Application of Current Transformer in Overcurrent Detection of Induction Cooker

There are many circuits for current detection. Generally, the current signal is converted into a voltage signal, and then the voltage is detected through the AD port of the single-chip microcomputer. For large voltage and large current occasions, the voltage is generally reduced before detection. Current transformers are based on this principle. It uses the principle of electromagnetic induction to convert the large current of the primary to the small current of the secondary.

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The primary winding of the current transformer is generally very small, and it is stringed in the line of the measured current.

Current transformers are widely used in the overcurrent detection of induction cookers. The following figure shows a part of the current detection circuit of a current transformer. Its ultimate purpose is to test the working current of the circuit, so as to continuously adjust the power output of the induction cooker to keep its work stable. The circuit is mainly composed of current transformers, resistors, capacitors, etc. Working principle: The AC voltage is obtained again after the mains passes through the power transformer. After rectification by the rectifier diodes D1-D4 and filtered by the electrolytic capacitor MC1, a smoother DC voltage is obtained, and the signal obtained after being divided by R3 and R4 is sent to IC, IC detects the magnitude of the voltage sent to judge the magnitude of the current, the greater the voltage, the greater the current, so IC will control the on-time of the IGBT switch to ensure the stability of the power output. Some current detection circuits are composed of LM339, which compare the voltages of the two to output a signal, and some are composed of triodes, which judge whether there is overcurrent by judging the high and low levels.

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