JPH0315269A - Starting circuit for multi-output switching power supply - Google Patents

Abstract

PURPOSE:To reduce power loss by starting control circuits at second and following stages with voltage induced in the auxiliary winding of prestage transformer. CONSTITUTION:A multi-output switching power supply comprises a DC input power source PDC, transformers T1-T2, switching transistors Q1-2, control circuits 1-2, rectifying/smoothing circuit RC and the like. Starting resistor R2 in the control circuit 2 for second DC/DC converter is connected with point Va of DC voltage source in which voltage produced in the auxiliary winding P2 of first DC/DC converter is rectified/smoothed through a diode D1 and a capacitor C1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a startup circuit for a multi-output switching power supply device in which a plurality of DC/DC converters are coupled in parallel to a DC input power supply. (Prior art) The conventional device of this type of multi-output switching power supply device is
It is shown in the figure. In Fig. 3, the AC voltage of commercial AC tiAc is rectified by a diode bridge rectifier circuit DB and smoothed by a smoothing capacitor CO to form a DC input power apoc, and the primary winding of a transformer T1 is connected in series to this DC input power supply PDC. Line P
1 and switching transistor Q1 are connected.
A rectifier/smoothing circuit RS consisting of diodes D3, D4, D5, D6, inductance elements 1, L2, and capacitors C2, C3 is connected to the secondary windings Sl, 52 of the transformer Tl, respectively. A series stabilized power supply circuit 3 is connected to the Sl side. Transformer T1
A control circuit 1 is connected to the auxiliary winding P2, which is supplied with an auxiliary power supply voltage rectified and smoothed by a diode DI and a capacitor CI. The switching transistor Ql is turned on and off so that the output voltage v1 on the line s2 side is constant.
Control off. The DC input ti1lPoc has a second DC/DC converter connected in parallel to the first DC/DC converter.
A DC converter is connected. This second DC/
The DC converter includes a transformer T2, a switching transistor Q2 connected to the transformer T2 in series with a primary winding P3, and a diode D7 . D8, capacitor C4. C
5, a control circuit 2 connected to the auxiliary winding P4 of the transformer T2, and a starting resistor R2 of the control circuit 2. 4 is a series stabilized power supply circuit. The first DC/DC converter is a forward type,
The second DC/DC converter is configured as a flyback type.

In Fig. 3, when the switch S is turned on, the starting resistor R1
The control circuit 1 is activated via the switch 1, and the switching transistor Q1 starts its switching operation. A pulse-like voltage is induced on the secondary side of the transformer T1 by turning on and off the switching transistor Ql, and a DC output voltage Vl is obtained by the rectifier/smoothing circuit RS. Commercial AC electricity! The switching transistor Q is controlled by the control circuit 1 so that the DC output voltage v1 remains constant even if the AC input voltage Vin and the load current ■1 on the DC output side fluctuate.
The on/off ratio of l is controlled. The series stabilized power supply circuit 3 of the secondary winding S1 has a voltage v2 between the terminals of the capacitor C2.
This circuit is designed to obtain a stable output voltage without causing the DC output voltage v2 to change depending on the DC output voltage v1, since this changes depending on the DC output voltage v1. When the switch S is turned on, a starting signal is input to the control circuit 2 of the second DC/DC converter via the starting resistor R2, so that the switching transistor Q2 starts a switching operation, and the first DC/DC converter and Similarly, stabilized DC output voltages V3 and V4 are obtained. [Problems to be Solved by the Invention] A load to which a DC output voltage is supplied by the multi-output switching power supply device described above is often required to be sequentially supplied with output voltages v1 to v4. However, in the conventional device described above, when the switch S is turned on, the switching transistors Ql and Q2 of the first and second IC converters start switching operations almost simultaneously, so the DC output voltage Vl-V4 also rises almost simultaneously. Go up. Therefore, there is a drawback that a circuit must be added to the load side to sequentially supply the DC output voltages v1 to v4. Also, starting resistance Ill,R
2 is connected to a high-potential DC input power source, which has the disadvantage of large losses and reduced efficiency of the switching i power supply. Therefore, the purpose of the present invention is to eliminate the drawbacks of the conventional device described above, and to start a multi-output switching II power supply device that can set the starting order of a plurality of C/DC converters and has less power loss due to starting resistance.・The purpose is to provide circuits. [Means for Solving the Problem] In order to achieve the above-mentioned object, the present invention includes a primary winding and a switching transistor of a transformer connected in series to a DC input power source, and a secondary output of the transformer. a rectifier/smoothing circuit that rectifies/smoothes the current, and a switching transistor connected to the auxiliary winding of the transformer and activated via a starting resistor so that the output of the rectifier/smoothing circuit becomes constant. DC consisting of a control circuit for off control
/ In a multi-output switching power supply device comprising a DC converter and a plurality of DC/DC converters connected in parallel to the DC input power supply,
/ The control circuit of the DC converter is the previous stage DC / DC
The converter is characterized in that it is started via a starting resistor by the voltage generated in the auxiliary winding of the converter's transformer. [Function] In the multi-output switching power supply device according to the present invention,
The control circuits of the DC/DC converters in the second and subsequent stages are started by the voltage generated in the auxiliary winding of the transformer of the preceding stage DC/DC converter via the starting resistor, so the preceding stage DC/DC converter is started. Later in the latter part [
The IC/DC converter is activated, and the activation order of multiple DC/DC converters connected in parallel to the DC input power source can be determined. [Example] Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, the same components as those in the conventional device shown in FIG.

