Induction cooker plate temperature and door control tube temperature detection circuit

Induction cooker plate temperature and door control tube temperature detection circuit

Shown is the induction tube temperature detection circuit . The temperature detection of the stove coil uses a
thermistor with a negative temperature coefficient. Its nominal value is 100 kn. When the temperature rises, its resistance value will drop rapidly. This resistor
is connected to the ◎ pin of voltage comparator U2C. If the temperature rises, the value of the external resistance of pin ◎ will decrease, and the voltage of pin ◎ will drop. When the voltage of U2C
's @ pin drops, the output voltage of @ pin will rise and become high level . The high level output by pin ⑧ will cause diode D17 to conduct, and
the voltage at the other end of diode D17 will increase, thus causing transistor VT8 to conduct, and the voltage at the collector of transistor VT8 will become low level.
The low level increases To the U2B@ pin, make the ⑦ pin of U2B become low level, which will make the ⑤ pin of U3A become low level, turning off
the output of the pulse width signal generating circuit.
    There is a temperature detection switch at the collector of the gate control tube, which is equivalent to a thermostat. At normal temperature, the temperature detection switch is short-circuited
(on state). When the temperature detection switch is turned on, it is equivalent to connecting pin ① of CN5 to ground, which is low level, and diode D18 is cut off. When the
gate control tube works for too long and the temperature rises to a certain level (exceeds the rated value), the temperature detection switch (temperature controller) will be disconnected,
the voltage at pin ① of CN5 will rise, and diode D18 will conduct Pass, high level is added to the base of transistor VT8, VT8 is turned on, and the pulse width signal generating
circuit is controlled.