Patent ID: 7109723

Claim:
A bridge type phase detection device comprises an electronic switch, a PWM IC, one or more than one transformer, a plurality of tubes, a voltage-detecting protection circuit and a first, second and third impedance; wherein a primary side of said transformer and said PWM IC coupling with said electronic switch, a secondary side of said transformer coupling with a first end of each one of said plurality of tubes, while a second end of each one of said plurality of tubes being grounded, and said voltage-detecting protection circuit coupling with said PWM IC; said bridge type phase detection device is characterized in: a first tube of said plurality of tubes has a phase opposite to that of a second tube of said plurality of tubes, and a first end of said first impedance coupling with said secondary side of said transformer and a first end of said first tube, a first end of said second impedance coupling with said secondary side of said transformer and a first end of said second tube, then a second end of said first impedance connecting to a second end of said second impedance to form a detection point, said detection point coupling with said third impedance and said voltage-detecting protection circuit; said detection point having a voltage value derived from calculating a sum of said phase of said first impedance and that of said second impedance, said voltage-detecting protection circuit detecting said detection point and obtaining approximately zero voltage at said detection point during normal operation, if said voltage-detecting protection circuit detecting a non-zero voltage, it is concluded that a tube anomaly is present.