JP2018148724A - DC voltage converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC voltage converter capable of maintaining a high conversion efficiency when adapting to a large-capacity load.SOLUTION: A DC voltage converter 10 comprises an auxiliary resonance circuit 20 which includes a first switch element SW1 connected to an inner power source line Ls, a low-pass filter 13, an auxiliary switch element SA serially connected, and an auxiliary reactor LA, and is connected to a first connection point N1 as a connection point of the first switch element SW1 and the low-pass filter 13. The DC voltage converter 10 further comprises: an auxiliary voltage apply part 12 that is electrically connected to the auxiliary resonance circuit 20 and a ground line Lg, and applies an auxiliary voltage VA of a constant voltage lower than a voltage value of an input voltage Vin to an auxiliary reactor LA through the auxiliary switch element SA; and a switch control part 11 that switches the first switch element SW1 with a zero voltage, and switches the auxiliary switch element SA with a zero-current.SELECTED DRAWING: Figure 1

Description

  The technology disclosed in the present specification relates to a DC voltage converter, and more particularly, to a DC voltage converter provided with an auxiliary resonance circuit.

  2. Description of the Related Art Conventionally, in order to suppress switching loss and high frequency noise due to switching by so-called soft switching of a switching element, a method of providing an auxiliary resonant circuit in a DC voltage converter has been widely performed. As a DC voltage converter provided with such an auxiliary resonance circuit, for example, a DC-DC converter (DC voltage converter) disclosed in Patent Document 1 is known. In the DC-DC converter of this document, by optimizing the period in which the second main switch (low-side switch) and the auxiliary switch included in the auxiliary resonance circuit are simultaneously turned on based on the current flowing through the smoothing reactor, This prevents the generation of useless power loss.

JP 2004-129393 A

  However, in the DC-DC converter of the above document, the energy source of the auxiliary resonance circuit, that is, the power source is the output voltage Vout. Since the output voltage Vout is obtained by converting the input voltage Vin, the loss in the auxiliary resonance circuit is also added as a conversion loss. This was not advantageous for improving the efficiency of the converter. Further, in the configuration in which the output voltage Vout is applied to the auxiliary resonance circuit in this way, when the input voltage Vin is converted to the very low output voltage Vout, even if the output voltage Vout is applied to the auxiliary resonance circuit, The voltage at point M in FIG. 1 does not reach the input voltage Vin, and there is a possibility that soft switching (zero voltage switching) of the first main switch S1 cannot be performed. In this case, the switching loss in the first main switch S1 increases.

  Also, in recent years, when a DC voltage converter is used as a power circuit that requires a large current, such as an electric vehicle, in other words, when used for a large capacity load, a small reduction in conversion efficiency causes a large conversion loss. End up. Therefore, a DC voltage converter that can maintain high conversion efficiency even when applied to a large-capacity load has been desired.

  The technology disclosed in the present specification has been completed based on the above-described circumstances, and provides a DC voltage converter capable of maintaining high conversion efficiency when applied to a large-capacity load. To do.

A DC voltage converter disclosed in the present specification is a DC voltage converter that converts a DC input voltage applied from a main power source into an output voltage having a predetermined voltage value, and is connected to the main power source. An internal power line, a first switch element connected to the internal power line, a low-pass filter having one end connected to one end of the first switch element, an auxiliary switch element and an auxiliary reactor connected in series, One end of the auxiliary reactor is electrically connected to an auxiliary resonance circuit connected to a first connection point that is a connection point between the first switch element and the low-pass filter, and to the auxiliary resonance circuit and a ground line, and the input An auxiliary voltage applying unit that applies an auxiliary voltage having a constant voltage lower than a voltage value to the auxiliary reactor via the auxiliary switch element; the first connection point; and the ground line. Comprising a reflux portion connected between the first switching element and zero-voltage switching, and a switch control unit which zero current switching the auxiliary switching element.
According to this configuration, the auxiliary voltage application unit that supplies power to the auxiliary resonance circuit is provided. Therefore, a loss caused by the auxiliary resonance circuit, for example, a switching loss caused by the auxiliary switch element is not added to the switching loss of the first switch element when the input voltage is converted into the output voltage. The first switch element is zero-voltage switched and the auxiliary switch element is zero-current switched. Therefore, according to the direct-current voltage converter of this configuration, high conversion efficiency can be maintained even when applied to a large-capacity load.

