WO2006054444A1

WO2006054444A1 - Multioutput switching power supply

Info

Publication number: WO2006054444A1
Application number: PCT/JP2005/020119
Authority: WO
Inventors: Yoshikazu Mizuno; Seiji Oda
Original assignee: Cosel Co., Ltd.
Priority date: 2004-11-19
Filing date: 2005-11-01
Publication date: 2006-05-26
Also published as: JP2006149092A

Abstract

A multioutput switching power supply having an improved efficiency by reducing the load variation through a simple arrangement and reducing the loss due to the dummy resistor for suppressing the load variation. A primary circuit is provided by connecting the primary winding (F1) of a transformer (2) and a main switching element (3) in series to a DC power supply (1), and the transformer (2) is provided with a plurality of secondary windings (S1) and (S2). The switching element (3) is switched and fly-back voltages induced in the plurality of secondary windings (S1) and (S2) of the transformer (2) are rectified by rectification elements (14, 15), respectively. The rectified outputs are connected in series and smoothed, thus supplying an output voltage. The plus-side terminals of the fly-back voltages induced in the secondary windings (S1, S2) of the transformer (2) are connected to the respective plus-side terminals of the rectification elements (14, 15) which are connected through a capacitor (12).

Description

Specification

Multi-output switching power supply

Technical field

The present invention relates to a switching power supply device that converts a DC input voltage into a desired voltage and supplies it to an electronic device, and particularly relates to a multi-output switching power supply device having a plurality of outputs.

Background art

Conventionally, a flyback-type multi-output switching power supply device has a circuit configuration as shown in FIG. 6, for example. In the circuit of this switching power supply device, a DC power supply 1 is connected to a series circuit composed of a primary winding F1 of a transformer 2 and a switching element 3. The switching element 3 also has a semiconductor switch element force such as a MOS-FET. The gate of the switching element 3 is connected to the output of the control circuit 8 that controls the on-duty of switching to control the output voltage.

[0003] The transformer 2 is provided with two secondary windings Sl and S2, and the terminals of the secondary windings Sl and S2 that have no dots are connected to the anodes of the rectifying diodes 4 and 5, respectively. Yes. The force sword of one rectifying diode 4 is connected to the output terminal 21 and to one end of the smoothing capacitor 6. The other end of the smoothing capacitor 6 is connected to the terminal on the side of the secondary winding S 2 with dots, and is connected to the output terminal 22. Further, the force sword of the other rectifying diode 5 is connected to the output terminal 22 and is connected to one end of the smoothing capacitor 7, and the other end of the smoothing capacitor 7 is attached with a dot of the secondary winding S1. Is connected to the output terminal 23 and connected to the output terminal 23. Outputs from the output terminals 21 and 23 are fed back to the control circuit 8 via the amplifier 11.

In the flyback multi-output power supply circuit shown in FIG. 6, energy is stored in the transformer 2 during the ON period of the switching element 3 on the primary side, and the rectifying diode 4 is stored during the OFF period of the switching element 3. Energy is supplied to the output through 5. The flyback voltages El and E2 of the secondary windings SI and S2 generated during the off period of the switching element 3 are generated in proportion to the respective power numbers with respect to the input voltage Vin. And secondary flyback SI, S2 flyback From the voltages El and E2, the smoothing capacitors 6 and 7 are charged through the rectifying diodes 4 and 5, and the output voltages Vol and Vo2 are supplied to the output terminals 21, 22, and 23. This output voltage is controlled by a combined voltage obtained by rectifying and smoothing the voltage generated at each secondary winding SI and S2 through the amplifier 11 with the output terminal 22 on the power sword side of the rectifying diode 5 being a negative potential. Input to control circuit 8 to stabilize the output.

Patent Document 1: JP-A-60-35957

Patent Document 2: JP-A-6-54532

Disclosure of the invention

Problems to be solved by the invention

In the case of this flyback type multi-output switching power supply, as shown in the equivalent circuit shown in FIG. 7, the leakage inductance between the transformer 2 and the rectifying diodes 4 and 5 depends on the wiring pattern of the circuit board, etc. A leakage inductance component 9, 10 such as a parasitic inductance is inserted in series. A rectified current flows through the leakage inductance components 9 and 10 every time the switching element 3 is switched. For this reason, when a load current is applied only to the output on one side or when an imbalance occurs in the load, the voltage drop generated by leakage inductance components such as leakage inductance increases on the output side where the load current flows. For this reason, the voltage on the output side that allows current to flow through the load decreases, the voltage on the output side that does not carry current or little increases, and the load fluctuation increases. This occurs because the combined voltage of the output is fed back to control the output voltage!

