JPS5862714A - Multioutput switching power supply device - Google Patents

Abstract

PURPOSE:To generate a highly accurate constant voltage with a small sized device, by converting a high input voltage into a low output voltage at a switching circuit and driving the 2nd switching circuit converting the voltage into a low voltage of multioutput. CONSTITUTION:An AC input voltage AC is rectified D0 and smoothed C0, and applied to a switching TR and a pulse transformer 17 to obtain a high frequency voltage at secondary windings 11, 12. The output of the secondary windings is rectified D1, smoothed C1, amplified AMP1 and compared PWM1 with a triangle wave from an oscillator OSC1 to control the pulse width of the output of a transformer DT, allowing to keep an output voltage V1 constant. A voltage V2 with decreased regulation in interlocking with the voltage V1 drives a switching circuit consisting of a pulse transformer 18 and a switching TR19. The output of secondary wingings 13-16 of the pulse transformer 18 is rectified to apply voltages V3-V6 to each circuit, and the voltage V3 is amplified AMP2, the TR19 is controlled with an oscillator OSC2 and a comparator PWM2 to keep the voltage V3 constant. Thus, accurate constant voltage can be obtained with a small-sized device.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching power supply, and particularly to a power supply device suitable for supplying multiple output voltages to office equipment and the like.

Traditionally, power supplies for office equipment require multiple output voltages.
Among them, there are those that require high accuracy such as 5V and 12V, and those that require medium accuracy for supplying to loads such as motors and lamps.

FIG. 1 shows an example of a conventional multi-output switching power supply (an example of 6 outputs). The AC input voltage AC is a rectifier. It is converted into a rectified and smoothed DC voltage by a capacitor C8 and applied to a series circuit of a pulse transformer PT and a transistor TR. By switching the transistor TR at a high frequency, high frequency power is transmitted to the secondary side of the pulse transformer FT, and one of its outputs is rectified and smoothed by a diode D and a capacitor C1 to become a DC output voltage v1. The output voltage (1) is fed back through the amplifier AMP, and compared and amplified with the signal from the oscillator O8C (the pulse width adjuster PWM controls the switching pulse width of the transistor TR so that the output voltage (1) remains constant The other output voltages 2 to v6 are similarly obtained by rectifying and smoothing the high-frequency secondary voltage, but unlike the output voltage v1 above, they are outside the feedback loop, so the transformer P
A voltage drop occurs due to the impedance of the windings 10 to 16 of T and the impedances of diodes D1 to D6, etc., resulting in the desired output voltage. fluctuation rate accuracy cannot be obtained. Therefore, in the case of an output that requires high precision of about ±51, a single output power supply 1 with feedback as shown in Fig. 1 was provided for each output voltage type, but the configuration was large-scale and the feature of a switching power supply was small. It has disadvantages that make it undesirable. As another method, in FIG. 1, the output voltage V outside the feedback loop is
, ~v6 must be provided with voltage regulators REG2 to REG6 at the subsequent stage. The various drawbacks of the voltage regulator REG will be explained using Figures 2 to 4. ↑ Figure 2 shows a serial strobber power supply, but since the power that has been voltage adjusted by transistor 2 directly generates heat, it requires large heat dissipation. It requires a container, which makes downsizing difficult. FIG. 3 shows an example of a chopper type, and the output voltage V. Transistor 4 controls the frequency of square wave oscillator 3 and the output voltage V. The signal fed back is compared and amplified by the drive circuit 5, and the pulse width is used to switch the input voltage ■! After chopping the signal into a high-frequency intermittent wave, the signal is smoothed by a filter circuit including a choke 6 and a capacitor 7 to obtain a DC output voltage. Due to the switching operation, heat generation can be reduced, but the circuit scale is complex and miniaturization is difficult. Figure 4 shows an example using a mag amp.
In addition to the example shown in FIG. 3, since the number of circuits forming the mag-amp 8 increases, it becomes increasingly difficult to construct a multi-output power supply in a compact and low-cost manner.

Next, differences in the structure of the pulse transformer PT depending on the input voltage range will be explained. FIG. 5 typically shows an example of a pulse transformer structure when the input voltage is 150V or less. One thorn winding 10 is wound on the bobbin 9 to fill the bobbin width W9, and secondary windings 11 to 16 are similarly wound thereon to fill the bobbin width W9. However, when the input voltage is 150 V or more, the voltage is 1% [in power supplies used in Europe, the primary winding 10 and the secondary winding of the bobbin 9 are Since it is mandatory to provide a creepage distance W91 of 6 mm or more with respect to the primary winding, the width W10 of the primary winding is significantly narrower than the winding width W9 of the secondary winding. As a result, the primary windings 10 and 2
The magnetic coupling between the secondary windings 11 to 16 deteriorates, leading to a decrease in the accuracy of the fluctuation rate. Also, in the case of Fig. 5, if the secondary winding requires 6 outputs as in the example shown, the primary winding l
The secondary windings 16, 15, 14, etc. that are distant from O are 2
Since the magnetic coupling is obviously worse than that of the next winding 11, it has a major drawback in that it is difficult to keep the output voltage fluctuation rate within ±10-. Therefore, when using the transformer shown in Figure 6, in order to obtain a fluctuation rate of ±101, it is necessary to connect the voltage regulator REG to the secondary side, making it difficult to obtain a small and low-cost O multi-output power supply. It had some drawbacks.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-output switching power supply device that eliminates the drawbacks of the prior art described above and can obtain a highly accurate voltage fluctuation rate with a simple circuit configuration.

