Patent Application
20130193910
This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2012-019467 filed Feb. 1, 2012, the description of which is incorporated herein by reference.
1. Technical Field
The present invention relates to an electric power transmission device, which includes a relay capacitor and transmits an electric power from a power supply to a battery via the relay capacitor.
2. Related Art
This type of electric power transmission device is proposed in, for example, Japanese Patent No. 4655250. This device includes a rectifier unit, a step-up chopper circuit for power factor correction (PFC) control, and a relay capacitor. The rectifier unit rectifies an alternating current (AC) power supplied from a commercial power supply to thereby produce a direct current (DC) power, and outputs the DC power to the step-up chopper circuit. The step-up chopper circuit is connected to the rectifier section and steps up the DC power outputted from the rectifier section. This step-up chopper circuit is provided with an output capacitor which is connected to the relay capacitor via a power supply side switching element. The relay capacitor is connected to an on-board battery via a battery side switching element. This can supply the electric power of the commercial power supply to the on-board battery while isolating the on-board battery from the commercial power supply.
However, in the electric power transmission device described above, when the power supply side switching element, provided between the output capacitor of the step-up chopper circuit and the relay capacitor, is turned on, a large current called an inrush current is allowed to flow from the output capacitor to the relay capacitor. This may decrease a reliability of the switching element.
An exemplary embodiment provides an electric power transmission device that includes a relay capacitor and transmits an electric power, which is able to prevent a large current from flowing to the relay capacitor and to avoid decrease in its reliability.
According to an exemplary aspect of the present disclosure, there is provided an electric power transmission device for transmitting an electric power of a power supply to a battery, comprising: a relay capacitor located between the power supply and the battery, the relay capacitor storing an electric power of the power supply; a power supply side switching element configured to open and close a first electrical path between the power supply and the relay capacitor; and a battery side switching element configured to open and close a second electrical path between the relay capacitor and the battery that is an object to which the electric power is supplied from the power supply, the battery side switching element having a pair of ends in the second electrical path, one of which is connected to the relay capacitor, wherein: the power supply side switching element has a pair of ends in the first electrical path, one of which is connected to the relay capacitor and the other is not connected to an output capacitor that is short-circuited with the relay capacitor when the power supply side switching element is closed.
According to this configuration, the other of pair of ends of the power supply side switching element, which is not connected to the relay capacitor, is not connected to another capacitor (for example, an output capacitor provided at an output side of a step-up chopper circuit) that is short-circuited with the relay capacitor when the power supply side switching element is closed. Thus, even when the battery side switching element is closed, a large current such as inrush current does not flow from another capacitor such as an output capacitor provided at an output side of a step-up chopper circuit to the relay capacitor. This makes it possible to prevent a large current from flowing to the relay capacitor and to avoid decrease in its reliability.
In the accompanying drawings:
Hereinafter, with reference to the accompanying drawings, exemplary embodiments of the present disclosure will be described. In these exemplary embodiments, an electric power transmission device of the present disclosure is applied to an on-board electric power transmission device mounted in a vehicle.
First, with reference to
As shown in
The high-voltage battery 10 shown in
The high-voltage battery 10 is arranged so as to have higher impedance than a vehicle body. In the present exemplary embodiment, a median value between a positive electrode and a negative electrode of the high-voltage battery 10 is set to be an electric potential of the vehicle body. This can be achieved by setting an electric potential of a connection point between two resistors 18, 20, connected in parallel to the high-voltage battery 10, to the electric potential of the vehicle body. Here, the resistors 18, 20 have a large resistance which is able to much increase the impedance between the high-voltage battery 10 and the vehicle body.
In the present exemplary embodiment, the electric power transmission device 1 supplies an electric power of the commercial power supply 40 outside the vehicle to the high-voltage battery 10. The electric power transmission device 1 includes a power supply side filter 32, a full wave rectifier circuit 30, a step-up chopper circuit 28, power supply side switching elements (hereinafter referred to as “power supply side open/close elements”) Ssp, Ssn, a relay capacitor 26, battery side switching elements (hereinafter referred to as “battery side open/close elements”) Sbp, Sbn, a smoothing filter 24, a battery side filter 22, an interface 50, and a controller 52, between the commercial power supply 40 and the high-voltage battery 10.
