AC/DC CONVERTER AND CHARGING APPARATUS

Abstract

An AC/DC converter and a charging apparatus. The AC/DC converter includes a circuit of at least one phase. In a circuit of each phase, a first end of an inductor is coupled to an alternating current power supply, and the second end of the inductor is coupled to a first end of a first winding and a first end of a second winding; the second end of the first winding is coupled to a winding connection end of a first switching unit, and the second end of the second winding is coupled to a winding connection end of a second switching unit; a bus connection end of the first switching unit is coupled to a bus of the AC/DC converter through at least two first rectifier units.

Description

TECHNICAL FIELD

The embodiments relate to the field of power supply technologies, an AC/DC converter, and a charging apparatus.

BACKGROUND

An Alternating Current/Direct Current (AC/DC) converter is a voltage converter that converts an input alternating current into an output direct current. An AC/DC converter shown in FIG. 1 is used as an example. After flowing through an inductor L₁₁, a current flows through a winding T₁₁ and a winding T₁₂ separately. When a switch tube Q₁₁ and a switch tube Q₁₂ are on, regardless of whether an alternating current power supply is in a positive half cycle or a negative half cycle, both the inductor L₁₁ and the winding T₁₁ form a closed loop with the switch tube Q₁₁ and the switch tube Q₁₂. A rectifier diode D₁₁ needs to withstand a voltage at both ends of a capacitor C₁₁, and a rectifier diode D₁₃ needs to withstand a voltage at both ends of a capacitor C₁₂. Similarly, when a switch tube Q₁₃ and a switch tube Q₁₄ are on, regardless of whether an alternating current power supply is in a positive half cycle or a negative half cycle, both the inductor L₁₁ and the winding T₁₂ form a closed loop with the switch tube Q₁₃ and the switch tube Q₁₄. A rectifier diode D₁₂ needs to withstand the voltage at both ends of the capacitor C₁₁, and a rectifier diode D₁₄ needs to withstand the voltage at both ends of the capacitor C₁₂. In other words, in an AC/DC converter in a current technology, a rectifier diode needs to withstand half of an output voltage of the AC/DC converter. In this case, the AC/DC converter in the current technology has a high requirement on a rated voltage of the rectifier diode. Especially in a high-voltage application scenario, for example, when an output voltage is 800 V, the rated voltage of the rectifier diode in the AC/DC converter needs to be greater than 400 V to ensure that the AC/DC converter can work normally. As a price and the rated voltage of the rectifier diode are positively correlated, the AC/DC converter has relatively high costs.

SUMMARY

The embodiments provide an AC/DC converter and a charging apparatus. An internal structure of a switching unit is improved, so that costs of the AC/DC converter can be reduced, and conversion efficiency can be improved.

According to a first aspect, an embodiment provides an AC/DC converter. The AC/DC converter is disposed between an alternating current power supply and power-consuming equipment. The AC/DC converter includes a circuit of at least one phase. A circuit of each phase includes an inductor, an autotransformer, a first switching unit, a second switching unit, at least two first rectifier units corresponding to the first switching unit, and at least two second rectifier units corresponding to the second switching unit. The autotransformer includes a first winding corresponding to the first switching unit and a second winding corresponding to the second switching unit. In an implementation, a first end of the inductor is coupled to the alternating current power supply, and the second end of the inductor is coupled to a first end of the first winding and a first end of the second winding. The second end of the first winding is coupled to a winding connection end of the first switching unit, and the second end of the second winding is coupled to a winding connection end of the second switching unit. A bus connection end of the first switching unit is coupled to a bus of the AC/DC converter through the at least two first rectifier units, a bus connection end of the second switching unit is coupled to the bus of the AC/DC converter through the at least two second rectifier units, and the bus of the AC/DC converter is coupled to the power-consuming equipment. At least two groups of switching circuits are included between the winding connection end of any one of the switching units and a ground cable connection end of the switching unit, where each group of switching circuits includes a diode and a controllable switch connected in series to the diode, and the controllable switch is configured to control a connection or disconnection between the winding connection end and the ground cable connection end of the switching unit including the controllable switch. Compared with a current technology in which two switch tubes are connected in series for switching between charging/discharging states of an inductor and implement AC/DC conversion, this embodiment improves an internal structure of a switching unit. In this embodiment, the switching unit uses the at least two groups of switching circuits. Each group of switching circuits includes the diode and the controllable switch connected in series to the diode. An output voltage of the AC/DC converter may be withstood by the diode in the switching circuit and a rectifier diode or withstood by the controllable switch in the switching circuit and a rectifier diode. Therefore, in this embodiment, an internal structure of a switching unit may be improved to reduce a voltage difference withstood by the rectifier units, so that when an output voltage for the power-consuming equipment provided by the AC/DC converter in this embodiment is the same as that provided by an AC/DC converter provided in the current technology, the AC/DC converter in this embodiment may select a rectifier component with a smaller rated voltage, and therefore, there are lower costs. In addition, a value of a rated voltage of a rectifier component is positively correlated with a forward voltage drop of the rectifier component. A larger rated voltage of the rectifier component indicates a larger loss caused by the rectifier component. Therefore, in this embodiment, an internal structure of a switching unit is improved, so that a rectifier component with a smaller rated voltage can be selected. Not only costs can be reduced, a loss of the AC/DC converter can be further reduced, and conversion efficiency can be improved.

With reference to the first aspect, in a first possible implementation, the AC/DC converter in this embodiment further includes a controller. The controller may send a first pulse control signal to a first controllable switch included in each group of switching circuits in the first switching unit, where the first pulse control signal is used to control on or off of the first controllable switch. The controller may further send a second pulse control signal to a second controllable switch included in each group of switching circuits in the second switching unit, where the second pulse control signal is used to control on or off of the second controllable switch. The first pulse control signal and the second pulse control signal have a same frequency, with a phase difference of 180º. In this case, there is a minimum current ripple of the AC/DC converter.

With reference to the first aspect or the first possible implementation of the first aspect, in a second possible implementation, the at least two groups of switching circuits included in any one of the switching units include a first group of switching circuits and a second group of switching circuits. The first group of switching circuits includes a first diode and a first switch tube, the second group of switching circuits includes a second diode and a second switch tube, and the bus of the AC/DC converter includes a positive bus and a negative bus. In an implementation, both an anode of the first diode and a cathode of the second diode are coupled to the second end of the winding corresponding to the switching unit, both a cathode of the first diode and a first end of the first switch tube are coupled to the positive bus of the AC/DC converter by using one rectifier unit in the two rectifier units corresponding to the switching unit, both an anode of the second diode and a second end of the second switch tube are coupled to the negative bus of the AC/DC converter by using the other rectifier unit in the two rectifier units corresponding to the switching unit, and both a second end of the first switch tube and a first end of the second switch tube are coupled to a ground cable of the AC/DC converter. In this embodiment, the second end of the winding is connected to a connection midpoint between the two diodes, and the ground cable of the AC/DC converter is connected to a connection midpoint between the two switch tubes. In this circuit connection mode of the switching unit, a switching speed of the switch tubes may be relatively slow, to avoid frequent switching of the switch tubes, thereby improving a service life of the AC/DC converter.