[0006] If the leakage inductance of the transformer 2 is a combined value of the leakage inductance component due to the parasitic inductance, the voltage drop Ve generated by the leakage inductance component Le is expressed as follows.

[0007] Ve = Le X (di / dt)

Here, (diZdt) is the slope of the current flowing in the leakage inductance component.

[0008] Therefore, the output voltage will not rise significantly above the target voltage due to the load! As shown in Fig. 8, output resistance at light load is increased by connecting a dummy resistor between output terminals 21, 22 and 22, 23, and consuming the minimum load current a by the dummy resistor. It is trying to prevent. [0009] Therefore, in the above conventional case, there is a problem that the loss due to the dummy resistor reduces the efficiency of the power supply! In addition, some transformers are made of a laminated substrate so as to reduce such leakage components, but there is a problem that the configuration becomes complicated and the cost increases.

[0010] Further, as disclosed in Patent Documents 1 and 2, a configuration in which the magnetic cores of the coils of the multi-output switching power supply circuit are shared is proposed in order to suppress the loss due to the dummy resistance. However, a sufficient effect on the above-mentioned problem has not been obtained.

[0011] The present invention has been made in view of the above-described problems of the conventional technology. With a simple configuration, the load variation is reduced, and the loss due to the dummy resistor for suppressing the load variation is reduced. An object of the present invention is to provide a multi-output switching power supply device capable of improving the efficiency of the power supply.

Means for solving the problem

[0012] The present invention includes a primary circuit in which a primary winding of a transformer and a main switching element are connected in series to a DC power source, and a plurality of secondary windings are provided in the transformer, and the switching is performed. By switching the elements, the flyback voltage generated in the secondary windings of the transformer is rectified by rectifying elements such as diodes, and the rectified outputs are connected in series to smooth the outputs. A flyback type multi-output switching power supply device that controls the output voltage by feed-knocking the combined voltage of the plurality of output voltages, and each secondary winding of the transformer A multi-output comprising a positive terminal of each rectifying element connected to each positive terminal of a flyback voltage generated in the circuit, and a positive terminal connected to each rectifying element via a capacitor. Sui A quenching power supply.

[0013] Further, the present invention includes a primary circuit in which a primary winding of a transformer and a main switching element are connected in series to a DC power source, the transformer is provided with a plurality of secondary windings, and the switch Switching elements, and a plurality of rectifying elements such as diodes for rectifying the AC voltages generated on the plurality of secondary windings of the transformer, respectively, and one end of the secondary winding on the side where the dots are located. A choke coil connected and connected to the output terminal at the other end, a plurality of return elements connected between one end of the choke coil and the non-dotted side of the secondary winding, and smoothing each output And a smoothing capacitor that performs a feedback operation on the combined voltage of the plurality of output voltages. The forward type multi-output switching power supply device that controls the output voltage by clicking, and the midpoint between each minus terminal of each rectifying element and each choke coil is connected via a capacitor. This is a multi-output switching power supply device connected.

[0014] The rectifying element is a diode, and the capacitor is formed by connecting the anode terminal of each diode. Alternatively, a synchronous rectification may be performed using a transistor for the rectification-requiring element. Furthermore, in the forward type multi-output switching power supply device, the magnetic core may be shared by a plurality of choke coils connected to each of the rectifying elements.

[0015] The multi-output switching power supply device of the present invention reduces load fluctuations and suppresses losses due to dummy resistors for reducing load fluctuations by simply connecting a capacitor between rectifying elements, and improves the efficiency of the power supply device. Can be increased. In addition, since the number of dummy resistance elements can be reduced, the circuit mounting area can be reduced, the components of the power supply device can be made smaller, and the power supply device as a whole can be reduced in size and cost. It contributes.

Brief Description of Drawings

FIG. 1 is a schematic circuit diagram of a multi-output switching power supply device according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the multi-output switching power supply device according to the first embodiment of the present invention.

