JP2013027162A - Dc power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce switching loss and diode loss specifically to achieve a higher frequency operation of a semiconductor switch, in a DC power supply device in which input and output are electrically insulated by a transformer.SOLUTION: A DC power supply device includes: a DC power supply (101); a power conversion circuit (Q1-Q4) capable of generating AC from DC; a transformer (T) including a primary winding connected to the output of the power conversion circuit; a rectification diode bridge circuit (D5-D8) connected to a secondary winding of the transformer (T) via a resonance reactor (Lz); and a filter circuit (102) comprising a filter reactor (LD) and a filter capacitor (FC) and connected to the output side of the rectification diode bridge circuit. In the DC power supply device, a circuit element (SR) is provided on the input side of the rectification diode bridge circuit, the circuit element having low impedance in a current direction until just before the occurrence of recovery of rectification diodes (D5-D8) comprising the rectification diode bridge circuit, and having high impedance in the reverse direction of the current direction.

Description

  The present invention relates to an insulation type DC-DC converter, and in particular, in a circuit having a function of reducing semiconductor switching loss by resonance of a reactor L and a capacitor C, suppression of fluctuation in voltage and loss reduction generated in a diode of a rectifier circuit. It is about.

  A DC-DC converter is used when stabilizing an unstable DC power supply, changing a DC voltage, or outputting a DC power supply that is electrically insulated from the input. Among them, in a DC power supply device in which the input and the output are electrically insulated, the transformer used for insulation is downsized in proportion to the increase in the switching frequency used. On the other hand, there is a limit to the increase in switching frequency due to heat generation due to switching loss of the semiconductor switch. In order to reduce such switching loss, there is a technique called soft switching provided with a commutation circuit using a resonance circuit. As such soft switching, prior art in which a commutation circuit is provided on the secondary side of a transformer is described in Patent Document 1 and Non-Patent Document 1 below.

FIG. 2 shows the configuration of a circuit having a commutation circuit described in these known examples.
101 is an input DC power source, 102 is a filter circuit composed of a filter reactor Ld and a filter capacitor FC, 103 is a resonance circuit, and 104 is a gate control unit for controlling on / off of each semiconductor switch.
The circuit operation of FIG. 2 will be described. Semiconductor switches Q1 to Q4 connected to the input DC power supply 101 are semiconductor switches constituting an inverter circuit, and free wheel diodes D1 to D4 are connected in parallel to the semiconductor switches Q1 to Q4, respectively. A primary winding of the transformer T is connected between a connection point a between the semiconductor switches Q1 and Q2 and a connection point b between the semiconductor switches Q3 and Q4, and the secondary winding is connected to the rectifier diode via the resonance reactor Lz. It is connected to the connection point c and the connection point d of the rectification bridge composed of D5 to D8. The output of this rectification bridge is given to the load RL via the filter circuit 102.
The resonant switch circuit 103 is inserted between the output side of the rectifier bridge and the filter circuit 102.

The gate control unit 104 gives ON / OFF commands to the semiconductor switches Q1 to Q4 and the resonance circuit control semiconductor switch Qz. As these semiconductor switches, bipolar transistors, MOSFETs, thyristors, gate turn-off thyristors, IGBTs, and the like can be considered. Here, IGBTs will be described as typical examples.
FIG. 3 shows the time change of the operation waveform for explaining the conventional example of FIG. Iab is a current flowing between the connection points a and b, Vab is a voltage between the connection points a and b, Iz is a current flowing in the resonance circuit, and Vz is a voltage across the resonance capacitor Cz. Vr represents the voltage across the diode D5 constituting the rectifier bridge, and Ir represents the forward current of the diode D5.

