JP2015198507A - Power circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce switching loss of a power circuit.SOLUTION: A power circuit 10 includes: switching elements S1, S2; a coil L0 which has one terminal connected to an arm connection point; a coil L1 which has a lower terminal connected to a drain terminal of the switching element S1 and an upper terminal connected to the arm connection point; and a diode D1 which is provided on a path connecting the drain terminal of the switching element S1 and an upper terminal of an upper arm circuit to each other not via neither the switching element S2 nor the coil L1. The switching element S1 is brought under pulse-width modulation control, and the switching element S2 turns ON in a part of an OFF period of the switching element S1. The switching element S1 changes an OFF state to an ON state while a current flows to an internal diode B2 of the switching element S2.

Description

  The present invention relates to a power supply circuit, and more particularly to a power supply circuit including a switching element such as a MOSFET.

  Conventionally, a power supply circuit such as a DC / DC converter or an inverter in which a switching element is provided in each of a lower arm circuit and an upper arm circuit is known. FIG. 15 is a circuit diagram showing a part of the inverter. In the circuit shown in FIG. 15, a switching element SL is provided in the lower arm circuit, a switching element SH is provided in the upper arm circuit, and a wiring W is connected to the arm connection point. MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors) or the like are used for the switching elements SL and SH. When the switching element SL is in an off state and the switching element SH is in an on state, current flows from the switching element SH to the wiring W. When the switching element SL is on and the switching element SH is off, current flows from the wiring W to the switching element SL.

  In a power supply circuit including a switching element, a switching loss occurs when the switching element changes between an on state and an off state. In particular, in a power supply circuit including a high-voltage, high-current MOSFET as a switching element, the recovery characteristics of a built-in diode (also referred to as a parasitic diode or an accompanying diode) included in the MOSFET are poor, and a large switching loss occurs due to the recovery current. . For example, in the circuit shown in FIG. 15, when the switching element SL changes from the off state to the on state, the recovery current Ir of the built-in diode BH of the switching element SH flows to the switching element SL, and a switching loss occurs.

  Patent Documents 1 to 3 describe conventional power supply circuits that reduce switching loss. Among these, in Patent Document 1, when power conversion from direct current to alternating current is performed in the power conversion device shown in FIG. 16, the semiconductor switch Q1 is in the on state, the semiconductor switches Q2 to Q4 are in the off state, and the current is a broken line. It is described that the semiconductor switch Q4 changes from the off state to the on state while flowing along the path indicated by the arrow. When the semiconductor switch Q4 changes from the off state to the on state, the recovery current of the diode D7 flows into the semiconductor switch Q4, and switching loss occurs. Patent Document 1 describes that by using a high-speed diode as the diode D7, the recovery current of the diode D7 is reduced and the switching loss is reduced.

JP 2010-11555 A JP 2003-102168 A JP 2010-68619 A

  However, in the state shown in FIG. 16, a certain amount of current flows through the diode D7. Since the recovery phenomenon occurs when the current flowing through the diode D7 is large, the recovery current of the diode D7 is large and the switching loss due to the recovery current is also large. Even if a high-speed diode is used as the diode D7, generation of a recovery current cannot be prevented.

  Therefore, an object of the present invention is to provide a power supply circuit in which switching loss is further reduced.

A first invention is a power supply circuit,
A lower switching element provided in the lower arm circuit;
An upper switching element provided in the upper arm circuit;
A coil with one terminal connected to the arm connection point;
When one of the lower side and the upper side is the first side and the other is the second side, the second side is between the second side terminal of the first side switching element and the second side terminal of the second side arm circuit. A current limiting coil provided in series with the switching element;
A diode provided on a path connecting the second side terminal of the first side switching element and the second side terminal of the second side arm circuit without passing through the second side switching element and the current limiting coil; With
The first side switching element is subjected to pulse width modulation control,
The second side switching element is turned on during a part of the off period of the first side switching element, and is otherwise turned off.
The first side switching element changes from an off state to an on state while a current flows through a built-in diode of the second side switching element.

According to a second invention, in the first invention,
The first side is the lower side, the second side is the upper side,
A lower terminal of the current limiting coil is connected to an upper terminal of the lower switching element;
The upper terminal of the current limiting coil is connected to the arm connection point,
The diode is provided on the path with an anode terminal on the upper terminal side of the lower switching element and a cathode terminal on the upper terminal side of the upper arm circuit.

According to a third invention, in the first invention,
The first side is the lower side, the second side is the upper side,
The lower terminal of the current limiting coil is connected to the arm connection point,
An upper terminal of the current limiting coil is connected to a lower terminal of the upper switching element;
The diode is provided on the path with an anode terminal on the upper terminal side of the lower switching element and a cathode terminal on the upper terminal side of the upper arm circuit.

According to a fourth invention, in the first invention,
The first side is the lower side, the second side is the upper side,
A lower terminal of the current limiting coil is connected to an upper terminal of the upper switching element;
An upper terminal of the current limiting coil is connected to an upper terminal of the upper arm circuit;
The diode is provided on the path with an anode terminal on the upper terminal side of the lower switching element and a cathode terminal on the upper terminal side of the upper arm circuit.

According to a fifth invention, in the first invention,
The first side is the upper side, the second side is the lower side,
An upper terminal of the current limiting coil is connected to a lower terminal of the upper switching element;
The lower terminal of the current limiting coil is connected to the arm connection point,
The diode is provided on the path with an anode terminal on the lower terminal side of the lower arm circuit and a cathode terminal on the lower terminal side of the upper switching element.

According to a sixth invention, in the first invention,
The first side is the upper side, the second side is the lower side,
The upper terminal of the current limiting coil is connected to the arm connection point,
A lower terminal of the current limiting coil is connected to an upper terminal of the lower switching element;
The diode is provided on the path with an anode terminal on the lower terminal side of the lower arm circuit and a cathode terminal on the lower terminal side of the upper switching element.

According to a seventh invention, in the first invention,
The first side is the upper side, the second side is the lower side,
An upper terminal of the current limiting coil is connected to a lower terminal of the lower switching element;
A lower terminal of the current limiting coil is connected to a lower terminal of the lower arm circuit;
The diode is provided on the path with an anode terminal on the lower terminal side of the lower arm circuit and a cathode terminal on the lower terminal side of the upper switching element.

In an eighth aspect based on the first aspect,
A current limiting circuit provided in series with the diode is further provided on the path.

