Flyback power converter primary side controller and method of operating same

Abstract

A circuit is disclosed. The circuit comprises a solid state switch controlled by a control circuit arranged to transition the solid state switch from a first on state to a first off state wherein in response to the transition, a plurality of resonant voltage valleys occur at a drain terminal of the solid state switch, the control circuit is further arranged to: determine an input power to the power converter circuit, and in response, determine a resonance voltage valley number based at least in part on the input power; and transitioning the solid-state switch from the first off state to a second on state when the order number of the plurality of resonance voltage valleys is equal to the number of resonance voltage valleys.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Patent Application Serial No. 63 / 672,142, “FLYBACK POWER CONVERTER PRIMARY SIDE CONTROLLER AND METHODS OF OPERATING THE SAME,” filed July 16, 2024, which is hereby incorporated by reference in its entirety for all purposes. TECHNICAL FIELD

[0003] The described implementations generally relate to power converters, and more specifically, the present implementations relate to flyback power converter primary side controllers and methods of operating the same. BACKGROUND

[0004] Electronic devices, such as computers, servers, and televisions, employ one or more electrical power conversion circuits to convert one form of electrical energy to another form of electrical energy. Some electrical power conversion circuits use a circuit topology known as a DC-DC converter to convert a high (or low) DC voltage to a lower (or higher) DC voltage. As many electronic devices are sensitive to the size and efficiency of the power conversion circuit, new types of power converters can provide relatively higher efficiency and smaller size for new types of electronic devices. SUMMARY

[0005] In some implementations, a circuit is disclosed. The circuit includes a transformer having a primary winding magnetically coupled to a secondary winding, the primary winding extending from a first terminal to a second terminal, the first terminal connected to a power source; a switch having a gate terminal, a source terminal, and a drain terminal, the drain terminal connected to the second terminal, the source terminal coupled to ground; and a controller circuit connected to the gate terminal and arranged to transition the switch from a first on state to a first off state, wherein in response to the transition, a plurality of resonant voltage valleys occur at the drain terminal, the controller circuit further arranged to: determine an input power at the first terminal, and in response, and based at least in part on the input power, determine a number of resonant voltage valleys; and transition the switch from the first off state to a second on state when a sequential number of the plurality of resonant voltage valleys is equal to the number of resonant voltage valleys.

[0006] In some implementations, the transition from the first off state to the second on state is made after a predetermined period of time.

[0007] In some embodiments, the number of resonant voltage valleys is a first number of resonant voltage valleys, the controller circuit is further arranged to determine a second number of resonant voltage valleys and to transition the switch to a third on state based at least in part on the second number of resonant voltage valleys.

[0008] In some embodiments, the transition to the third on state is made after the predetermined period of time.

[0009] In some embodiments, the determining the number of resonant voltage valleys includes comparing the determined input power to a predetermined threshold.

[0010] In some embodiments, the controller circuit includes a lookup table having a plurality of predetermined thresholds.

[0011] In some embodiments, the determining the input power includes sensing an input voltage at the first terminal, sensing a current flowing through the drain terminal to the source terminal, and calculating the input power based on the sensed input voltage and the sensed current.

[0012] In some embodiments, a power converter circuit is disclosed. The power converter circuit includes a solid state switch controlled by a control circuit, the control circuit arranged to transition the solid state switch from a first on state to a first off state, wherein in response to the transition, a plurality of resonant voltage valleys occur at a drain terminal of the solid state switch, the control circuit further arranged to: determine an input power to the power converter circuit, and in response, determine a number of resonant voltage valleys based at least in part on the input power; and transition the solid state switch from the first off state to a second on state when an ordinal number of the plurality of resonant voltage valleys is equal to the number of resonant voltage valleys.

[0013] In some embodiments, a method of operating a power converter circuit is disclosed. The method includes: providing a solid state switch in the power converter circuit; controlling, by a control circuit, the solid state switch to transition from a first on state to a first off state, wherein in response to the transition, a plurality of resonant voltage valleys occur at a drain terminal of the solid state switch; determining, by the control circuit, an input power to the power converter circuit; in response to determining the input power, determining a number of resonant voltage valleys based at least in part on the input power; and transitioning, by the control circuit, the solid state switch from the first off state to a second on state when an ordinal number of the plurality of resonant voltage valleys is equal to the number of resonant voltage valleys.

[0014] In some embodiments, the predetermined period of time has a zero value.

[0015] In some embodiments, the resonant voltage valley number is a first resonant voltage valley number, and the method further includes determining, by the control circuit, a second resonant voltage valley number, and controlling the solid state switch to transition to a third on state based at least in part on the second resonant voltage valley number.

