WO2013129288A1 - Synchronous rectification circuit and switching power source device comprising same - Google Patents

Synchronous rectification circuit and switching power source device comprising same Download PDF

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WO2013129288A1
WO2013129288A1 PCT/JP2013/054694 JP2013054694W WO2013129288A1 WO 2013129288 A1 WO2013129288 A1 WO 2013129288A1 JP 2013054694 W JP2013054694 W JP 2013054694W WO 2013129288 A1 WO2013129288 A1 WO 2013129288A1
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Prior art keywords
diode
switching element
rectifier circuit
synchronous rectifier
voltage
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PCT/JP2013/054694
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French (fr)
Japanese (ja)
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佐々木　正人
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シャープ株式会社
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33592—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Definitions

  • the present invention relates to a synchronous rectifier circuit and a switching power supply device including the same, and more particularly to a synchronous rectifier circuit including a diode and a switching power supply device including the same.
  • a synchronous rectifier circuit In a switching power supply, a synchronous rectifier circuit is often used to increase power conversion efficiency.
  • the synchronous rectifier circuit reduces power loss that occurs during the switching operation.
  • FIG. 4 is a circuit diagram showing a circuit configuration of a switching power supply device having a conventional synchronous rectifier circuit (Patent Document 1: Japanese Patent Application Laid-Open No. 2010-161868).
  • the switching power supply device is a resonant reset type forward converter.
  • the switching power supply device includes a transformer T, a main switching element Qp, a commutation switching element Qs, a rectifying switching element Q, a choke coil L, a capacitor C, an input power supply Vin, and an output terminal Vout.
  • the rectifying switching element Q includes a parasitic diode D.
  • the length of time that the reverse recovery current flows through the rectifying switching element Q (reverse recovery time) and the magnitude of the reverse recovery current are called reverse recovery characteristics of the rectifying switching element Q.
  • the reverse recovery characteristic is determined by the parasitic diode D of the rectifying switching element Q, which is an FET (Field Effect Transistor). If the reverse recovery characteristic of the parasitic diode D is poor, the reverse recovery time becomes long and the reverse recovery current increases. For this reason, the power loss which arises at the time of switching operation will increase. Therefore, a switching power supply device with high power conversion efficiency cannot be realized.
  • Patent Document 2 Japanese Patent Laid-Open No. 2004-201445 discloses a synchronous rectifier circuit that reduces power loss due to reverse recovery current.
  • FIG. 5 is a circuit diagram showing a circuit configuration of a resonant reset type forward converter 2 having a synchronous rectifier circuit different from the resonant reset type forward converter shown in FIG.
  • resonant reset type forward converter 2 is different from the resonant reset type forward converter shown in FIG. 4 in that synchronous rectifier circuit 20 is provided instead of rectifying switching element Q.
  • the resonant reset type forward converter 2 includes a transformer T, a main switching element Qp, a commutation switching element Qs, a synchronous rectifier circuit 20, a choke coil L, a capacitor C, an input power source Vin, and an output terminal Vout. Prepare.
  • the input power source Vin and the output terminal Vout are insulated by the transformer T.
  • the main switching element Qp is connected in series with the primary winding Np.
  • the commutation switching element Qs and the synchronous rectifier circuit 20 are connected in series with the secondary winding Ns.
  • the commutation switching element Qs and the synchronous rectification circuit 20 realize synchronous rectification in synchronization with the switching operation of the main switching element Qp.
  • the synchronous rectifier circuit 20 includes a rectifier switching element Q2, a resistor R2, and a diode D20.
  • the rectifying switching element Q2 is an FET. For this reason, the rectifying switching element Q2 has a parasitic diode D2.
  • the resistor R2 is connected in series with the rectifying switching element Q2.
  • the diode D20 is connected in parallel to the series circuit of the rectifying switching element Q2 and the resistor R2 in the direction in which the anode is connected to the source of the rectifying switching element Q2.
  • the choke coil L stores or releases energy according to the switching operation of the commutation switching element Qs and the synchronous rectification circuit 20.
  • One end of the choke coil L is connected to a connection point between the secondary winding Ns and the commutation switching element Qs.
  • the other end of the choke coil L is connected to one end of the output terminal Vout.
  • the other end of the output terminal Vout is connected to a connection point between the commutation switching element Qs and the synchronous rectification circuit 20.
  • the output terminal Vout outputs a voltage stabilized by the capacitor C and supplies power to the load.
  • the main switching element Qp When the main switching element Qp is turned on based on a control signal (not shown), the commutation switching element Qs is turned off and the rectification switching element Q2 is turned on by a synchronous rectification control signal (not shown) synchronized with the control signal.
  • a voltage is applied from the input power source Vin to the primary winding Np.
  • X Vin is induced.
  • a voltage is applied to the synchronous rectifier circuit 20 in the forward direction. For this reason, a current flows through the path of the secondary winding Ns, the choke coil L, the output terminal Vout, and the synchronous rectifier circuit 20, and power is supplied to the load.
  • a voltage (Ns / Np ⁇ Vin ⁇ Vout) is applied between the terminals of the choke coil L. Therefore, energy is accumulated in the choke coil L.
  • the diode D20 is not only required to have better reverse recovery characteristics than the parasitic diode D2.
  • the diode D20 is also required to have a higher breakdown voltage than the parasitic diode D2.
  • a diode generally has a trade-off relationship between breakdown voltage and reverse recovery characteristics. For this reason, if a diode having a good reverse recovery characteristic is used in order to reduce power loss due to the reverse recovery current, the withstand voltage is reduced.
  • the resonant reset type forward converter 2 can reduce the power loss generated during the switching operation. On the other hand, it is not possible to realize a switching power supply device having a high-voltage synchronous rectifier circuit.
  • the present invention has been made to solve the above-described problems, and has an object to provide a high-voltage synchronous rectifier circuit and a switching power supply device including the same that reduce power loss. To do.
  • a synchronous rectifier circuit includes a rectifying switching element, a first diode connected in parallel to the rectifying switching element, a rectifying switching element, and a first diode. And a second diode connected in series to the parallel circuit. The breakdown voltage of the second diode is lower than the breakdown voltage of the first diode.
  • the second diode is a Schottky barrier diode.
  • the second diode is a pn junction diode or a pin junction diode.
  • the rectifying switching element is an FET.
  • the first diode is a parasitic diode of the FET.
  • a switching power supply device including a synchronous rectification circuit includes a synchronous rectification circuit, an input power supply, a main switching element, and an output terminal.
  • the main switching element is connected in series to the input power supply and performs a switching operation based on a control signal.
  • the synchronous rectifier circuit rectifies the applied voltage in synchronization with the switching operation of the main switching element.
  • the output terminal outputs the voltage rectified by the synchronous rectifier circuit.
  • the switching power supply device further includes a transformer that insulates the input power supply from the output terminal.
  • the switching power supply device further includes a commutation switching element and an inductance element on the secondary side of the transformer.
  • the commutation switching element is connected in series to a series circuit of a secondary winding of the transformer and a synchronous rectifier circuit.
  • the inductance element is connected in series between a connection point between the secondary winding and the commutation switching element and one end of the output terminal.
  • the breakdown voltage is determined by the first diode connected in parallel to the rectification switching element.
  • the reverse recovery characteristic is determined by the second diode connected in series to the parallel circuit of the rectifying switching element and the first diode.
  • a diode having a low breakdown voltage has good reverse recovery characteristics. For this reason, a synchronous rectifier circuit in which power loss due to reverse recovery current is reduced and a switching power supply device including the same can be realized by using a diode having a lower withstand voltage than the first diode as the second diode.
  • a diode having a high breakdown voltage has a high impedance in the reverse direction.
  • a high voltage in the reverse direction is mainly applied to the first diode. That is, it does not matter that the second diode has a low breakdown voltage. Therefore, a high voltage synchronous rectifier circuit and a switching power supply device including the same can be realized.
  • FIG. 5 is a circuit diagram showing a circuit configuration of a switching power supply device including a synchronous rectification circuit different from the switching power supply device shown in FIG. 4.
  • FIG. 1 is a circuit diagram showing a circuit configuration of a synchronous rectifier circuit according to an embodiment of the present invention.
  • the synchronous rectification circuit 10 includes a rectification switching element Q1 and a diode D10.
  • the rectifying switching element Q1 is an FET. For this reason, the rectifying switching element Q1 has a parasitic diode (first diode) D1.
  • the diode (second diode) D10 is connected in series with the rectifying switching element Q1 in a direction in which the cathode is connected to the source of the rectifying switching element Q1.
  • a diode having a lower breakdown voltage than the parasitic diode D1 is used as the diode D10.
  • FIG. 2 is a circuit diagram showing a circuit configuration of the resonant reset type forward converter 1 including the synchronous rectifier circuit 10 shown in FIG.
  • a resonant reset type forward converter (switching power supply device) 1 includes a transformer T, a main switching element Qp, a commutation switching element Qs, a synchronous rectifier circuit 10, a choke coil L, and a capacitor C. And an input power source Vin and an output terminal Vout.
  • the input power source Vin and the output terminal Vout are insulated by the transformer T.
  • the main switching element Qp is connected in series with the primary winding Np.
  • the commutation switching element Qs and the synchronous rectifier circuit 10 are connected in series with the secondary winding Ns.
  • the commutation switching element Qs and the synchronous rectification circuit 10 realize synchronous rectification in synchronization with the switching operation of the main switching element Qp.