The circuit operation will be described using the above symbols.
In FIG. 2, it is assumed that ON signals are given from the gate control device 104 to the semiconductor switches Q1 and Q4, and the semiconductor switches Q1 and Q4 of the inverter circuit are in a conductive state. When the current Iab flows through the primary winding of the transformer T, energy is transmitted from the DC power supply 101 to the load RL via the transformer T, the resonant reactor Lz, the rectifier bridge, and the filter circuit 102.
When a signal for turning on the resonant circuit control semiconductor switch Qz of the resonant switch circuit 103 is given from the gate control device 104 at time t0 before the semiconductor switches Q1 and Q4 of the inverter circuit are turned off, the charging current of the resonant capacitor Cz is input. It flows from the DC power supply 101. This charging current becomes the series resonance current Iz of the resonance reactor Lz and the resonance capacitor Cz.

Here, the current Iab flowing through the semiconductor switches Q1 and Q4 is the sum of the current Id flowing through the load side and the series resonance current Iz when the turns ratio of the transformer T is 1: 1, and increases in a sine wave shape. The current Ir of the rectifier diode D5 has the same waveform. At this time, a voltage Vz is generated in the resonance capacitor Cz, and the voltage Vz becomes higher than the secondary voltage of the transformer T due to resonance between the resonance reactor Lz and the resonance capacitor Cz.
At time t1, charging of the resonance capacitor Cz is completed, and the voltage Vz reaches the maximum value. Thereafter, discharge of the resonance capacitor Cz starts, and a discharge current flows out as a series resonance current Iz through a path between the free wheel diode D9 and the resonance capacitor Cz. Since the turns ratio of the transformer T is 1: 1, the current Id to the filter reactor Ld flows so as to be constant as the sum of the current Iab and the series resonance current Iz, and the current Iab decreases as the series resonance current Iz increases. Will do.

  At time t2, the series resonance current Iz and the current Id become equal, and the current Iab becomes 0 at this time. As the discharge progresses, the resonance capacitor Cz is completely discharged at time t4, and the series resonance current Iz becomes zero. At time t3 during this period, the semiconductor switches Q1 and Q4 are turned off. On the other hand, since the current Id flowing through the filter reactor Ld is a continuous value, when the discharge current Iz of the resonant capacitor Cz becomes 0, the current Id switches to the current from the rectifier diodes D5 to D8 and flows. At this time, since the current Id is the sum of the diode current Ir flowing through the diode D5 and the current Io flowing through the diode D7, the value of the diode current Ir flowing through the diode D5 is half the value of Id. The continuity of is maintained.

  At time t3 between time t2 and t4 when the series resonance current Iz flows through the freewheel diode D9 and the transformer primary current Iab becomes 0, a turn-off signal is sent from the gate control device 104 to the semiconductor switches Q1 and Q4. Is turned off, the transformer primary side voltage Vab becomes 0, and a voltage equal to the input DC power supply voltage E is applied to the semiconductor switches Q1 and Q4. This is because a slight amount of the exciting current of the transformer freewheels along the path of the diode D3, the DC power supply 101, and the diode D2. Since the currents of the semiconductor switches Q1 and Q4 become almost zero at the time t3, almost no switching loss occurs in the process of turning off the semiconductor switches Q1 and Q4.

  On the other hand, when the semiconductor switch Qz is turned on at time t0, the time rate of change of the resonance current Iz is limited by the resonance reactor Lz, and the series resonance current Iz gradually increases. Is small. Further, when the semiconductor switch Qz is turned off while the free wheel diode D9 is conducting and the series resonance current Iz is positive, the current of Qz is already 0, so that no switching loss occurs during the turn-off process.

  At time t5, the gate control device 104 issues a turn-on command to the semiconductor switches Q2 and Q3 to start turn-on. At this time, the current Id flowing through the filter reactor Ld is equal to the current Ir circulating through the rectifier diodes D5 to D8. At this time, since the current Iab starts to flow through the resonant reactor Lz by turning on the semiconductor switches Q2 and Q3, it cannot increase rapidly, and since the current Id can be considered constant, the sum of the current Iab and the current Ir is Id It changes to become. Therefore, the current Iab increases as the current Ir decreases, and almost no current flows in the turn-on transient state of the semiconductor switches Q2 and Q3. For this reason, the turn-on loss is small. The current Iab gradually increases, becomes equal to the current Id at time t6, and the current Ir becomes zero. For the subsequent half cycle from time t0 'to time t6', the paired arms (semiconductor switches Q2 and Q3) operate on the same principle as described above.

