The present invention relates to a high-voltage battery charging system, and more particularly to a high-voltage battery charging system for use in an electric vehicle.
Fossil fuels such as petroleum and coal are widely used in automobiles or power plants for generating motive force or electrical power. As known, burning fossil fuels produces waste gases and carbon oxide. The waste gases may pollute the air. In addition, carbon dioxide is considered to be a major cause of the enhanced greenhouse effect. It is estimated that the world's oils supply would be depleted in the next several decades. The oil depletion may lead to global economic crisis.
Consequently, there are growing demands on clean and renewable energy. Recently, electric vehicles and plug-in hybrid electric vehicles have been researched and developed. Electric vehicles and plug-in hybrid electric vehicles use electrical generators to generate electricity. In comparison with the conventional gasoline vehicles and diesel vehicles, the electric vehicles and hybrid electric vehicles are advantageous because of low pollution, low noise and better energy utilization. The uses of the electric vehicles and hybrid electric vehicles can reduce carbon dioxide release in order to decelerate the greenhouse effect.
As known, an electric vehicle or a plug-in hybrid electric vehicle has a built-in battery as a stable energy source for providing electric energy for powering the vehicle. In a case that the electric energy stored in the battery is exhausted, the battery is usually charged by a battery charger. Generally, the current battery charger has an isolated architecture, and a transformer is an essential component in an electric energy path of an isolated DC-DC converter. During the process of converting electric energy by the transformer, magnetic loss (iron loss) and wire loss (copper loss) are incurred. That is, the power loss of the isolated DC-DC converter is very high. In this situation, the charging time of the battery is long. Moreover, since an insulating tape or a three-layered insulating wire is required for isolating the primary winding from the secondary winding of the transformer, the process of fabricating the transformer is complicated and costly.
Therefore, there is a need of providing a high-voltage battery charging system for use in an electric vehicle so as to obviate the drawbacks encountered from the prior art.
It is an object of the present invention to provide a high-voltage battery charging system for use in an electric vehicle in order to reduce power loss, reduce the fabricating cost, shorten the charging time, and increase the operating efficiency.
In accordance with an aspect of the present invention, there is provided a high-voltage battery charging system for use in an electric vehicle. The high-voltage battery charging system is installed in a vehicle body of the electric vehicle for charging a high-voltage battery unit within the vehicle body. The high-voltage battery charging system includes a rectifier circuit, a power factor correction circuit and a non-isolated DC-DC converting circuit. The rectifier circuit is connected to a common terminal for rectifying an AC input voltage into a rectified voltage. The power factor correction circuit is connected to the rectifier circuit and a bus for increasing a power factor and generating a bus voltage. The non-isolated DC-DC converting circuit is connected to the power factor correction circuit and the high-voltage battery unit for charging the high-voltage battery unit, wherein no transformer is included in the non-isolated DC-DC converting circuit.
The above contents of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:
The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.
In this embodiment, the high-voltage battery charging system further comprises an electromagnetic interference (EMI) filtering circuit 6. The EMI filtering circuit 6 is connected to the input side of the rectifier circuit 3 for filtering off the surge and high-frequency noise contained in the AC input voltage Vin and the AC input current Iin. In addition, the use of the EMI filtering circuit 6 can reduce the electromagnetic interference resulted from the switching circuits of the non-isolated DC-DC converting circuit 5 and the PFC circuit 4, so that the adverse influence of the electromagnetic interference on the AC input voltage Vin and the AC input current Iin will be minimized. After the surge and high-frequency noise are filtered off by the EMI filtering circuit 6, the AC input voltage Vin and the AC input current Iin are transmitted to the input side of the rectifier circuit 3. The AC input voltage Vin is rectified into a rectified voltage Vr by the rectifier circuit 3.
The PFC circuit 4 is interconnected between the rectifier circuit 3 and a bus B1 for increasing the power factor and generating a bus voltage Vbus. The non-isolated DC-DC converting circuit 5 is interconnected between the PFC circuit 4 and the high-voltage battery unit 2 for converting the bus voltage Vbus into a charging voltage VHb. The high-voltage battery unit 2 is charged by the charging voltage VHb. The bus capacitor Cbus is interconnected between the bus B1 and a common terminal COM for energy storage and voltage stabilization. In accordance with a key feature of the present invention, no transformer is included in the electric energy path of the non-isolated DC-DC converting circuit 5. By mean of a switching circuit and an output filter circuit of the non-isolated DC-DC converting circuit 5, the high-voltage battery unit 2 is charged by the charging voltage VHb.
