An auxiliary converter provides operating power for the controller

Abstract

An auxiliary converter coupled to an output of a main power converter includes an auxiliary switch, a timing circuit, and an energy transfer element. The auxiliary switch is coupled to the output of the main power converter. The timing circuit is coupled to receive a control signal from a controller of the main power converter, wherein the controller regulates the output of the main power converter, the timing circuit is configured to output an auxiliary drive signal to control switching of the auxiliary switch in response to the control signal. The energy transfer element is coupled to the auxiliary switch, wherein the energy transfer element is configured to transfer energy from the output of the main power converter to a power supply of the controller, the power supply provides operating power for the controller of the main power converter.

Description

[0001] This application claims the benefit of currently pending U.S. Provisional Application No. 62 / 954,807, filed December 30, 2019, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates generally to power converters, and more particularly, to controllers for power converters. BACKGROUND

[0003] Electronic devices operate using electrical power. Because of their high efficiency, small size, and light weight, switched mode power converters are commonly used to power many electronic devices today. Conventional wall outlets provide high voltage alternating current (ac) power. In a switched power converter, the high voltage ac input is converted by an energy transfer element to provide a well-regulated direct current (dc) output. Switched mode power converter controllers typically provide output regulation by sensing one or more signals representative of one or more output quantities and controlling the output in a closed loop. In operation, switches are utilized to provide a desired output by varying the duty cycle (typically the ratio of the on time of the switch to the total switching period), varying the switching frequency, or varying the number of pulses per unit time of the switches in the switched mode power converter.

[0004] Power converters typically include one or more controllers that sense and regulate the output of the power converter. These controllers typically require a regulated or unregulated voltage source to power the circuit components of the controller. A bypass capacitor coupled to the controller can provide operating power to the circuit of the controller. BRIEF DESCRIPTION OF DRAWINGS

[0005] Non-limiting and non-exhaustive embodiments of the present application are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views.

[0006] Figure 1 is a schematic diagram of an example isolated power converter including an auxiliary converter according to embodiments of the present disclosure.

[0007] Figure 2A is a schematic diagram of an example auxiliary converter according to embodiments of the present disclosure. Figure 1

[0008] Figure 2B is a timing diagram illustrating example waveforms of the auxiliary converter of Figure 2A

[0009] Figure 3 is a schematic diagram of an example auxiliary converter according to embodiments of the present disclosure.​​Figure 1 schematic diagram of another example auxiliary converter of

[0010] Figure 4 is another example auxiliary converter according to embodiments of the present disclosure Figure 1 schematic diagram of yet another example auxiliary converter of

[0011] Figure 5 is another example auxiliary converter according to embodiments of the present disclosure Figure 1 schematic diagram of still another example auxiliary converter of

[0012] Figure 6 is another example isolated power converter including an auxiliary converter according to embodiments of the present disclosure

[0013] Figure 7 is another example auxiliary converter according to embodiments of the present disclosure Figure 1 schematic diagram of an example auxiliary converter of

[0014] Figure 8 is another example auxiliary converter according to embodiments of the present disclosure Figure 1

[0015] In all of the several views of the drawings, corresponding reference characters indicate corresponding parts throughout the several views. The skilled artisan will understand that the elements in the drawings are illustrated for simplicity and clarity and that the actual implementation can not be drawn to scale. For example, the dimensions of some of the elements in the drawings can be exaggerated relative to other elements to help improve the understanding of the present embodiments of the application. Also, common but well-understood elements that are useful not only for the state of the art but also for the advancement to the art have generally not been depicted in order to avoid obscuring aspects of the present embodiments of the application. DETAILED DESCRIPTION

[0016] In the following description, numerous specific details are set forth to provide a thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present application can be practiced without requiring these specific details. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring aspects of the present application.

[0017] ​References throughout this specification to "one embodiment", "an embodiment", "one example" or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" or "in an embodiment" or "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics can be combined in any suitable

[0018] Power converters often include one or more controllers that sense and regulate the output of the power converter. These controllers often require a regulated or unregulated voltage source to power the circuit components of the controller. A bypass capacitor coupled to the controller can provide run power to the circuit of the controller.

[0019] Isolated power converters can include a primary controller and a secondary controller that are galvanically isolated from each other by an energy transfer element (e.g., a coupled inductor, a transformer, etc.). In other words, a dc voltage applied between an input side and an output side of the power converter will produce substantially zero current.

[0020] The primary controller is configured to control a power switch on a primary side of the isolated power converter to control the transfer of energy from a primary winding of the energy transfer element to a secondary winding of the energy transfer element. The secondary controller is coupled to circuit components on a secondary side of the isolated power converter. The secondary controller can also be configured to control a secondary switch coupled to the secondary winding of the energy transfer element, such as a transistor used as a synchronous rectifier for the power converter. Although the primary controller and the secondary controller are galvanically isolated from each other, the secondary controller can transmit signals to the primary controller that control how the primary controller switches the power switch to transfer energy to the secondary side.

[0021] The secondary side of the isolated power converter includes a bypass capacitor that provides run power to the circuit of the secondary controller. The secondary controller is coupled to the bypass capacitor and typically includes a linear regulator to regulate a bypass voltage across the bypass capacitor to a sufficient level to run the circuit of the secondary controller. For example, the bypass voltage can be regulated to substantially 4.4 volts (V).

[0022] Typically, the source to charge the bypass capacitor can be significantly higher than the operating level for the bypass voltage. Additionally, the source can also be quite variable. For example, the output voltage of a power converter can be utilized to charge the bypass capacitor to a sufficient level for the secondary controller to operate. However, for some applications, the output voltage of the power converter can be between 20V-30V, and at times can reach levels above 40V. A charge pump and a linear regulator can be utilized to charge the bypass capacitor from a high voltage source, such as the output voltage, to a much lower bypass voltage. However, utilizing circuits such as charge pumps and linear regulators can result in excessive dissipation and increased heat, which can adversely affect the efficiency of the power converter.

[0023] Embodiments of the present disclosure utilize an auxiliary converter, such as a buck converter, to obtain a low voltage supply from a higher voltage rail of a primary power converter to provide operating power for a controller of the primary power converter. Additionally, the higher voltage rail of the primary power converter is also generated by the primary power converter. For example, the auxiliary converter can obtain a lower bypass voltage for a bypass capacitor of a secondary controller from a higher voltage rail, such as an output voltage of the primary power converter. In another embodiment, the auxiliary converter can obtain a lower bypass voltage for a bypass capacitor of a primary controller from a voltage of a bias winding of an energy transfer element of the primary power converter. For both embodiments, the output voltage and the bias winding voltage are generated by the primary power converter during operation of the primary power converter. In an embodiment, the auxiliary converter includes a timing circuit, a switch, and an energy transfer element configured to obtain the low voltage supply from the higher voltage rail. Additionally, a drive signal to control the switch of the auxiliary converter can be sourced from a controller of the power converter, such as a controller on an output side of the power converter (e.g., a secondary controller) or a controller on an input side of the power converter (e.g., a primary controller). In yet other embodiments, the auxiliary converter can be an open loop converter, and the operating frequency of the auxiliary converter is responsive to the operating frequency of the primary power converter.

[0024] In an embodiment, the timing circuit can generate an auxiliary drive signal to turn on and turn off the switch of the auxiliary converter. In one embodiment, the timing circuit generates the auxiliary drive signal in response to a secondary drive signal to control a synchronous rectifier of the power converter. The timing circuit can include a resistor and a capacitor, which is commonly referred to as a resistor-capacitor (RC) circuit, and an RC time constant of the RC circuit determines a conduction time of the switch of the auxiliary converter. As such, the auxiliary drive signal can obtain the low voltage supply from the higher voltage rail of the primary power converter to provide operating power for the controller of the primary power converter.

[0025] Figure 1An example primary power converter 100 according to an embodiment of the present disclosure is illustrated that includes an auxiliary converter 140 to obtain a bypass voltage VBP 131 for a bypass capacitor 133 that provides power to a second controller 126 (e.g., a secondary controller) of the primary power converter 100. The illustrated primary power converter 100 includes a clamp circuit 104, an energy transfer element Tl 106, an input winding 108 of the energy transfer element Tl 106, an output winding 110 of the energy transfer element Tl 106, a power switch S1 112, an input return 111, an output rectifier S2 114, an output capacitor CO 115, an output sense circuit 121, the second controller 126, a first controller 124, the bypass capacitor 133 (e.g., a power supply capacitor for the second controller 126), and the auxiliary converter 140. The auxiliary converter 140 is shown to include a timing circuit 142, an auxiliary power switch S3 144, an energy transfer element L2 146, and diodes Dl 148 and D2 150. A communication link 135 between the second controller 126 and the first controller 124 is also illustrated.