A ninth invention is a power supply circuit,
A lower switching element provided in the lower arm circuit;
An upper switching element provided in the upper arm circuit;
A coil with one terminal connected to the arm connection point;
A first current limiting coil having a lower terminal connected to the upper terminal of the lower switching element and an upper terminal connected to the arm connection point;
A second current limiting coil having a lower terminal connected to the arm connection point and an upper terminal connected to the lower terminal of the upper switching element;
An anode terminal on a first path connecting the upper terminal of the lower switching element and the upper terminal of the upper arm circuit without passing through the upper switching element, the first current limiting coil and the second current limiting coil; A first diode provided on the upper terminal side of the lower switching element and a cathode terminal on the upper terminal side of the upper arm circuit;
A first current limiting circuit provided in series with the first diode on the first path;
On the second path connecting the lower terminal of the upper switching element and the lower terminal of the lower arm circuit without passing through the lower switching element, the first current limiting coil, and the second current limiting coil A second diode provided with an anode terminal on the lower terminal side of the lower arm circuit and a cathode terminal on the lower terminal side of the upper switching element;
A second current limiting circuit provided in series with the second diode on the second path;
A first period in which the lower switching element is subjected to pulse width modulation control, the upper switching element is turned on in a part of an off period of the lower switching element, and the upper switching element is subjected to pulse width modulation control, A second period in which the lower switching element is turned on in a part of the off period of the upper switching element,
In the first period, the lower switching element changes from an off state to an on state while a current flows through a built-in diode of the upper switching element,
In the second period, the upper switching element changes from an off state to an on state while a current flows through a built-in diode of the lower switching element.

  A tenth invention is a power supply device including a plurality of power supply circuits according to any one of the first to ninth inventions.

  According to the first aspect, when the second side switching element changes to the ON state, the current that has been flowing to the diode until then flows to the second side switching element, and the current that flows to the diode decreases. Therefore, when the first side switching element changes to the ON state, the recovery current of the diode can be reduced, and the switching loss due to the recovery current of the diode can be reduced. Further, when the first side switching element changes to the ON state, the potential of the terminal on the current limiting coil side of the second side switching element is changed by the action of the current limiting coil to the second side terminal of the first side switching element. It changes later than the potential. For this reason, when the recovery current of the built-in diode of the second side switching element flows, the voltage across the first side switching element is already sufficiently small (preferably, almost zero). Therefore, switching loss due to the recovery current of the built-in diode of the second side switching element can also be reduced.

  According to the second to fourth inventions described above, in the booster circuit that controls the pulse width modulation of the lower switching element, the switching current caused by the recovery current of the diode and the recovery current of the built-in diode of the upper switching element is reduced. be able to.

  According to the fifth to seventh inventions described above, in the step-down circuit that controls the pulse width modulation of the upper switching element, the switching loss caused by the recovery current of the diode and the recovery current of the built-in diode of the lower switching element is reduced. be able to.

  According to the eighth aspect, by providing the current limiting circuit, the current flowing through the diode is limited while the first side switching element is in the OFF state. For this reason, when the second side switching element changes from the OFF state to the ON state, the current that has been flowing to the diode until then flows quickly to the second side switching element, and the current that flows to the diode decreases rapidly. Therefore, even when the off-period of the first side switching element is short, the switching loss due to the recovery current of the diode and the recovery current of the built-in diode of the second side switching element can be reduced.

  According to the ninth aspect of the invention, in the power supply circuit that selectively controls the pulse width modulation of the lower switching element and the upper switching element, the recovery currents of the first and second diodes, and the lower and upper switching elements are built-in. Switching loss due to the recovery current of the diode can be reduced. Also, by providing the first and second current limiting circuits, the circulating current passing through the lower switching element and the second diode and the circulating current passing through the upper switching element and the first diode are reduced, The amount of heat generated in the upper switching element can be reduced.

  According to the tenth aspect of the present invention, switching loss can be reduced for a power supply device including a plurality of power supply circuits.

1 is a circuit diagram of a power supply circuit according to a first embodiment of the present invention. It is a figure for demonstrating operation | movement of the power supply circuit shown in FIG. It is a figure for demonstrating operation | movement of the power supply circuit shown in FIG. It is a figure for demonstrating operation | movement of the power supply circuit shown in FIG. It is a figure for demonstrating operation | movement of the power supply circuit shown in FIG. It is a figure which shows the electric current which flows into the power supply circuit which concerns on a 1st comparative example. It is a figure which shows the electric current which flows into the power supply circuit which concerns on a 3rd comparative example. It is a circuit diagram of the power circuit concerning the modification of the 1st embodiment of the present invention. FIG. 6 is a diagram showing a first example of a current limiting circuit of the power supply circuit shown in FIG. 5. FIG. 6 is a diagram showing a second example of the current limiting circuit of the power supply circuit shown in FIG. 5. It is a circuit diagram of the power supply circuit which concerns on the 2nd Embodiment of this invention. It is a circuit diagram of the power circuit concerning the modification of the 2nd Embodiment of this invention. It is a circuit diagram of the power supply circuit which concerns on the 3rd Embodiment of this invention. It is a circuit diagram of the power supply circuit which concerns on the 4th Embodiment of this invention. It is a circuit diagram of the power supply circuit which concerns on the modification of the 4th Embodiment of this invention. It is a circuit diagram of the power supply device which concerns on the 5th Embodiment of this invention. It is a circuit diagram of the power supply device which concerns on the 6th Embodiment of this invention. It is a figure which shows the electric current which flows into the power supply circuit which concerns on a 4th comparative example. It is a figure which shows the electric current which flows into the power supply circuit which concerns on a 4th comparative example. It is a figure which shows the recovery electric current which generate | occur | produces with the conventional inverter. It is a figure which shows the electric current which flows into the conventional power converter device.

(First embodiment)
FIG. 1 is a circuit diagram of a power supply circuit according to the first embodiment of the present invention. A power supply circuit 10 shown in FIG. 1 is a step-up chopper circuit including switching elements S1 and S2, coils L0 and L1, a diode D1, an input capacitor C1, and an output capacitor C2. The power supply circuit 10 has terminals T1 to T4 for external connection. A DC power supply 1 is connected to the terminals T1 and T2, and a DC load 2 is connected to the terminals T3 and T4 as an output load. A reference potential (hereinafter referred to as 0V) is applied to the terminals T2 and T4. The power supply circuit 10 boosts the voltage input from the terminals T1 and T2, and outputs the boosted voltage from the terminals T3 and T4.

  The power supply circuit 10 has a configuration in which a coil L1 and a diode D1 are added to a step-up chopper circuit having switching elements S1 and S2 and a coil L0. As the diode D1, for example, an FRD (Fast Recovery Diode) having excellent recovery characteristics, a Schottky Barrier Diode (hereinafter referred to as SBD) using a compound semiconductor such as SiC (silicon carbide), or the like is used. The For example, N-channel MOSFETs are used for the switching elements S1 and S2. A built-in diode is generated between the drain and source of the MOSFET. Hereinafter, a built-in diode of the switching element S * (* is a character string of one or more characters) is referred to as B *.

  One terminal (lower terminal) of the coil L1 is connected to the drain terminal of the switching element S1 and the anode terminal of the diode D1. The other terminal (upper terminal) of the coil L1 is connected to the source terminal of the switching element S2 and one terminal (right terminal in FIG. 1) of the coil L0. The other terminal (the left terminal in FIG. 1) of the coil L0 is connected to the terminal T1. The drain terminal of the switching element S2 and the cathode terminal of the diode D1 are connected to the terminal T3. The source terminal of the switching element S1 is connected to the terminals T2 and T4. The input capacitor C1 is provided between the terminals T1 and T2, and the output capacitor C2 is provided between the terminals T3 and T4. Note that the power supply circuit 10 may not include the input capacitor C1 and may not include the output capacitor C2.