With reference to the first aspect or the first possible implementation of the first aspect, in a third possible implementation, the at least two groups of switching circuits included in any one of the switching units include a first group of switching circuits and a second group of switching circuits. The first group of switching circuits includes a third diode and a third switch tube, the second group of switching circuits includes a fourth diode and a fourth switch tube, and the bus of the AC/DC converter includes a positive bus and a negative bus. In an implementation, both a cathode of the third diode and a first end of the third switch tube are coupled to the positive bus of the AC/DC converter by using one rectifier unit in the two rectifier units corresponding to the switching unit, both a second end of the third switch tube and a first end of the fourth switch tube are coupled to the second end of the winding corresponding to the switching unit, both an anode of the fourth diode and a second end of the fourth switch tube are coupled to the negative bus of the AC/DC converter by using the other rectifier unit in the two rectifier units corresponding to the switching unit, and both an anode of the third diode and a cathode of the fourth diode are coupled to a ground cable of the AC/DC converter. In this embodiment, the second end of the winding is connected to a connection midpoint between the two switch tubes, and the ground cable of the AC/DC converter is connected to a connection midpoint between the two diodes. In this circuit connection mode of the switching unit, a diode conduction speed is relatively high, so that a conversion speed of the AC/DC converter can be improved.

With reference to the second possible implementation of the first aspect or the third possible implementation of the first aspect, in a fourth possible implementation, the AC/DC converter provided in this embodiment further includes a first capacitor and a second capacitor. The first capacitor is coupled between the positive bus of the AC/DC converter and the ground cable of the AC/DC converter, and the second capacitor is coupled between the negative bus of the AC/DC converter and the ground cable of the AC/DC converter.

With reference to the first aspect or any one of the foregoing possible implementations of the first aspect, in a fifth possible implementation, the AC/DC converter includes a three-phase circuit, and a sum of phasors of currents in the three-phase circuit is zero.

With reference to any one of the foregoing possible implementations of the first aspect, in a sixth possible implementation, the controller may further control duty ratios of the first pulse control signal and the second pulse control signal to be less than 0.5 when a voltage of the alternating current power supply is less than a half of an output voltage of the AC/DC converter; or the controller may further control duty ratios of both the first pulse control signal and the second pulse control signal to be greater than 0.5 when a voltage of the alternating current power supply is greater than a half of an output voltage of the AC/DC converter.

With reference to the first aspect or any one of the foregoing possible implementations of the first aspect, in a seventh possible implementation, winding turns of the first winding and the second winding are equal.

According to a second aspect, an embodiment provides a charging apparatus. The charging apparatus may include the AC/DC converter according to the first aspect or any one of possible implementations of the first aspect and an electric meter, and the electric meter is connected in series between an alternating current power supply and the AC/DC converter. The AC/DC converter may convert an alternating current output from the alternating current power supply into a first direct current and transmit the first direct current to power-consuming equipment, and the electric meter may measure electric energy supplied by the alternating current power supply to the power-consuming equipment.

With reference to the second aspect, in a first possible implementation, the charging apparatus further includes a DC/DC converter. The DC/DC converter is disposed between the AC/DC converter and the power-consuming equipment. The AC/DC converter transmits, via the DC/DC converter to the power-consuming equipment, the first direct current obtained by converting the alternating current output from the alternating current power supply. The DC/DC converter may convert the first direct current to obtain a second direct current and supply the second direct current to the power-consuming equipment.

It should be understood that, for implementation and beneficial effects of the foregoing aspects, a reference may be provided for each other.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram of an AC/DC converter in a current technology;

FIG. 2 is a block diagram of a structure of a charging apparatus according to an embodiment;

FIG. 3 is a block diagram of a structure of an AC/DC converter according to an embodiment;

FIG. 4A and FIG. 4B are circuit diagrams of a switching unit according to an embodiment;

FIG. 5 is a sequence diagram of a pulse control signal according to an embodiment;

FIG. 6A to FIG. 6F are equivalent circuit diagrams of an AC/DC converter according to an embodiment;

FIG. 7A to FIG. 7F are other equivalent circuit diagrams of an AC/DC converter according to an embodiment;

FIG. 8 is another sequence diagram of a pulse control signal according to an embodiment;

FIG. 9A and FIG. 9B are still another equivalent circuit diagram of an AC/DC converter according to an embodiment;

FIG. 10A and FIG. 10B are yet another equivalent circuit diagram of an AC/DC converter according to an embodiment;

FIG. 11 is a three-phase circuit diagram of an AC/DC converter according to an embodiment; and

FIG. 12 is a schematic diagram of a waveform of an alternating current power grid according to an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

The embodiments are described below with reference to the accompanying drawings. The described embodiments are some of rather than all of the embodiments. Based on the embodiments, all other embodiments obtained by a person of ordinary skill in the art without creative efforts shall fall within the scope of the embodiments.

The embodiments are further described below in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram of a structure of a charging apparatus according to an embodiment. As shown in FIG. 2, a charging apparatus 21 is disposed between an alternating current power supply and power-consuming equipment. The charging apparatus 21 may include an electric meter 211 and an AC/DC converter 212. An output end of the alternating current power supply is coupled to a first end of the electric meter 211, the second end of the electric meter 211 is coupled to a first end of the AC/DC converter 212, and the second end of the AC/DC converter 212 is coupled to the power-consuming equipment.

It should be noted that “coupling” indicates a direct or indirect connection. For example, coupling between A and B may be a direct connection between A and B, or may be an indirect connection between A and B via one or more other electrical components. For example, A is directly connected to C, and C is directly connected to B, so that A is connected to B via C.

The AC/DC converter 212 may convert an alternating current output from the alternating current power supply into a first direct current and transmit the first direct current to the power-consuming equipment. The electric meter 211 is connected in series between the alternating current power supply and the AC/DC converter 212 and may measure electric energy supplied by the alternating current power supply to the power-consuming equipment. Optionally, the AC/DC converter 212 may further include a communications module (not shown in the figure), and the communications module may transmit electric energy data measured by the electric meter 211 to the power-consuming equipment. Alternatively, the AC/DC converter 212 may further include a display module (not shown in the figure), and the display module may display electric energy data measured by the electric meter 211.

For example, the AC/DC converter 212 may perform rectification by using a circuit structure, for example, a half-wave rectifier, a full-wave rectifier, or an active inverter.

For example, the power-consuming equipment may be a terminal, an inverter, an electric vehicle, or the like. For example, the alternating current power supply in the AC/DC converter 212 may be from an alternating current power grid. In this case, the charging apparatus in this embodiment may be implemented as a charging pile, to output a direct current to an electric vehicle.

In some implementations, the AC/DC converter 212 may further include a DC/DC converter (not shown in the figure). The DC/DC converter is disposed between the AC/DC converter 212 and the power-consuming equipment, that is, the second end of the AC/DC converter 212 is coupled to the power-consuming equipment via the DC/DC converter. In an implementation, the AC/DC converter 212 may convert the alternating current output from the alternating current power supply into the first direct current, and the DC/DC converter may convert the first direct current into a second direct current and transmit the second direct current to the power-consuming equipment.

For example, the DC/DC converter may be, for example, a BUCK converter. The BUCK converter may step down a voltage of the first direct current to obtain the second direct current, that is, the second direct current may be less than the first direct current. The DC/DC converter may be, for example, a BOOST converter. The BOOST converter may step up a voltage of the first direct current to obtain the second direct current, that is, the second direct current may be greater than the first direct current. Optionally, the DC/DC converter may be, for example, a BUCK-BOOST converter. The BUCK-BOOST converter may step up or step down a voltage of the first direct current to obtain the second direct current, that is, the second direct current may be greater than or less than the first direct current. Optionally, the AC/DC converter 212 and the DC/DC converter may be built in a charging pile in a charging station in a form of a printed circuit board (PCB).