[0026] Figure 1 The input voltage V IN 102, the output voltage VOUT 116, the output current I O 117, the output quantity UO 119, the feedback signal FB 122, the bypass voltage VBP 131, the request signal REQ 132, the current sense signal ISNS 129, the power switch voltage V D 137, the power switch current I D 139, the primary drive signal DR 136, the secondary drive signal 128, the auxiliary drive signal ADR 143, the energy transfer element current IL2 145, the auxiliary voltage VL2 147, and the auxiliary switch current IS3 149.

[0027] In the illustrated embodiment, the primary power converter 100 is shown to have a flyback topology. Additionally, the input of the primary power converter 100 is galvanically isolated from the output current of the primary power converter 100, such that the input return 111 is galvanically isolated from the output return 118. Because the input and output of the primary power converter 100 are galvanically isolated, there is no direct current (dc) path across the isolation barrier of the energy transfer element Tl 106, or between the input winding 108 and the output winding 110, or between the input return 111 and the output return 118. It should be understood that other known power converter topologies and configurations can also benefit from the teachings of the present disclosure.

[0028] The primary power converter 100 receives an unregulated input V IN102 provides output power to a load 120. In one embodiment, the input V IN 102 is a rectified and filtered ac line voltage. In another embodiment, the input voltage V IN 102 is a dc input voltage. The input V IN 102 is coupled to an energy transfer element 106. In some embodiments, the energy transfer element 106 can be a coupled inductor, transformer, or inductor. An example energy transfer element 106 is shown to include two windings: an input winding 108 (also referred to as a primary winding) and an output winding 110 (also referred to as a secondary winding). However, the energy transfer element 106 can have more than two windings. The input winding 108 of the energy transfer element is further coupled to a power switch SI 112, and the power switch SI 112 is further coupled to an input return 111. The voltage at the drain of the power switch SI 112 is denoted as the power switch voltage V D 139. The clamp circuit 104 is coupled across the input winding 108. The clamp circuit 104 limits the maximum voltage across the power switch SI 112. Additionally, when the clamp circuit 104 includes active circuit components (such as a switch), the clamp circuit 104 can facilitate zero voltage switching of the power switch SI 112.

[0029] The output winding 110 is coupled to an output rectifier S2 114, which is shown as a transistor used as a synchronous rectifier. However, the output rectifier S2 114 can also be a diode. An output capacitor CO 115 is shown coupled to the output rectifier S2 114 and an output return 118. The main power converter 100 also includes circuitry to regulate an output quantity UO 119, which in one embodiment can be an output voltage V OUT 116, an output current I O 117, or a combination of both. An output sense circuit 121 is configured to sense the output quantity UO 119 to provide a feedback signal FB 122 representing the output of the main power converter 100 to a second controller 126.

[0030] The second controller 126 is configured to output a secondary drive signal SR 128 and a request signal REQ 132 in response to the feedback signal FB 122. The secondary drive signal SR 128 is received by the output rectifier S2 114 and controls the turn-on and turn-off of the output rectifier S2 114. In one embodiment, the secondary drive signal SR 128 is a rectangular pulse waveform having varying lengths of logic high and logic low segments. The logic high segments can correspond to the output rectifier S2 114 being on, while the logic low segments correspond to the output rectifier S2 114 being off. Additionally, the period of the secondary drive signal SR 128 (e.g., the duration between successive leading or trailing edges in the secondary drive signal SR 128) can be referred to as a switching period TSW that represents the operating period (or frequency) of the primary power converter. In one embodiment, the secondary drive signal SR 128 and the primary drive signal DR 136 have substantially the same switching period.

[0031] The request signal REQ 132 represents a request to turn on the power switch SI 112. The request signal REQ 132 can include a request event 199 that is generated in response to the feedback signal FB 122. In one embodiment, the second controller 126 is configured to compare the feedback signal FB 122 to a regulation reference. In response to the comparison, the second controller 126 can output a request event 199 in the request signal REQ 132. The request signal REQ 132 can be a rectangular pulse waveform that jumps to a logic high value and quickly returns to a logic low value. The logic high pulse can be referred to as a request event 199. In other embodiments, it is understood that the request signal REQ 132 can be an analog continuously varying signal, rather than a pulse waveform, while still benefiting from the teachings of the present disclosure.

[0032] The first controller 124 is coupled to receive a signal representing the switching current ISI 110 of the power switch SI 112. The first controller 124 is also coupled to receive a signal representing the output voltage VOUT 116. The first controller 124 is configured to output a primary drive signal DR 136 in response to the feedback signal FB 122. The primary drive signal DR 136 is received by the power switch SI 112 and controls the turn-on and turn-off of the power switch SI 112. In one embodiment, the primary drive signal DR 136 is a rectangular pulse waveform having varying lengths of logic high and logic low segments. The logic high segments can correspond to the power switch SI 112 being on, while the logic low segments correspond to the power switch SI 112 being off. Additionally, the period of the primary drive signal DR 136 (e.g., the duration between successive leading or trailing edges in the primary drive signal DR 136) can be referred to as a switching period TSW that represents the operating period (or frequency) of the primary power converter. In one embodiment, the primary drive signal DR 136 and the secondary drive signal SR 128 have substantially the same switching period. DThe current sense signal ISNS 129 of 137 and the request signal REQ 132 over the communication link 135 shown as a dashed line, and outputs a primary drive signal DR 136. The first controller 124 provides the primary drive signal DR 136 to the power switch SI 112 to control various switching parameters of the power switch SI 112 to control the transfer of energy from the input to the output of the primary power converter 100 through the energy transfer element 106. Examples of such parameters include the switching frequency (or switching period TSW), the duty cycle, the on-time, and the off-time, or varying the number of pulses per unit of time of the power switch SI 112. In addition, the power switch SI 112 can be controlled such that it has a fixed switching frequency or a variable switching frequency. In one embodiment, the primary drive signal DR 136 is a rectangular pulse waveform having varying durations of logic high segments and logic low segments, the logic high segments corresponding to the power switch SI 112 being on and the logic low segments corresponding to the power switch SI 112 being off. In one embodiment, the first controller 124 outputs the primary drive signal DR 136 to turn on the power switch SI 112 in response to a request event 199 in the request signal REQ 132. The first controller 124 outputs the primary drive signal DR 136 to turn off the power switch SI 112 when the switching current ID 137 provided by the current sense signal ISNS 129 reaches a current limit.

[0033] If the clamp circuit 104 includes active components, such as transistors, the first controller 124 can also output a clamp drive signal (not shown). The clamp drive signal can control various switching parameters of the clamp switch included in the clamp circuit 104, such as the on-time or the off-time of the clamp switch. In one embodiment, in response to a request event 199 in the request signal REQ 132, the first controller 124 outputs the clamp drive signal to turn on the clamp switch for a duration of time that can be selected to provide sufficient charge from the clamp circuit 104 to the input winding 108 to discharge the parasitic capacitance of the power switch SI 112. Once the first controller 124 turns off the clamp switch of the clamp circuit 104, the first controller 124 outputs the primary drive signal DR 136 to turn on the power switch SI 112.

[0034] The second controller 126 and the first controller 124 can communicate via a communication link 135. For the illustrated embodiment, the second controller 126 is coupled to the secondary side of the primary power converter 100 and references the output return line 118, while the first controller 124 is coupled to the primary side of the primary power converter 100 and references the input return line 111. In embodiments, the first controller 124 and the second controller 126 are galvanically isolated from one another, and the communication link 135 provides galvanic isolation using an inductive coupling (such as a transformer or a coupled inductor), an optical coupler, a capacitive coupling, or other device that maintains isolation. However, it should be understood that in some embodiments, the second controller 126 is not galvanically isolated from the first controller 124.

