Alarm circuit for induction cooker

Shown is the alarm circuit for an induction cooktop . When the induction cooker
sound.
    This circuit uses a voltage comparator SF324. It's actually an operational amplifier . This operational amplifier
determines the change of the signal output by its pin ⑧ based on the changes in the input signal levels of pins ◎ and ⑩.
    The 12 V voltage is added to one end of the buzzer through the lead, and the other end of the buzzer is connected to the @ pin of the operational amplifier SF324 (D). Since
one end of the buzzer is 12 V. If the voltage at the other end is lower than 12 V, a current will be generated in the buzzer, which will make the buzzer sound
. If the operational amplifier SF324 (D) outputs a pulse signal, the buzzer will also sound and the tone will change. This is
how the buzzer is driven.
    When the buzzer sounds and when it does not sound is mainly controlled by the control circuit. For example, when the microprocessor circuit detects overheating,
overvoltage, etc. or changes working status, it will generate a control signal. This control signal is fed into the reverse control transistor Q16 .
If the control signal sent to Q16 is high level, transistor Q16 will be turned on. After Q16 is turned on, the collector of the transistor will be grounded, and
the base of the transistor Q15 will also be grounded, and the transistor Q15 will be turned off; conversely, when the transistor Q16 is turned off, the transistor Q15 will be turned on. After transistor
Q15 is turned on, pin ⑨ of operational amplifier SF324 (C) becomes low voltage. If the transistor Q15 is turned off,
the ⑨ pin of the operational amplifier SF324 (c) will have a high voltage. The voltage of the ⑩ pin of the operational amplifier SF324 (C) is sent from the power supply through the voltage divider, and this voltage is
unchanged. Therefore, the voltage of the control signal is sent to the ◎ pin of SF324 (C). The level of the ◎ pin will change
the output of the operational amplifier SF324 (C), and the output of the operational amplifier SF324 (C) controls the transistor Q17. If the output of the operational amplifier SF324 (C) is high level,
the transistor Q17 will be turned on, and the @ pin of the operational amplifier SF324 (D) will become low level. If the transistor Q17 is turned off, the ⑩ of the operational amplifier
SF324 (D) will The pin will become high level. If the level of the @ pin is higher than the @ pin, the voltage of the @ pin of the operational amplifier SF324 will drop.
At this time, the buzzer will sound. Therefore, whether there is a fault will be detected by detecting the voltage, that is, if the buzzer does not
sound when it is supposed to sound, the voltage of the @ pin of the operational amplifier and the transistor Q17 should be detected. Operational amplifiers C and D are integrated in SF324. When the buzzer
stops alarming, SF324 should be detected. Focus on detecting the output end. If the output of the @ and @ pins is abnormal, you can first check
whether the SF324 power supply is normal. Because the power supply is abnormal, the operational amplifier cannot work properly. If the voltage is abnormal and the output is wrong, it means that
the operational amplifier SF324 is damaged and needs to be replaced.