# US 2019/0356233 A1 · A dc-dc converter and a method for controlling a dc-dc converter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0356233 A1 - Document ID: US20190356233A1 - Status: Published application - Kind: A1 - Application number: 16/414,482 - Filed: 2019-05-16 - Published: 2019-11-21 - Earliest claimed: 2018-05-18 - Assignees: Astec International Limited - Applicants: Astec International Limited - Inventors: Jinying ZHANG; Zhishuo LI; Huihui LU; Yuandong HE; Shoutang CHENG - Web page: https://patentgrep.com/patent/US20190356233A1 ## CPC - H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer} - H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters - H02M 1/36: Means for starting or stopping converters - 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 - 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 A switch-mode DC-DC power converter includes one or more input terminals for receiving an input voltage from a voltage source, one or more output terminals for supplying an output voltage to a load, and a transformer coupled between the input and output terminals. The transformer includes at least one primary winding and at least one secondary winding. The converter also includes a primary switch coupled to control current through the at least one primary winding, a synchronous rectifier coupled to control current through the at least one secondary winding, and means for controlling switching operation of the synchronous rectifier by disabling switching of the synchronous rectifier for a defined time delay in response to receiving an input signal indicative of a startup of the DC-DC power converter, and enabling switching of the synchronous rectifier after the defined time delay has elapsed. ## Claims ### Claim 1 A switch-mode DC-DC power converter, comprising: one or more input terminals for receiving an input voltage from a voltage source; one or more output terminals for supplying an output voltage to a load; a transformer coupled between the input and output terminals, the transformer including at least one primary winding and at least one secondary winding; a primary switch coupled to control current through the at least one primary winding; a synchronous rectifier coupled to control current through the at least one secondary winding; and means for controlling switching operation of the synchronous rectifier by disabling switching of the synchronous rectifier for a defined time delay in response to receiving an input signal indicative of a startup of the DC-DC power converter, and enabling switching of the synchronous rectifier after the defined time delay has elapsed. ### Claim 2 (depends on 1) The DC-DC power converter of claim 1, wherein: the at least one secondary winding of the transformer comprises at least two secondary windings; the synchronous rectifier is coupled to control current through a first one of the at least two secondary windings; and the means for controlling switching operation of the synchronous rectifier includes a pre-bias circuit coupled to receive the input signal from a second one of the at least two secondary windings. ### Claim 3 (depends on 1) The DC-DC power converter of claim 1, wherein the means for controlling switching operation of the synchronous rectifier includes a pre-bias circuit coupled to receive the input signal from the at least one secondary winding. ### Claim 4 (depends on 1) The DC-DC power converter of claim 1, wherein: the transformer comprises at least one auxiliary winding; and the means for controlling switching operation of the synchronous rectifier includes a pre-bias circuit coupled to receive the input signal from the at least one auxiliary winding. ### Claim 5 (depends on 1) The DC-DC power converter of claim 1, further comprising an isolator coupled between a primary side of the transformer and a secondary side of the transformer, wherein: the isolator is coupled to supply a drive signal for the primary switch from the primary side of the transformer to the secondary side of the transformer; the means for controlling switching operation of the synchronous rectifier includes a pre-bias circuit coupled to receive the drive signal from the isolator; and the input signal comprises the drive signal. ### Claim 6 (depends on 1) The DC-DC power converter of claim 1, further comprising an isolator coupled between a primary side of the transformer and a secondary side of the transformer, wherein: the isolator is coupled to supply a converter turn-on signal from the primary side of the transformer to the secondary side of the transformer; the means for controlling switching operation of the synchronous rectifier includes a pre-bias circuit coupled to receive the converter turn-on signal from the isolator; and the input signal comprises the converter turn-on signal. ### Claim 7 A method of controlling a switch-mode DC-DC power converter including a transformer including at least one primary winding and at least one secondary winding, and a synchronous rectifier coupled to control current through the at least one secondary winding, the method comprising: in response to receiving an input signal indicative of a startup of the DC-DC power converter, disabling switching of the synchronous rectifier for a defined time delay; and enabling switching of the synchronous rectifier after the defined time delay has elapsed. ### Claim 8 (depends on 7) The method of claim 7, further comprising: enabling switching operation