# US 2017/0288556 A1 · Circuits and Methods for Auxiliary Secondary Supply Generation with Self-Starting Primary Side Driver in Isolated Power Converters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0288556 A1 - Document ID: US20170288556A1 - Status: Published application - Kind: A1 - Application number: 15/085,154 - Filed: 2016-03-30 - Published: 2017-10-05 - Earliest claimed: 2016-03-30 - Assignees: Infineon Technologies Austria AG - Applicants: Infineon Technologies Austria AG - Inventors: Benjamim Tang; Darryl Tschirhart; Simone Fabbro; Giuseppe Bernacchia; Alan Huang - Web page: https://patentgrep.com/patent/US20170288556A1 ## CPC - H02M 3/33546: {with automatic control of the output voltage or current (H02M3/33561 takes precedence)} - H02M 1/36: Means for starting or stopping converters - H02M 3/33553: {with galvanic isolation between input and output of both the power stage and the feedback loop} - H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer} - H02M 3/3376: {with automatic control of output voltage or current} - H02M 1/0006: {Arrangements for supplying an adequate voltage to the control circuit of converters} - H02M 1/0045: {Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode} - 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 Circuits that provide an auxiliary power supply on the secondary side of an isolated switched-mode power converter are described. Such an auxiliary supply may be used to provide power to a secondary side controller or to other circuitry in the secondary side of the power converter. During at least a start-up phase of the power converter, the secondary side auxiliary power supply is supplied power by use of a self-starting primary side driver that operates autonomously until the secondary side controller is fully operational. Circuits and methods for such a self-starting primary side driver are provided. The techniques disclosed provide for a secondary side auxiliary power supply that uses minimal additional circuitry. ## Claims ### Claim 1 A switched-mode power converter circuit using an isolated topology for converting power from an input source into power for an output load, the switched-mode power converter circuit comprising: a transformer comprising a primary side winding and one or more secondary side windings; one or more primary side switch devices electrically connected to the primary side winding; a secondary side controller circuit coupled to one or more of the secondary side windings and configured to control switching of the one or more primary side switch devices during a steady-state operating phase in which the secondary side controller circuit is fully powered and operational; a primary side startup circuit configured to control switching of the one or more primary side switch devices during a startup operating phase in which the secondary side controller circuit is not controlling the switching of the one or more primary side switch devices, so as to energize the primary side winding during the startup operating phase; and a secondary side auxiliary power supply circuit galvanically isolated from the primary side winding and configured to supply power to the secondary side controller circuit based on energy transferred from the primary side winding during the startup operating phase. ### Claim 2 (depends on 1) The switched-mode power converter circuit of claim 1, further comprising: a primary side determining circuit configured to determine whether the switched-mode power converter is operating in the steady-state operating phase by sensing activity on control signals that are generated by the secondary side controller circuit to control switching of the one or more primary side switch devices. ### Claim 3 (depends on 1) The switched-mode power converter circuit of claim 1, further comprising: a primary side detection circuit configured to detect whether a voltage level of the input source is higher than a threshold, wherein the primary side startup circuit is further configured to begin generation of startup control signals that control switching of the one or more primary side switch devices in response to the primary side detection circuit detecting that the voltage level is higher than the threshold. ### Claim 4 (depends on 1) The switched-mode power converter circuit of claim 1, wherein the one or more primary side switch devices are controlled by control signals that are pulse-width modulated (PWM) waveforms, each of which is characterized by at least a frequency and a duty cycle. ### Claim 5 (depends on 4) The switched-mode power converter circuit of claim 4, wherein the secondary side controller circuit is further configured to generate the frequency and duty cycle for each of the PWM waveforms based upon a voltage sense signal input to the secondary side controller, the voltage sense signal being based upon the voltage at the output load of the switched-mode power converter. ### Claim 6 (depends on 1) The switched-mode power converter circuit of claim 1, further comprising: one or more secondary side switch devices configured to rectify a voltage provided to the output load of the switched-mode power converter circuit, wherein the secondary side controller circuit is further configured to output rectification control signals that control the one or more secondary side switch devices. ### Claim 7 (depends on 6) The switched-mode power converter circuit of claim 6, wherein the secondary side auxiliary power supply circuit is further configured to supply power to one or more rectification driver circuits, wherein each of the rectification driver circuits has an output controlling one of the secondary side switches, and an input controlled by one of the output rectification control signals. ### Claim 8 (depends on 1) The switched-mode power converter circuit of claim 1, wherein the transformer comprises two or more secondary side windings including an auxiliary winding, and where the secondary side auxiliary power supply circuit is coupled to the auxiliary winding and the output load is coupled to one or more of the secondary windings that are distinct from the auxiliary winding. ### Claim 9 (depends on 8) The switched-mode power converter circuit of claim 8, wherein the secondary