Patent ID: 7218062
Filing Date: 2007-05-15
Classification: H05B,Y10S

Abstract:
1. A protective device used for a CCFL driving system, the protective device is used to protect a control circuit and a CCFL of the CCFL driving system, comprising: (a) a short detecting circuit coupling with a high terminal of the CCFL and a power supply through a step-down capacitor, wherein the short detecting circuit receives a high AC power at the high terminal of the CCFL, and outputs a short-circuit protective signal to the control circuit when a shorting event occurs to the CCFL; (b) a rectified diode coupling with the high terminal of the CCFL through a step-down capacitor, wherein the rectified diode rectifies the high AC power and outputs a high DC power; (c) a first charging capacitor coupling with the rectified diode, wherein the first charging capacitor generates a detecting voltage based on the high DC power; (d) an open detecting circuit coupling with the first charging capacitor and having a threshold, wherein the open detecting circuit outputs an open-circuit protective signal to the control circuit when the detecting voltage is greater than the threshold; and (e) a lighting voltage-limited circuit coupling with the first charging capacitor and receiving the detecting voltage, and outputting an over-voltage protective signal to the control circuit.