| 摘要 |
<p>Presence/absence of failure of a PWM-driven load can easily be judged according to the state of pulse voltage applied to the load. A failure diagnosis apparatus (10) judges failure of an electromagnetic valve (2) pulse-width modulation driven by a drive circuit (4) in response to a control pulse signal (P1). A voltage signal (VA) generated by a pulse width modulation drive is input to a smoothing circuit (11) at a connection point (A) between the electromagnetic valve (2) and the drive circuit (4) so as to obtain a smoothing output voltage (VB). It is determined whether the level value of the smoothing output voltage (VB) is a predetermined value determined by the duty ratio of the control pulse signal (P1) which is a duty ratio set for pulse width modulation drive, thereby judging presence/absence of failure of the electromagnetic valve (2).</p> |
