Himax Analogic, Inc.

Chin-Lung Wu

Kai-Ji Chen

Chun-Kai Wang

Aung Aung Yinn

A circuit and a method for driving light emitting diodes (LEDs) are provided. First, an input voltage is converted into an output voltage and the output voltage is transmitted to the anode terminals of LED strings. The output voltage is reduced when the output voltage is greater than a first threshold voltage and the output voltage is reduced when the lowest level among the cathode terminal voltages of all the LED strings is greater than a second threshold voltage. Thus, the output voltage can be maintained at a lower level for driving all the LED strings to reduce unnecessary power wastage.

Circuit and method for driving light emitting diodes

A driving circuit for a light emitting diode (LED) and a method thereof are provided. The driving circuit includes a voltage converting circuit and a reference voltage generator. The reference voltage generator generates a reference voltage according to the cathode voltage of the LED. The voltage converting circuit automatically adjusts the driving voltage of the LED based on the reference voltage so as to reduce the possibility of unnecessary power wastage caused by high driving voltage.

Driving circuit and method for light emitting diode

A light-emitting diode driving circuit includes a control circuit, a transistor switch and a compensating circuit. The control circuit receives an oscillating signal to generate a pulse drive signal. The transistor switch is activated by the pulse drive signal such that an inductor is charged by an input voltage, in which the inductor is arranged to deliver an inducting current to at least one light-emitting diode when the transistor switch is deactivated. The compensating circuit is coupled between the control circuit and a capacitor provided for reducing ripples of an output voltage corresponding to the inducting current. The compensating circuit performs a charging and discharging operation along with the capacitor when controlled by a dimming control signal provided to control brightness of the light-emitting diode.

Light-emitting diode driving circuit

A driving circuit includes a DC-to-DC voltage converter, a current source, a detector and a feedback control circuit. The DC-to-DC voltage converter has a switch and generates a driving voltage on first ends of the series of light emitting diodes, in which a magnitude of the driving voltage is correlated with conduction of the switch. The current source is coupled to second ends of the series of the light emitting diodes and provides driving currents flowing through the light emitting diodes. The detector generates a feedback voltage corresponding to a sum of voltages on the second ends of the series of the light emitting diodes. The feedback control circuit generates a first control signal which controls the conduction of the switch in response to the feedback voltage.

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Tainan County, Taiwan

Chin-Lung Wu