  • the choke coil L accumulates or discharges energy according to the switching operation of the commutation switching element Qs and the synchronous rectification circuit 10.
  • One end of the choke coil L is connected to a connection point between the secondary winding Ns and the commutation switching element Qs.
  • the other end of the choke coil L is connected to one end of the output terminal Vout.
  • the other end of the output terminal Vout is connected to a connection point between the commutation switching element Qs and the synchronous rectifier circuit 10.
  • the output terminal Vout outputs a voltage stabilized by the capacitor C and supplies power to the load.
  • the main switching element Qp When the main switching element Qp is turned on based on a control signal (not shown), the commutation switching element Qs is turned off and the rectification switching element Q1 is turned on by a synchronous rectification control signal (not shown) synchronized with the control signal.
  • a voltage is applied from the input power source Vin to the primary winding Np.
  • X Vin is induced.
  • a voltage is applied to the synchronous rectifier circuit 10 in the forward direction. For this reason, a current flows through the path of the secondary winding Ns, the choke coil L, the output terminal Vout, and the synchronous rectifier circuit 10, and power is supplied to the load.
  • a voltage (Ns / Np ⁇ Vin ⁇ Vout) is applied between the terminals of the choke coil L. Therefore, energy is accumulated in the choke coil L.
  • the reverse recovery characteristic of the synchronous rectifier circuit 10 is determined by one of the parasitic diode D1 and the diode D10 having the better reverse recovery characteristic.
  • the parasitic diode D1 and the diode D10 are connected in series. For this reason, if one of the parasitic diode D1 and the diode D10 cuts off the current, no current flows through the other.
  • the diode D10 has a lower withstand voltage than the parasitic diode D1. For this reason, the reverse recovery characteristic of the diode D10 is better than the reverse recovery characteristic of the parasitic diode D1. Therefore, the reverse recovery characteristic of the synchronous rectifier circuit 10 is determined by the reverse recovery characteristic of the diode D10.
  • the reverse recovery characteristic of the synchronous rectifier circuit 10 is improved by using a low-breakdown-voltage diode as the diode D10 connected in series with the rectifier switching element Q1.
  • the diode D10 has a low breakdown voltage.
  • the synchronous rectification circuit 10 can be applied to various switching power supply devices.
  • the reason will be described with reference to FIG.
  • FIG. 3 shows the time variation of the current flowing through the synchronous rectifier circuit 10 and the voltage across the terminals of the diode when the applied voltage is reversed from the forward direction to the reverse direction in the synchronous rectifier circuit 10 according to the embodiment of the present invention.
  • waveform a indicates current I flowing through synchronous rectifier circuit 10.
  • a waveform b indicates the voltage VD10 between the terminals of the diode D10.
  • a waveform c shows the inter-terminal voltage VD1 of the parasitic diode D1.
  • the current I decreases and becomes zero at time t0. However, the current I does not quickly converge to zero.
  • the reverse recovery current increases during the period from time t0 to time t1.
  • the reverse recovery current reaches the maximum reverse recovery current value Irrm (Maximum Reverse Recovery Current) at time t1.
  • the length of the period from time t0 to time t1 and the magnitude of the maximum reverse recovery current value Irrm are determined by the reverse recovery characteristics of the diode D10.
  • the inter-terminal voltage VD10 of the diode D10 starts to increase in the reverse direction before the inter-terminal voltage VD1 of the parasitic diode D1. This is because the reverse recovery characteristic of the diode D10 is better than the reverse recovery characteristic of the parasitic diode D1.
  • the current I starts to decrease from the maximum reverse recovery current value Irrm and returns to zero at time t2.
  • the counter electromotive force generated in the secondary winding Ns is divided according to the impedance ratio of the parasitic diode D1 and the diode D10.
  • the divided back electromotive force is applied to the synchronous rectifier circuit 10.
  • the parasitic diode D1 has a higher breakdown voltage and a larger impedance than the diode D10. For this reason, the voltage applied to the parasitic diode D1 is higher than the voltage applied to the diode D10.
  • the inter-terminal voltage VD1 of the parasitic diode D1 starts increasing in the reverse direction. Accordingly, the voltage VD10 between the terminals of the diode D10 starts to decrease.
  • the inter-terminal voltage VD1 and the inter-terminal voltage VD10 converge to voltages corresponding to the impedance ratio of the parasitic diode D1 and the diode D10 at time t3.
  • a high voltage diode As the parasitic diode D1, a high voltage is not applied to the diode D10 in the reverse direction. For this reason, the diode D10 is not destroyed. Therefore, a diode having a lower withstand voltage than the diode D20 in the conventional synchronous rectifier circuit 20 can be used as the diode D10 in the synchronous rectifier circuit 10 according to the embodiment of the present invention. Therefore, in the diode D10, power loss due to the reverse recovery current can be reduced as compared with the diode D20.
  • the on-resistance of the rectifier switching element Q1 is set to be small so that the rectifier switching is not performed by the parasitic diode D1.
  • a current flows through the element Q1. Therefore, no power loss due to the forward voltage drop occurs in the parasitic diode D1. Power loss occurs only at diode D10.
  • a diode generally has a trade-off relationship between the breakdown voltage and the forward voltage Vf. That is, the lower the breakdown voltage, the lower the forward voltage Vf.
  • a diode having a lower breakdown voltage than the diode D20 can be used. For this reason, in the diode D10, the power loss due to the forward voltage drop can be reduced as compared with the diode D20.
  • the synchronous rectifier circuit 10 As described above, in the synchronous rectifier circuit 10 according to the embodiment of the present invention, it is possible to use a diode having a low breakdown voltage and good reverse recovery characteristics. For this reason, the synchronous rectifier circuit 10 can reduce both the power loss due to the forward voltage drop and the power loss due to the reverse recovery current, as compared with the conventional synchronous rectifier circuit 20.
  • a Schottky Barrier Diode is known as a diode with low breakdown voltage and good reverse recovery characteristics.
  • the Schottky barrier diode has a very small reverse recovery current due to the principle of rectification operation. For this reason, power loss due to the reverse recovery current hardly occurs. Therefore, it is preferable to use a Schottky barrier diode as the diode D10.
  • the change when the reverse recovery current converges to zero is gentle (referred to as soft recovery characteristics). Therefore, by using a Schottky barrier diode, it is possible to reduce noise generated during the switching operation.
  • pn junction diodes and pin junction diodes also have good reverse recovery characteristics when the breakdown voltage is low. Therefore, power loss due to reverse recovery current can be reduced by using a pn junction diode and a pin junction diode for the diode D10.
  • the diode D10 is connected in the direction in which the cathode of the diode D10 is connected to the source of the rectification switching element Q1.
  • the connection direction of the diode D10 is not limited to this. The same effect can be obtained even when the anode of the diode D10 is connected to the drain of the rectifying switching element Q1.
  • the rectifying switching element Q1 is not limited to the switching element including the parasitic diode D1.
  • the diode connected in parallel to the rectifying switching element Q1 is not limited to the parasitic diode D1 of the rectifying switching element Q1.
  • the rectifying switching element Q1 does not include the parasitic diode D1
  • a similar effect can be obtained by connecting a diode having a higher breakdown voltage than the diode D10 in parallel to the rectifying switching element Q1 instead of the parasitic diode D1. .
  • the power loss due to the forward voltage drop increases when the diode has a high breakdown voltage.
  • a pin junction diode has a relatively good reverse recovery characteristic when it has a high breakdown voltage.
  • the forward voltage Vf is high, the power loss due to the forward voltage drop increases.
  • GaN (gallium nitride) Schottky barrier diodes and SiC (silicon carbide) Schottky barrier diodes are known as Schottky barrier diodes having a high breakdown voltage of about 600 V. These high breakdown voltage Schottky barrier diodes also have a high forward voltage Vf. Therefore, the power loss due to the forward voltage drop increases. Therefore, the diode used for the synchronous rectifier circuit 10 should be determined in consideration of the balance between withstand voltage and power loss.
  • the synchronous rectifier circuit 10 synchronized with the switching operation of the main switching element Qp has been described as an example.
  • the “synchronous rectifier circuit” according to the present invention is not limited to this.
  • the synchronous rectifier circuit 10 can obtain the same effect in general synchronous rectifier circuits in which a voltage is applied in the reverse direction and a reverse recovery current flows.
  • the rectifying switching element Q1 may not be synchronized with the switching operation of the main switching element Qp.
  • the switching power supply device including the synchronous rectifier circuit 10 As the switching power supply device including the synchronous rectifier circuit 10 according to the embodiment of the present invention, the case where the input power source Vin and the output terminal Vout are insulated by the transformer T has been described using the resonance reset type forward converter 1 as an example. .
  • the “synchronous rectifier circuit” according to the present invention is not limited to this.
  • the synchronous rectifier circuit 10 can be applied to all switching power supply devices including a synchronous rectifier circuit in which a voltage is applied in the reverse direction and a reverse recovery current flows. Regardless of whether the switching power supply device is an insulating type or a non-insulating type, the circuit system is not limited. Therefore, the switching power supply device including the synchronous rectifier circuit 10 may be a DC-DC converter, a non-insulated DC-DC converter, an inverter, or the like of a power conditioner.
