Patent ID: 8917026
Filing Date: 2014-12-23
Classification: H05B,Y02B

Abstract:
1. An electrical circuit comprising: a first LED string including at least one LED; a first transistor coupled to the first LED string at a first terminal of the first transistor, the first transistor operating in a linear mode; a second LED string including one or more color strings, each of the one or more color strings including at least one LED, the one or more color strings coupled in series, the first LED string and the second LED string coupled in parallel; a second transistor coupled to the second LED string at a first terminal of the second transistor, the second transistor operating in a linear mode; a bypass transistor coupled to one of the one or more color strings, the bypass transistor operating in a linear mode, a first terminal of the bypass transistor coupled to a first terminal of a corresponding color string, a second terminal of the bypass transistor coupled to a second terminal of the corresponding color string; a power supply configured to provide power to the first and second LED strings; a controller coupled to transistors including the first transistor, the second transistor and the bypass transistor at gate terminals of the transistors to control gate voltages of the transistors so that the first transistor, the second transistor and the bypass transistor are operating in the linear modes; and a digital-to-analog converter and at least one operational amplifier coupled between the controller and a gate terminal of the bypass transistor or coupled between the controller and a gate terminal of one of the first and second transistors.