A structure of the AC/DC converter provided in this embodiment is described below with reference to the accompanying drawings.

FIG. 3 is a block diagram of a structure of an AC/DC converter according to an embodiment. As shown in FIG. 3, the AC/DC converter is disposed between an alternating current power supply and power-consuming equipment. The AC/DC converter includes a circuit of at least one phase. It can be understood that a quantity of circuit phases included in the AC/DC converter determines a scenario to which the AC/DC converter is applicable. For example, if the AC/DC converter is applicable to an application scenario in which the alternating current power supply is an alternating current power grid, the AC/DC converter includes a three-phase circuit. For another example, if the AC/DC converter is applicable to a scenario in which the alternating current power supply is a single-phase alternating current, the AC/DC converter includes a single-phase circuit.

In FIG. 3, an example in which the AC/DC converter includes a single-phase circuit is used. The single-phase circuit includes an inductor L₃₁, an autotransformer 310, a first switching unit 311, a second switching unit 312, at least two first rectifier units (for example, a first rectifier unit 313a and a first rectifier unit 313b) corresponding to the first switching unit 311, and at least two second rectifier units (for example, a second rectifier unit 314a and a second rectifier unit 314b) corresponding to the second switching unit 312. The autotransformer 310 includes a first winding T₃₁ corresponding to the first switching unit 311 and a second winding T₃₂ corresponding to the second switching unit 312.

Optionally, winding turns of the first winding T₃₁ and the second winding T₃₂ are equal. In this case, the autotransformer 310 divides and shunts a current of the inductor L₃₁, so that an output current of the AC/DC converter can be increased.

In an implementation, a first end of the inductor L₃₁ is coupled to the alternating current power supply, the second end of the inductor L₃₁ is coupled to a first end of the first winding T₃₁ and a first end of the second winding T₃₂, the second end of the first winding T₃₁ is coupled to a winding connection end {circle around (1)} of the first switching unit 311, and the second end of the second winding T₃₂ is coupled to a winding connection end {circle around (1)} of the second switching unit 312.

A positive bus connection end {circle around (2)} of the first switching unit 311 is coupled to a positive bus DC1+ of the AC/DC converter via the first rectifier unit 313a, and a negative bus connection end {circle around (3)} of the first switching unit 311 is coupled to a negative bus DC1− of the AC/DC converter via the first rectifier unit 313b.

A positive bus connection end {circle around (2)} of the second switching unit 312 is coupled to a positive bus DC1+ of the AC/DC converter via the second rectifier unit 314a, and a negative bus connection end {circle around (3)} of the second switching unit 312 is coupled to a negative bus DC1− of the AC/DC converter via the second rectifier unit 314b.

The power-consuming equipment is coupled between the positive bus DC1+ and the negative bus DC1− of the AC/DC converter, and an output voltage of the AC/DC converter is a voltage difference between the positive bus DC1+ of the AC/DC converter and the negative bus DC1− of the AC/DC converter.

An internal structure of each of the switching units may be as follows: at least two groups of switching circuits are included between the winding connection end 1 of any one of the switching units and a ground cable connection end 4 of the switching unit, where each group of switching circuits includes a diode and a controllable switch connected in series to the diode. The controllable switch may control a connection or disconnection between the winding connection end {circle around (1)} and the ground cable connection end {circle around (4)} of the switching unit including the controllable switch. For example, the first group of switching circuits in the first switching unit 311 includes a diode D₃₁ and a switch tube Q₃₁ connected in series to the diode D₃₁. If the switch tube Q₃₁ is off, the winding connection end 1 of the first switching unit 311 and the ground cable connection end {circle around (4)} of the first switching unit 311 is disconnected; or if the switch tube Q₃₁ is on, a connection between the winding connection end {circle around (1)} of the first switching unit 311 and the ground cable connection end {circle around (4)} of the first switching unit 311 is on when the alternating current power supply is in a positive half cycle. The second group of switching circuits in the first switching unit 311 includes a diode D₃₂ and a switch tube Q₃₂ connected in series to the diode D₃₂. If the switch tube Q₃₂ is off, the winding connection end 1 of the first switching unit 311 and the ground cable connection end {circle around (4)} of the first switching unit 311 is disconnected; or if the switch tube Q₃₂ is on, a connection between the winding connection end {circle around (1)} of the first switching unit 311 and the ground cable connection end {circle around (4)} of the first switching unit 311 is on when the alternating current power supply is in a negative half cycle.

It can be understood that, in FIG. 3, an example in which the controllable switch is implemented as a metal-oxide semiconductor field-effect transistor (MOSFET) is used. It can be understood that the controllable switch may alternatively be implemented as a relay, a contactor, an insulated gate bipolar transistor (IGBT), or the like.

In some implementations, the AC/DC converter further includes a first capacitor C₃₁ and a second capacitor C₃₂. The first capacitor C₃₁ is coupled between the positive bus DC1+ of the AC/DC converter and a ground cable (GND) of the AC/DC converter, and the second capacitor C₃₂ is coupled between the negative bus DC1− of the AC/DC converter and the GND of the AC/DC converter. It can be understood that the first capacitor C₃₁ is a filter capacitor of the positive bus DC1+ of the AC/DC converter, and the second capacitor C₃₂ is a filter capacitor of the negative bus DC1− of the AC/DC converter.

In some implementations, the AC/DC converter may further include a controller (not shown in the figure). The controller may send a first pulse control signal to a first controllable switch (for example, the switch tube Q₃₁ and the switch tube Q₃₂) included in each group of switching circuits in the first switching unit 311. The first pulse control signal may control on or off of the switch tube Q₃₁ and the switch tube Q₃₂. The controller may further send a second pulse control signal to a second controllable switch (that is, the two switch tubes in the second switching unit 312) included in each group of switching circuits in the second switching unit 312. The second pulse control signal may control on or off of the two switch tubes in the second switching unit 312. The first pulse control signal and the second pulse control signal have a same frequency. Optionally, a phase difference between the first pulse control signal and the second pulse control signal may be 180º. In this case, there is a minimum current ripple of the AC/DC converter.

Further, in some implementations, a voltage of the alternating current power supply is represented by V_in, and the output voltage of the AC/DC converter is represented by V_o. When V_in<V_o/2, the controller controls duty ratios of the first pulse control signal and the second pulse control signal to be less than 0.5. Alternatively, when V_in>V_o/2, the controller controls duty ratios of the first pulse control signal and the second pulse control signal to be greater than 0.5. A duty ratio of the first pulse control signal is the same as a duty ratio of the second pulse control signal. The controller may keep the output voltage, of the AC/DC converter, V_o=2V_in by adjusting the duty ratio of the pulse control signal.