[0016] In some embodiments, the determining the resonant voltage valley number includes comparing the determined input power to a predetermined threshold.

[0017] In some embodiments, determining the input power includes sensing an input voltage to the power converter circuit, sensing a current flowing through the drain terminal to source terminal of the solid state switch, and calculating the input power based on the sensed input voltage and the sensed current. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1A A schematic diagram of a quasi-resonant (QR) flyback converter circuit with a primary side controller is shown in accordance with embodiments of the disclosure. Figure 1B Operation of the primary switch of the QR flyback converter of Figure 1A is shown.

[0019] Figure 2 A schematic diagram of input power based valley lockout number selection in accordance with some embodiments of the disclosure is shown.

[0020] Figure 3 An example of a valley selection method for selecting a valley number to operate the primary switch of the QR flyback converter of Figure 1A is shown in accordance with certain embodiments.

[0021] Figure 4 A graph for determining a valley number in accordance with embodiments of the disclosure is shown.

[0022] Figure 5 A schematic diagram of a valley number selection and determination circuit that can be used to change the valley number is shown in accordance with certain embodiments.

[0023] Figure 6A and 6B A power converter with a circuit arranged to determine an input power using input voltage sensing is shown in accordance with certain embodiments. Figure 6A A controller circuit including a primary side controller co-packaged with a power switch is shown. Figure 6B An auxiliary voltage Vaux and voltage at the DMAG pin are shown; and

[0024] Figure 7 is a simplified flowchart showing a method of determining a valley number in a QR flyback converter based on a primary side input power in accordance with some embodiments of the disclosure. DETAILED DESCRIPTION

[0025] The circuits, apparatuses, and related technology disclosed herein generally relate to power converters. More specifically, the circuits, apparatuses, and related technology disclosed herein relate to a primary side controller for a flyback power converter and methods of operating the same. In some embodiments, input power delivered into a quasi-resonant (QR) flyback converter circuit can be monitored by a primary side controller and used to control the number of resonant voltage valleys for switching of a main switch. In various embodiments, the number of valleys for switching can be after a predetermined period of time. Embodiments of the present disclosure can reduce electromagnetic interference (EMI), thereby reducing audible noise. In some embodiments, a QR flyback converter can operate using resonant voltage valley switching to reduce switching losses of a main switch, where input power can be used to determine which valley will be used for switching.

[0026] In some embodiments, an input power lookup table on a primary side controller can be used to determine which resonant voltage valley will be used for operation of a QR flyback converter. The circuits and related technology disclosed herein can be used for various power converter circuits to perform efficient resonant voltage valley jumps. In some embodiments, the circuits and technology for updating the number of valleys can minimize rapid valley changes, thereby reducing audible noise. In various embodiments, a memory of a primary side controller of a QR flyback converter can include a lookup table with input power thresholds. The input power thresholds can be used to determine a resonant voltage valley for operating a QR flyback converter. In some embodiments, an externally adjustable component, such as but not limited to a resistor, can be used to set the power thresholds. In some embodiments, the number of valleys is updated when the monitored input power remains in a new range for a de-bounce time (e.g., 1 millisecond).

[0027] In various embodiments, a primary side controller can receive a first signal corresponding to an input voltage of a QR flyback converter and receive a second signal corresponding to a current flowing through a primary side main switch. The primary side controller can calculate an input power based on the input voltage and the current flowing through the primary side main switch. Based on the calculated input power, the primary side controller can determine an operating switching valley. In this way, the primary side controller can operate in a feed-forward mode that can respond relatively quickly to changes in the input voltage compared to a current method in which feedback from an output voltage can be used to provide feedback to the primary side controller.

[0028] In some embodiments, the disclosed QR flyback converter with one side input power valley number can utilize gallium nitride (GaN) power switches and / or circuitry. In various embodiments, the disclosed QR flyback converter can utilize silicon-based or silicon carbide-based power switches and / or circuitry. Various inventive embodiments are described herein, including methods, processes, systems, apparatuses, and the like.

