The core of intelligent circuit breaker is intelligent controller, which is also known as electronic trip, microprocessor trip and protection control unit, etc. It is the main basis to judge whether intelligent circuit breaker is advanced. DSP + CPLD mode, CPLD can be more simplified the design of the circuit components, simple logic program using VHDL language, by editing the function of the program can achieve some peripheral control circuit, DSP to save space and time, but also can realize serial port expansion, due to the circuit breaker when shut off, the closing function, produce strong If the electromagnetic effect is directly driven by the GPIO pin of DSP, the external electromagnetic interference may cause the DSP program to fly or reset, which seriously affects the execution effect. Therefore, the input and output of the switching parameters of the system are completed by CPLD, which improves the anti-interference ability of the system to a large extent. 2 key technology to achieve intelligent circuit breaker microprocessor has hardware generalization, flexible application, memory, calculation, table lookup ability, instruction system is suitable for real-time control, fast execution speed and a series of advantages, is the core of intelligent circuit breaker.