JPH0326284U

JPH0326284U -

Info

Publication number: JPH0326284U
Application number: JP8830888U
Authority: JP
Priority date: 1988-07-01
Filing date: 1988-07-01
Publication date: 1991-03-18

Description

[Brief explanation of drawings]

第１図は、本考案によるＤＣ−ＤＣコンバータ
のリレーを用いた駆動回路の切り替えを行なう回
路図。第２図は、本考案によるフオトカプラーと
トランジスタを組合せた駆動回路の切り替えを行
なう回路図。第３図は、従来のＤＣ−ＤＣコンバ
ータの回路図である。１……直流入力電源、２……スイツチングトラ
ンジスタ、３ａ……リレーのコイル、３ｂ……リ
レーの接点、４ａ……フオトカプラーの発光素子
、４ｂ……フオトカプラーの受光素子、５……ト
ランス、５ａ……１次巻線、５ｂ……補助巻線、
５ｃ……２次巻線、６……ダイオード、１０……
コンデンサ、７，８……駆動用抵抗、９……制御
用トランジスタ、１１……出力電流検出回路、１
２……オンオフ用ＮＰＮトランジスタ、１３，１
７，１８，１９，２０……抵抗、１４ａ……フオ
トカプラーの発光ダイオード、１４ｂ……フオト
カプラーのフオトトランジスタ、１５……コンパ
レータ用ＩＣ、１６……出力電流検出用抵抗。 FIG. 1 is a circuit diagram for switching a drive circuit using a relay of a DC-DC converter according to the present invention. FIG. 2 is a circuit diagram for switching a drive circuit that combines a photocoupler and a transistor according to the present invention. FIG. 3 is a circuit diagram of a conventional DC-DC converter. 1...DC input power supply, 2...Switching transistor, 3a...Relay coil, 3b...Relay contact, 4a...Photocoupler light emitting element, 4b...Photocoupler light receiving element, 5...Transformer , 5a...primary winding, 5b...auxiliary winding,
5c... Secondary winding, 6... Diode, 10...
Capacitor, 7, 8... Drive resistor, 9... Control transistor, 11... Output current detection circuit, 1
2... NPN transistor for on/off, 13,1
7, 18, 19, 20...resistor, 14a...photocoupler light emitting diode, 14b...photocoupler phototransistor, 15...comparator IC, 16...output current detection resistor.

Claims

[Claims for Utility Model Registration] 1. Connecting the primary winding of a transformer and a transistor in series with a DC input power source, and controlling the transistor with a drive current obtained from an auxiliary winding of the transformer to generate self-oscillation. In a DC-DC converter, the flyback voltage obtained from the secondary winding of the transformer is rectified and filtered by a diode and a capacitor connected to the output side to obtain a DC output. A circuit that detects the output current is connected after the capacitor, and a resistor that controls the base drive current of the primary switching transistor is connected to a resistor that controls the base drive current of the primary switching transistor by the contact of the relay driven by the output current detection circuit. What is claimed is: 1. A drive circuit for a self-excited DC-DC converter, characterized in that it is configured to switch to a small value when the value of the load current is small, and to a large value when the value of the load current is small, and is characterized by having a resistance switching function for controlling the drive current. 2. A primary winding of a transformer and a transistor are connected in series with a DC input power source, and the transistor is controlled by a drive current obtained from an auxiliary winding of the transformer to produce self-oscillation, and the secondary winding of the transformer is In a DC-DC converter, the flyback voltage obtained from the line is rectified and filtered using a diode and capacitor connected to the output side to obtain a DC output.The output current is detected after the output diode and capacitor. The circuit operates a comparator with a light emitting diode of a photocoupler connected to the output side according to the value of the detected output current, and when the output current is large, the comparator output is turned off. Turn off the phototransistor of the coupler and
Connect the collector of the phototransistor to the base of the NPN transistor, which has a resistor connected to the collector side in parallel to the base drive resistor of the switching transistor connected to the next winding, and whose base potential is connected to a positive potential power supply via the resistor. A drive circuit for a DC-DC converter, characterized in that, when the phototransistor is turned off, the transistor inserted across the driving resistor is turned on.