FIG. 4 shows waveforms of the voltage Vr and current Ir of the rectifier diode D5 when the circuit shown in FIG. 2 is actually operated. In FIG. 4, times corresponding to times t0 to t6 in FIG. 3 are clearly shown.
FIG. 3 in an ideal case is compared with FIG. 4 which is an actually measured waveform. In the ideal voltage waveform at time t2 and t6 when the diode current Ir flowing in the forward direction becomes zero, no surge (bounce) occurs in the ideal FIG. 3, but when the actual operation waveform in FIG. It can be seen that a surge voltage is generated at the time.
In an ideal diode, the current value is obtained when the diode is reverse-biased or the forward current decreases due to other effects from the state where the current is flowing forward between the anode and the cathode. Even if becomes zero, it does not flow in the reverse direction.

  However, in an actual diode, if the current is stopped or becomes zero for the above reason from the state in which the forward current is flowing between the anode and the cathode, the current between the PN junction is reduced. Since it takes a certain amount of time for the accumulated minority carriers to disappear, a reverse surge current flows during this time. This phenomenon is called recovery (reverse recovery), and it is apparent from the fact that the current Ir instantaneously flows in the negative direction when the time t2 and t6 in FIG.

  A surge voltage is generated in the reverse direction between the terminals of the diode by the recovery current which is the reverse surge current. Further, the product of the above-described recovery current and this surge voltage is a recovery loss, and this is treated as a switching loss of the diode. In addition, if this surge voltage exceeds the reverse withstand voltage of the diode, the diode may break down, causing a rapid change in time, causing high-frequency electromagnetic noise and adversely affecting other devices. There is also.

As a countermeasure against such a diode recovery phenomenon, as described in Patent Document 2, a CR snubber is generally attached to each rectifier diode. In Patent Documents 2 and 3, a saturable reactor is introduced into each rectifier diode.
The purpose of these prior arts is to suppress the generation of electromagnetic noise due to surge voltage.
The RC snubber is used to absorb the energy generated by the snubber circuit when the surge voltage is generated and suppress the generation of the surge voltage. The introduction of the saturable reactor is a reverse surge that generates a recovery phenomenon. By suppressing the generation of current and delaying the disappearance of minority carriers inside the diode, the recovery itself is delayed, and the surge voltage is suppressed.

JP-A-4-368464 Japanese Patent Laid-Open No. 10-262371 JP 2002-223568 A

O. Deblecker, A Moretti, and F. Vallee: “Comparative Analysis of Two Zero-Current Switching Isolated DC-DCConverters for Auxiliary Railway Supply,” SPEEDAM 2008.

Now, using the voltage Vr and current Ir of the rectifier diode D5 shown in FIG. 4 which is the result of actually operating the circuit, the loss generated in the recovery at times t6 and t2 is calculated to be about 110 W, respectively. And 50W.
Judging from the current flowing through the rectifier diode D5, the recovery of the rectifier diode D5 that occurs at time t6 occurs as an operation of the DC-DC converter regardless of the presence or absence of the resonant switch circuit 103, but the recovery at time t2 is primary. It is generated by flowing a resonance current for reducing the switching loss generated in the semiconductor switches Q1 to Q4 on the side and reducing the primary side current Iab to only the exciting current of the transformer T.
That is, by introducing the resonant switch circuit 103, the turn-off loss of the primary-side semiconductor switch can be greatly reduced, but new recovery loss is added to the rectifier diode bridges D5 to D8 connected to the secondary side of the transformer T. Will occur. In the above operation example, the recovery loss increases by about 1.5 times depending on the presence or absence of the resonant switch circuit 103. This means that the operating frequency of the DC-DC converter itself is limited by the heat generated by the rectifier diode bridge.