side auxiliary power supply circuit is further configured to switch from being provided input power from the auxiliary winding during the startup operating phase to being provided power by one or more of the secondary side windings that are coupled to the output load during the steady-state operating phase. ### Claim 10 (depends on 1) The switched-mode power converter circuit of claim 1, wherein the power input for the secondary side auxiliary power supply circuit is supplied by the secondary winding, and wherein the secondary winding also supplies power to the output load. ### Claim 11 (depends on 1) The switched-mode power converter circuit of claim 1, further comprising: a control signal isolation circuit that inputs control signals from the secondary side controller circuit, and that outputs control signals that are used to control the one or more primary side switch devices. ### Claim 12 (depends on 1) The switched-mode power converter circuit of claim 1, wherein the switched mode power converter circuit is configured in one of a half-bridge topology, a full-bridge topology, an active clamp forward topology, and a push-pull topology. ### Claim 13 A primary side driver circuit in a switched-mode power converter using an isolated topology, the primary side driver circuit configured to generate switch control signals provided to control terminals of one or more primary side switch devices in order to energize a primary side winding of a transformer, the primary side driver circuit comprising: input terminals configured for inputting external control signals from a secondary side of the switched-mode power converter; a startup circuit configured to generate startup control signals that control switching of the one or more primary side switch devices during a startup operating phase; and a selection circuit configured to provide the switch control signals based upon the generated startup control signals during the startup operating phase, and based upon the external control signals during a steady-state operating phase. ### Claim 14 (depends on 13) The primary side driver circuit of claim 13, further comprising: a determining circuit configured to determine whether the switched-mode power converter is operating in the steady-state operating phase by sensing activity on the external control signals. ### Claim 15 (depends on 14) The primary side driver circuit of claim 14, wherein sensing activity on the external control signals is performed by detecting that there has been no change in the state of the external control signals for a predetermined period of time. ### Claim 16 (depends on 13) The primary side driver circuit of claim 13, further comprising: a detection circuit configured to detect whether a voltage level of an input source supplying the primary side of the transformer is higher than a threshold, wherein the startup circuit is further configured to begin generation of the startup control signals in response to the detection circuit detecting that the voltage level is higher than the threshold. ### Claim 17 (depends on 13) The primary side driver circuit of claim 13, wherein the startup control signals are pulse width modulated (PWM) waveforms, each of which has a frequency and a duty cycle. ### Claim 18 (depends on 17) The primary side driver circuit of claim 17, wherein the frequency and duty cycle of the PWM waveforms are determined by a default configuration stored in the primary side driver circuit. ### Claim 19 (depends on 17) The primary side driver circuit of claim 17, wherein the frequency and duty cycle are controlled by input configuration terminals. ### Claim 20 (depends on 13) The primary side driver circuit of claim 13, wherein the startup circuit comprises an oscillator circuit. ### Claim 21 A method, in a primary side driver circuit of a switched-mode power converter using an isolated topology, for generating switch control signals that are provided to control terminals of one or more primary side switch devices in order to energize a primary winding of a transformer of the switched-mode power converter, the method comprising: monitoring external control signals from a secondary side of the switched-mode power converter; generating startup control signals that control switching of the one or more primary side switch devices, the startup control signals being based upon default parameters; detecting whether the switched-mode power converter is operating in a startup operating phase; and responsive to detecting that the switched-mode power converter is operating in the startup operating phase, providing the switch control signals to the one or more primary side switch devices based upon the generated startup control signals. ### Claim 22 (depends on 21) The method of claim 21, wherein detecting whether the switched-mode power converter is operating in the startup operating phase is performed by sensing that there has been no change in the state of the monitored external control signals for a predetermined period of time. ### Claim 23 (depends on 22) The method of claim 22, wherein detecting that there has been a change in the state of the monitored external control signals within the predetermined period of time indicates that the switched-mode power converter is not operating in the startup operating phase and, responsive to such detection, disabling the generation of startup control signals based upon the default parameters. ### Claim 24 (depends on 21) The method of claim 21, further comprising: detecting whether a voltage level of an input source supplying the primary winding is higher than a threshold, wherein generation of the startup control signals begins responsive to detecting that the voltage level is higher than the threshold. ### Claim 25 (depends on 21) The method of claim 21, wherein the default parameters are hard-wired within the primary side driver circuit. ### Claim 26 (depends on 21) The method of claim 21, wherein the default parameters are determined based upon inputs provided to input configuration terminals of the primary side driver circuit. ### Claim 27 (depends on 21) The method of claim 21, wherein the switch control signals are pulse-width modulated (PWM) waveforms having a frequency and a duty cycle.