In the DC voltage converter, the reflux unit may be configured by a second switch element that is zero-voltage switched by the switch control unit.
According to this configuration, the return period can be appropriately set by on / off control of the second switch element, and the switching loss of the second switch element can be suppressed by zero voltage switching.

The DC voltage converter may further include a first parallel capacitor connected in parallel to the first switch element and a second parallel capacitor connected in parallel to the reflux unit.
According to this configuration, when the first switch element is turned off, the speed of the potential change at the first connection point in the so-called dead time can be adjusted.

The DC voltage converter may further include a first diode connected between a second connection point that is a connection point between the auxiliary reactor and the auxiliary switch element, and the ground line.
According to this configuration, the first diode can stabilize the potential at the second connection point during the off-period of the auxiliary switch element. That is, when the auxiliary switch element is off and the second switch element is on, when the MOSFET is used as the auxiliary switch element, the potential at the second connection point varies via the parasitic capacitance of the auxiliary switch element. Can be considered. In that case, the fluctuation | variation of the electric potential of a 2nd connection point is suppressed by the 1st diode.

In the DC voltage converter, the auxiliary switch element may be configured by two auxiliary switch elements connected in series that are simultaneously controlled by the switch control unit.
According to this configuration, by configuring the auxiliary switch element with two auxiliary switch elements connected in series, the on-resistance as the auxiliary switch element increases. Accordingly, the on-state current flowing when the auxiliary switch element is turned on is reduced, so that the on-resistance loss of the auxiliary switch element is reduced as compared with the case where there is only one auxiliary switch element. Since the loss (power) is proportional to the square of the current, in this case, the amount of decrease in the on-resistance loss due to the decrease in the on-current is greater than the amount of increase in the on-resistance loss that accompanies the increase in on-resistance. Therefore, on-resistance loss is reduced.

The DC voltage converter may further include a second diode connected between a third connection point that is an intermediate connection point of the two auxiliary switch elements and the power supply line.
According to this configuration, the second diode can stabilize the potential at the third connection point in a period in which one auxiliary switch element close to the auxiliary voltage application unit is off. That is, when one auxiliary switch element is off and the other auxiliary switch element and the second switch element are on, when a MOSFET is used as one auxiliary switch element, the parasitic capacitance of one auxiliary switch element is reduced. Therefore, it is conceivable that the potential at the third connection point varies. In that case, the fluctuation | variation of the electric potential of a 3rd connection point is suppressed by the 2nd diode.

Further, in the DC voltage converter, the main power source is composed of a battery composed of a plurality of cells, and the auxiliary voltage application unit includes an external connection terminal connected to an intermediate potential part of the battery, and the external connection terminal You may make it comprise with the voltage application line which connects the said auxiliary | assistant switch element.
According to this configuration, the auxiliary voltage application unit can be formed with a simple configuration without providing an auxiliary power source such as a battery in the apparatus.

In the DC voltage converter, the auxiliary voltage may have a voltage value that is half or more of the input voltage.
According to this configuration, each switch element can be soft-switched reliably by setting the voltage value of the auxiliary voltage to be equal to or lower than the input voltage and equal to or higher than half the input voltage.

  According to the DC voltage conversion device disclosed in the present specification, high conversion efficiency can be maintained when applied to a large capacity load.