Compared with a current technology in which two switch tubes are connected in series for switching between charging/discharging states of an inductor and implement AC/DC conversion, this embodiment improves an internal structure of a switching unit. In this embodiment, the switching unit uses the at least two groups of switching circuits. Each group of switching circuits includes the diode and the controllable switch connected in series to the diode. An output voltage of the AC/DC converter may be withstood by the diode in the switching circuit and a rectifier diode or withstood by the controllable switch in the switching circuit and a rectifier diode. Therefore, in this embodiment, an internal structure of a switching unit may be improved to reduce a voltage difference withstood by the rectifier units, so that when an output voltage for the power-consuming equipment provided by the AC/DC converter in this embodiment is the same as that provided by an AC/DC converter provided in the current technology, the AC/DC converter in this embodiment may select a rectifier component with a smaller rated voltage, and therefore, there are lower costs. In addition, a value of a rated voltage of a rectifier component is positively correlated with a forward voltage drop of the rectifier component. A larger rated voltage of the rectifier component indicates a larger loss caused by the rectifier component. Therefore, in this embodiment, an internal structure of a switching unit is improved, so that a rectifier component with a smaller rated voltage can be selected. Not only costs can be reduced, a loss of the AC/DC converter can be further reduced, and conversion efficiency can be improved.

In some implementations, a circuit diagram of the first switching unit shown in FIG. 4A is used as an example. Both an anode of the diode D₃₁ and a cathode of the diode D₃₂ are coupled to the second end of the first winding T₃₁ corresponding to the first switching unit. That is, a connection point between the anode of the diode D₃₁ and the cathode of the diode D₃₂ is the winding connection end 1 of the first switching unit 311. Both a cathode of the diode D₃₁ and a first end (that is, a drain) of the switch tube Q₃₁ are coupled to the positive bus DC1+ of the AC/DC converter by using one rectifier unit (for example, the first rectifier unit 313a) in the two rectifier units corresponding to the first switching unit. That is, a connection point between the cathode of the diode D₃₁ and the drain of the switch tube Q₃₁ is the positive bus connection end 2 of the first switching unit 311. Both an anode of the diode D₃₂ and a second end (that is, a source) of the switch tube Q₃₁ are coupled to the negative bus DC1− of the AC/DC converter by using the other rectifier unit (for example, the first rectifier unit 313b) in the two rectifier units corresponding to the first switching unit. That is, a connection point between the anode of the diode D₃₂ and the source of the switch tube Q₃₁ is the negative bus connection end 3 of the first switching unit 311. Both the second end (that is, the source) of the switch tube Q₃₁ and a first end (that is, a drain) of the switch tube Q₃₂ are coupled to the ground cable of the AC/DC converter. That is, a connection point between the source of the switch tube Q₃₁ and the drain of the switch tube Q₃₂ is the ground cable connection end 4 of the first switching unit 311.

Similarly, for a circuit diagram of the second switching unit 312, refer to the descriptions of the first switching unit. Details are not described herein again.

In this embodiment, the second end of the winding is connected to a connection midpoint between the two diodes, and the ground cable of the AC/DC converter is connected to a connection midpoint between the two switch tubes. In this circuit connection mode of the switching unit, a line-frequency diode with a relatively low switching speed may be used, and a switching speed of the switch tubes may also be relatively low, to avoid frequent switching of the switch tubes, thereby improving a service life of the AC/DC converter.

Optionally, in some implementations, an example in which a circuit diagram of the second switching unit shown in FIG. 4B is used. Both the second end (that is, the source) of the switch tube Q₃₁ and the first end (that is, the drain) of the switch tube Q₃₂ are coupled to the second end of the first winding T₃₁ corresponding to the first switching unit. That is, a connection point between the source of the switch tube Q₃₁ and the drain of the switch tube Q₃₂ is the winding connection end {circle around (1)} of the first switching unit 311. Both the first end (that is, the drain) of the switch tube Q₃₁ and the cathode of the diode D₃₁ are coupled to the positive bus DC1+ of the AC/DC converter by using one rectifier unit (for example, the first rectifier unit 313a) in the two rectifier units corresponding to the first switching unit. That is, a connection point between the drain of the switch tube Q₃₁ and the cathode of the diode D₃₁ is the positive bus connection end {circle around (2)} of the first switching unit 311. Both the second end (that is, the source) of the switch tube Q₃₂ and the anode of the diode D₃₂ are coupled to the negative bus DC1− of the AC/DC converter by using the other rectifier unit (for example, the first rectifier unit 313b) in the two rectifier units corresponding to the first switching unit. That is, a connection point between the anode of the diode D₃₂ and the source of the switch tube Q₃₁ is the negative bus connection end {circle around (3)} of the first switching unit 311. Both the anode of the diode D₃₁ and the cathode of the diode D₃₂ are coupled to the ground cable of the AC/DC converter. That is, a connection point between the anode of the diode D₃₁ and the cathode of the diode D₃₂ is the ground cable connection end {circle around (4)} of the first switching unit 311.

Similarly, for a circuit diagram of the second switching unit 312, refer to the descriptions of the first switching unit. Details are not described herein again.

In this embodiment, unlike the switching unit shown in FIG. 4A, the second end of the winding is connected to a connection midpoint between the two switch tubes, and the ground cable of the AC/DC converter is connected to a connection midpoint between the two diodes. In this circuit connection mode of the switching unit, a diode conduction speed is relatively high, so that a conversion speed of the AC/DC converter can be improved.

With reference to FIG. 5 to FIG. 7F, an operating principle of the AC/DC converter provided in embodiments is described below.

FIG. 5 is a sequence diagram of a pulse control signal according to an embodiment. As shown in FIG. 5, the first pulse control signal and the second pulse control signal have a same frequency, with a phase difference of 180º. In addition, duty ratios of the first pulse control signal and the second pulse control signal are less than 0.5.

In some implementations, when a connection relationship in the internal structure of the switching unit is shown in FIG. 4A, with reference to the sequence diagram of the pulse control signal shown in FIG. 5, it is assumed that the alternating current output from the alternating current power supply is in a positive half cycle in a time period from t₅₀ to t₅₃, and the alternating current output from the alternating current power supply is in a negative half cycle in a time period from t₅₄ to t₅₇. In this case, the AC/DC converter provided in embodiments may obtain, at different moments, equivalent circuit diagrams as shown in FIG. 6A to FIG. 6F.

It should be first noted that in embodiments, an example in which the rectifier unit is implemented as a rectifier diode is used. It can be understood that the rectifier unit may be another semiconductor device, for example, a triode or an MOSFET.

In a time period from t₅₀ to t₅₁, the first pulse control signal is on a high level, and the switch tube Q₃₁ and the switch tube Q₃₂ are on, while the second pulse control signal is on a low level, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 6A. The alternating current output from the alternating current power supply flows through the inductor L₃₁ and then flows through the winding T₃₁ and the winding T₃₂ separately. A current on the winding T₃₁ flows through the diode D₃₁ and the switch tube Q₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is charging; and a current on the winding T₃₂ flows through the diode D₃₃, a rectifier diode D2, and the first capacitor C₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging. A voltage on the positive bus DC1+ of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D2.

In a time period from t₅₁ to t₅₂, both the first pulse control signal and the second pulse control signal are on a low level, the switch tube Q₃₁ and the switch tube Q₃₂ are off, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 6B. The alternating current output from the alternating current power supply flows through the inductor L₃₁ and then flows through the winding T₃₁ and the winding T₃₂ separately. The current on the winding T₃₁ flows through the diode D₃₁, a rectifier diode D1, and the first capacitor C₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is charging; and the current on the winding T₃₂ flows through the diode D₃₃, the rectifier diode D2, and the first capacitor C₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging. The voltage on the positive bus DC1+ of the AC/DC converter is a sum of direct currents obtained by discharging of the inductor L₃₁ through the rectifier diode D1 and the rectifier diode D2.