of the synchronous rectifier for a defined turn-off time delay in response to the input signal transitioning to a logical low level; and disabling switching operating of the synchronous rectifier after the defined turn-off time delay has elapsed. ### Claim 9 (depends on 7) The method of claim 7, wherein: the DC-DC power converter includes a driver circuit coupled to control switching operation of the synchronous rectifier; disabling switching operation of the synchronous rectifier includes disabling the driver circuit; and enabling switching operation of the synchronous rectifier includes enabling the driver circuit. ### Claim 10 (depends on 9) The method of claim 9, further comprising: receiving, at the driver circuit, a pulse width modulated (PWM) control signal; and controlling switching operation of the synchronous rectifier according to the received PWM control signal when the driver circuit is enabled. ### Claim 11 (depends on 7) The method of claim 7, wherein: the DC-DC power converter includes a pre-bias circuit including at least one resistor and at least one capacitor coupled in a resistor-capacitor (RC) circuit; and the defined time delay corresponds to an RC time constant of the RC circuit. ### Claim 12 (depends on 8) The method of claim 8, wherein: the DC-DC power converter includes a pre-bias circuit including at least one resistor and at least one capacitor coupled in a resistor-capacitor (RC) circuit; and the defined turn-off time delay corresponds to an RC time constant of the RC circuit. ### Claim 13 (depends on 7) The method of claim 7, wherein receiving the input signal includes at least one of: receiving the input signal via the at least one secondary winding of the transformer; receiving the input signal via an auxiliary winding of the transformer; and receiving the input signal via an isolator coupled between a primary side of the transformer and a secondary side of the transformer. ### Claim 14 (depends on 7) The method of claim 7, wherein: the DC-DC power converter includes a pre-bias circuit including at least one resistor and at least one capacitor coupled in a resistor-capacitor (RC) circuit, at least one switch and at least one diode coupled between the RC circuit and the switch; receiving the input signal includes receiving the input signal at the pre-bias circuit; and enabling and disabling the synchronous rectifier includes enabling and disabling via the at least one switch of the pre-bias circuit. ### Claim 15 A switch-mode DC-DC power converter, comprising: one or more input terminals for receiving an input voltage from a voltage source; one or more output terminals for supplying an output voltage to a load; a transformer coupled between the input and output terminals, the transformer including at least one primary winding and at least one secondary winding; a primary switch coupled to control current through the at least one primary winding; a synchronous rectifier coupled to control current through the at least one secondary winding; and a control circuit coupled to receive an input signal indicative of active operation of the DC-DC converter from one of the windings of the transformer or an isolator coupled between primary and secondary sides of the transformer, and control switching operation of the synchronous rectifier by enabling switching operation of the synchronous rectifier for a defined time delay in response to the input signal transitioning to a logical low level and disabling switching operating of the synchronous rectifier after the defined time delay has elapsed. ### Claim 16 (depends on 15) The DC-DC power converter of claim 15, wherein the control circuit is coupled to, in response to receiving a startup signal indicative of a startup of the DC-DC power converter, disable switching of the synchronous rectifier for a defined turn-on time delay, and enable switching of the synchronous rectifier after the defined turn-on time delay has elapsed. ### Claim 17 (depends on 15) The DC-DC power converter of claim 15, wherein the control circuit includes: a driver circuit coupled to receive a pulse width modulated (PWM) control signal to control switching operation of the synchronous rectifier according to the received PWM control signal; and a pre-bias circuit coupled to receive the input signal and selectively enable and disable the driver circuit according to the received input signal and the defined time delay. ### Claim 18 (depends on 17) The DC-DC power converter of claim 17, wherein: the pre-bias circuit includes at least one resistor and at least one capacitor coupled in a resistor-capacitor (RC) circuit; and the defined time delay corresponds to an RC time constant of the RC circuit. ### Claim 19 (depends on 16) The DC-DC power converter of claim 16, wherein: the pre-bias circuit includes at least one resistor and at least one capacitor coupled in a resistor-capacitor (RC) circuit; and the defined turn-on time delay corresponds to an RC time constant of the RC circuit. ### Claim 20 (depends on 15) The DC-DC power converter of claim 15, wherein: the at least one secondary winding of the transformer comprises at least two secondary windings; the synchronous rectifier is coupled to control current through a first one of the at least two secondary windings; and the control circuit includes a pre-bias circuit coupled to receive the input signal from a second one of the at least two secondary windings. ### Claim at position 21 -25. (canceled)