| 摘要 |
An optically coupled solid state relay circuit is disclosed. A light emitting diode input circuit is utilized to trigger a photosensitive transistor. A trim resistor in the base of the photosensitive transistor is utilized to adjust the sensitivity of the circuit. The photosensitive transistor is utilized, in conjunction with other circuitry, to control a silicon controlled rectifier which provides gate drive to a triac. Voltage limiting circuitry is provided to insure that the solid state relay will switch only during those periods within a selected range of the zero crossing of the line voltage and half of the bridge circuit which provides single polarity operating voltages is comprised of fast recovery diodes to improve the circuit's ability to withstand rapid polarity reversals.
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