In a time period from t₅₂ to t₅₃, the first pulse control signal is on a low level, and the switch tube Q₃₁ and the switch tube Q₃₂ are off, while the second pulse control signal is on a high level, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 6C. The alternating current output from the alternating current power supply flows through the inductor L₃₁ and then flows through the winding T₃₁ and the winding T₃₂ separately. The current on the winding T₃₁ flows through the diode D₃₁, the rectifier diode D1, and the first capacitor C₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging; and the current on the winding T₃₂ flows through the diode D₃₃ and the switch tube Q₃₃ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging. The voltage on the positive bus DC1+ of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D1.

In a time period from t₅₄ to t₅₅, because the alternating current is in the negative half cycle, even if a pulse control signal in the time period from t₅₄ to t₅₅ is the same as the pulse control signal in the time period from t₅₀ to t₅₁ (that is, the first pulse control signal is on a high level, and the second pulse control signal is on a low level), there is a different equivalent circuit diagram of the AC/DC converter. In this case, the switch tube Q₃₁ and the switch tube Q₃₂ are on, the switch tube Q₃₃ and the switch tube Q₃₄ are off, and an equivalent circuit diagram of the AC/DC converter is shown in FIG. 6D. The current on the winding T₃₁ flows through the switch tube Q₃₂ and a diode D₃₂ to the GND of the AC/DC converter, and the inductor L₃₁ is charging; and the current on the winding T₃₂ flows through the second capacitor C₃₂, a rectifier diode D4, and a diode D₃₄ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging. The currents on the winding T₃₁ and on the winding T₃₂ converge to the inductor L₃₁. The voltage on the negative bus DC1− of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D4.

Similarly, in a time period from t₅₅ to t₅₆, both the first pulse control signal and the second pulse control signal are on a low level, the switch tube Q₃₁ and the switch tube Q₃₂ are off, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 6E. The current on the winding T₃₁ flows through the second capacitor C₃₂, a rectifier diode D3, and the diode D₃₂ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging; and the current on the winding T₃₂ flows through the second capacitor C₃₂, the rectifier diode D4, and the diode D₃₄ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging. The currents on the winding T₃₁ and on the winding T₃₂ converge to the inductor L₃₁. The voltage on the negative bus DC1− of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D3 and the rectifier diode D4.

In a time period from t₅₆ to t₅₇, the first pulse control signal is on a low level, and the switch tube Q₃₁ and the switch tube Q₃₂ are off, while the second pulse control signal is on a high level, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 6F. The current on the winding T₃₁ flows through the second capacitor C₃₂, a rectifier diode D3, and the diode D₃₂ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging; and the current on the winding T₃₂ flows through the switch tube Q₃₄ and the diode D₃₄ to the GND of the AC/DC converter, and the inductor L₃₁ is charging. The currents on the winding T₃₁ and on the winding T₃₂ converge to the inductor L₃₁. The voltage on the negative bus DC1− of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D3.

Optionally, in some implementations, when a connection relationship in the internal structure of the switching unit is shown in FIG. 4B, the time sequence diagram of the pulse control signal shown in FIG. 5 is still applicable. However, a current loop formed with the inductor L₃₁ varies at various moments.

For example, in the time period from t₅₀ to t₅₁, the switch tube Q₃₁ and the switch tube Q₃₂ are on, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 7A. The alternating current output from the alternating current power supply flows through the inductor L₃₁ and then flows through the winding T₃₁ and the winding T₃₂ separately. Different from the case in FIG. 6A, the current on the winding T₃₁ flows through the switch tube Q₃₂ and the diode D₃₂ to the GND of the AC/DC converter, and the inductor L₃₁ is charging; and the current on the winding T₃₂ flows through a parasitic diode of the switch tube Q₃₃, the rectifier diode D2, and the first capacitor C₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging. The voltage on the positive bus DC1+ of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D2.

In the time period from t₅₁ to t₅₂, the switch tube Q₃₁ and the switch tube Q₃₂ are off, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 7B. The alternating current output from the alternating current power supply flows through the inductor L₃₁ and then flows through the winding T₃₁ and the winding T₃₂ separately. Different from the case in FIG. 6B, the current on the winding T₃₁ flows through a parasitic diode of the switch tube Q₃₁, the rectifier diode D1, and the first capacitor C₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging; and the current on the winding T₃₂ flows through the parasitic diode of the switch tube Q₃₃, the rectifier diode D2, and the first capacitor C₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging. The voltage on the positive bus DC1+ of the AC/DC converter is a sum of direct currents obtained by discharging of the inductor L₃₁ through the rectifier diode D1 and the rectifier diode D2.

In the time period from t₅₂ to t₅₃, the switch tube Q₃₁ and the switch tube Q₃₂ are off, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 7C. The alternating current output from the alternating current power supply flows through the inductor L₃₁ and then flows through the winding T₃₁ and the winding T₃₂ separately. Different from the case in FIG. 6C, the current on the winding T₃₁ flows through the parasitic diode of the switch tube Q₃₁, the rectifier diode D1, and the first capacitor C₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging; and the current on the winding T₃₂ flows through the switch tube Q₃₄ and the diode D₃₄ to the GND of the AC/DC converter, and the inductor L₃₁ is charging. The voltage on the positive bus DC1+ of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D1.

In the time period from t₅₄ to t₅₅, the alternating current is in the negative half cycle, the switch tube Q₃₁ and the switch tube Q₃₂ are on, the switch tube Q₃₃ and the switch tube Q₃₄ are off, and an equivalent circuit diagram of the AC/DC converter is shown in FIG. 7D. Different from the case in FIG. 6D, the current on the winding T₃₁ flows through the diode D₃₁ and the switch tube Q₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is charging; and the current on the winding T₃₂ flows through the second capacitor C₃₂, the rectifier diode D4, and a parasitic diode of the switch tube Q₃₄ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging. The currents on the winding T₃₁ and on the winding T₃₂ converge to the inductor L₃₁. The voltage on the negative bus DC1− of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D4.

In the time period from t₅₅ to t₅₆, the alternating current is in the negative half cycle, the switch tube Q₃₁ and the switch tube Q₃₂ are off, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 7E. Different from the case in FIG. 6E, the current on the winding T₃₁ flows through the second capacitor C₃₂, the rectifier diode D3, and a parasitic diode of the switch tube Q₃₂ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging; and the current on the winding T₃₂ flows through the second capacitor C₃₂, the rectifier diode D4, and the parasitic diode of the switch tube Q₃₄ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging. The currents on the winding T₃₁ and on the winding T₃₂ converge to the inductor L₃₁. The voltage on the negative bus DC1− of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D3 and the rectifier diode D4.

In the time period from t₅₆ to t₅₇, the alternating current is in the negative half cycle, the switch tube Q₃₁ and the switch tube Q₃₂ are off, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 7F. Different from the case in FIG. 6F, the current on the winding T₃₁ flows through the second capacitor C₃₂, the rectifier diode D3, and a parasitic diode of the switch tube Q₃₂ to the GND of the AC/DC converter, and the inductor L₃₁ is discharging; and the current on the winding T₃₂ flows through the diode D₃₃ and the switch tube Q₃₃ to the GND of the AC/DC converter, and the inductor L₃₁ is charging. The currents on the winding T₃₁ and on the winding T₃₂ converge to the inductor L₃₁. The voltage on the negative bus DC1− of the AC/DC converter is a direct current obtained by discharging of the inductor L₃₁ through the rectifier diode D3.

