Solid state relay SSR internal circuit

6.3V220UF Volume: 5X8 own factory direct sales - solid capacitor - patch aluminum

Photocoupler

Typical circuits for power control include SSR (solid state relay) switching circuit, zero voltage switching on/off control circuit, bidirectional thyristor phase control circuit, and transistor DC voltage control circuit.
The SSR is an electronic switch that outputs an on/off according to the presence or absence of current at the input. It has a long life and high reliability compared to relays with mechanical contacts.
The internal circuit of the SSR is shown in the figure. If a DC voltage is applied to its input terminal, a current flows through the LED in the photocoupler, and the LED emits light. When the phototransistor PT receives the LED and the PT is turned on, the DC voltage signal triggers the bidirectional transistor through the BG1, SCR and D1-D4 in the zero voltage switching circuit to turn it on, and the load has current.