JPH03139167A - Power supply - Google Patents

Abstract

PURPOSE:To perform optimal voltage conversion and efficient control by controlling a switching element, connected to the primary of a converter transformer, based on a signal synchronized with the flyback voltage of the converter transformer. CONSTITUTION:A converter transformer T1 is driven by a switching transistor Tr1, where the voltage induced in the secondary winding n2 is rectified and smoothed through a diode D2 and a capacitor C2 and fed to a load. Voltage induced in secondary winding n3 is fed through the diode D2 and a resistor R4 to (+) input terminal of a comparator Q1 while furthermore fed to (-) input terminal of the comparator Q1 after it is rectified and smoothed through a diode D4 and a capacitor C3. Consequently, a signal synchronized with the flyback voltage of the converter transformer T1, i.e., an output signal from the comparator Q1, is produced. A PWM circuit 1 controls the switching transistor Tr1 based on the synchronized signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply device used as a switching regulator in office equipment and the like.

[Conventional technology]

FIG. 7 is a circuit diagram showing the configuration of a power supply device having this type of conventional voltage resonance type converter transformer. In the same figure, T1 has one end of the primary winding n1 connected to a DC power supply (V C
C) in the converter transformer connected to -order winding n1
The other end is connected to a ground terminal via a switching transistor Tr. Further, a resonance capacitor C1 and a diode D1 are connected in parallel with the switching transistor TrI, and a PWM circuit 1 is connected to the base (gate) of the switching transistor T-.

On the secondary side of the converter transformer T1, there are two secondary windings n2. R3 is provided, and one secondary winding n2 serves as an output winding. A rectifying diode D2 and a smoothing capacitor C2 are connected to this secondary winding n2 to supply a stable DC output to the load. Further, a rectifying diode D3 is connected to the other secondary winding +11 n 3, and the base of an NPN transistor T12 connected to a +5V DC power supply is connected to the cathode side of this diode D3. R1゜R2
, R3 are resistances.

In the power supply device configured as a voltage resonance type switching regulator as described above, the converter transformer T is driven by turning on and off the switching transistor Tr1, and generates an alternating current voltage on the secondary side. The voltage developed across the secondary winding n2 is applied to the diode D2. After being rectified and smoothed by capacitor C2, it is supplied to the load as the output of the device. Further, the voltage generated in the secondary winding n3 is applied to the base of the NPN transistor T,2, and this NPN
The output (collector voltage) of PN transistor Tr2 is PW
The M circuit 1 is powered manually. The PWM circuit 1 controls the on/off states of the switching transistors T, . . . to supply a stable DC output to the load. That is, the flyback voltage generated in the converter transformer T is detected, the off time of the switching transistor Tr1 is determined based on the detection signal 3, and switching control is performed in synchronization with the flyback voltage.

Here, the optimal switching control is such that the next on-time begins when the flyback voltage generated at the collector of the switching transistors T, 1 becomes zero volts, but in reality, the switching transistors T,
1 collector voltage is difficult to detect. Therefore, as in the circuit shown in Fig. 7, the flyback voltage is detected from the secondary winding n3 other than the charging part of the converter transformer T, and is synchronized with the drop volt voltage of the output of the secondary winding n3. Switching control is performed using FIG. 8 shows the signal waveforms of each section a, b, and c of the circuit of FIG. 7 at that time.

[Problem to be solved by the invention]

As mentioned above, conventional power supplies control the switching transistor by detecting the flyback voltage from other windings, and when this winding reaches zero volts and the collector of the switching transistor reaches zero volts. Since the synchronization timing is different from when the switching transistor is turned on, the synchronization signal is turned on by the synchronization signal when the voltage remains in the collector of the switching transistor, which prevents optimal voltage conversion and prevents efficient control. The problem was that it was not possible to do so.

The present invention has been made with attention to such problems, and an object of the present invention is to provide a power supply device that can perform optimal voltage conversion and perform efficient control.

(Means for solving problems) The power supply device of the present invention is configured as follows.

(a) In a power supply device having a voltage resonance type converter transformer, the flyback voltage of the converter transformer is determined from the output of a detection winding that detects the flyback voltage of the converter transformer and the output obtained by rectifying and smoothing the output. A signal synchronized with is generated, and a switching element connected to the next side of the converter transformer is controlled based on this signal.

(b) In the power supply device of a above, the rectified and smoothed output of the detection winding of the converter transformer is used as a power source, and the switching element driven by the output of the detection winding is synchronized with the flyback voltage of the converter transformer. I tried to get the signal.

(C) In the above power supply device, a PW using the rectified and smoothed output of the detection winding of the converter transformer as a power source.
The M circuit controls the switching elements in synchronization with the flyback voltage of the converter transformer.