[0029] Figure 1A A schematic diagram of a QR flyback converter circuit with one side controller according to embodiments of the disclosure is shown. As shown in FIG. 1, QR flyback converter circuit 100 can include transformer 135 with primary winding 110, secondary winding 120, and auxiliary winding 125. Secondary side winding 120 and auxiliary winding 125 can each have a winding direction opposite that of primary winding 110. In some embodiments, secondary side winding 120 and auxiliary winding 125 can each have a winding direction that is the same as that of primary winding 110. Primary winding 110 can be magnetically coupled to secondary winding 120 and magnetically coupled to auxiliary winding 125. Primary winding 110 can extend from first terminal 107 to second terminal 109. QR flyback converter circuit 100 can further include switch 115 having gate terminal 117, drain terminal 119, and source terminal 121. Drain terminal 119 can be connected to second terminal 109. Source terminal 121 can be connected to current sense device 155. Current sense device 155 can be connected to ground 102. Current sense device 155 can be arranged to sense a drain-to-source current in switch 115.

[0030] Input voltage 105 (v IN ) can be applied to primary winding 110 at first terminal 107. Switch 115 can be a gallium nitride (GaN)-based, silicon-based, or silicon carbide-based power switch. One side controller circuit 150 can be coupled to switch 115 at gate terminal 117. One side controller circuit 150 can be arranged to control an operational state of switch 115. QR flyback converter circuit 100 can generate output voltage 160 (v O ) at the secondary side winding. QR flyback converter circuit 100 can be arranged to operate using resonant voltage valley switching. One side controller circuit 150 can be arranged to determine an input power to the first terminal, compare the determined input power to a predetermined threshold, and control a number of operational valleys of the switch based on the comparison and a predetermined time period. In some embodiments, one side controller circuit 150 can include a lookup table having a plurality of predetermined thresholds.

[0031] Figure 1B Operation of switch 115 is shown. Figure 1BThe drain-to-source voltage of switch 115 is shown. Switch 115 can be turned on during time 0-1. At time 1, the switch can be turned off. During time 1-2, transformer 135 releases its stored magnetic energy, causing it to be fully discharged at time 2, which may lead to ringing behavior during time 2-4. The resonance observed between the primary winding 110 and switch 115 during times 2-4 can be seen in the drain-to-source voltage of switch 115. DS The QR flyback converter 100 can operate more efficiently when switch 115 is turned on at a trough instead of a peak. The first trough (n=1) occurs at time 3. Switch 115 can be turned on again at time 4 at the second trough (n=2).

[0032] The circuits and techniques disclosed herein can be used to determine the valley number. In some embodiments, the primary-side controller circuit 150 can determine the valley number based on the input power to the primary side. The primary-side controller 150 can calculate the input power based on the input voltage and the current through switch 115. The current through switch 115 can be sensed by current transmitting device 155. The primary-side controller circuit 150 can compare the calculated input power with a power threshold stored in a lookup table stored in the memory of the primary-side controller circuit 150. Based on the comparison result and a predetermined time period, the primary-side controller circuit 150 can adjust the operating valley number to have efficient operation to reduce losses and minimize emitted EMI and audible noise. In some embodiments, the predetermined time period has a zero value.

[0033] Figure 2 A schematic diagram illustrating valley lock-in number selection based on input power according to some embodiments of this disclosure is shown. For example... Figure 2 As shown, the valley number selector multiplexer 202 may include several inputs and outputs, the outputs of which can be arranged to generate a target valley number 204. The inputs to the multiplexer can be any number of valleys that can be used, such as n1, n2, n3 up to n... k The valley selector multiplexer 202 can also have a power input 206 (p) that can receive the value of the input power. IN Additional inputs to the multiplexer may include, but are not limited to, input voltages (V). IN ) and output voltage (V O Factors such as... The output of the valley-locked selector multiplexer can be the target valley number 204. Determining block 210 can be used to compare the target valley number 204 with the target valley number and determine whether to change the valley number or remain at the same switching valley number. Determining block 210 can receive input from the valley update / maintain control circuit. Determining block 210 can determine whether to update the valley number or maintain the original valley number, and can then generate an output for the currently set valley number 212.

[0034] Figure 3 An example of a valley selection method for selecting a valley number to operate the switch 115 is shown according to certain embodiments. The output power of a QR flyback converter can closely track to the input power of the converter. Figure 3 A graph of a QR flyback converter with output full load of 100% Po_Max is shown. The input power p IN The input power can be divided into 5 regions. Each region has a corresponding number of target valleys. The graph shows that for various power outputs, a unique valley number can be determined. The example shown can select 5 regions and a fixed power region range. In various embodiments, there is no limit to the range and number of power regions.

[0035] Figure 4 A graph for determining a valley number according to embodiments of the disclosure is shown. As Figure 4 shown, the input power 402 and the output power 404 are plotted as a function of time. As can be seen, the input power and the output power can closely track each other. When the input power is in the range of region 3 (406) and the hold time is exceeded, the target valley number will be set to n3, and the current number of the system can also be set to n3 (t < t1). When the input power changes from region 3 to region 2 (t = t1), the input power can enter the range of region 2, so the target valley number is set to n2, however the hold time of region 2 is not exceeded, so the currently set valley of the system can be maintained at the previous set value n3 (t = t1 to t2). When the input power stays in region 2 for more than the hold time, the currently set valley number of the system can be updated and reset to the target valley number n2 (t = t2).

