JP2002369508A - Dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC-DC converter that can reduce electromagnetic noise and surface voltages, and that can be simplified in circuit configuration and control action. SOLUTION: When a transistor Q1 is turned off, an auxiliary LC circuit 400 suppresses the potential drop at a junction C of the output terminal of the transistor Q1, by discharging the energy stored during the turned-on period of the transistor Q1 to the junction C. Consequently, the switching loss of transistor Q and surge noise can be reduced, because the potential difference (voltage drop) between both terminals of the transistor Q, when the transistor Q1 is in a turned off state is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a DC-DC converter.

[0002]

2. Description of the Related Art Conventional chopper type (including synchronous rectification type)
2. Description of the Related Art In DC-DC converter technology, there is known a DC-DC converter in which an auxiliary switching element is used to reduce a current during a switching transition period of a main switching element to reduce a switching loss.

[0003]

However, the conventional DC-DC converter with an auxiliary switching element has a problem that the circuit configuration is complicated and the control of the added auxiliary switching element is not easy.

In other words, the current and voltage of each part of the circuit must be sensed as control parameters, and each switch must be precisely intermittently controlled based on the detected and detected control parameters, which complicates the circuit configuration and lowers economic efficiency. There was a problem. There is also a problem that electromagnetic noise and surge voltage accompanying switching are large.

The present invention has been made in view of the above problems, and has as its object to provide a DC-DC converter capable of reducing electromagnetic noise and surge voltage and simplifying circuit configuration and control operation. I have.

[0006]

A DC-D according to claim 1.
The C converter is connected to a main choke coil having an output terminal electrically connected to the higher output terminal, and an input-side higher power supply line on the input side electrically connecting the higher input terminal and the input terminal of the main choke coil. A DC switch comprising: a series switch provided for intermittently controlling an input current; and a parallel switch for electrically connecting a lower power supply line to which a lower input terminal and a lower output terminal are connected and the input terminal of the main choke coil.
-In the DC converter, a sub-choke coil interposed between the series switch and the main choke coil in the input-side high-level power supply line, and a second end electrically connected to a connection end of the two choke coils. One capacitor,
An anode is connected to the lower power supply line, a cathode is electrically connected to the other end of the first capacitor, and a second diode is connected to the lower power supply line. A connection point between the sub-choke coil and the series switch, a second diode whose anode is electrically connected to the other end of the second capacitor, a cathode of the first diode, and an anode of the second diode. An auxiliary LC circuit having an electrically connected third diode is provided.

[0007] The DC-DC converter according to claim 2 is
The main choke coil whose output terminal is electrically connected to the higher output terminal, and the input which is provided on the input side higher power supply line on the input side which electrically connects the higher input terminal and the input terminal of the main choke coil. A series switch for intermittently controlling the current;
A DC-DC converter comprising a low-level power supply line to which a low-level input terminal and a low-level output terminal are connected, and a parallel switch for electrically connecting the input terminal of the main choke coil, wherein one end has the series switch and the main choke. A second choke coil having the other end connected to the lower power supply line through the parallel switch at a connection point with the coil, and a first end electrically connected to a connection point between the series switch and the both choke coils at the other end. A capacitor, a first diode having an anode electrically connected to the other end of the first capacitor, a cathode electrically connected to an input terminal of the series switch, and one end electrically connected to an input terminal of the series switch. A second capacitor, an anode is provided at a connection point between the sub choke coil and the parallel switch, and a cathode is provided at the second capacitor. A second diode electrically connected to the other end thereof, and an auxiliary LC circuit having a third diode electrically connecting the anode of the first diode and the cathode of the second diode. I have.

These inventions have the following features in common.

In other words, each invention discharges the electromagnetic energy stored in the sub-choke coil to the output terminal of the series switch through a diode and a capacitor when the series switch is off, thereby turning on or off the series switch. To suppress the undesired potential change at the time. This reduces switching loss and surge noise of the series switch.

To explain further, the largest component of the loss of the chopper type DC-DC converter is switching loss,
In particular, it is the switching loss of the series switch. Along with this switching loss, surge voltage and electromagnetic wave noise superimposed on the power supply voltage also increase. In these inventions,
The energy stored in the auxiliary LC circuit is used for reducing the switching loss of the series switch when the series switch is turned off through the diode. This enables ZCS and ZVS when the series switch is off, simplifies the circuit configuration over the entire load range of the DC-DC converter, and improves efficiency and reliability.