  • T transformer Np primary winding, Ns secondary winding, L choke coil, C capacitor, Qp main switching element, Qs commutation switching element, Q, Q1, Q2 rectification switching element, D, D1, D2 parasitic diode, D10, D20 diode, R2 resistor, 1, 2 resonant reset type forward converter, 10, 20 synchronous rectifier circuit, Vin input power supply, Vout output terminal, I current, Irrm maximum reverse recovery current value, Vf forward voltage, VD1, VD10 Terminal voltage, t0, t1, t2, t3 time.

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Abstract

A synchronous rectification circuit comprises a rectification switching element (Q1), a parasitic diode (D1), and a diode (D10). The parasitic diode (D1) is connected in parallel to the rectification switching element (Q1). The diode (D10) is connected in series to the parallel circuit containing the rectification switching element (Q1) and the parasitic diode (D1). The pressure resistance of the diode (D10) is less than the pressure resistance of the parasitic diode (D1).

Description

同期整流回路およびそれを備えたスイッチング電源装置Synchronous rectifier circuit and switching power supply device including the same
　本発明は、同期整流回路およびそれを備えたスイッチング電源装置に関し、特に、ダイオードを含む同期整流回路およびそれを備えたスイッチング電源装置に関する。 The present invention relates to a synchronous rectifier circuit and a switching power supply device including the same, and more particularly to a synchronous rectifier circuit including a diode and a switching power supply device including the same.
　スイッチング電源装置では、電力変換効率を高めるために同期整流回路が多く用いられている。同期整流回路は、スイッチング動作時に生じる電力損失を低減する。 In a switching power supply, a synchronous rectifier circuit is often used to increase power conversion efficiency. The synchronous rectifier circuit reduces power loss that occurs during the switching operation.
　図４は、従来の同期整流回路を備えたスイッチング電源装置の回路構成を示す回路図である（特許文献１：特開２０１０－１６１８６８号公報）。 FIG. 4 is a circuit diagram showing a circuit configuration of a switching power supply device having a conventional synchronous rectifier circuit (Patent Document 1: Japanese Patent Application Laid-Open No. 2010-161868).
　図４を参照して、スイッチング電源装置は、共振リセット形フォワードコンバータである。スイッチング電源装置は、トランスＴと、主スイッチング素子Ｑｐと、転流スイッチング素子Ｑｓと、整流スイッチング素子Ｑと、チョークコイルＬと、コンデンサＣと、入力電源Ｖｉｎと、出力端子Ｖｏｕｔとを備える。整流スイッチング素子Ｑは、寄生ダイオードＤを含む。 Referring to FIG. 4, the switching power supply device is a resonant reset type forward converter. The switching power supply device includes a transformer T, a main switching element Qp, a commutation switching element Qs, a rectifying switching element Q, a choke coil L, a capacitor C, an input power supply Vin, and an output terminal Vout. The rectifying switching element Q includes a parasitic diode D.
　整流スイッチング素子Ｑに印加される電圧が順方向から逆方向に反転すると、整流スイッチング素子Ｑを順方向に流れる電流は減少する。しかし、電流はすぐにゼロに収束するのではない。一旦逆回復電流が流れてから、電流はゼロに収束する。 When the voltage applied to the rectifying switching element Q is reversed from the forward direction to the reverse direction, the current flowing in the forward direction through the rectifying switching element Q decreases. However, the current does not quickly converge to zero. Once reverse recovery current flows, the current converges to zero.
　整流スイッチング素子Ｑを逆回復電流が流れる時間（逆回復時間）の長さ、および逆回復電流の大きさを、整流スイッチング素子Ｑの逆回復特性と言う。逆回復特性は、ＦＥＴ（Ｆｉｅｌｄ　Ｅｆｆｅｃｔ　Ｔｒａｎｓｉｓｔｏｒ）である整流スイッチング素子Ｑの寄生ダイオードＤにより定まる。寄生ダイオードＤの逆回復特性が悪いと、逆回復時間が長くなるとともに、逆回復電流が大きくなる。このため、スイッチング動作時に生じる電力損失が増加してしまう。したがって、電力変換効率の高いスイッチング電源装置を実現できない。 The length of time that the reverse recovery current flows through the rectifying switching element Q (reverse recovery time) and the magnitude of the reverse recovery current are called reverse recovery characteristics of the rectifying switching element Q. The reverse recovery characteristic is determined by the parasitic diode D of the rectifying switching element Q, which is an FET (Field Effect Transistor). If the reverse recovery characteristic of the parasitic diode D is poor, the reverse recovery time becomes long and the reverse recovery current increases. For this reason, the power loss which arises at the time of switching operation will increase. Therefore, a switching power supply device with high power conversion efficiency cannot be realized.
特開２０１０－１６１８６８号公報JP 2010-161868 A 特開２００４－２０１４５５号公報JP 2004-201445 A
　特許文献２（特開２００４－２０１４５５号公報）に、逆回復電流による電力損失を低減する同期整流回路が開示されている。 Patent Document 2 (Japanese Patent Laid-Open No. 2004-201445) discloses a synchronous rectifier circuit that reduces power loss due to reverse recovery current.
　図５は、図４に示す共振リセット形フォワードコンバータと異なる同期整流回路を備えた共振リセット形フォワードコンバータ２の回路構成を示す回路図である。図５を参照して、共振リセット形フォワードコンバータ２は、整流スイッチング素子Ｑに代えて同期整流回路２０を備える点において、図４に示す共振リセット形フォワードコンバータと異なる。 FIG. 5 is a circuit diagram showing a circuit configuration of a resonant reset type forward converter 2 having a synchronous rectifier circuit different from the resonant reset type forward converter shown in FIG. Referring to FIG. 5, resonant reset type forward converter 2 is different from the resonant reset type forward converter shown in FIG. 4 in that synchronous rectifier circuit 20 is provided instead of rectifying switching element Q.
　共振リセット形フォワードコンバータ２は、トランスＴと、主スイッチング素子Ｑｐと、転流スイッチング素子Ｑｓと、同期整流回路２０と、チョークコイルＬと、コンデンサＣと、入力電源Ｖｉｎと、出力端子Ｖｏｕｔとを備える。 The resonant reset type forward converter 2 includes a transformer T, a main switching element Qp, a commutation switching element Qs, a synchronous rectifier circuit 20, a choke coil L, a capacitor C, an input power source Vin, and an output terminal Vout. Prepare.
　共振リセット形フォワードコンバータ２では、トランスＴによって入力電源Ｖｉｎと出力端子Ｖｏｕｔとが絶縁される。トランスＴの１次側では、主スイッチング素子Ｑｐが１次巻線Ｎｐと直列に接続される。トランスＴの２次側では、転流スイッチング素子Ｑｓおよび同期整流回路２０が２次巻線Ｎｓと直列に接続される。 In the resonant reset type forward converter 2, the input power source Vin and the output terminal Vout are insulated by the transformer T. On the primary side of the transformer T, the main switching element Qp is connected in series with the primary winding Np. On the secondary side of the transformer T, the commutation switching element Qs and the synchronous rectifier circuit 20 are connected in series with the secondary winding Ns.
　転流スイッチング素子Ｑｓおよび同期整流回路２０は、主スイッチング素子Ｑｐのスイッチング動作と同期して、同期整流を実現する。 The commutation switching element Qs and the synchronous rectification circuit 20 realize synchronous rectification in synchronization with the switching operation of the main switching element Qp.
　同期整流回路２０は、整流スイッチング素子Ｑ２と、抵抗Ｒ２と、ダイオードＤ２０とを含む。整流スイッチング素子Ｑ２はＦＥＴである。このため、整流スイッチング素子Ｑ２は、寄生ダイオードＤ２を有する。抵抗Ｒ２は、整流スイッチング素子Ｑ２に直列に接続される。ダイオードＤ２０は、整流スイッチング素子Ｑ２と抵抗Ｒ２との直列回路に並列に、アノードが整流スイッチング素子Ｑ２のソースと接続される向きに接続される。 The synchronous rectifier circuit 20 includes a rectifier switching element Q2, a resistor R2, and a diode D20. The rectifying switching element Q2 is an FET. For this reason, the rectifying switching element Q2 has a parasitic diode D2. The resistor R2 is connected in series with the rectifying switching element Q2. The diode D20 is connected in parallel to the series circuit of the rectifying switching element Q2 and the resistor R2 in the direction in which the anode is connected to the source of the rectifying switching element Q2.
　チョークコイルＬは、転流スイッチング素子Ｑｓおよび同期整流回路２０のスイッチング動作に応じて、エネルギーを蓄積または放出する。チョークコイルＬの一端は、２次巻線Ｎｓと転流スイッチング素子Ｑｓとの接続点に接続される。チョークコイルＬの他端は、出力端子Ｖｏｕｔの一端に接続される。出力端子Ｖｏｕｔの他端は、転流スイッチング素子Ｑｓと同期整流回路２０との接続点に接続される。出力端子Ｖｏｕｔは、コンデンサＣによって安定化された電圧を出力して、負荷に電力を供給する。 The choke coil L stores or releases energy according to the switching operation of the commutation switching element Qs and the synchronous rectification circuit 20. One end of the choke coil L is connected to a connection point between the secondary winding Ns and the commutation switching element Qs. The other end of the choke coil L is connected to one end of the output terminal Vout. The other end of the output terminal Vout is connected to a connection point between the commutation switching element Qs and the synchronous rectification circuit 20. The output terminal Vout outputs a voltage stabilized by the capacitor C and supplies power to the load.
