JPS5976173A - Drive system for multioutput switching power source - Google Patents

Abstract

PURPOSE:To reduce the size of a multioutput switching power source and to enance the efficiency of the power source by driving a plurality of switching elements by frequencies of different integer ratio, thereby optimizing the switching frequency to the respective outputs and synchronously operating the elements. CONSTITUTION:Waveform shapers 3, 3' generate triangular waves in accordance with a frequency generated from an oscillator 2. The pulse phi1 for driving the first switching element is transmitted from the oscillator 2 to the shaper 3, and a comparator 5 produces an output by a triangular wave produced from the shaper 3. On the other hand, a pulse phi2 for driving the second switching element is generated from the shaper 3' by dividing the frequency from the oscillator 2 by a frequency divider 7. The frequencies of the pulses phi1, phi2 become integer ratio, thereby operating synchronously them by the different frequencies.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a multi-output switching power supply drive system, and in particular, when supplying multiple DC voltages to electronic equipment, each switching element is driven at a different frequency, thereby reducing the size and size of the power supply. , power supply drive method % formula % for high efficiency Conventionally, in multi-output power supply devices using the switching method, a single-output switching power supply was prepared for each voltage each night.
Multiple output voltages are obtained by combining a plurality of these or by transforming the output of a single switching element using a transformer. In particular, when a high-precision, compact, multi-output switching power supply is required, as shown in Figure 1, the number of switching elements Q, , Q, transformers T, , T, rectifier sections, and filter sections each equal to the number of outputs is required. In an O-line operation type (input direct rectification type) switching regulator in which each switching element Q□l Q is installed independently and controlled by a common control circuit 1, the switching regulator shown in Fig. 1 is used. Connect the input circuit to the front stage to absorb the noise superimposed on the input AC lightning voltage 1 voltage,
Energy is stored in large capacity electrolytic capacitor C0 through the aftermath rectifier.

In Figure 1, the voltage stored in capacitor C0 ■□
U is converted into a high frequency voltage by the switching elements Q, , , Q, and the high frequency transformer T,
, T, to supply energy to the output circuit (rectifying and smoothing circuit) to obtain each output voltage V, , V,. The control circuit 1 generates drive pulses φ1. φ.

This is to control the pulse width.

In general, the switching method is controlled by changing the duty cycle with a fixed pulse width (
There are two methods: a frequency control method) and a method of controlling by changing the pulse width at a fixed frequency (pulse width control method). Here, we will use the latter.

FIG. 2 is a block diagram of the conventional control circuit shown in FIG.

Conventionally, as shown in Figure 1 of the whistle, two switching elements Q
When driving □ and Q independently, synchronized operation is performed using the same frequency to prevent interference due to each driving frequency.

The control circuit usually includes an error amplifier, an oscillator, a modulation section, a logic gate circuit, and the like.

In the pulse width control method, the output voltage v1 or ■ is input to the error amplifier 4, and the DC signal from the error amplifier 1t@W4 is used as the oscillation output trigger of the oscillator 2 to generate the pulse φ0. Modulate φ.

In FIG. 2, one oscillator 2 is shared, and the pulse from the oscillator 2 is converted into a triangular wave by the waveform shaping circuit 3 and inputted to both comparators 5, and the signal from each scissor difference amplifier 4 is input to both comparators 5. 5, the width conversion outputs are taken out respectively, and the drive pulses φ1.
We have obtained φ.

In this case, drive path A・path φ0. Since φ is a synchronous operation with the same frequency using the oscillator 2, it is not possible to select a different optimum frequency depending on each output voltage. The disadvantage of the same frequency, synchronous operation is that due to the frequency limit of high-speed, high-voltage rectifier diodes, it is not possible to take full advantage of the characteristics that allow Schottky barrier diodes to operate at higher speeds.

In particular, in recent years, puff-MO as a high-speed switching element
8FET 17) Appearance, 200KH2゜500H
, switching power supplies have been put into practical use, and the problem is the switching speed of the rectifier.

A Schottky barrier diode can be used as a rectifier diode in a +5V circuit used in general logic circuits, and its switching frequency is 500KH.

Although it can be used up to around 100KH, in the case of a higher voltage circuit, for example, in the case of +12V or higher, the operating limit of this rectifier is about 100KH. For this reason, when performing synchronized operation at the same frequency with a multi-output switching power supply, it is necessary to drive at the lowest frequency limited by the slowest element, which is a major constraint on downsizing and increasing efficiency of the device. It has become.

[Purpose of the invention]

The purpose of the present invention is to eliminate such conventional drawbacks by setting the switching frequency for each output voltage to the optimum frequency and performing synchronized operation to provide a multi-output device that can be made smaller and more efficient. The object of the present invention is to provide a switching power supply drive system.