As shown in
In this configuration, the full wave rectifier circuit 30 rectifies an AC power supplied via the input terminal through the power supply side filter 32 from the commercial power supply 40 to thereby produce DC power, and outputs the DC power via the output terminal.
The step-up chopper circuit 28 is connected to the full wave rectifier circuit 30. This step-up chopper circuit 28 includes an inductor Lc, a chopper control switching element Sc, and a diode Dc. The inductor Lc stores an electric power outputted from the full wave rectifier circuit 30. The chopper control switching element Sc applies an output voltage of the full wave rectifier circuit 30 to both ends of the inductor Lc. The diode Dc outputs an electric power stored in the inductor Lc.
In this configuration, the step-up chopper circuit 28 steps up the DC power outputted from the full wave rectifier 30, and outputs the stepped up DC power.
The relay capacitor 26 is connected to the step-up chopper circuit 28 via the power supply side open/close elements Ssp, Ssn. The power supply side open/close elements Ssp, Ssn are configured to open and close a first electrical path between the commercial power supply 40 and the relay capacitor 26. The power supply side open/close elements Ssp, Ssn are closed and opened under electronic control. When the power supply side open/close elements Ssp, Ssn are opened, current does not flow in a direction from one to the other of both ends of a current flow path which is an opened/closed object as well as a direction from the other to one thereof.
In the present exemplary embodiment, the power supply side open/close elements Ssp, Ssn are configured by a pair of N-channel metal-oxide semiconductor field-effect transistors (MOSFETs) in which a short circuit is formed between each source of the pair thereof. The purpose of this short circuit is to make it easy to turn on and off the pair of N-channel MOSFETs. In general, N-channel MOSFET is turned on and off depending on an electric potential of its gate to its source. Then, a short circuit is formed between the sources of the pair of N-channel MOSFETs, thereby allowing the electric potential of these sources to be the same as each other, and making it possible to turn on and off the pair of N-channel MOSFETs by using a single voltage signal.
The relay capacitor 26 is connected to the smoothing filter 24 via the battery side open/close elements Sbp, Sbn. The battery side open/close elements Sbp, Sbn are configured to open and close a second electrical path between the relay capacitor 26 and the battery 10. The battery side open/close elements Sbp, Sbn are closed and opened under electronic control. When the battery side open/close elements Sbp, Sbn are opened, current does not flow in a direction from one to the other of both end portions of a current flow path which is an opened/closed object as well as a direction from the other to one thereof In the present exemplary embodiment, the battery side open/close elements Sbp, Sbn are configured by a pair of N-channel MOSFETs in which a short circuit is formed between each source of the pair thereof. The purpose of this short circuit is the same as that of the power supply side open/close elements Ssp, Ssn.
The smoothing filter 24 includes an energy storing inductor 24a, a diode which is connected in parallel to the relay capacitor 26, and a capacitor 24 which is connected in parallel to the relay capacitor via the energy storing inductor 24a. This smoothing filter 24 is a circuit that, regardless of intermittent closing operation of the battery side open/close elements Sbp, Sbn, prevents rapid change in current outputted to the side of the high-voltage battery 10.
The smoothing filter 24 is connected to the high voltage battery 10 via the battery side filter 22. This battery side filter 22 is configured by including, for example, a common-mode choke coil, X capacitor, and a Y capacitor.
As shown in
In the present exemplary embodiment, the step-up chopper circuit 28 is not provided with an output capacitor provided on the output side thereof. In other words, the relay capacitor 26 is used as a substitute for a capacitor (output capacitor) provided at an output side of a well-known step-up chopper circuit. Thus, there is no capacitor which is short-circuited with the relay capacitor 26 via the power supply side open/close elements Ssp, Ssn when the power supply side open/close elements Ssp, Ssn are closed. This is because, with such a short-circuited output capacitor (i.e., output capacitor), a large current called an inrush current may flow from this capacitor to the relay capacitor 26 due to a closing operation of the power supply side open/close elements Ssp, Ssn. The purpose of the above configuration with no output capacitor of the step-up chopper circuit is to avoid such a situation.
Beside this, in order to avoid the above situation where a large current may flow, the following techniques (i) and (ii) may be also considered:
(i) decreasing a capacitance of the relay capacitor 26; and
(ii) increasing an electric resistance between the step-up chopper circuit 28 and the relay capacitor 26 such as on-resistance of the power supply side open/close elements Ssp, Ssn.