As described above, the recovery of the rectifying diode generated at time t2 becomes a new problem in the DC-DC converter having the soft switching function as shown in FIG.
Here, when the surge voltage values generated at times t6 and t2 in FIG. 4 are viewed, it can be seen that there is a difference between them. This is probably because the two types of recovery that occur in the secondary-side rectifier diode bridge are different.
First, consider the recovery that occurs at time t6. Until just before time t5, the load current Id is circulating through the rectifier diodes D5 to D8. Since the primary side semiconductor switches Q2 and Q3 are turned on at time t5, a voltage is generated between the terminals of the transformer T, and a reverse bias is applied to the rectifier diodes D5 and D8. Therefore, the current Ir decreases from the time t5 to the time t6 as the current Iab of the transformer T increases. Thereafter, at time t6, the current Ir reaches zero, and the voltage Vr is generated. This operation is a typical operation of “recovery”, and this recovery may occur when a reverse bias is applied to the rectifier diode constituting the secondary rectifier diode bridge directly from the primary side via the transformer T. I understand.

  Next, consider the recovery that occurs at time t2. The current Ir flowing through the rectifier diode D5 from the time t1 to the time t2 decreases with the sum of the resonance current Iz and the load current Id, and the current Iz gradually increases, so that the current Ir becomes zero at the time t2. To reach. At this time, since the current Iab flowing into the transformer T from the primary side also becomes zero, energy from the primary side is not supplied, but the current continues to flow due to the inductance of the current path through which the current Ir flows. Recovery occurs when a reverse surge current corresponding to the carrier disappearance flows.

  As described above, recovery at which the reverse bias is forcibly applied from the primary side occurs at the time t6, and the current disappears spontaneously, and the recovery at the time t2 occurs only with the magnetic energy stored in the wiring inductance. . In other words, this means that the energy for generating recovery at time t6 is large and that it is small at time t2. That is, since the energy of recovery at time t2 is about the magnetic energy due to the inductance of the current path through which the current Ir flows, recovery loss can be suppressed without adding a large-capacity energy absorbing element. is there.

  Therefore, in the present invention, the current flows so that the direction of the current Ir does not change abruptly, especially at the time t2 (and t2 ′ when Iab becomes zero after the semiconductor switches Q2 and Q3 are turned on at t5). An object of the present invention is to provide a DC power supply device in which recovery loss is reduced at time t2 (and t2 ′) by introducing a circuit element having a small impedance in the direction and a large impedance in the opposite direction.

Therefore, the following technical means have been taken in the special flow power supply device of the present invention. That is,
(1) A DC power source, a power conversion circuit capable of generating AC from DC, a transformer whose primary winding is connected to the output of the power conversion circuit, and a secondary winding of the transformer via a resonant reactor A resonant circuit comprising a connected rectifier diode bridge circuit, a filter circuit composed of a filter reactor and a filter capacitor and connected to the output side of the rectifier diode bridge circuit, and a freewheeling diode (D9) connected in antiparallel A resonant switch circuit (103) including a circuit control semiconductor switch (Qz) and a resonant capacitor (Cz) is connected in parallel to the output side of the rectifier diode bridge, so that the resonant reactor (Lz) and the resonant switch circuit are connected. In the DC power supply device that forms a series resonant circuit with the resonant capacitor (Cz) of (103), the rectifier diode On the primary or secondary side of the transformer connected to the input side of the bridge circuit, the impedance is low in the current direction until the recovery of the rectifier diode constituting the rectifier diode bridge circuit occurs, and in the opposite direction Provided circuit elements with high impedance.

(2) In the DC power supply device described above, a saturable reactor is used as the circuit element.

(3) In the DC power supply device described above, the saturable reactor is arranged on a lower voltage side of the primary voltage and secondary voltage of the transformer.

(4) In the above DC power supply device, the circuit element has a function of reducing the switching loss of the semiconductor switch constituting the power conversion circuit connected to the primary side of the transformer.