1 is a schematic circuit diagram illustrating a DC voltage converter according to a first embodiment. Schematic time chart showing the operation of the DC voltage converter Schematic partial circuit diagram showing the current flow of the DC voltage converter Schematic partial circuit diagram showing the current flow of the DC voltage converter Schematic partial circuit diagram showing the current flow of the DC voltage converter Schematic partial circuit diagram showing the current flow of the DC voltage converter Schematic partial circuit diagram showing the current flow of the DC voltage converter Schematic partial circuit diagram showing the current flow of the DC voltage converter Schematic partial circuit diagram showing the current flow of the DC voltage converter The partial circuit diagram which shows the auxiliary voltage application part which concerns on Embodiment 2. Schematic time chart showing the operation when the DC voltage converter is applied to the boost converter

<Embodiment 1>
A DC voltage converter 10 according to a first embodiment will be described with reference to FIGS. 1 to 9.
1. Configuration of DC Voltage Converter In this embodiment, the DC voltage converter 10 is a so-called chopper type step-down DC-DC converter, which steps down a DC input voltage Vin applied from a battery as a main power supply 40, and It is converted into a DC output voltage Vout having a predetermined voltage value. The input voltage Vin is 48V, for example, and the output voltage Vout is 24V, for example.

  The DC voltage converter 10 is applied to the present embodiment, for example, an HV vehicle on which a gasoline engine and a travel motor are mounted, and is applied to a power circuit that supplies power to a large-capacity load 50 such as a travel motor. The Note that the application of the DC voltage converter 10 is not limited to HV vehicles, and is not limited to vehicles. Further, the load to which the DC voltage converter 10 is applied is not necessarily limited to a large capacity load. Furthermore, the present invention is not limited to a step-down DC-DC converter, and can be applied to a step-up DC-DC converter as described later.

  As shown in FIG. 1, the DC voltage converter 10 includes an internal power line Ls, a first switch element SW1, a first parallel capacitor C1, a switch control unit 11, an auxiliary voltage application unit 12, a low-pass filter 13, and a reflux unit 14. , And an auxiliary resonant circuit 20.

  The internal power supply line Ls is connected to the battery Ba and supplies power from the battery Ba to each part of the DC voltage converter 10.

  In the present embodiment, the first switch element SW1 is configured by an N-channel MOSFET including a body diode D1. The drain of the first switch element SW1 is connected to the internal power supply line Ls.

  The first parallel capacitor C1 is connected in parallel to the first switch element SW1. The first parallel capacitor C1 is not limited to an individual element, and may be a parasitic capacitor of the first switch element SW1.

  The low-pass filter 13 is a well-known filter, and includes, for example, a smoothing reactor Lo and a smoothing capacitor Co as shown in FIG. An input terminal 13a (corresponding to one end of the low-pass filter) of the low-pass filter 13 is connected to a source terminal S (corresponding to one end of the first switch element) of the first switch element SW1, and an output terminal 13b of the DC voltage converter 10 is connected. Connected to the output terminal. The low-pass filter 13 receives the potential Vn1 of the first connection point N1, that is, the first connection point voltage Vn1, and outputs the output voltage Vout obtained by smoothing the first connection point voltage Vn1.

  The reflux unit 14 is connected between the first connection point N1 and the ground line Lg, and is well known. In the present embodiment, the reflux unit 14 is configured by the second switch element SW2 as shown in FIG. In the second switch element SW2, the body diode D2 is configured by an N-channel MOSFET, and zero voltage switching is performed by the switch control unit 11.

  The second parallel capacitor C2 is connected in parallel to the second switch element SW2. The second parallel capacitor C2 can adjust the changing speed of the first connection point potential Vn1 when the first switch element SW1 and the second switch element SW2 are in the off state, that is, the so-called dead time. Note that the second parallel capacitor C2 is not limited to an individual element, like the first parallel capacitor C1, and may be a parasitic capacitor of the second switch element SW2.

  As described above, since the reflux unit 14 is configured by the second switch element SW2, the setting of the reflux period can be appropriately performed by the on / off control of the second switch element SW2, and the switching of the second switch element SW2 by the zero voltage switching. Loss can be suppressed. The configuration of the reflux unit 14 is not limited to this, and may be configured by, for example, one reflux diode.