In some implementations, FIG. 8 is another sequence diagram of a pulse control signal according to an embodiment. As shown in FIG. 8, the duty ratios of the first pulse control signal and the second pulse control signal are greater than 0.5. Compared with the time sequence diagram of the pulse control signal shown in FIG. 5, it can be understood that an overlapped part in the time sequence diagram of the pulse control signal in FIG. 5 shows that both the first pulse control signal and the second pulse control signal are on a low level, while an overlapped part in the time sequence diagram of the pulse control signal in FIG. 8 shows that both the first pulse control signal and the second pulse control signal are on a high level. Therefore, with control of the sequence diagram of the pulse control signal shown in FIG. 5, switch tubes (for example, the switch tubes Q₃₁, Q₃₂, Q₃₃, and Q₃₄) of various switching units may all be in an off state, and with control of the sequence diagram of the pulse control signal shown in FIG. 8, the switch tubes Q₃₁, Q₃₂, Q₃₃, and Q₃₄ may all be in an on state.

In some implementations, when a connection relationship in the internal structure of the switching unit is shown in FIG. 4A, with reference to the sequence diagram of the pulse control signal shown in FIG. 8, it is assumed that the alternating current output from the alternating current power supply is in a positive half cycle in a time period from tgo to t₈₃, and the alternating current output from the alternating current power supply is in a negative half cycle in a time period from t₈₄ to t₈₇.

In a time period from t₈₀ to t₈₁, the first pulse control signal is on a low level, and the switch tube Q₃₁ and the switch tube Q₃₂ are off, while the second pulse control signal is on a high level, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 6C. For an implementation, refer to the descriptions in FIG. 6C. Details are not described herein again.

In a time period from t₈₁ to t₈₂, both the first pulse control signal and the second pulse control signal are on a high level, the switch tube Q₃₁ and the switch tube Q₃₂ are on, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 9A. The alternating current output from the alternating current power supply flows through the inductor L₃₁ and then flows through the winding T₃₁ and the winding T₃₂ separately. The current on the winding T₃₁ flows through the diode D₃₁ and the switch tube Q₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is charging; and the current on the winding T₃₂ flows through the diode D₃₃ and the switch tube Q₃₃ to the GND of the AC/DC converter, and the inductor L₃₁ is charging. A voltage difference between the positive bus DC+ and the negative bus DC− of the AC/DC converter is a voltage output within the time period from tso to t₈₁.

In a time period from t₈₂ to t₈₃, the first pulse control signal is on a high level, and the switch tube Q₃₁ and the switch tube Q₃₂ are on, while the second pulse control signal is on a low level, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 6A. For an implementation, refer to the descriptions in FIG. 6A. Details are not described herein again.

In a time period from t₈₄ to t₈₅, the alternating current is in the negative half cycle, the first pulse control signal is on a low level, and the switch tube Q₃₁ and the switch tube Q₃₂ are off, while the second pulse control signal is on a high level, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 6F. For an implementation, refer to the descriptions in FIG. 6F. Details are not described herein again.

In a time period from t₈₅ to t₈₆, the alternating current is in the negative half cycle, both the first pulse control signal and the second pulse control signal are on a high level, the switch tube Q₃₁ and the switch tube Q₃₂ are on, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 9B. The current on the winding T₃₁ flows through the switch tube Q₃₂ and the diode D₃₂ to the GND of the AC/DC converter, and the inductor L₃₁ is charging; and the current on the winding T₃₂ flows through the switch tube Q₃₄ and the diode D₃₄ to the GND of the AC/DC converter, and the inductor L₃₁ is charging. The voltage difference between the positive bus DC+ and the negative bus DC− of the AC/DC converter is a voltage output within the time period from t₈₄ to t₈₅.

In a time period from t₈₆ to t₈₇, the alternating current is in the negative half cycle, the first pulse control signal is on a high level, the second pulse control signal is on a low level, the switch tube Q₃₁ and the switch tube Q₃₂ are on, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. An equivalent circuit diagram of the AC/DC converter is shown in FIG. 6D, for an implementation, refer to the descriptions in FIG. 6D. Details are not described herein again.

Optionally, in some implementations, when a connection relationship in the internal structure of the switching unit is shown in FIG. 4B, the time sequence diagram of the pulse control signal shown in FIG. 8 is still applicable. However, a current loop formed with the inductor L₃₁ varies at various moments.

For example, in the time period from tgo to t₈₁, the switch tube Q₃₁ and the switch tube Q₃₂ are off, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 7C. For an implementation, refer to the descriptions in FIG. 7C. Details are not described herein again.

In the time period from t₈₁ to t₈₂, the switch tube Q₃₁ and the switch tube Q₃₂ are on, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 10A. The current on the winding T₃₁ flows through the switch tube Q₃₂ and the diode D₃₂ to the GND of the AC/DC converter, and the inductor L₃₁ is charging; and the current on the winding T₃₂ flows through the switch tube Q₃₄ and the diode D₃₄ to the GND of the AC/DC converter, and the inductor L₃₁ is charging. The voltage difference between the positive bus DC+ and the negative bus DC− of the AC/DC converter is a voltage output within the time period from t₈₀ to t₈₁.

In the time period from t₈₂ to t₈₃, the switch tube Q₃₁ and the switch tube Q₃₂ are on, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 7A. For an implementation, refer to the descriptions in FIG. 7A. Details are not described herein again.

In the time period from t₈₄ to t₈₅, the alternating current is in the negative half cycle, the switch tube Q₃₁ and the switch tube Q₃₂ are off, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 7F. For an implementation, refer to the descriptions in FIG. 7F. Details are not described herein again.

In the time period from t₈₅ to t₈₆, the alternating current is in the negative half cycle, the switch tube Q₃₁ and the switch tube Q₃₂ are on, and the switch tube Q₃₃ and the switch tube Q₃₄ are on. In this case, an equivalent circuit diagram of the AC/DC converter is shown in FIG. 10B. The current on the winding T₃₁ flows through the diode D₃₁ and the switch tube Q₃₁ to the GND of the AC/DC converter, and the inductor L₃₁ is charging; and the current on the winding T₃₂ flows through the diode D₃₃ and the switch tube Q₃₃ to the GND of the AC/DC converter, and the inductor L₃₁ is charging. The voltage difference between the positive bus DC+ and the negative bus DC− of the AC/DC converter is a voltage output within the time period from t₈₄ to t₈₅.

In the time period from t₈₆ to t₈₇, the alternating current is in the negative half cycle, the switch tube Q₃₁ and the switch tube Q₃₂ are on, and the switch tube Q₃₃ and the switch tube Q₃₄ are off. An equivalent circuit diagram of the AC/DC converter is shown in FIG. 7D, for an implementation, refer to the descriptions in FIG. 7D. Details are not described herein again.

In some implementations, FIG. 11 is a three-phase circuit diagram of an AC/DC converter according to an embodiment. As shown in FIG. 11, the AC/DC converter includes a three-phase circuit, and a circuit of each phase includes an inductor, an autotransformer, a first switching unit, a second switching unit, a first rectifier unit, and a second rectifier unit. In other words, the AC/DC converter may include three phase circuits described in FIG. 3, where the switching unit may be implemented as the circuit described in FIG. 4A or FIG. 4B.

