US Patent No. 10,772,168

LED DRIVING CIRCUIT AND DRIVING METHOD THEREOF


Patent No. 10,772,168
Issue Date September 08, 2020
Title Led Driving Circuit And Driving Method Thereof
Inventorship

Claim of US Patent No. 10,772,168

1. A Light Emitting Diode (LED) driving circuit, comprising a rectifying circuit (40), a filter circuit (20), a current-limiting circuit (10), a detection and control circuit (30) and an LED lamp string, wherein, the rectifying circuit (40) is connected with an alternating-current power source, a negative pole of the rectifying circuit (40) is connected with a second end of the filter circuit (20) and a second end of the detection and control circuit (30); an input end of the current-limiting circuit (10) is connected with a positive pole of the rectifying circuit (40), a first output end of the current-limiting circuit (10) is connected with a positive pole of the LED lamp string and an input end of the filter circuit (20), and a second output end of the current-limiting circuit (10) is connected with a third end of the detection and control circuit (30); a negative pole of the LED lamp string is connected with an input end of the detection and control circuit (30);wherein the detection and control circuit (30) detects a voltage V3 in the negative pole of the LED lamp string, and the voltage V3 is referred to as a first detection voltage; when the first detection voltage V3 is smaller than a third set voltage V33, a first output current I2 flowing out of the first output end of the current-limiting circuit (10) is a first constant current I21, the first constant current I21 supplies a charge current of the filter circuit (20) and a current I3 of the LED lamp string, the current I3 flowing through the LED lamp string is controlled by the detection and control circuit (30), no current is output from the second output end of the current-limiting circuit (10), and a second output current I5 is zero; when the first detection voltage V3 is greater than or equal to the third set voltage V33 and smaller than a fourth set voltage V34, the first output current I2 of the current-limiting circuit (10) is reduced with the increase of the first detection voltage V3, and at the same time, the second output current I5 flowing from the current-limiting circuit (10) to the detection and control circuit (30) is increased with the increase of the first detection voltage V3; when the first detection voltage V3 is greater than or equal to the fourth set voltage V34, the first output current I2 of the current-limiting circuit (10) remains as a second constant current I22, and the second output current I5 of the current-limiting circuit (10) remains as a third constant current I51; at this time, the second constant current I22 is a minimum current flowing from the current-limiting circuit (10) to the LED lamp string and the filter circuit (20), and the third constant current I51 is a maximum current flowing from the current-limiting circuit to the detection and control circuit (30).