JP5420080B2 - Power converter - Google Patents

Description

The present invention relates to a power conversion equipment for converting the DC power into DC power of a different voltage.

  In recent years, in addition to conventional vehicles that run only with conventional engines, electric vehicles such as hybrid vehicles that combine an engine and a motor generator and electric vehicles that run only with a motor have appeared, and the use of electric vehicles has been spreading. In the electric vehicle, in addition to the conventional low voltage battery, a high voltage battery is used to supply energy to the motor generator. Further, as vehicle electrical components, for example, there are high-voltage loads such as heaters and air-conditioning compressors, and low-voltage loads such as headlights and wipers, and the use voltages of various loads are lower than the use voltages of motors. For this reason, the voltage of the high voltage battery is stepped down by the DC / DC converter and supplied to the load.

Some step-down DC / DC converters as conventional power converters include transistors, diodes, and coils.
In another conventional example, a high-voltage side DC output having the same voltage as the output voltage of the DC power supply and a low-voltage side DC output having a voltage lower than the output voltage of the DC power supply can be supplied. A first DC power supply having the same output voltage as the DC output and a second DC power supply having an output voltage that is the difference between the high-voltage side DC output and the output voltage of the first DC power supply are connected in series. An output obtained by connecting the first and second DC power supplies in series is supplied as the high-voltage DC output, and the low-voltage DC output is connected to the output of the first DC power supply and the second DC power supply. The output that has been stepped down by the DC-DC converter is provided (for example, Patent Document 1).

JP 2001-136735 A (FIGS. 7 and 1)

In the above conventional power conversion device (step-down DC / DC converter), it is necessary to handle all load power connected to the subsequent stage because the step-down ratio is large because the high voltage battery steps down to a low voltage, and it is necessary to handle all load power connected to the subsequent stage. Had the problem of requiring large power capacity and increasing size.
Further, in a power conversion device (DC-DC conversion device) according to another example, the voltage lower by the output voltage of the first DC power supply may be stepped down from the DC power supply, but the load power connected to the first DC power supply is reduced. Accordingly, since the amount of power handled by the DC-DC converter increases, the reduction of the power capacity of the DC-DC converter is limited. In addition, since one of the first and second DC power supplies connected in series is used in a biased manner, there is a problem in that the reliability of the DC power supply is impaired.

The present invention has been made in order to solve the above-described problems. The power capacity of a power conversion device that steps down the battery voltage and supplies it to a plurality of loads while maintaining the reliability of the battery. It shall be the reduced intended to reduce the size of the power converter.

The power conversion device according to the present invention includes first and second capacitors connected in series so as to divide the battery voltage between both terminals of the battery, and first and second switching connected in series between the two terminals. elements, and, and the first, connection point and the first of the second capacitor, a first DC / DC converter with a connected inductor between the connection point of the second switching element, the second DC / DC converter that steps down the voltage of the second capacitor, the first, the first by mutual transfer of power between the second capacitor, the voltage of the second capacitor is desired partial pressure as the voltage, the first, second switching element drive control to a control circuit for controlling the first DC / DC converter, a first connected in parallel with said first capacitor The load on the first DC power of a capacitor is supplied, and DC power of the second capacitor is supplied to a second load connected to the output side of the second DC / DC converter, and the second DC / DC The desired divided voltage is adjusted so that the step-down ratio of the DC converter is reduced, and the control circuit controls the first DC / DC converter to change the voltage of the second capacitor to the second voltage. The step-down ratio of the DC / DC converter is changed so as to decrease.

The power converter according to the present invention includes a first and a second capacitor connected in series so as to divide the battery voltage between both terminals of the battery, and a first and a second capacitor connected in series between the terminals. A first DC / DC converter having a switching element and an inductor connected between a connection point of the first and second capacitors and a connection point of the first and second switching elements; The voltage of the second capacitor is stepped down, and the first DC / DC converter of the insulation type in which the input side and the output side are insulated from each other, and the first and second capacitors by the power transfer between the first and second capacitors. And a control circuit for controlling the first DC / DC converter by drivingly controlling the first and second switching elements so that the voltage of the second capacitor becomes a desired divided voltage. The first controller DC power of the first capacitor is supplied to a first load connected in parallel to the sensor, and DC of the second capacitor is supplied to a second load connected to the output side of the second DC / DC converter. It supplies power.
The power converter according to the present invention includes N capacitors connected in series so as to divide the battery voltage between both terminals of the battery, N switching elements connected in series between the two terminals, and A first DC / DC converter having (N-1) inductors connected between each connection point of N capacitors and each connection point of the N switching elements; and the N capacitors A control circuit for controlling the first DC / DC converter by drivingly controlling the N switching elements so that the voltages of the N capacitors become a desired divided voltage by exchanging electric power between them. And supplying each DC power of the N capacitors to each load, providing a predetermined voltage range as the desired divided voltage, and the control circuit including the N capacitors. When the voltage of the capacitor is outside the predetermined voltage range out that operating the first DC / DC converter.