[0036] The currently set valley number represents the current number of valleys in the system. The current number can also be referred to as the current number. The target valley number represents the number of valleys selected based on the input power region number. When t < t1, the output power p OUT may have a value close to the input power p IN in region 3. Therefore, the target valley number can be set to equal the current valley number, i.e. n = n3. When t1 < t < t2, the output power (and input power) can enter region 2, where the target valley number is n = n2, however the valley number of the power converter remains at n = n3 because p INthe de-bounce time period can have completed when the time is at t2. Thus, the valley number can change from n = n3 to n = n2. At the same time, the input power can change instantaneously due to the decrease in the number of valleys. In some embodiments, the latency of the system feedback response can be used to readjust the on-time (Ton) of the main switch to maintain a stable output. As long as the recovery time of this feedback response does not exceed the de-bounce time, the number of system valleys can remain at n = n2 (and not change to nl). When t3 < t < t4, the input power p OUT may have a value close to the input power p IN in the region 2. Thus, the target valley number can be set equal to the currently set valley number, i.e., n = n2. When t4 < t < t5, the input power p IN may enter the region 1 (410), and thus the target valley number can change to n = nl. The de-bounce timer is started again, and the currently set valley number can remain at n = n2 until the de-bounce time is met.

[0037] In some embodiments, it can be decided to update the valley number at each control cycle or PWM cycle. If the power is in a fixed region for a certain time period, then the valley number for that region can be updated. If the input power changes between regions, then the original valley number is maintained at the current number. The valley number can be kept in a region for a predetermined time period. In some embodiments, the predetermined time period can be the de-bounce time. In various embodiments, a de-bounce time of 1 millisecond can be used, however any other suitable de-bounce time is within the scope of the present disclosure. If the input power is in a power region for a predetermined time period (e.g., the de-bounce time), then the valley number is updated to that power region. In some embodiments, the valley number update method can include the input power (p IN ) staying in a fixed region for a predetermined time period, and then the valley number is changed to a new valley number. However, when Pin does not stay in a fixed region for a predetermined time period, then the previous valley number is maintained.

[0038] In various embodiments, the input power of the QR flyback converter can be continuously monitored by the primary side controller 150, and the operating resonant voltage valley can be selected based on the input power. As Figure 4As shown, when the input power 402 is in the 3rd region (406) and the hold-up time is exceeded, the target valley number can be set to n3, and the system's currently set valley number can also be set to n3 (t < t1). When the input power changes from the 3rd region to the 2nd region (408) (t = t1), the input power enters the 2nd region range, so the target valley number can be set to n2, however the hold-up time is not exceeded in the 2nd region, so the system's currently set valley can remain at the previous set value n3 (t = t1 to t2). When the input power stays in the 2nd region for the hold-up time, the system's currently set valley number can be updated and reset to the target valley number n2 (t = t2).

[0039] In some embodiments, when the switch 115 transitions from the on state to the off state, a series of resonant voltage valleys can occur at the drain terminal. The controller circuit 150 can be arranged to determine the input power at the input terminal 107, and in response, and based at least in part on the input power, determine a resonant voltage valley number, and transition the switch 115 from the first off state to the second on state when the sequential number of the series of resonant voltage valley numbers is equal to the resonant voltage valley number. The sequential number of the series of resonant voltage valley numbers is the number of valleys, e.g., 1, 2, 3,..., n. For example, the valley number 3 can be selected based on the input power. Thus, the sequential number is 3, and the power converter can operate using the valley number 3. When the input power changes (and after a predetermined time has elapsed), the valley number can change to a different number, e.g., 2, so the sequential number is 2.

[0040] In some embodiments, the selection of the valley can be determined based on an external resistor connected to the primary side controller 150. In some embodiments, the controller locks the valley (e.g., reuses the same valley number), and can change the valley lock periodically based on the input power. In this way, audible noise can be reduced, as the switching frequency can dither if the converter operates on a different valley each time it occurs, which can cause audible noise to increase.

