Solid State Power Controllers (SSPC) Information

Solid State Power Controllers (SSPC) Information

Solid state power controllers (SSPC) are semiconductor devices that control power (voltage and/or current) supplied to a load. They perform supervisory and diagnostic functions in order to identify overload conditions and prevent short circuits. There are several basic types of solid state power controllers (SSPC). AC controllers are designed to switch alternating current (AC) voltages. DC controllers are designed to switch direct current (DC) voltages. AC/DC controllers are designed to switch both AC and DC voltages. Analog controllers use variable voltage, current, or some other method of analog control. Microcontrollers are complete computer systems on a chip. They typically combine an arithmetic logic unit (ALU), memory, timer/counters, serial port, input/output (I/O) ports, and clock oscillator. Microcontrollers require programming from external devices. Programmable sold-state power controllers (SSPCs) can be programmed by a computer, or by a specialized or proprietary programming method. 


Specifications for solid state power controllers (SSPC) include dropout voltage, input voltage, load voltage, and maximum load current. Dropout voltage (must-release voltage, turn-off voltage) is the voltage applied to the input at or below which the output enters the OFF state. Input voltage (must operate voltage, pickup voltage, turn-on voltage) is the range of voltages which, when applied across the input terminals, maintains the ON condition across the output terminal. Load voltage (maximum switching voltage, line voltage) is the range of output supply voltages over which the SSPC normally operates. Maximum load current (maximum switching voltage range, maximum switching current) is the maximum continuous current allowed across SSPC output terminals under specified heat dissipation and ambient-temperature conditions. Other specifications for solid state power controllers (SSPC) include the number of input channels and the input current range. 

Differences Between Solid State Power Controllers (SSPC)

Solid state power controllers (SSPC) differ in terms of construction, output device, and features. There are two basic constructions: epoxy shell and plastic mold. Output devices include bipolar junction transistors (BJT), metal-oxide field-effect transistors (MOSFET), silicon-controlled rectifiers, and triacs. In terms of features, some solid-state power controllers (SSPCs) provide analog switching, high voltage isolation, instant trip protection, nuisance trip suppression, over current protection, overvoltage protection, or reverse protection.  Others are bounce-free, electromagnetic interference (EMI) tolerant), opto-isolated, or radiation hardened. Solid state power controllers (SSPC) with a built-in heat sink, internal snubber, soft turn-on, thermal memory, true l2t protection, and visual indicators are also available.