[Effect]

In the power supply device of the present invention, a synchronization signal is generated from the output of the detection winding that detects the flyback voltage of the converter transformer and the output obtained by rectifying and smoothing the output, and this synchronization signal allows optimal synchronization timing. The switching element on the primary side of the converter transformer is controlled by

〔Example〕

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, and the same reference numerals as in the conventional FIG. 7 indicate the same components. In the figure, T, is a converter transformer, T,1 is a switching transistor such as an FET, which is a switching element connected to its primary winding n3, and C,,D, is connected in parallel with the switching transistor T,,1. Capacitors and diodes, n2. n3 is converter transformer T,
In the secondary winding, the secondary winding n2 is the output winding, and the secondary winding n3 is the output winding.
is a detection winding that detects flyback voltage. D2. C2 is a rectifying diode and a smoothing capacitor connected to the secondary winding n2, D, D4 is a rectifying diode connected to the secondary winding n3, and C3 is a smoothing capacitor. 1 is a comparator that compares the output of the primary winding n3 with the output obtained by rectifying and smoothing this output, and the output side of this comparator Q1 is a switching transistor T.
It is connected to a PWM circuit that controls r1.

R4 to R8 are resistors.

Next, the operation of the circuit shown in FIG. 1 will be explained using the signal waveform diagram shown in FIG. FIG. 2 shows signal waveforms at each part of FIG. 1.

The converter transformer T is driven by a switching transistor T, and generates an alternating current voltage on the secondary side. The voltage generated in the secondary winding n2 of this converter transformer TI is applied to the diode D2. It is rectified and smoothed by capacitor C2, and is supplied to the load as a DC output. Further, the voltage generated in the secondary winding n is applied to the diode D2 and the resistor R.
The signal is inputted to one input terminal of the comparator Q through a resistor R, and after being rectified and smoothed by a diode D4 and a capacitor C3, it is inputted to one input terminal of the comparator Q through a resistor R. At this time, secondary winding +t%t03
The output of comparator Q1 and the output waveform are the second
The waveform will be as shown in the figure.

Here, a signal synchronized with the flyback voltage of the converter transformer T1, that is, an output signal of the comparator Q, is generated from the output of the secondary winding n3 and the output obtained by rectifying and smoothing the output. controls the switching transistor T,1 based on this synchronization signal. Specifically, the rising edge of the output signal of the comparator Q1 is synchronized with the rising edge of the on-time of the PWM control, whereby the switching transistor Tr1 is controlled at a frequency synchronized with the resonance of the converter transformer T. Therefore, optimal voltage conversion can be performed and efficient control can be performed.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention. In the figure, T, 3 is a PNP transistor provided as a switching element that uses the rectified and smoothed output of the secondary winding n3 of the converter transformer n3 as a power source and is driven by the output of the secondary winding n3. A signal synchronized with the flyback voltage of the converter transformer T is obtained from the output of the transistor Tr3 and is input to the PWM circuit 1. Tr4
is an NPN transistor, and R9 to R,2 are resistors.

In the circuit shown in FIG. 3, the voltage generated in the secondary winding n3 of the converter transformer T1 is rectified and smoothed by a diode D4 and a capacitor C3, and then is rectified and smoothed by a diode D4 and a capacitor C3.
The power is applied to the emitter of the transistor T13 as a power source, and also to the base of the transistor T13 via the diode D3 and the resistor RI0.

At this time, the voltage waveforms of the emitter and base of the transistor Tr3 and the waveform of the synchronization signal input to the PWM circuit 1 are as shown in FIG. That is, similar to the circuit of the embodiment shown in FIG. 1 described above, it is possible to optimally control the switching transistor Trl and perform optimal voltage conversion.

Here, since the circuit of FIG. 3 does not use a comparator, a signal synchronized with the flyback voltage can be obtained without requiring a stable power source for driving the comparator. For this reason, the primary winding n of the converter transformer T1,
It is also possible to configure a primary control type switching power supply device in which the secondary winding n3 is the primary side and is insulated from the secondary winding n2.

FIG. 5 is a circuit diagram showing a third embodiment of the present invention. This embodiment is configured as a flyback voltage resonance type switching power supply device using the above-mentioned primary control method. In the figure, n4 is a detection winding for detecting the flyback voltage of the converter transformer T, which is provided on the primary side of the converter transformer T, and is connected to a rectifying diode D5 and a smoothing capacitor C4. There is. 2
The output after rectification and smoothing of this detection winding n4 is connected to the power supply (
This PWM circuit consists of fc (VCC).
The circuit 2 controls the switching transistors T, , l in synchronization with the flyback voltage. Further, the output of the detection winding n4 is connected to the diode D6. PW via PNP transistor Trs and NPN transistor Tr6
It is designed to be input to the timing (TIMING) terminal of M circuit 2. n5 is converter transformer T,
This secondary winding is provided as an output winding together with the secondary winding n2, so that two systems of DC outputs A and B can be obtained. Dy, Cs are the rectifying diodes and smoothing capacitors R, , R, 4 are resistors that divide the DC output after rectification and smoothing of the secondary winding n5, which are connected to the secondary @anS. The voltage detected is input to the voltage detection circuit 3, and the voltage detection signal is sent to the PWM circuit 2 via the photocoupler 4.
is man-powered. 5 is an AC power supply, 6 is a diode stack that converts the AC into DC and supplies it to the primary side of the converter transformer T, C6 is a smoothing capacitor, R15 ~
RI7 is a resistor.