However, the technique (i) is likely to excessively decrease an electric power which can be transmitted during one period of open/close of the power supply side open/close elements Ssp, Ssn. This leads to a decrease in a transmission rate of the electric power. To cope with this situation, a technique for increasing an open/close rate of the power supply side open/close elements Ssp, Ssn may be further considered. However, this technique is likely to increase a switching loss of the power supply side open/close elements Ssp, Ssn.
On the other hand, the technique (ii) is likely to increase electric power loss and to decrease electric power transmission efficiency.
In contrast, in the present exemplary embodiment, the relay capacitor 26 is used as a substitute for a capacitor on the output side of the step-up chopper circuit 28. Thus, the inductor Lc can restrict a change rate of current flows into the relay capacitor 26 due to close-operation of the power supply side open/close elements Ssp, Ssn. Specifically, when the chopper control switching element Sc is switched on, current flows in a loop path (first loop path) including the full wave rectifier circuit 30, the inductor Lc, and the chopper control switching element Sc, and then, energy is stored in the inductor Lc. When the chopper control switching element Sc is then switched off, current flows in a loop path (second loop path) including the full wave rectifier circuit 30, the inductor Lc, and the relay capacitor 26. In this case, an increasing rate of current flowing into to the relay capacitor 26 is restricted by inductance of the inductor Lc. This can decrease an electrical resistance of an electrical path from a cathode side of the diode Dc to the relay capacitor 26, or increase a capacitance of the relay capacitor 26 to some extent.
In this case, if the power supply side open/close elements Ssp, Ssn are opened when the chopper control switching element Sc is changed from a switching-on condition into an switching-off condition, a voltage of the anode side of the diode Dc may be excessively increased.
To cope with this, in the present exemplary embodiment, the power supply side open/close elements Ssp, Ssn and the battery side open/close elements Sbp, Sbn are operated in such a manner as shown in
Here, a time period Tm1, between a timing at which the power supply side open/close elements Ssp, Ssn are closed and a timing at which the chopper control switching element Sc is switched off, is set to be same as a time period Tm1 between a timing at which the chopper control switching element Sc is switched on and a timing at which the power supply side open/close elements Ssp, Ssn are opened. These time periods Tm1 are set to be equal to or larger than a time required for the chopper control switching element Sc and the power supply side open/close elements Ssp, Ssn to be switched on/off.
On the other hand, the battery side open/close elements Sbp, Sbn are operated so as to prevent a situation where an isolation (insulation) between the side of the high-voltage battery 10 and the side of the commercial power supply 40 is not kept. This is because both of the power supply side open/close elements Ssp, Ssn and the battery side open/close elements Sbp, Sbn are closed. In other words, the battery side open/close elements Sbp, Sbn are closed while the power supply side open/close elements Ssp, Ssn are opened. This can be achieved by such an operation that the power supply side open/close elements Ssp, Ssn are opened before the battery side open/close elements Sbp, Sbn are closed, and the power supply side open/close elements Sbp, Sbn are closed after the battery side open/close elements Sbp, Sbn are opened.
Here, a time period Tm2, between a timing at which the power supply side open/close elements Ssp, Ssn are opened and a timing of at which the battery side open/close elements Sbp, Sbn are closed, is set to be same as a time period Tm2 between a timing at which the battery side open/close elements Sbp, Sbn are opened and a timing at which the the power supply side open/close elements Ssp, Ssn are closed. These time periods Tm2 are set to be equal to or larger than a time required for the battery side open/close elements Sbp, Sbn and the power supply side open/close elements Ssp, Ssn to be closed and opened. This is so called a dead time setting.
The purpose of the switching-on/off operation of the chopper control switching element Sc is to use the set-up chopper circuit 28 as a power factor correction (PFC) circuit. Then, a time ratio of a switching-on period to one switching-on/off period is variably operated depending on a phase of an output current of the full wave rectifier circuit 30. In this regard, a switching frequency itself may be set to be variable.
In a series of processes, first, at step S10, the controller 52 judges whether or not the commercial power supply 40 is connected to the connector C. As a result, if judged that there is the time (YES) at step S10, at step S12, the controller 52 judges whether or not an output voltage V of the full wave rectifier circuit 30 is equal to or smaller than a prescribed voltage Vth. The purpose of this process is to judge whether or not there is a zero-cross timing of an output current of the full wave rectifier circuit 30. Then, if an affirmative judgment (YES) is obtained at step S12, the controller 52 permits the power supply side open/close elements Ssp, Ssn to close at step S14.
