| 摘要 |
A LED driving circuit, a control circuit and associated current sensing circuit. The control circuit has a sensing circuit, an estimation circuit, an amplifying circuit, a comparing circuit, a zero-cross detection circuit and a logic circuit. The sensing circuit is configured to sense a switching current flowing through at least one switch of a switching circuit to provide a first sensing signal. The estimation circuit is configured to process the first sensing signal to provide a feedback signal, wherein the feedback signal is indicative of a average current signal flowing through a LED. An average current flowing through the LED is regulated by sensing a switching current flowing through at least one switch. |
| 主权项 |
1. A control circuit for a LED driving circuit, wherein the LED driving circuit comprises a switching circuit comprising at least one switch and an inductive element, and wherein the switching circuit is configured to receive a DC voltage signal for driving a plurality of LED, and to receive a control signal configured to control the at least one switch to switch on and off so as to regulate an average current flowing through the plurality of LED; the control circuit comprising:
a sensing circuit coupled between the at least one switch and a logic ground, wherein the sensing circuit is configured to sense a switching current signal flowing through the at least one switch, and to provide a first sensing signal, and wherein the first sensing signal is indicative of the switching current signal; an estimation circuit having an input terminal and an output terminal, wherein the input terminal of the estimation circuit is coupled to the sensing circuit for receiving the first sensing signal; and wherein the estimation circuit is configured to process the first sensing signal, and to provide a feedback signal at the output terminal, wherein the feedback signal is indicative of the average current signal flowing through the plurality of LED; an amplifying circuit having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of the amplifying circuit is coupled to the output terminal of the estimation circuit for receiving the feedback signal; and wherein the second input terminal of the amplifying circuit is configured to receive a reference signal, wherein the reference signal is indicative of a desired average current of the plurality of LED; and wherein the amplifying circuit is configured to amplify the difference of the feedback signal and the reference signal, and to provide an error signal at the output terminal; a comparing circuit having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of the comparing circuit is coupled to the output terminal of the amplifying circuit for receiving the error signal; and wherein the second input terminal of the comparing circuit is configured to receive the first sensing signal; and wherein the comparing circuit is configured to compare the error signal with the first sensing signal, and to provide a comparing signal at the output terminal; and wherein when the first sensing signal is larger than the error signal, the comparing signal is configured to turn the at least one switch off; and a zero-cross detection circuit having an input terminal and an output terminal, wherein the input terminal of the zero-cross detection circuit is coupled to the switching circuit, and configured to receive a current signal flowing through the inductive element so as to generate a second sensing signal, wherein the second sensing signal is indicative of the current signal flowing through the inductive element; and wherein the zero-cross detection circuit is configured to compare the second sensing signal with a zero-cross threshold, and to provide a zero-cross signal at the output terminal; and wherein when the second sensing signal decreases to the zero-cross threshold, the zero-cross signal is configured to turn the at least one switch on. |
