# US 2018/0324925 A1 · Detection circuit and led tube including the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0324925 A1 - Document ID: US20180324925A1 - Status: Published application - Kind: A1 - Application number: 15/683,501 - Filed: 2017-08-22 - Published: 2018-11-08 - Earliest claimed: 2017-05-04 - Assignees: Philips Lighting Holding B.V. - Applicants: Philips Lighting Holding B.V. - Inventors: Han LU; Jingxu ZHOU; DeYong KONG - Web page: https://patentgrep.com/patent/US20180324925A1 ## CPC - H05B 45/50: responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits - H05B 45/30: Driver circuits - H05B 47/26: Circuit arrangements for protecting against earth faults - F21Y 2103/10: comprising a linear array of point-like light-generating elements - F21Y 2115/10: Light-emitting diodes [LED] - H05B 45/36: Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI] - 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 - F21Y: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract Embodiments of the present disclosure involve a detection circuit for a tube and a tube including the detection circuit. The detection circuit comprises: impedance connected between two ends of a tube; a voltage detector configured to detect voltage on the impedance; a voltage threshold circuit configured to provide a voltage threshold; a first control circuit configured to compare voltage across the two ends of the tube to the voltage threshold, and to control the voltage detector to detect only when the voltage across the two ends of the tube is smaller than the voltage threshold. By using the detection circuit of the present disclosure, it can detect whether a human body contacts the tube under protection state, to avoid of the risk of getting an electrical shock. ## Claims ### Claim 1 A voltage detection circuit, comprising: an impedance coupled between inputs of an LED tube; a voltage detector configured to detect a voltage across the impedance; a voltage threshold circuit configured to provide a threshold voltage; a first control circuit configured to compare an input voltage across the inputs of the tube to the threshold voltage, and to control the voltage detector to detect the voltage across the impedance when the input voltage is less than the threshold voltage. ### Claim 2 (depends on 1) The detection circuit according to claim 1, wherein the threshold voltage is not greater than 30 volts. ### Claim 3 (depends on 1) The detection circuit according to claim 1, further comprising a second control circuit configured to enable the voltage detector when the voltage threshold circuit is charged to a starting voltage. ### Claim 4 (depends on 3) The detection circuit according to claim 3, wherein the first control circuit is configured to compare the input voltage with the starting voltage that acts as the threshold voltage, and to control the voltage detector to detect the voltage across the impedance when the input voltage is less than the starting voltage, wherein the first control circuit is adapted to decouple the impedance from the inputs before the detection and to couple the impedance between the input during the detection. ### Claim 5 (depends on 3) The detection circuit according to claim 3, wherein the voltage threshold circuit comprises a first capacitor and the detection circuit comprises: a first charging loop configured to charge the first capacitor to reach the starting voltage; and the first control circuit further comprises a transistor adapted to connect the impedance between the input voltage and a power ground, and the transistor is adapted to be turned on to begin the detection and is adapted to be turned off when not detection. ### Claim 6 (depends on 5) The detection circuit according to claim 5, wherein the first charging loop is configured to set a time required for an initial charge of the first capacitor to reach the starting voltage as: from 90 milliseconds when the input voltage is 230 volts; to 260 milliseconds when the input voltage is 90 volts. ### Claim 7 (depends on 6) The detection circuit according to claim 6, wherein the detection circuit comprises a first discharging loop configured to discharge the first capacitor when the voltage detector starts detection. ### Claim 8 (depends on 7) The detection circuit according to claim 7, wherein the first discharging loop is configured to set the time for discharging the first capacitor to be less than the starting voltage as less than 1 millisecond, and the first charging loop is configured to set the time range required for recharging the discharged first capacitor to reach the starting voltage as: from 50 milliseconds when the input voltage is 230 volts; to 200 milliseconds when the input voltage is 90 volts. ### Claim 9 (depends on 1) The detection circuit according to claim 1, further comprising a timing circuit configured to enable the voltage threshold circuit and the first control circuit before timing expires, and to disable the voltage threshold circuit and the first control circuit when timing is expired. ### Claim 10 (depends on 9) The detection circuit according to claim 9, wherein the timing circuit comprises a second capacitor, a second charging loop configured to charge the second capacitor, and a voltage limit element, wherein the timing circuit is configured to enable the voltage threshold circuit and the first control circuit when the voltage of the second capacitor is lower than a threshold of the voltage limit element. ### Claim 11 (depends on 10) The detection circuit according to claim 10, wherein the timing ranges: from 275 milliseconds when the input voltage is 230 volts; to 800 milliseconds when the input voltage is 90 volts. ### Claim 12 (depends on 10) The detection circuit according to claim 10, wherein the timing circuit further comprises a second discharging loop configured to discharge the second capacitor when the circuit is not connected to the input voltage. ### Claim 13 (depends on 1) The detection circuit according to claim 1, wherein the voltage detector is configured to detect the voltage across the impedance to determine whether a further impedance, apart from the LED tube, is linked to the impedance connected across the inputs of the LED tube; whereby, when the voltage is greater than a first threshold, the voltage detector determines the absence of the further impedance apart from the LED tube; and whereby, when the voltage is less than the first threshold, the voltage detector determines the presence of the further impedance apart from the LED tube. ### Claim 14 (depends on 1) The detection circuit according to claim 1, further comprising a rectifier bridge, wherein the voltage threshold circuit, the first control circuit and the impedance are configured to: connect to an output of the rectifier bridge to receive an input voltage of full-wave rectification; or connect to an input of the rectifier bridge to receive an input voltage of half-wave rectification. ### Claim 15 (depends on 1) The detection circuit according to claim 1, at least partially implemented in an integrated circuit. ### Claim 16 (depends on 1) An LED tube, comprising the detection circuit for the tube in claim 1, wherein the LED tube is connected to a mains supply; the LED tube further comprising an LED light source and an LED driving circuit for driving the LED light source, wherein the detection circuit initiates the LED driving circuit when the voltage across the impedance is detected to be greater than the first threshold. ### Claim 17 (depends on 16) The LED tube according to claim 16, wherein the LED light source and the LED driving circuit are in a series connection, and the series connection is in parallel with the detection circuit, especially in parallel with the impedance of the detection circuit.