According to the invention, is the power supplied to the loads of a plurality of capacitors that push divided battery voltage, the power converter is mutually shifts the DC power among multiple capacitors. For this reason, the actual voltage conversion ratio of the power converter is low, and the amount of power handled can be significantly reduced. For this reason, the power capacity of the power converter can be greatly reduced, and downsizing can be effectively achieved. In addition, the battery voltage is divided by multiple capacitors, but since the battery supplies power as a whole, it does not impair the reliability of the battery due to the biased power consumption as shown in the prior art, and is small and reliable. A highly in-vehicle power supply device can be obtained.

It is a figure which shows the structure of the vehicle-mounted power supply device by Embodiment 1 of this invention. It is operation | movement explanatory drawing of the DC / DC converter by Embodiment 1 of this invention. It is operation | movement explanatory drawing of the DC / DC converter by Embodiment 1 of this invention. It is operation | movement explanatory drawing of the DC / DC converter by Embodiment 1 of this invention. It is operation | movement explanatory drawing of the DC / DC converter by Embodiment 1 of this invention. It is a figure which shows the relationship between the battery voltage by Embodiment 2 of this invention, and the operating state of a DC / DC converter. It is a figure which shows the structure of the vehicle-mounted power supply device by Embodiment 3 of this invention. It is a figure which shows the example of the input / output voltage relationship of the DC / DC converter by Embodiment 3 of this invention. It is a figure which shows the relationship between the operating efficiency and voltage V1 of the 2nd DC / DC converter by Embodiment 4 of this invention. It is a figure which shows the relationship between the output electric power and voltage V1 of the 2nd DC / DC converter by Embodiment 5 of this invention. It is a figure which shows the structure of the vehicle-mounted power supply device by Embodiment 6 of this invention. It is a figure which shows the example of each voltage relationship at the time of the battery charge of the vehicle-mounted power supply device by Embodiment 6 of this invention. It is a figure which shows the structure of the vehicle-mounted power supply device by Embodiment 7 of this invention.

Embodiment 1 FIG.
Hereinafter, a power converter according to Embodiment 1 of the present invention and an in-vehicle power supply device including the power converter will be described with reference to the drawings.
1 is a configuration diagram of an in-vehicle power supply device according to Embodiment 1 of the present invention.
As shown in FIG. 1, the in-vehicle power supply device steps down the voltage of the high voltage battery 1 for driving the vehicle driving motor and the voltage of the battery 1 to supply power to the first load 10 a and the second load 10 b. Power conversion device 2 is provided.

The main circuit of the power conversion device 2 includes a DC / DC converter 2a as a first DC / DC converter. The DC / DC converter 2a includes first and second input terminals 1a and 1b connected in series. Connection point between first and second MOSFETs 3a and 3b as switching elements, first and second capacitors 5a and 5b connected in series so as to divide the battery voltage, and first and second MOSFETs 3a and 3b And an inductor 4 connected between connection points of the first and second capacitors 5a and 5b, and output terminals 7a, 7b and 7c. In the first and second MOSFETs 3a and 3b, diodes are connected in antiparallel, and parasitic diodes built into the elements may be used as the diodes.
The power conversion device 2 also includes a control circuit 6 that drives and controls the first and second MOSFETs 3a and 3b to control the output of the DC / DC converter 2a.

Next, the details of the connection configuration of the in-vehicle power supply device are shown below.
The battery 1 is connected between the input terminals 1a-1b. The input terminal 1a is connected to the source terminal of the first MOSFET 3a, one end of the first capacitor 5a, and the output terminal 7a. The input terminal 1b is connected to the drain terminal of the second MOSFET 3b and one end of the second capacitor 5b. Each is connected to the output terminal 7c. The drain terminal of the first MOSFET 3 a and the source terminal of the second MOSFET 3 b are connected to each other, and the connection point is connected to one end of the inductor 4. The other end of the inductor 4 is connected to the other end of the first capacitor 5a, the other end of the second capacitor 5b, and the output terminal 7b.

The terminal 6b of the control circuit 6 is connected to the input terminal 1b, and the terminal 6a is connected to the input terminal 1a. Further, the terminal 6cc of the control circuit 6 is connected to the output terminal 7c, the terminal 6bb is connected to the output terminal 7b, and the terminal 6aa is connected to the output terminal 7a. The terminal 6x is connected to the gate terminal of the first MOSFET 3a, and the terminal 6y is connected to the gate terminal of the second MOSFET 3b.
The output terminal 7a is connected to one end of the first load 10a, and the output terminal 7b is connected to the other end of the first load 10a and one end of the second load 10b. The output terminal 7c is connected to the other end of the second load 10b.

Next, the operation of the in-vehicle power supply device will be described below.
The DC / DC converter 2a steps down the input voltage VA from the battery 1 to generate voltages V1 and V2 of the first and second capacitors 5a and 5b, and applies them to the first load 10a and the second load 10b. Supply power.
The control circuit 6 acquires the potentials of the input / output terminals 1a, 1b, and 7a to 7c and inputs the voltage VA of the battery 1 as an input voltage and the voltages V1 of the first and second capacitors 5a and 5b as output voltages, V2 is detected, and based on these voltages, gate signals to the first and second MOSFETs 3a and 3b are output to drive and control the first and second MOSFETs 3a and 3b, and the DC / DC converter 2a is output. Control.
The DC / DC converter 2a is controlled so that the voltages V1 and V2 of the first and second capacitors 5a and 5b become desired voltages. Since the sum of the voltage V1 and the voltage V2 is always equal to VA, the other voltage can be controlled by controlling one voltage. In this case, the voltage V2 can also be controlled by controlling the voltage V1 to the target voltage.