  Thus, in the power supply circuit 10, the switching element S1 and the coil L1 (current limiting coil) are provided in the lower arm circuit, and the switching element S2 is provided in the upper arm circuit. One terminal of the coil L0 is connected to the arm connection point. The coil L1 is provided in series with the switching element S2 (upper switching element) between the drain terminal of the switching element S1 (upper terminal of the lower switching element) and the terminal T3 (upper terminal of the upper arm circuit). The lower terminal of the coil L1 is connected to the drain terminal of the switching element S1, and the upper terminal of the coil L1 is connected to the arm connection point. The diode D1 passes through the path connecting the drain terminal of the switching element S1 and the terminal T3 without passing through the switching element S2 and the coil L1, and has an anode terminal on the drain terminal side of the switching element S1 and a cathode terminal on the terminal T3. It is provided on the side.

  Control signals CS1 and CS2 are supplied to the gate terminals of the switching elements S1 and S2, respectively. The control signal CS1 is a PWM (Pulse Width Modulataion) signal having a predetermined duty ratio. The frequency of the control signal CS1 is set to, for example, several kHz to several hundred kHz. The control signal CS2 is a signal that changes complementarily to the control signal CS1. However, a first dead time is provided between the time when the control signal CS1 changes to the low level and the time when the control signal CS2 changes to the high level, and the control signal CS1 changes after the control signal CS2 changes to the low level. A second dead time is provided until the level changes to a high level.

  The switching element S1 is subjected to pulse width modulation control based on the control signal CS1. Based on the control signal CS2, the switching element S2 is turned on during a part of the off period of the switching element S1, and is otherwise turned off. By controlling the switching elements S1 and S2 in this way, the input voltage can be boosted according to the duty ratio of the PWM signal.

  The inductance value of the coil L0 is determined by the same method as that of a general boost chopper circuit. For example, when an input voltage is 150 V, an input current is 10 A, a PWM signal frequency is 20 kHz, an output voltage is 300 V, and an inductor having an inductance value of 1.25 mH is used as the coil L0, the inductor current ripple is about ± 15%. It becomes. As the coil L1, a coil having an inductance value smaller than that of the coil L0 (for example, a coil having an inductance value of about 50 nH to 10 μH, more preferably a coil having an inductance value of about 100 nH to 2 μH) is used.

  Hereinafter, the operation of the power supply circuit 10 will be described with reference to FIGS. 2A to 2D. FIG. 2A shows a current flowing through the power supply circuit 10 when the switching element S1 is in the on state and the switching element S2 is in the off state. FIG. 2B shows the current flowing through the power supply circuit 10 after the switching element S1 changes from the on state to the off state. FIG. 2C shows a current flowing through the power supply circuit 10 when the switching element S1 is in the off state and the switching element S2 is in the on state. FIG. 2D shows the current flowing through the power supply circuit 10 after the switching element S1 changes from the off state to the on state. Hereinafter, the current flowing through the coil L1 is IL1, the current flowing through the switching element S2 is IS2, the forward voltage of the diode D1 is Vf1, and the potential of the terminal T3 is Vout.

  When the switching element S1 is in the on state and the switching element S2 is in the off state (FIG. 2A), a current that flows through the coils L0 and L1 and the switching element S1 flows between the terminals T1 and T2. At this time, energy is accumulated in the coils L0 and L1.

  Next, the switching element S1 changes from the on state to the off state (FIG. 2B). Until the switching element S1 changes to a complete OFF state, the channel resistance of the switching element S1 increases and the drain potential of the switching element S1 increases. When the drain potential of the switching element S1 rises to (Vout + Vf1), a part of the current IL1 flows to the terminal T3 via the diode D1. After the switching element S1 changes to the complete OFF state, the entire current IL1 flows to the terminal T3 via the diode D1.

  Next, after the first dead time, the switching element S2 changes from the off state to the on state (FIG. 2C). After the switching element S2 changes to the ON state, the current that has passed through the coil L0 flows to the terminal T3 through a path that passes through the coil L1 and the diode D1 and a path that passes through the switching element S2. At this time, the energy stored in the coils L0 and L1 while the switching element S1 is on is released.

  The current flowing through the switching element S2 flows through the low resistance channel region. For this reason, the source potential of the switching element S2 becomes Vout similarly to the drain potential of the switching element S2. On the other hand, when a forward current flows through the diode D1, the cathode potential of the diode D1 is lower than the anode potential by the forward voltage. Therefore, the anode potential of the diode D1 is (Vout + Vf1). Therefore, when the direction of the current IL1 shown in FIG. 2C is positive, the voltage across the coil L1 is (−Vf1). Since a negative voltage is applied across the coil L1, the current IL1 decreases. Current IS2 increases by a decrease of current IL1.

  Next, after the current IL1 becomes sufficiently small (preferably, after the current IL1 becomes almost zero), the switching element S2 changes from the on state to the off state. Even after the switching element S2 changes to the OFF state, the current IS2 continues to flow through the built-in diode B2. At this time, the potentials at both ends of the coil L1 are both Vout. Strictly speaking, the potential of the upper terminal of the coil L1 is higher than the potential Vout by the forward voltage of the built-in diode B2.

  Next, after the second dead time, the switching element S1 changes from the off state to the on state (FIG. 2D). In this way, the switching element S1 changes from the off state to the on state while the current flows through the built-in diode B2 of the switching element S2. When the switching element S1 is turned on, the drain potential of the switching element S1 immediately decreases to the reference potential. On the other hand, the source potential of the switching element S2 does not drop immediately due to the current limiting action of the coil L1. A current corresponding to the voltage across the coil L1 gradually flows through the coil L1. Therefore, the current passing through the coil L1 and the switching element S1 starts to flow later than the change of the switching element S1 to the ON state.

  While the current flowing through the coil L0 is larger than the current flowing through the coil L1, the current IS2 continues to flow. When the current flowing through the coil L0 becomes equal to the current flowing through the coil L1, the current IS2 stops flowing. When the current IS2 stops flowing, the source potential of the switching element S2 decreases, and the recovery current of the built-in diode B2 of the switching element S2 flows to the switching element S1. In particular, when a super junction MOSFET is used as the switching element S2, the charging current of the source-drain capacitance of the switching element S2 also flows through the switching element S1. However, when the recovery current or the charging current starts to flow, the drain potential of the switching element S1 has already decreased (preferably, almost decreased to the reference potential), and the drain-source voltage of the switching element S1 is Already small enough (preferably nearly zero). For this reason, the switching loss resulting from the recovery current of the built-in diode B2 of the switching element S2 is small.

  When the switching element S1 changes from the off state to the on state, the recovery current of the diode D1 flows to the switching element S1. However, when the switching element S2 changes from the off state to the on state, the current that has been flowing to the diode D1 until then flows to the switching element S2, and the current that flows to the diode D1 decreases. Thus, since the recovery phenomenon occurs when the current flowing through the diode D1 is small, the recovery current of the diode D1 is small and the switching loss due to the recovery current of the diode D1 is also small.