[0035] In one embodiment, the first controller 124 and the second controller 126 can be formed as part of an integrated circuit fabricated as a hybrid integrated circuit or a monolithic integrated circuit. In one embodiment, the power switch SI 112 can also be integrated with the first controller 124 and the second controller 126 in a single integrated circuit package. Additionally, in one embodiment, the first controller 124 and the second controller 126 can be formed as separate integrated circuits. The power switch SI 112 can also be integrated in the same integrated circuit as the first controller 124, or can be formed as an integrated circuit separately. Additionally, it should be understood that neither the primary controller 124, the secondary controller 126, and the power switch SI 112 have to be included in a single package, and can be implemented in separate controller packages or a combination of combined / separate packages.

[0036] It is generally understood that a closed switch can conduct current and is considered to be on, while an open switch is unable to conduct current and is considered to be off. In one embodiment, the power switch SI 112 can be a transistor, such as a metal-oxide-semiconductor field-effect transistor (MOSFET), a bipolar junction transistor (BJT), a silicon carbide (SiC) based transistor, a gallium nitride (GaN) based transistor, or an insulated-gate bipolar transistor (IGBT).

[0037] The primary power converter 100 also includes an auxiliary converter 140 coupled to the output capacitor CO 115. The auxiliary converter 140 is also coupled to the bypass capacitor 133 and the bypass terminal BP 130 of the second controller 126. In embodiments, the auxiliary converter 140 provides a low voltage power supply (e.g., a bypass voltage VBP 131) from a higher voltage rail (e.g., the output voltage VOUT 116) of the primary power converter 100 to provide operating power. For the illustrated embodiment, the auxiliary converter 140 provides the bypass voltage VBP 131 for the second controller 126 from the output voltage VOUT 116 of the primary power converter 100.

[0038] The auxiliary converter 140 is shown to include a timing circuit 142, an auxiliary power switch S3 133, an energy transfer element L2 146 (shown as an inductor), a freewheeling diode Dl 148, and a diode D2 150. An auxiliary drive signal ADR 143 that controls the switching of the auxiliary power switch S3 144 can originate from the first controller 124 or the second controller 126. In the illustrated embodiment, the auxiliary drive signal ADR 143 originates from the second controller 126, specifically, from the secondary drive signal SR 128.

[0039] In the illustrated embodiment, the auxiliary converter 140 is coupled in a buck converter configuration to output capacitor CO 115 and output voltage VOUT 116 as its input and bypass capacitor 133 and bypass voltage VBP 131 as its output. The auxiliary converter 140 is also an open loop converter, and the operating frequency of the auxiliary power switch S3 144 is responsive to the operating frequency of the switches of the main power converter 100 (e.g., power switch SI 112 or output rectifier S2 114). As mentioned above, the output voltage VOUT 116 is the voltage generated by the main power converter 100.

[0040] The timing circuit 142 is coupled to the second controller 126 and is configured to generate the auxiliary drive signal ADR 143 in response to the secondary drive signal SR 128. The timing circuit 142 can also be referred to as an auxiliary drive circuit configured to control the switching of the auxiliary power switch S3 144. In one embodiment, the timing circuit 142 is capacitively coupled to the second controller 126. In another embodiment, the timing circuit is directly coupled to the second controller 126. The auxiliary drive signal ADR 143 controls the switching of the auxiliary power switch S3 144. In an implementation, the timing circuit determines the on-time or off-time of the auxiliary power switch S3 144 in response to the secondary drive signal SR 128. However, it should be understood that in other implementations, the timing circuit 142 can be coupled to receive other signals representative of the operating frequency of the main power converter 100 other than the secondary drive signal SR 128. For example, the timing circuit 142 can be coupled to one winding of the energy transfer element Tl 106, such as the tertiary winding or from a tapped node of the output winding 110 or a tapped node of the input winding 108. It should be understood that in other embodiments, the secondary drive signal SR 128 can be replaced with a switching edge waveform generated from an auxiliary winding of the main converter energy transfer element Tl 106 of the main power converter 100.

[0041] The auxiliary power switch S3 144 is coupled to the input of the auxiliary converter and the output capacitor CO 115 of the main power converter. The auxiliary power switch S3 144 is also coupled to the energy transfer element L2 146. The auxiliary power switch S3 144 can be a transistor such as a metal oxide semiconductor field effect transistor (MOSFET), a bipolar junction transistor (BJT), a silicon carbide (SiC) based transistor, a gallium nitride (GaN) based transistor, or an insulated gate bipolar transistor (IGBT).

[0042] The freewheeling diode Dl 148 is coupled to the auxiliary power switch S3 144 and the output return 118. The energy transfer element L2 146 is coupled to the diode D2 150 which is coupled to the bypass terminal BP 130 and the bypass capacitor 133. The auxiliary power switch S3 144, the freewheeling diode Dl 148, and the energy transfer element L2 are shown coupled in a buck converter configuration. The diode D2 150 is coupled as a blocking diode to prevent current from flowing from the output of the auxiliary converter 140 to the input of the auxiliary converter 140. Or in other words, the diode D2 150 prevents current from flowing from the bypass capacitor 133 to the output capacitor CO 115 in the event that the output voltage VOUT 116 falls below the bypass voltage VBP 131. It should be understood that in a main power converter where the output voltage VOUT 116 will operate in a range such that the output voltage VOUT 116 is always greater than the bypass voltage VBP 131, the diode D2 150 can be omitted from the auxiliary converter 140 while still maintaining the benefits of the present invention.

[0043] In operation, the timing circuit 142 outputs an auxiliary drive signal ADR 143 to turn on the auxiliary power switch S3 144. When the auxiliary power switch S3 144 is on, the output capacitor CO 115 is coupled to the energy transfer element L2 146 and substantially the output voltage VOUT 116 minus the sum of the bypass voltage VBP 131 and the voltage drop across the diode D2 150 is applied across the energy transfer element L2 146. The energy transfer element L2 146 is exemplified as an inductor. As such, the inductor current IL2 145 of the inductor L2 146 is substantially a function of the voltage across the inductor L2 146 divided by the inductance of the inductor L2 146 multiplied by the on-time of the auxiliary power switch S3 144. In one embodiment, when the auxiliary power switch S3 144 is on, the inductor current IL2 145 increases linearly and flows from the auxiliary switch S3 144 to the bypass capacitor 133. Additionally, the inductor current IL2 145 and the auxiliary switch current IS3 149 are substantially the same.

[0044] Timing circuit 142 outputs an auxiliary drive signal to turn off auxiliary power switch S3 144. As such, auxiliary switch current IS3 149 falls to zero and inductor current IL2 145 linearly decreases as a function of the voltage across inductor L2 146 divided by the inductance of inductor L2 146 until inductor current IL2 145 reaches zero or auxiliary power switch S3 144 turns on. Inductor current IL2 145 flows from freewheeling diode Dl 148 to bypass capacitor 133. As shown, diode Dl 148 is coupled to provide a path for inductor current IL2 145 when timing circuit 142 turns off auxiliary switch S3 144. Or in other words, diode Dl 148 allows inductor current IL2 145 to freewheel through auxiliary converter 140.

[0045] Figure 2A One embodiment of an auxiliary converter 240 that can be used with Figure 1 the primary power converter 100 of FIG. 1 is illustrated. It should be understood that similarly named and numbered elements are coupled and function as described above. Additionally, portions of the primary power converter such as output rectifier S2 114 and output capacitor CO 115 have been reproduced in FIG. 2 to provide context for the coupling of auxiliary converter 240.

[0046] For the illustrated embodiment, timing circuit 142 includes capacitor C1 252 and resistor R1 254. Thus, auxiliary converter 240 is capacitively coupled to receive secondary drive signal SR 128 from second controller 126. Auxiliary power switch S3 244 is exemplified as having its emitter terminal coupled to output capacitor CO 115 and its collector terminal coupled to a pnp BJT of power transfer element L2 146 (e.g., inductor L2 146) and freewheeling diode D1 148. Specifically, the collector terminal of auxiliary power switch S3 244 is coupled to the cathode of freewheeling diode D1 148. The base terminal of auxiliary power switch S3 244 is coupled to receive auxiliary drive signal ADR 143. Additionally, a resistor R2 256 is coupled between the base terminal and the emitter terminal. As shown, the auxiliary switching current IS3 149 is approximately the collector current of the PNP BJT, while the auxiliary voltage VL2 146 is approximately the collector voltage of the PNP BJT. For an embodiment where the output voltage VOUT116 is between 20-40V with a 2.2 microfarad (μF) bypass capacitor 133, the inductance of inductor L2 146 is approximately 470 microhenries (μH), the capacitance of capacitor C1 is approximately 470 picofarads (pF), the resistance of resistor R1 is approximately 1 kiloohm (kΩ), the resistance of resistor R2 is approximately 1.5 kΩ, and the auxiliary power switch S3 244 can be a 2N2907 transistor. Diodes D1 148 and D2 150 can be small-signal diodes.