(5) In the DC power supply device described above, the semiconductor switch is turned off when the current flowing through the semiconductor switch constituting the power conversion circuit becomes almost zero.

(6) The on / off control of the semiconductor switch constituting the power conversion circuit and the semiconductor switch for resonance circuit control in the DC power supply device described above is controlled by a gate control device.

(7) In the DC power supply device described above, the resonance reactor is configured by the sum of the leakage inductance of the transformer and its wiring inductance.

According to the present invention, in the transformer-insulated DC-DC converter, the recovery of the rectifier diode constituting the rectifier diode bridge circuit can be performed on the primary side or the secondary side of the transformer connected to the input side of the rectifier diode bridge circuit. By providing a circuit element with low impedance for the current direction up to just before generation and high impedance in the opposite direction, the switching loss of the primary-side semiconductor switch is reduced and the transformer secondary-side rectifier diode is used. An excellent effect of reducing loss due to the generated recovery can be achieved.
This means that the waste heat of the DC-DC converter is reduced, and not only energy saving by improving efficiency and downsizing of the cooling device, but also downsizing of the transformer can be realized by increasing the driving frequency. This contributes to the improvement of reliability and reliability.

1 shows a first embodiment of a DC power supply device according to the present invention. The circuit structure of a prior art example is shown. The ideal voltage current in a prior art example and the time change of semiconductor switch command are shown. 2 shows measured waveforms of the voltage Vr and current Ir of the rectifier diode D5 in the configuration of FIG. The magnetic characteristic (BH curve) of the saturable reactor used in Example 1 of this invention is shown. The waveform which expanded the time t2 vicinity of FIG. 4 measured with the circuit of the prior art example is shown. FIG. 7 shows waveforms when the embodiment of the present invention is applied to the operation circuit of FIG. As a second embodiment of the present invention, a circuit in the case where the primary side semiconductor switch is constituted by a half bridge is shown. The example of the saturable reactor SR used in Example 1, 2 of this invention is shown.

The present invention solves the problem that the loss of the rectifier diode increases due to the current generated by the circuit that reduces the turn-off loss of the primary side semiconductor switch, but has the effect of reducing the total recovery loss of the rectifier diode.
Embodiments of the present invention will be described below with reference to the drawings.

[Example 1]
First, as Embodiment 1 of the present invention, its configuration and operation principle will be described with reference to FIG.
101 is an input DC power source, 102 is a filter circuit composed of a filter reactor Ld and a filter capacitor FC, 103 is a resonance circuit, and 104 is a gate control device for each semiconductor switch. Q1 to Q4 are semiconductor switches constituting an inverter circuit, and free wheel diodes D1 to D4 are attached to the respective semiconductor switches. A primary winding of the transformer T is connected between a connection point a between the semiconductor switches Q1 and Q2 and a connection point b between the semiconductor switches Q3 and Q4, and the secondary winding is a rectifier diode bridge composed of rectifier diodes D5 to D8. Are connected to connection points c and d. The output of this rectifier diode bridge is given to the load RL via the filter circuit 102.

The gate control device 104 gives ON / OFF commands to the semiconductor switches Q1 to Q4 and the semiconductor switch Qz in the resonance circuit 103. As the semiconductor switch, a bipolar transistor, a MOSFET, a thyristor, a gate turn-off thyristor, an IGBT, and the like can be considered. In this embodiment, an IGBT will be described as a representative example.
In the configuration shown in FIG. 1, the sum of the leakage inductance of the transformer T and the inductance due to the wiring is described as a resonance reactor Lz, and a series resonance circuit is configured together with the resonance capacitor Cz of the resonance circuit 103.
A resonance circuit 103 including a capacitor Cz that can be controlled by the semiconductor switch Qz is connected in series to the output sides e and f of the rectifier diodes D5 to D8. More specifically, the resonance circuit 103 is a circuit in which a semiconductor switch Qz to which a free wheel diode D9 is connected in antiparallel and a resonance capacitor Cz are connected in series. The resonance circuit 103 is inserted in parallel with the rectifier diode bridge circuit between the output side of the rectifier diode bridge and the filter circuit 102.

