| 摘要 |
A detector circuit for detecting a malfunction of a circuit due to a low third power supply voltage that has the same amplitude and potential as an input signal is provided. Based on an output signal of the detector circuit, whether an output of a second power supply voltage generation circuit for activating a heater driving circuit is allowed or not is determined. When the third power supply voltage is low and the heater driving circuit operates improperly, no power supply voltage is supplied from the second power supply voltage generation circuit. Since no power supply voltage is supplied to the heater driving circuit, the heater driving circuit does not drive a corresponding heater.
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