A feature of the present invention is that the power supply is divided into a switching power supply that converts a high input voltage to a low output voltage, and a second switching power supply that converts the low output voltage into a low voltage with multiple outputs. The purpose is to improve magnetic coupling and obtain higher precision in fluctuation rate.

An embodiment of the present invention will be described below with reference to FIG. 9th
In the figure, the alternating current input voltage AC is converted into a direct current voltage, and the switching transistor 'l'R and the pin lance 17 are connected.
Diode Do1 applied to capacitor C8, secondary windings 11 and 12 of transformer 17, amplifier AMPI forming the first feedback loop, oscillator 08CI
, a pulse width regulator PWMI, a drive transformer DTI, a second pulse transformer 18 to which low voltage v2 is applied, a switching transistor 19, and a secondary winding 1a of the transformer 18.
~16.A device consisting of an amplifier AMP2, an oscillator 08C2, and a pulse width adjuster PWM2 forming a second feedback loop.The operation in FIG.
When 0V is applied, a rectified and smoothed high DC zero voltage is applied to the series circuit of the primary winding 10 of the transformer 17 and the transistor TR. The high frequency power switched by the transistor TR according to the frequency of the oscillator 08CI is transmitted to the secondary windings 11 and 12, and the diodes D, , D
, and are rectified and smoothed by capacitors C, , C2 to obtain low DC voltages V, , V2. The output voltage ■1 passes through the amplifier AMPL, and the pulse width adjuster PWMI outputs a drive signal with a pulse width that makes the output voltage ■1 constant compared to the triangular wave from the oscillator 08C1 to the switching transistor TR via the transformer DT1. It operates to give a constant voltage. Since the fluctuation rate of the output voltage v1 is within the feedback loop, high accuracy within ±5% can be obtained.

As for the other output voltage (2), since the structure of the transformer 17 is only the secondary windings 11 and 12 in FIG. 6, the magnetic coupling is maintained well and a fluctuation rate of ±10 degrees can be easily realized.

Next, the second transformer 18 to which the low DC voltage ■2 is applied
The primary windings 103-106 are driven by a switching transistor 19 driven according to the frequency of the oscillator osc2, and a switching transistor 19 transmits high-frequency power to the secondary windings 13-16. Output voltage ■3
is made into a constant voltage in the second feedback loop by the same operation as described above, and a highly accurate fluctuation rate within ±5 inches is obtained.

Furthermore, the structure of the pulse transformer 18 is a sand inch winding in which the primary winding and the secondary winding are alternately wound as shown in FIG. 7 and a sand inch winding as shown in FIG. It is now possible to use a bifilar winding in which the primary and secondary windings are alternately arranged, as shown in Figure 2, which satisfies the dielectric strength characteristics without difficulty, and achieves ideally close magnetic coupling. It is possible to easily obtain a fluctuation rate accuracy of ±5 to ±10 inches.

FIG. 10 shows another embodiment of the structure of the second transformer 18. If the ratio between the primary side voltage v2 and the secondary side voltages ■3 to v6 is not large, the primary winding as shown in FIG. Line 101-1
By connecting 06 in parallel instead of in series, the high frequency resistance of the primary windings 101 to 106 can be reduced, making it possible to further improve the accuracy of the fluctuation rate of the output voltages 3 to v6. .

According to the present invention, a constant voltage feedback loop is formed by dividing the transformer into a first transformer with a high input voltage and a small number of secondary winding outputs and a second transformer with a low input voltage and a large number of secondary winding outputs. ±5 inches and ±1 with a simple configuration
Since multiple DC constant voltage outputs with a highly accurate variation rate of 0.01 can be obtained, the multi-output switching power supply device can be made smaller and lower in price.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional multi-output power supply, Figure 2 is a block diagram of a series power supply, Figure 3 is a block diagram of a chopper power supply, Figure 4 is a block diagram of a mag-amp power supply,
5 is a diagram of the winding structure of a conventional transformer, FIG. 6 is a diagram of the winding structure of another conventional transformer, FIG. 7 is a diagram of the structure of a transformer used in an embodiment of the present invention, and FIG. FIG. 9 is a diagram showing one embodiment of the power supply device according to the present invention, and FIG. 10 is a diagram showing the transformer structure of the third embodiment. 17... if pulse transformer, 18... second pulse 6 pulse transformer, PWM1... first pulse width regulator, PWM2... 20th pulse width regulator, 10,
101-106...Primary winding, 11-16...Secondary winding. Agent Patent Attorney Akio Takahashi Figure 1 Figure 2 Figure 30 Figure 4 Figure 50

Claims (1)

[Claims] 1. A first having one input winding and one or more output windings
a first voltage conversion device comprising a first switching circuit that turns on and off an input of the transformer; a second transformer having one input winding and two or more output windings; the transformer; A second voltage conversion device comprising a second switching circuit that turns on and off an input of the first voltage converter, and a circuit that feeds back one of the outputs to adjust the switching time of the second switching circuit. A multi-output switching power supply device characterized in that the output of the device is configured to be input to a second voltage conversion device. 2. Claim 1 is characterized in that a circuit is provided for feeding back one of the outputs of the output winding of the first transformer to adjust the switching time of the first switching circuit. Multi-output switching power supply.