In FIG. 11, an example in which the switching unit is implemented as the circuit described in FIG. 4A is used, and an alternating current power supply is implemented as an alternating current power grid, including three-phase voltages a, b, and c. A voltage of one phase is correspondingly input into a circuit of one phase.

It should be first noted that the AC/DC converter shown in FIG. 11 is applied to a three-phase three-wire circuit. The AC/DC converter provided in this embodiment may alternatively be applied to a three-phase four-wire circuit, a three-phase five-wire circuit, or the like. This is not limited.

For a schematic diagram of waveforms of the three-phase voltages a, b, and c, refer to FIG. 12. A phase difference between the three-phase voltages a, b, and c is 120°. At different moments, a status of a circuit of each phase may be considered as an independent process. In the three-phase circuit, the AC/DC converter in this embodiment may be in a plurality of states. For example, when the switching unit is implemented as that in FIG. 4A, at a T^th moment shown in FIG. 12, the a-phase voltage and the c-phase voltage are in a positive half cycle, and the b-phase voltage is in a negative half cycle. In this case, circuits of phases corresponding to the a-phase voltage and the c-phase voltage (that is, a branch into which a voltage V_a is input and a branch into which a voltage V_c is input) may be in the foregoing three states with reference to FIG. 6A to FIG. 6C. A circuit of a phase corresponding to the b-phase voltage (that is, a branch into which a voltage V_b is input) may be in the foregoing three states with reference to FIG. 6D to FIG. 6F. Therefore, at the T^th moment, the AC/DC converter may have 27 possible combinations of loop states.

For example, both the branch into which the voltage V_a is input and the branch into which the voltage V_c is input form the loop shown in FIG. 6A, and the branch into which the voltage V_b is input forms the loop shown in FIG. 6D. A ground cable of an alternating current power grid is different from a GND of the AC/DC converter. Therefore, a current output from the alternating current power grid needs to return to the ground cable of the alternating current power grid. That is, the three-phase circuit complies with the Kirchhoff's circuit laws. Currents on the branch into which the voltage V_a is input and the branch into which the voltage V_c is input flow back to the ground cable of the alternating current power grid through the branch into which the voltage V_b is input. In other words, a sum of phasors of currents in the three-phase circuit is zero.

In an implementation, after being input into an inductor L_a, the voltage V_a flows through a winding T_a1 and a winding T_a2 separately. A current on the winding T_a1 flows through a diode D_a1 and a switch tube Q_a1 to the GND of the AC/DC converter; and a current on the winding T_a2 flows through a diode D_a3, a rectifier diode D2, and a first capacitor C₁₀₁ to the GND of the AC/DC converter.

After being input to an inductor L_c, the voltage V_c flows through a winding T_c1 and a winding T_c2 separately. A current on the winding T_c1 flows through a diode D_c1 and a switch tube Q_c1 to the GND of the AC/DC converter; and a current on the winding T_c2 flows through a diode D_c3, a rectifier diode D₁₀, and the first capacitor C₁₀₁ to the GND of the AC/DC converter.

A current at the GND of the AC/DC converter may flow through a switch tube Q_b2, a diode D_b2, and a winding T_b1 to the ground cable of the alternating current power grid, or may flow through a second capacitor C₁₀₂, a rectifier diode D8, a diode D_b4, and a winding T_b2 to the ground cable of the alternating current power grid.

Optionally, both the branch into which the voltage V_a is input and the branch into which the voltage V_c is input form the loop shown in FIG. 6A, and the branch into which the voltage V_b is input forms the loop shown in FIG. 6E; both the branch into which the voltage V_a is input and the branch into which the voltage V_c is input form the loop shown in FIG. 6A, and the branch into which the voltage V_b is input forms the loop shown in FIG. 6F; the branch into which the voltage V_a is input form the loop shown in FIG. 6A, the branch into which the voltage V_c is input form the loop shown in FIG. 6B, and the branch into which the voltage V_b is input forms the loop shown in FIG. 6D; the branch into which the voltage V_a is input form the loop shown in FIG. 6A, the branch into which the voltage V_c is input form the loop shown in FIG. 6B, and the branch into which the voltage V_b is input forms the loop shown in FIG. 6E; or the branch into which the voltage V_a is input form the loop shown in FIG. 6A, the branch into which the voltage V_c is input form the loop shown in FIG. 6B, and the branch into which the voltage V_b is input forms the loop shown in FIG. 6F, or the like. Details are not described herein again.

It should be noted that the terms “first” and “second” are merely intended for a purpose of description and shall not be understood as an indication or implication of relative importance.

The foregoing descriptions are merely implementations but are not intended to limit the scope of the embodiments. Any variation or replacement readily figured out by a person skilled in the art shall fall within the scope the embodiments.

Claims

1. An AC/DC converter, wherein the AC/DC converter is disposed between an alternating current power supply and power-consuming equipment, the AC/DC converter comprising: a circuit of at least one phase that comprisesan inductor,an autotransformer,a first switching unit,a second switching unit,at least two first rectifier units corresponding to the first switching unit, andat least two second rectifier units corresponding to the second switching unit, the autotransformer comprises a first winding corresponding to the first switching unit and a second winding corresponding to the second switching unit, a first end of the inductor is coupled to the alternating current power supply, and a second end of the inductor is coupled to a first end of the first winding and a first end of the second winding, a second end of the first winding is coupled to a winding connection end of the first switching unit, and a second end of the second winding is coupled to a winding connection end of the second switching unit, a bus connection end of the first switching unit is coupled to a bus of the AC/DC converter through the at least two first rectifier units, a bus connection end of the second switching unit is coupled to the bus of the AC/DC converter through the at least two second rectifier units, and the bus of the AC/DC converter is coupled to the power-consuming equipment; and at least two groups of switching circuits are comprised between the winding connection end of any one of the switching units and a ground cable connection end of the switching unit, wherein each group of switching circuits comprises a diode and a controllable switch connected in series to the diode, and the controllable switch is configured to control a connection or disconnection between the winding connection end and the ground cable connection end of the switching unit comprising the controllable switch.

2. The AC/DC converter according to claim 1, further comprising: a controller configured to:send a first pulse control signal to a first controllable switch comprised in each group of switching circuits in the first switching unit, wherein the first pulse control signal is used to control on or off of the first controllable switch;send a second pulse control signal to a second controllable switch comprised in each group of switching circuits in the second switching unit, wherein the second pulse control signal is used to control on or off of the second controllable switch; and the first pulse control signal and the second pulse control signal have a same frequency, with a phase difference of 180°.

3. The AC/DC converter according to claim 1, wherein the at least two groups of switching circuits comprised in any one of the switching units comprise a first group of switching circuits and a second group of switching circuits, wherein the first group of switching circuits comprises a first diode and a first switch tube, the second group of switching circuits comprises a second diode and a second switch tube, and the bus of the AC/DC converter comprises a positive bus and a negative bus; and both an anode of the first diode and a cathode of the second diode are coupled to the second end of the winding corresponding to the switching unit, both a cathode of the first diode and a first end of the first switch tube are coupled to the positive bus of the AC/DC converter by using one rectifier unit in the two rectifier units corresponding to the switching unit, both an anode of the second diode and a second end of the second switch tube are coupled to the negative bus of the AC/DC converter by using the other rectifier unit in the two rectifier units corresponding to the switching unit, and both a second end of the first switch tube and a first end of the second switch tube are coupled to a ground cable of the AC/DC converter.

