| 摘要 |
PURPOSE:To suppress overcurrent in the inverter by providing memory means for storing the fact that a load current exceeds a predetermined value until the subsequent sampling timing and automatically reducing the pulse width of a modulated pulse in accordance with the output signal from the memory means. CONSTITUTION:The transistor Tr or the inverter 9 of pulse width modulation type is driven by a circuit including a flip-flop 3 for storing the overcurrent, a pulse width modulator 2 and an overcurrent detector 5. When the load current becomes high to exceed the rated current of the transistor Tr, a signal from the detector 12 is applied to the detector 5, thereby resetting the flip-flop 3 and closing an AND gate 7, and the modulator 2 is inhibited until the output pulse of the modulator 2 becomes next sampling period. Accordingly, since the transistor can be effectively protected against the overload, a transistor of low rated value can be used. |