　以下、同期整流回路２０を備えた共振リセット形フォワードコンバータ２の動作を説明する。 Hereinafter, the operation of the resonant reset type forward converter 2 including the synchronous rectifier circuit 20 will be described.
　主スイッチング素子Ｑｐが制御信号（図示しない）に基づいてターンオンすると、制御信号と同期した同期整流制御信号（図示しない）により、転流スイッチング素子Ｑｓがターンオフするとともに、整流スイッチング素子Ｑ２がターンオンする。 When the main switching element Qp is turned on based on a control signal (not shown), the commutation switching element Qs is turned off and the rectification switching element Q2 is turned on by a synchronous rectification control signal (not shown) synchronized with the control signal.
　トランスＴの１次側で、入力電源Ｖｉｎから１次巻線Ｎｐに電圧が印加される。これにより、トランスＴの２次側では、２次巻線Ｎｓで図中黒丸に向かって電流が流れる方向に、１次巻線Ｎｐと２次巻線Ｎｓの比に応じた電圧（Ｎｓ／Ｎｐ×Ｖｉｎ）が誘起される。同期整流回路２０には順方向に電圧が印加される。このため、２次巻線Ｎｓ―チョークコイルＬ―出力端子Ｖｏｕｔ―同期整流回路２０の経路を電流が流れ、負荷に電力が供給される。このとき、チョークコイルＬの端子間には電圧（Ｎｓ／Ｎｐ×Ｖｉｎ－Ｖｏｕｔ）が印加される。したがって、チョークコイルＬにエネルギーが蓄積される。 On the primary side of the transformer T, a voltage is applied from the input power source Vin to the primary winding Np. Thereby, on the secondary side of the transformer T, the voltage (Ns / Np) corresponding to the ratio of the primary winding Np and the secondary winding Ns in the direction in which the current flows in the secondary winding Ns toward the black circle in the figure. X Vin) is induced. A voltage is applied to the synchronous rectifier circuit 20 in the forward direction. For this reason, a current flows through the path of the secondary winding Ns, the choke coil L, the output terminal Vout, and the synchronous rectifier circuit 20, and power is supplied to the load. At this time, a voltage (Ns / Np × Vin−Vout) is applied between the terminals of the choke coil L. Therefore, energy is accumulated in the choke coil L.
　次に、主スイッチング素子Ｑｐが制御信号に基づいてターンオフすると、制御信号と同期した同期整流制御信号により、転流スイッチング素子Ｑｓがターンオンするとともに、整流スイッチング素子Ｑ２がターンオフする。 Next, when the main switching element Qp is turned off based on the control signal, the commutation switching element Qs is turned on and the rectification switching element Q2 is turned off by the synchronous rectification control signal synchronized with the control signal.
　トランスＴの１次側からの電力の供給がなくなると、トランスＴの２次側では、チョークコイルＬに蓄積されたエネルギーが放出される。このとき、チョークコイルＬ―出力端子Ｖｏｕｔ―転流スイッチング素子Ｑｓの経路を電流が流れ、負荷に電力が供給される。加えて、２次巻線Ｎｓで図中黒丸の逆側に向かって電流が流れる方向に逆起電力が発生する。このため、同期整流回路２０には逆方向に電圧が印加される。 When the power supply from the primary side of the transformer T is lost, the energy accumulated in the choke coil L is released on the secondary side of the transformer T. At this time, current flows through the path of the choke coil L, the output terminal Vout, and the commutation switching element Qs, and power is supplied to the load. In addition, back electromotive force is generated in the direction in which current flows in the secondary winding Ns toward the opposite side of the black circle in the figure. For this reason, a voltage is applied to the synchronous rectifier circuit 20 in the reverse direction.
　同期整流回路２０に逆方向に電圧が印加されるとき、抵抗Ｒ２の抵抗値を十分大きく設定することにより、整流スイッチング素子Ｑ２と抵抗Ｒ２との直列回路ではなく、ダイオードＤ２０を電流が流れる。そのため、同期整流回路２０の逆回復特性は、寄生ダイオードＤ２に代えて、ダイオードＤ２０によって定まる。したがって、ダイオードＤ２０に寄生ダイオードＤ２よりも逆回復特性が良いダイオードを用いることで、逆回復電流による電力損失を低減できる。 When a voltage is applied to the synchronous rectifier circuit 20 in the reverse direction, by setting the resistance value of the resistor R2 sufficiently large, a current flows through the diode D20 instead of the series circuit of the rectifier switching element Q2 and the resistor R2. Therefore, the reverse recovery characteristic of the synchronous rectifier circuit 20 is determined by the diode D20 instead of the parasitic diode D2. Therefore, by using a diode having better reverse recovery characteristics than the parasitic diode D2 as the diode D20, power loss due to the reverse recovery current can be reduced.
　ところが、２次巻線Ｎｓで発生する逆起電力は高電圧である。このため、ダイオードＤ２０には、寄生ダイオードＤ２よりも逆回復特性が良いことが要求されるだけでない。ダイオードＤ２０には、寄生ダイオードＤ２よりも高耐圧であることも要求される。 However, the back electromotive force generated in the secondary winding Ns is a high voltage. For this reason, the diode D20 is not only required to have better reverse recovery characteristics than the parasitic diode D2. The diode D20 is also required to have a higher breakdown voltage than the parasitic diode D2.
　しかしながら、ダイオードでは、耐圧と逆回復特性との間にトレードオフの関係が一般に成り立つことが知られている。このため、逆回復電流による電力損失を低減するために逆回復特性が良いダイオードを用いると、低耐圧になってしまう。 However, it is known that a diode generally has a trade-off relationship between breakdown voltage and reverse recovery characteristics. For this reason, if a diode having a good reverse recovery characteristic is used in order to reduce power loss due to the reverse recovery current, the withstand voltage is reduced.
　したがって、共振リセット形フォワードコンバータ２では、スイッチング動作時に生じる電力損失を低減できる。その一方で、高耐圧の同期整流回路を備えたスイッチング電源装置を実現できない。 Therefore, the resonant reset type forward converter 2 can reduce the power loss generated during the switching operation. On the other hand, it is not possible to realize a switching power supply device having a high-voltage synchronous rectifier circuit.
　それゆえに、本発明は、上記問題点を解決するためになされたものであり、電力損失を低減し、かつ、高耐圧の同期整流回路およびそれを備えたスイッチング電源装置を提供することを目的とする。 Therefore, the present invention has been made to solve the above-described problems, and has an object to provide a high-voltage synchronous rectifier circuit and a switching power supply device including the same that reduce power loss. To do.
　上記目的を達成するために、本発明のある局面に従うと、同期整流回路は、整流スイッチング素子と、整流スイッチング素子に並列に接続された第１のダイオードと、整流スイッチング素子と第１のダイオードとの並列回路に直列に接続された第２のダイオードとを備える。第２のダイオードの耐圧は、第１のダイオードの耐圧よりも低い。 In order to achieve the above object, according to one aspect of the present invention, a synchronous rectifier circuit includes a rectifying switching element, a first diode connected in parallel to the rectifying switching element, a rectifying switching element, and a first diode. And a second diode connected in series to the parallel circuit. The breakdown voltage of the second diode is lower than the breakdown voltage of the first diode.
　好ましくは、第２のダイオードは、ショットキーバリアダイオードである。
　好ましくは、第２のダイオードは、ｐｎ接合ダイオードまたはｐｉｎ接合ダイオードである。 Preferably, the second diode is a Schottky barrier diode.
Preferably, the second diode is a pn junction diode or a pin junction diode.
　好ましくは、整流スイッチング素子は、ＦＥＴである。第１のダイオードは、ＦＥＴの寄生ダイオードである。 Preferably, the rectifying switching element is an FET. The first diode is a parasitic diode of the FET.
　上記目的を達成するために、本発明の他の局面に従うと、同期整流回路を備えたスイッチング電源装置は、同期整流回路と、入力電源と、主スイッチング素子と、出力端子とを備える。主スイッチング素子は、入力電源に直列に接続し、制御信号に基づいてスイッチング動作する。同期整流回路とは、印加された電圧を、主スイッチング素子のスイッチング動作と同期して整流する。出力端子は、同期整流回路が整流した電圧を出力する。 In order to achieve the above object, according to another aspect of the present invention, a switching power supply device including a synchronous rectification circuit includes a synchronous rectification circuit, an input power supply, a main switching element, and an output terminal. The main switching element is connected in series to the input power supply and performs a switching operation based on a control signal. The synchronous rectifier circuit rectifies the applied voltage in synchronization with the switching operation of the main switching element. The output terminal outputs the voltage rectified by the synchronous rectifier circuit.
　好ましくは、スイッチング電源装置は、入力電源と出力端子とを絶縁するトランスをさらに備える。 Preferably, the switching power supply device further includes a transformer that insulates the input power supply from the output terminal.
　好ましくは、スイッチング電源装置は、トランスの２次側に、転流スイッチング素子とインダクタンス素子とをさらに備える。転流スイッチング素子は、トランスの２次巻線と同期整流回路との直列回路に直列に接続される。インダクタンス素子は、２次巻線と転流スイッチング素子との接続点と、出力端子の一端との間に直列に接続される。 Preferably, the switching power supply device further includes a commutation switching element and an inductance element on the secondary side of the transformer. The commutation switching element is connected in series to a series circuit of a secondary winding of the transformer and a synchronous rectifier circuit. The inductance element is connected in series between a connection point between the secondary winding and the commutation switching element and one end of the output terminal.
