# US 10,772,168 B2 · LED driving circuit and driving method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,772,168 B2 - Document ID: US10772168B2 - Status: Granted - Kind: B2 - Application number: 16/259,637 - Filed: 2019-01-28 - Published: 2019-05-23 - Granted: 2020-09-08 - Earliest claimed: 2017-01-20 - Applicants: Shaanxi Reactor Microelectronics Co., Ltd - Inventors: Shihong Yang; Hu Wang - Web page: https://patentgrep.com/patent/US10772168B2 ## CPC - H05B 45/345: Current stabilisation; Maintaining constant current - F21S 4/10: with light sources attached to loose electric cables, e.g. Christmas tree lights - F21V 23/06: the elements being coupling devices {, e.g. connectors} - H05B 45/36: Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI] - H05B 47/28: Circuit arrangements for protecting against abnormal temperature - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - F21S: NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS - F21V: FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR ## Abstract An LED driving circuit and a driving method thereof. The LED driving circuit comprises a rectifying circuit (40), a filter circuit (20), a current limiting circuit (10), a detection and control circuit (30), and an LED lamp string. The rectifying circuit is connected to an alternating-current power supply, and the negative electrode of the rectifying circuit is connected to the second end of the filter circuit and the second end of the detection and control circuit; the input end of the current limiting circuit is connected to the positive electrode of the rectifying circuit, the first output end of the current limiting circuit is connected to the positive electrode of the LED lamp string and the input end of the filter circuit, and the second output end of the current limiting circuit is connected to the third end of the detection and control circuit. ## Claims ### Claim 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). ### Claim 2 (depends on 1) The LED driving circuit according to claim 1, wherein the detection and control circuit (30) comprises a control circuit (70) and a voltage-dividing circuit (60), and the voltage dividing circuit (60) comprises voltage-dividing resistors R1 and R2 which are connected in series. ### Claim 3 (depends on 2) The LED driving circuit according to claim 2, wherein the second output end of the current-limiting circuit (10) is connected with a third end of the control circuit (70), and the negative pole of the LED lamp string is connected with an input end of the control circuit (70) and an input end of the resistor R1; the resistor R1 is connected in series with the resistor R2, and a fourth end of the control circuit (70) is connected with an output end of the resistor R1 and an input end of the resistor R2; the negative pole of the rectifying circuit (40) is connected with a second end of the control circuit (70) and an output end of the resistor R2. ### Claim 4 (depends on 3) The LED driving circuit according to claim 3, wherein a filter capacitor C1 is added on the fourth end of the control circuit (70), and the capacitor C1 is connected in parallel with the resistor R2. ### Claim 5 (depends on 2) The LED driving circuit according to claim 2, wherein the control circuit (70) comprises a first power supply circuit (110), a reference circuit (120), a first driving circuit (130), a first current-sampling circuit (140), a voltage-sampling circuit (150), a pull-down current circuit (160) and a power tube Q1, wherein the reference circuit (120) is connected to the first power supply circuit (110) and the first driving circuit (130), the first driving circuit (130) is connected to a control end of the power tube Q1 and the first current-sampling circuit (140), and the voltage-sampling circuit (150) is connected to the pull-down current circuit (160) and the first current-sampling circuit (140). ### Claim 6 (depends on 5) The LED driving circuit according to claim 5, wherein the control circuit (70) is provided with a first over-temperature protection circuit (310) connected with the first driving circuit (130). ### Claim 7 (depends on 1) The LED driving circuit according to claim 1, wherein the current-limiting circuit (10) is used to control a charge current of filter circuit (20) and a current I3 in the LED lamp string. ### Claim 8 (depends on 1) The LED driving circuit according to claim 1, wherein the detection and control circuit (30) is used to detect a current in the LED lamp string and control the current-limiting circuit (10) and the filter circuit (20) according to a detection result. ### Claim 9 (depends on 1) The LED driving circuit according to claim 1, wherein the current-limiting circuit (10) comprises a second power supply circuit (170), a control and driving circuit (180), a second driving circuit (190), a second current-sampling circuit (300) and a power tube Q2, wherein the second driving circuit (190) is connected to the second power supply circuit (170), the control and driving circuit (180), the second current-sampling circuit (300) and a control end of the power tube Q2, and the second power supply circuit (170) is connected to the control and driving circuit (180). ### Claim 10 (depends on 9) The LED driving circuit according to