# US 8,786,210 B2 · Drive circuit for light emitting diode > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,786,210 B2 - Document ID: US8786210B2 - Status: Granted - Kind: B2 - Application number: 12/827,688 - Filed: 2010-06-30 - Published: 2012-01-05 - Granted: 2014-07-22 - Earliest claimed: 2010-06-30 - Assignees: Welch Allyn, Inc. - Applicants: Paul Delucia - Inventors: Paul Delucia - Web page: https://patentgrep.com/patent/US8786210B2 ## CPC - A61B 1/227: for ears, i.e. otoscopes - H05B 45/3574: Emulating the electrical or functional characteristics of incandescent lamps - A61B 1/0684: {using light emitting diodes [LED]} - Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED] - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - 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 A drive circuit for a light emitting diode, and applications thereof, are disclosed. In one example, the drive circuit includes an input voltage and a ground, and a current control block including a voltage supply connection, a ground connection, a first voltage sense connection, and a second voltage sense connection. The voltage supply connection electrically connects to the input voltage and the ground connection connected to the ground. The drive circuit includes a current sense resistor connected to the first voltage sense connection, a first current adjustment resistor connected between the current sense resistor and the second voltage sense connection, and a second current adjustment resistor connected between the second voltage sense connection and the input voltage. A light emitting diode can connect from a point between the current sense resistor and the first current adjustment resistor to the ground. ## Claims ### Claim 1 A drive circuit for a light emitting diode, the drive circuit comprising: an input voltage and a ground; a current control block including a voltage supply connection, a ground connection, a first voltage sense connection, and a second voltage sense connection, the voltage supply connection electrically connected to the input voltage and the ground connection connected to the ground, the current control block configured to maintain a constant voltage across the first and second voltage sense connections; a current sense resistor connected to the first voltage sense connection; a first current adjustment resistor connected between the current sense resistor and the second voltage sense connection; and a second current adjustment resistor connected between the second voltage sense connection and the input voltage, thereby forming a voltage divider at the second voltage sense connection, such that adjustment of the input voltage proportionally changes a voltage across the light emitting diode at a constant current. ### Claim 2 (depends on 1) The drive circuit of claim 1, wherein a light emitting diode can be connected from a point between the current sense resistor and the first current adjustment resistor to the ground. ### Claim 3 (depends on 2) The drive circuit of claim 2, wherein current at a light emitting diode is at least partially controlled by the input voltage. ### Claim 4 (depends on 1) The drive circuit of claim 1, wherein the first current adjustment resistor has a resistance greater than a resistance of the current sense resistor. ### Claim 5 (depends on 1) The drive circuit of claim 1, wherein the current control block further includes an output voltage connection, and wherein a light emitting diode can be connected between the output voltage connection and the first voltage sense connection. ### Claim 6 (depends on 1) The drive circuit of claim 1, wherein the second current adjustment resistor has a resistance greater than a resistance of the current sense resistor. ### Claim 7 (depends on 1) The drive circuit of claim 1, wherein a dimming control is set by a ratio between the first and second current adjustment resistors. ### Claim 8 (depends on 1) The drive circuit of claim 1, wherein a plurality of light emitting diodes can be connected from a point between the current sense resistor and the first current adjustment resistor to the ground. ### Claim 9 (depends on 1) The drive circuit of claim 1, wherein the current control block comprises a switching controller. ### Claim 10 (depends on 9) The drive circuit of claim 9, further comprising a capacitor connected between the first and second voltage sense connections, the capacitor selected to provide an approximately constant voltage across the first and second voltage sense connections. ### Claim 11 (depends on 10) The drive circuit of claim 10, wherein the approximately constant voltage reflects an average current passing through a light emitting diode connected from a point between the current sense resistor and the first current adjustment resistor to the ground. ### Claim 12 A replacement light emitting diode package useable in an illumination device, the replacement light emitting diode package comprising: an input voltage and a ground; a current control block including a voltage supply connection, a ground connection, a first voltage sense connection, and a second voltage sense connection, the voltage supply connection electrically connected to the input voltage and the ground connection connected to the ground; the current control block configured to maintain a constant voltage across the first and second voltage sense connections; a current sense resistor connected to the first voltage sense connection; a first current adjustment resistor connected between the current sense resistor and the second voltage sense connection; a second current adjustment resistor connected between the second voltage sense connection and the input voltage; and a light emitting diode connected from a point between the current sense resistor and the first current adjustment resistor to the ground, such that adjustment of the input voltage proportionally changes a voltage across the light emitting diode at a constant current. ### Claim 13 (depends on 12) The replacement light emitting diode package of claim 12, wherein the illumination device comprises a medical scope. ### Claim 14 (depends on 12) The replacement light emitting diode package of claim 12, wherein the illumination device comprises an orifice scope. ### Claim 15 (depends on 12) The replacement light emitting diode package of claim 12, wherein current at a light emitting diode is controlled by the input voltage. ### Claim 16 (depends on 12) The replacement light emitting diode package of claim 12, wherein the illumination device is selected from the group consisting of: a control panel display; a medical device; and a flashlight. ### Claim 17 A medical scope comprising: a voltage source electrically connected to a socket, the socket comprising a voltage pin and a ground pin; a light emitting diode package sized to fit in the socket, the light emitting diode package including: a current control block including a voltage supply connection, a ground connection, a first voltage sense connection, and a second voltage sense connection, the voltage supply connection electrically connected to the voltage pin of the voltage source and the ground connection connected to the ground pin, the current control block configured to maintain a constant voltage across the first and second voltage sense connections; a current sense resistor connected to the first voltage sense connection; a first current adjustment resistor connected between the current sense resistor and the second voltage sense connection; a second current adjustment resistor connected between the second voltage sense connection and the input voltage; and a light emitting diode connected from a point between the current sense resistor and the first current adjustment resistor to the ground, such that adjustment of the input voltage proportionally changes a voltage across the light emitting diode at a constant current. ### Claim 18 (depends on 17) The medical scope of claim 17, wherein current at a light emitting diode is at least partially controlled by the input voltage. ### Claim 19 (depends on 17) The medical scope of claim 17, wherein the current control block comprises a switching controller. ### Claim 20 (depends on 19) The medical scope of claim 19, wherein the light emitting diode package includes a capacitor connected between the first and second voltage sense connections, provide an approximately constant voltage across the first and second voltage sense connections. ### Claim 21 (depends on 17) The medical scope of claim 17, wherein a dimming control is set by a ratio between the first and second current adjustment resistors. ### Claim 22 A drive circuit for a light emitting diode, the drive circuit comprising: an input voltage and a ground; a current control block including a voltage supply connection, a ground connection, a first voltage sense connection, and a second voltage sense connection, the voltage supply connection electrically connected to the input voltage and the ground connection connected to the ground, the current control block configured to maintain a constant voltage across the first and second voltage sense connections; a current sense resistor connected to the first voltage sense connection; a first current adjustment resistor connected between the current sense resistor and the second voltage sense connection; a second current adjustment resistor connected between the second voltage sense connection and the input voltage; and a capacitor connected between the first and second voltage sense connections, the capacitor selected to provide an approximately constant voltage across the first and second voltage sense connections, such that adjustment of the input voltage proportionally changes a voltage across the light emitting diode at a constant current.