[0047] Resistor R1 254 and capacitor C1 252 form an RC circuit. The RC time constant of resistor R1 254 and capacitor C1 252 determines the on-time of auxiliary power switch S3 244. The values ​​of resistor R1 254 and capacitor C1 252 can be selected based on the amount of step-down from output voltage VOUT 116 to bypass voltage VBP 131. For example, output voltage VOUT 116 can be between 20-40V, while bypass voltage VBP 131 is regulated to approximately 4.4V. In one embodiment, the values ​​of resistor R1 254 and capacitor C1 252 can be selected such that a time constant of 2-2.5 is approximately equal to 1-2 milliseconds (μs).

[0048] Resistor R2 256 facilitates the turn-off of auxiliary power switch S3 244 and provides a discharge path for reset capacitor C1 252. The RC time constants of resistors R1 254, R2 256, and capacitor C1 252 determine the duration of reset capacitor C1 252. (The remaining text appears to be incomplete and requires further context.) Figure 2BFurther discussed, when the secondary drive signal SR 128 turns off the output rectifier S2 114, the capacitor CI 252 is reset.

[0049] Figure 2B A timing diagram 201 is illustrated with example waveforms for the auxiliary drive signal ADR 143 (e.g., illustrated as the base voltage of the auxiliary switch S3 244), the auxiliary voltage VL2 147 (e.g., the collector voltage of the auxiliary switch S3 244), the auxiliary switch current IS3 149 (e.g., the collector current of the auxiliary switch S3 244), the energy transfer element current IL2 145 (e.g., the current of the inductor L2 146), and the secondary drive signal SR 128.

[0050] In the illustrated embodiment, at time tl 280, the secondary drive signal SR 128 has been logic high, indicating that the output rectifier S2 114 is on. After time tl 280, the auxiliary drive signal ADR 143 is substantially equal to the output voltage VOUT 116, and the auxiliary voltage VL2 147 is substantially equal to the bypass voltage VBP 131. Additionally, the auxiliary switch current IS3 149 and the energy transfer element current IL2 145 are substantially zero.

[0051] At time t2 282, the secondary drive signal SR 128 transitions to a logic low value, indicating to turn off the output rectifier S2 114. The resistor R1 254 and the capacitor C1 252 provide a drive current to the auxiliary power switch S3 244 (illustrated as a pnp BJT), and the time constant of the resistor R1 254 and the capacitor C1 252 determines the on-time of the auxiliary power switch S3 244. As shown at time t2 282, the auxiliary drive signal ADR 143 decreases and then increases to the output voltage VOUT 116. The duration required to increase to the output voltage VOUT 116 is responsive to the time constant of the resistor R1 254 and the capacitor C1 252. As shown, if the difference between the output voltage VOUT 116 and the value of the auxiliary drive signal ADR 143 is greater than the base-emitter threshold of the auxiliary power switch S3 244, the auxiliary power switch S3 244 remains on. Additionally, at time t2 282, the auxiliary voltage VL2 147 generally increases to the output voltage VOUT 116 and remains at the output voltage VOUT 116 for the remainder of the conduction (e.g., on-time) of the auxiliary power switch S3 244. During the on-time of the auxiliary power switch S3 244, both the auxiliary switch current IS3 149 and the energy transfer element current IL2 145 linearly increase. As mentioned above, the rate of increase is a function of the voltage across the inductor L2 146 divided by the inductance of the inductor L2 146.

[0052] At time t3 284, the capacitor C1 252 has discharged through the resistor R1 254, and the auxiliary drive signal ADR 143 generally reaches the output voltage VOUT 116, and the auxiliary power switch S3 244 stops conducting (e.g., turns off). The auxiliary voltage VL2 147 is generally equal to the output rail 118 minus the voltage drop across the freewheeling diode D1 148 (e.g., -V D1). The auxiliary switch current IS3149 also falls to substantially zero. However, the energy transfer element current IL2145 continues to flow through diode D1148, and the energy transfer element current IL2145 decreases linearly. The rate of decrease is substantially a function of the voltage across the inductor L2146 divided by the inductance of the inductor L2146. For the illustrated embodiment, the energy transfer element current IL2145 decreases to substantially zero at time t4286. If the energy transfer element current IL2145 decreases to substantially zero, the auxiliary converter 240 operates in discontinuous conduction mode (DCM). Additionally, once the energy transfer element current IL2145 reaches zero, a relaxation ring can be observed at the auxiliary voltage VL2147. After time t4286, the auxiliary voltage VL2147 oscillates around the bypass voltage VBP131. For the illustrated embodiment, the oscillation decays to the bypass voltage VBP131 before the auxiliary switch S3244 is turned on in the subsequent cycle, however, it should be understood that the oscillation can continue until the auxiliary switch S3244 is turned on in the subsequent cycle.

[0053] At time t5288, the secondary drive signal SR128 transitions to a logic high value, indicating turn on of the output rectifier S2114. When the secondary drive signal SR128 transitions to a logic high value at time t5288, the auxiliary drive signal ADR143 increases and then decreases in response to the RC time constant of the capacitor C1252 and resistors R1254 and R2256. In one embodiment, the auxiliary drive signal ADR143 increases above the emitter reference of the auxiliary power switch S3244, increasing the bypass voltage VBP131. The capacitor C1252 discharges through resistors R1254 and R2256 to substantially the output voltage VOUT116, which will reset the voltage across the capacitor C1252, allowing it to be ready for the next trailing edge of the secondary drive signal SR128.

[0054] The amount of power delivered by the auxiliary converter 240 is substantially a function of the voltage across the inductor L2146 during the on-time of the auxiliary power switch S3244, the inductance of the inductor L2146, and the switching frequency f SW of the secondary drive signal SR128, or mathematically:

[0055]

[0056] Figure 3 It is exemplified that the auxiliary converter 240 can be used in a variety of applications, including but not limited to: Figure 1Another example auxiliary converter 340 is used in conjunction with the main power converter 100. It should be understood that similarly named and numbered components are coupled and function as described above. Additionally, portions of the main power converter, such as the output rectifier S2 114 and the output capacitor CO 115, are already... Figure 3 The reproduction in the middle provides context for the coupling of the auxiliary converter 340. Additionally, the auxiliary converter 340 is similar to... Figure 2A The auxiliary converter 240 is shown. However, at least one difference is that the auxiliary power switch S3 344 is exemplified as a p-type MOSFET (PMOS). As shown, the source terminal of the auxiliary power switch S3 344 is coupled to the input of the auxiliary converter 340, which is coupled to the output capacitor CO 115; the drain terminal of the auxiliary power switch S3 344 is coupled to the cathode of the power transfer element L2 146 and the freewheeling diode D1 148; and the gate terminal of the auxiliary power switch S3 344 is coupled to the timing circuit 142, shown as a resistor R1 254 and a capacitor C1 252. In the illustrated embodiment, the voltage at the gate terminal of the auxiliary power switch S3 344 is the auxiliary drive signal ADR 143. Resistor R2 256 is illustrated as being coupled between the drain and source terminals of the auxiliary power switch S3 344.

[0057] Figure 4 Examples of what can be done with Figure 1 Another example auxiliary converter 440 is used in conjunction with the main power converter 100. It should be understood that similarly named and numbered components are coupled and function as described above. Additionally, parts of the main power converter, such as the output rectifier S2 114 and the output capacitor CO 115, are already... Figure 4 The following provides context for the coupling of auxiliary converter 440. Auxiliary converter 440 is similar to auxiliary converter 240 shown in Figure 2. However, at least one difference is that the power transfer element 446 is exemplified as a coupled inductor T2446 having a first winding 470 and a second winding 472. Similar to the above, auxiliary power switch S3 244 is shown as a PNP BJT. The collector terminal of auxiliary power switch S3 244 is coupled to one end of the first winding 470. The other end of the first winding 470 is coupled to the output return line 118. Diode D2 150 is coupled to one end of the second winding 472, while the other end of the second winding 427 is coupled to the output return line 118. Auxiliary converter 440 is coupled and functions similarly to a flyback converter. However, it should be understood that other polarities can be utilized for the coupled inductor T2 446. For example, the polarity for the coupled inductor T2 446 can be selected to allow auxiliary converter 440 to act as a forward converter.

