# US 2019/0174596 A1 · Led drive circuit and led lamp > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0174596 A1 - Document ID: US20190174596A1 - Status: Published application - Kind: A1 - Application number: 16/266,014 - Filed: 2019-02-02 - Published: 2019-06-06 - Earliest claimed: 2016-08-02 - Assignees: Opple Lighting Co., Ltd. - Applicants: Opple Lighting Co., Ltd. - Inventors: Wei WEN - Web page: https://patentgrep.com/patent/US20190174596A1 ## CPC - H05B 45/3578: Emulating the electrical or functional characteristics of discharge lamps - H05B 45/37: Converter circuits - H05B 45/50: responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits - H05B 45/58: involving end of life detection of LEDs - H05B 45/39: Circuits containing inverter bridges - Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED] - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract The present disclosure provides a light-emitting diode (LED) drive circuit and an LED lamp. The LED drive circuit includes: a feedback control circuit and a load impedance increasing circuit, where the feedback control circuit acquires the operating current of an LED, compares the operating current with a default threshold, drives the load impedance increasing circuit to operate when the operating current of the LED is greater than or equal to the threshold, and allows the load impedance increasing circuit not to operate when the operating current of the LED is less than the threshold; and the load equivalent impedance of the LED drive circuit is increased when the load impedance increasing circuit operates. ## Claims ### Claim 1 A light-emitting diode (LED) drive circuit, comprising: a feedback control circuit and a load impedance increasing circuit, wherein: the feedback control circuit acquires operating current of an LED, compares the operating current with a default threshold, drives the load impedance increasing circuit to operate when the operating current of the LED is greater than or equal to the threshold, and allows the load impedance increasing circuit not to operate when the operating current of the LED is less than the threshold; and the load equivalent impedance of the LED drive circuit is increased when the load impedance increasing circuit operates. ### Claim 2 (depends on 1) The LED drive circuit according to claim 1, further comprising: a rectifier bridge, and wherein the load impedance increasing circuit is disposed between the rectifier bridge and the LED. ### Claim 3 (depends on 2) The LED drive circuit according to claim 2, wherein: the load impedance increasing circuit comprises a load impedance increasing element and a switching element connected with the load impedance increasing element in parallel; when the switching element is switched on, the load impedance increasing element is bypassed; and when the switching element is switched off, the load impedance increasing element is connected to the LED drive circuit to increase the load equivalent impedance of the LED drive circuit. ### Claim 4 (depends on 3) The LED drive circuit according to claim 3, wherein the switching element comprises: a power triode, a field effect transistor (FET) or a relay. ### Claim 5 (depends on 3) The LED drive circuit according to claim 3, wherein: the threshold is a threshold voltage; the feedback control circuit comprises a current detection unit, a threshold comparison unit and a drive unit, and wherein the current detection unit acquires the operating current of the LED, converts the operating current into comparative voltage, and inputs the comparative voltage into the threshold comparison unit; and the threshold comparison unit compares the comparative voltage with the threshold voltage, controls the drive unit to start operating so as to drive the load impedance increasing circuit to operate when the comparative voltage is greater than or equal to the threshold voltage, and allows the drive unit not to operate and allows the load impedance increasing circuit not to operate when the comparative voltage is less than the threshold voltage. ### Claim 6 (depends on 5) The LED drive circuit according to claim 5, wherein the current detection unit comprises: a sampling resistor, a transformer or a Hall sensor. ### Claim 7 (depends on 6) The LED drive circuit according to claim 6, wherein the current detection unit comprises a sampling resistor, and wherein the sampling resistor is connected with the LED in series, and the comparative voltage is generated when the operating current of the LED flows across the sampling resistor. ### Claim 8 (depends on 7) The LED drive circuit according to claim 7, wherein the threshold comparison unit comprises a comparator, and wherein the sampling resistor is connected to a positive end of the comparator, the threshold voltage is connected to a negative end of the comparator, an output of the comparator is connected to the drive unit, and the output of the comparator is connected to the positive end of the comparator. ### Claim 9 (depends on 8) The LED drive circuit according to claim 8, wherein the threshold comparison unit further comprises: a first resistor, a second resistor, a third resistor and a fourth resistor, and wherein the sampling resistor is connected to the positive end of the comparator through the first resistor, the threshold voltage is connected to the negative end of the comparator through the second resistor, the output of the comparator is connected to the positive end of the comparator through the third resistor, and the output of the comparator is connected to the drive unit through the fourth resistor. ### Claim 10 (depends on 5) The LED drive circuit according to claim 5, wherein the drive unit comprises: a switch triode, a current-limiting resistor and a fly-wheel diode, and wherein a base of the switch triode is connected to an output of the threshold comparison unit, an emitter of the switch triode is grounded, a collector of the switch triode is connected to the fly-wheel diode through the current-limiting resistor, and the fly-wheel diode is connected with the switching element of the load impedance increasing circuit in reverse parallel. ### Claim 11 (depends on 10) The LED drive circuit according to claim 10, further comprising a power conversion circuit, and wherein the load impedance increasing element is an impedance inductor; the switching element is a relay, the relay comprising a drive winding and a relay switch, wherein one end of the drive winding is connected to the collector of the switch triode through the current-limiting resistor, another end of the drive winding is connected to a power source, the drive winding is connected with the fly-wheel diode in reverse parallel, the relay switch is connected with the impedance inductor in parallel, and two ends of the impedance inductor are connected with the rectifier bridge and the power conversion circuit. ### Claim 12 (depends on 5) The LED drive circuit according to claim 5, further comprising a power conversion circuit, wherein the drive unit comprises: an optical coupling module, a first divider resistor, a second divider resistor and a voltage regulator diode, and wherein an input of the optical coupling module is connected to an output of the threshold comparison unit, an output of the optical coupling module is connected to the load impedance increasing circuit, a bus of the rectifier bridge is connected to the switching element of the load impedance increasing circuit through the first divider resistor and the second divider resistor, and two ends of the voltage regulator diode are connected with two ends of the switching element. ### Claim 13 (depends on 12) The LED drive circuit according to claim 12, wherein the load impedance increasing element is an impedance inductor, and the switching element is an FET, and wherein the bus of the rectifier bridge is connected to a gate electrode of the FET through the first divider resistor and the second divider resistor, the gate electrode of the FET is connected to the output of the optical coupling module, the gate electrode and a source electrode of the FET are connected with two ends of the voltage regulator diode, two ends of the impedance inductor are connected with the source electrode and a drain electrode of the FET, and one end of the impedance inductor connected with the source electrode of the FET is connected with the rectifier bridge; and another end of the impedance inductor connected with the drain electrode of the FET is connected with the power conversion circuit. ### Claim 14 An LED lamp, comprising a LED drive circuit and at least one LED connected with the LED drive circuit, wherein: the LED drive circuit comprises a feedback control circuit and a load impedance increasing circuit, wherein the feedback control circuit acquires operating current of an LED, compares the operating current with a default threshold, drives the load impedance increasing circuit to operate when the operating current of the LED is greater than or equal to the threshold, and allows the load impedance increasing circuit not to operate when the operating current of the LED is less than the threshold; and the load equivalent impedance of the LED drive circuit is increased when the load impedance increasing circuit operates; and the LED drive circuit is configured to drive the at least one LED to emit light after power-on. ### Claim 15 A method of utilizing a light-emitting diode (LED) drive circuit, comprising: acquiring, by a feedback control circuit, operating current of an LED, comparing the operating current with a default threshold, driving a load impedance increasing circuit to operate when the operating current of the LED is greater than or equal to the threshold, allowing the load impedance increasing circuit not to operate when the operating current of the LED is less than the threshold, and increasing the load equivalent impedance of the LED drive circuit when the load impedance increasing circuit operates. ### Claim 16 (depends on 15) the method of claim 15, further comprising: connecting a switching element of the load impedance increasing circuit with a load impedance increasing element of the load impedance increasing circuit in parallel; when the switching element is switched on, bypassing the load impedance increasing element; and when the switching element is switched off, connecting the load impedance increasing element to the LED drive circuit to increase the load equivalent impedance of the LED drive circuit.