JP2003009526A - Switching power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce spike currents at the time the switching transistor is ON, the loss at ON, the noise and terminal voltage, and the loss in the switching transistor, i.e., the temperature rise, in an RCC system of switching power unit which is used for light-power load such as a washing machine, a dish washer, etc., where the power of electronic circuit load is small. SOLUTION: A resistor 8 and a capacitor 7 for high speed switching connected in series to this resistor 8 are connected between the primary winding 1b of the switching transistor 1 and the base of the switching transistor 3, a capacitor 9 is connected between the base of the switching transistor 3 and the reference voltage of the control winding 1b of the switching transformer 1, and a snubber circuit by the series connection consisting of a resistor 11 and a capacitor 10 is connected to the collector of the switching transformer 1.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RCC type switching power supply used in a washing machine, a dishwasher and other small power loads having a small electric circuit load. is there. 2. Description of the Related Art Conventionally, an RCC type switching power supply has been configured as shown in FIG. Hereinafter, the configuration will be described. As shown in FIG. 2, the switching transformer 1 includes a main winding 1a, a control winding 1b, and a secondary winding 1c. The polarity of the winding of the switching transformer 1 is the polarity of the RCC switching power supply, the main winding 1a and the control winding 1b operate in the same phase, and the main winding 1a and the secondary winding 1c operate in the opposite phases. I do. [0004] The capacitor 2 is the main DC power supply of the switching power supply. The switching transistor 3 has a resistor 4 connected to the emitter, and connects the base and the emitter of the transistor in parallel with the resistor 4. When the current flowing through the resistor 4 rises to the base-emitter ON voltage of the transistor 5, the transistor 5 is turned on. . The diode 6 is connected between the switching transistor 3 and the control winding 1b of the switching transformer 1. When the control winding voltage increases, a bias current is supplied to the switching transistor 3 through the diode 6. The capacitor 7 is connected in parallel with the diode 6 to speed up switching. [0006] The resistor 8 is connected in series with the diode 6,
This limits the bias current to the switching transistor 3. One end of the collector and the emitter of the transistor 5 is connected to a connection point between the resistor 8 and the base of the switching transistor 3, and the other end is connected to a connection point between the reference potential side of the control winding 1 b and the resistance 4. The capacitor 10 and the resistor 11 are connected in series to form a snubber circuit (hereinafter referred to as a CR snubber circuit), and one end thereof is connected to a connection point between the collector of the switching transistor 3 and the main winding 1a of the switching transformer 1. The other end is connected to the high potential side of the capacitor 2. The photocoupler 12 is a phototransistor 1
2a and a photodiode 12b. The collector of the phototransistor 12a is connected to the cathode of the diode 6, and the emitter is connected to the base of the transistor 5. The diode 13 and the capacitor 14 are connected to the secondary winding of the switching transistor 1 to form a secondary rectifier circuit. The constant voltage diode 15 is connected in series with the photodiode 12b, and is connected in parallel with the capacitor 14. The resistor 16 is connected to the high potential side of the capacitor 2 and the base of the switching transistor 3. The operation of the above configuration will be described. When a voltage is applied to the capacitor 2, the switching transistor 3 is turned on by the starting resistor 16. When the switching transistor 3 is turned on, a voltage is generated in the main winding 1a of the switching transistor 1, and a voltage is also generated in the control winding b.
Is biased and the current further increases. When this current flows through the emitter resistor 4 and the voltage reaches the base-emitter on-voltage of the transistor 5, the transistor 5 is turned on to draw in the base bias current of the switching transistor 3, and the switching transistor 3 is turned off. Become. When the switching transistor 3 is turned off, a voltage is generated in the secondary winding 1c of the switching transformer 1, and a secondary DC voltage is generated by the rectifier circuit of the diode 13 and the capacitor 14. This state repeats,
When the secondary output voltage reaches the sum of the operating voltage of the constant voltage diode 15 and the ON voltage of the photodiode 12b, the photocoupler starts operating, and thereby starts operating to stabilize the secondary output voltage. That is, when the secondary voltage is about to rise, a current flows through the photodiode 12b, thereby activating the phototransistor 12a, supplying a bias current to the base of the transistor 5, and thereby the transistor 5a.