[0058] Figure 5 Examples of what can be done with Figure 1 Another example auxiliary converter 540 is used in conjunction with the main power converter 100. It should be understood that similarly named and numbered components are coupled and function as described above. Additionally, portions of the main power converter, such as the output rectifier S2 114 and the output capacitor CO 115, are already... Figure 5 The reproduction in the middle provides context for the coupling of the auxiliary converter 540. Additionally, the auxiliary converter 540 is similar to... Figure 2A The auxiliary converter 240 shown is illustrated. However, at least one difference is that the auxiliary converter 540 also includes a second auxiliary switch S4 573 and resistors R3 574, R4 575 and R5 576.

[0059] Auxiliary switch S3 344 is exemplified as a pnp BJT, while the second auxiliary switch S4 573 is exemplified as an npn BJT; however, it should be understood that other transistors may be used. As shown, the base terminal of auxiliary switch S3 244 is coupled to capacitor C1 252 and resistor R2 256. Additionally, resistor R1 254 is coupled to receive the second controller 126 and the secondary drive signal SR 128. The second auxiliary switch S4 573 is coupled to the node between resistor R1 254 and capacitor C1 252. As shown, the collector terminal of the second auxiliary switch S4 573 is coupled to the node between resistor R1 254 and capacitor C1 252. The base terminal of the second auxiliary switch S4 573 is coupled to both resistors R3 574 and R4 575. As shown, resistors R3 574 and R4 575 are coupled to form a resistive voltage divider for the input of auxiliary converter 540. The input of auxiliary converter 540 is coupled to the output of power converter 500. Thus, resistors R3 574 and R4 575 are coupled to form a resistive voltage divider for the output voltage VOUT 116. Resistor R5 576 is coupled to the emitter terminal of auxiliary switch S4 573. Both resistors R4 575 and R5 576 are coupled to output loop 116. However, it should be understood that resistor R5 576 may be optional.

[0060] Typically, an auxiliary converter without a second auxiliary switch S4 573 and resistors R3 574, R4 575, and R5 576 has a substantially constant on-time for auxiliary switch S3 244, regardless of the input to the auxiliary converter (e.g., output voltage VOUT 116). Thus, the energy transfer element current IL2 145 typically increases with increasing output voltage VOUT 116, which may be related to the increased energy supplied by the auxiliary converter. During operation, the second auxiliary switch S4 573 and resistors R3 574, R4 575, and R5 576 are configured to reduce the on-time of auxiliary switch S3 244 as the input to the auxiliary converter 540 (e.g., output voltage VOUT 116 in this embodiment) increases. During operation, when the second auxiliary switch S4 573 is on, the voltage at the node between resistors R1 254 and C1 252 may decrease. The amount of voltage reduction at this node is a function of the input of the auxiliary converter (e.g., the output voltage VOUT 116). The larger the input (e.g., the output voltage VOUT 116), the larger the current drawn by the second auxiliary switch S4 573, and the lower the voltage at the node between resistors R1 254 and C1 252. Thus, as the output voltage VOUT 116 increases, the second auxiliary switch S4 573, along with resistors R3 574, R4 575, and R5 576, can reduce the on-time of the auxiliary power switch S3 244. By reducing the on-time of the auxiliary switch S2 233, the peak power transfer element current IL2 145 can be compensated by the increased output voltage VOUT 116, and the peak power transfer element current IL2 145 can be relatively independent of the output voltage VOUT 116. In one embodiment, the auxiliary converter 540 can provide constant power to its output (e.g., bypass capacitor 133 and bypass terminal 5BP 130) regardless of the value of the output voltage VOUT 116.

[0061] Figure 6 Another example of a primary power converter 600 according to one embodiment of the present disclosure is illustrated, which includes an auxiliary converter 640 to obtain a bypass voltage VBP 131 for a bypass capacitor 133 that supplies power to a first controller 124 (e.g., a primary controller) of the primary power converter 600. In other words, the auxiliary converter 640 may be coupled to the input side of the power converter 600 to provide an efficient power source for the first controller 124 and to supply operating current to the first controller 124.

[0062] It should be understood that the main power converter 600 and the auxiliary converter 640 are related to... Figure 1The illustrated primary power converter 100 and auxiliary converter 140 share many similarities, and similarly named and numbered elements couple and function as described above. However, at least one difference is that the input of the auxiliary converter 640 is coupled to the third winding 691 of the energy transfer element 106 of the primary power converter 600, and the auxiliary converter 640 provides operating power to the circuit of the first controller 124. As such, the bypass voltage VBP 131 of the bypass capacitor 133 is obtained from a bias voltage VBIAS 692 of the third winding 691. The bias voltage VBIAS 692 is further generated by the primary power converter 600. The bypass capacitor 133 is coupled to a bypass terminal BP 693 of the first controller 124 to provide operating power to the circuit of the first controller. It should also be understood that any of the example auxiliary converters discussed above can be used with Figure 6 the auxiliary converter 640.

[0063] The third winding 691 in the illustrated embodiment is an input referenced winding of the energy transfer element 106, and is coupled to the input return 111. The other end of the third winding 691 is coupled to the input of the auxiliary converter 640 and provides a voltage rail from which the auxiliary converter 640 obtains a low voltage power supply for the first controller 124. As illustrated, the third winding 691 is coupled to an auxiliary switch S3 144 of the auxiliary converter 640. The auxiliary converter 640 is also coupled to the first controller 124 to receive a primary drive signal DR 136 that is representative of the operating frequency (e.g., switching frequency f SW ) of the primary power converter 600. It should be understood that in other embodiments, the auxiliary converter 640 can be coupled to receive an inverted version of the primary drive signal DR 136 while benefiting from the teachings of the present disclosure. The timing circuit 142 can also be referred to as an auxiliary drive circuit configured to control the switching of the auxiliary power switch S3 144. As illustrated, the timing circuit 142 is configured to generate an auxiliary drive signal ADR 143 in response to the primary drive signal DR 136. However, it should be understood that in other embodiments, the primary drive signal DR 136 can be replaced by a switching waveform derived from a winding on the energy transfer element T1 106. As illustrated, the output of the auxiliary converter 640 is coupled to the bypass terminal BP 693 of the primary controller 124. The output of the auxiliary converter 640 provides operating power / current to the bypass terminal BP 693 of the primary controller 124.

[0064] Figure 7 It is exemplified that the auxiliary converter 640 can be used with Figure 1An example auxiliary converter 740 is used in conjunction with the main power converter 100. It should be understood that similarly named and numbered components are coupled and function as described above. Additionally, portions of the main power converter, such as the output rectifier S2 114 and the output capacitor CO 115, are already... Figure 7 The reproduction in the middle provides context for the coupling of the auxiliary converter 740. Additionally, the auxiliary converter 740 is similar to... Figure 2A The auxiliary converter 240 is shown. However, at least one difference is that the auxiliary converter 740 includes resistor R7 778, instead of... Figure 1 and Figure 2A The energy transfer element L2 146 is shown. As shown, the collector terminal of the auxiliary power switch S3 244 is coupled to resistor R7 778. The other end of resistor R7 778 is coupled to diode D2 150. During operation, timing circuit 142 outputs auxiliary drive signal ADR 143 in response to secondary drive signal SR 128 to turn on auxiliary power switch S3 144. When auxiliary power switch S3 144 is on, output capacitor CO 115 is coupled to resistor R7 778, and approximately the sum of output voltage VOUT 116 minus bypass voltage VBP 131 and the voltage drop across diode D2 150 is applied across resistor R7 778. Using resistor R7 778, bypass capacitor 133 can be pulse-charged from output voltage VOUT 116.

