JP4812433B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply device that achieves high efficiency, miniaturization, and cost reduction.

As a conventional switching power supply device, as shown in FIG. 6, the primary side, and an input to both ends of a DC power source V _IN choke L _IN and the first switching element Q1 connected in series, between the terminals of the switch element Q1 The primary winding Np of the transformer T and the first capacitor C1 are connected in series, and the second switch element Q2 and the second capacitor C2 are connected in series between the primary winding Np terminals of the transformer T. The so-called boost half bridge is constructed, and the secondary side is configured by providing a center tap on the secondary winding Ns and connecting a rectifier circuit including an output choke and a smoothing capacitor to both ends of the secondary winding Ns. A switching power supply device (hereinafter referred to as “BHB”) system switching power supply device is known (see Patent Document 1).

Further, as another conventional switching power supply device, as shown in FIG. 7, the primary side is connected in series with the primary winding Np of the transformer T and the first switch element Q1 at both ends of the DC power supply _VIN , The second switch element Q2 and the capacitor C1 are connected in series to both ends of the first switch element Q1, and the secondary side includes the first rectifier element D1, the tertiary winding Nr, and the output choke Lo. A configuration in which a series circuit of a secondary winding Ns and a second rectifying element D2 is connected in series and connected in parallel to the first rectifying element D1 is known (see Patent Document 2).
JP-A-11-262263 JP 2004-320916 A

  However, the former switching power supply can perform zero volt switching (hereinafter referred to as “ZVS”) by using the leakage inductance current near the rated load, but this current decreases in the light load region, making ZVS difficult. It is. On the other hand, if the leakage inductance value is such that ZVS can be achieved even in a light load region, the dead time becomes longer, resulting in a problem that the efficiency is reduced.

  The latter switching power supply device has a primary side, a transformer primary winding and a first switch element connected in series at both ends of a direct current, and a second switch element and a capacitor at both ends of the first switch element. Are connected in series, and there is a problem that the input ripple is relatively large.

  The present invention has been made in view of the above problems, and provides a switching power supply device that realizes an expansion of the zero volt switching range and can reduce input ripple as compared with a conventional circuit.

  In order to solve the above problems, a switching power supply according to the present invention includes a DC power supply, a series circuit of an input choke and a first switch element, and a primary winding of a transformer connected between terminals of the switch element. A series circuit of a first capacitor, a series circuit of a second switch element and a second capacitor connected between terminals of the primary winding, a first rectifier element and a secondary winding of a transformer; A series circuit of a tertiary winding of the transformer and an output choke, a second rectifying element connected in parallel with the series circuit of the first rectifying element and the secondary winding, and a smoothing capacitor. Features.

  A switching power supply according to the present invention includes a DC power supply, a series circuit of an input choke, a tertiary winding of a transformer, and a first switch element, a primary winding of a transformer connected between terminals of the switch element, A series circuit of one capacitor, a series circuit of a second switch element and a second capacitor connected between the terminals of the primary winding, one end of the secondary winding divided by the center tap, and a negative A first rectifier connected to the output terminal, a second rectifier connected to the other end of the secondary winding and the negative output terminal, the center tap and the output choke connected in series, and the output choke And a smoothing capacitor connected in series with each of the two rectifying elements.

  A switching power supply according to the present invention includes a DC power supply, a series circuit of a first primary winding of a transformer and a first switch element, and a second primary winding of a transformer connected between terminals of the switch element. A series circuit of a line and a first capacitor, a series circuit of a second switch element and a second capacitor connected between the terminals of the second primary winding, a first rectifier element and a transformer A series circuit of a secondary winding, a tertiary winding of a transformer, and an output choke; a second rectifying element connected in parallel with the series circuit of the first rectifying element and the secondary winding; and a smoothing capacitor It is characterized by having.

  Further, the rectifying element is a MOSFET or other switching element.

  According to the present invention, the ripple can be reduced as compared with the conventional switching power supply device. In addition, in the BHB type switching power supply device, there is a problem that the dead time becomes longer and the efficiency decreases when the leakage inductance value that allows ZVS to flow in a high input voltage range and a middle load range is used. According to the invention, even if the leakage inductance value is not large, the parasitic capacitance discharge current of the first switch element is increased even in a high input voltage range and a medium load range, and ZVS can be performed while suppressing a decrease in efficiency.

