| 摘要 |
PROBLEM TO BE SOLVED: To realize a deboosting noninsulated dc-dc conversion circuit which operates stably with low loss, even when a low voltage is inputted, with merely adding a small number of circuit components to the conventional circuit. SOLUTION: The dc-dc conversion circuit 1 of this invention is a deboosting noninsulated circuit which on/off-controls a power transistor Q1 by a constant- current circuit (drive circuit 12). The constant-current circuit is composed by comprising a control transistor Q2, whose collector terminal (one of the input or the output terminals) is connected to the base terminal of the power transistor, a constant-voltage generating resistor R1, whose one terminal is connected to the emitter terminal (the other terminal) of the control transistor Q2 and the other terminal is grounded, and a constant-voltage dropping circuit 121, whose one terminal is connected to the base terminal of the control transistor and the other terminal is grounded. When a control pulse P is inputted to the base terminal of the control transistor Q2, the control transistor Q2 operates, so that its ON-current becomes constant.
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