When the voltage V1 is smaller than the target voltage, the first control shown in FIGS. 2 and 3 turns on and off the second MOSFET 3b and transfers energy from the second capacitor 5b to the first capacitor 5a. The voltage V1 of the first capacitor 5a is increased.
First, as shown in FIG. 2, when the first MOSFET 3a is turned off and the second MOSFET 3b is turned on, a current flows through a path of the second capacitor 5b-second MOSFET 3b-inductor 4, and the second capacitor The energy of 5b is transferred to the inductor 4. Next, as shown in FIG. 3, when the second MOSFET 3b is turned off, a current flows through the path of the inductor 4-the first capacitor 5a-the diode of the first MOSFET 3a, and the energy of the inductor 4 is changed to the first capacitor 5a. Migrate to
As described above, when the second MOSFET 3b is turned on and off and the states shown in FIGS. 2 and 3 are repeated, energy is transferred from the second capacitor 5b to the first capacitor 5a, and the voltage V1 is increased to control the target voltage. .

On the other hand, when the voltage V1 is larger than the target voltage, the second control shown in FIG. 4 and FIG. 5 causes the first MOSFET 3a to turn on and off to transfer energy from the first capacitor 5a to the second capacitor 5b. The voltage V1 of the first capacitor 5a is reduced.
First, as shown in FIG. 4, when the second MOSFET 3b is turned off and the first MOSFET 3a is turned on, a current flows through the path of the first capacitor 5a-inductor 4-first MOSFET 3a, and the first capacitor 3a is turned on. The energy of 5a is transferred to the inductor 4. Next, as shown in FIG. 5, when the first MOSFET 3a is turned off, a current flows through the path of the inductor 4-the diode of the second MOSFET 3b-the second capacitor 5b, and the energy of the inductor 4 is changed to the second capacitor 5b. Migrate to
As described above, when the first MOSFET 3a is turned on and off and the states shown in FIGS. 4 and 5 are repeated, energy is transferred from the first capacitor 5a to the second capacitor 5b, and the voltage V1 is lowered and controlled to the target voltage. .

  2 to 5 show examples in which rectification is performed by the diodes of the first and second MOSFETs 3a and 3b, but synchronous rectification in which on / off of the first and second MOSFETs 3a and 3b is synchronized with the timing of rectification by the diodes. Operation may be performed.

As described above, the DC / DC converter 2a operates so as to exchange power between the first and second capacitors 5a and 5b, and the voltage V1 is controlled to the target voltage. The target voltage is set so that the balanced state of the divided voltage shared by the first and second capacitors 5a and 5b is maintained, that is, the voltage V1 is in a constant stable state. It is determined according to the second load 10b. Desirably, the current flowing through the first load 10a and the current flowing through the second load 10b are determined to be equal. The control circuit 6 controls the DC / DC converter 2a so that the voltage V1 becomes the determined target voltage.
The target voltage of the voltage V1 may be calculated by the control circuit 6, but may be calculated by an external calculation device and given to the control circuit 6. Alternatively, the control circuit 6 may detect a stable state by changing the voltage V1 and control the voltage V1 as the target voltage.

  When the current flowing through the first load 10a and the current flowing through the second load 10b are equal, the balanced state of the divided voltages shared by the voltages V1 and V2 of the first and second capacitors 5a and 5b is maintained. If the voltage V1 is the target voltage in this equilibrium state, the DC / DC converter 2a can output desired voltages V1 and V2 in the stopped state to supply power to the first and second loads 10a and 10b. Further, when the voltages V1 and V2 of the first and second capacitors 5a and 5b hold the balanced state, it is said that the electric power of the first load 10a and the second load 10b is in the balanced state.

  When the equilibrium state as described above is lost and the current flowing through the first load 10a becomes larger than the current flowing through the second load 10b, the voltage V1 decreases and the voltage V2 increases. In that case, energy is transferred from the second capacitor 5b to the first capacitor 5a by the first control, and the voltage V1 is controlled. When the current flowing through the first load 10a is smaller than the current flowing through the second load 10b, the voltage V1 increases and the voltage V2 decreases. In that case, energy is transferred from the first capacitor 5a to the second capacitor 5b by the second control, and the voltage V1 is controlled.

As described above, the DC / DC converter 2a can control the output voltages V1 and V2 (= VA−V1) to a constant target voltage. In the DC / DC converter 2a, the input voltage VA from the battery 1 is stepped down to generate the output voltages V1 and V2. The power conversion operation is performed by energy transfer between the second capacitor 5b and the first capacitor 5a. The actual voltage conversion ratio is V1 / V2 or V2 / V1, which can be significantly reduced. Further, the power capacity handled by the DC / DC converter 2a is only a power difference based on the current difference between the first load 10a and the second load 10b, so that the power capacity can be greatly reduced, and the DC / DC converter 2a can be downsized. be able to.
Further, the voltage VA of the battery 1 is divided by the first and second capacitors 5a and 5b. However, since the battery 1 supplies power as a whole, the battery 1 has a biased power consumption as shown in the prior art. There is no loss of reliability. For this reason, a small and highly reliable on-vehicle power supply device can be obtained by using the small DC / DC converter 2a and the highly reliable battery 1.