In the above circuit, the PWM circuit 2 composed of an IC determines the on-time of the PWM signal output to the switching transistor Tri based on the synchronization signal input from the timing terminal. And converter transformer T1
The voltage developed across the secondary 5in2°05 of the diodes D2. D, and rectified by capacitors C2 and C5.

After smoothing, it is supplied to each load. At this time, the DC output voltage from the secondary winding n, , is the resistance R,3, R,4
The voltage is divided by and input to the voltage detection circuit 3. The detection signal of this voltage detection circuit 3 is transmitted to P
The WM circuit 2 is manually inputted from the F/Bi device, and the PWM circuit 2 controls the converter transformer T so that the output is constant based on the input detection signal. Furthermore, the detection winding n4 of the converter transformer T1 is connected to a diode D5.
The signal is rectified and smoothed by a capacitor C4, and is supplied as a power source to the PWM circuit 2, and is also rectified by a diode D6 and supplied to the base of a PNP transistor Tr5. The collector of the PNP transistor Tr5 is N
It is connected to the bases of PN transistors T, , 8, and the collectors of these transistors T, , 6 are connected to the power supply terminal of the PWM circuit 2 via a resistor RIB, and also to the timing terminal. With this configuration, a signal for timing synchronization with the power supply of the control circuit including the PWM circuit 2 can be obtained with one winding n4, and there is no need to add a new winding to the converter transformer T1. Therefore, it is possible to reduce costs. 6th
The figure is a signal waveform diagram of each part in FIG. 5, and this embodiment also provides the same effects as each of the embodiments described above.

〔Effect of the invention〕

As explained above, according to the present invention, a synchronization signal is generated from the output of the detection winding that detects the flyback voltage of the converter transformer and the output obtained by rectifying and smoothing the output, and based on this synchronization signal. of the converter transformer.
Since the switching element on the next side is controlled, optimum voltage conversion can be performed and efficient control can be performed. In addition, by using the output after adjusting and smoothing the detection winding as a power source and obtaining a synchronization signal from the switching element driven by the winding, switching control can be performed without requiring a comparator and its driving power source. Furthermore, by controlling the switching element on the primary side of the converter transformer with a PWM circuit using the rectified and smoothed output of the detection winding as a power source, a new winding can be added to obtain the synchronization signal. There is no need to provide one, and primary control becomes easy.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of the first embodiment of the present invention;
The figure is a signal waveform diagram of each part of Fig. 1, and Fig. 3 is a signal waveform diagram of each part of the present invention.
A circuit diagram showing the configuration of the embodiment, FIG. 4 is a signal waveform diagram of each part in FIG. 3, FIG. 5 is a circuit diagram showing the configuration of the third embodiment of the present invention, and FIG. 6 is a diagram of each part in FIG. 7 is a circuit diagram showing the configuration of a conventional power supply device, and FIG. 8 is a signal waveform diagram of each part of FIG. 7. 1.2-...-P W M circuit 3... Voltage detection circuit C2-C6... Smoothing capacitor D2-D
7------- Diode n for rectification, ＊＊＊＊＊＊-
Secondary winding n 2 + n ll+...-Secondary winding (output winding) 1'l 3**a-osSecondary winding (detection winding) Fig. Each node 6 in Fig. 1 )Spring Ichipi type Fig. 2 n″4...Detection winding...Comparator...Converter transformer

Claims (3)

[Claims] (1) In a power supply device having a voltage resonance type converter transformer, the flyback voltage of the converter transformer is determined from the output of a detection winding that detects the flyback voltage of the converter transformer and the output obtained by rectifying and smoothing the output. 1. A power supply device that generates a signal synchronized with and controls a switching element connected to the primary side of a converter transformer based on this signal. (2) Using the rectified and smoothed output of the detection winding of the converter transformer as a power source, and obtaining a signal synchronized with the flyback voltage of the converter transformer from a switching element driven by the output of the detection winding. The power supply device according to claim 1, characterized in that: (3) The switching element according to claim 2, characterized in that the switching element is controlled in synchronization with the flyback voltage of the converter transformer by a PWM circuit using the rectified and smoothed output of the detection winding of the converter transformer as a power source. power supply.