FIG. 1 shows the best mode for carrying out the present invention. The switching power supply according to the present embodiment employs a BHB switching power supply and includes an output transformer T having a primary winding Np, a secondary winding Ns, and a tertiary winding Nr. Further, an input choke L _IN and a first switch element Q1 are connected in series to both ends of the DC power source V _IN , and a primary winding Np and a first capacitor C1 are connected in series to both ends of the first switch element Q1. A series circuit of a second switch element Q2 and a second capacitor C2 is connected to both ends of the primary winding Np.

  On the secondary side, the first rectifying element D1, the secondary winding Ns, the tertiary winding Nr, and the output choke Lo are connected in series, and the first rectifying element D1 and the secondary winding Ns are connected in series. A rectifier circuit is configured by connecting a second rectifier element D2 in parallel with the circuit and providing a smoothing capacitor Co on the output side.

The switching power supply device configured as described above operates as follows. The circuit operation will be described with reference to FIG. 2 which is an equivalent circuit diagram and FIG. 3 which is a voltage and current waveform of each part. First, at the time T0 shown in FIG. 3, the first switch element Q1 is turned on, but the input voltage is applied to the leakage inductance Lr, and the current ILr has a slope of V _IN (T1-T0) / Lr. To increase. Each transformer winding is in a short circuit state, and power is not supplied to the secondary side. This is a commutation period in which the first rectifier diode D1 and the second rectifier diode D2 on the secondary side are both conductive.

  Subsequently, as shown in FIG. 3, at time T1, the primary side current ILr reaches the primary conversion value of the output choke current ILo, and a voltage is generated in each transformer winding. All of the current flowing through the first rectifier diode D1 and the second rectifier diode D2 on the secondary side is transferred to the second rectifier diode D2, and power supply from the primary winding Np to the secondary side is started.

  At time T2, the first switch element Q1 is turned off, but the energy stored in the leakage inductance Lr charges the parasitic capacitor CQ1 of the first switch element Q1, and discharges the parasitic capacitor CQ2 of the second switch element Q2. Current flows, and power supply to the secondary side continues.

  At time T3, the parasitic capacitance CQ2 of the second switch element Q2 is discharged to zero volts, and the parasitic diode DQ2 of the second switch element Q2 becomes conductive. The primary winding voltage becomes zero volts, and a commutation period occurs in which both the first rectifier diode D1 and the second rectifier diode D2 on the secondary side are in conduction.

  At time T4, the second switch element Q2 is turned on. At this time, since the parasitic diode DQ2 of the second switch element Q2 is in a conductive state, it becomes ZVS. The secondary side is still in the commutation period.

  At time T5, the primary side current ILr reaches the primary conversion value of the output choke current ILo, and all the currents flowing through the first rectifier diode D1 and the second rectifier diode D2 on the secondary side are all on the secondary side. The process proceeds to the first rectifier diode D1, and the power supply to the secondary side is started by the clamp on the transformer primary side and the release of the energy stored in the second capacitor C2. The tertiary winding Nr current increases and is superimposed on the exciting inductor current ILp, and the second switch element Q2 current increases.

  The second switch element Q2 is turned off at time T6, but the current that charges the parasitic capacitance CQ2 of the second switch element Q2 and discharges the parasitic capacitor CQ1 of the first switch element Q1 by the energy accumulated in the leakage inductance Lr. Flows. These currents are ZVS currents, which are increased from the normal method due to the tertiary winding Nr current. For this reason, the ZVS range can be expanded as compared with the normal method. The power supply to the secondary side is sustained.

  At time T7, the parasitic capacitance CQ1 of the first switch element Q1 is discharged to zero volts, and the parasitic diode DQ1 of the first switch element Q1 becomes conductive. The total value of both primary winding voltages becomes zero volts, and it becomes a commutation period in which the first rectifier diode D1 and the second rectifier diode D2 on the secondary side are both conducting. When the first switch element Q1 is turned on in the next cycle, the parasitic diode DQ1 of the first switch element Q1 is in a conductive state, and thus becomes ZVS.

