Method for over voltage protecting the diode string and light emitting diode driving circuit and light emitting diode driving system using the method

摘要

PURPOSE: A light emitting diode driving circuit, a light emitting diode drive system, and a diode string over voltage protection method are provided to uniformly maintain brightness of a light emitting diode and the light emitting diode driving circuit while increasing operating dependability of the light emitting diode driving circuit. CONSTITUTION: A diode string(610) comprises light emitting diodes which are serially connected. A constant current supply(620) is connected to one of the diode string terminals. An over voltage protection circuit(630) comprises a zener diode(ZD), a protective resistance(Rc), a comparison voltage source(631), and a comparator(COM). One terminal of the zener diode is connected with a common terminal of the constant current supply and the diode string.