The "main choke coil" referred to in the invention of each of the above structures may be an inductance element in an electric circuit, and may be, for example, a motor winding. In each of the above inventions, a diode chopper type DC-DC converter may be configured using a diode as a two-terminal switch as a parallel switch, and a synchronous rectification type DC using a transistor as a three-terminal switch as a parallel switch.
-A DC converter may be configured. The term “electrically connect” as used in the present specification includes a connection via some circuit element, for example, a resistance element, other than a direct connection. In each configuration of the present invention, the direction of the DC power supply may be reversed if the direction of the diode is reversed.

According to the configuration of the second aspect, the above effect can be obtained not only at the time of step-down but also at the time of step-up.

According to the third aspect of the present invention, in the DC-DC converter according to the first or second aspect, the sub choke coil has an inductance smaller than that of the main choke coil. As a configuration, a conductor pattern can be formed on a printed circuit board, and the device can be manufactured, so that downsizing can be achieved.

According to a fourth aspect of the present invention, in the DC-DC converter according to any one of the first to third aspects, since the capacitors have substantially equal capacities, the electromagnetic energy accumulated in the sub choke coil is further reduced. When transferring to a capacitor, stored energy loss due to the difference in capacitance between the two capacitors can be reduced, and power transfer efficiency can be improved.

According to a fifth aspect of the present invention, the DC-DC converter according to any one of the first to fourth aspects is further characterized in that the parallel switch comprises a diode as a two-terminal switch. The control can be further simplified.

According to a sixth aspect of the present invention, in the DC-DC converter according to any one of the first to fifth aspects, the parallel switch further includes a transistor as a three-terminal switch, and a two-terminal connected in anti-parallel to the transistor. Since it is characterized by comprising a flywheel diode as a switch, the switching loss of the parallel switch can be reduced.

In a preferred embodiment of the present invention, the transistor is turned on when a potential at a connection point between the main choke coil and the transistor as the parallel switch is lower than a predetermined value with respect to the lower power supply line. I do. Thereby, the switching loss of the parallel switch can be further reduced.

In a preferred embodiment of each of the inventions described above, the on-timing (Z
VS, ZCS timing) and an on-timing determined based on a comparison between the output voltage of the DC-DC converter and the reference output voltage. It is useful in terms of simplicity. Further, the same effect is obtained by detecting a quantity of electricity linked to the current of the sub choke coil and turning on a transistor as a parallel switch when the current of the sub choke coil becomes a predetermined value or less based on the quantity of electricity. Can play.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the DC-DC converter according to the present invention will be described in detail with reference to the following embodiments. In each of the embodiments described below, if the direction of the diode is reversed, the direction of the input-side DC power supply E may be reversed.

[0020]

Embodiment 1 (Circuit Configuration) FIG. 1 shows a circuit configuration of a DC-DC converter of this embodiment.

E is a high-voltage input-side DC power supply, C1, C2,
C3 and C4 are capacitors, Q1 is a series switch composed of transistors, Q2 is a parallel switch composed of transistors, D1, D2, D3, D4 and D5 are diodes, L
1, L2 is a choke coil, RL is a load resistance element (may be a low-voltage DC power supply), and 100 is a transistor Q1, Q2.
Is a controller for controlling the intermittent operation.

Capacitors C3 and C4, choke coil L
2. Diodes D3, D4, and D5 are auxiliary Ls referred to in the present invention.
The C circuit 400 is configured.

The capacitor C1 is a smoothing capacitor connected in parallel with the input side DC power supply E, and the capacitor C2 is a smoothing capacitor connected in parallel with the load resistance element RL.

A diode D1 is a flywheel diode connected in anti-parallel with the transistor Q1, a diode D2.
Is a flywheel diode connected in anti-parallel with the transistor Q2. Note that the transistor Q2 as a parallel switch can be omitted. In this case, the diode D3 as a two-terminal switch connected in antiparallel with the transistor Q2 constitutes the parallel switch referred to in the present invention.