  The auxiliary resonance circuit 20 includes an auxiliary switch element AS and an auxiliary reactor LA, a first stabilization diode (first diode) D21, and a second stabilization diode (second diode) D22 connected in series. The auxiliary resonance circuit 20 is connected to a first connection point N1 that is a connection point between the first switch element SW1 and the low-pass filter 13. Specifically, one end La1 of the auxiliary reactor LA of the auxiliary resonance circuit 20 is connected to the first connection point N1. On the other hand, the other end La2 of the auxiliary reactor LA is connected to the drain D of the auxiliary switch element AS22. Here, the reactance of the auxiliary reactor LA is set to be sufficiently smaller than the smoothing reactor Lo.

  Specifically, as shown in FIG. 1, the auxiliary switch element AS is controlled by the switch control unit 11 at the same time, and is connected in series to two auxiliary switch elements SA (the first auxiliary switch element SA21 and the second auxiliary switch element SA21). It is constituted by an auxiliary switch element SA22). Each auxiliary switch element SA21, SA22 is configured by an N-channel MOSFET in this embodiment. In the following description, the two auxiliary switch elements (SA21, SA22) are referred to as “auxiliary switch elements SA” when it is not necessary to distinguish between them.

  The first stabilization diode D21 is connected between the second connection point N2, which is a connection point between the auxiliary reactor LA and the second auxiliary switch element SA22, and the ground line Lg. Specifically, the cathode of the first stabilization diode D21 is connected to the second connection point N2, and the anode of the first stabilization diode D21 is connected to the ground line Lg.

  The second stabilization diode D22 is connected between the third connection point N3, which is an intermediate connection point between the two auxiliary switch elements SA21 and SA22, and the internal power supply line Ls. Specifically, the cathode of the second stabilization diode D22 is connected to the internal power supply line Ls, and the anode of the second stabilization diode D22 is connected to the third connection point N3. The first stabilization diode D21 and the second stabilization diode D22 stabilize the voltage Vsa between the drain and the source of the auxiliary switch element SA when the auxiliary switch element SA is turned off.

  The auxiliary voltage application unit 12 is electrically connected to the auxiliary resonance circuit 20 and the ground line Lg, and supplies the auxiliary voltage VA having a constant voltage lower than the voltage value of the input voltage Vin to the auxiliary reactor LA via the auxiliary switch element SA. Apply. In the first embodiment, the auxiliary voltage application unit is configured by the battery 12 that outputs the auxiliary voltage VA. At that time, the positive output of the battery 12 is connected to the drain terminal of the first auxiliary switch element AS21 of the auxiliary resonance circuit 20, and the negative output of the battery 12 is connected to the ground line Lg.

  Here, the auxiliary voltage VA is not less than half of the input voltage Vin and less than the input voltage Vin. Thus, by setting the auxiliary voltage VA, each switch element can be surely soft-switched. In the first embodiment, the auxiliary voltage VA is about 30 V, for example.

  The switch control unit 11 is connected to each switch element (SW1, SW2, SA), and generates a gate control signal (G1, G2, GA) for controlling on / off switching of each switch element. Specifically, the switch control unit 11 switches the first and second switch elements (SW1, SW2) by so-called zero voltage switching (ZVS) according to the gate control signals (G1, G2). The switch control unit 11 switches the auxiliary switch element SA by so-called zero current switching (ZCS) by the gate control signal GA. Each switch element (SW1, SW2, SA) is not limited to an N-channel MOSFET. For example, an IGBT or the like may be used.

2. Operation of DC Voltage Converter Next, the operation of the DC voltage converter 10 will be described with reference to FIGS.
As shown in FIG. 2, at time t0 in the return state where the first switch element SW1 is in the OFF state and the second switch element SW2 is in the ON state, in other words, at the time t0 in the synchronous rectification state, the auxiliary switch element SA is When turned on by the GA, that is, when zero current switching (ZCS) is performed, the resonance operation by the auxiliary resonance circuit 20 is started.

  Then, in the first period K1, which is a period from time t0 to time t1, a current flows as shown in FIG. That is, the resonance current Irs that is a current flowing through the auxiliary switch element SA and the auxiliary reactor LA is increased, and accordingly, the second current Isw2 that is a current flowing through the second switch element SW2 is decreased. The increasing speed of the resonance current Irs depends on the reactance magnitude of the auxiliary reactor LA. In the first period K1, an output current Io that is a current flowing through the smoothing reactor Lo is constant. Note that the output current Io is substantially constant without being limited to the first period K1.