Here, the turn ratio of the transformer T is N: 1 (N is a natural number not including zero), and the primary side voltage V1 is greater than or equal to the secondary side voltage V2. In addition, in this embodiment, a saturable reactor SR is provided as a circuit element having a low impedance in the direction in which a current flows until just before recovery occurs in the rectifier diode and a high impedance in the opposite direction.
The operation of FIG. 1 is the same as FIG. 2, and the voltage / current waveforms are the same as those of FIG. 3 described in the technical background. Here, only the operation and effect of the saturable reactor SR will be described with reference to FIG. FIG. 5 shows the magnetic characteristics (BH curve) of the saturable reactor SR. In FIG. 5, B represents the magnetic flux density of the saturable reactor, and H represents the strength of the magnetic field.

  At time t5 ′, an ON signal is given from the control device 104 to the semiconductor switches Q1 and Q4 (see FIG. 3), and the semiconductor switches Q1 and Q4 of the inverter circuit become conductive, and points a and b that are primary sides of the transformer T A voltage equal to the power supply voltage E is generated in the voltage Vab between. At this time t5 ′, the operating point on the magnetic characteristics of the saturable reactor is near the point H3 in FIG. 5, and therefore, the saturable reactor SR can be regarded as a large inductance. Therefore, at the instant when the time t5 ′ is reached, the saturable reactor. In SR, a voltage equal to the voltage V2 generated on the secondary side of the transformer T is generated. Considering the current Iab at this time, compared with the conventional example of FIG. 2, it is equivalent to the case where the inductance value of the resonance reactor Lz is large, and therefore flows more slowly. Therefore, the turn-on loss generated by the semiconductor switches Q1 and Q4 on the primary side is further smaller than that in the case of FIG.

Here, the magnetic flux Φ of the saturable reactor SR can be expressed by Equation 1. In Equation 1, n represents the number of turns of the saturable reactor SR, and V represents a voltage generated in the saturable reactor SR. Equation 1 is based on Faraday's law of electromagnetic induction.

上記、数式１と数式２の関係から、可飽和リアクトルＳＲの磁束密度Ｂは、時間変化しない電圧Ｖに対して次の数式３の関係を持つ。すなわち、磁束密度Ｂは通過する面積が一定の時、電圧Ｖとその発生時間ｔに比例する。

Further, the magnetic flux Φ and the magnetic flux density B have the relationship of the following formula 2. In Equation 2, S indicates the area of the surface through which the magnetic flux density B passes, and n indicates the unit normal vector with respect to the area, but the right side of Equation 2 further indicates when the magnetic flux density B and the surface through which it passes are perpendicular. Show.

From the relationship between Equation 1 and Equation 2, the magnetic flux density B of the saturable reactor SR has the relationship of Equation 3 below with respect to the voltage V that does not change over time. That is, the magnetic flux density B is proportional to the voltage V and the generation time t thereof when the passing area is constant.

Thus, when the voltage V is generated in the saturable reactor SR, the magnetic flux density B increases as the time t elapses. At this time, the operating point of the saturable reactor shown in FIG. 5 moves from the point H3 to the point H1 through the point H0 from time t5 ′ to t6 ′.
At time t6 ′, the saturable reactor SR is saturated, and when the operating point reaches the point H1 in FIG. 5, the permeability of the saturable reactor SR becomes extremely small, so that the inductance of the saturable reactor is almost zero. It becomes. As described above, the saturable reactor has a low-impedance state with no inductance in the positive direction of the current Iab of the transformer T when the operating point on its magnetic characteristics exists around the point H1 in FIG. .