In the first embodiment, description has been made using MOSFETs as the first and second switching elements 3a and 3b. However, a bipolar transistor, an insulated bipolar transistor (IGBT), a silicon carbide transistor, or a wide transistor is described. The same effect can be obtained by using a MOSFET formed of a band gap semiconductor.
A wide band gap semiconductor is a semiconductor having a larger band gap than silicon, for example, silicon carbide, gallium nitride-based material, or diamond. Since the switching element formed of such a wide band gap semiconductor has high voltage resistance and high allowable current density, the switching element can be reduced in size. By using these reduced switching elements, Miniaturization of the DC / DC converter 2a and the in-vehicle power supply device can be promoted. Furthermore, since the power loss is low, the efficiency of the switching element can be increased, and the efficiency of the DC / DC converter 2a and the in-vehicle power supply device can be increased.
In addition, since switching elements made of wide band gap semiconductors have high heat resistance, it is usually possible to reduce the size of the heat sink fins of the heat sink provided in the in-vehicle power supply device and to cool the water cooling part. Further downsizing becomes possible.

  Each of the first and second switching elements 3a and 3b may be configured by connecting a plurality of switching elements in series. Each of the first and second capacitors 5a and 5b may be configured by connecting a plurality of capacitors in series or in parallel.

Embodiment 2. FIG.
In the second embodiment, an in-vehicle power supply device having a circuit configuration similar to that of the first embodiment is used, and power is exchanged between the first and second capacitors 5a and 5b, similarly to the first embodiment. The DC / DC converter 2a operates to control the voltage V1. In this case, a predetermined voltage range is provided as the target voltage of the voltage V1. When the balanced state of the first load 10a and the second load 10b is lost, as shown in FIG. 6, when the value of the voltage V1 is in the range of V1a to V1b, the DC / DC converter 2a operates. Stop. When the value of the voltage V1 is smaller than V1a or larger than V1b, as shown in the first embodiment, the DC / DC is exchanged between the first and second capacitors 5a and 5b. The converter 2a operates to control the value of the voltage V1 so that it falls within the range of V1a to V1b.
In this embodiment, the same effects as those of the first embodiment can be obtained, and the DC / DC converter 2a can further reduce the amount of electric power to be handled and can further promote downsizing, and an in-vehicle vehicle using the DC / DC converter 2a. The power supply device can be similarly reduced in size.

Embodiment 3 FIG.
Next, a power converter according to Embodiment 3 of the present invention and an in-vehicle power supply device including the power converter will be described with reference to the drawings.
FIG. 7 is a configuration diagram of an in-vehicle power supply device according to Embodiment 3 of the present invention.
As shown in FIG. 7, the in-vehicle power supply device steps down the voltage of the high voltage battery 1 for driving a vehicle driving motor and the voltage of the battery 1 to supply power to the first load 10 a and the second load 10 b. Power converter 20 and a low-voltage second battery 9 for the second load 10b.
The main circuit of the power conversion device 20 includes a DC / DC converter 2 a and a second DC / DC converter 8. The DC / DC converter 2a is the same as that of the first embodiment, and the second DC / DC converter 8 includes input terminals 8a and 8b and output terminals 8c and 8d, and the input side is connected to the second capacitor 5b. Connected in parallel. The second DC / DC converter 8 is an insulation type DC / DC converter in which the input terminals 8a and 8b and the output terminals 8c and 8d are insulated, and has a transformer, for example.

  Similarly to the first embodiment, the power conversion device 20 includes a control circuit 6 that drives and controls the first and second MOSFETs 3a and 3b to control the output of the DC / DC converter 2a. And the second DC / DC converter 8 is controlled. This second control circuit may be shared by the control circuit 6.

Next, differences from the first embodiment in the connection configuration of the in-vehicle power supply device will be described below.
The output terminal 7a of the DC / DC converter 2a is connected to one end of the first load 10a, and the output terminal 7b is connected to the other end of the first load 10a and the input terminal 8a of the second DC / DC converter 8, respectively. The output terminal 7 c is connected to the input terminal 8 b of the second DC / DC converter 8. The output terminal 8d of the second DC / DC converter 8 is connected to the positive electrode side of the second battery 9 and one end of the second load 10b. The output terminal 8c of the second DC / DC converter 8 is connected to the negative electrode side of the second battery 9 and the other end of the second load 10b.

Next, the operation of the in-vehicle power supply device will be described below.
The DC / DC converter 2a steps down the input voltage VA from the battery 1 to generate voltages V1 and V2 of the first and second capacitors 5a and 5b, and supplies the first load 10a with the voltage V1. . The second DC / DC converter 8 steps down the voltage V2 of the second capacitor 5b to charge the second battery 9, and supplies power to the second load 10b with the voltage V2.

