Patent ID: 9018845
Filing Date: 2015-04-28
Classification: H05B,Y02B

Abstract:
1. A circuit for adjusting current of a light-emitting diode (LED), comprising: a single-output constant current source, a plurality of LED output circuits and a control bus connected with the plurality of LED output circuits, each of the plurality of LED output circuits comprising a load circuit, an adjustment circuit, a current regulation circuit and an adjustment control circuit, wherein: the load circuit comprises a plurality of LEDs connected in series, one terminal of the load circuit is connected with a first output terminal of the single-output constant current source, and the other terminal of the load circuit is connected with an input terminal of the adjustment circuit; the adjustment circuit comprises an regulator connected with the load circuit and a current sampling circuit, one terminal of the current sampling circuit is connected with the regulator, and the other terminal of the current sampling circuit is connected with a second output terminal of the single-output constant current source, and an output terminal of the adjustment circuit is connected with an input terminal of the current regulation circuit; an output terminal of the current regulation circuit is connected with a first input terminal of the adjustment control circuit, and the current regulation circuit makes, as required, some adjustments to a sampled-current output from the adjustment circuit such that the sampled-current is converted into a control signal corresponding to the sampled-current, and the control signal is output to the adjustment control circuit; and a second input terminal of the adjustment control circuit is connected with the control bus and an output terminal of the adjustment control circuit is connected with the regulator, the adjustment control circuit compares the control signal with a voltage of the control bus, and adjusts impedance of the regulator according to the comparison result, so as to achieve adjustment for current of this LED output circuit; and the current regulation circuit comprises a second resistor, one terminal of the second resistor is connected with the output terminal of the adjustment circuit, and the other terminal of the second resistor is connected with a first switch and an input terminal of a filter circuit respectively, the other terminal of the first switch is connected to ground, the first switch is turned on or off under the control of a pulse signal, and an output terminal of the filter circuit is connected with the input terminal of the adjustment control circuit.