　本発明に係る同期整流回路によれば、整流スイッチング素子に並列に接続された第１のダイオードにより、耐圧が定まる。整流スイッチング素子と第１のダイオードとの並列回路に直列に接続された第２のダイオードにより、逆回復特性が定まる。低耐圧であるダイオードは逆回復特性が良い。このため、第２のダイオードに第１のダイオードよりも低耐圧のダイオードを用いることで、逆回復電流による電力損失を低減した同期整流回路およびそれを備えたスイッチング電源装置を実現できる。また、高耐圧であるダイオードは逆方向のインピーダンスが高い。このため、第１のダイオードに高耐圧のダイオードを用いることで、逆方向の高電圧は第１のダイオードに主に印加される。つまり、第２のダイオードが低耐圧であることは問題にならない。したがって、高耐圧の同期整流回路およびそれを備えたスイッチング電源装置を実現できる。 According to the synchronous rectification circuit of the present invention, the breakdown voltage is determined by the first diode connected in parallel to the rectification switching element. The reverse recovery characteristic is determined by the second diode connected in series to the parallel circuit of the rectifying switching element and the first diode. A diode having a low breakdown voltage has good reverse recovery characteristics. For this reason, a synchronous rectifier circuit in which power loss due to reverse recovery current is reduced and a switching power supply device including the same can be realized by using a diode having a lower withstand voltage than the first diode as the second diode. In addition, a diode having a high breakdown voltage has a high impedance in the reverse direction. For this reason, by using a high breakdown voltage diode as the first diode, a high voltage in the reverse direction is mainly applied to the first diode. That is, it does not matter that the second diode has a low breakdown voltage. Therefore, a high voltage synchronous rectifier circuit and a switching power supply device including the same can be realized.
本発明の実施の形態に係る同期整流回路の回路構成を示す回路図である。It is a circuit diagram which shows the circuit structure of the synchronous rectifier circuit which concerns on embodiment of this invention. 図１に示す同期整流回路を備えたスイッチング電源装置の回路構成を示す回路図である。It is a circuit diagram which shows the circuit structure of the switching power supply device provided with the synchronous rectification circuit shown in FIG. 本発明の実施の形態に係る同期整流回路において、印加される電圧が順方向から逆方向に反転するとき、同期整流回路を流れる電流およびダイオードの端子間電圧の時間変化を示す波形図である。In the synchronous rectifier circuit according to the embodiment of the present invention, when the applied voltage is reversed from the forward direction to the reverse direction, it is a waveform diagram showing the time change of the current flowing through the synchronous rectifier circuit and the voltage between the terminals of the diode. 従来の同期整流回路を備えたスイッチング電源装置の回路構成を示す回路図である。It is a circuit diagram which shows the circuit structure of the switching power supply device provided with the conventional synchronous rectifier circuit. 図４に示すスイッチング電源装置と異なる同期整流回路を備えたスイッチング電源装置の回路構成を示す回路図である。FIG. 5 is a circuit diagram showing a circuit configuration of a switching power supply device including a synchronous rectification circuit different from the switching power supply device shown in FIG. 4.
　以下、本発明に係る実施の形態について図面を参照しながら詳細に説明する。なお、図中同一または相当部分には同一符号を付して、その説明を繰り返さない。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or an equivalent part in a figure, and the description is not repeated.
　　（実施の形態）
　図１は、本発明の実施の形態に係る同期整流回路の回路構成を示す回路図である。 (Embodiment)
FIG. 1 is a circuit diagram showing a circuit configuration of a synchronous rectifier circuit according to an embodiment of the present invention.
　図１を参照して、同期整流回路１０は、整流スイッチング素子Ｑ１とダイオードＤ１０とを含む。 Referring to FIG. 1, the synchronous rectification circuit 10 includes a rectification switching element Q1 and a diode D10.
　整流スイッチング素子Ｑ１はＦＥＴである。このため、整流スイッチング素子Ｑ１は寄生ダイオード（第１のダイオード）Ｄ１を有する。ダイオード（第２のダイオード）Ｄ１０は、整流スイッチング素子Ｑ１に直列に、カソードが整流スイッチング素子Ｑ１のソースに接続される向きに接続される。ダイオードＤ１０には、寄生ダイオードＤ１よりも低耐圧のダイオードが用いられる。 The rectifying switching element Q1 is an FET. For this reason, the rectifying switching element Q1 has a parasitic diode (first diode) D1. The diode (second diode) D10 is connected in series with the rectifying switching element Q1 in a direction in which the cathode is connected to the source of the rectifying switching element Q1. A diode having a lower breakdown voltage than the parasitic diode D1 is used as the diode D10.
　図２は、図１に示す同期整流回路１０を備えた共振リセット形フォワードコンバータ１の回路構成を示す回路図である。 FIG. 2 is a circuit diagram showing a circuit configuration of the resonant reset type forward converter 1 including the synchronous rectifier circuit 10 shown in FIG.
　図２を参照して、共振リセット形フォワードコンバータ（スイッチング電源装置）１は、トランスＴと、主スイッチング素子Ｑｐと、転流スイッチング素子Ｑｓと、同期整流回路１０と、チョークコイルＬと、コンデンサＣと、入力電源Ｖｉｎと、出力端子Ｖｏｕｔとを備える。 Referring to FIG. 2, a resonant reset type forward converter (switching power supply device) 1 includes a transformer T, a main switching element Qp, a commutation switching element Qs, a synchronous rectifier circuit 10, a choke coil L, and a capacitor C. And an input power source Vin and an output terminal Vout.
　共振リセット形フォワードコンバータ１では、トランスＴによって入力電源Ｖｉｎと出力端子Ｖｏｕｔとが絶縁される。トランスＴの１次側では、主スイッチング素子Ｑｐが１次巻線Ｎｐと直列に接続される。トランスＴの２次側では、転流スイッチング素子Ｑｓおよび同期整流回路１０が２次巻線Ｎｓと直列に接続される。 In the resonant reset type forward converter 1, the input power source Vin and the output terminal Vout are insulated by the transformer T. On the primary side of the transformer T, the main switching element Qp is connected in series with the primary winding Np. On the secondary side of the transformer T, the commutation switching element Qs and the synchronous rectifier circuit 10 are connected in series with the secondary winding Ns.
　転流スイッチング素子Ｑｓおよび同期整流回路１０は、主スイッチング素子Ｑｐのスイッチング動作と同期して、同期整流を実現する。 The commutation switching element Qs and the synchronous rectification circuit 10 realize synchronous rectification in synchronization with the switching operation of the main switching element Qp.
　チョークコイルＬは、転流スイッチング素子Ｑｓおよび同期整流回路１０のスイッチング動作に応じて、エネルギーを蓄積または放出する。チョークコイルＬの一端は、２次巻線Ｎｓと転流スイッチング素子Ｑｓとの接続点に接続される。チョークコイルＬの他端は、出力端子Ｖｏｕｔの一端に接続される。出力端子Ｖｏｕｔの他端は、転流スイッチング素子Ｑｓと同期整流回路１０との接続点に接続される。出力端子Ｖｏｕｔは、コンデンサＣによって安定化された電圧を出力して、負荷に電力を供給する。 The choke coil L accumulates or discharges energy according to the switching operation of the commutation switching element Qs and the synchronous rectification circuit 10. One end of the choke coil L is connected to a connection point between the secondary winding Ns and the commutation switching element Qs. The other end of the choke coil L is connected to one end of the output terminal Vout. The other end of the output terminal Vout is connected to a connection point between the commutation switching element Qs and the synchronous rectifier circuit 10. The output terminal Vout outputs a voltage stabilized by the capacitor C and supplies power to the load.
　以下、同期整流回路１０を備えた共振リセット形フォワードコンバータ１の動作を説明する。 Hereinafter, the operation of the resonant reset type forward converter 1 including the synchronous rectifier circuit 10 will be described.
　主スイッチング素子Ｑｐが制御信号（図示しない）に基づいてターンオンすると、制御信号と同期した同期整流制御信号（図示しない）により、転流スイッチング素子Ｑｓがターンオフするとともに、整流スイッチング素子Ｑ１がターンオンする。 When the main switching element Qp is turned on based on a control signal (not shown), the commutation switching element Qs is turned off and the rectification switching element Q1 is turned on by a synchronous rectification control signal (not shown) synchronized with the control signal.
　トランスＴの１次側で、入力電源Ｖｉｎから１次巻線Ｎｐに電圧が印加される。これにより、トランスＴの２次側では、２次巻線Ｎｓで図中黒丸に向かって電流が流れる方向に、１次巻線Ｎｐと２次巻線Ｎｓの比に応じた電圧（Ｎｓ／Ｎｐ×Ｖｉｎ）が誘起される。同期整流回路１０には順方向に電圧が印加される。このため、２次巻線Ｎｓ―チョークコイルＬ―出力端子Ｖｏｕｔ―同期整流回路１０の経路を電流が流れ、負荷に電力が供給される。このとき、チョークコイルＬの端子間には電圧（Ｎｓ／Ｎｐ×Ｖｉｎ－Ｖｏｕｔ）が印加される。したがって、チョークコイルＬにエネルギーが蓄積される。 On the primary side of the transformer T, a voltage is applied from the input power source Vin to the primary winding Np. Thereby, on the secondary side of the transformer T, the voltage (Ns / Np) corresponding to the ratio of the primary winding Np to the secondary winding Ns in the direction in which current flows in the secondary winding Ns toward the black circle in the figure. X Vin) is induced. A voltage is applied to the synchronous rectifier circuit 10 in the forward direction. For this reason, a current flows through the path of the secondary winding Ns, the choke coil L, the output terminal Vout, and the synchronous rectifier circuit 10, and power is supplied to the load. At this time, a voltage (Ns / Np × Vin−Vout) is applied between the terminals of the choke coil L. Therefore, energy is accumulated in the choke coil L.