Choke coil (main choke coil) L1
Is connected to the higher end of the load resistance element RL. The input terminal A of the choke coil L1 is connected to the higher end of the input DC power supply through the choke coil (sub choke coil) L2 and the transistor (series switch) Q1 sequentially. Reference numeral 200 denotes an input-side high power supply line, and 300 denotes a low power supply line. Transistor (parallel switch) Q
2 connects the input terminal of the main choke coil L1 and the lower power supply line 300.

Choke coil (sub choke coil) L
2, capacitors C3, C4, diodes D3, D4, D
Reference numeral 5 denotes an auxiliary LC circuit according to the present invention, and diodes D3, D4, and D5 constitute a partial resonance control switch as a two-terminal switch.

The choke coil L2 is connected to the transistor Q1
And the choke coil L1. Capacitor (first capacitor) C
One end of 3 is connected to the connection point A of the choke coils L1 and L2, and the other end is grounded to the lower power line 300 through a diode (first diode) D3. The anode of the diode D3 is connected to the lower power supply line 300.

One end of the capacitor (second capacitor) C4 is grounded to the lower power supply line 300, and the other end is connected to a connection point between the transistor Q1 and the choke coil L2 through a diode (second diode) D4. B is the higher input terminal of the circuit.

The anode of the diode (third diode) D5 is connected to the cathode of the diode D3, and the cathode of the diode D5 is connected to the anode of the diode D4. The capacitances of the capacitors C3 and C4 are set equal. (Operation) The operation of the above circuit will be described below with reference to the circuit diagram of FIG. 1 and the timing chart of FIG. In the following description, a diode chopper type circuit that does not use the transistor Q2 will be described. (Description of Operation) The operation of this DC-DC converter will be described below with reference to the timing chart shown in FIG. In the following description of the operation, the basic operation of the DC-DC conversion will be described first, and then the operation of this auxiliary LC circuit will be described. (Basic operation) If the auxiliary LC circuit 400 is ignored, this D
The C-DC converter is the same as a normal DC-DC converter.

In step-down power transmission from the high-voltage power supply E to the low-voltage power supply E2, the transistors Q1 and Q2 are turned on alternately.
When the transistor Q1 is turned on, low-voltage power is supplied to the low-voltage power supply E2 while storing electromagnetic energy in the choke coil L1, and this electromagnetic energy is supplied to the low-voltage power supply E2 through the diode D2 (or the transistor Q2) by turning off the transistor Q1. (Operation of auxiliary LC circuit) When the transistor Q1 is turned on, the choke coil L2 stores electromagnetic energy.
The capacitors C3 and C4 are connected through the choke coil L2, the capacitor C3, the diode D5, and the capacitor C4.
Is charged.

The capacitors C3 and C4 and the choke coil L2 connected in series form a series resonance circuit through the diode D5. When the resonance proceeds for a half cycle, the diode D
4. Due to D5, the capacitor C3 cannot be discharged, and the resonance stops. That is, the capacitors C3 and C4 perform only the charging operation during the ON period of the transistor Q1.

When the transistor Q1 is turned off, the choke coil L1 tries to maintain its current state, so that the potential at the node A tends to decrease. Choke coil L2
Tries to raise the potential of the connection point A in order to maintain the current state, and tries to decrease the potential of the connection point C.
However, the potential drop at the connection point A is effectively suppressed because the capacitor C3 discharges to the connection point A through the diode D3, and accordingly, the potential drop at the connection point C is suppressed. Further, the capacitor C4 discharges to the connection point C through the diode D4 when the potential of the connection point C drops, and the connection point C
To prevent the potential from dropping.

That is, when the transistor Q1 is turned off, the auxiliary LC circuit releases the energy accumulated during the on-period of the transistor Q1 to the connection point C, which is the output terminal of the transistor Q1, and the potential of the connection point C drops. Deter. Thus, the potential difference (voltage drop) between both ends of the transistor Q1 when it is off is reduced, so that the switching loss of the transistor Q and the surge noise can be reduced.

After the emission of the electromagnetic energy from the choke coil L2 is completed, the transistor Q1 maintains a predetermined OFF state. Thereafter, when the emission of the electromagnetic energy to the load resistance RL of the choke coil L1 through the diode D2 attenuates to a predetermined level. , The transistor Q1 turns on, and the above operation is repeated.