FIG. 8 is an example showing the relationship between the input voltage VA and the output voltages V1 and V2 of the DC / DC converter 2a.
Suppose that the first load 10a operates within a voltage range of 200V to 400V, that is, the voltage range of the voltage V1 is 200V to 400V. When the voltage VA = 320V, the voltage V1 = 200V and the voltage V2 = 120V. When VA = 600V, the voltage V1 = 400V and the voltage V2 = 200V.
When the voltage VA satisfies the relationship of the linear functions with the voltage V1 and the voltage V2, respectively, the range of the voltage V2 that is the input voltage range of the second DC / DC converter 8 is as small as 120V to 200V. The input / output voltage conversion ratio of the DC / DC converter 8 can be reduced. When the input / output voltage conversion ratio of the second DC / DC converter 8 is thus reduced, the second DC / DC converter 8 operates with high efficiency.

The control and operation of the DC / DC converter 2a is the same as in the first embodiment, and the DC / DC converter 2a operates so as to exchange power between the first and second capacitors 5a and 5b, and the voltage V1 is Controlled to target voltage. For this reason, the DC / DC converter 2a can handle only the power difference between the first load 10a and the second load 10b, as in the first embodiment, and can greatly reduce the power capacity. Converter 2a can be reduced in size.
Therefore, a small and high-efficiency power conversion device 20 using the small DC / DC converter 2a and the high-efficiency second DC / DC converter 8 and an in-vehicle power supply device using the same can be obtained.

  Further, in this embodiment, since the second DC / DC converter 8 is constituted by an insulated DC / DC converter, it is possible to generate a high voltage at the output terminals 8c and 8d even if the high-voltage side voltage V2 is used as the input voltage. Absent. Alternatively, the first load 10a may be connected to the high-voltage side voltage V2, and the second DC / DC converter 8 may be connected to the low-voltage side to use the voltage V1 as an input voltage. In this case, the second DC / DC The converter 8 may be a non-insulated DC / DC converter, and the same effect can be obtained.

  In the third embodiment, the case where the voltage VA satisfies the relationship of the linear function with the voltage V1 and the voltage V2, respectively, has been described, but the constant values of the voltage V1 and the voltage V2 according to the increase of the voltage VA. The same effect can be obtained if there are sections or increasing sections.

Embodiment 4 FIG.
In the fourth embodiment, an in-vehicle power supply device having a circuit configuration similar to that of the third embodiment is used, and power is exchanged between the first and second capacitors 5a and 5b, similarly to the third embodiment. When the DC / DC converter 2a operates to control the voltage V1, the voltages V1 and V2 of the first and second capacitors 5a and 5b are generated, and the second DC / DC converter 8 generates the second capacitor 5b. The voltage V2 is reduced.
In this embodiment, the target voltage of the voltage V 1 is changed depending on the operation efficiency of the second DC / DC converter 8. FIG. 9 is a diagram showing the relationship between the voltage V1 and the operating efficiency of the second DC / DC converter. As shown in the figure, when the operating efficiency of the second DC / DC converter is low, the voltage V1 is increased. Specifically, control is performed such that the target voltage of the voltage V1 is increased and the voltage V1 is increased by the DC / DC converter 2a. As a result, the input voltage V2 of the second DC / DC converter 8 is lowered, the input / output conversion ratio can be reduced, and high efficiency can be achieved.

  Thus, by adjusting the target voltage of the voltage V1 so as to reduce the input / output voltage conversion ratio of the second DC / DC converter 8, the operating efficiency of the second DC / DC converter 8 can be improved. A highly efficient second DC / DC converter 8 is obtained. In addition, a small and more efficient power conversion device 20 and an in-vehicle power supply device using the same can be realized.

  In the above-described fourth embodiment, the case where the operation efficiency of the second DC / DC converter 8 and the voltage V1 satisfy the relationship of the linear function is illustrated and described. However, the second DC / DC converter 8 is illustrated. The same effect can be obtained if the voltage V1 tends to decrease with respect to the operating efficiency of the above.

Embodiment 5 FIG.
In the fifth embodiment, an in-vehicle power supply device having a circuit configuration similar to that of the third embodiment is used, and power is exchanged between the first and second capacitors 5a and 5b as in the third embodiment. When the DC / DC converter 2a operates to control the voltage V1, the voltages V1 and V2 of the first and second capacitors 5a and 5b are generated, and the second DC / DC converter 8 generates the second capacitor 5b. The voltage V2 is reduced.
In this embodiment, the output power of the second DC / DC converter 8 is controlled so that the power of the first load 10a and the second load 10b is balanced. FIG. 10 is a diagram showing the relationship between the output power of the second DC / DC converter 8 and the voltage V1. As shown in FIG. 10, by changing the output power of the second DC / DC converter 8 according to the voltage V1, the power of the first load 10a and the second load 10b can be balanced.
As described above, since the DC / DC converter 2a handles the power difference between the first and second loads 10a and 10b, the power of the first load 10a and the second load 10b is balanced. By controlling the output power of the second DC / DC converter 8, the amount of power handled by the DC / DC converter 2a can be extremely low. For this reason, size reduction of the DC / DC converter 2a can be further promoted, and a further compact power conversion device and in-vehicle power supply device can be obtained.

  In the fifth embodiment, the output power of the second DC / DC converter 8 and the voltage V1 satisfy the relationship of the linear function is illustrated and described. The same effect can be obtained if the output power of the DC / DC converter 8 tends to decrease.

