| 摘要 |
<p>A solid state switching circuit for applying rectified alternating current to one or the other of two solenoid valve actuators and modulating that current from a pull-in value to a lower holding value has a separate power circuit for each solenoid and a common timing and trigger circuit. Each power circuit contains pair of diodes and a pair of silicon controlled rectifiers connected in a bridge circuit to supply its solenoid. The common timing and triggering circuit is connected to be energized whenever either power circuit is energized and contains a first DIAC control circuit for supplying triggering pulses early in each AC cycle and a second DIAC circuit for supplying pulses late in each AC cycle. The DIACs feed a coupling transformer which is coupled to the silicon controlled rectifiers of both power circuits. A time delay circuit biases a transistor to the on state after a predetermined time interval to disable the first DIAC control circuit.</p> |