FIG. 3 is a graph showing output current and output voltage of the multi-output switching power supply device according to the first embodiment of the present invention.

FIG. 4 is a schematic circuit diagram of a multi-output switching power supply device according to a second embodiment of the present invention.

FIG. 5 is an equivalent circuit diagram of the multi-output switching power supply device according to the second embodiment of the present invention.

FIG. 6 is a schematic circuit diagram of a conventional flyback multi-output switching power supply device.

FIG. 7 is an equivalent circuit diagram of a conventional flyback type multi-output switching power supply device. FIG. 8 is a graph showing output current and output voltage of a conventional flyback multi-output switching power supply.

Explanation of symbols

[0017] 1 DC power supply

2 lance

3 Switching element

6, 7 Smoothing capacitor

8 Control circuit

9, 10 Leakage inductance component

12 capacitors

14, 15 Rectifier element

21, 22, 23 Output terminal

Fl Primary shoreline

SI, S2 secondary cable

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a power supply circuit of a flyback type multi-output switching power supply apparatus according to the first embodiment of the present invention. The same components as those of the power supply circuit shown in FIG. In the multi-output switching power supply device of this embodiment, a DC power supply 1 is connected to a series circuit composed of a primary winding F1 of a transformer 2 and a switching element 3. The switching element 3 is composed of a semiconductor switch element such as a MOS-FET. The gate of the switching element 3 is connected to the output of the control circuit 8 that controls the on-duty of switching to control the output voltage.

[0019] The transformer 2 is provided with two secondary windings Sl and S2. The terminals without secondary dots of the secondary windings Sl and S2 are respectively connected to the positive side terminals which are the anodes of the rectifying elements 14 and 15 such as the rectifying diode. A negative side terminal, which is a force sword of one rectifying element 14, is connected to an output terminal 21 and to one end of one smoothing capacitor 6. The other end of the smoothing capacitor 6 is connected to the terminal on the side where the dot of the secondary winding S2 is attached and also connected to the output terminal 22. The force of the other rectifying element 15 The negative terminal, which is a sword, is connected to the output terminal 22 and to one end of the other smoothing capacitor 7. The other end of the smoothing capacitor 7 is connected to a terminal on the side where the secondary winding S1 is attached, and is connected to the output terminal 23. Outputs from the output terminals 21 and 23 are fed back to the control circuit 8 via the amplifier 11.

[0020] In addition, between each terminal of the secondary winding Sl, S2, which has no dot, and the positive terminal, which is each of the rectifying elements 14, 15, is connected! / A capacitor 12 is provided.

[0021] As the rectifying elements 14 and 15 of this embodiment, for example, a Schottky diode, a first tricano diode, or the like may be used, and a transistor may be used. As the capacitor 12, a ceramic capacitor, an aluminum electrolytic capacitor, a functional polymer electrolytic capacitor, or the like can be used as appropriate.

[0022] In the flyback multi-output power supply circuit shown in Fig. 1, energy is stored in the transformer 2 during the ON period of the primary side switching element 3, and the secondary winding Sl is stored during the OFF period of the switching element 3. The flyback voltage due to S2 is applied to the output side through the rectifying elements 14 and 15, and energy is supplied. The flyback voltages El and E2 of the secondary windings S1 and S2 generated during the OFF period of the switching element 3 are generated in proportion to the respective power numbers with respect to the input voltage Vin. Then, the flyback voltages El and E2 of the secondary windings SI and S 2 are applied to the positive side terminals of the rectifying elements 14 and 15, the smoothing capacitors 6 and 7 are charged, and the output terminals 21, 22 and 23 Are supplied with output voltages Vol and Vo2. This output voltage is controlled by combining the voltage generated on the secondary windings SI and S2 with the output terminal 22 on the negative side of the rectifying element 15 on the negative side, and a combined voltage obtained by rectifying and smoothing the voltage via the amplifier 11. Input to 8 stabilizes output.