Embodiment 6 FIG.
Next, a power converter according to Embodiment 6 of the present invention and an in-vehicle power supply device including the power converter will be described with reference to the drawings.
FIG. 11 is a block diagram of an in-vehicle power supply device according to Embodiment 6 of the present invention.
As shown in FIG. 11, the in-vehicle power supply device includes a high-voltage battery 1 connected to a motor generator M / G of a vehicle via an inverter, a first load 10a and a second load by stepping down the voltage of the battery 1. A power converter 200 having a function of supplying power to the load 10b and charging the battery 1 from the AC power source 12 is provided. The main circuit of the power conversion device 200 includes a DC / DC converter 2 a and an AC / DC converter 11. The DC / DC converter 2a is the same as that of the first embodiment, and the AC / DC converter 11 includes output terminals 11a and 11b and input terminals 11c and 11d, and the output side is connected to the first capacitor 5a. When charging 1, the input side is connected to the AC power source 12.

  Similarly to the first embodiment, the power conversion device 200 includes a control circuit 6 that drives and controls the first and second MOSFETs 3a and 3b to control the output of the DC / DC converter 2a. And the AC / DC converter 11 is controlled. Further, current detection means 15 is arranged so as to detect the current flowing through the inductor 4. In this case, the control circuit 6 performs two types of control, that is, the control described in the first embodiment and the control in the charging mode when the battery 1 is charged. The third control circuit may perform only the control when charging the battery 1 and may be shared by the control circuit 6.

Next, differences from the first embodiment in the connection configuration of the in-vehicle power supply device will be described below.
A terminal 6 s of the control circuit 6 is connected to the current detection means 15. The output terminal 7 a of the DC / DC converter 2 a is connected to one end of the first load 10 a and the output terminal 11 a of the AC / DC converter 11. The output terminal 7b is connected to the other end of the first load 10a, one end of the second load 10b, and the output terminal 11b of the AC / DC converter 11, respectively. The output terminal 7c is connected to the other end of the second load 10b. An AC power supply 12 is connected between the input terminals 11c-11d of the AC / DC converter 11. In the first embodiment as well, the battery 1 is connected to a motor generator (motor) via an inverter, but is not shown for convenience.

Next, the operation of the in-vehicle power supply device will be described below.
In the power conversion device 200, when the voltage of the battery 1 is stepped down to supply power to the first load 10a and the second load 10b, the DC / DC converter 2a operates in the same manner as in the first embodiment. Here, the operation | movement which charges the battery 1 via the power converter device 200 from the alternating current power supply 12 is demonstrated below.
AC power from the AC power supply 12 is converted into DC power by the AC / DC converter 11 and output to the first capacitor 5a. In the DC / DC converter 2a, the first MOSFET 3a is turned on / off to charge the battery 1 with the voltage VA. At this time, the control circuit 6 controls the DC / DC converter 2a so that the current flowing through the inductor 4 becomes a predetermined current.

FIG. 12 shows an example of the relationship between the voltages V1 and V2 of the first and second capacitors 5a and 5b, which are input / output voltages of the DC / DC converter 2a, and the voltage VA of the battery 1.
For example, the condition where the AC / DC converter 11 has the highest power conversion efficiency is assumed to be operated under the condition where the DC voltage, that is, the output voltage, the voltage V1 is 370V. In the example of FIG. 12, when the voltage VA of the battery 1 is 320V, the voltage V1 = 310V and the voltage V2 = 10V, and when the voltage VA = 380V, the voltage V1 = 370V and the voltage V2 = 10V, and the voltage VA is 320V to 380V. In this region, the voltage VA satisfies a relationship of linear functions with the voltages V1 and V2, respectively. Further, when the voltage VA of the battery 1 is 600V, the voltage V1 = 370V and the voltage V2 = 230V, and the voltage VA satisfies the relationship of the linear functions with the voltages V1 and V2 even in the region where the voltage VA is 380V to 600V. .
When the DC / DC converter 2a and the AC / DC converter 11 are operated under such conditions, in the region where the voltage VA is 320V to 380V, the input / output voltage conversion ratio in the DC / DC converter 2a becomes a value close to 1, The DC / DC converter 2a operates with high efficiency. In the region where the voltage VA is 380V to 600V, the AC / DC converter 11 operates with the highest efficiency.

  In this way, the AC / DC converter 11 controls the voltage V1 to a voltage that is a highly efficient optimum operating point for a long time, and further, according to the voltage VA of the battery 1, the input / output of the DC / DC converter 2a. The voltage V1 is controlled so that the voltage conversion ratio becomes a value close to 1. Thereby, the DC / DC converter 2a which comprises the power converter device 200, and the AC / DC converter 11 operate | move with a low loss, and the power converter device with high conversion efficiency is obtained.

  In this embodiment, the case where the on-vehicle power supply device of the first embodiment is modified so as to be applicable to charging is shown. However, any of the on-vehicle power supply devices of the above-described second to fifth embodiments is an AC / DC converter. The battery 1 can be similarly charged by using the power conversion device provided with 11, and the same effect can be obtained.

  Further, in the sixth embodiment, the voltage VA has been described so as to satisfy the relationship between the voltages V1 and V2 and the linear function, respectively. If there is, the same effect can be obtained.