　次に、主スイッチング素子Ｑｐが制御信号に基づいてターンオフすると、制御信号と同期した同期整流制御信号により、転流スイッチング素子Ｑｓがターンオンするとともに、整流スイッチング素子Ｑ１がターンオフする。 Next, when the main switching element Qp is turned off based on the control signal, the commutation switching element Qs is turned on and the rectification switching element Q1 is turned off by the synchronous rectification control signal synchronized with the control signal.
　トランスＴの１次側から電力の供給がなくなると、トランスＴの２次側では、チョークコイルＬに蓄積されたエネルギーが放出される。このとき、チョークコイルＬ―出力端子Ｖｏｕｔ―転流スイッチング素子Ｑｓの経路を電流が流れ、負荷に電力が供給される。加えて、２次巻線Ｎｓで図中黒丸の逆側に向かって電流が流れる方向に、逆起電力が発生する。このため、同期整流回路１０には逆方向に電圧が印加される。 When there is no power supply from the primary side of the transformer T, the energy accumulated in the choke coil L is released on the secondary side of the transformer T. At this time, current flows through the path of the choke coil L, the output terminal Vout, and the commutation switching element Qs, and power is supplied to the load. In addition, back electromotive force is generated in the direction in which current flows in the secondary winding Ns toward the opposite side of the black circle in the figure. For this reason, a voltage is applied to the synchronous rectifier circuit 10 in the reverse direction.
　同期整流回路１０に逆方向に電圧が印加されるとき、同期整流回路１０の逆回復特性は、寄生ダイオードＤ１およびダイオードＤ１０のうちのいずれか逆回復特性の良い方によって定まる。寄生ダイオードＤ１とダイオードＤ１０は直列に接続される。このため、寄生ダイオードＤ１およびダイオードＤ１０のうちのいずれか一方が電流を遮断すれば、他方にも電流が流れないからである。ダイオードＤ１０は、寄生ダイオードＤ１よりも低耐圧である。このため、ダイオードＤ１０の逆回復特性の方が、寄生ダイオードＤ１の逆回復特性よりも良い。したがって、同期整流回路１０の逆回復特性は、ダイオードＤ１０の逆回復特性によって定まることになる。 When a voltage is applied to the synchronous rectifier circuit 10 in the reverse direction, the reverse recovery characteristic of the synchronous rectifier circuit 10 is determined by one of the parasitic diode D1 and the diode D10 having the better reverse recovery characteristic. The parasitic diode D1 and the diode D10 are connected in series. For this reason, if one of the parasitic diode D1 and the diode D10 cuts off the current, no current flows through the other. The diode D10 has a lower withstand voltage than the parasitic diode D1. For this reason, the reverse recovery characteristic of the diode D10 is better than the reverse recovery characteristic of the parasitic diode D1. Therefore, the reverse recovery characteristic of the synchronous rectifier circuit 10 is determined by the reverse recovery characteristic of the diode D10.
　以上、整流スイッチング素子Ｑ１に直列に接続されたダイオードＤ１０に低耐圧のダイオードを用いることで、同期整流回路１０の逆回復特性が良くなることを説明した。ここで、同期整流回路１０に逆方向に高電圧が印加されても、ダイオードＤ１０が低耐圧であることは問題にならない。このため、同期整流回路１０は様々なスイッチング電源装置に適用できる。以下、その理由について図３を参照しながら説明する。 As described above, it has been described that the reverse recovery characteristic of the synchronous rectifier circuit 10 is improved by using a low-breakdown-voltage diode as the diode D10 connected in series with the rectifier switching element Q1. Here, even if a high voltage is applied to the synchronous rectifier circuit 10 in the reverse direction, it does not matter that the diode D10 has a low breakdown voltage. For this reason, the synchronous rectification circuit 10 can be applied to various switching power supply devices. Hereinafter, the reason will be described with reference to FIG.
　図３は、本発明の実施の形態に係る同期整流回路１０において、印加される電圧が順方向から逆方向に反転するとき、同期整流回路１０を流れる電流およびダイオードの端子間電圧の時間変化を示す波形図である。図３を参照して、波形ａは、同期整流回路１０を流れる電流Ｉを示す。波形ｂは、ダイオードＤ１０の端子間電圧ＶＤ１０を示す。波形ｃは、寄生ダイオードＤ１の端子間電圧ＶＤ１を示す。 FIG. 3 shows the time variation of the current flowing through the synchronous rectifier circuit 10 and the voltage across the terminals of the diode when the applied voltage is reversed from the forward direction to the reverse direction in the synchronous rectifier circuit 10 according to the embodiment of the present invention. FIG. Referring to FIG. 3, waveform a indicates current I flowing through synchronous rectifier circuit 10. A waveform b indicates the voltage VD10 between the terminals of the diode D10. A waveform c shows the inter-terminal voltage VD1 of the parasitic diode D1.
　主スイッチング素子ＱｐがターンオフしてトランスＴの１次側から電力の供給がなくなると、２次巻線Ｎｓに逆起電力が発生する。このため電流Ｉが減少し、時刻ｔ０でゼロになる。しかし、電流Ｉはすぐにゼロに収束するのではない。時刻ｔ０から時刻ｔ１までの期間で逆回復電流が増加する。逆回復電流は、時刻ｔ１で最大逆回復電流値Ｉｒｒｍ（Ｍａｘｉｍｕｍ　Ｒｅｖｅｒｓｅ　Ｒｅｃｏｖｅｒｙ　Ｃｕｒｒｅｎｔ）に達する。時刻ｔ０から時刻ｔ１までの期間の長さおよび最大逆回復電流値Ｉｒｒｍの大きさは、ダイオードＤ１０の逆回復特性により定まる。 When the main switching element Qp is turned off and power is not supplied from the primary side of the transformer T, back electromotive force is generated in the secondary winding Ns. Therefore, the current I decreases and becomes zero at time t0. However, the current I does not quickly converge to zero. The reverse recovery current increases during the period from time t0 to time t1. The reverse recovery current reaches the maximum reverse recovery current value Irrm (Maximum Reverse Recovery Current) at time t1. The length of the period from time t0 to time t1 and the magnitude of the maximum reverse recovery current value Irrm are determined by the reverse recovery characteristics of the diode D10.
　時刻ｔ１において、寄生ダイオードＤ１の端子間電圧ＶＤ１よりも先に、ダイオードＤ１０の端子間電圧ＶＤ１０が逆方向に増加を開始する。ダイオードＤ１０の逆回復特性の方が、寄生ダイオードＤ１の逆回復特性よりも良いためである。電流Ｉは、最大逆回復電流値Ｉｒｒｍから減少を開始し、時刻ｔ２でゼロに戻る。 At time t1, the inter-terminal voltage VD10 of the diode D10 starts to increase in the reverse direction before the inter-terminal voltage VD1 of the parasitic diode D1. This is because the reverse recovery characteristic of the diode D10 is better than the reverse recovery characteristic of the parasitic diode D1. The current I starts to decrease from the maximum reverse recovery current value Irrm and returns to zero at time t2.
　時刻ｔ２以降は、２次巻線Ｎｓで発生した逆起電力が、寄生ダイオードＤ１とダイオードＤ１０のインピーダンスの比に応じて分圧される。分圧された逆起電力が同期整流回路１０に印加される。寄生ダイオードＤ１の方がダイオードＤ１０よりも高耐圧でありインピーダンスが大きい。このため、寄生ダイオードＤ１に印加される電圧の方が、ダイオードＤ１０に印加される電圧よりも高い。寄生ダイオードＤ１の端子間電圧ＶＤ１は逆方向に増加を開始する。それに伴って、ダイオードＤ１０の端子間電圧ＶＤ１０は減少を開始する。端子間電圧ＶＤ１および端子間電圧ＶＤ１０は、時刻ｔ３で、寄生ダイオードＤ１とダイオードＤ１０のインピーダンスの比に応じた電圧に収束する。 After time t2, the counter electromotive force generated in the secondary winding Ns is divided according to the impedance ratio of the parasitic diode D1 and the diode D10. The divided back electromotive force is applied to the synchronous rectifier circuit 10. The parasitic diode D1 has a higher breakdown voltage and a larger impedance than the diode D10. For this reason, the voltage applied to the parasitic diode D1 is higher than the voltage applied to the diode D10. The inter-terminal voltage VD1 of the parasitic diode D1 starts increasing in the reverse direction. Accordingly, the voltage VD10 between the terminals of the diode D10 starts to decrease. The inter-terminal voltage VD1 and the inter-terminal voltage VD10 converge to voltages corresponding to the impedance ratio of the parasitic diode D1 and the diode D10 at time t3.
