| 摘要 |
PROBLEM TO BE SOLVED: To reduce the power loss in a main switching power supply by shortening the turn-off time, without making the drive control circuit of a main switching element complicated. SOLUTION: Between a main control circuit 4 and a main switching element 2, a differential circuit is composed of a limiting resistor 6, a capacitor 7, a bias resistor 8, a parasitic capacity 9 of the main switching element. The constants of the limiting resistor 6, the capacitor 7, and the bias resistor 8 for constituting the differential circuit are set, so that the voltage of a gate terminal 2a is set to the threshold of the main switching element 2 or more when an 'on' signal is sent, and the voltage is set to 0 V or less when an 'off' signal is sent, thus applying reverse bias to the gate terminal 2a when the off signal is sent. By applying the reverse bias, charge being charged to the parasitic capacity 9 of the main switching element 2 is rapidly discharged, and the main switching element 2 is turned off, thus drastically reducing the turn-off time of the main switching element 2.
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