[Summary of the Invention V] The multi-output switching power supply drive system of the present invention is a multi-output switching system that stabilizes a plurality of switching elements by controlling each one independently by pulse width modulation in order to supply a plurality of DC voltages. The power supply is characterized in that the plurality of switching elements are driven at different frequencies, and the specific frequencies are set at an integer ratio.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 3.

When the present invention is applied to the control circuit l shown in FIG.
, D2 uses a Schottky barrier diode to make the output voltage 1 to 5, while Dll.

It is assumed that a high-speed diode with a PN junction lifetime killer is used for D, and the output voltage (2) is set to +24 (2).

The switching elements Q, , Q, are MOS FE
Using 'l', this switching element Q, , Qi, it.

Each drive pulse φ0. Drive by giving φ.

These driving pulses φ4. The control circuit that gives φ is
As shown in FIG. 3, a waveform shaping circuit 3' and a frequency dividing circuit 7 are newly provided to perform synchronized operation at different frequencies.

In FIG. 3, only one oscillator 2 is installed to generate the fundamental frequency of the multi-output switching power supply, which is shared by both switching elements Q and Q. For the frequency generated by the oscillator 2, the waveform shaping circuit 3.3' generates a triangular wave. Here, the pulse φ that drives the switching element Q1 to obtain the first output voltage ■□ is as follows:
The signal is directly transmitted from the oscillator 2 to the waveform shaping circuit 3, and generated by the comparator 5 using the triangular wave generated there. On the other hand, the pulse φ, which drives the switching element Q to obtain the second output voltage ■, is generated by dividing the frequency of the oscillator 2 into 1/! by the frequency divider 7. 1, and is thereby generated by the waveform shaping circuit 3'. As a result, the driving pulses φ1 and φ have respective frequencies in an integer ratio, allowing synchronous operation at different frequencies. That is, the first
The output voltage of
Occurs at a switching frequency of 00KH7, one second
The output voltage is +24 using a high-voltage high-speed diode.
Since the V current is generated by the switching frequency of 1QQKI+, synchronous transfer is possible.

FIG. 5 is a time chart of the pulse width conversion operation of the comparator in Figure 3.

The triangular wave shown in @5 diagram (R,) from the waveform shaping circuit 3,
The output voltage 1 voltage v0 from the error amplifier 4 is compared by the comparator 5, and the modulated output φ□ shown in FIG. 5(b) is obtained by width conversion. In addition, the triangular wave (not shown in FIG. 5(0)) from the waveform shaping circuit 3' and the output voltage V from the error amplifier 4' are compared by the comparator 5', and width conversion is performed as shown in ff15(d). Z change W, f output φ,? iI
Ru.

In FIG. 5, the frequencies of the modulated outputs φ and φ are an integer ratio of 3=2, but if this is set to 5:l, the embodiment of FIG. 3 is obtained.

FIG. 4 is a splitter diagram of a control circuit showing another embodiment of the present invention.

FIG. 4 shows an embodiment in which an oscillator is separately provided.

That is, a 500KH oscillator 2 and a 100K112 oscillator 2' generate pulses of each frequency and input them to the waveform shaping circuits 5 and 3', respectively.
J: Create a triangular wave shown in , and set the comparator 5.5'
Send to. Comparators 5 and 5' are shown in FIG. 5(b).
(,l) modulation output φ1. Outputs φ.

In this way, in the present invention, the Schottky barrier die'
Converters that can use − codes (+5V, etc.) are high frequency,
In addition, converters that cannot be used can be driven at low frequencies and operated synchronously to eliminate interference between circuits.

〔Effect of the invention〕

As explained above, according to the present invention, in a multi-purpose customizing Wt source, each output voltage has an IP!
By driving at an appropriate frequency and performing synchronous operation,
It is possible to realize an optimal power supply that matches the characteristics of the switching element, and it is possible to achieve smaller size and higher efficiency.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a multi-output switching power supply to which the present invention is applied, Fig. 2 is a block diagram of a conventional control circuit for synchronous operation, and Fig. 3 is an example of the present invention for different frequency/synchronous operation. FIG. 4 is a block diagram of the control circuit showing another embodiment of the present invention, and FIG. 5 is a time chart of the width conversion operation of the comparator in FIGS. 3 and 4. 18 control circuits, 2.2'! Oscillator, 3.3': Waveform shaping circuit, 4.4': Error multiplier 1.5.5'! Comparator, 6.6': Output amplifier, 7: Frequency divider circuit. Patent applicant Hitachi, Ltd. Representative Patent attorney Masatoshi Iso No. 1
Figure 2 Figure δ

Claims (1)

[Claims] In order to supply a plurality of DC voltages, a plurality of switching elements are independently controlled and stabilized by varying the pulse width. J!
A multi-output switching power supply driving method characterized by driving several switching elements at different frequencies and setting the respective frequencies to an integer ratio.