[0023] The flyback multi-output power supply circuit of this embodiment also has a leakage inductance between the transformer 2 and the rectifying elements 14 and 15, a parasitic inductance due to a pattern, etc., as in the equivalent circuit shown in FIG. Leakage inductance component of 9, 10 force It becomes a circuit inserted in series. A rectified current flows through the leakage inductance components 9 and 10 every time the switching element 3 is switched. Therefore, when a load current is applied only to the output on one side or when an imbalance occurs in the load, the output side where the load current is flowing has a voltage drop caused by leakage inductance components 9, 10 such as leakage inductance. big Become. For this reason, the voltage on the output side that allows current to flow through the load decreases, the voltage on the output side that does not pass current or little increases, and the load fluctuation increases. This occurs because the output voltage is controlled by feeding back the combined voltage of the output as described above.

In this embodiment, the switching element 3 is turned off, and the voltage drop caused by the leakage inductance components 9 and 10 is corrected by the capacitor 12 connected to the positive side terminals of the rectifying elements 14 and 15, Load fluctuation is suppressed.

[0025] In this operation, for example, the rated load current of the power supply device flows through the load of the output voltage Vol between the output terminals 22 and 23, and the load current flows through the output voltage Vo2 between the output terminals 21 and 22. Think about when not. When switching element 3 is turned off and a flyback voltage is generated on secondary winding Sl, S2 of transformer 2, rectified current flows between output terminals 22 and 23, and point A in Fig. 2 is a leakage inductance component from point B 9 , 10 composite value Le 〖The voltage Ve is reduced. As a result, current II flows through capacitor 12 as shown in Fig. 2 to increase the voltage at point A and suppress the increase in voltage at point B, as shown in Fig. 3. Reduces load fluctuations compared to the configuration.

[0026] According to the multi-output power supply device of this embodiment, by connecting the positive side terminals of the rectifying elements 14, 15 via the capacitor 12, the load fluctuation of the power supply device is reduced, and the dummy resistor Can reduce power loss and increase power supply efficiency. In addition, it is possible to provide an efficient power supply device that suppresses the increase in cost because it is not necessary to form a transformer with a multilayer substrate in order to reduce the leakage component. Furthermore, dummy resistance can be reduced, which contributes to downsizing of the power supply device.

Next, a multi-output switching power supply device according to a second embodiment of the present invention will be described with reference to FIGS. Here, the same members as those in the above embodiment are denoted by the same reference numerals and the description thereof is omitted. The multiple output switching power supply of this embodiment is for a forward type multiple output switching power supply. In this multi-output switching power supply, the terminal with the secondary windings Sl and S2 is connected to the positive terminal which is the anode of the rectifying elements 14 and 15 such as the rectifying diode. The negative terminal, which is the cathode of one of the rectifying elements 14, is connected to one terminal of the cooperative choke coil 13 connected in series, and the other terminal of the cooperative choke coil 13 is connected to the output terminal 21. When Both are connected to one end of one smoothing capacitor 6. The other end of the smoothing capacitor 6 is connected to the terminal of the secondary winding S2 where no dot is present, and is connected to the output terminal 22.

[0028] The negative side terminal of the other rectifying element 15 is connected to one terminal of the cooperative choke coil 17 connected in series, and the other terminal of the cooperative choke coil 17 is connected to the output terminal 22. And is connected to one end of the other smoothing capacitor 7. The other end of the smoothing capacitor 7 is connected to the terminal of the secondary winding S1 where no dot is present, and is connected to the output terminal 23. Further, the cooperative choke coils 13 and 17 share the magnetic core 16.

[0029] A return element 18 such as a return diode is connected between the negative terminal of the rectifier element 14 and the terminal on the secondary winding S2 where no dot is present. In the reflux element 18, the positive terminal that is the anode is connected to the other terminal of the secondary winding S2, and the negative terminal that is the force sword is connected to the negative terminal of the rectifying element 14. ing. Further, a freewheeling diode 19 is connected between the negative terminal of the rectifying element 15 and the terminal of the secondary winding S1 that has no dot. The freewheeling diode 19 has an anode with a positive terminal connected to the terminal without the dot of the secondary winding S1, and a negative terminal with a force sword connected to the negative terminal of the rectifying element 15. Yes. In addition, capacitors 12 are provided between the negative terminals of the rectifying elements 14 and 15 and the secondary winding SI and S2 terminals of the cooperative choke coils 13 and 17, respectively! /

[0030] The forward type multi-output power supply circuit of this embodiment also has a parasitic inductance due to a leakage inductance between the transformer 2 and the rectifying elements 14 and 15 as in the equivalent circuit shown in FIG. This is a circuit in which leakage inductance components 9 and 10 are inserted in series. Therefore, when a load current is applied to only one output or when an unbalance occurs in the load, the voltage drop generated by leakage inductance components 9 and 10 such as leakage inductance increases on the output side where the load current flows. The voltage on the output side that causes current to flow to the load decreases, and if current is supplied to the load, the voltage on the output side increases or decreases, and the load fluctuation increases.