  Hereinafter, the effect of the power supply circuit 10 according to the present embodiment will be described in comparison with the comparative example. Here, as comparative examples, a circuit in which the coil L1 and the diode D1 are deleted from the power supply circuit 10 (first comparative example), a circuit in which the diode D1 is deleted from the power supply circuit 10 (second comparative example), and the power supply circuit 10 Consider a circuit (third comparative example) that keeps the switching element S2 in the OFF state during the ON period of the switching element S1.

  In the power supply circuit according to the first comparative example, when the switching element S1 changes from the off state to the on state, the recovery current Ir of the built-in diode B2 of the switching element S2 flows to the switching element S1 (see FIG. 3). Since the recovery current Ir flows to the switching element S1 when the drain potential of the switching element S1 is still high, a large switching loss occurs. On the other hand, in the power supply circuit 10, when the recovery current of the built-in diode B2 of the switching element S2 flows, the drain-source voltage of the switching element S1 is already sufficiently small (preferably almost zero). Therefore, the switching loss is small. Therefore, according to the power supply circuit 10, switching loss can be reduced as compared with the power supply circuit according to the first comparative example.

  In the power supply circuit according to the second comparative example, when the switching element S1 changes from the on state to the off state, a large surge is generated at the drain terminal of the switching element S1 due to the energy stored in the coil L1, and the switching element S1 It can be destroyed. In contrast, in the power supply circuit 10, when the switching element S1 changes from the on state to the off state, the current IL1 flows to the terminal T3 via the diode D1. Therefore, according to the power supply circuit 10, the occurrence of the surge can be prevented and the switching element S1 can be prevented from being destroyed.

  In the power supply circuit according to the third comparative example, when the switching element S1 changes from the on state to the off state, the current IL1 flows to the terminal T3 via the diode D1 (see FIG. 4). However, the power supply circuit according to the third comparative example does not have a function of switching the path of the current IL1 from the path via the diode D1 to the path via the switching element S2. For this reason, even after the switching element S1 changes from the on state to the off state, the current IS2 hardly increases and the current IL1 hardly decreases. Next, after the switching element S1 changes from the off state to the on state, the current IL1 flows through the switching element S1, not through the diode D1. However, since a large amount of current flows through the diode D1 at that time, the recovery current of the diode D1 is large and a large switching loss occurs. A power supply circuit including a diode instead of the switching element S2 has the same problem.

  On the other hand, in the power supply circuit 10, when the switching element S1 changes from the on state to the off state, the current IS2 increases and the current IL1 decreases and eventually stops flowing. For this reason, the current flowing through the diode D1 before the switching element S1 changes from the off state to the on state is smaller than that of the power supply circuit according to the third comparative example. Therefore, according to the power supply circuit 10, switching loss can be reduced as compared with the power supply circuit according to the third comparative example.

  As described above, in the power supply circuit 10 according to the present embodiment, when the switching element S2 changes to the ON state, the current that has been flowing to the diode D1 until then flows to the switching element S2, and the current that flows to the diode D1 is Decrease. Therefore, when the switching element S1 changes to the ON state, the recovery current of the diode D1 can be reduced, and the switching loss due to the recovery current of the diode D1 can be reduced. When the switching element S1 changes to the on state, the potential at the source terminal of the switching element S2 changes with a delay from the potential at the drain terminal of the switching element S1 due to the action of the coil L1. For this reason, when the recovery current of the built-in diode B2 of the switching element S2 flows, the voltage across the switching element S1 is already sufficiently small (preferably almost zero). Therefore, switching loss due to the recovery current of the built-in diode B2 of the switching element S2 can also be reduced. Therefore, according to the power supply circuit 10 according to the present embodiment, the switching loss due to the recovery current of the diode D1 and the recovery current of the built-in diode B2 of the switching element S2 in the booster circuit that controls the pulse width modulation of the switching element S1. Can be reduced.

  FIG. 5 is a block diagram showing a configuration of a power supply circuit according to a modification of the first embodiment of the present invention. The power supply circuit 15 shown in FIG. 5 is obtained by adding a current limiting circuit X1 to the power supply circuit 10. The current limiting circuit X1 is provided in series with the diode D1 on a path connecting the drain terminal of the switching element S1 and the terminal T3 without passing through the switching element S2 and the coil L1. The current limiting circuit X1 includes, for example, a resistance element, a diode, a series body of a plurality of diodes, or a circuit in which these are connected in series. 6A and 6B are circuit diagrams illustrating examples of current limiting circuits. The current limiting circuit X1 illustrated in FIG. 6A includes a resistance element Rx, and the current limiting circuit X1 illustrated in FIG. 6B includes a diode Dx. The diode Dx may be a single diode or a series of diodes. In either case, the diode Dx can be configured using FRD, SiC SBD, or the like.

  By providing the current limiting circuit X1 in series with the diode D1, the current flowing through the diode D1 is limited while the switching element S1 is in the OFF state. For this reason, after the switching element S2 changes from the OFF state to the ON state, the current that has been flowing to the diode D1 until then flows quickly to the switching element S2, and the current that flows to the diode D1 decreases rapidly. Therefore, even when the off period of the switching element S1 is short, such as when the step-up rate is high or when the high-frequency operation is performed, switching due to the recovery current of the diode D1 and the recovery current of the built-in diode B2 of the switching element S2 Loss can be reduced.

  In the power supply circuit 15 shown in FIG. 5, the current limiting circuit X1 is provided on the cathode terminal side of the diode D1, but the current limiting circuit X5 may be provided on the anode terminal side of the diode D1. In addition, in the second to fifth embodiments described later, a modification in which a current limiting circuit is added in series with the diode can be configured by the same method as the first embodiment.

(Second Embodiment)
FIG. 7 is a circuit diagram of a power supply circuit according to the second embodiment of the present invention. The power supply circuit 20 shown in FIG. 7 is obtained by changing the position where the coil L1 is provided in the power supply circuit 10 according to the first embodiment. In the power supply circuit 10, the coil L1 is provided in the same arm circuit (lower arm circuit) as the switching element S1 subjected to pulse width modulation control. The lower terminal of the coil L1 is connected to the drain terminal of the switching element S1, and the upper terminal of the coil L1 is connected to the arm connection point.

  On the other hand, in the power supply circuit 20 according to the present embodiment, the coil L1 is provided in an arm circuit (upper arm circuit) different from the switching element S1 that is subjected to pulse width modulation control. The lower terminal of the coil L1 is connected to the arm connection point, and the upper terminal of the coil L1 is connected to the source terminal of the switching element S2 (lower terminal of the upper switching element). The power supply circuit 20 operates in the same manner as the power supply circuit 10.

  According to the power supply circuit 20 according to the present embodiment, as in the first embodiment, the recovery current of the diode D1 and the built-in diode B2 of the switching element S2 of the booster circuit that controls the switching width of the switching element S1 are controlled. Switching loss due to the recovery current can be reduced.

  FIG. 8 is a block diagram showing a configuration of a power supply circuit according to a modification of the second embodiment of the present invention. The power supply circuit 25 shown in FIG. 8 is obtained by changing the position where the coil L1 is provided in the power supply circuit 10 according to the first embodiment. In the power supply circuit 25, the coil L1 is provided in an arm circuit different from the switching element S1 that is subjected to pulse width modulation control. The lower terminal of the coil L1 is connected to the drain terminal of the switching element S2 (the upper terminal of the upper switching element), and the upper terminal of the coil L1 is connected to the terminal T3 (the upper terminal of the upper arm circuit). The power supply circuit 25 operates in the same manner as the power supply circuits 10 and 20.

