Voltage control circuit network device and method of detecting voltage

摘要

A voltage control circuit for implementing, e.g., the CPS function in which a high-accuracy comparison is performed between a high external voltage and a reference voltage. A diode-connected transistor converts the external voltage to a voltage lower than the external voltage in conjunction with an external voltage dropping resistor. A comparator compares the converted voltage with a specified comparison voltage. The size of the transistor is determined such that the ratio of an increment of the converted voltage to an increment of the external voltage is sufficiently high in a comparison region in which the external voltage is close to the reference voltage. A clamping circuit clamps the converted voltage with a specified limit voltage such that the converted voltage does not exceed the withstand voltage of the circuit.