[0065] Figure 8 Examples of what can be done with Figure 1 An example auxiliary converter 840 is used in conjunction with the main power converter 100. It should be understood that similarly named and numbered components are coupled and function as described above. Additionally, portions of the main power converter, such as the output rectifier S2 114 and the output capacitor CO 115, are already... Figure 8 The reproduction in the middle provides context for the coupling of the auxiliary converter 840. Additionally, the auxiliary converter 840 is similar to... Figure 7 The auxiliary converter 740 is shown. However, at least one difference is the addition of resistor R8 878 and capacitor C2 880. Similar to... Figure 7 The auxiliary converter 840 includes resistor R7778, instead of Figure 1 and Figure 2AThe energy transfer element L2 146 is shown in the middle. The collector terminal of the auxiliary power switch S3 244 is coupled to a resistor R7 778. The other end of the resistor R7 778 is coupled to a resistor R8 878 and a capacitor C2 880. As shown, the resistor R8 878 is then further coupled to the diode D2 150, while the capacitor C2 880 is coupled to the output return 118. In operation, the timing circuit 142 outputs an auxiliary drive signal ADR 143 in response to the secondary drive signal SR 128 to turn on the auxiliary power switch S3 144. When the auxiliary power switch S3 144 is on, the output capacitor CO 115 is coupled to the resistor R7 778, and the bypass capacitor 133 can be pulsed charged from the output voltage VOUT 116. The resistor R8 878 and the capacitor C2 880 are configured to smooth any current ripple to the bypass capacitor 133.

[0066] The above description of the illustrated embodiments of the application, including what is described in the abstract, is not intended to be exhaustive or to be limiting to the precise forms disclosed. While specific embodiments of, and examples for, the application are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the application, as those skilled in the relevant art will recognize. In fact, changes can be made to the specific form of the application described above and still be within the scope of the application. For example, the specific voltage, current, frequency, power range values, times, etc. provided are for illustrative purposes and other values can be employed in other embodiments and examples in accordance with the teachings of the present application.

[0067] While the application has been defined by reference to a specific embodiment and examples, it will be recognized that equivalents modifications are possible. For example, the following embodiments can be used to alternatively define the application: Embodiment 1. An auxiliary converter coupled to an output of a primary power converter, comprising: an auxiliary switch coupled to the output of the primary power converter; a timing circuit coupled to receive a control signal from a controller of the primary power converter, wherein the controller regulates the output of the primary power converter, the timing circuit configured to output an auxiliary drive signal to control switching of the auxiliary switch in response to the control signal; and an energy transfer element coupled to the auxiliary switch, wherein the energy transfer element is configured to transfer energy from the output of the primary power converter to a power supply of the controller that provides operating power for the controller of the primary power converter.

[0068] Embodiment 2. The auxiliary converter of embodiment 1, wherein the timing circuit is capacitively coupled to the controller to generate the auxiliary drive signal.

[0069] Embodiment 3. The auxiliary converter of embodiments 1 or 2, wherein the timing circuit is directly coupled to the controller to generate the auxiliary drive signal.

[0070] Embodiment 4. The auxiliary converter of any of embodiments 1-3, wherein the auxiliary drive signal is level shifted to drive the auxiliary switch.

[0071] Embodiment 5. The auxiliary converter of any of embodiments 1-4, wherein the auxiliary drive signal is generated by a winding of an energy transfer element of the main power converter, the energy transfer element of the main power converter configured to transfer energy from an input of the main power converter to an output of the main power converter.

[0072] Embodiment 6. The auxiliary converter of any of embodiments 1-5, wherein the controller of the main power converter is coupled to an input of the main power converter.

[0073] Embodiment 7. The auxiliary converter of any of embodiments 1-6, wherein the controller of the main power converter is coupled to the output of the main power converter.

[0074] Embodiment 8. The auxiliary converter of any of embodiments 1-7, wherein the auxiliary converter is an open loop converter operating at a frequency derived from an operating frequency of the main power converter.

[0075] Embodiment 9. The auxiliary converter of any of embodiments 1-8, wherein the auxiliary converter is a buck converter.

[0076] Embodiment 10. The auxiliary converter of any of embodiments 1-9, wherein the auxiliary switch comprises a bipolar junction transistor (BJT).

[0077] Embodiment 11. The auxiliary converter of any of embodiments 1-10, wherein the auxiliary switch comprises a metal oxide semiconductor field effect transistor (MOSFET).

[0078] Embodiment 12. The auxiliary converter of any of embodiments 1-11, wherein the energy transfer element of the auxiliary converter comprises an inductor.

[0079] Embodiment 13. The auxiliary converter of any of embodiments 1-12, wherein the energy transfer element of the auxiliary converter comprises a coupled inductor.

[0080] Example 14. The auxiliary converter of any one of Examples 1-13, the timing circuit comprising: a capacitor coupled to the controller; and a first resistor coupled to the capacitor and a control terminal of the auxiliary switch, wherein a time constant of the capacitor and the first resistor determines a turn-on time of the auxiliary switch.

[0081] Example 15. The auxiliary converter of any one of Examples 1-14, further comprising: a second resistor coupled to the control terminal of the auxiliary switch and the output of the main power converter, wherein a time constant of the capacitor, the first resistor, and the second resistor determines a reset time of the capacitor.

[0082] Example 16. The auxiliary converter of any one of Examples 1-15, further comprising: a second auxiliary switch coupled to the capacitor and the first resistor; a third resistor coupled to the output of the main power converter and the second auxiliary switch; and a fourth resistor coupled to the second auxiliary switch, wherein the second auxiliary switch, third resistor, and fourth resistor are configured to change a voltage between the capacitor and the first resistor in response to the output of the main power converter.

[0083] Example 17. The auxiliary converter of any one of Examples 1-16, further comprising: a first diode coupled to the energy transfer element of the auxiliary converter to provide a path for current of the energy transfer element when the auxiliary switch is off.

[0084] Example 18. The auxiliary converter of any one of Examples 1-17, further comprising: a second diode coupled to the energy transfer element of the auxiliary converter and the power supply of the controller, the second diode coupled to prevent current flow from the power supply to the output of the main power converter.

[0085] Example 19. A main power converter comprising: an energy transfer element coupled between an input of the main power converter and an output of the main power converter; a power switch coupled to the energy transfer element; a first controller coupled to the input of the main power converter, the first controller configured to generate a first drive signal to control switching of the power switch to transfer energy between the input and the output of the main power converter, the first controller configured to receive a request signal and generate the first drive signal in response to a request event in the request signal; an output rectifier coupled to the energy transfer element; a second controller coupled to the output of the main power converter, the second controller configured to generate the request event in the request signal in response to the output of the main power converter, the second controller further configured to generate a second drive signal to control switching of the output rectifier; and an auxiliary converter coupled to the output of the main power converter and configured to generate a power supply to provide operating power for the second controller, the power supply generated in response to the second drive signal.

[0086] Example 20. The main power converter of Example 19, the auxiliary converter comprising: an auxiliary switch coupled to the output of the main power converter; a timing circuit coupled to receive the second drive signal from the second controller, the timing circuit configured to output an auxiliary drive signal to control switching of the auxiliary switch in response to the second drive signal; and an energy transfer element coupled to the auxiliary switch, wherein the energy transfer element transfers energy from the output of the main power converter to the power supply of the second controller.

[0087] Example 21. The main power converter of Example 19 or 20, wherein the auxiliary switch comprises a bipolar junction transistor (BJT).

[0088] Example 22. The main power converter of any of Examples 19-21, the timing circuit comprising: a capacitor coupled to the second controller to receive the second drive signal; and a first resistor coupled to the capacitor and a control terminal of the auxiliary switch, wherein a time constant of the capacitor and the first resistor determines a turn-on time of the auxiliary switch.

[0089] Example 23. The primary power converter of any one of Examples 19-22, the timing circuit further comprising: a second resistor coupled to the control terminal of the auxiliary switch and the output of the primary power converter, wherein a time constant of the capacitor, the first resistor, and second resistor determines a reset time of the capacitor.

[0090] Example 24. The primary power converter of any one of Examples 19-23, the auxiliary converter further comprising: a second diode coupled to the energy transfer element of the auxiliary converter and the power supply of the second controller, the second diode configured to prevent a flow of current from the power supply of the second controller to the output of the primary power converter.

[0091] Example 25. An auxiliary converter coupled to a primary power converter, comprising: an auxiliary switch coupled to an input of the auxiliary converter, wherein the input of the auxiliary converter is coupled to receive a voltage generated by the primary power converter; a timing circuit coupled to receive a control signal from a controller of the primary power converter, wherein the controller regulates an output of the primary power converter, the timing circuit configured to output an auxiliary drive signal to control switching of the auxiliary switch in response to the control signal; and an energy transfer element coupled to the auxiliary switch, wherein the energy transfer element is configured to transfer energy from the input of the auxiliary converter to an output of the auxiliary converter that provides operating power for the controller of the primary power converter.