Eventually, at time t0, the resonance switch Qz is turned on and the resonance current flows through Iab. However, since the direction of the current does not change until time t2, the saturable reactor SR is in a low impedance state.
At time t2, as described in the background art, the current Ir instantaneously tries to flow in the reverse direction, but the saturable reactor SR has a large inductance with respect to the reverse current at this time, and is in a high impedance state. At this time, the saturable reactor SR generates a voltage in a direction that prevents the reverse current by releasing the magnetic energy stored at time t6 ′, and its operating point is based on Equation 3 at time t6 ′. Although moving from the upper point H1 toward the point H2, the energy that causes recovery at time t2 is small as described above, and therefore the operating point in FIG. 5 remains near the point H1. In addition, the recovery current does not flow in a surge state, the recovery current gradually flows out like the current Iab at time t6 ′, and the carrier of the rectifier diode D5 disappears slowly, so that no surge voltage is generated.

  FIG. 6 shows the voltage Vr and current Ir of the rectifier diode at time t2 when the operation test is performed with the circuit diagram of FIG. 2 without introducing the saturable reactor. As shown in the figure, it can be seen that a voltage is generated and a loss is generated when a recovery current in the reverse direction flows. FIG. 7 shows measurement results of the voltage Vr and current Ir in the circuit shown in FIG. 1 in which the saturable reactor according to the embodiment of the present invention is introduced. At the time of recovery of the rectifier diode, no current flows in the reverse direction and no recovery of surge current occurs, and the recovery ends, and then the voltage Vr slowly recovers.

Thereafter, the semiconductor switches Q3 and Q4 are turned on at time t5, and a voltage opposite to that at time t5 ′ is generated in the secondary side voltage V2 of the transformer T. At this time, energy is applied from the primary side in the same manner as at time t5 ′, and the current Iab gradually flows out by moving the operating point of the saturable reactor SR from the vicinity of the point H1 in FIG. 5 to the point H3 through the point H2. At time t6, the magnetic saturation occurs and the saturable reactor SR enters a low impedance state.
Since the paired arm of the primary side semiconductor switch operates from time t0 'to t5', the operation is repeated according to the same principle, only in the reverse direction of voltage and current from time t0 to t5.
Note that although recovery occurs in the rectifier diode at times t6 and t6 ′, the energy of this recovery is large because it is supplied from the primary side as described above, and the operating point of the saturable reactor is changed from points H1 to H3 (or its Until it is moved to the reverse), the surge current generated in the recovery can be suppressed, so there is some effect, but beyond that, the effect of the reactor is lost and the surge voltage and loss due to the recovery current are generated.

  According to the present invention, in the circuit of FIG. 2, a recovery loss of 110 W at time t6 and 50 W at time t2 in total of 160 W has occurred, but by introducing the saturable reactor SR of FIG. 80W and 0W at time t2, a total of 80W, and the effect of reducing the recovery loss by half is obtained.

[Example 2]
The present invention can also be realized in the form of FIG. This is an example in which the configuration of the semiconductor switch on the primary side is configured with a half bridge. As operations of the semiconductor switch of the power conversion circuit, the operations of the semiconductor switches Q1 and Q4 of FIG. 1 are handled by the semiconductor switch Q1 of FIG. 8, and similarly, the operations of the semiconductor switches Q2 and Q3 of FIG. The primary side of the transformer T is connected between the connection point a of the semiconductor switches Q1 and Q2 and the connection point b of the voltage dividing capacitors C1 and C2. The operation of reducing the switching loss, the operation of the saturable reactor SR, and the shape of the voltage / current waveform are the same as those in the first embodiment.
However, since the primary-side semiconductor switch is formed of a half bridge, the primary-side voltage V1 of the transformer T is E / 2. Therefore, unlike the first embodiment, a step-up transformer is used, and the turn ratio is 1: N (N is a natural number not including zero).

Therefore, when the transformer T is a step-up transformer having a turns ratio of 1: N, if the saturable reactor SR is introduced to the secondary side of the transformer T as in the first embodiment, it occurs in the saturable reactor SR when the rectifier diode is recovered. The voltage is higher than that in Example 1. According to Equation 3, since the time until the saturable reactor SR is saturated is shortened, the period of high impedance for suppressing the recovery surge current is shortened.
For this reason, the saturable reactor SR is introduced into the primary side which is a low voltage among the windings of the transformer T.