　寄生ダイオードＤ１に高耐圧のダイオードを用いることで、ダイオードＤ１０には逆方向に高電圧が印加されない。このため、ダイオードＤ１０が破壊されることはない。したがって、本発明の実施の形態に係る同期整流回路１０におけるダイオードＤ１０には、従来の同期整流回路２０におけるダイオードＤ２０よりも低耐圧のダイオードを用いることができる。よって、ダイオードＤ１０では、ダイオードＤ２０と比べて、逆回復電流による電力損失を低減できる。 By using a high voltage diode as the parasitic diode D1, a high voltage is not applied to the diode D10 in the reverse direction. For this reason, the diode D10 is not destroyed. Therefore, a diode having a lower withstand voltage than the diode D20 in the conventional synchronous rectifier circuit 20 can be used as the diode D10 in the synchronous rectifier circuit 10 according to the embodiment of the present invention. Therefore, in the diode D10, power loss due to the reverse recovery current can be reduced as compared with the diode D20.
　以上、寄生ダイオードＤ１に高耐圧のダイオードを用いることで、同期整流回路１０に逆方向に電圧が印加されるとき、逆回復電流による電力損失を低減できることを説明した。しかし、逆回復電流だけでなく、順方向電圧降下によっても電力損失は生じる。 As described above, it has been explained that the use of a high voltage diode as the parasitic diode D1 can reduce the power loss due to the reverse recovery current when a voltage is applied to the synchronous rectifier circuit 10 in the reverse direction. However, power loss is caused not only by reverse recovery current but also by forward voltage drop.
　従来の同期整流回路２０に順方向に電圧が印加されるとき、整流スイッチング素子Ｑ２のオン抵抗の抵抗値および抵抗Ｒ２の抵抗値が調整される。これにより、寄生ダイオードＤ２ではなく、整流スイッチング素子Ｑ２を電流が流れるようにすることができる。そのため、順方向電圧降下による電力損失は、寄生ダイオードＤ２では生じず、ダイオードＤ２０でのみ生じる。 When a voltage is applied to the conventional synchronous rectifier circuit 20 in the forward direction, the resistance value of the on-resistance of the rectifying switching element Q2 and the resistance value of the resistor R2 are adjusted. As a result, current can flow through the rectifying switching element Q2 instead of the parasitic diode D2. Therefore, the power loss due to the forward voltage drop does not occur in the parasitic diode D2, but occurs only in the diode D20.
　同様に、本発明の実施の形態に係る同期整流回路１０に順方向に電圧が印加されるとき、整流スイッチング素子Ｑ１のオン抵抗を小さく設定しておくことで、寄生ダイオードＤ１ではなく、整流スイッチング素子Ｑ１を電流が流れる。そのため、順方向電圧降下による電力損失は、寄生ダイオードＤ１では生じない。電力損失はダイオードＤ１０のみで生じる。 Similarly, when a voltage is applied in the forward direction to the synchronous rectifier circuit 10 according to the embodiment of the present invention, the on-resistance of the rectifier switching element Q1 is set to be small so that the rectifier switching is not performed by the parasitic diode D1. A current flows through the element Q1. Therefore, no power loss due to the forward voltage drop occurs in the parasitic diode D1. Power loss occurs only at diode D10.
　ダイオードでは、耐圧と順方向電圧Ｖｆとの間にもトレードオフの関係が一般に成り立つことが知られている。つまり、耐圧が低いほど順方向電圧Ｖｆを低くすることができる。ダイオードＤ１０には、ダイオードＤ２０よりも低耐圧のダイオードを用いることができる。このため、ダイオードＤ１０では、ダイオードＤ２０と比べて、順方向電圧降下による電力損失も低減できる。 It is known that a diode generally has a trade-off relationship between the breakdown voltage and the forward voltage Vf. That is, the lower the breakdown voltage, the lower the forward voltage Vf. As the diode D10, a diode having a lower breakdown voltage than the diode D20 can be used. For this reason, in the diode D10, the power loss due to the forward voltage drop can be reduced as compared with the diode D20.
　以上、本発明の実施の形態に係る同期整流回路１０では、低耐圧で逆回復特性の良いダイオードを用いることが可能になる。このため、同期整流回路１０は、従来の同期整流回路２０と比べて、順方向電圧降下による電力損失および逆回復電流による電力損失の双方を低減できる。 As described above, in the synchronous rectifier circuit 10 according to the embodiment of the present invention, it is possible to use a diode having a low breakdown voltage and good reverse recovery characteristics. For this reason, the synchronous rectifier circuit 10 can reduce both the power loss due to the forward voltage drop and the power loss due to the reverse recovery current, as compared with the conventional synchronous rectifier circuit 20.
　具体的に、低耐圧であるため逆回復特性が良いダイオードとして、ショットキーバリアダイオード（Ｓｃｈｏｔｔｋｙ　Ｂａｒｒｉｅｒ　Ｄｉｏｄｅ）が知られている。ショットキーバリアダイオードは、整流動作の原理上、逆回復電流が非常に小さい。このため、逆回復電流による電力損失がほとんど生じない。そのため、ダイオードＤ１０には、ショットキーバリアダイオードを用いることが好ましい。また、ショットキーバリアダイオードでは、逆回復電流がゼロに収束する際の変化が緩やかである（ソフトリカバリー特性と呼ばれる）。したがって、ショットキーバリアダイオードを用いることで、スイッチング動作時に発生するノイズを低減することもできる。 Specifically, a Schottky Barrier Diode is known as a diode with low breakdown voltage and good reverse recovery characteristics. The Schottky barrier diode has a very small reverse recovery current due to the principle of rectification operation. For this reason, power loss due to the reverse recovery current hardly occurs. Therefore, it is preferable to use a Schottky barrier diode as the diode D10. In the Schottky barrier diode, the change when the reverse recovery current converges to zero is gentle (referred to as soft recovery characteristics). Therefore, by using a Schottky barrier diode, it is possible to reduce noise generated during the switching operation.
　ショットキーバリアダイオード以外にも、ｐｎ接合ダイオードおよびｐｉｎ接合ダイオードも、低耐圧の場合には逆回復特性が良い。そのため、ダイオードＤ１０にｐｎ接合ダイオードおよびｐｉｎ接合ダイオードを用いることにより、逆回復電流による電力損失を低減できる。 In addition to Schottky barrier diodes, pn junction diodes and pin junction diodes also have good reverse recovery characteristics when the breakdown voltage is low. Therefore, power loss due to reverse recovery current can be reduced by using a pn junction diode and a pin junction diode for the diode D10.
　なお、本発明の実施の形態に係る同期整流回路１０では、ダイオードＤ１０のカソードが整流スイッチング素子Ｑ１のソースに接続される向きにダイオードＤ１０を接続した。しかし、ダイオードＤ１０の接続の向きは、これに限定されるものではない。ダイオードＤ１０のアノードが整流スイッチング素子Ｑ１のドレインに接続される向きであっても、同様の効果を得ることができる。 In the synchronous rectification circuit 10 according to the embodiment of the present invention, the diode D10 is connected in the direction in which the cathode of the diode D10 is connected to the source of the rectification switching element Q1. However, the connection direction of the diode D10 is not limited to this. The same effect can be obtained even when the anode of the diode D10 is connected to the drain of the rectifying switching element Q1.
　また、整流スイッチング素子Ｑ１は、寄生ダイオードＤ１を含むスイッチング素子に限定されるものではない。整流スイッチング素子Ｑ１に並列に接続したダイオードも、整流スイッチング素子Ｑ１の寄生ダイオードＤ１に限定されるものではない。整流スイッチング素子Ｑ１が寄生ダイオードＤ１を含まない場合、寄生ダイオードＤ１に代えて、ダイオードＤ１０よりも高耐圧のダイオードが整流スイッチング素子Ｑ１に並列に接続されることで、同様の効果を得ることができる。 Further, the rectifying switching element Q1 is not limited to the switching element including the parasitic diode D1. The diode connected in parallel to the rectifying switching element Q1 is not limited to the parasitic diode D1 of the rectifying switching element Q1. When the rectifying switching element Q1 does not include the parasitic diode D1, a similar effect can be obtained by connecting a diode having a higher breakdown voltage than the diode D10 in parallel to the rectifying switching element Q1 instead of the parasitic diode D1. .
　ただし、ダイオードは、高耐圧になると順方向電圧降下による電力損失が増加する。たとえば、ｐｉｎ接合ダイオードは、高耐圧の場合には、逆回復特性は比較的良い。しかし、順方向電圧Ｖｆが高いため、順方向電圧降下による電力損失が増加してしまう。また、６００Ｖ程度の高耐圧のショットキーバリアダイオードとして、ＧａＮ（窒化ガリウム）ショットキーバリアダイオードおよびＳｉＣ（シリコンカーバイド）ショットキーバリアダイオードが知られている。これら高耐圧のショットキーバリアダイオードも、順方向電圧Ｖｆが高い。そのため、順方向電圧降下による電力損失が増加してしまう。したがって、同期整流回路１０に用いるダイオードは、耐圧と電力損失とのバランスを考慮して決定されるべきである。 However, the power loss due to the forward voltage drop increases when the diode has a high breakdown voltage. For example, a pin junction diode has a relatively good reverse recovery characteristic when it has a high breakdown voltage. However, since the forward voltage Vf is high, the power loss due to the forward voltage drop increases. Further, GaN (gallium nitride) Schottky barrier diodes and SiC (silicon carbide) Schottky barrier diodes are known as Schottky barrier diodes having a high breakdown voltage of about 600 V. These high breakdown voltage Schottky barrier diodes also have a high forward voltage Vf. Therefore, the power loss due to the forward voltage drop increases. Therefore, the diode used for the synchronous rectifier circuit 10 should be determined in consideration of the balance between withstand voltage and power loss.
