JPH03101178U

JPH03101178U -

Info

Publication number: JPH03101178U
Application number: JP677590U
Authority: JP
Priority date: 1990-01-26
Filing date: 1990-01-26
Publication date: 1991-10-22

Description

[Brief explanation of drawings]

第１図は本考案の原理を説明するブロツク図、
第２図は本考案の一実施例を示すスイツチング電
源の保護回路の電気回路図、第３図はスイツチン
グ電源回路の基本電気回路図である。１……商用電源整流回路、２……直流定電圧回
路、３……第２制御手段、４……第１制御手段、
６，８，１８，１９，２０，２３，２４，２８，
２９，３２，３４，３８，３９，４０，４４，４
６，４９……抵抗器、７，３５，３６，４１，４
８……トランジスタ、９……変圧器、１０……１
次巻線、１１……ベース巻線、１２……２次巻線
、１３，２６，２７，３０，３７，４７……ダイ
オード、１４，２５，３１，３３，４５，５０…
…コンデンサ、２１，２２……コンパレータ、４
２……接続端子。 Figure 1 is a block diagram explaining the principle of the present invention.
FIG. 2 is an electrical circuit diagram of a protection circuit for a switching power supply showing an embodiment of the present invention, and FIG. 3 is a basic electrical circuit diagram of the switching power supply circuit. DESCRIPTION OF SYMBOLS 1... Commercial power supply rectifier circuit, 2... DC constant voltage circuit, 3... Second control means, 4... First control means,
6, 8, 18, 19, 20, 23, 24, 28,
29, 32, 34, 38, 39, 40, 44, 4
6, 49...Resistor, 7, 35, 36, 41, 4
8...Transistor, 9...Transformer, 10...1
Next winding, 11... Base winding, 12... Secondary winding, 13, 26, 27, 30, 37, 47... Diode, 14, 25, 31, 33, 45, 50...
...Capacitor, 21, 22...Comparator, 4
2... Connection terminal.

Claims

[Claims for Utility Model Registration] (1) A transformer having a primary winding, a secondary winding, and a base winding for positive feedback of switching operation, a collector of a switching transistor, and one end of the primary winding. The emitter of the transistor is connected to one end of the base winding, and a branch point is provided at the base of the transistor, and one end of the branch is connected to the other end of the base winding through the bias resistor of the transistor. between the other end of the primary winding and one end of the base winding. a commercial power rectifier circuit that supplies power;
A switching power supply circuit comprising a circuit that extracts an output from the secondary winding and supplies it to a load, the switching power supply circuit comprising a switching operation stop transistor, first control means and second control means for controlling the same transistor, and the commercial power supply rectifier. A DC constant voltage circuit is provided to stabilize the output of the circuit, and the collector of the switching operation stopping transistor is connected to the branch point of the base of the switching transistor, and the emitter of the switching operation stopping transistor and the base winding are connected. one end of the transistor, the first control means and the second control means are connected to the base of the transistor, and the DC constant voltage circuit is further connected to the first control means and the second control means. and supplying a driving DC voltage to the first control means and the second control means, and connecting the input circuit of the first control means and the connection point of the base winding and the bias resistor. The first control means detects a voltage outside a predetermined voltage range occurring in the base winding and brings the switching operation stop transistor into a conductive state to stop the operation of the switching transistor, and the second control means A switching power supply protection circuit, characterized in that the switching power supply circuit is configured to prevent the switching operation stop transistor from becoming conductive due to a transient phenomenon when power is applied to the switching power supply circuit. (2) The first control means includes an abnormal voltage detection circuit, a branch point is provided at the output end of the DC constant voltage circuit, and one of the branch points is divided by a first, second, and third resistor. 1 reference voltage and a second reference voltage are obtained and inputted to a first comparator circuit and a second comparator circuit, and the abnormal voltage detection circuit rectifies the voltage at the connection point between the base winding and the bias resistor as a detection input. A diode is connected and the output of the diode is input as a comparison signal to the first and second comparator circuits through a smoothing circuit, and when the comparison signal deviates from the first and second reference voltages, the comparator circuit 2. The switching power supply protection circuit according to claim 1, wherein a bias voltage is supplied to the base of the transistor for stopping the switching operation by outputting an output from the switching power source to make the transistor conductive. (3) The second control means includes a circuit including a first transistor and a second transistor, connects the emitter of the first transistor and a branch point of the output end of the DC constant voltage circuit, and loads the collector of the transistor. The base of the second transistor is connected to the base of the second transistor via a resistor, and the base is connected to the earth line via a bias resistor, and the collector of the second transistor is connected to the base of the switching operation stop transistor. The emitter of the second transistor is connected to the ground line, the branch point of the output end of the DC constant voltage circuit is connected to the base of the first transistor via a first resistor for biasing, and the base is biased. The first transistor is connected to one of the capacitors, the other of which is connected to the ground line through a second resistor, and the collector current is supplied to the first transistor using the charging current that flows through the capacitor when the power is turned on to the switching power supply circuit. 3. The switching power supply protection circuit according to claim 1, wherein the switching operation stopping transistor is prevented from becoming conductive by causing the second transistor to conduct. (4) Connecting the anode of a diode to the connection point between the second resistor and the capacitor, and connecting the cathode of the diode to the branch point of the output end of the DC constant voltage circuit to form a discharge circuit for the capacitor. and discharging the capacitor through the diode when the switching power supply circuit is powered off,
Claim (3) characterized in that when the power is turned on again, a charging current is passed through the capacitor to operate the circuit.
Switching power supply protection circuit as described.