  According to the power supply circuit 25 according to the present modification, as in the first and second embodiments, the switching loss due to the recovery current of the diode D1 is reduced in the booster circuit that controls the pulse width modulation of the switching element S1. be able to. Further, when the switching element S1 changes to the ON state, the potential of the drain terminal of the switching element S2 changes with a delay from the potential of the drain terminal of the switching element S1 due to the action of the coil L1. For this reason, when the recovery current of the built-in diode B2 of the switching element S2 flows, the voltage across the switching element S1 is already sufficiently small (preferably almost zero). Therefore, switching loss due to the recovery current of the built-in diode B2 of the switching element S2 can also be reduced.

  In the power supply circuit 20, the coil L1 is provided on the source side of the switching element S2. In the power supply circuit 25, the coil L1 is provided on the drain side of the switching element S2. However, coils are provided on the drain side and the source side of the switching element S2. A provided power supply circuit may be configured.

(Third embodiment)
FIG. 9 is a circuit diagram of a power supply circuit according to the third embodiment of the present invention. A power supply circuit 30 shown in FIG. 9 is a step-down chopper circuit including switching elements S1 and S2, coils L0 and L2, a diode D2, an input capacitor C1, and an output capacitor C2. Hereinafter, differences from the first embodiment will be described, and description of points in common with the first embodiment will be omitted.

  The power supply circuit 30 has a configuration in which a coil L2 and a diode D2 are added to a step-down chopper circuit having switching elements S1, S2 and a coil L0. For the diode D2, for example, FRD or SiC SBD is used. The power supply circuit 30 steps down the voltage input from the terminals T1 and T2, and outputs the stepped down voltage from the terminals T3 and T4.

  One terminal (upper terminal) of the coil L2 is connected to the source terminal of the switching element S2 and the cathode terminal of the diode D2. The other terminal (lower terminal) of the coil L2 is connected to the drain terminal of the switching element S1 and one terminal (left terminal in FIG. 9) of the coil L0. The other terminal of the coil L0 (the right terminal in FIG. 9) is connected to the terminal T3. The drain terminal of the switching element S2 is connected to the terminal T1. The source terminal of the switching element S1 and the anode terminal of the diode D2 are connected to the terminals T2 and T4.

  Thus, in the power supply circuit 30, the switching element S1 is provided in the lower arm circuit, and the switching element S2 and the coil L2 (current limiting coil) are provided in the upper arm circuit. One terminal of the coil L0 is connected to the arm connection point. The coil L2 is provided in series with the switching element S1 (lower switching element) between the source terminal of the switching element S2 (lower terminal of the upper switching element) and the terminal T2 (lower terminal of the lower arm circuit). It is done. The upper terminal of the coil L2 is connected to the source terminal of the switching element S2, and the lower terminal of the coil L2 is connected to the arm connection point. The diode D2 passes through the path connecting the source terminal of the switching element S2 and the terminal T2 without passing through the switching element S1 and the coil L2, and has the anode terminal on the terminal T2 side and the cathode terminal of the source terminal of the switching element S1. It is provided on the side.

  Control signals CS1 and CS2 are supplied to the gate terminals of the switching elements S1 and S2, respectively. In the present embodiment, the control signal CS2 is a PWM signal having a predetermined duty ratio, and the control signal CS1 is a signal that changes complementarily to the control signal CS2. However, a first dead time is provided between the time when the control signal CS2 changes to the low level and the time when the control signal CS1 changes to the high level, and the control signal CS2 changes after the control signal CS1 changes to the low level. A second dead time is provided until the level changes to a high level.

  The power supply circuit 30 operates in the same manner as the power supply circuit 10. Hereinafter, the current flowing through the coil L2 is IL2, the current flowing through the switching element S1 is IS1, the forward voltage of the diode D2 is Vf2, and the potential of the terminal T3 is Vout.

  When the switching element S1 is in the off state and the switching element S2 is in the on state, current flows through the switching element S2 and the coils L2 and L0 between the terminals T1 and T2, and energy is stored in the coils L0 and L2. . Next, the switching element S2 changes from the on state to the off state. After the switching element S2 changes to the complete OFF state, the entire current IL2 becomes a current passing through the diode D2.

  Next, after the first dead time, the switching element S1 changes from the off state to the on state. After the switching element S1 changes to the ON state, a current passing through the diode D2 and the coil L2 and a current passing through the switching element S1 flow through the coil L0. Since the current flowing through the switching element S1 flows through the low-resistance channel region, the drain potential of the switching element S1 becomes the reference potential (0 V) as is the case with the source potential of the switching element S1. Since the anode potential of the diode D2 is lower than the cathode potential by the forward voltage, the cathode potential of the diode D2 becomes (−Vf2). Therefore, when the upward direction is positive in FIG. 9, the voltage across the coil L2 is (−Vf2). Since a negative voltage is applied across the coil L2, the current IL2 decreases. Current IS1 increases by a decrease in current IL2.

  Next, after the current IL2 becomes sufficiently small (preferably, after the current IL2 becomes substantially zero), the switching element S1 changes from the on state to the off state. Next, after the second dead time, the switching element S2 changes from the off state to the on state. Thus, the switching element S2 changes from the off state to the on state while the current flows through the built-in diode B1 of the switching element S1. When the switching element S2 is turned on, the source potential of the switching element S2 immediately rises to the power supply potential (the potential of the terminal T1). On the other hand, the drain potential of the switching element S1 does not rise immediately due to the current limiting action of the coil L2. A current corresponding to the voltage across the coil L2 gradually flows through the coil L2. Therefore, the current passing through the coil L2 and the switching element S2 starts to flow after the change of the switching element S2 to the ON state.

  After a while, the current IS1 stops flowing. Along with this, the drain potential of the switching element S1 rises, and the recovery current of the built-in diode B1 of the switching element S1 flows to the switching element S2. However, when the recovery current begins to flow, the source potential of the switching element S2 has already risen (preferably almost increased to the power supply potential), and the drain-source voltage of the switching element S2 has already been sufficiently high. It is small (preferably almost zero). For this reason, the switching loss resulting from the recovery current of the built-in diode B1 of the switching element S1 is small.

  When the switching element S2 changes from the off state to the on state, the recovery current of the diode D2 flows to the switching element S2. However, when the switching element S1 changes from the off state to the on state, the current that has been flowing to the diode D2 until then flows to the switching element S1, and the current that flows to the diode D2 decreases. Thus, since the recovery phenomenon occurs when the current flowing through the diode D2 is small, the recovery current of the diode D2 is small and the switching loss due to the recovery current of the diode D2 is also small.

  According to the power supply circuit 30 according to the present embodiment, the switching loss due to the recovery current of the diode D2 and the recovery current of the built-in diode B1 of the switching element S1 is reduced for the step-down circuit that performs pulse width modulation control of the switching element S2. can do.