  In the sixth embodiment, the AC / DC converter 11 is unidirectionally described for charging the battery 1 from the AC power supply 12, but the AC / DC converter 11 has a bidirectional power conversion function. May be. In this case, the AC / DC converter 11 can convert the DC power of the first capacitor 5a into AC power and output it to the AC power supply 12. Therefore, the battery 1 passes through the first capacitor 5a and the AC / DC converter 11. Thus, power can be supplied to the AC power source 12.

Embodiment 7 FIG.
Next, a power converter according to Embodiment 7 of the present invention and an in-vehicle power supply device including the power converter will be described with reference to the drawings.
In the first to sixth embodiments, the DC / DC converter 2a including the two capacitors 5a and 5b connected in series to the two switching elements 3a and 3b connected in series and the one inductor 4 is the first. Although used as a DC / DC converter, the number of switching elements and capacitors in the first DC / DC converter may be three or more. In this embodiment, the case of three will be described below.

FIG. 13 is a block diagram of an in-vehicle power supply device according to Embodiment 7 of the present invention.
As shown in FIG. 13, the in-vehicle power supply device includes a high-voltage battery 1 for driving a vehicle driving motor, and a first load 10 a, a second load 10 b, and a third load by stepping down the voltage of the battery 1. The power converter 30 for supplying electric power to 10c is provided.
The main circuit of the power conversion device 30 includes a DC / DC converter 30a serving as a first DC / DC converter. The DC / DC converter 30a includes input terminals 1a and 1b and three switching elements connected in series. First, second, and third MOSFETs 3a, 3b, and 3c, first, second, and third capacitors 5a, 5b, and 5c connected in series so as to divide the battery voltage, and two inductors 4a 4b and output terminals 7a to 7d. The inductor 4a is connected between the connection point of the first and second MOSFETs 3a and 3b and the connection point of the first and second capacitors 5a and 5b. The inductor 4b is connected to the second and third MOSFETs 3b and 3c. And the connection point of the second and third capacitors 5b and 5c. The first, second, and third MOSFETs 3a, 3b, and 3c have diodes connected in antiparallel, but the diodes may be parasitic diodes built in the elements.
The power conversion device 30 includes a control circuit 6 that drives and controls the first, second, and third MOSFETs 3a, 3b, and 3c to control the output of the DC / DC converter 30a.

Next, the details of the connection configuration of the in-vehicle power supply device are shown below.
The battery 1 is connected between the input terminals 1a-1b. The input terminal 1a is connected to the source terminal of the first MOSFET 3a, one end of the first capacitor 5a, and the output terminal 7a. The input terminal 1b is connected to the drain terminal of the third MOSFET 3c and one end of the third capacitor 5c. Each is connected to an output terminal 7d. The drain terminal of the first MOSFET 3a and the source terminal of the second MOSFET 3b are connected to each other, and the connection point is connected to one end of the inductor 4a. The other end of the inductor 4a is connected to the other end of the first capacitor 5a, the other end of the second capacitor 5b, and the output terminal 7b. The drain terminal of the second MOSFET 3b and the source terminal of the third MOSFET 3c are connected to each other, and the connection point is connected to one end of the inductor 4b. The other end of the inductor 4b is connected to the other end of the second capacitor 5b, the other end of the third capacitor 5c, and the output terminal 7c.

The terminal 6b of the control circuit 6 is connected to the input terminal 1b, and the terminal 6a is connected to the input terminal 1a. Further, the terminal 6dd of the control circuit 6 is connected to the output terminal 7d, the terminal 6cc is connected to the output terminal 7c, the terminal 6bb is connected to the output terminal 7b, and the terminal 6aa is connected to the output terminal 7a. The terminal 6x is connected to the gate terminal of the first MOSFET 3a, the terminal 6y is connected to the gate terminal of the second MOSFET 3b, and the terminal 6z is connected to the gate terminal of the third MOSFET 3c.
The output terminal 7a is connected to one end of the first load 10a, and the output terminal 7b is connected to the other end of the first load 10a and one end of the second load 10b. The output terminal 7c is connected to the other end of the second load 10b and one end of the third load 10c, and the output terminal 7d is connected to the other end of the third load 10c.

Next, the operation of the in-vehicle power supply device will be described below.
The DC / DC converter 30a steps down the input voltage VA from the battery 1 to generate voltages V1, V2, and V3 of the first, second, and third capacitors 5a, 5b, and 5c, and the first load 10a. The power is supplied to the second load 10b and the third load 10c.
The control circuit 6 acquires the potentials of the input terminals 1a, 1b, and 7a to 7d and inputs the voltage VA of the battery 1 as an input voltage and the first, second, and third capacitors 5a, 5b, and 5c as output voltages. Voltage V1, V2, and V3 are detected, and based on these voltages, the gate signals to the first, second, and third MOSFETs 3a, 3b, and 3c are output to output the first, second, and third MOSFETs 3a. 3b and 3c are driven and the output of the DC / DC converter 30a is controlled.