[0092] Example 26. The auxiliary converter of Example 25, wherein the input of the auxiliary converter is coupled to an output side of the primary power converter and is coupled to receive an output voltage generated by the primary power converter.

[0093] Example 27. The auxiliary converter of Example 25 or 26, wherein the input of the auxiliary converter is coupled to an input side of the primary power converter and is coupled to receive a voltage of a reference input generated by the primary power converter.

[0094] Example 28. The auxiliary converter of any one of Examples 25-27, wherein the timing circuit is capacitively coupled to the controller to generate the auxiliary drive signal.

[0095] Example 29. The auxiliary converter of any one of Examples 25-28, wherein the timing circuit is directly coupled to the controller to generate the auxiliary drive signal.

[0096] Embodiment 30. The auxiliary converter of any one of embodiments 25-29, wherein the auxiliary drive signal is level shifted to drive the auxiliary switch.

[0097] Embodiment 31. The auxiliary converter of any one of embodiments 25-30, wherein the auxiliary drive signal is generated by a winding of an energy transfer element of the main power converter, the energy transfer element of the main power converter configured to transfer energy from an input of the main power converter to the output of the main power converter.

[0098] Embodiment 32. The auxiliary converter of any one of embodiments 25-31, wherein the controller of the main power converter is coupled to the input of the main power converter.

[0099] Embodiment 33. The auxiliary converter of any one of embodiments 25-32, wherein the controller of the main power converter is coupled to the output of the main power converter.

[0100] Embodiment 34. The auxiliary converter of any one of embodiments 25-33, wherein the auxiliary converter is an open loop converter operating at a frequency derived from an operating frequency of the main power converter.

[0101] Embodiment 35. The auxiliary converter of any one of embodiments 25-24, wherein the auxiliary converter is a buck converter.

[0102] Embodiment 36. The auxiliary converter of any one of embodiments 25-35, wherein the auxiliary switch comprises a bipolar junction transistor (BJT).

[0103] Embodiment 37. The auxiliary converter of any one of embodiments 25-36, wherein the auxiliary switch comprises a metal oxide semiconductor field effect transistor (MOSFET).

[0104] Embodiment 38. The auxiliary converter of any one of embodiments 25-37, wherein the energy transfer element comprises an inductor.

[0105] Embodiment 39. The auxiliary converter of any one of embodiments 25-38, wherein the energy transfer element comprises a coupled inductor.

[0106] Embodiment 40. The auxiliary converter of any one of embodiments 25-39, the timing circuit comprising: a capacitor coupled to the controller; and a first resistor coupled to the capacitor and a control terminal of the auxiliary switch, wherein a time constant of the capacitor and the first resistor determines a turn-on time of the auxiliary switch.

[0107] Embodiment 41. The auxiliary converter of any one of embodiments 25-40, further comprising: a second resistor coupled to the control terminal of the auxiliary switch and the input of the auxiliary converter, wherein a time constant of the capacitor, the first resistor, and the second resistor determines a reset time of the capacitor.

[0108] Embodiment 42. The auxiliary converter of any one of embodiments 25-41, further comprising: a second auxiliary switch coupled to the capacitor and the first resistor; a third resistor coupled to the input of the auxiliary converter and the second auxiliary switch; and a fourth resistor coupled to the second auxiliary switch, wherein the second auxiliary switch, third resistor, and fourth resistor are configured to reduce a voltage between the capacitor and the first resistor in response to the input of the auxiliary converter.

[0109] Embodiment 43. The auxiliary converter of any one of embodiments 25-42, further comprising: a first diode coupled to the energy transfer element of the auxiliary converter to provide a path for current of the energy transfer element when the auxiliary switch is off.

[0110] Embodiment 44. The auxiliary converter of any one of embodiments 25-43, further comprising: a second diode coupled to the energy transfer element of the auxiliary converter and the output of the auxiliary converter, the second diode coupled to prevent current flow from the output of the auxiliary converter to the input of the auxiliary converter.

[0111] Example 45. An auxiliary converter coupled to a main power converter, comprising: an auxiliary switch coupled to an input of the auxiliary converter, wherein the input of the auxiliary converter is coupled to receive a voltage generated by the main power converter; a timing circuit coupled to receive a control signal from a controller of the main power converter, wherein the controller regulates an output of the main power converter, the timing circuit configured to output an auxiliary drive signal to control switching of the auxiliary switch in response to the control signal; and a first resistor coupled to the auxiliary switch, the first resistor configured to provide current from the input of the auxiliary converter to an output of the auxiliary converter, wherein the output of the auxiliary converter provides operating power to the controller of the main power converter.

[0112] Example 46. The auxiliary converter of Example 45, further comprising: a capacitor coupled to the first resistor; and a second resistor coupled to the first resistor, the capacitor and the first resistor configured to smooth current provided to the output of the auxiliary converter.

Claims

1. An auxiliary converter configured to be coupled to an output of a main power converter, the auxiliary converter comprising: an auxiliary power switch coupled to an input of the auxiliary converter and to the output of the main power converter; a timing circuit configured to be coupled to receive a control signal from a controller of the main power converter, wherein the controller is to regulate the output of the main power converter, and wherein the timing circuit is configured to output an auxiliary drive signal to control switching of the auxiliary power switch and to determine a turn-on time or a turn-off time of the auxiliary power switch in response to the control signal; and an energy transfer element coupled to the auxiliary power switch such that when the auxiliary power switch is turned on, the input of the auxiliary converter is coupled to the energy transfer element, and when the auxiliary power switch is turned off, the input of the auxiliary converter is not coupled to the energy transfer element, wherein the energy transfer element is configured to transfer energy from the output of the main power converter to a power supply of the controller of the main power converter, the auxiliary converter thereby deriving a lower voltage power supply from a higher voltage on the output of the main power converter and providing operating power for the controller of the main power converter.

2. The auxiliary converter of claim 1, wherein the timing circuit is configured to be capacitively coupled to the controller of the main power converter to generate the auxiliary drive signal.

3. The auxiliary converter of claim 1, wherein the timing circuit is configured to be directly coupled to the controller of the main power converter to generate the auxiliary drive signal.

4. The auxiliary converter of claim 1, wherein the auxiliary drive signal is level shifted to drive the auxiliary power switch.

5. The auxiliary converter of claim 1, wherein the auxiliary drive signal is generated by a winding of an energy transfer element of the main power converter, the energy transfer element of the main power converter configured to transfer energy from an input of the main power converter to the output of the main power converter.

6. The auxiliary converter of claim 1, wherein the controller of the main power converter is coupled to an input of the main power converter, and wherein the control signal is a primary drive signal to control switching of a power switch of the main power converter.

7. The auxiliary converter of claim 1, wherein the controller of the main power converter is coupled to the output of the main power converter, and wherein the control signal is a secondary drive signal to control turn-on and turn-off of an output rectifier.

8. The auxiliary converter of claim 1, wherein the auxiliary converter is an open loop converter operating at a frequency derived from an operating frequency of the main power converter.

9. The auxiliary converter of claim 1, wherein the auxiliary converter is a buck converter. ​ 10. The auxiliary converter of claim 1, wherein the auxiliary power switch comprises a bipolar junction transistor (BJT).

11. The auxiliary converter of claim 1, wherein the auxiliary power switch comprises a metal oxide semiconductor field effect transistor (MOSFET).

12. The auxiliary converter of claim 1, wherein the energy transfer element of the auxiliary converter comprises an inductor.

13. The auxiliary converter of claim 1, wherein the energy transfer element of the auxiliary converter comprises a coupled inductor.

14. The auxiliary converter of claim 1, the timing circuit comprising: a capacitor coupled to the controller of the main power converter; and a first resistor coupled to the capacitor and a control terminal of the auxiliary power switch, wherein a time constant of the capacitor and the first resistor determines a turn-on time of the auxiliary power switch.

15. The auxiliary converter of claim 14, further comprising: a second resistor coupled to the control terminal of the auxiliary power switch and the output of the main power converter, wherein a time constant of the capacitor, the first resistor, and the second resistor determines a reset time of the capacitor.

16. The auxiliary converter of claim 14, further comprising: a second auxiliary switch coupled to the capacitor and the first resistor; a third resistor coupled to the output of the main power converter and the second auxiliary switch; and a fourth resistor coupled to the second auxiliary switch, wherein the second auxiliary switch, third resistor, and fourth resistor are configured to vary a voltage between the capacitor and the first resistor in response to the output of the main power converter.