(Fourth embodiment)
FIG. 10 is a circuit diagram of a power supply circuit according to the fourth embodiment of the present invention. The power supply circuit 40 shown in FIG. 10 is obtained by changing the position where the coil L2 is provided in the power supply circuit 30 according to the third embodiment. In the power supply circuit 30, the coil L2 is provided in the same arm circuit (upper arm circuit) as the switching element S2 subjected to pulse width modulation control. The upper terminal of the coil L2 is connected to the source terminal of the switching element S2, and the lower terminal of the coil L2 is connected to the arm connection point.

  On the other hand, in the power supply circuit 40 according to the present embodiment, the coil L2 is provided in an arm circuit (lower arm circuit) different from the switching element S2 that is subjected to pulse width modulation control. The upper terminal of the coil L2 is connected to the arm connection point, and the lower terminal of the coil L2 is connected to the drain terminal of the switching element S1 (upper terminal of the lower switching element). The power supply circuit 40 operates in the same manner as the power supply circuit 30.

  According to the power supply circuit 40 according to the present embodiment, as in the third embodiment, the recovery current of the diode D2 and the built-in diode B1 of the switching element S1 of the step-down circuit that performs pulse width modulation control of the switching element S2 Switching loss due to the recovery current can be reduced.

  FIG. 11 is a block diagram showing a configuration of a power supply circuit according to a modification of the fourth embodiment of the present invention. The power supply circuit 45 shown in FIG. 11 is obtained by changing the position where the coil L2 is provided in the power supply circuit 30 according to the third embodiment. In the power supply circuit 45, the coil L2 is provided in an arm circuit different from the switching element S2 that is subjected to pulse width modulation control. The upper terminal of the coil L2 is connected to the source terminal (lower terminal of the lower switching element) of the switching element S1, and the lower terminal of the coil L2 is connected to the terminal T2 (lower terminal of the lower arm circuit). The power supply circuit 45 operates in the same manner as the power supply circuits 30 and 40.

  According to the power supply circuit 45 according to the present modification, as in the third and fourth embodiments, the switching loss due to the recovery current of the diode D2 is reduced in the step-down circuit that controls the pulse width modulation of the switching element S2. be able to. When the switching element S2 changes to the on state, the potential of the source terminal of the switching element S1 changes later than the potential of the source terminal of the switching element S2 due to the action of the coil L2. For this reason, when the recovery current of the built-in diode B1 of the switching element S1 flows, the voltage across the switching element S2 is already sufficiently small (preferably almost zero). Therefore, the switching loss due to the recovery current of the built-in diode B1 of the switching element S1 can also be reduced.

  In the power supply circuit 40, the coil L2 is provided on the drain side of the switching element S1, and in the power supply circuit 45, the coil L1 is provided on the source side of the switching element S1, but coils are provided on the drain side and the source side of the switching element S1. A provided power supply circuit may be configured.

(Fifth embodiment)
In the fifth embodiment, a power supply device including a plurality of power supply circuits according to the first to fourth embodiments will be described. FIG. 12 is a circuit diagram of a power supply device according to the fifth embodiment of the present invention. A power supply device 50 shown in FIG. 12 is an inverter including two power supply circuits 10 according to the first embodiment. The power supply device 50 includes switching elements S1a, S2a, S1b, S2b, coils L0a, L1a, L0b, L1b, diodes D1a, D1b, input capacitors C1a, C1b, and a smoothing capacitor C3. The power supply device 50 includes terminals T1a to T3a and T1b to T3b for external connection. A DC power source 1a is connected to the terminals T1a and T2a, a DC power source 1b is connected to the terminals T1b and T2b, and an AC load 3 is connected as an output load to the terminals T3a and T3b. A reference potential is applied to the terminals T2a and T2b. DC power supplies 1a and 1b output the same level of voltage.

  One terminal (lower terminal) of the coil L1a is connected to the drain terminal of the switching element S1a and the anode terminal of the diode D1a. The other terminal (upper terminal) of the coil L1a is connected to the source terminal of the switching element S2a and one terminal (left terminal in FIG. 12) of the coil L0a. The other terminal (the right terminal in FIG. 12) of the coil L0a is connected to the terminal T3a. The drain terminal of the switching element S2a and the cathode terminal of the diode D1a are connected to the terminal T1a. The source terminal of the switching element S1a is connected to the terminal T2a. The input capacitor C1a is provided between the terminals T1a and T2a.

  Switching elements S1b and S2b, coils L0b and L1b, diode D1b, and input capacitor C1b are connected in the same form as switching elements S1a and S2a, coils L0a and L1a, diode D1a, and input capacitor C1a. The smoothing capacitor C3 is provided between the terminals T3a and T3b. The power supply device 50 may not include the input capacitors C1a and C1b, and may not include the smoothing capacitor C3. Further, the terminal T1a and the terminal T1b may be shared, the terminal T2a and the terminal T2b may be shared, and a single power source may be connected between the two obtained terminals. In this case, the input capacitor C1a and the input capacitor C1b may be shared.

  Control signals CS1a, CS2a, CS1b, CS2b are applied to the gate terminals of the switching elements S1a, S2a, S1b, S2b, respectively. The power supply device 50 divides one AC cycle into the first half and the second half. In the first half of the cycle, the control signal CS1b is fixed at a low level, the control signal CS2b is fixed at a high level, and the control signal CS1a is a PWM signal. The control signal CS2a changes complementarily to the control signal CS1a. The switching element S2a is turned on during a part of the off period of the switching element S1a, and is otherwise turned off. The switching element S1a changes from the off state to the on state while a current flows through the built-in diode B2a of the switching element S2a. At this time, since the potential of the terminal T3a is lower than the potential of the terminal T3b, the current flows from the terminal T3b to the terminal T3a via the AC load 3 (to the left in FIG. 12). The duty ratio of the control signal CS1a changes similarly to the half cycle of the sine wave. Accordingly, the voltage applied to the AC load 3 in the first half of the cycle changes in the same manner as in the half cycle of the sine wave.

  In the second half of the cycle, the control signal CS1a is fixed at a low level, the control signal CS2a is fixed at a high level, and the control signal CS1b is a PWM signal. Control signal CS2b changes complementarily to control signal CS1b. The switching element S2b is turned on during part of the off period of the switching element S1b, and is otherwise turned off. The switching element S1b changes from the off state to the on state while a current flows through the built-in diode B2b of the switching element S2b. At this time, since the potential of the terminal T3a is higher than the potential of the terminal T3b, the current flows from the terminal T3a to the terminal T3b via the AC load 3 (rightward in FIG. 12). The duty ratio of the control signal CS1b changes similarly to the half cycle of the sine wave. Therefore, the voltage applied to the AC load 3 in the second half of the cycle changes in the same manner as in the half cycle of the sine wave. In this way, the power supply device 50 drives the AC load 3 in two phases.

  As described above, the power supply device 50 performs the pulse width modulation control of the switching element S1a in the first half of the cycle, and performs the pulse width modulation control of the switching element S1b in the second half of the cycle. In either the first half of the cycle or the second half of the cycle, the pulse width changes in the same manner as the sine wave. Therefore, according to the power supply device 50, a voltage that changes in a sine wave shape can be generated to drive the AC load 3 in two phases.