[Example 3]
FIG. 9 is a configuration example in which a saturable core made of a magnetic material in a ring shape is placed on the primary side of the transformer T as the saturable reactor SR shown in the first and second embodiments. Normally, the core having such a shape is used in a common mode (round-trip line) to prevent electromagnetic noise. However, in the present invention, an effect of suppressing the recovery loss of the rectifier diode can be obtained by using the normal mode.
Note that the points a and b in FIG. 9 correspond to the connection points a and b in FIGS. 1 to 8, respectively.

  As described above, according to the present invention, the input side of the rectifier diode bridge circuit of the DC power supply device has a low impedance for the current direction until the recovery of the rectifier diode occurs, and a high impedance for the reverse direction. By providing a circuit element with impedance, it is possible to effectively suppress the generation of surge voltage associated with recovery and reduce power loss without incurring cost increase, and prevent rectifier diode breakdown and electromagnetic noise generation. Therefore, it can be expected to be widely used as an energy saving measure means and a high reliability measure means of the DC power supply device.

DESCRIPTION OF SYMBOLS 101: DC power supply 102: Filter circuit 103: Resonance switch circuit 104: Gate control apparatus 105: Saturable core comprised with the ring-shaped magnetic material C1, C2: Voltage dividing capacitor Cz: Resonance capacitor D1-D4, D9: Freewheel diodes D5 to D8: Rectifier diode E: Input DC power supply voltage FC: Filter capacitor Ld: Filter reactor Lz: Resonance reactor Q1 to Q4: Semiconductor switch Qz: Semiconductor switch for resonance circuit control RL: Load SR: Saturable reactor T : Transformer V1: Primary voltage of transformer T V2: Secondary voltage of transformer T

Claims (7)

A DC power source, a power conversion circuit capable of generating AC from DC, a transformer having a primary winding connected to the output of the power conversion circuit,
A rectifier diode bridge circuit connected to the secondary winding of the transformer via a resonant reactor;
Comprising a filter reactor and a filter capacitor, and having a filter circuit connected to the output side of the rectifier diode bridge circuit,
A resonant switch control semiconductor switch (Qz) having a freewheeling diode (D9) connected in antiparallel and a resonant switch circuit (103) comprising a resonant capacitor (Cz) are connected in parallel to the output side of the rectifier diode bridge. By
In the DC power supply device that forms a series resonance circuit with the resonance reactor (Lz) and the resonance capacitor (Cz) of the resonance switch circuit (103),
Low impedance in the current direction until the recovery of the rectifier diode constituting the rectifier diode bridge circuit occurs on the primary side or secondary side of the transformer connected to the input side of the rectifier diode bridge circuit, A DC power supply device characterized in that a circuit element having a high impedance is provided in the reverse direction.   2. The DC power supply device according to claim 1, wherein a saturable reactor is used as the circuit element.   3. The DC power supply device according to claim 2, wherein the saturable reactor has a low voltage side among the primary side voltage and the secondary side voltage of the transformer so that the time in which the saturable reactor is in a high impedance state is short when the voltage is high. DC power supply device characterized by being arranged in   2. The DC power supply device according to claim 1, wherein the circuit element has a function of reducing a switching loss of a semiconductor switch constituting a power conversion circuit connected to a primary side of the transformer. .   5. The DC power supply device according to claim 1, wherein the semiconductor switch is turned off when a current flowing through the semiconductor switch constituting the power conversion circuit becomes almost zero. DC power supply.   6. The DC power supply device according to claim 1, wherein on / off control of the semiconductor switch constituting the power conversion circuit and the semiconductor switch for resonance circuit control is controlled by a gate control device. A direct current power supply device.   7. The DC power supply device according to claim 1, wherein the resonance reactor is configured by a total of a leakage inductance of the transformer and a wiring inductance thereof.

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