  Within the first period K1, the second switch element SW2 is turned off. As the second switch element SW2 is turned off, the second current Isw2 further decreases and becomes zero at time t1.

  FIG. 4 shows a current flow in a period (second period K2) from time t1 to time t2 when the first connection point voltage Vn1 becomes larger than the input voltage Vin. In the second period K2, since the first and second switch elements (SW1, SW2) are in the off state (so-called dead time), the resonance current Irs mainly includes the first parallel capacitor C1 and the second parallel capacitor C2. (See currents Ic1 and Ic2 in FIG. 4). At this time, the first parallel capacitor C1 is discharged, while the second parallel capacitor C2 is charged. Therefore, the first connection point voltage Vn1 increases. Here, the first connection point voltage Vn1 is equal to the second voltage Vsw2 that is the drain-source voltage of the second switch element SW2. Therefore, as shown in FIG. 2, the second voltage Vsw2 increases in the second period K2.

  At time t2, when the first connection point voltage Vn1 (second voltage Vsw2) becomes higher than the input voltage Vin, the body diode D1 of the first switch element SW1 becomes conductive, and the drain-source between the first switch element SW1. The first voltage Vsw1, which is a voltage, becomes zero. FIG. 5 shows a state from time t2 to time t3 (third period K3), which is a conduction period of the body diode D1. At this time, the first current Isw1 in the reverse direction flows through the body diode D1.

  Then, the first switch element SW1 is turned on while the body diode D1 is conducting (time t3). That is, the first switch element SW1 is zero voltage switched (ZVS). At this time, a reverse voltage (input voltage Vin−auxiliary voltage VA) is applied to the auxiliary reactor LA. Then, as shown in FIG. 2, after time t3, the first current Isw1, which is the current flowing through the first switch element SW1, increases, and the resonance current Irs decreases. Then, after the value of the first current Isw1 reaches the output current Io, the resonance current Irs becomes zero (time t4). FIG. 6 shows a current flow in a period (fourth period K4) from time t3 to time t4. In the fourth period K4, the first current Isw1 in the reverse direction first flows through the body diode D1, but when the resonance current Irs decreases and becomes smaller than the output current Io, the first current Isw1 in the forward direction. Begins to flow.

  Immediately after time t4 when the resonance current Irs becomes zero, the auxiliary switch element SA is turned off, that is, zero current switching (ZCS) is performed. Next, at a time t5 after the elapse of a predetermined time from the time t4, the first switch element SW1 is turned off, that is, zero voltage switching is performed. FIG. 7 shows a current flow in a period (fifth period K5) from time t4 to time t5. In the fifth period K5, the second switch element SW2 is in the off state, and the auxiliary resonance circuit 20 is not operating, so that a normal conversion operation is performed.

  Immediately after the first switch element SW1 is turned off at time t5, the first current Isw1 is commutated to the first parallel capacitor C1 and the second parallel capacitor C2 (see currents Ic1 and Ic2 in FIG. 8). At this time, the first connection point voltage Vn1 (second voltage Vsw2) drops rapidly. Then, after time t6 when the first connection point potential Vn1 becomes lower than zero V, the body diode D2 and the first stabilization diode D21 become conductive (see current Id21 in FIG. 9). When the first stabilization diode D21 is turned on, the potential at one end (second connection point N2) of the auxiliary reactor LA is maintained near zero V, and the oscillation of the potential at the second connection point N2 is suppressed.

  Then, at time t7 after time t6 when the body diode D2 becomes conductive, the second switch element SW2 is turned on, that is, zero voltage switching is performed, so-called synchronous rectification is started. Here, the period from time t5 to time t7 is a so-called dead time. FIG. 8 shows a current flow in a period (sixth period K6) from time t5 to time t6, which is the first half of the dead time, and FIG. 9 shows from time t6 to time t7, which is the second half of the dead time. The flow of current in the period (seventh period K7) is shown.