When the transistor Q1 is turned on, the potential at the connection point C, which is the output terminal, is changed to the choke coil L1,
Since the voltage is raised by the back electromotive force of L2, the potential difference (voltage drop) between both ends of the transistor Q1 is small (the current of the transistor Q1 is small), and its switching loss and surge noise are suppressed.

As a result, the auxiliary LC circuit of this embodiment has an effect of reducing switching loss and surge noise of the transistor Q1 when the transistor Q1 is off.

Next, waveforms of respective parts when the capacitances of the capacitors C3 and C4 are equal and not equal will be described below with reference to FIGS. FIG. 6 shows C3 = C4.
7 shows the case where C3> C4, and FIG. 8 shows the case where C3 <C4. As can be seen from FIGS. 6 to 8, C3> C4
In the case of, the charge that could not be stored in C3 becomes
4, power loss occurs, and in the case of C3 <C4, electric charge that has not been extracted from the capacitor C2 is consumed through the diode D3, resulting in power loss. That is, it is understood that the regeneration of resonance energy can be performed most efficiently when the capacitances of the capacitors C3 and C4 are equal.

[0038]

Embodiment 2 Embodiment 2 will be described below with reference to FIG.

In this embodiment, a synchronous rectification type DC-DC converter is obtained by operating the transistor Q2 in the first embodiment.

As in the ordinary synchronous rectification type DC-DC converter, the transistor Q2 is turned on and off alternately with the transistor Q1 to assist the electromagnetic energy discharge of the choke coil L1. That is, the transistor Q2
Is turned on when the transistor Q1 is turned off, and suppresses the potential drop at the connection point A due to the emission of electromagnetic energy from the choke coil L1.

Turning off transistor Q2 (transistor Q
Since the auxiliary LC circuit 400 suppresses the rise in the potential at the connection point A at the time of 1 (ON), the voltage drop when the transistor Q2 is OFF is reduced, and the switching loss and surge noise are reduced.

[0042]

Embodiment 3 Embodiment 3 will be described with reference to the circuit diagram of FIG. This circuit is obtained by applying the auxiliary LC circuit of the present invention to a DC-DC converter capable of bidirectional power transmission between the high-voltage battery E and the low-voltage battery E2. Therefore, a low-voltage DC power supply E2 is employed instead of the load resistance element RL.

(Circuit Configuration) This embodiment is characterized in that an auxiliary LC circuit 500 is used instead of the auxiliary LC circuit 400 shown in FIG.

The auxiliary LC circuit 500 includes a capacitor C5,
C6, choke coil L2, diodes D6, D7, D
8. The choke coil (sub choke coil) L2 includes the choke coil L1 and the transistor Q2.
It is interposed between and.

One end of the capacitor C5 is connected to the transistor Q1.
The diode D6 is connected to a connection point between the transistor Q2 and the choke coil L2 and a capacitor C5.
Is connected to the other end.

One end of the capacitor C6 is connected to the transistor Q1.
The diode D7 connects the other end of the capacitor C6 to the input terminal of the transistor Q1.

The anode of the diode D8 is a diode D8.
6 and the cathode of the diode D8 is connected to the anode of the diode D7. (Explanation of Operation) FIG.
This will be described below with reference to the timing chart of FIG.
However, in this embodiment, the transistor Q2 is operated. In the following description of operation, first, DC-DC
The basic operation of conversion will be described, and then the operation of this auxiliary LC circuit will be described. (Basic operation) If the auxiliary LC circuit 500 is ignored, this D
The C-DC converter is the same as a normal DC-DC converter.

In step-down power transmission from the high-voltage power supply E to the low-voltage power supply E2, the transistors Q1 and Q2 are turned on alternately. When the transistor Q1 is turned on, the choke coil L1
Power is supplied to the low-voltage power supply E2 while the electromagnetic energy is stored in the low-voltage power supply E2 through the diode D2 (or the transistor Q2) and the choke coil L2 when the transistor Q1 is turned off. The behavior of the choke coil L2 will be described later. In this step-down power transmission, it is appropriate that the on-time of the transistor Q1 is longer than the on-time of the transistor Q2, and the on-time of the transistor Q2 is turned on for a time corresponding to emission of the stored electromagnetic energy of the choke coil L1.