If a negative judgment (NO) is obtained at step S10 or a process of step S14 is completed, the series of processes is temporarily terminated.
These processes can avoid a situation where inrush current flows in the relay capacitor 26. Thus, there is no need for providing a pre-charge high impedance path between the full wave rectifier circuit 30 and the relay capacitor 26.
As described above, according to a configuration of the present exemplary embodiment, an electric power of the commercial power supply 40 can be transmitted to the high-voltage battery 10, while isolating the high-voltage battery 10 from the commercial power supply 40. Thus, for example, even when there is a member for making contact between an output terminal on a low voltage side (an anode of the diodes 30b, 30d) and the vehicle body, it is possible to prevent occurrence of a situation where the high-voltage battery 10 is charged and discharged via this member.
In addition, in the present exemplary embodiment, the power supply side open/close elements Ssp, Ssn and the battery side open/close elements Sbp, Sbn are provided at both of an positive electrode side and a negative electrode side, and are designed such that current is prevent from flowing in any directions, thereby largely contributing to an improvement of isolation performance between the high-voltage battery 10 and the commercial power supply 40.
Further, it is possible to easily reduce a loss due to electric power transmission compared to a case where a power conversion circuit with a transformer is used. This is because there is no power loss due to the transformer. In particular, it is possible to more easily reduce this loss because techniques for reducing on-resistance of MOSFETs have advanced in recent years and then a conduction loss of the power supply side open/close elements Ssp, Ssn and the battery side open/close elements Sbp, Sbn can be reduced. Thus, a cooling device for the electric power transmission can be configured by an air-cooling system, not a water-cooling system which is usually used.
Here, a period capable of outputting energy charged in the relay capacitor 26 into the side of the smoothing filter 24 is limited to a period during which the battery side open/close elements Sbp, Sbn are closed. However, when the battery side open/close elements Sbp, Sbn are opened, energy stored in the energy storing inductor 24a can flow in a loop path including the energy storing inductor 24a and the diode 24b. Thus, even while the battery side open/close elements Sbp, Sbn are opened, energy stored in the energy storing inductor 24a can be outputted to the high-voltage battery 10. Here, it is preferable that an inductance of the inductor 24a is set such that, if there is a certain amount of electric power transmission, current flowing in the inductor 24a gradually decreases but does not reduce to zero while the battery side open/close elements Sbp, Sbn are opened.
Next, a second exemplary embodiment is described, focusing on the differences from the first exemplary embodiment.
As shown in
As shown in
Here, a period during which the battery side open/close elements Sbpa, Sbna (the battery side open/close elements Sbpb, Sbnb) are closed may be set to an arbitrary long time within a period during which the power supply side open/close elements Sspa, Ssna (the power supply side open/close elements Sspb, Ssnb) are opened. In the present exemplary embodiment, the period during which the battery side open/close elements Sbpa, Sbna are in the closed condition is set to be equal to the period during which the power supply side open/close elements Sspb, Ssnb are closed. In addition, the period during which the battery side open/close elements Sbpb, Sbnb are closed is set to be equal to the period during which the power supply side open/close elements Sspa, Ssna are closed. The purpose of these setting is to simplify a configuration by matching an operation signal for the battery side open/close elements Sbpa, Sbna and an operation signal for the power supply side open/close elements Sspb, Ssnb as well as by matching an operation signal for the battery side open/close elements Sbpb, Sbnb and an operation signal for the power supply side open/close elements Sspa, Ssna.
Next, a third exemplary embodiment is described, focusing on the differences from the first exemplary embodiment.
In the an electric power transmission device 1b of the present exemplary embodiment, the full wave rectifier circuit 30 and the step-up chopper circuit 28 share the diodes Dc1, Dc2. Specifically, as shown in
The above configuration which is also called a bridgeless boost is applied in the present exemplary embodiment. Compared to the configuration shown in
The first to third exemplary embodiments described above may be implemented in modifications as set forth below.
