| 摘要 |
PURPOSE:To simplify the titled circuit by driving a switching element and a circuit using an output level of a pulse width modulator so as to change/ discharge an equivalent capacitance at the input side of a pulse amplifier comprising the plural switching elements. CONSTITUTION:With a PWM signal Pd going to an H level, since a driver 39 outputs an L level and a driver 41 outputs an H level, a photocoupler 40 and a PNP transistor (TR) Q2 are turned off and an NPN Q1 and a photocoupler 43 are turned on. Then a pulse voltage is applied between the gate and source of a power TR 30 through the TR Q1 from the positive pole of a rectifier circuit 50, an equivalent capacitor of the gate and source is changed up, and when the voltage reaches a prescribed value or over, the TR 30 is turned on. With the signal Pd going to an L level, the TR Q1 is turned off, the TR Q2 is turned on and the electric charge of the said equivalent capacitance is discharged. TRs 31-33 are operated similarly to supply the AC power supply to a load 35. Thus, the charge/discharge circuit and the switching circuit are driven by one and same power supply to simplify the circuit constitution. |