  A period (eighth period K8) from time t7 to time t8 when the second switch element SW2 is turned off next corresponds to a synchronous rectification period. After time t8, the operation from time t0 is repeated. Note that one cycle from time t0 to time t8 is, for example, 10 μs (microseconds).

  Here, the on / off timing of each gate control signal (G1, G2, GA) is determined by a known method. That is, the on / off timing is determined by the switch control unit 11 based on a comparison between a detection signal from a detection circuit (not shown) that detects an electrical quantity such as the resonance current Irs and a reference value, for example. Alternatively, it is determined in advance by calculation based on circuit constants such as the reactance value of the auxiliary reactor LA. In this case, the determined timing data is stored in a memory or the like of the switch control unit 11, and the switch control unit 11 determines the on / off timing based on the stored data. Alternatively, the on / off timing is determined based on both the detection signal and the stored data.

3. Effects of First Embodiment In the first embodiment, an auxiliary voltage application unit 12 that supplies power to the auxiliary resonance circuit 20 is provided. Therefore, the loss due to the auxiliary resonance circuit 20, for example, the switching loss due to the auxiliary switch elements (SA21, SA22) is not added to the switching loss of the first switch element SW1 when the input voltage Vin is converted to the output voltage Vout. The first switch element SW1 and the second switch element SW2 are zero-voltage switched, and the auxiliary switch elements (SA21, SA22) are zero-current switched. Therefore, according to the direct-current voltage converter 10 of the first embodiment, high conversion efficiency can be maintained even when applied to a large-capacity load.

  In the first embodiment, the first stabilization diode D21 connected between the second connection point N2 and the ground line Lg is provided. The first stabilization diode D21 can stabilize the potential at the second connection point N2 during the period when the auxiliary switch element SA is off. That is, in the period when the auxiliary switch element SA21 is off and the second switch element SW2 is on (seventh period K7), when the N-channel MOSFET is used as the auxiliary switch element SA as in the first embodiment, the auxiliary switch element It is conceivable that the potential at the second connection point N2 fluctuates via the parasitic capacitance of SA, and the potential at the second connection point N2 rises more than the input voltage Vin. However, at that time, the fluctuation of the potential at the second connection point N2 is suppressed by the first stabilization diode D21. Note that the first stabilization diode D21 may be omitted.

  In the first embodiment, the auxiliary switch element SA is composed of two auxiliary switch elements (SA21 and SA22) that are connected in series and controlled simultaneously by the switch control unit 11. For this reason, the on-resistance as the auxiliary switch element SA increases. Accordingly, the on-current that flows when the auxiliary switch element SA is turned on is reduced, and the on-resistance loss of the auxiliary switch element SA is reduced as compared with the case where the number of the auxiliary switch element SA is one. That is, the loss (power) is proportional to the square of the current. In this case, the amount of decrease in the on-resistance loss due to the decrease in the on-current is greater than the amount of increase in the on-resistance loss associated with the increase in on-resistance. Therefore, on-resistance loss is reduced.

  In the first embodiment, the second stabilization diode D22 connected between the third connection point N3, which is an intermediate connection point between the two auxiliary switch elements (SA21, SA2), and the internal power supply line Ls is provided. ing. The second stabilization diode D22 can stabilize the potential at the third connection point N3 during the period in which the first auxiliary switch element (one auxiliary switch element) SA21 close to the auxiliary voltage applying unit 12 is off. That is, during the period when the first auxiliary switch element SA21 is off and the second auxiliary switch element (the other auxiliary switch element) SA22 and the second switch element SW2 are on, the first auxiliary switch element SA21 as in the first embodiment. When an N-channel MOSFET is used, it is conceivable that the potential of the third connection point N3 varies via the parasitic capacitance of the first auxiliary switch element SA21. At this time, the fluctuation of the potential at the third connection point N3 is suppressed by the second stabilization diode D22. Note that the second stabilization diode D22 may be omitted.