The DC / DC converter 30a is controlled so that the voltages V1, V2, and V3 of the first, second, and third capacitors 5a, 5b, and 5c become desired voltages. Since the sum of the voltage V1, the voltage V2, and the voltage V3 is always equal to the voltage VA, the remaining voltage can be controlled by controlling any two voltages. For example, the voltage V3 can also be controlled by controlling the voltage V1 and the voltage V2 to the respective target voltages.
Also in the seventh embodiment, as in the first embodiment, the DC / DC converter 30a operates so as to transfer power between the first to third capacitors 5a to 5c, and the voltages V1 to V3 are Controlled to target voltage. The target voltage is determined according to the first to third loads 10a to 10c so that the balanced state of the divided voltages shared by the first to third capacitors 5a to 5c is maintained. Desirably, it determines so that the electric current which flows through each load 10a-10c may become equal. The control circuit 6 controls the DC / DC converter 2a so that the voltages V1 to V3 become the determined target voltages.

As described above, the DC / DC converter 30a steps down the input voltage VA from the battery 1 to generate the output voltages V1, V2, and V3. However, the power is transferred by energy transfer between the first to third capacitors 5a to 5c. Conversion operation is being performed. For this reason, as in the first embodiment, the DC / DC converter 30a can remarkably reduce the actual voltage conversion ratio, greatly reduce the amount of power to be handled, and can reduce the size of the DC / DC converter 30a. .
Further, since the battery 1 supplies power as a whole, the reliability of the battery 1 is not impaired due to uneven power consumption, and the battery 1 is used together with the small DC / DC converter 30a. Can be obtained.

  Note that the number of switching elements and capacitors in the first DC / DC converter is not limited to 2 or 3, and when N is an integer of 2 or more, the first DC / DC converter has N connected in series. Capacitors, N switching elements connected in series, and (N-1) inductors connected between the connection points of the N capacitors and the connection points of the N switching elements. The same effects as described above can be obtained.

Claims (9)

First and second capacitors connected in series so as to divide the battery voltage between both terminals of the battery, first and second switching elements connected in series between the two terminals, and the first, attachment point and the first of the second capacitor, a first DC / DC converter with a connected inductor between the connection point of the second switching element,
A second DC / DC converter for stepping down the voltage of the second capacitor;
The first and second switching elements are driven and controlled so that the voltages of the first and second capacitors become a desired divided voltage by mutual power transfer between the first and second capacitors. and a control circuit for controlling the first DC / DC converter Te,
DC power of the first capacitor is supplied to a first load connected in parallel to the first capacitor, and the second load is connected to the second load connected to the output side of the second DC / DC converter. The DC power of the capacitor of
The desired divided voltage is adjusted so that the step-down ratio of the second DC / DC converter is lowered, and the control circuit controls the first DC / DC converter to control the voltage of the second capacitor. Is changed so that the step-down ratio of the second DC / DC converter is lowered . 2. The power converter according to claim 1, wherein the control circuit controls output power of the second DC / DC converter so that powers of the first and second loads are balanced. 3. The power converter according to claim 1 , wherein the second DC / DC converter is an isolated DC / DC converter in which an input side and an output side are insulated. First and second capacitors connected in series so as to divide the battery voltage between both terminals of the battery, first and second switching elements connected in series between the two terminals, and the first, A first DC / DC converter having an inductor connected between a connection point of a second capacitor and a connection point of the first and second switching elements;
An insulation type second DC / DC converter in which the voltage of the second capacitor is stepped down and the input side and the output side are insulated ;
The first and second switching elements are driven and controlled so that the voltages of the first and second capacitors become a desired divided voltage by mutual power transfer between the first and second capacitors. And a control circuit for controlling the first DC / DC converter,
DC power of the first capacitor is supplied to a first load connected in parallel to the first capacitor, and the second load is connected to the second load connected to the output side of the second DC / DC converter. A power converter that supplies direct current power of a capacitor . N capacitors connected in series so as to divide the battery voltage between both terminals of the battery, N switching elements connected in series between the two terminals, and connection points of the N capacitors A first DC / DC converter having (N-1) inductors connected between the connection points of the N switching elements;
The first DC / DC converter is controlled by driving the N switching elements so that the N capacitors have a desired divided voltage by transmitting and receiving power between the N capacitors. And a control circuit for controlling the
Supplying each DC power of the N capacitors to each load,
A predetermined voltage range is provided as the desired divided voltage,
The control circuit, the power converter the voltage of the N capacitors, characterized in that to operate the outside when the first DC / DC converter the predetermined voltage range. 6. The power converter according to claim 5 , wherein the desired divided voltage is determined according to each of the loads so that an equilibrium state is maintained at the divided voltage. The N capacitors are two capacitors, a first capacitor and a second capacitor, and the N switching elements are two switching elements, a first switching element and a second switching element, and each of the loads Is the first and second loads,
A second DC / DC converter for stepping down the voltage of the second capacitor; wherein the first load is connected in parallel to the first capacitor; and the second load is the second DC / DC converter. The power conversion device according to claim 5 , wherein the power conversion device is connected to an output side of the power conversion device. 7. The power converter according to claim 5, wherein the loads are connected in parallel to the N capacitors. According to any one of claims 1 to 8, characterized in that the band gap than on Kiss switching element silicon of the inner first DC / DC converter is formed by a wide wide band gap semiconductor Power converter.

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