# US 8,786,195 B2 · Automatic method to detect short and open conditions on the outputs of a LED driver device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,786,195 B2 - Document ID: US8786195B2 - Status: Granted - Kind: B2 - Application number: 13/047,299 - Filed: 2011-03-14 - Published: 2011-09-29 - Granted: 2014-07-22 - Earliest claimed: 2010-03-23 - Assignees: STMicroelectronics S.r.l. - Applicants: Sergio Castiglia; Roberto La Rosa - Inventors: Sergio Castiglia; Roberto La Rosa - Web page: https://patentgrep.com/patent/US8786195B2 ## CPC - H05B 45/50: responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract Driving a light-emitting element by a driver capable of testing at least an open or short condition of the light-emitting element. In particular, a driving signal is generated to drive the light-emitting element. It is evaluated based on the value of the driving signal whether a predetermined condition is reached. If so, a latch signal is output indicating that the testing has finished. ## Claims ### Claim 1 A driving apparatus for driving a light emitting element, the driving apparatus comprising: a driving means for outputting a driving signal for driving a light emitting element, a testing means for testing the light emitting element by measuring the driving signal, and an evaluating means for determining that the value of the driving signal reaches a predetermined condition, and for outputting a latch signal, indicating that testing is completed, at a time when the value of the driving signal reaches the predetermined condition. ### Claim 2 (depends on 1) The driving apparatus according to claim 1, wherein the driving means is configured to start driving the light emitting element upon change of level of an output enable signal input to the driving means. ### Claim 3 (depends on 2) The driving apparatus according to claim 2, wherein the output enable signal is a logic signal and the driving means is configured to start driving the light emitting element upon setting the output enable signal to low level. ### Claim 4 (depends on 2) The driving apparatus according to claim 2 further comprising a turn-off logic means for turning off the light emitting element upon change of the level of the output enable signal. ### Claim 5 (depends on 4) The driving apparatus of claim 4, wherein the turn-off logic includes an AND logic gate, the two inputs of the AND logic gate being the output enable signal and the latch signal, and the output of the AND logic gate is a signal controlling turning off the driving of the light emitting element. ### Claim 6 (depends on 1) The driving apparatus according to claim 1 wherein the latch signal is a logic signal. ### Claim 7 (depends on 1) The driving apparatus according to claim 1 further comprising a turn-off logic means for turning off the light emitting element when the evaluating means outputs the latch signal indicating that testing is completed. ### Claim 8 (depends on 1) The driving apparatus according to claim 1 wherein the latch signal is a pulse of a predetermined height and length. ### Claim 9 (depends on 1) The driving apparatus according to claim 1 wherein the light emitting element is at least one LED. ### Claim 10 (depends on 1) The driving apparatus according to claim 1 wherein the evaluating means includes a comparator configured to compare the driving signal with a predetermined value and to determine that the predetermined condition is reached if the value of the driving signal is equal to and/or greater than the predetermined value. ### Claim 11 (depends on 1) The driving apparatus according to claim 1 wherein the testing means is configured, based on a measurement of current or voltage of the driving signal, to detect an open or a short circuit. ### Claim 12 (depends on 1) An integrated circuit implementing the driving apparatus according to claim 1. ### Claim 13 A driving method for driving a light emitting element, the driving method comprising: driving, with a driving means, a light emitting element by outputting a driving signal, testing, with a testing means, the light emitting element by measuring the driving signal, determining, with an evaluating means, that the value of the driving signal reaches a predetermined condition, and outputting, with the evaluating means, a latch signal, indicating that testing is completed, at a time when the value of the driving signal reaches the predetermined condition. ### Claim 14 (depends on 13) The driving method according to claim 13, wherein driving of the light emitting element is initiated upon change of level of an output enable signal input to the driving means. ### Claim 15 (depends on 14) The driving method according to claim 14, wherein the output enable signal is a logic signal and driving is initiated upon setting the output enable signal to low level. ### Claim 16 (depends on 13) The driving method according to claim 13 further comprising a driving to an OFF state the light emitting element upon outputting the latch signal indicating that testing is