The difference in FIG. 1 from the conventional example shown in FIG. 3 is that the starting resistor R2 of the control circuit 2 of the second DC/DC converter is
is connected to point Va of the DC voltage source, which is the voltage generated in the auxiliary winding P2 of the first DC/DC converter, rectified and smoothed by the diode D1 and capacitor C1. In addition, the secondary winding S of the first DC/DC converter
A resistor RIO, a Zener diode ZD10, and a photocoupler P are connected between the DC output voltage terminals of the rectifier/smoothing circuit RS on the second side.
A series circuit with the light emitting diode of the CIO is connected, and a transistor TI controlled by the phototransistor of the photocoupler PCIO is provided in the series stabilized power supply circuit 3 on the side of the secondary winding Sl, and the transistor TI is connected to the light emitting diode of the second DC/DC converter. Resistor Rll between the DC output voltage terminals of the 34 secondary windings
and Zener diode ZDII and photocoupler PCII
A series circuit with a light emitting diode is connected, and a secondary winding S
Photocoupler PCI in series stabilized power supply circuit 4 on side 3
A transistor T2 is provided which is controlled by the phototransistor of I. Now, when the switch S is turned on at time point 10 shown in FIG. A DC output voltage v1 that has been rectified and smoothed by the rectification and smoothing circuit RS is output. When this DC output voltage v1 reaches the Zener voltage Za of the Zener diode zD10, the photocoupler PCIO is turned on and the series stabilized power supply circuit 3 starts operating, so that the DC output voltage v2 on the side of the secondary winding Sl becomes DC. It rises after the output voltage v1 rises. 1st DC/D
The switching transistor Ql of the C converter performs a switching operation to generate a DC output voltage V1. After V2 rises, the pulse-like voltage generated in the auxiliary winding P2 of the transformer T1 is rectified by the diode D1 and transferred to the capacitor C.
Smoothed by 1. The auxiliary voltage generated in the auxiliary winding P2 supplies a starting signal to the control circuit 2 via the starting resistor R2, and the switching transistor Q2 starts the switching operation. As a result, the second DC/DC converter sequentially outputs DC output voltages V3 and V4.

Here, the power loss due to the starting resistor R2 is the auxiliary winding P2
Assuming that the DC voltage generated in the conventional device is IOV, when the input voltage of the commercial AC power supply AC is 100 V, the DC input voltage (PDC) is approximately 140 V, so the power loss due to the starting resistor R2 in the conventional device can be reduced to approximately 1/10.

〔Effect of the invention〕

As explained above, according to the present invention, the primary winding of the transformer and the switching transistor connected in series to the DC input power source, and the rectifying/smoothing transistor for rectifying/smoothing the secondary output of the transformer. and a control circuit that is connected to the auxiliary winding of the transformer and is started via a starting resistor to control on/off the switching transistor so that the output of the rectifier/smoothing circuit is constant. A DC converter is provided, and a plurality of D
In a multi-output switching 1t section device in which C/DC converters are combined, the control circuit of the second and subsequent stage DC/DC converters has a starting resistance determined by the voltage generated in the auxiliary winding of the transformer of the preceding stage DC/DC converter. By configuring the DC/DC converter in the multi-output switching power supply I to be started, the order in which the DC output voltage rises can be determined. This has the advantage that the efficiency of a multi-output switching power supply can be improved because loss can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a multi-output switching power supply device showing an embodiment of the present invention, and FIG. 2 is a waveform diagram of the main parts of FIG. 1.
Figure 3 is a circuit diagram of a conventional multi-output switching power supply. PDC: DC input power supply, TI, T2: Transformer, Q1
．． Q2: Switching transistor, Rl rectifier and smoothing circuit, R1. R2 + starting resistance, P1. P2: [auxiliary winding, 1
．． 2: No.■? ■■ Figure 2

Claims (1)

[Claims] 1) A primary winding and a switching transistor of a transformer connected in series to a DC input power source, a rectifier/smoothing circuit for rectifying/smoothing the secondary output of the transformer, and an auxiliary winding of the transformer. and a control circuit that controls the switching transistor on and off so that the output of the rectifier/smoothing circuit is constant, and is started via a starting resistor, and a plurality of DC/DC converters are connected in parallel to the DC input power source. In a multi-output switching power supply device in which two DC/DC converters are combined, the DC/DC converters in the second and subsequent stages are
1. A starting circuit for a multi-output switching power supply, characterized in that a control circuit for a DC converter is started via a starting resistor by a voltage generated in an auxiliary winding of a transformer of a preceding DC/DC converter.