| 摘要 |
PURPOSE:To make it possible to construct the equipment with small loss for a load capacity by allowing an overload detection signal to turn off a switching element of an inverter and by resetting the overload detection signal information at the fall of the PWM waveform control. CONSTITUTION:An inverter controlling circuit divides a reference frequency of a reference signal oscillator 31 by means of dividers 32, 34, generating an output frequency and a carrier frequency of a PWM signal, and then outputs a sive wave signal 91 and a triangular wave signal 92. Then, it compares those signals in a PWM signal forming circuit 36, forming a PWM signal 93. The PWM signal 93 is output as a control signal of semiconductor switches 2A, 2D and the PWM signal 93 which is reversed by a NOT circuit 37 is output as a control signal of semiconductor switches 2B, 2C. The PWM signal 93 is led to a fall point signal forming circuit 40 and then a signal 94 which is always at the 'H' level is output and is sent to a flip flop circuit 46 and then a set signal 96 is output but it is reset by an excess current signal 95. As a result, an inverter as to correspond to the rated capacity of a load can be selected. |