  The switching power supply according to the present embodiment can reduce the input ripple as compared with the conventional switching power supply by the operation as described above. In addition, in the BHB type switching power supply device, there is a problem that the dead time becomes longer and the efficiency is lowered when the leakage inductance value that allows ZVS to flow in a high input voltage range and a medium load range is used. According to the present invention, ZVS can be performed while suppressing a decrease in efficiency even in a high input voltage range and a medium load range.

  In this embodiment, the diodes D1 and D2 are used as the secondary-side rectifier elements, but a synchronous rectification method using a switching element such as a MOSFET may be employed.

Next, FIG. 4 shows a second embodiment different from FIG. In the switching power supply according to this embodiment, a tertiary winding Nr is provided on the primary side, a center tap is provided on the secondary side, and the secondary winding Ns is divided into two. An input choke L _IN , a tertiary winding Nr, and a first switch element Q1 are connected in series to both ends of the DC power source V _IN . A primary winding Np and a first capacitor C1 are connected in series to both ends of the first switch element Q1. A series circuit of a second switch element Q2 and a second capacitor C2 is connected to both ends of the primary winding Np.

  On the secondary side, the cathodes of the rectifying elements D1 and D2 are connected to the ends of the secondary windings Ns1 and Ns2 divided by the center tap, respectively, and the anodes of the rectifying elements D1 and D2 are connected to the negative side of the output part. It is. The center tap is connected to the positive side of the output unit. An output choke Lo and a smoothing capacitor Co are provided on the output side.

  The switching power supply configured as described above operates in the same manner as the switching power supply. Therefore, detailed description is omitted. In this embodiment, the diodes D1 and D2 are used as the secondary-side rectifier elements, but a synchronous rectification method using a switching element such as a MOSFET may be employed.

Next, FIG. 5 shows a third embodiment different from FIG. The switching power supply according to the present embodiment employs a BHB switching power supply and has a first primary winding Np1, a second primary winding Np2, a secondary winding Ns, and a tertiary winding Nr. An output transformer T is included. Further, a first primary winding Np1 and a first switch element Q1 are connected in series to both ends of the DC power source _VIN , and a second primary winding Np2 and a first switch are connected to both ends of the first switch element Q1. Are connected in series, and a series circuit of a second switch element Q2 and a second capacitor C2 is connected to both ends of the second primary winding Np2.

  On the secondary side, the first rectifying element D1, the secondary winding Ns, the tertiary winding Nr, and the output choke Lo are connected in series, and the first rectifying element D1 and the secondary winding Ns are connected in series. A rectifier circuit is configured by connecting a second rectifier element D2 in parallel with the circuit and providing a smoothing capacitor Co on the output side.

  The switching power supply configured as described above operates in the same manner as the switching power supply. Therefore, detailed description is omitted. In this embodiment, the diodes D1 and D2 are used as the secondary-side rectifier elements, but a synchronous rectification method using a switching element such as a MOSFET may be employed.

  According to the present invention, compared to a conventional BHB type switching power supply device, ZVS can be performed while suppressing a decrease in efficiency even in a high input voltage range and a medium load range, which is industrially applicable.

1 is a circuit configuration diagram of a first embodiment of a switching power supply device according to the present invention. 1 is an equivalent circuit diagram of a switching power supply device according to the present invention. It is an operation | movement waveform diagram of the switching power supply device which concerns on this invention. It is a circuit block diagram of the switching power supply device of 2nd embodiment. It is a circuit block diagram of the switching power supply device of 3rd embodiment. It is a circuit block diagram of the conventional switching power supply device. Similarly, it is a circuit block diagram of the conventional switching power supply device.

Explanation of symbols

T transformer Q switch element L choke C capacitor D diode Np primary winding Ns secondary winding Nr tertiary winding

Claims (2)

A series circuit of a DC power supply, an input choke, a tertiary winding of the transformer, and a first switch element; a series circuit of a primary winding of the transformer and a first capacitor connected between the terminals of the switch element; A first rectifier connected to a series circuit of a second switch element and a second capacitor connected between the terminals of the primary winding, one end of the secondary winding divided by the center tap, and a negative output terminal An element, a second rectifying element connected to the other end of the secondary winding and a negative output terminal, the center tap and the output choke connected in series, the other end of the output choke and the two rectifying elements And a smoothing capacitor connected in series with each other. 2. The switching power supply device according to claim 1, wherein the rectifying element is a MOSFET or other switching element.

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