In step-up power transmission from the low-voltage power supply E2 to the high-voltage power supply E, the transistors Q1 and Q2 are turned on alternately. When the transistor Q2 is turned on, the choke coil L1
To store electromagnetic energy. This electromagnetic energy is supplied to the high voltage power supply E through the diode D1 (or the transistor Q1) when the transistor Q2 is turned off. The behavior of the choke coil L2 will be described later. In this step-up power transmission, the on-time of the transistor Q2 is longer than the on-time of the transistor Q1, and it is appropriate that the on-time of the transistor Q1 is turned on for a time corresponding to the release of the stored electromagnetic energy of the choke coil L1. Obviously, it is possible to omit the transistor Q2 in the step-down operation and omit the transistor Q1 in the step-up operation. (Operation of Auxiliary LC Circuit) (Step-Up Operation) First, step-up power transmission from the low-voltage power supply E2 to the high-voltage power supply E will be described below.

When the transistor Q2 is turned on and the transistor Q1 is turned off, current flows from the low voltage power supply E2 through the choke coils L1, L2 and the transistor Q2, and electromagnetic energy is stored in the choke coils L1, L2.

When the transistor Q2 is turned off and the transistor Q1 is turned on, the current flowing from the low-voltage power supply E2 to the transistor Q2 through the choke coil L1 increases the amount of electromagnetic energy accumulated in the choke coil L1 by energizing the transistor Q2. Power is supplied to the high-voltage battery E through the transistor Q1. At this time, the potential rise at the connection point A is regulated by the diode D1.

When the transistor Q2 is turned off, the stored electromagnetic energy of the choke coil L2 raises the potential of the connection point X and lowers the potential of the connection point A in order to maintain conduction. As a result, a current flows from the connection point X through the diodes D6, D8, and D7, the rise in the potential of the connection point X is regulated, and the capacitor C5 is charged. Thereby, switching loss and surge noise when the transistor Q2 is off are reduced.

The rise of the potential at the node X prevents the potential at the node A from lowering through the diodes D6 and D8 and the capacitor C6, and charges the capacitor C6. When the transistor Q1 is turned off, the stored power of the capacitor C6 is returned to the input terminal of the transistor Q1 through the diode D7 and is regenerated.

(Step-down operation) The transistor Q2 is turned off,
When the transistor Q1 is on, the choke coil L2 does not store any electromagnetic energy.

Considering the switching transition period of the transistors Q1 and Q2, immediately after the transistor Q1 is turned on, the choke coil L1 generates a back electromotive force to suppress the current of the transistor Q1 and reduce the switching loss of the transistor Q1. I do. Immediately after the transistor Q1 is turned off, the choke coil L1 tries to keep energizing to dissipate its electromagnetic energy, and as a result, the potential at the connection point A tends to decrease. However, this potential drop is caused by the capacitors C5 and C6 through the diode D8.
And the voltage drop (potential difference between both ends) of the transistor Q1 when the transistor Q1 is turned off is reduced by that amount. Therefore, switching loss and surge noise in the off transition period of the transistor Q1 are reduced. After that, the charge of the capacitor C6 is returned to the input terminal of the transistor Q1, that is, the high-voltage power supply E together with the potential recovery of the connection point A.

Immediately after the transistor Q2 is turned off, the stored electromagnetic energy of the choke coil L2 tries to lower the potential at the connection point X, but this potential drop is clamped by the diode D2.

FIG. 4 shows the waveforms of the respective parts during the above-described boosting operation, and FIG. 5 shows the waveforms of the respective parts during the above-described step-down operation.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a DC-DC converter according to a first embodiment.

FIG. 2 is a timing chart showing waveforms at various points in the DC-DC converter according to the first embodiment.

FIG. 3 is a circuit diagram illustrating a DC-DC converter according to a third embodiment.

FIG. 4 is a timing chart showing waveforms of respective parts when boosting a DC-DC converter according to a third embodiment.

FIG. 5 is a timing chart showing waveforms of respective parts when stepping down the DC-DC converter according to the third embodiment.