  Further, according to the power supply device 50, similarly to the first embodiment, the recovery current of the diodes D1a and D1b and the switching loss due to the built-in diodes B2a and B2b of the switching elements S2a and S2b can be reduced. . Thus, switching loss can be reduced for a power supply device including a plurality of power supply circuits.

  A power supply device 50 shown in FIG. 12 is an inverter that includes two power supply circuits 10 and performs two-phase driving. In the same manner, an inverter that includes three power supply circuits 10 and performs three-phase driving can be configured. An inverter that performs three-phase driving is used, for example, for driving a motor. In addition, an inverter that includes a plurality of power supply circuits according to the first to fourth embodiments or the modifications thereof and performs multi-phase driving can be configured by the same method.

(Sixth embodiment)
FIG. 13 is a circuit diagram of a power supply device according to the sixth embodiment of the present invention. A power supply device 60 shown in FIG. 13 is obtained by adding coils L2a and L2b, diodes D2a and D2b, and current limiting circuits X1a, X2a, X1b, and X2b to the power supply device 50 according to the fifth embodiment. is there. Hereinafter, differences from the fifth embodiment will be described, and descriptions of points common to the fifth embodiment will be omitted.

  One terminal (lower terminal) of the coil L1a is connected to the drain terminal of the switching element S1a and the anode terminal of the diode D1a. The other terminal (upper terminal) of the coil L1a is connected to one terminal (lower terminal) of the coil L2a and one terminal (left terminal in FIG. 13) of the coil L0a. The other terminal (upper terminal) of the coil L2a is connected to the source terminal of the switching element S2a and one terminal (upper terminal in FIG. 13) of the current limiting circuit X2a. The other terminal (the right terminal in FIG. 13) of the coil L0a is connected to the terminal T3a. The cathode terminal of the diode D1a is connected to one terminal (the lower terminal in FIG. 13) of the current limiting circuit X1a. The drain terminal of the switching element S2a and the other terminal (the upper terminal in FIG. 13) of the current limiting circuit X1a are connected to the terminal T1a. The other terminal (the lower terminal in FIG. 13) of the current limiting circuit X2a is connected to the cathode terminal of the diode D2a. The source terminal of the switching element S1 and the anode terminal of the diode D2a are connected to the terminal T2a.

  Switching elements S1b, S2b, coils L0b-L2b, diodes D1b, D2b, input capacitors C1b, and terminals T1b, T2b are switching elements S1a, S2a, coils L0a-L2a, diodes D1a, D2a, input capacitors C1a, and It is connected in the same form as the terminals T1a and T2a. The current limiting circuits X1a, X2a, X1b, and X2b include, for example, a resistance element, a diode, a series body of a plurality of diodes, or a circuit in which these are connected in series (see FIGS. 6A and 6B).

  Control signals CS1a, CS2a, CS1b, CS2b are applied to the gate terminals of the switching elements S1a, S2a, S1b, S2b, respectively. The power supply device 60 divides one AC cycle into the first half and the second half. In the first half of the cycle, the control signals CS1a and CS2b become PWM signals, the control signal CS2a changes complementarily to the control signal CS1a, and the control signal CS1b changes complementarily to the control signal CS2b. The switching element S2a is turned on during a part of the off period of the switching element S1a, and is otherwise turned off. The switching element S1a changes from the off state to the on state while a current flows through the built-in diode B2a of the switching element S2a. The switching element S1b is turned on during a part of the off period of the switching element S2b, and is turned off otherwise. The switching element S2b changes from the off state to the on state while a current flows through the built-in diode B1b of the switching element S1b.

  In the second half of the cycle, the control signals CS2a and CS1b become PWM signals, the control signal CS1a changes complementarily to the control signal CS2a, and the control signal CS2b changes complementarily to the control signal CS1b. The switching element S1a is turned on during a part of the off period of the switching element S2a, and is turned off otherwise. The switching element S2a changes from the off state to the on state while a current flows through the built-in diode B1a of the switching element S1a. The switching element S2b is turned on during part of the off period of the switching element S1b, and is otherwise turned off. The switching element S1b changes from the off state to the on state while a current flows through the built-in diode B2b of the switching element S2b.

  Thus, in one power supply circuit (left power supply circuit in FIG. 13; hereinafter referred to as a first power supply circuit) included in the power supply device 60, the lower arm circuit is provided with the switching element S1a and the coil L1a, and the upper arm circuit. Are provided with a switching element S2a and a coil L2a. One terminal of the coil L0a is connected to the arm connection point. The lower terminal of the coil L1a is connected to the drain terminal of the switching element S1 (the upper terminal of the lower switching element), and the upper terminal of the coil L1a is connected to the arm connection point. The lower terminal of the coil L2a is connected to the arm connection point, and the upper terminal of the coil L2a is connected to the source terminal of the switching element S2 (lower terminal of the upper switching element). The diode D1a has an anode terminal on the first path connecting the drain terminal of the switching element S1a and the terminal T1a (upper terminal of the upper arm circuit) without passing through the switching element S2a and the coils L1a and L2a. The cathode terminal is provided on the drain terminal side with the terminal T1a side. The current limiting circuit X1a is provided in series with the diode D1a on the first path. The diode D2a has an anode terminal connected to the terminal T2a on the second path connecting the source terminal of the switching element S2a and the terminal T2a (lower terminal of the lower arm circuit) without passing through the switching element S1a and the coils L1a and L2a. On the other side, the cathode terminal is provided with the source terminal side of the switching element S2a. The current limiting circuit X2a is provided in series with the diode D2a on the second path.

  In the first power supply circuit, the switching element S1a is subjected to pulse width modulation control, the switching element S1b is turned on in a part of the off period of the switching element S1a, and the switching element S1b has a pulse width. The modulation is controlled, and the switching element S1a has a second half (second period) of a cycle in which the switching element S1a is turned on in a part of the off period of the switching element S1b. In the first half of the cycle, the switching element S1a changes from the off state to the on state while the current flows through the built-in diode B1b of the switching element S1b. While the current is flowing, the state changes from the off state to the on state.

  Thus, the power supply device 60 performs pulse width modulation control of the switching elements S1a and S2b in the first half of the cycle, and performs pulse width modulation control of the switching elements S1b and S2a in the second half of the cycle. According to the power supply device 60, by performing pulse width modulation control of the two switching elements, the generated voltage can be brought close to a sine wave, and the AC load 3 can be more accurately driven in two phases.

  Further, according to the power supply device 60, as in the fifth embodiment, the recovery current of the diodes D1a, D2a, D1b, D2b and the built-in diodes B1a, B2a, B1b of the switching elements S1a, S2a, S1b, S2b, Switching loss due to B2b can be reduced. Thus, switching loss can be reduced for a power supply device including a plurality of power supply circuits.

  Hereinafter, the effect of providing the current limiting circuits X1a, X2a, X1b, and X2b in the power supply device 60 will be described. Here, as a comparative example, consider a circuit (fourth comparative example) in which the current limiting circuits X1a and X1b are deleted from the first power supply circuit.