In this embodiment, the magnitude of the AC input voltage Vin is 110˜380 volts, the magnitude of the bus voltage Vbus is 350˜450 volts, and the magnitude of the charging voltage VHb is 200˜380 volts. The rectifier circuit 3, the PFC circuit 4, the non-isolated DC-DC converting circuit 5, the EMI filtering circuit 6 and the bus capacitor Cbus of the high-voltage battery charging system 7 and the high-voltage battery unit 2 are operated at high voltage values. As such, the high-voltage battery charging system 7 has low charging loss and short charging time during the charging process and has low power loss and enhanced efficiency during the driving process. Generally, voltage values of the high-voltage battery charging system 7 and the high-voltage battery unit 2 are higher than the safety extra-low voltage (e.g. 36V). For preventing the AC input voltage Vin, the bus voltage Vbus or the charging voltage VHb from attacking the driver or passengers within the electric vehicle body 1, a high voltage-resistant insulating material is used to separate or isolate the high-voltage battery charging system 7 and the high-voltage battery unit 2 from the electric vehicle body 1 where the driver or passengers is touchable. Alternatively, the high-voltage battery charging system 7 and the high-voltage battery unit 2 are separated from the electric vehicle body 1 by at least a specified safety distance (e.g. 3˜8 mm, 5 mm, 6 mm, 6.5 mm, 7 mm, 9 mm or 12 mm).
In an embodiment, the high-voltage battery charging system 7 and the high-voltage battery unit 2 are contained in respective insulated containers. In addition, the high-voltage battery charging system 7 is connected with the high-voltage battery unit 2 and the utility power source via high voltage-resistant cables with insulating covering (not shown). As such, the charging voltage VHb and the AC input voltage Vin are respectively transmitted to the high-voltage battery unit 2 and the high-voltage battery charging system 7 through the high voltage-resistant cables.
In some embodiments, for protecting the driver or passengers, the surface of the electric vehicle body 1 is coated with a high voltage-resistant insulating material (e.g. an insulating varnish) or an insulating spacer is disposed at the contact region between the electric vehicle body 1, the high-voltage battery charging system 7 and the high-voltage battery unit 2.
An example of the non-isolated DC-DC converting circuit 5 includes but is not limited to a buck non-isolated DC-DC converting circuit, a buck-boost non-isolated DC-DC converting circuit or a boost non-isolated DC-DC converting circuit. An example of the PFC circuit 4 includes but is not limited to a continuous conduction mode (CCM) boost PFC circuit, a direct coupling modulated bias (DCMB) boost PFC circuit, a buck PFC circuit or a buck-boost PFC circuit. The high-voltage battery unit 2 includes one or more batteries such as lead-acid batteries, nickel-cadmium batteries, nickel iron batteries, nickel-metal hydride batteries, lithium-ion batteries, or a combination thereof.
In a case that the first switching circuit 41 is conducted, the first inductor L1 is in a charge status and the current magnitude of the first current I1 is increased. The first current I1 will be transmitted from the first inductor L1 to the first current-detecting circuit 42 through the first switching circuit 41, so that a current-detecting signal Vs is generated by the first current-detecting circuit 42. Whereas, in a case that the first switching circuit 41 is shut off, the first inductor L1 is in a discharge status and the current magnitude of the first current I1 is decreased. The first current I1 will be transmitted to the bus capacitor Cbus through the first diode D1.
In this embodiment, the power factor correction controlling unit 43 comprises an input waveform detecting circuit 431, a first feedback circuit 432 and a power factor correction controller 433. The input waveform detecting circuit 431 is connected to the positive input terminal of the rectifier circuit 3, the power factor correction controller 433 and the common terminal COM. The input waveform detecting circuit 431 is used for reducing the voltage magnitude of the rectified voltage Vr and filtering off the high-frequency noise contained in the rectified voltage Vr thereby generating an input detecting signal Vra. The waveform of the input detecting signal Vra is identical to that of the AC input voltage Vin after being rectified. The first feedback circuit 432 is connected to the bus B1, the power factor correction controller 433 and the common terminal COM. The bus voltage Vbus is subject to voltage-division by the first feedback circuit 432, thereby generating a first feedback signal Vf1.
In other words, the power factor correction controller 433 acquires the waveform of the AC input voltage Vin by the detecting signal Vra. The power factor correction controller 433 discriminates whether the bus voltage Vbus is maintained at the rated voltage value (e.g. 450V) by the first feedback signal Vf1. The increase magnitude of the first current I1 is detected by the current-detecting signal Vs. According to the detecting signal Vra, Vf1, and Vs, the power factor correction controller 433 controls the duty cycle of the first switching circuit 41. As a consequence, the bus voltage Vbus is maintained at the rated voltage value, and the distribution of the AC input current Iin is similar to the waveform of the AC input voltage Vin. The distribution of the first current I1 is similar to the waveform of the AC input voltage Vin after being rectified. As shown in
In this embodiment, the non-isolated DC-DC converting circuit 5 is a single-phase non-isolated DC-DC converting circuit. The non-isolated DC-DC converting circuit 5 comprises a second inductor L2, a second diode D2 (a second rectifier element), a first output capacitor Co1, a second switching circuit 51a and a DC-DC controlling unit 52. The second inductor L2, the second diode D2 (a second rectifier element), the first output capacitor Co1 and the second switching circuit 51a define a first phase power circuit. The second inductor L2 is interconnected between a second connecting node K2 and the high-voltage battery unit 2. The second diode D2 is interconnected between the second connecting node K2 and the common terminal COM. The first output capacitor Co1 is interconnected between the high-voltage battery unit 2 and the common terminal COM. The second switching circuit 51a is interconnected between the bus B1 and the second connecting node K2. The DC-DC controlling unit 52 is connected to the control terminal of the second switching circuit 51a, the common terminal COM and the high-voltage battery unit 2. According to the charging voltage VHb, the on/off statuses of the second switching circuit 51a are controlled by the DC-DC controlling unit 52.