17. The auxiliary converter of claim 1, further comprising: a first diode coupled to the energy transfer element of the auxiliary converter to provide a path for current of the energy transfer element when the auxiliary power switch is off.

18. The auxiliary converter of claim 1, further comprising: a second diode coupled to the energy transfer element of the auxiliary converter and the power supply of the controller of the main power converter, the second diode coupled to prevent current flow from the power supply to the output of the main power converter.

19. A main power converter, comprising: an energy transfer element coupled between an input of the main power converter and an output of the main power converter; a power switch coupled to the energy transfer element; ​ ​ a first controller coupled to the input of the main power converter, the first controller configured to generate a first drive signal to control switching of the power switch to transfer energy between the input and the output of the main power converter, the first controller configured to receive a request signal and generate the first drive signal in response to a request event in the request signal; an output rectifier coupled to the energy transfer element; a second controller coupled to the output of the main power converter, the second controller configured to generate the request event in the request signal in response to the output of the main power converter, the second controller further configured to generate a second drive signal to control switching of the output rectifier; and an auxiliary converter coupled to the output of the main power converter and configured to generate a power source to provide operating power for the second controller coupled to the output of the main power converter, energy transferred from the input to the output of the main power converter, the power source generated in response to the second drive signal that controls switching of the output rectifier, wherein the auxiliary converter comprises: an auxiliary power switch coupled to the output of the main power converter; a timing circuit coupled to receive the second drive signal from the second controller, the timing circuit configured to output an auxiliary drive signal to control switching of the auxiliary power switch and determine a turn-on time or a turn-off time of the auxiliary power switch in response to the second drive signal; and an energy transfer element coupled to the auxiliary power switch, wherein the energy transfer element transfers energy from the output of the main power converter to the power source of the second controller.

20. The main power converter of claim 19, wherein the auxiliary power switch comprises a bipolar junction transistor (BJT).

21. The main power converter of claim 20, the timing circuit comprising: a capacitor coupled to the second controller to receive the second drive signal; and a first resistor coupled to the capacitor and a control terminal of the auxiliary power switch, wherein a time constant of the capacitor and the first resistor determines the turn-on time of the auxiliary power switch.

22. The main power converter of claim 21, the timing circuit further comprising: a second resistor coupled to the control terminal of the auxiliary power switch and the output of the main power converter, wherein a time constant of the capacitor, the first resistor, and the second resistor determines a reset time of the capacitor.

23. The main power converter of claim 19, the auxiliary converter further comprising: ​ a second diode coupled to the energy transfer element of the auxiliary converter and the power supply of the second controller, the second diode configured to prevent current flow from the power supply of the second controller to the output of the primary power converter.

24. An auxiliary converter configured to be coupled to a primary power converter, the auxiliary converter comprising: an auxiliary power switch coupled to an input of the auxiliary converter, wherein the input of the auxiliary converter is coupled to receive a voltage generated by the primary power converter; a timing circuit configured to be coupled to receive a control signal from a controller of the primary power converter, wherein the controller is used to regulate an output of the primary power converter, and wherein the timing circuit is configured to output an auxiliary drive signal to control switching of the auxiliary power switch and determine a turn-on time or turn-off time of the auxiliary power switch in response to the control signal; and an energy transfer element coupled to the auxiliary power switch such that when the auxiliary power switch is turned on, the input of the auxiliary converter is coupled to the energy transfer element, and when the auxiliary power switch is turned off, the input of the auxiliary converter is not coupled to the energy transfer element, wherein the energy transfer element is configured to transfer energy from the input of the auxiliary converter to an output of the auxiliary converter, the output of the auxiliary converter thereby providing operating power for the controller of the primary power converter.

25. The auxiliary converter of claim 24, wherein the input of the auxiliary converter is configured to be coupled to an output side of the primary power converter and configured to be coupled to receive an output voltage generated by the primary power converter.

26. The auxiliary converter of claim 24, wherein the input of the auxiliary converter is configured to be coupled to an input side of the primary power converter and configured to be coupled to receive a voltage of a reference input generated by the primary power converter.

27. The auxiliary converter of claim 24, wherein the timing circuit is configured to be capacitively coupled to the controller of the primary power converter to generate the auxiliary drive signal.

28. The auxiliary converter of claim 24, wherein the timing circuit is configured to be directly coupled to the controller of the primary power converter to generate the auxiliary drive signal.

29. The auxiliary converter of claim 24, wherein the auxiliary drive signal is level shifted to drive the auxiliary power switch.

30. The auxiliary converter of claim 24, wherein, the auxiliary drive signal is generated by a winding of an energy transfer element of the primary power converter, the energy transfer element of the primary power converter configured to transfer energy from an input of the primary power converter to the output of the primary power converter.

31. The auxiliary converter of claim 24, wherein the controller of the main power converter is coupled to the input of the main power converter, and wherein the control signal is a primary drive signal for controlling switching of power switches of the main power converter.

32. The auxiliary converter of claim 24, wherein the controller of the main power converter is coupled to the output of the main power converter, and wherein the control signal is a secondary drive signal for controlling turn-on and turn-off of an output rectifier.

33. The auxiliary converter of claim 24, wherein the auxiliary converter is an open loop converter operating at a frequency derived from an operating frequency of the main power converter.

34. The auxiliary converter of claim 24, wherein the auxiliary converter is a buck converter.

35. The auxiliary converter of claim 24, wherein the auxiliary power switch comprises a bipolar junction transistor (BJT).

36. The auxiliary converter of claim 24, wherein the auxiliary power switch comprises a metal oxide semiconductor field effect transistor (MOSFET).

37. The auxiliary converter of claim 24, wherein the energy transfer element comprises an inductor.

38. The auxiliary converter of claim 24, wherein the energy transfer element comprises a coupled inductor.

39. The auxiliary converter of claim 24, the timing circuit comprising: a capacitor configured to be coupled to the controller of the main power converter; and a first resistor coupled to the capacitor and a control terminal of the auxiliary power switch, wherein a time constant of the capacitor and the first resistor determines a turn-on time of the auxiliary power switch.

40. The auxiliary converter of claim 39, further comprising: a second resistor coupled to the control terminal of the auxiliary power switch and the input of the auxiliary converter, wherein a time constant of the capacitor, the first resistor, and the second resistor determines a reset time of the capacitor.

41. The auxiliary converter of claim 39, further comprising: a second auxiliary switch coupled to the capacitor and the first resistor; a third resistor coupled to the input of the auxiliary converter and the second auxiliary switch; and a fourth resistor coupled to the second auxiliary switch, wherein the second auxiliary switch, third resistor, and fourth resistor are configured to vary a voltage between the capacitor and the first resistor in response to the input of the auxiliary converter.

42. The auxiliary converter of claim 24, further comprising: a first diode coupled to the energy transfer element of the auxiliary converter to provide a path for current of the energy transfer element when the auxiliary power switch is off.

43. The auxiliary converter of claim 24, further comprising: ​ ​ a second diode coupled to the energy transfer element of the auxiliary converter and the output of the auxiliary converter, the second diode coupled to prevent current flow from the output of the auxiliary converter to the input of the auxiliary converter.

44. An auxiliary converter coupled to a primary power converter, comprising: an auxiliary power switch coupled to an input of the auxiliary converter, wherein the input of the auxiliary converter is coupled to receive a voltage generated by the primary power converter; a timing circuit coupled to receive a control signal from a controller of the primary power converter, wherein the controller of the primary power converter regulates an output of the primary power converter, the timing circuit configured to output an auxiliary drive signal to control switching of the auxiliary power switch and determine an on-time or off-time of the auxiliary power switch in response to the control signal; a blocking diode coupled to prevent current flow from an output of the auxiliary converter to the input of the auxiliary converter; and a first resistor coupled to the auxiliary power switch, the first resistor configured and coupled to provide current from the input of the auxiliary converter to the output of the auxiliary converter, wherein one end of the first resistor is coupled to a collector terminal of the auxiliary power switch and another end of the first resistor is coupled to the blocking diode, wherein the output of the auxiliary converter provides operating power to the controller of the primary power converter.

45. The auxiliary converter of claim 44, further comprising: a capacitor coupled to the first resistor; and a second resistor coupled to the first resistor, the capacitor and the first resistor configured to smooth current provided to the output of the auxiliary converter.

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