At this time, in this embodiment, the voltage drop caused by the leakage inductance components 9 and 10 is alleviated to some extent by the cooperative choke coils 13 and 17 sharing the magnetic core 16, but the effect is not sufficient. Condensers connected to the positive terminals of rectifier elements 14, 15 The voltage between the outputs is corrected by the sensor 12, and the load fluctuation is suppressed more effectively.

[0032] In this operation, for example, the rated load current of the power supply device flows through the load of the output voltage Vol between the output terminals 22 and 23, and the load current flows through the output voltage Vo2 between the output terminals 21 and 22. Otherwise, the rectified current flows between the output terminals 22 and 23 due to the voltage generated on the secondary windings Sl and S2 of the transformer 2, and the point A in Fig. 5 is the combined value of the leakage inductance components 9 and 10 from the point B Voltage due to Le is reduced by Ve. As a result, as shown in FIG. 5 through the capacitor 12, the current 13 flows through the capacitor 12, the voltage at the point A is increased, the voltage at the point B is suppressed from increasing, and the load fluctuation is reduced.

[0033] According to the multi-output power supply device of this embodiment, by connecting the capacitor 12 between the negative side terminals of the rectifying elements 14, 15, the load fluctuation of the power supply device is reduced, and the same as in the above embodiment. The effect of can be obtained.

Note that the multi-output switching power supply apparatus of the present invention is not limited to the above embodiment, and the number of multi-outputs can be set as appropriate, and the rectifying element is synchronized using various transistors in addition to the diode. A power supply circuit that can be rectified is also applicable to an appropriate circuit.

Claims

The scope of the claims

[1] A primary side circuit in which a primary winding of a transformer and a main switching element are connected in series to a DC power supply, a plurality of secondary windings are provided in the transformer, and the switching element is switched. Then, the flyback voltages generated in the plurality of secondary windings of the transformer are rectified by rectifying elements, the rectified outputs are connected in series, and the outputs are smoothed to supply an output voltage. The flyback type multi-output switching power supply device that controls the output voltage by feeding back the combined voltage of the plurality of output voltages,

A positive side terminal of each rectifying element is connected to each positive side terminal of a flyback voltage generated on each secondary winding of the transformer, and a capacitor is connected between each positive side terminal of each rectifying element. A multi-output switching power supply device characterized by being connected via

2. The multi-output switching power supply device according to claim 1, wherein the rectifying element is a diode, and the capacitor is connected to an anode terminal of each diode.

[3] The multiple output switching power supply device according to [1], wherein a transistor is used as the rectifying element for synchronous rectification.

[4] A primary side circuit in which a primary primary winding of a transformer and a main switching element are connected in series to a DC power supply, a plurality of secondary windings are provided in the transformer, and the switching element is switched. A plurality of rectifying elements that respectively rectify AC voltages generated in a plurality of secondary windings of the transformer, and one end connected to the dot side of the secondary winding and the other end connected to an output terminal. A plurality of recirculation elements connected between one end of the choke coil and the non-dotted side of the secondary winding, and a smoothing capacitor for smoothing each output. In the forward type multi-output switching power supply that controls the output voltage by feeding back the combined voltage of the voltage,

A multi-output switching power supply device comprising: a negative terminal of each rectifying element and a midpoint of each choke coil connected via a capacitor.

5. The multi-output switching power supply apparatus according to claim 4, wherein the rectifying element is a diode, and the capacitor is connected to a force sword terminal of each diode.

6. The multiple output cascade according to claim 4, wherein a synchronous rectification is performed using a transistor as the rectifying element. Switching power supply.

5. The multi-output switching power supply device according to claim 4, wherein each choke coil connected to each rectifying element shares a magnetic core with a plurality of choke coils.