| 摘要 |
An automatic start switch is provided to extend a lifetime of a contact point by preventing an arc discharge by selectively driving a triac based on an induced voltage on a motor start coil. A voltage source(101) full wave-rectifies and converts an input AC voltage to a constants level DC voltage. A start coil induced voltage rectifier(102) half-rectifies and converts the induced voltage at both ends of the start coil to a DC voltage. A peak holder(103) charges the half-rectified start coil induced voltage and converts the charged voltage to a DC voltage. A differentiation circuit(104) differentiates the DC voltage, which is charged at the peak holder, and delivers an induced voltage increase rate to a comparator. The comparator(105) compares an output from the differentiation circuit with a reference value and outputs a high or low signal. A start initial signal generator(108) outputs a high signal, which the output from the start coil induced voltage rectifier is lower than the reference value, and outputs a low signal, when the output from the start coil induced voltage rectifier is higher than the reference value. An inverter(106) inverts the output from the start initial signal generator and applies the result to a triac driver. The triac driver(107) couples or disconnects a start condenser with or from the start coil according to an output level of the inverter. |