  In the power supply circuit according to the fourth comparative example, it is assumed that the switching element S1a changes from the off state to the on state while a current flows through the built-in diode B2a of the switching element S2a. At this time, the recovery current of the built-in diode B2a of the switching element S2a flows through the coil L2a, and the recovery current and the current passing through the coil L0a flow through the coil L1a and the switching element S1a (see FIG. 14A). In particular, when a super junction MOSFET is used as the switching element S2a, a charging current of the capacitance between the source and drain of the switching element S2a also flows.

  When a recovery current or a charging current flows through the coil L2a, energy is accumulated in the coil L2a. For this reason, even after the switching element S1a is turned on, a circulating current continues to flow through the diode D2a, the coils L2a, L1a, and the switching element S1a (see FIG. 14B). Since a circulating current larger than the current flowing through the coil L0a flows to the switching element S1a, the switching element S1a generates more heat than necessary, and heat dissipation becomes difficult. Further, the switching loss when the switching element S1a changes from the on state to the off state also increases.

  On the other hand, consider a case where the first power supply circuit of the power supply device 60 is provided with current limiting circuits X1a and X2a including resistance elements. In this case, the circulating current passing through the diode D2a, the coils L2a and L1a, and the switching element S1a is converted into thermal energy by the resistance element in the current limiting circuit X2a and decreases. Similarly, the circulating current passing through the diode D1a, the switching element S2a, and the coils L2a and L1a is also converted into thermal energy by the resistance element in the current limiting circuit X1a and decreases. Therefore, according to the first power supply circuit having the current limiting circuits X1a and X2a, the circulating current passing through the switching element S1a and the diode D2a and the circulating current passing through the switching element S2a and the diode D1a are reduced, and the switching element S1a The amount of heat generated in S2a can be reduced.

  In addition, the features of each embodiment described above can be arbitrarily combined as long as they do not contradict their properties, and a power supply device and a power supply circuit having features of a plurality of embodiments can be configured.

  As described above, according to the power supply circuit and the power supply device of the present invention, switching loss can be reduced.

10, 15, 20, 25, 30, 40, 45 ... power supply circuit 50, 60 ... power supply device S1 ... switching element (lower switching element)
S2: Switching element (upper switching element)
L0 ... coil L1, L2 ... coil (current limiting coil)
D1, D2 ... Diode C1 ... Input capacitor C2 ... Output capacitor C3 ... Smoothing capacitor X1, X2 ... Current limiting circuit

Claims (10)

A lower switching element provided in the lower arm circuit;
An upper switching element provided in the upper arm circuit;
A coil with one terminal connected to the arm connection point;
When one of the lower side and the upper side is the first side and the other is the second side, the second side is between the second side terminal of the first side switching element and the second side terminal of the second side arm circuit. A current limiting coil provided in series with the switching element;
A diode provided on a path connecting the second side terminal of the first side switching element and the second side terminal of the second side arm circuit without passing through the second side switching element and the current limiting coil; With
The first side switching element is subjected to pulse width modulation control,
The second side switching element is turned on during a part of the off period of the first side switching element, and is otherwise turned off.
The power supply circuit according to claim 1, wherein the first side switching element changes from an off state to an on state while a current flows through a built-in diode of the second side switching element. The first side is the lower side, the second side is the upper side,
A lower terminal of the current limiting coil is connected to an upper terminal of the lower switching element;
The upper terminal of the current limiting coil is connected to the arm connection point,
The diode is provided on the path with an anode terminal on an upper terminal side of the lower switching element and a cathode terminal on an upper terminal side of the upper arm circuit. The power supply circuit described in 1. The first side is the lower side, the second side is the upper side,
The lower terminal of the current limiting coil is connected to the arm connection point,
An upper terminal of the current limiting coil is connected to a lower terminal of the upper switching element;
The diode is provided on the path with an anode terminal on an upper terminal side of the lower switching element and a cathode terminal on an upper terminal side of the upper arm circuit. The power supply circuit described in 1. The first side is the lower side, the second side is the upper side,
A lower terminal of the current limiting coil is connected to an upper terminal of the upper switching element;
An upper terminal of the current limiting coil is connected to an upper terminal of the upper arm circuit;
The diode is provided on the path with an anode terminal on an upper terminal side of the lower switching element and a cathode terminal on an upper terminal side of the upper arm circuit. The power supply circuit described in 1. The first side is the upper side, the second side is the lower side,
An upper terminal of the current limiting coil is connected to a lower terminal of the upper switching element;
The lower terminal of the current limiting coil is connected to the arm connection point,
The diode is provided on the path with an anode terminal on a lower terminal side of the lower arm circuit and a cathode terminal on a lower terminal side of the upper switching element. Item 2. The power supply circuit according to Item 1. The first side is the upper side, the second side is the lower side,
The upper terminal of the current limiting coil is connected to the arm connection point,
A lower terminal of the current limiting coil is connected to an upper terminal of the lower switching element;
The diode is provided on the path with an anode terminal on a lower terminal side of the lower arm circuit and a cathode terminal on a lower terminal side of the upper switching element. Item 2. The power supply circuit according to Item 1. The first side is the upper side, the second side is the lower side,
An upper terminal of the current limiting coil is connected to a lower terminal of the lower switching element;
A lower terminal of the current limiting coil is connected to a lower terminal of the lower arm circuit;
The diode is provided on the path with an anode terminal on a lower terminal side of the lower arm circuit and a cathode terminal on a lower terminal side of the upper switching element. Item 2. The power supply circuit according to Item 1.   The power supply circuit according to claim 1, further comprising a current limiting circuit provided in series with the diode on the path. A lower switching element provided in the lower arm circuit;
An upper switching element provided in the upper arm circuit;
A coil with one terminal connected to the arm connection point;
A first current limiting coil having a lower terminal connected to the upper terminal of the lower switching element and an upper terminal connected to the arm connection point;
A second current limiting coil having a lower terminal connected to the arm connection point and an upper terminal connected to the lower terminal of the upper switching element;
An anode terminal on a first path connecting the upper terminal of the lower switching element and the upper terminal of the upper arm circuit without passing through the upper switching element, the first current limiting coil and the second current limiting coil; A first diode provided on the upper terminal side of the lower switching element and a cathode terminal on the upper terminal side of the upper arm circuit;
A first current limiting circuit provided in series with the first diode on the first path;
On the second path connecting the lower terminal of the upper switching element and the lower terminal of the lower arm circuit without passing through the lower switching element, the first current limiting coil, and the second current limiting coil A second diode provided with an anode terminal on the lower terminal side of the lower arm circuit and a cathode terminal on the lower terminal side of the upper switching element;
A second current limiting circuit provided in series with the second diode on the second path;
A first period in which the lower switching element is subjected to pulse width modulation control, the upper switching element is turned on in a part of an off period of the lower switching element, and the upper switching element is subjected to pulse width modulation control, A second period in which the lower switching element is turned on in a part of the off period of the upper switching element,
In the first period, the lower switching element changes from an off state to an on state while a current flows through a built-in diode of the upper switching element,
In the second period, the upper switching element changes from an off state to an on state while a current flows through a built-in diode of the lower switching element.   The power supply device provided with two or more power supply circuits in any one of Claims 1-9.

Images