Solid state relays are a type of power control switch implemented based on semiconductor devices. Typically, solid state relays use devices such as semiconductor triodes (transistors) and thyristors as control elements to control their on/off state. So, what is the difference between solid state relays and SCRs? In this article, we have collected some information that we hope will be of great value to our readers.

The working principle of solid-state relay

A control signal is used to drive the internal semiconductor device to control the circuit on and off. The control signal can be in the form of a DC voltage, pulse signal, etc. When the control signal is applied to the control side of the solid state relay, the control circuit generates a specific trigger signal that causes the semiconductor device (e.g., triode or thyristor) to turn on or off, thereby controlling the on/off state of the circuit. Compared to mechanical relays, solid-state relays have a faster response time and longer life, and do not produce mechanical vibration or arcing.

Solid-state relays and SCRs are two commonly used electronic components that can be used to achieve circuit control and switching operations, but there are some differences in their operating principles and characteristics.

Working principle is different: solid state relay is an electronic switching device, through the control of semiconductor devices to achieve circuit switching, its internal usually using MOSFET, IGBT and other semiconductor devices to replace the traditional mechanical relays to achieve high speed, low noise, no arc, no mechanical wear and other characteristics. The SCR is a semiconductor device that can be switched on and off by controlling its gate voltage to realize the circuit. The internal structure of a SCR is similar to a diode, but it has a control terminal that can be used to achieve positive half-cycle conduction or double conduction.

Different control voltage: The control voltage of solid state relays is generally low, usually within the range of 3-30V, so they can be directly controlled by logic circuits such as microcontrollers; while the control voltage of SCRs is higher, generally requiring more than 7-15V for normal conduction, so they need to be used with driving circuits.

Different scope of application: Solid-state relays are suitable for low-voltage, low-power control applications, such as electronic equipment, industrial automation, etc.; while SCRs are suitable for high-voltage, high-power control applications, such as home appliances, lighting, power tools, etc.

Different switching speeds: Solid-state relays are usually switched in microseconds or nanoseconds, allowing for high-speed switching, while SCRs are relatively slow, generally taking milliseconds or longer to complete a switching action.

Cost differences: Solid-state relays are relatively expensive to manufacture because they require multiple internal semiconductor devices to achieve switching control, while SCRs are relatively inexpensive to manufacture because they have only one internal semiconductor device.

In conclusion, solid state relays and SCRs are important electronic components with different features and applications, which need to be selected according to specific application scenarios and needs.