CA3079

Oct 1999 T NT D UC P R O L A C E ME E T OL E REP enter at tsc OBS ENDED m/ rt C MM l Suppo tersil.co O C E a .in NO R Technic or www our ERSIL T 8-IN 1-88 ® CA3059, CA3079 Zero-Voltage Switches for 50Hz-60Hz and 400Hz Thyristor Control Applications Description The CA3059 and CA3079 zero-voltage switches are monolithic silicon integrated circuits designed to control a thyristor in a variety of AC power switching applications for AC input voltages of 24V, 120V, 208/230V, and 277V at 50Hz-60Hz and 400Hz. Each of the zero-voltage switches incorporates 4 functional blocks (see the Functional Block Diagram) as follows: 1. Limiter-Power Supply - Permits operation directly from an AC line. 2. Differential On/Off Sensing Amplifier - Tests the condition of external sensors or command signals. Hysteresis or proportional-control capability may easily be implemented in this section. 3. Zero-Crossing Detector - Synchronizes the output pulses of the circuit at the time when the AC cycle is at zero voltage point; thereby eliminating radio-frequency interference (RFI) when used with resistive loads. 4. Triac Gating Circuit - Provides high-current pulses to the gate of the power controlling thyristor. In addition, the CA3059 provides the following important auxiliary functions (see the Functional Block Diagram). 1. A built-in protection circuit that may be actuated to remove drive from the triac if the sensor opens or shorts. 10 2. Thyristor firing may be inhibited through the action of an i...