Driving circuit for LED lamp
First Claim
1. A driving circuit for a light-emitting diode (LED) lamp comprising no more than 4 strings each having an input and an output terminals and comprising a plurality of LEDs coupled in series between the input and the output terminals, the driving circuit for receiving an on-off control signal and a dimming control signal and outputting a direct-current (DC) voltage of no more than 70 volts to the input terminals of the strings, the driving circuit comprising:
- a plurality of diodes, each having an anode terminal coupled to the output terminal of a corresponding string and a cathode terminal;
an overvoltage protection circuit, coupled to the cathode terminals of the diodes, for outputting an overvoltage control signal when a voltage at the output terminal of one of the strings is greater than a threshold voltage;
a plurality of constant current circuits, each coupled between the output terminal of a corresponding string and ground, the on-off control signal for controlling whether the constant current circuits work or not so as to control whether the LED lamp works or not, the dimming control signal for controlling a duty cycle of working of the constant current circuits so as to control a brightness of the LED lamp; and
a switch for forcing the on-off control signal to control the constant current circuits not to work when receiving the overvoltage control signal.
1 Assignment
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Accused Products
Abstract
A driving circuit for an LED lamp including no more than 4 strings each having an input and an output terminals outputs a DC voltage of no more than 70V to the input terminals. The driving circuit includes constant current circuits each coupled between the output terminal of a corresponding string and ground. An on-off control signal controls whether the constant current circuits work to control whether the LED lamp works. A dimming control signal controls a duty cycle of working of to the constant current circuits to control a brightness of the LED lamp. The driving circuit further includes an overvoltage protection circuit and a switch. When a voltage at one input terminal is too high or a short circuit occurs in one string, the overvoltage protection circuit outputs an overvoltage control signal and accordingly the switch forces the on-off control signal to control the constant current circuits not to work.
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Citations
10 Claims
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1. A driving circuit for a light-emitting diode (LED) lamp comprising no more than 4 strings each having an input and an output terminals and comprising a plurality of LEDs coupled in series between the input and the output terminals, the driving circuit for receiving an on-off control signal and a dimming control signal and outputting a direct-current (DC) voltage of no more than 70 volts to the input terminals of the strings, the driving circuit comprising:
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a plurality of diodes, each having an anode terminal coupled to the output terminal of a corresponding string and a cathode terminal; an overvoltage protection circuit, coupled to the cathode terminals of the diodes, for outputting an overvoltage control signal when a voltage at the output terminal of one of the strings is greater than a threshold voltage; a plurality of constant current circuits, each coupled between the output terminal of a corresponding string and ground, the on-off control signal for controlling whether the constant current circuits work or not so as to control whether the LED lamp works or not, the dimming control signal for controlling a duty cycle of working of the constant current circuits so as to control a brightness of the LED lamp; and a switch for forcing the on-off control signal to control the constant current circuits not to work when receiving the overvoltage control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification