# US 11,452,189 B2 · External zero-crossing detection circuit for LED drivers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,452,189 B2 - Document ID: US11452189B2 - Status: Granted - Kind: B2 - Application number: 17/393,895 - Filed: 2021-08-04 - Published: 2022-02-17 - Granted: 2022-09-20 - Earliest claimed: 2020-08-14 - Assignees: Erp Power, LLC - Applicants: Erp Power, LLC - Inventors: Michael Archer; Louis Chen - Web page: https://patentgrep.com/patent/US11452189B2 ## CPC - H05B 45/38: using boost topology - H02M 1/083: {for the ignition at the zero crossing of the voltage or the current} - H02M 1/126: {using passive filters} - H02M 1/4225: {using a non-isolated boost converter} - H05B 45/355: Power factor correction [PFC]; Reactive power compensation - H05B 45/382: with galvanic isolation between input and output - G01R 19/175: Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero - H02M 1/4258: {using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage (H02M1/4241 takes precedence)} - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A zero-crossing detection circuit coupled to a power factor correction (PFC) controller of a power supply system includes a zener diode configured to generate a zener reference signal, and an operational amplifier coupled to the zener diode and configured to receive the zener reference signal and a feedback signal corresponding to an output current of the power supply system, and to generate a zero-crossing signal to a zero-crossing input of the PFC controller. ## Claims ### Claim 1 A zero-crossing detection circuit coupled to a power factor correction (PFC) controller of a power supply system, the zero-crossing detection circuit comprising: a zener diode configured to generate a zener reference signal; and an operational amplifier coupled to the zener diode and having an input terminal directly coupled to the PFC controller, the operational amplifier being configured to receive the zener reference signal and a feedback signal corresponding to an output current of the power supply system, and to generate a zero-crossing signal for transmission to a zero-crossing input of the PFC controller, the zero-crossing signal being configured to variably control an off-time of the PFC controller, wherein the PFC controller is configured to reduce a total harmonic distortion (THD) of the power supply system. ### Claim 2 (depends on 1) The zero-crossing detection circuit of claim 1, wherein a cathode of the zener diode is coupled to a positive input terminal of the operational amplifier, and wherein a negative input terminal of the operational amplifier is configured to receive the feedback signal. ### Claim 3 (depends on 1) The zero-crossing detection circuit of claim 1, wherein a negative input terminal of the operational amplifier is coupled to a compare input of the PFC controller. ### Claim 4 (depends on 1) The zero-crossing detection circuit of claim 1, wherein the zener diode is biased by a gate control signal output by the PFC controller, and wherein an off-time of the gate control signal is based on the zero-crossing signal. ### Claim 5 (depends on 1) The zero-crossing detection circuit of claim 1, wherein the zener reference signal is based on a gate control signal output by the PFC controller. ### Claim 6 (depends on 1) The zero-crossing detection circuit of claim 1, wherein the zener reference signal is configured to decay in response to the PFC controller being turned off. ### Claim 7 (depends on 1) The zero-crossing detection circuit of claim 1, further comprising: a diode coupled between an output of the operational amplifier and the zero-crossing input of the PFC controller and configured to prevent a signal entering the zero-crossing input from being pulled down. ### Claim 8 (depends on 1) The zero-crossing detection circuit of claim 1, further comprising: a low-pass filter configured to filter a gate control signal output by the PFC controller and to bias the zener diode with the filtered gate control signal. ### Claim 9 (depends on 1) The zero-crossing detection circuit of claim 1, wherein the feedback signal is based on the output current of the power supply system and a brightness setting of a light source coupled to the power supply system. ### Claim 10 A power supply system comprising: a power factor correction (PFC) controller comprising a zero-crossing input, and configured to generate a gate control signal based on a zero-crossing signal received at the zero-crossing input to reduce a total harmonic distortion (THD) of the power supply system; and a zero-crossing detection circuit coupled to the PFC controller, the zero-crossing detection circuit comprising: a zener diode configured to generate a zener reference signal; and an operational amplifier coupled to the zener diode and having an input terminal directly coupled to the PFC controller, the operational amplifier being configured to receive the zener reference signal and a feedback signal corresponding to an output current of the power supply system, and to generate the zero-crossing signal to variably control an off-time of the PFC controller. ### Claim 11 (depends on 10) The power supply system of claim 10, wherein an off-time of the gate control signal is based on the zero-crossing signal. ### Claim 12 (depends on 10) The power supply system of claim 10, wherein a cathode of the zener diode is coupled to a positive input terminal of the operational amplifier, and wherein a negative input terminal of the operational amplifier is coupled to a compare input of the PFC controller and is configured to receive the feedback signal. ### Claim 13 (depends on 10) The power supply system of claim 10, wherein the zener diode is biased by the gate control signal output by the PFC controller. ### Claim 14 (depends on 10) The power supply system of claim 10, wherein the zener reference signal is based on the gate control signal, and is configured to decay in response to the PFC controller being turned off. ### Claim 15 (depends on 10) The power supply system of claim 10, further comprising: a diode coupled between an output of the operational amplifier and the zero-crossing input of the PFC controller and configured to prevent a signal entering the zero-crossing input from being pulled down. ### Claim 16 (depends on 10) The power supply system of claim 10, further comprising: a low-pass filter configured to filter the gate control signal output by the PFC controller and to bias the zener diode with the filtered gate control signal. ### Claim 17 (depends on 10) The power supply system of claim 10, wherein the PFC controller is configured to reduce the total harmonic distortion and increase a power factor of the power supply system. ### Claim 18 (depends on 10) The power supply system of claim 10, further comprising: a sense resistor coupled to an output of the power supply system and configured to measure an output signal of the power supply system. ### Claim 19 (depends on 18) The power supply system of claim 18, further comprising: an error amplifier configured to compare the output signal with an output reference signal and to generate the feedback signal, wherein the output reference signal is based on a brightness setting of a light source coupled to the power supply system. ### Claim 20 (depends on 19) The power supply system of claim 19, further comprising: an optocoupler coupled between the error amplifier and the operational amplifier and configured to communicate the feedback signal.