claim 9, wherein the current-limiting circuit (10) is provided with a second over-temperature protection circuit (320) connected with the second driving circuit (190). ### Claim 11 A method of driving an LED driving circuit, wherein the LED driving circuit comprises a rectifying circuit (40), a filter circuit (20), a current-limiting circuit (10), a detection and control circuit (30) and an LED lamp string, the method comprising: using the detection and control circuit (30) to detect the first detection voltage V3 in the negative pole of the LED lamp string and control a magnitude of the current I3 flowing through the LED lamp string according to a magnitude of the first detection voltage V3, wherein when the first detection voltage V3 is smaller than a first set voltage value V31, no current flows through the LED lamp string, the first output current I2 of the current-limiting circuit (10) is a first constant current I21 used for charging a capacitor in the filter circuit (20) and at this time, a charge current I4 of the filter circuit (20) is the largest, and the second output current I5 of the current-limiting circuit (10) is zero; wherein when the first detection voltage V3 is equal to the first set voltage V31, the LED lamp string is conducted, there is a current flowing through the LED lamp string and at this time, the first output current I2 flowing out of the current-limiting circuit (10) remains as the first constant current I21, wherein the first constant current I21 is divided into two parts, one part of which is used for charging the filter circuit (20), and the other part flows through the LED lamp string for turning on the LED lamp string, and the second output current I5 of the current-limiting circuit (10) continues to be zero; wherein when the first detection voltage V3 is greater than a first set voltage V31 and smaller than a second set voltage V32, the first output current I2 flowing out of the current-limiting circuit (10) continues to remain as the first constant current I21 and with the increase of the first detection voltage V3, the current I3 flowing through the LED lamp string is increased, the charge current I4 of the filter circuit (20) is reduced and the second output current I5 of the current-limiting circuit (10) continues to be zero; wherein when the first detection voltage V3 is greater than or equal to the second set voltage V32 and smaller than a third set voltage V33, the first output current I2 flowing out of the current-limiting circuit (10) is the first constant current I21, the current I3 flowing through the LED lamp string under the control of the detection and control circuit (30) is a fourth constant current I32, and at this time, the fluctuation of the first detection voltage V3 does not cause the fluctuation of the current I3, and the second output current I5 of the current-limiting circuit (10) continues to be zero; wherein 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 flowing out of the current-limiting circuit (10) is reduced with the increase of the first detection voltage V3 and at the same time, the detection and control circuit (30) draws the second output current I5 from the current-limiting circuit (10), 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, the current I3 flowing through the LED lamp string under the control of the detection and control circuit (30) remains as the fourth constant current I32, and the second output current I5 is far smaller than the first output current I2; and wherein when the first detection voltage V3 is greater than or equal to the fourth set voltage V34, the first output current I2 flowing out of the current-limiting circuit (10) remains as a second constant current I22, the second output current I5 flowing out of the current-limiting circuit (10) remains as a third constant current I51 and at this time, the second constant current I22 is a minimum current flowing from the current-limiting circuit to the LED lamp string and the filter circuit (20), the third constant current I51 is a maximum current flowing from the current-limiting circuit to the detection and control circuit (30), and the third constant current I51 is far smaller than the second constant current I22. ### Claim 12 (depends on 11) The method according to claim 11, wherein a second detection voltage V4 is obtained by performing voltage division for the first detection voltage V3, and the voltage fluctuation of the second detection voltage V4 is correspondingly reduced in such a way that the fluctuation of the first output current I2 of the current-limiting circuit (10) is reduced correspondingly, and the current I3 on the LED lamp string and a voltage drop on the detection and control circuit (30) are relatively stable; further, different voltage division ratios may be correspondingly adapted to different input voltages. ### Claim 13 (depends on 12) The method according to claim 12, wherein a constant second detection voltage V4 is obtained by filtering the second detection voltage V4 in such a way that the first output current I2 of the current-limiting circuit (10) is a constant value correspondingly, thereby ensuring that the current I3 on the LED lamp string is constant and the voltage drop on the detection and control circuit (30) is stable.