Patent ID: 8450994
Filing Date: 2013-05-28
Classification: G01R

Abstract:
1. A voltage application time period measuring circuit for measuring a voltage application time period of a voltage applied from a commercial power supply to an electronic device, comprising: a voltage monitoring circuit for monitoring a direct current power supply voltage supplied from an AC/DC converter based on an alternating current voltage from the commercial power supply, generating a connection signal when the electronic device is connected to the commercial power supply, and generating a disconnection signal when the electronic device is not connected to the commercial power supply; a counter for measuring the voltage application time period; a voltage application time period memory including a nonvolatile semiconductor device, for storing the voltage application time period; and a waveform shaping circuit for generating a square-wave voltage, wherein when the connection signal is generated from the voltage monitoring circuit, the voltage application time period is read from the voltage application time period memory to the counter and measured by the counter based on the square-wave voltage, and when the voltage application time period reaches a preset voltage application time period, the voltage application time period measuring circuit generates a detection signal.