  In addition, the voltage applied to each switch element (SW1, SW2, SA) can be made substantially the same level as the input voltage Vin, and the current flowing through each switch element can be made almost the same level as the output current Io. Therefore, each switch element can be a component with a small rating, thereby reducing conduction loss.

<Embodiment 2>
A second embodiment will be described with reference to FIG. Only the configuration of the auxiliary voltage applying unit 12 is different from the first embodiment. Therefore, only the differences of the auxiliary voltage application unit 12 will be described below.

  As shown in FIG. 10, the auxiliary voltage applying unit 12A in the second embodiment includes an external connection terminal J1 connected to the intermediate potential unit 40m of the battery 40 having a voltage value “VA”, an external connection terminal J1, and an auxiliary And a voltage application line Lv connecting the switch element SA21. In this case, the voltage application line Lv is connected to the drain terminal of the first auxiliary switch element AS21 of the auxiliary resonance circuit 20, and the external connection terminal J1 is connected to the ground line Lg via the battery 40.

  According to the auxiliary voltage application unit 12A in the second embodiment, it is not necessary to separately provide a configuration of an auxiliary power source such as a battery in the DC voltage converter 10, and the auxiliary voltage application unit can be formed with a simple configuration.

  Note that the configuration of the auxiliary voltage application unit is not limited to this, and for example, a converter that converts the input voltage Vin into the auxiliary voltage VA may be provided, and the auxiliary voltage application unit 12 may be configured by this converter. Alternatively, the battery 40 as the main power source may be provided as the configuration of the DC voltage conversion device 10 and the auxiliary voltage application unit may be configured by a part of the battery.

<Other embodiments>
The present invention is not limited to the embodiments described above with reference to the drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the above-described embodiment, the auxiliary switch element SA is configured by two auxiliary switch elements (SA21, SA2), but is not limited thereto. For example, the auxiliary switch element SA may be configured by one auxiliary switch element SA21.

  (2) In the above embodiment, the example in which the reflux unit 14 is configured by the second switch element SW2 and the second parallel capacitor C2 is shown, but the present invention is not limited thereto. For example, the reflux unit 14 may be configured by a single reflux diode.

  (3) In the above embodiment, the DC voltage converter 10 is applied to a chopper type step-down DC-DC converter. However, the present invention is not limited to this. For example, the DC voltage converter 10 is replaced with a chopper type step-up DC-DC. It can also be applied to a DC converter. FIG. 11 shows an example of control and operation when the DC voltage converter 10 is applied to a chopper type step-up DC-DC converter. Specifically, FIG. 11 shows an example of control and operation in the boost mode in a bidirectional step-down / step-up DC-DC converter in which the input side and the output side can be reversed. For example, it is assumed that the input side of the DC voltage converter 10 is connected to a 48V battery and the output side is connected to a 12V battery.

In FIG. 11, time t0 indicates the time when the gate control signal GA is turned on, time t1 indicates the time when the gate control signal G2 is turned off, and time t2 indicates the time when the gate control signal G1 is turned on. Time t3 indicates the time when the gate control signal G1 is turned off, time t4 indicates the time when the gate control signal GA is turned off, and time t5 indicates the time when the gate control signal G2 is turned on. Time t6 indicates the time when the gate control signal GA is turned on again.
Here, the step-up mode can be realized with the same circuit configuration as that of the first embodiment shown in FIG. 1, and only the on / off timing of each gate control signal (G1, G2, GA) is different from that of the first embodiment. In other words, the step-down DC-DC converter shown in FIG. 1 can be operated as a step-up DC-DC converter by changing only the on / off timing of each gate control signal (G1, G2, GA).

  That is, during the step-down operation, current flows from the high voltage side (left side in FIG. 1) to the low voltage side (right side). At this time, the output current Io increases as the ON time of the first switch element SW1 (the time from time t2 to time t3 in FIG. 11) is increased, and the output current Io decreases as the time is shortened. When the ON time of the first switch element SW1 at the time when the output current Io becomes zero is further shortened, the current of the DC voltage converter 10 starts to flow in the reverse direction (from the low voltage side to the high voltage side) and enters the boost mode. change. This means that the low pressure on the output side (right side in FIG. 1) has been converted to the high pressure on the input side (left side in FIG. 1). In this case, similarly to the normal chopper method, the second switch element SW2 becomes a synchronous rectifier element at the time of step-down, and the first switch element SW1 becomes a synchronous rectifier element at the time of step-up. Even at the time of boosting, all the switch elements (SW1, SW1, SA) are zero-voltage or zero-current switching (soft switching).

