# US 2012/0249012 A1 · Method and system for supplying multiple led drivers using the same traic dimmer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2012/0249012 A1 - Document ID: US20120249012A1 - Status: Published application - Kind: A1 - Application number: 13/075,200 - Filed: 2011-03-30 - Published: 2012-10-04 - Earliest claimed: 2011-03-30 - Assignees: Gre Alpha Electronics Ltd. - Inventors: Abel Xu - Web page: https://patentgrep.com/patent/US20120249012A1 ## CPC - H02M 5/257: using semiconductor devices only - H05B 45/385: using flyback topology - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract An RCD transient absorption circuit, having a first port and a second port, the RCD transient absorption circuit comprising a first resistor, a capacitor and a diode, wherein: the first resistor is connected in parallel to the capacitor, and resultant parallel connection of which is connected in series to a diode; one end of the resultant parallel connection of the first resistor and the capacitor is connected to a cathode of the diode; another end of resultant parallel connection is the first port of the RCD transient absorption circuit; and the second port of the RCD transient absorption circuit is an anode of the diode; the RCD transient absorption circuit further comprises a power-trimming device connected in parallel to the first resistor and the capacitor. ## Claims ### Claim 1 An RCD transient absorption circuit, having a first port and a second port, the RCD transient absorption circuit comprising a first resistor, a capacitor and a diode, wherein: the first resistor is connected in parallel to the capacitor, and resultant parallel connection of which is connected in series to a diode; one end of the resultant parallel connection of the first resistor and the capacitor is connected to a cathode of the diode; another end of resultant parallel connection is the first port of the RCD transient absorption circuit; and the second port of the RCD transient absorption circuit is an anode of the diode; the RCD transient absorption circuit further comprises a power-trimming device connected in parallel to the first resistor and the capacitor. ### Claim 2 (depends on 1) The RCD transient absorption circuit of claim 1, wherein the power-trimming device is a variable resistor. ### Claim 3 (depends on 1) The RCD transient absorption circuit of claim 1, wherein the power-trimming device is formed by a second resistor and a variable resistor connected in series. ### Claim 4 (depends on 2) The RCD transient absorption circuit of claim 2, wherein the variable resistor has a resistance range from a few 10 k ohms to a few 100 k ohms. ### Claim 5 (depends on 3) The RCD transient absorption circuit of claim 3, wherein the second resistor has a resistance value of a few 10 k ohms in order to protect the variable resistor from being mistakenly set to zero ohm. ### Claim 6 (depends on 1) The RCD transient absorption circuit of claim 1, further comprising a TVS connected in parallel to the power-trimming device, wherein the cathode of the TVS is also connected to the cathode of the diode. ### Claim 7 A dimmable LED driver system comprising a dimmer and at least one LED driver, each LED driver comprising: an AC-to-DC converter that matches the characteristics of the dimmer; a transformer for storing energy and for changing the voltage level; an output section for supplying power to LED(s) for lighting; and a PWM controller and a switcher, both of which are used for control of the output power; wherein the dimmable LED driver system is controlled by the dimmer; the at least one LED driver uses an RCD transient absorption circuit; a first port and a second port of the RCD transient absorption circuit connect to a first end and a second end of the primary winding of the transformer respectively; and the first port of the RCD transient absorption circuit connects to an output of the AC-to-DC converter. ### Claim 8 (depends on 7) The dimmable LED driver system of claim 7, wherein the dimmer is a TRIAC dimmer. ### Claim 9 (depends on 8) The dimmable LED driver system of claim 8, wherein the TRIAC dimmer is series connected to the at least one LED driver. ### Claim 10 A method that employs a dimmer to perform the dimming function on a plurality of LED drivers, the method comprising the steps of: installing an RCD transient absorption circuit into each of the plurality of LED drivers, wherein the RCD transient absorption circuit includes a power-trimming device; choosing one LED driver as a reference driver; setting the dimmer to a conduction angle; adjusting the conduction angle such that the reference driver delivers an output current that is 1% within full-load current; measuring output current level of each of the plurality of LED drivers other than the reference driver; and adjusting the power-trimming device of the RCD transient absorption circuit in each of the LED drivers such that the output current is the same as that of the reference driver.