Patent ID: 7652496

Claim:
A commutation failure detection circuit for a back-to-back silicon controlled rectifier (SCR) circuit, comprising: a first detecting signal generator coupled to the back-to-back SCR circuit for detecting a commutation at a negative half cycle of an AC input voltage, comprising: a first non-conductive signal amplifier circuit generating a first non-conductive signal when the back-to-back SCR circuit is not conductive at the negative half cycle of the AC input voltage; a first non-conductive signal driver receiving and transferring the first non-conductive signal; and a first non-conductive signal isolator receiving the transferred first non-conductive signal for generating a first commutation detecting signal at a first status when the first non-conductive signal is absent; and a second detecting signal generator coupled to the back-to-back SCR circuit for detecting the commutation at a positive half cycle of the AC input voltage, comprising: a second non-conductive signal amplifier circuit generating a second non-conductive signal when the back-to-back SCR circuit is not conductive at the positive half cycle of the AC input voltage; a second non-conductive signal driver receiving and transferring the second non-conductive signal; and a second non-conductive signal isolator receiving the transferred second non-conductive signal for generating a second commutation detecting signal at the first status when the second non-conductive signal is absent.