# US 2014/0191684 A1 · Systems and methods for a hysteresis based driver using a led as a voltage reference > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0191684 A1 - Document ID: US20140191684A1 - Status: Published application - Kind: A1 - Application number: 13/734,155 - Filed: 2013-01-04 - Published: 2014-07-10 - Earliest claimed: 2013-01-04 - Assignees: Integrated Illumination Systems, Inc. - Inventors: Charles Valois - Web page: https://patentgrep.com/patent/US20140191684A1 ## CPC - H05B 45/3725: Switched mode power supply [SMPS] - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract The present disclosure is directed to a hysteresis based driver that incorporates the forward voltage of the LEDs being driven into the design of the driver itself. Instead of providing a typical fixed voltage reference, the forward voltage of one or more LEDS driven by the driver is used as a voltage reference. As the input voltage varies during operation of the one or more LEDs, the current varies as well. This current change is larger than it would be without the LEDs and only resistors. This variable current measurement may be used as input into a hysteresis circuit that controls the switch that turns on and off the one or more LEDs. As such, the driver may not incorporate or use a typical fixed voltage reference such as one provided by a zener diode. ## Claims ### Claim 1 A driver for one or more light emitting diodes (LEDs) that incorporates forward voltage of the one or more LEDs to provide hysteresis, the driver comprising: a first input to receive an input voltage; a switch electrically coupled to the first input and electrically coupled to one or more light emitting diodes (LEDs), an output of the switch, when switched on, to provide voltage to the one or more LEDs; a current measurement component electrically coupled to the one or more LEDS, to measure current through the one or more LEDs based on forward voltage of the one or more LEDs; a hysteresis component to receive as input the input voltage and a measurement of voltage based on the current measured by the current measurement component; wherein the current measurement component is configured to measure changes to the current based on changes to the forward voltage of the one or more LEDs; and wherein the hysteresis component is electrically coupled to the switch to turn the switch off and on responsive to changes to the input voltage in conjunction with the changes to the forward voltage of the one or more LEDs, as measured by the current measurement component, being above or below a threshold. ### Claim 2 (depends on 1) The driver of claim 1, further comprising a ballast resistor electrically coupled to the output of the switch, the ballast resistor comprising a predetermined resistance to provide a current, when the switch is on, to the one or more LEDs below the maximum rating of the one or more LEDs. ### Claim 3 (depends on 1) The driver of claim 1, wherein the hysteresis component comprises a comparator that compares the input voltage to the measurement of voltage based on the current measured by the current measurement component. ### Claim 4 (depends on 3) The driver of claim 3, wherein the hysteresis component further comprises a feed forward resistor electrically coupled between input and output of the comparator, the feed forward resistor comprising a predetermined resistance that provides a smaller effect than the input voltage to the comparator and a larger effect than an offset voltage of the comparator. ### Claim 5 (depends on 1) The driver of claim 1, further comprising a filter electrically coupled between the current measurement component and the hysteresis component to provide a filtered version of the current measurement from the current measurement component as input to the hysteresis component, the filter configured to have a predetermined oscillation frequency to avoid exceeding a threshold of the switch. ### Claim 6 (depends on 1) The driver of claim 1, wherein the current measurement component includes a current sense resistor to convert into voltage the measurement of current through the one or more LEDs. ### Claim 7 (depends on 1) The driver of claim 1, wherein current to the one or more LEDs is regulated as the voltage output from the one or more LEDs changes with a lesser effect than changes to the input voltage. ### Claim 8 A driver for one or more light emitting diodes (LEDs) that uses forward voltage of the one or more LEDs as a reference voltage, the driver comprising: a first input to receive an input voltage; a switch electrically coupled to the first input and electrically coupled to one or more light emitting diodes (LEDs), an output of the switch, when switched on, to provide voltage to the one or more LEDs; a measurement component electrically coupled to the one or more LEDs, to measure voltage across the one or more LEDs based on changes in forward voltage of the one or more LEDs; a comparator to receive as a reference voltage a measurement of voltage from the measurement component, the comparator configured to compare the reference voltage to the input voltage; wherein the comparator is electrically coupled to the switch to turn the switch off and on responsive to comparison of the input voltage to the reference voltage comprising forward voltage of the one or more LEDs. ### Claim 9 (depends on 8) The driver of claim 8, further comprising a ballast resistor electrically coupled to the output of the switch, the ballast resistor comprising a predetermined resistance to provide a current, when the switch is on, to the one or more LEDs below the maximum rating of the one or more LEDs. ### Claim 10 (depends on 8) The driver of claim 8, further comprising a feed forward resistor electrically coupled between input and output of the comparator, the feed forward resistor comprising a predetermined resistance that provides a smaller effect than the input voltage to the comparator and a larger effect than an offset voltage of the comparator. ### Claim 11 (depends on 8) The driver of claim 8, further comprising a filter electrically coupled between the measurement component and the comparator to provide a filtered version of the current measurement from the measurement component as input to the comparator, the filter configured to have a predetermined oscillation frequency to avoid exceeding a threshold of the switch. ### Claim 12 (depends on 1) The driver of claim 1, wherein the measurement component includes a current sense resistor to convert into voltage the measurement of current through the one or more LEDs. ### Claim 13 (depends on 1) The driver of claim 1, wherein changes to the forward voltage of the one or more LEDs provides a stable reference voltage to the comparator. ### Claim 14 (depends on 1) The driver of claim 1, wherein the driver does not have a reference voltage for the comparator other than a stable reference voltage provided by changes to the current through the one or more LEDs. ### Claim 15 A driver for one or more light emitting diodes (LEDs) that automatically provides varying frequency, the driver comprising: a first input to receive an input voltage; a switch electrically coupled to the first input and electrically coupled to one or more light emitting diodes (LEDs), an output of the switch, when switched on, to provide voltage to the one or more LEDs; a measurement component electrically coupled to the one or more LEDs, to measure current through the one or more LEDs based on changes to the input voltage; a hysteresis component to receive as input the input voltage and a measurement of voltage responsive to the current measurement component; wherein the measurement component is configured to measure a voltage output from the one or more LEDs; wherein the hysteresis component is electrically coupled to the switch to turn the switch off and on responsive to the changes to the voltage output, the voltage output to increase with a lesser effect than changes to the input voltage; and wherein the driver is configured to have times the switch is on vary based on changes to the input voltage. ### Claim 16 (depends on 15) The driver of claim 15, wherein the hysteresis component comprises a comparator and a feed forward resistor electrically coupled between input and output of the comparator, the feed forward resistor comprising a predetermined resistance that provides a smaller effect than the input voltage to the comparator and a larger effect than an offset voltage of the comparator. ### Claim 17 (depends on 15) The driver of claim 15, further comprising a filter electrically coupled between the measurement component and the hysteresis component to provide a filtered version of the current measurement from the measurement component as input to the hysteresis component, the filter configured to have a predetermined oscillation frequency to avoid exceeding a threshold of the switch. ### Claim 18 (depends on 17) The driver of claim 17, wherein during a charging part of oscillation the filter reacts more quickly as the input voltage increases. ### Claim 19 (depends on 15) The driver of claim 15, wherein the measurement component includes a current sense resistor to convert into voltage the measurement of current through the one or more LEDs. ### Claim 20 (depends on 15) The driver of claim 15, wherein oscillation varies inversely with input voltage.