# US 9,438,123 B2 · Push-pull LED driver circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,123 B2 - Document ID: US9438123B2 - Status: Granted - Kind: B2 - Application number: 14/854,768 - Filed: 2015-09-15 - Published: 2016-06-30 - Granted: 2016-09-06 - Earliest claimed: 2014-09-22 - Assignees: General Electronics Applications, Inc. - Applicants: Joseph Pernyeszi - Inventors: Joseph Pernyeszi - Web page: https://patentgrep.com/patent/US9438123B2 ## CPC - H05B 45/382: with galvanic isolation between input and output - H02M 3/158: including plural semiconductor devices as final control devices for a single load - H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)} - H02M 3/3372: {of the parallel type} - H02M 3/3376: {with automatic control of output voltage or current} - H05B 45/39: Circuits containing inverter bridges - H02M 1/0058: {by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero (using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826)} - H05B 45/30: Driver circuits - H05B 45/375: using buck topology - H05B 45/385: using flyback topology - Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED] - Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - 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) - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract Push-pull circuits are described that are suitable for the driving of LEDs and that reduce the voltage stress on the switching transistors that is caused by the output transformer. The push-pull arrangement caters to reducing the size of the transformer as it eliminates the DC magnetic bias of the transformer core and it also caters to the integration of the semiconductor content of the circuit requiring only low side DMOS to be implemented in the monolithic, junction isolated process. ## Claims ### Claim 1 A driver circuit connectable to a load, comprising: a DC supply node; first and second switches; a first rectifier; a transformer having first and second primary windings and a secondary winding, wherein the first and second primary windings are respectively connected to ground through the first and second switches and have a center tap connected to the DC supply node, and wherein the secondary winding is connected to the load through the first rectifier when the driver circuit is connected to drive the load; and control circuitry connected to the first and second switches, whereby the first and second switches are alternately conducting when driving the load, wherein, when the driver circuit is connected to drive the load, the load is connected in parallel with the first rectifier and is connected in series with the first and second switches between the DC supply node and ground through the center tap. ### Claim 2 (depends on 1) The driver circuit of claim 1, wherein the center tap is connected to the DC supply node through the load when the driver circuit is connected to drive the load. ### Claim 3 (depends on 1) The driver circuit of claim 1, wherein the first and second switches are connect to ground through the load when the driver circuit is connected to drive the load. ### Claim 4 (depends on 1) The driver circuit of claim 1, wherein the load is one or more LEDs connected in series. ### Claim 5 (depends on 1) The driver circuit of claim 1, wherein, when the driver circuit is driving the load, current through the load is a sum of a current from the secondary winding and a current into the center tap. ### Claim 6 (depends on 1) The driver circuit of claim 1, wherein the first rectifier includes: first and second series connected capacitors having an intermediate node connected to a first terminal of the secondary winding; and first and second series connected diodes having an intermediate node connected to a second terminal of the secondary winding. ### Claim 7 (depends on 6) The driver circuit of claim 6, wherein the first and second series connected diodes are connected to the second terminal of secondary winding through a third capacitor forming a resonant circuit. ### Claim 8 (depends on 1) The driver circuit of claim 1, wherein the first rectifier includes: first and second series connected diodes having an intermediate node connected to a first terminal of the secondary winding; and third and fourth series connected diodes having an intermediate node connected to a second terminal of the secondary winding. ### Claim 9 (depends on 8) The driver circuit of claim 8, further comprising: a capacitor connected in parallel with the first and second series connected diodes and with the third and fourth series connected diodes. ### Claim 10 (depends on 8) The driver circuit of claim 8, wherein the third and fourth series connected diodes are connected to the second terminal of secondary winding through a third capacitor forming a resonant circuit. ### Claim 11 (depends on 1) The driver circuit of claim 1, wherein the driver circuit further includes a second rectifier connected between the DC supply node and ground and connectable to an AC voltage source. ### Claim 12 (depends on 1) The driver circuit of claim 1, wherein the first and second switches are implemented as DMOS transistors. ### Claim 13 (depends on 1) The driver circuit of claim 1, wherein each of the first and second switches is respectively connected to ground in parallel with a corresponding one of a first diode and a second diode. ### Claim 14 (depends on 1) The driver circuit of claim 1, wherein the control circuitry uses a voltage based regulation. ### Claim 15 (depends on 1) The driver circuit of claim 1, wherein the control circuitry uses a current based regulation. ### Claim 16 (depends on 1) The driver circuit of claim 1, wherein the center tap is connected to ground through a capacitor. ### Claim 17 (depends on 1) The driver circuit of claim 1, wherein the control circuitry and first and second switches are formed on a common integrated circuit.