Using the OB2226 chip.
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The OB2226 is a high performance, high precision PWM controller with built-in error amplifier, load compensation, fixed frequency oscillator, soft start, cycle current limit, overload protection, output short circuit protection, overtemperature protection and VDD undervoltage protection. This is a dedicated power management chip used in induction cookers, widely used in low-power AC\/DC off-line switching power supplies, such as induction cookers, liquid crystal power supplies and other equipment.
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The OB2226 series has two packaging processes, one is OB2226SP, using a 7-pin DIP package, and the other is OB2226CPOB2226AP using an 8-pin SOP package.
Drive circuit Q300, Q301 and LM339. In addition, the 18V voltage supply instability, and the R209, R210 variable value of the power-on delay protection circuit will also lead to intermittent heating.