Is turned on and the feedback operation of turning off the switching transistor 3 is performed. The above is the operation of the RCC switching power supply. However, in such a conventional configuration, when the switching transistor 3 is turned on, a spike-shaped current flows due to the electric charge accumulated in the CR snubber circuit, and becomes a noise source. , And a source of loss. SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. The spike current when the switching transistor is turned on is reduced, the loss at the time of turning on is reduced, the noise terminal voltage is reduced, and the loss of the switching transistor, that is, the temperature rise is reduced. The aim is to reduce it. According to the present invention, in order to achieve the above object, there is provided a resistor between a control winding of a switching transformer and a base of a switching transistor, and a switching high speed connected in series with the resistor. A capacitor between the base of the switching transistor and the reference potential of the control winding of the switching transformer, and a snubber circuit with a series connection of a resistor and a capacitor connected to the collector of the switching transformer. It is. Thus, the spike current when the switching transistor is turned on can be reduced, and the loss at the time of turning on can be reduced, the noise terminal voltage can be reduced, and the loss of the switching transistor, that is, the temperature rise can be reduced. The invention according to claim 1 of the present invention is directed to a resistor connected between a control winding of a switching transformer and a base of a switching transistor and a switching high speed connected in series with the resistor. A switching capacitor, a capacitor connected between a base of the switching transistor and a reference potential of a control winding of a switching transformer, and a snubber circuit formed by a resistor and a capacitor connected in series to a collector of the switching transformer. By shifting the ON timing of the base of the switching transistor, the energy of the snubber circuit consisting of a resistor and a capacitor and the resonance of the snubber circuit due to resonance with the inductance of a switching transformer and other patterns is consumed, and the collector voltage is reduced. By turning on when the constant value decreases, spike current can be reduced, and noise generation and transistor loss can be reduced. An embodiment of the present invention will be described below with reference to the drawings. Components having the same configuration as the conventional example are denoted by the same reference numerals, and description thereof is omitted. As shown in FIG. 1, one end of the capacitor 9 is connected to the connection point between the resistor 8 and the base of the switching transistor 3, and the other end is connected to the reference potential side of the control winding 1b and the connection point of the resistor 4. are doing. The collector and the emitter of the transistor 5 are connected in parallel with the capacitor 9. Other configurations are the same as the conventional example. The operation of the above configuration will be described. In addition,
The basic operation of the switching power supply of the RCC system is the same as that of the conventional example, and the description is omitted. The capacitor 7 is connected in parallel with the diode 6 to the base bias circuit of the switching transistor 3 and gives a steep change to the base bias voltage, thereby increasing the speed and increasing the switching speed. It is. On the other hand, the capacitor 9 forms a time constant circuit in combination with the resistor 8.
This causes a time delay and a dull voltage change. Here, the operation when the switching transistor 3 is switched on and off will be described. At the time of switching off, the loss can be reduced by delaying the rise of the collector voltage by the snubber circuit by connecting the resistor 11 and the capacitor 10 in series. At the time of switching on, the capacitor 7 causes the cathode voltage of the diode 6 to rise sharply simultaneously with the generation of the voltage of the control winding 1b. The steeply rising voltage is time-delayed by the resistor 8 and the capacitor 9 to slow down the voltage rising speed. The slowing down of the voltage rise slows down the switching speed and increases the switching-on loss. However, since the switching time is delayed, the collector voltage at the time of switching on is reduced, and while the on-timing is delayed, energy loss occurs due to resonance between the snubber circuit and the main winding 1a and other inductances. By turning on when the collector voltage drops by a certain value, the resistance 8
Although the switching speed at the time of ON is slowed down by the capacitor 9 and the capacitor 9, the loss of the switching transistor 3 can be reduced by the reduction of the spike current and the voltage current as compared with the operation when the capacitor 3 is not provided. As described above, according to the first aspect of the present invention, the resistor connected between the control winding of the switching transformer and the base of the switching transistor and the resistor connected in series with the resistor. A connected capacitor for speeding up the switching, a capacitor connected between the base of the switching transistor and a reference potential of a control winding of the switching transformer, and a series connection of a resistor and a capacitor connected to the collector of the switching transformer. Since the snubber circuit is provided, by shifting the ON timing of the base of the switching transistor, the snubber circuit consisting of a resistor and a capacitor and the energy of the snubber circuit due to resonance with the inductance of the switching transformer and other patterns are consumed, and the collector current By turning on when the pressure drops by a certain value, the switching speed at the time of switching on decreases, but by delaying the on timing, it is possible to turn on after waiting for energy release of the snubber circuit during this period and a decrease in the collector voltage, The spike current can be reduced, the loss when the switching transistor is turned on can be reduced, and the noise terminal voltage and the temperature rise of the switching transistor can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a switching power supply according to an embodiment of the present invention. FIG. 2 is a circuit diagram of a conventional switching power supply. [Description of References] 1 Switching transformer 1b Control winding 3 Switching Transistor 7 Capacitor 8 Resistor 9 Capacitor 10 Capacitor 11 Resistance

Claims (1)

Claims: 1. A resistor connected between a control winding of a switching transformer and a base of a switching transistor, a capacitor connected in series with the resistor for high-speed switching, and a capacitor connected to the switching transistor. An RCC switching power supply device comprising: a capacitor connected between a base and a reference potential of a control winding of a switching transformer; and a snubber circuit formed by connecting a resistor and a capacitor connected in series to a collector of the switching transformer.