FIG. 6 shows a DC-DC converter (C3 = C
It is a timing chart which shows each part waveform of 4).

FIG. 7 shows a DC-DC converter (C3> C) according to the first embodiment.
It is a timing chart which shows each part waveform of 4).

FIG. 8 shows a DC-DC converter according to the first embodiment (C3 <C
It is a timing chart which shows each part waveform of 4).

[Explanation of symbols]

 L1 Choke coil (Main choke coil) B High input terminal 200 Input high power line Q1 Transistor (Series switch) 300 Low power line Q2 Transistor (Parallel switch) L2 Choke coil (Sub choke coil) C3 Capacitor (First capacitor) D3 Diode (first diode) C4 capacitor (second capacitor) D4 diode (second diode) D5 diode (third diode) 400 auxiliary LC circuit C5 capacitor (second capacitor) C6 capacitor (first capacitor) D7 diode (first diode) Diode) D6 Diode (second diode) D8 Diode (third diode) 500 Auxiliary LC circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshihiko Sugiura 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Shigeo Hirashima 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Denso Corporation (72) Inventor Hiroshi Matsumae 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation (72) Inventor Yuji Hayashi 14 Iwatani, Shimoba-Kakucho, Nishio-shi, Aichi Prefecture F-term in Japan Automotive Parts Research Institute, Inc. (Reference) 5H730 AA02 AA14 AA16 AS04 AS05 AS13 BB13 BB14 BB57 BB65 BB66 BB86 DD02 DD12 DD13 DD32 DD41

Claims (6)

[Claims] 1. A main choke coil having an output terminal electrically connected to a high-level output terminal, and an input-side high-level power supply line on an input side electrically connecting a high-level input terminal and an input terminal of the main choke coil. A series switch interposed to intermittently control the input current; and a parallel switch electrically connecting a lower power supply line to which a lower input terminal and a lower output terminal are connected, and the input terminal of the main choke coil. In the DC-DC converter, a sub-choke coil provided between the series switch and the main choke coil in the input-side high-level power supply line, and one end is electrically connected to a connection end of the two choke coils. A first capacitor, a first diode having an anode electrically connected to the lower power supply line and a cathode electrically connected to the other end of the first capacitor, respectively; A second capacitor having an end electrically connected to the lower power supply line; a cathode electrically connected to a connection point between the sub choke coil and the series switch; and an anode electrically connected to the other end of the second capacitor. A DC-DC converter, comprising: an auxiliary LC circuit having: a second diode; and a third diode that electrically connects a cathode of the first diode and an anode of the second diode.
DC converter. 2. A main choke coil having an output terminal electrically connected to a high-level output terminal, and an input-side high-level power supply line on an input side electrically connecting a high-level input terminal to an input terminal of the main choke coil. A series switch interposed to intermittently control the input current; and a parallel switch electrically connecting a lower power supply line to which a lower input terminal and a lower output terminal are connected, and the input terminal of the main choke coil. In the DC-DC converter, one end is connected to the connection point between the series switch and the main choke coil, the other end is connected to the lower power supply line through the parallel switch, and one end is connected to the series switch and the main choke coil. A first capacitor electrically connected to a connection point with the choke coil; an anode connected to the other end of the first capacitor; and a cathode connected to the series switch. A first diode electrically connected to the input terminal of the series switch, a second capacitor having one end electrically connected to the input terminal of the series switch, and an anode connected to the sub choke coil and the parallel switch. At a connection point, a second diode whose cathode is electrically connected to the other end of the second capacitor, respectively, and a third diode that electrically connects the anode of the first diode and the cathode of the second diode. DC-, comprising an auxiliary LC circuit having:
DC converter. 3. The DC-DC converter according to claim 1, wherein the sub choke coil has an inductance smaller than that of the main choke coil.
C converter. 4. The DC-D according to claim 1, wherein
In the C converter, the two capacitors have substantially the same capacity. 5. The DC-D according to claim 1, wherein:
In the C converter, the parallel switch includes a diode serving as a two-terminal switch. 6. The DC-D according to claim 1, wherein
In the C converter, the parallel switch includes a transistor serving as a three-terminal switch, and a flywheel diode serving as a two-terminal switch connected in anti-parallel to the transistor.