In this embodiment, the DC-DC controlling unit 52 comprises a second feedback circuit 521 and a DC-DC controller 522. The second feedback circuit 521 is connected to the high-voltage battery unit 2, the DC-DC controller 522 and the common terminal COM. The charging voltage VHb is subject to voltage-division by the second feedback circuit 521, thereby generating a second feedback signal Vf2. The DC-DC controller 522 is connected to the control terminal of the second switching circuit 51a, the second feedback circuit 521 and the common terminal COM. According to the second feedback signal Vf2, the DC-DC controller 522 discriminates whether the charging voltage VHb is maintained at the rated voltage value (e.g. 380V). As a consequence, the duty cycle of the second switching circuit 51a is controlled, and the charging voltage VHb is maintained at the rated voltage value.
The electric energy path of the non-isolated DC-DC converting circuit 5 passes through the second switching circuit 51a and the second inductor L2. In other words, no transformer is included in the non-isolated DC-DC converting circuit 5. In the non-isolated DC-DC converting circuit 5, a first output filter circuit is defined by the second inductor L2 and the first output capacitor Co1. The operations of the first output filter circuit and the second switching circuit 51a cause the high-voltage battery unit 2 to be charged by the charging voltage VHb. That is, by the switching circuit and the output filter circuit of the non-isolated DC-DC converting circuit 5, the high-voltage battery unit 2 is charged by the charging voltage VHb.
The third inductor L3 is interconnected between a third connecting node K3 and the high-voltage battery unit 2. The third diode D3 is interconnected between the third connecting node K3 and the common terminal COM. The second output capacitor Co2 is interconnected between the high-voltage battery unit 2 and the common terminal COM. The third switching circuit 51b is interconnected between the bus B1 and the third connecting node K3. The DC-DC controlling unit 52 is connected to the control terminal of the second switching circuit 51a, the control terminal of the third switching circuit 51b, the common terminal COM and the high-voltage battery unit 2. According to the charging voltage VHb, the second switching circuit 51a and the third switching circuit 51b are alternately conducted under control of the DC-DC controlling unit 52. As a consequence, the duty cycles of the second switching circuit 51a and the third switching circuit 51b are controlled, and the charging voltage VHb is maintained at the rated voltage value.
In this embodiment, since the non-isolated DC-DC converting circuit 5 is a multi-phase converting circuit, the high-voltage battery charging system 7 has enhanced operating efficiency and enhanced heat dissipating efficiency when the high-voltage battery charging system 7 is applied to an electric vehicle having higher charging power (e.g. 1000 or 2000 Watts).
In the above embodiments, the rectifier circuit 3 is a bridge rectifier circuit. The positive output terminal of the rectifier circuit 3 is connected to the input terminal of the power factor correction circuit 4. The negative output terminal of the rectifier circuit 3 is connected to the common terminal COM. An example of the first current-detecting circuit 42 includes but is not limited to a current transformer or a detecting resistor Rs. Each of the first switching circuit 41, the second switching circuit 51a and the third switching circuit 51b includes one or more switch elements. The switch element is a metal oxide semiconductor field effect transistor (MOSFET), a bipolar junction transistor (BJT) or an insulated gate bipolar transistor (IGBT). In this embodiment, each of the first switching circuit 41, the second switching circuit 51a and the third switching circuit 51b includes a metal oxide semiconductor field effect transistor (MOSFET). Each of the power factor correction controller 433 and the DC-DC controller 522 includes a controller, a micro controller unit (MCU) or a digital signal processor (DSP).
The waveform of the AC input current Iin indicates that the AC input current Iin is not rectified and the surge and high-frequency noise contained in the AC input current Iin has been filtered off by the EMI filtering circuit 6. In this embodiment, the electromagnetic interference resulted from the switching circuits of the non-isolated DC-DC converting circuit 5 and the PFC circuit 4 is minimized. The distribution of the AC input current Iin is similar to the waveform of the AC input voltage Vin. The envelop curve of the AC input current Iin is similar to the waveform of the AC input voltage Vin. The phase of the AC input current Iin is similar to that of the AC input voltage Vin. Since the phase difference is very low (e.g. 1˜15 degrees), a better power factor correction function is achieved.
From the above description, since no transformer is included in the electric energy path of the non-isolated DC-DC converting circuit of the high-voltage battery charging system according to the present invention, the power loss and the fabricating cost are both reduced, the charging time is shortened, and the operating efficiency is enhanced. Moreover, since the operating voltages of the high-voltage battery charging system and the high-voltage battery unit are very high, the charging loss is reduced and the charging time is further shortened. By means of the power factor correction circuit and the electromagnetic interference filtering circuit, the power factor is enhanced and the electromagnetic interference is reduced.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
Number | Date | Country | Kind |
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200910262532.1 | Dec 2009 | CN | national |