# US 2013/0155561 A1 · Over voltage protection circuit and driver circuit using the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0155561 A1 - Document ID: US20130155561A1 - Status: Published application - Kind: A1 - Application number: 13/429,349 - Filed: 2012-03-24 - Published: 2013-06-20 - Earliest claimed: 2011-12-19 - Assignees: Lextar Electronics Corporation - Inventors: Chien-Feng LAI - Web page: https://patentgrep.com/patent/US20130155561A1 ## CPC - H02H 3/202: {for DC systems} - H02H 9/041: {using a short-circuiting device} - H02H 9/042: {comprising means to limit the absorbed power or indicate damaged over-voltage protection device} - H05B 45/395: Linear regulators - H05B 45/54: in a series array of LEDs - Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED] - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) - 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 An over voltage protection circuit, adapted for placing between a power pin of a chip and a power terminal is provided. The over voltage protection circuit includes a voltage detection unit, a current limiting component, and a switch component. The voltage detection unit is coupled between the power terminal and a ground, for outputting a setting voltage according to the voltage level at the power terminal. The current limiting component is coupled between the power terminal and the power pin of the chip. The switch component is coupled between the power pin of the chip and the ground, wherein the switch component is further coupled to the voltage detection unit and controlled by the setting voltage. When the voltage level at the power terminal is higher than a first predetermined value, the switch component conducts to cut off voltage received by the chip. ## Claims ### Claim 1 An over voltage protection circuit, adapted for placing between a power pin of a chip and a power terminal, the over voltage protection circuit comprising: a voltage detection unit, coupled between the power terminal and a ground, for outputting a setting voltage according to a voltage level at the power terminal; a current limiting component, coupled between the power terminal and the power pin of the chip; and a switch component, coupled between the power pin of the chip and the ground, wherein the switch component is further coupled to the voltage detection unit and operates according to the setting voltage; wherein the switch component conducts to cut off voltage being received by the chip, when the voltage level at the power terminal is higher than a first predetermined value. ### Claim 2 (depends on 1) The over voltage protection circuit according to claim 1, wherein the voltage detection unit comprises: a first resistor, coupled between the power terminal and a common terminal; and a second resistor, coupled between the common terminal and the ground; wherein the setting voltage is generated at the common terminal. ### Claim 3 (depends on 2) The over voltage protection circuit according to claim 2, wherein the voltage detection unit further comprises a comparator, having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal is coupled to the common terminal, the second input terminal is coupled to a reference voltage, and the output terminal is for outputting the setting voltage to the switch component. ### Claim 4 (depends on 1) The over voltage protection circuit according to claim 1, wherein the current limiting component is a resistor. ### Claim 5 (depends on 1) The over voltage protection circuit according to claim 1, wherein the switch component is an NMOS transistor, the drain of the NMOS transistor being coupled to the power pin, the source of the NMOS transistor being coupled to the ground, the gate of the NMOS transistor being coupled to the voltage detection unit for receiving the setting voltage. ### Claim 6 (depends on 1) The over voltage protection circuit according to claim 1, wherein the switch component is an NPN transistor, the collector of the NPN transistor being coupled to the power pin, the emitter of the NPN transistor being coupled to the ground, the base of the NPN transistor being coupled to the voltage detection unit for receiving the setting voltage. ### Claim 7 (depends on 1) The over voltage protection circuit according to claim 1, further comprising: a zener diode having an anode coupled to the ground, and a cathode coupled to the power pin of the chip; and a capacitor, coupled between the power pin of the chip and the ground. ### Claim 8 (depends on 1) The over voltage protection circuit according to claim 1, wherein the chip is an off-line linear LED driver IC. ### Claim 9 (depends on 2) The over voltage protection circuit according to claim 2, wherein the power terminal is further coupled to a rectifier circuit, the rectifier circuit rectifying an AC voltage and powering the chip through the power terminal, wherein when the AC voltage is higher than the first predetermined value, the switch component conducts, wherein the first predetermined value is related to the resistance of the first resistor, the resistance of the second resistor, and a threshold voltage of the switch component by the following equation: Vset = ( 1 + R   1 R   2 ) × Vth 2 wherein, Vset represents the first predetermined value; R1 represents the resistance of the first resistor; R2 represents the resistance of the second resistor; Vth represents the threshold voltage of the switch component. ### Claim 10 A driver circuit, adapted for driving a light emitting unit having at least a light emitting diode, a first end of the light emitting unit being coupled to a power terminal, the driver circuit comprising: a chip, coupled to a second end of the light emitting unit, for driving the light emitting unit; and an over voltage protection circuit, coupled between the power terminal and a power pin of the chip, the over voltage protection circuit comprising: a voltage detection unit, coupled between the power terminal and a ground, for outputting a setting voltage according to a voltage level at the power terminal; a current limiting component, coupled between the power terminal and the power pin of the chip; and a switch component, coupled between the power pin of the chip and the ground, wherein the switch component is further coupled to the voltage detection unit and operates according to the setting voltage; wherein the switch component conducts to cut off voltage being received by the chip, when the voltage level at the power terminal is higher than a first predetermined value. ### Claim 11 (depends on 10) The driver circuit according to claim 10, wherein the voltage detection unit comprises: a first resistor, coupled between the power terminal and a common terminal; and a second resistor, coupled between the common terminal and the ground; wherein the setting voltage is generated at the common terminal. ### Claim 12 (depends on 11) The driver circuit according to claim 11, wherein the voltage detection unit further comprises a comparator, having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal is coupled to the common terminal, the second input terminal is coupled to a reference voltage, and the output terminal is for outputting the setting voltage to the switch component. ### Claim 13 (depends on 10) The driver circuit according to claim 10, wherein the current limiting component is a resistor. ### Claim 14 (depends on 10) The driver circuit according to claim 10, further comprising: a rectifier circuit, coupled to the power terminal, for rectifying an AC voltage and powering the chip through the power terminal, wherein when the AC voltage is higher than the first predetermined value, the switch component conducts, wherein the first predetermined value is related to the resistance of the first resistor, the resistance of the second resistor, and a threshold voltage of the switch component by the following equation: Vset = ( 1 + R   1 R   2 ) × Vth 2 wherein, Vset represents the first predetermined value; R1 represents the resistance of the first resistor; R2 represents the resistance of the second resistor; Vth represents the threshold voltage of the switch component.