　本発明の実施の形態に係る同期整流回路として、主スイッチング素子Ｑｐのスイッチング動作と同期する同期整流回路１０を例に説明した。しかし、本発明に係る「同期整流回路」は、これに限定されるものではない。同期整流回路１０は、逆方向に電圧が印加されて逆回復電流が流れる同期整流回路全般で、同様の効果を得ることができる。整流スイッチング素子Ｑ１は、主スイッチング素子Ｑｐのスイッチング動作と同期していなくてもよい。 As a synchronous rectifier circuit according to the embodiment of the present invention, the synchronous rectifier circuit 10 synchronized with the switching operation of the main switching element Qp has been described as an example. However, the “synchronous rectifier circuit” according to the present invention is not limited to this. The synchronous rectifier circuit 10 can obtain the same effect in general synchronous rectifier circuits in which a voltage is applied in the reverse direction and a reverse recovery current flows. The rectifying switching element Q1 may not be synchronized with the switching operation of the main switching element Qp.
　また、本発明の実施の形態に係る同期整流回路１０を備えたスイッチング電源装置として、共振リセット形フォワードコンバータ１を例に、トランスＴで入力電源Ｖｉｎと出力端子Ｖｏｕｔとを絶縁する場合について説明した。しかし、本発明に係る「同期整流回路」は、これに限定されるものでもない。同期整流回路１０は、逆方向に電圧が印加されて逆回復電流が流れる同期整流回路を備えるスイッチング電源装置全般に適用できる。スイッチング電源装置が絶縁型および非絶縁型のいずれであるかを問わず、回路方式も問わない。このため、同期整流回路１０を備えたスイッチング電源装置は、パワーコンディショナのＤＣ－ＤＣコンバータ、非絶縁型ＤＣ－ＤＣコンバータ、またはインバータなどであってもよい。 Further, as the switching power supply device including the synchronous rectifier circuit 10 according to the embodiment of the present invention, the case where the input power source Vin and the output terminal Vout are insulated by the transformer T has been described using the resonance reset type forward converter 1 as an example. . However, the “synchronous rectifier circuit” according to the present invention is not limited to this. The synchronous rectifier circuit 10 can be applied to all switching power supply devices including a synchronous rectifier circuit in which a voltage is applied in the reverse direction and a reverse recovery current flows. Regardless of whether the switching power supply device is an insulating type or a non-insulating type, the circuit system is not limited. Therefore, the switching power supply device including the synchronous rectifier circuit 10 may be a DC-DC converter, a non-insulated DC-DC converter, an inverter, or the like of a power conditioner.
　今回開示された実施の形態はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は、上記した説明ではなく、請求の範囲によって示され、請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。 The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
　Ｔ　トランス、Ｎｐ　１次巻線、Ｎｓ　２次巻線、Ｌ　チョークコイル、Ｃ　コンデンサ、Ｑｐ　主スイッチング素子、Ｑｓ　転流スイッチング素子、Ｑ，Ｑ１，Ｑ２　整流スイッチング素子、Ｄ，Ｄ１，Ｄ２　寄生ダイオード、Ｄ１０，Ｄ２０　ダイオード、Ｒ２　抵抗、１，２　共振リセット形フォワードコンバータ、１０，２０　同期整流回路、Ｖｉｎ　入力電源、Ｖｏｕｔ　出力端子、Ｉ　電流、Ｉｒｒｍ　最大逆回復電流値、Ｖｆ　順方向電圧、ＶＤ１，ＶＤ１０　端子間電圧、ｔ０，ｔ１，ｔ２，ｔ３　時刻。 T transformer, Np primary winding, Ns secondary winding, L choke coil, C capacitor, Qp main switching element, Qs commutation switching element, Q, Q1, Q2 rectification switching element, D, D1, D2 parasitic diode, D10, D20 diode, R2 resistor, 1, 2 resonant reset type forward converter, 10, 20 synchronous rectifier circuit, Vin input power supply, Vout output terminal, I current, Irrm maximum reverse recovery current value, Vf forward voltage, VD1, VD10 Terminal voltage, t0, t1, t2, t3 time.

Claims (7)

  1. 　整流スイッチング素子と、
    　前記整流スイッチング素子に並列に接続された第１のダイオードと、
    　前記整流スイッチング素子と前記第１のダイオードとの並列回路に直列に接続された第２のダイオードとを備え、
    　前記第２のダイオードの耐圧は、前記第１のダイオードの耐圧よりも低い、同期整流回路。     A rectifying switching element;
    A first diode connected in parallel to the rectifying switching element;
    A second diode connected in series to a parallel circuit of the rectifying switching element and the first diode;
    The synchronous rectifier circuit, wherein a breakdown voltage of the second diode is lower than a breakdown voltage of the first diode.
  2. 　前記第２のダイオードは、ショットキーバリアダイオードである、請求項１に記載の同期整流回路。 The synchronous rectifier circuit according to claim 1, wherein the second diode is a Schottky barrier diode.
  3. 　前記第２のダイオードは、ｐｎ接合ダイオードまたはｐｉｎ接合ダイオードである、請求項１に記載の同期整流回路。 The synchronous rectifier circuit according to claim 1, wherein the second diode is a pn junction diode or a pin junction diode.
  4. 　前記整流スイッチング素子は、ＦＥＴであって、
    　前記第１のダイオードは、前記ＦＥＴの寄生ダイオードである、請求項１～３のいずれか一項に記載の同期整流回路。     The rectifying switching element is an FET,
    The synchronous rectifier circuit according to any one of claims 1 to 3, wherein the first diode is a parasitic diode of the FET.
  5. 　請求項１～４のいずれか一項に記載の同期整流回路と、
    　入力電源と、
    　前記入力電源に直列に接続され、制御信号に基づいてスイッチング動作する主スイッチング素子と、
    　前記同期整流回路が整流した電圧を出力する出力端子とを備え、
    　前記同期整流回路は、印加された電圧を、前記主スイッチング素子のスイッチング動作と同期して整流する、スイッチング電源装置。     The synchronous rectifier circuit according to any one of claims 1 to 4,
    Input power,
    A main switching element connected in series to the input power source and performing a switching operation based on a control signal;
    An output terminal for outputting the voltage rectified by the synchronous rectifier circuit,
    The synchronous rectifier circuit rectifies an applied voltage in synchronization with a switching operation of the main switching element.
  6. 　前記入力電源と前記出力端子とを絶縁するトランスをさらに備える、請求項５に記載のスイッチング電源装置。 The switching power supply device according to claim 5, further comprising a transformer that insulates the input power supply from the output terminal.
  7. 　前記スイッチング電源装置は、前記トランスの２次側に、転流スイッチング素子とインダクタンス素子とをさらに備え、
    　前記転流スイッチング素子は、前記トランスの２次巻線と前記同期整流回路との直列回路に直列に接続され、
    　前記インダクタンス素子は、前記２次巻線と前記転流スイッチング素子との接続点と、前記出力端子の一端との間に直列に接続された、請求項６に記載のスイッチング電源装置。     The switching power supply device further includes a commutation switching element and an inductance element on the secondary side of the transformer,
    The commutation switching element is connected in series to a series circuit of a secondary winding of the transformer and the synchronous rectification circuit,
    The switching power supply device according to claim 6, wherein the inductance element is connected in series between a connection point between the secondary winding and the commutation switching element and one end of the output terminal.
PCT/JP2013/054694 2012-03-02 2013-02-25 Synchronous rectification circuit and switching power source device comprising same WO2013129288A1 (en)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61157274A (en) * 1984-12-27 1986-07-16 Fuji Electric Co Ltd Inverter circuit
JPH04127869A (en) * 1990-09-18 1992-04-28 Nippon Telegr & Teleph Corp <Ntt> Rectifying circuit
JPH05316726A (en) * 1992-05-02 1993-11-26 Hitachi Metals Ltd Switching power source
JPH09154276A (en) * 1995-09-26 1997-06-10 Fujitsu Denso Ltd Synchronous rectifier circuit
JPH09215199A (en) * 1996-02-02 1997-08-15 Fujitsu Ltd Parallel-connected harmonic compensating circuit
JP2001238348A (en) * 2000-02-21 2001-08-31 Nissan Motor Co Ltd Protection circuit for power supply with inductive load
JP2008198735A (en) * 2007-02-09 2008-08-28 Sanken Electric Co Ltd Composite semiconductor device including rectifier element

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61157274A (en) * 1984-12-27 1986-07-16 Fuji Electric Co Ltd Inverter circuit
JPH04127869A (en) * 1990-09-18 1992-04-28 Nippon Telegr & Teleph Corp <Ntt> Rectifying circuit
JPH05316726A (en) * 1992-05-02 1993-11-26 Hitachi Metals Ltd Switching power source
JPH09154276A (en) * 1995-09-26 1997-06-10 Fujitsu Denso Ltd Synchronous rectifier circuit
JPH09215199A (en) * 1996-02-02 1997-08-15 Fujitsu Ltd Parallel-connected harmonic compensating circuit
JP2001238348A (en) * 2000-02-21 2001-08-31 Nissan Motor Co Ltd Protection circuit for power supply with inductive load
JP2008198735A (en) * 2007-02-09 2008-08-28 Sanken Electric Co Ltd Composite semiconductor device including rectifier element

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