| 摘要 |
PURPOSE:To make a load voltage detecting transformer and a power transformer unnecessary, by inserting a voltage detecting circuit having a load voltage detecting resistance between the output terminal of a full wave rectifier and the connection point between a load and a phase controller. CONSTITUTION:A series circuit of diodes 46 and 47 is so provided that respective anodes are connected to both ends of a load 3. A series circuit consisting of a reverse blocking triode thyristor 49 and a voltage detecting resistance 50 is inserted between the output terminal of a full wave rectifier 4, whose inout terminal is connected to an AC power source 1, and the connection point between diodes 46 and 47. The thyristor 49 is made conductive synchronously with a bidirectional thyristor 2. As the result, a closed circuit where a series circuit consisting of the diode 46 (47), the thyristor 49, the resistance 50, a diode D3 (D1) is connected in parallel to the power source 1 is formed, and a full-wave rectified voltage corresponding to the voltage between both ends of the power source 1 is generated between both ends of the resistance 50. The voltage between both ends of the resistance 50 is used as a detection voltage, thereby making the load voltage detecting transformer and the power transformer unnecessary to reduce the cost. |