As described above, the DC voltage conversion apparatus 10 according to the first embodiment is a bidirectional type by simply changing the on / off timing of each gate control signal (G1, G2, GA) without changing the circuit configuration. The step-down / step-up DC-DC converter can be realized.
The DC voltage converter 10 is not limited to this, and can also be applied to a normal unidirectional step-up DC-DC converter in which the input side and the output side are fixed.

DESCRIPTION OF SYMBOLS 10 ... DC voltage converter 11 ... Switch control part 12 ... Auxiliary voltage application part 13 ... Low pass filter 14 ... Recirculation | reflux part 20 ... Auxiliary resonance circuit 40 ... Main power supply C1 ... 1st parallel capacitance C2 ... 2nd parallel capacitance D21 ... 1st Stabilization diode (first diode)
D22: Second stabilizing diode (second diode)
J1 ... External connection terminal (auxiliary voltage application unit)
LA ... auxiliary reactor Lg ... ground line Ls ... internal power supply line Lv ... voltage application line (auxiliary voltage application unit)
N1 ... first connection point N2 ... second connection point N3 ... third connection point SA ... auxiliary switch element SA21 ... first auxiliary switch element (N-channel MOSFET)
SA22: second auxiliary switch element (N-channel MOSFET)
SW1... First switch element (N-channel MOSFET)
SW2: Second switch element (N-channel MOSFET)

Claims (8)

A DC voltage converter that converts a DC input voltage applied from a main power source into an output voltage having a predetermined voltage value,
An internal power line connected to the main power source;
A first switch element connected to the internal power line;
A low-pass filter having one end connected to one end of the first switch element;
An auxiliary resonance circuit including an auxiliary switch element and an auxiliary reactor connected in series, wherein one end of the auxiliary reactor is connected to a first connection point that is a connection point between the first switch element and the low-pass filter;
An auxiliary voltage applying unit electrically connected to the auxiliary resonant circuit and a ground line, and applying an auxiliary voltage having a constant voltage lower than a voltage value of the input voltage to the auxiliary reactor via the auxiliary switch element;
A reflux portion connected between the first connection point and the ground line;
A switch controller for zero voltage switching the first switch element and zero current switching the auxiliary switch element;
DC voltage converter with In the DC voltage converter according to claim 1,
The reflux unit is a DC voltage converter configured by a second switch element that is zero-voltage switched by the switch control unit. In the direct-current voltage converter according to claim 1 or 2,
A first parallel capacitor connected in parallel to the first switch element;
The direct-current voltage converter further comprising a second parallel capacitor connected in parallel to the reflux unit. In the direct-current voltage converter according to any one of claims 1 to 3,
The direct-current voltage converter, further comprising a first diode connected between a second connection point, which is a connection point between the auxiliary reactor and the auxiliary switch element, and the ground line. In the direct-current voltage converter according to any one of claims 1 to 4,
The auxiliary switch element is simultaneously controlled by the switch control unit,
A direct-current voltage converter comprising two auxiliary switch elements connected in series. In the DC voltage converter according to claim 5,
The direct-current voltage converter, further comprising: a second diode connected between a third connection point that is an intermediate connection point of the two auxiliary switch elements and the internal power supply line. In the DC voltage converter as described in any one of Claims 1-6,
The main power source is composed of a battery composed of a plurality of cells,
The auxiliary voltage application unit includes:
An external connection terminal connected to the intermediate potential portion of the battery;
A voltage application line connecting the external connection terminal and the auxiliary switch element;
A DC voltage converter configured by In the DC voltage converter as described in any one of Claims 1-7,
The auxiliary voltage has a voltage value that is more than half of the input voltage.

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