In the first to third exemplary embodiments described above, the power supply side open/close elements and the battery side open/close elements are configured by a pair of N-channel MOSFETs whose sources are short-circuited with each other, but are not limited to this in the present disclosure. For example, they may be configured by a pair of N-channel MOSFETs whose drains are short-circuited with each other. In this case, the electric power transmission device may be provided with a driving circuit for driving the pair of N-channel MOSFETs. The driving circuit may be configured individually for each of the pair of N-channel MOSFETs. As substitute for the N-channel MOSFETs, P-channel MOSFETs may be used as MOSFETs.
In the first to third exemplary embodiments described above, the pair of MOSFETs is provided with blocking means for blocking bidirectional flow of current when the power supply side open/close elements and the battery side open/close elements are electronically operated to be changed into the opened condition. The blocking means is not limited to this configuration using the pair of MOSFETs.
For example, as shown in
For example, as shown
For example, in the configuration of the first exemplary embodiment (see
In the first exemplary embodiment (see
In the exemplary embodiments described above, the inductor Lc configuring the step-up chopper circuit 28 is used. As a substitute for this, an inductor configuring a step-up/down circuit may be used. This step-up/down circuit may include: (i) a first series connection of a pair of switching elements connected in parallel to the full wave rectifier circuit 30; (ii) a second series connection of a pair of switching elements connected in parallel to the relay capacitor 26; and (iii) an inductor connecting a connection point of the first series connection and a connection point of second series connection.
In the first to third exemplary embodiments described above, the switching control means of the controller 52 is configured to control the chopper control switching element Sc, the power supply side open/close elements Ss# (#=p, n) and the battery side open/close elements Sb# (#=p, n) such that: (i) the power supply side open/close elements Ss# are closed (i.e., a close/open command for the power supply side open/close elements Ss# is change into a close command) before the chopper control switching element Sc is switched off (i.e., a switching-on/off command for the chopper control switching element Sc is changed into a switching-off command); and (ii) the power supply side open/close elements Ss# are opened (i.e., the close/open command for the power supply side open/close elements SO is change into an open command) after the chopper control switching element Sc is switched on (i.e., the switching-on/off command for the chopper control switching element Sc is changed into a switching-on command). The switching control means is not limited to this.
For example, when a transmission time of a command (switching-on/off command) for changing a switching condition of the power supply side open/close elements Ss# is shorter than that of the chopper control switching element Sc, a switching of the switching-off command for the chopper control switching element Sc may be synchronized with a switching of the close command for the power supply side open/close elements Ss#.
In the second exemplary embodiments (see
(Plurality of Sets of Relay Capacitors and Power supply Side/Battery Side Open/Close Elements)
The plurality of sets of the relay capacitors, the power supply side open/close elements, and the battery side open/close elements are not limited to two sets, but may be three or more sets which are different in switching-on/off period form one another. In this case, these settings include the power supply side open/close elements Ss#, which is in the closed condition during the off-period of the shopper control switching element Sc. This makes it possible to reduce a switching loss per unit time of the power supply side open/close elements Ss#.
In the third exemplary embodiment (see
In the synchronizing means of the controller 52 in the first exemplary embodiments (see
The electric power transmission device may further include a pre-charging circuit etc. In this case, the synchronizing means is not essential and may be omitted.
When an output current to the high-voltage battery 10 is allowed to be in a discontinuous manner, the energy storing inductor 24a may be omitted. When this output current is fully smoothed by, for example, the smoothing capacitor 24c, the energy storing inductor 24a may be also omitted. These conditions may be achieved by, for example, a configuration capable of reliably establishing electrical continuity between the smoothing filter 24 and either of the relay capacitors 26a, 26b in the second exemplary embodiment (see
The flow restriction element is not limited to the diode 24b of the smoothing filter 24, but may be, for example, a switching element for synchronous rectification, i.e., a switching element which is switched on in synchronization with a period during which the battery side open/close elements Sb# are opened.
The battery unit is not limited to the high-voltage battery 10 of storing electric energy of a rotary machine as on-vehicle main machinery, but may be, for example, a battery provided in a house.
The battery side filter 22 and the power supply side filter 32 is not essential and may be omitted.
The present disclosure may be embodied in several other forms without departing from the spirit thereof. The embodiments and modifications described so far are therefore intended to be only illustrative and not restrictive, since the scope of the disclosure is defined by the appended claims rather than by the description preceding them. All changes that fall within the metes and bounds of the claims, or equivalents of such metes and bounds, are therefore intended to be embraced by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-019467 | Feb 2012 | JP | national |
