| 摘要 |
A temperature detecting circuit detects the rise of ambient temperature, using a forward voltage drop across a diode. The temperature detecting circuit comprises a temperature detecting diode whose cathode is grounded, a first constant current supply device connected with the anode of the temperature detecting diode, for supplying a constant current Ia to the temperature-detecting diode, a rectifying diode whose cathode is connected with the anode of the temperature detecting diode, a second constant current supply device connected with the anode of the rectifying diode, for supplying a constant current Ib to the temperature-detecting diode, a comparator, and a transistor. When the voltage at the anode of the temperature-detecting diode is lower than a reference voltage, the comparator produces a high-level signal indicative of overheating. In response to this, the transistor shorts the anode of the rectifying diode to ground potential to supply the constant current Ib from the second constant current supply device directly to ground potential.
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