completed. ### Claim 17 (depends on 13) The driving method according to claim 13 further comprising driving to an OFF state the light emitting element upon change of the level of the output enable signal. ### Claim 18 (depends on 13) The driving method according to claim 13 wherein the latch signal is a logic signal. ### Claim 19 (depends on 18) The driving method according to claim 18 wherein the latch signal is a pulse of a predetermined height and length. ### Claim 20 (depends on 13) The driving method according to claim 13 wherein the light emitting element is at least one LED. ### Claim 21 (depends on 13) The driving method according to claim 13 wherein determining includes comparing the driving signal with a predetermined value and determining that the predetermined condition is reached if the value of the driving signal is equal to and/or greater than the predetermined value. ### Claim 22 (depends on 13) The driving method according to claim 13 wherein testing includes, based on a measurement of current or voltage of the driving signal, detecting an open or a short circuit. ### Claim 23 (depends on 13) A computer program product comprising a computer readable medium having a computer readable program code embodied thereon, the program code being adapted to carry out the method according to claim 13. ### Claim 24 A driver for a light-emitting element, comprising: a driver circuit configured to output a driving signal for driving a light-emitting element; a test circuit configured to test the light-emitting element by measuring the driving signal; and an evaluation circuit configured to determine that a value of the driving signal meets a predetermined condition, and to provide a latch signal at a time when the value of the driving signal meets the predetermined condition. ### Claim 25 (depends on 24) A driver for a light-emitting element as defined in claim 24, wherein the evaluation circuit comprises a comparator configured to compare the driving signal with a reference value and to provide the latch signal in response to the driving signal exceeding the reference value. ### Claim 26 (depends on 24) A driver for a light-emitting element as defined in claim 24, wherein the driver circuit includes turn-off logic configured to turn off the light-emitting element when the evaluation circuit provides the latch signal. ### Claim 27 (depends on 24) A driver for a light-emitting element as defined in claim 24, wherein an active state of the latch signal indicates that testing is completed. ### Claim 28 (depends on 24) A driver for a light-emitting element as defined in claim 24, wherein the driving signal is turned on by the driver circuit in response to a transition of an output enable signal to an active state and is turned off in response to a transition of the latch signal to an active state. ### Claim 29 (depends on 24) A driver for a light-emitting element as defined in claim 24, wherein the driving signal is turned on by the driver circuit in response to a transition of an output enable signal to an active state and is turned off in response to a transition of the output enable signal to an inactive state. ### Claim 30 (depends on 24) A driver for driving a light-emitting element as defined in claim 24, wherein the test circuit is configured to detect an open or a short circuit condition of the light-emitting element. ### Claim 31 A method for driving a light-emitting element, comprising: supplying, by a driver circuit, a driving signal for driving a light-emitting element; testing, by a test circuit, the light-emitting element by measuring the driving signal; and determining, by an evaluation circuit, that a value of the driving signal meets a predetermined condition and providing a latch signal at a time when the value of the driving signal meets the predetermined condition. ### Claim 32 (depends on 31) A method for driving a light-emitting element as defined in claim 31, wherein determining and providing comprise comparing the driving signal with a reference value and providing the latch signal in response to the driving signal exceeding the reference value. ### Claim 33 (depends on 31) A method for driving a light-emitting element as defined in claim 31, wherein supplying the driving signal includes turning off the light-emitting element in response to providing the latch signal. ### Claim 34 (depends on 31) A method for driving a light-emitting element as defined in claim 31, wherein supplying the driving signal comprises turning on the driving signal in response to a transition of an output enable signal to an active state and turning off the driving signal in response to a transition of the latch signal to an active state. ### Claim 35 (depends on 31) A method for driving a light-emitting element as defined in claim 31, wherein supplying the driving signal comprises turning on the driving signal in response to a transition of an output enable signal to an active state and turning off the driving signal in response to a transition of the output enable signal to an inactive state.