4. The AC/DC converter according to claim 1, wherein the at least two groups of switching circuits comprised in any one of the switching units comprise a first group of switching circuits and a second group of switching circuits, wherein the first group of switching circuits comprises a third diode and a third switch tube, the second group of switching circuits comprises a fourth diode and a fourth switch tube, and the bus of the AC/DC converter comprises a positive bus and a negative bus; and both a cathode of the third diode and a first end of the third switch tube are coupled to the positive bus of the AC/DC converter by using one rectifier unit in the two rectifier units corresponding to the switching unit, both a second end of the third switch tube and a first end of the fourth switch tube are coupled to the second end of the winding corresponding to the switching unit, both an anode of the fourth diode and a second end of the fourth switch tube are coupled to the negative bus of the AC/DC converter by using the other rectifier unit in the two rectifier units corresponding to the switching unit, and both an anode of the third diode and a cathode of the fourth diode are coupled to a ground cable of the AC/DC converter.

5. The AC/DC converter according to claim 3, further comprising: a first capacitor and a second capacitor, whereinthe first capacitor is coupled between the positive bus of the AC/DC converter and the ground cable of the AC/DC converter, and the second capacitor is coupled between the negative bus of the AC/DC converter and the ground cable of the AC/DC converter.

6. The AC/DC converter according to claim 1, wherein the AC/DC converter comprises a three-phase circuit, and a sum of phasors of currents in the three-phase circuit is zero.

7. The AC/DC converter according to claim 2, wherein the controller is further configured to: control duty ratios of the first pulse control signal and the second pulse control signal to be less than 0.5 when a voltage of the alternating current power supply is less than half of an output voltage of the AC/DC converter; orcontrol duty ratios of the first pulse control signal and the second pulse control signal to be greater than 0.5 when the voltage of the alternating current power supply is greater than half of the output voltage of the AC/DC converter.

8. The AC/DC converter according to claim 1, wherein winding turns of the first winding and the second winding are equal.

9. A charging apparatus, wherein the charging apparatus comprises an AC/DC converter and an electric meter, and the electric meter is connected in series between an alternating current power supply and the AC/DC converter which is disposed between an alternating current power supply and power-consuming equipment, the AC/DC converter comprises a circuit of at least one phase, a circuit of each phase comprises an inductor, an autotransformer, a first switching unit, a second switching unit, at least two first rectifier units corresponding to the first switching unit, and at least two second rectifier units corresponding to the second switching unit, and the autotransformer comprises a first winding corresponding to the first switching unit and a second winding corresponding to the second switching unit; a first end of the inductor is coupled to the alternating current power supply, and the second end of the inductor is coupled to a first end of the first winding and a first end of the second winding;the second end of the first winding is coupled to a winding connection end of the first switching unit, and the second end of the second winding is coupled to a winding connection end of the second switching unit;a bus connection end of the first switching unit is coupled to a bus of the AC/DC converter through the at least two first rectifier units, a bus connection end of the second switching unit is coupled to the bus of the AC/DC converter through the at least two second rectifier units, and the bus of the AC/DC converter is coupled to the power-consuming equipment; andat least two groups of switching circuits are comprised between the winding connection end of any one of the switching units and a ground cable connection end of the switching unit, wherein each group of switching circuits comprises a diode and a controllable switch connected in series to the diode, and the controllable switch is configured to control a connection or disconnection between the winding connection end and the ground cable connection end of the switching unit comprising the controllable switch;the AC/DC converter is configured to:convert an alternating current output from the alternating current power supply into a first direct current, andtransmit the first direct current to power-consuming equipment, and the electric meter is configured to measure electric energy supplied by the alternating current power supply to the power-consuming equipment.

10. The charging apparatus according to claim 9, further comprising: a DC/DC converter disposed between the AC/DC converter and the power-consuming equipment; andthe AC/DC converter transmits, via the DC/DC converter to the power-consuming equipment, the first direct current obtained by converting the alternating current output from the alternating current power supply, and the DC/DC converter is configured to:convert the first direct current to obtain a second direct current, andsupply the second direct current to the power-consuming equipment.

11. The charging apparatus according to claim 9, wherein the AC/DC converter further comprises a controller configured to: send a first pulse control signal to a first controllable switch comprised in each group of switching circuits in the first switching unit, wherein the first pulse control signal is used to control on or off of the first controllable switch;send a second pulse control signal to a second controllable switch comprised in each group of switching circuits in the second switching unit, wherein the second pulse control signal is used to control on or off of the second controllable switch; and the first pulse control signal and the second pulse control signal have a same frequency, with a phase difference of 180°.

12. The charging apparatus according to claim 9, wherein the at least two groups of switching circuits comprised in any one of the switching units comprise a first group of switching circuits and a second group of switching circuits, the first group of switching circuits comprises a first diode and a first switch tube, the second group of switching circuits comprises a second diode and a second switch tube, and the bus of the AC/DC converter comprises a positive bus and a negative bus; and both an anode of the first diode and a cathode of the second diode are coupled to the second end of the winding corresponding to the switching unit, both a cathode of the first diode and a first end of the first switch tube are coupled to the positive bus of the AC/DC converter by using one rectifier unit in the two rectifier units corresponding to the switching unit, both an anode of the second diode and a second end of the second switch tube are coupled to the negative bus of the AC/DC converter by using the other rectifier unit in the two rectifier units corresponding to the switching unit, and both a second end of the first switch tube and a first end of the second switch tube are coupled to a ground cable of the AC/DC converter.

13. The charging apparatus according to claim 9, wherein the at least two groups of switching circuits comprised in any one of the switching units comprise a first group of switching circuits and a second group of switching circuits, the first group of switching circuits comprises a third diode and a third switch tube, the second group of switching circuits comprises a fourth diode and a fourth switch tube, and the bus of the AC/DC converter comprises a positive bus and a negative bus; and both a cathode of the third diode and a first end of the third switch tube are coupled to the positive bus of the AC/DC converter by using one rectifier unit in the two rectifier units corresponding to the switching unit, both a second end of the third switch tube and a first end of the fourth switch tube are coupled to the second end of the winding corresponding to the switching unit, both an anode of the fourth diode and a second end of the fourth switch tube are coupled to the negative bus of the AC/DC converter by using the second rectifier unit in the two rectifier units corresponding to the switching unit, and both an anode of the third diode and a cathode of the fourth diode are coupled to a ground cable of the AC/DC converter.

14. The charging apparatus according to claim 13, wherein the AC/DC converter further comprises a first capacitor coupled between the positive bus of the AC/DC converter and the ground cable of the AC/DC converter and a second capacitor coupled between the negative bus of the AC/DC converter and the ground cable of the AC/DC converter.

15. The charging apparatus according to claim 9, wherein the AC/DC converter further comprises a three-phase circuit and a sum of phasors of currents in the three-phase circuit is zero.

16. The charging apparatus according to claim 11, wherein the controller is further configured to: control duty ratios of the first pulse control signal and the second pulse control signal to be less than 0.5 when a voltage of the alternating current power supply is less than half of an output voltage of the AC/DC converter; orcontrol duty ratios of the first pulse control signal and the second pulse control signal to be greater than 0.5 when the voltage of the alternating current power supply is greater than half of the output voltage of the AC/DC converter.

17. The AC/DC converter according to claim 9, wherein winding turns of the first winding and the second winding are equal.