| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect output detection voltages, corresponding to respective regions, appropriately without being interdependent, by differentiating the detection characteristics of the output detection voltage, detected by dividing it with a resistance voltage-dividing circuit, in a rated operation region and a protective operation region lower than that.SOLUTION: An output detection voltage Vs is outputted by dividing the output voltage from a step-up chopper circuit 10 by means of a resistance voltage-dividing circuit, and a control IC 30 is provided with a normal voltage detecting section 36 and a start voltage detecting section 38. A control section 32 starts switching operation of a FET 20 when a start signal is obtained, and operates the FET 20 in a rated operation range if a normal voltage detection signal has been obtained after start. A correction circuit 40 feeds a bias current to a resistor 28 of the resistance voltage-dividing circuit by conducting a diode 44 connected with a voltage source 42, and generates a bias voltage, and then raises the output detection voltage of the resistance voltage-dividing circuit by the bias voltage, thus obtaining the characteristics different from the output voltage detection characteristics determined by the resistance ratio of the resistance voltage-dividing circuit.</p> |
