Electronic controller for circuit breaker

Abstract

Electronic controller of circuit breaker, low cost and high reliability, including new current sampling circuit, current transformer, microcontroller and power supply circuit; new current sampling circuit includes current transformer interface, rectification unit, half-wave current conversion circuit and signal lifting circuit; the half-wave current conversion circuit is connected with the rectifier unit, and the signal lifting circuit is connected with the half-wave current conversion circuit to raise the half-wave sampled voltage signal to a positive signal by raising the reference voltage Vref; the power supply circuit includes a power starting circuit, a power supply The start-up circuit includes a voltage monitoring circuit, an analog load unit and a power conversion chip U2; when the voltage of the power supply is lower than the start-up threshold, the voltage monitoring circuit makes the power conversion chip U2 not work and connects the power supply and the analog load unit; when the voltage of the power supply When it is greater than the startup threshold, the voltage monitoring circuit makes the power conversion chip U2 output the working voltage to the normal working load and cuts off the connection between the power supply and the analog load unit.

Description

technical field [0001] The invention belongs to the field of low-voltage electrical appliances, and relates to a novel current sampling circuit, in particular to a current sampling circuit suitable for an electronic controller of a molded case circuit breaker and an electronic controller of the circuit breaker. Background technique [0002] The current protection methods of low-voltage circuit breakers were initially thermal magnetic and electromagnetic. With the development of electronic technology, electronic controllers were developed and used in the 1990s. Electronic controllers use the output of current transformers as current sampling signals. At the same time The output of the current transformer is used as the power supply of the electronic trip unit. [0003] However, due to the limited output energy and low output power of the current transformer of the intelligent molded case circuit breaker, low power consumption is required for the power consumption of the contr...

AI Technical Summary

Problems solved by technology

[0004] The current sampling circuit of the existing electronic controller such as Figure 1-2 As shown, since the full-wave rectification method is adopted, and the signal is a negative signal, it needs to be reversely amplified by the operational amplifier, resulting in the following defects and deficiencies in the controller: 1) Due to the increase in components, the layout area of ​​the PCB board increases, The volume of the controller is larger; 2) Due to the increase of the operational amplifier for reverse amplification processing, the power consumption of the controller increases, and the requirements for the transformer increase; 3) Due to the increase in components, the cost increases, making the smart molded case circuit breaker The cost is high; 4) Due to the use of full-wave rectification, the ground current cannot be sampled, and the controller cannot realize the ground protection function

Since the back-end load loses the power supply, the power supply voltage Vin will continue to rise, and it will be higher than the conduction voltage of the voltage regulator tube DZ1 again, and the cycle repeats, so the power chip U1 is always in the cycle working state of on and off, which will make the electronic The controller is in an unstable working state, prone to faults such as malfunction and display

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