[0041] In various embodiments, the primary side controller 150 can be arranged to calculate the input power based on the input voltage and i DS The input power is calculated as:

[0042] Power = V · I

[0043] p IN = v IN · i IN = v IN · < i DS >

[0044]

[0045] The method of calculating the average input power can be based on other calculation methods, and is not limited to the method shown above. Other suitable methods can be used, and are within the scope of the present disclosure. In some embodiments, i DS The average of pIN can be determined based on techniques that can not use integration followed by averaging. For example, any suitable value obtained by taking a midpoint or peak of a pin calculation is within the scope of the present disclosure. Various sampling techniques for sampling the input voltage and i DS Various sampling techniques for sampling the input voltage and i

[0046] Figure 5 A schematic of a valley number selection and determination circuit that can be used to change the valley number is shown, according to certain embodiments. The circuit 500 can include an input terminal 501 connected to an A / D converter 504. The A / D converter 504 is connected to a lookup table 506 having an output terminal 507. The output terminal 507 can be connected to a circuit 510 having an output terminal 511. The output terminal 511 can be connected to a one-shot circuit 514 having an output terminal 515. When the average of the input power pIN 502 is input to the A / D converter 504, a corresponding digital signal is generated according to the threshold of pIN, and sent to the lookup table 506 to determine the target valley number (implemented in binary code in some embodiments) corresponding to the current pIN. The target valley number can be input to the circuit 510, which is arranged to generate a D0_stable 512. When the target valley number binary code 508 maintains a stable state for a predetermined period of time (e.g., 1 millisecond), the one-shot circuit 514 can generate an updated CLK signal 516 to update the current target valley number to the current set 522 valley number. The D0_target 508 and the updated CLK 516 can be input to a flip-flop 518, which is arranged to generate a D0_current 520.

[0047] Figure 6A and 6B A power converter 600 having a circuit arranged to determine the input power using input voltage sensing is shown, according to certain embodiments. Figure 6A A controller circuit 602 including a primary side controller co-packaged with a power switch is shown. Figure 6BThe auxiliary voltage Vaux and the voltage at the DMAG pin 648 are shown. The primary side controller can be arranged to perform valley lock control as discussed above. The power switch can be silicon-based, or GaN-based, or silicon carbide-based. The primary winding 604 can have a first terminal 606 and a second terminal 608. The second terminal 608 can be connected to a drain pin of the controller circuit 602. The QR flyback converter circuit 600 can include a resistor 624 and a resistor 626 coupled between the auxiliary winding 630 and ground 640. During an input signal on period, the primary winding 604 can be magnetically coupled to the auxiliary winding 630, whereby a voltage Vaux can be generated at the auxiliary winding 630, where Vaux is equal to Vin. The pull current on the DMAG pin 648 can be clamped to 0 V, and i DMAG The input power can be proportional to Vin, so the input power can be determined:

[0048]

[0049] In some embodiments, other methods for input voltage detection can be utilized. These methods can use a packaged pin coupled to an input bulk capacitor to sense voltage or current. In various embodiments, iDMAG through a resistor can be used, and a transformer coupled to a bulk capacitor can be used so that the input voltage can be detected. In some embodiments, a high voltage (HV) pin can be used with an integrated resistive divider, where the resistive divider is connected to a bulk capacitor to sense the input voltage.

[0050] Figure 7 is a simplified flowchart showing a method for determining a number of valleys in a QR flyback converter based on primary side input power in accordance with some embodiments of the present disclosure. Referring to Figure 7 The method 700 for determining a number of valleys in a QR flyback converter based on primary side input power can include determining an input power to a power input terminal (702). The method further includes comparing the determined input power to a predetermined threshold (704). The method also includes selecting a first resonant voltage valley number based on the comparison (706), and controlling a state of a switch for a predetermined period of time using the first resonant voltage valley number (708). The method additionally determines whether the valley number has been updated based on the input power (710). If the valley number has been updated, the controller circuit can change the valley number to a new valley number (712), however if the valley number has not been updated, the controller circuit can continue to use the existing valley number (714).

[0051] It should be appreciated, Figure 7The specific steps illustrated in the flowchart of FIG. 6 provide particular methods of determining a valley number in a QR flyback converter based on primary side input power according to an embodiment of the present disclosure. Other sequences of steps can also be performed according to alternative embodiments. For example, embodiments of the present disclosure can perform the steps outlined above in a different order. Moreover, Figure 7 The various steps illustrated in the flowchart of FIG. 6 can include multiple sub-steps that can be performed in various sequences as appropriate to the individual steps. Furthermore, additional steps can be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0052] In some embodiments, the combination of circuits and methods disclosed herein can be used to provide valley number selection for operation of a flyback converter. Although the circuits and methods are described and illustrated herein with respect to several particular configurations of flyback converters, embodiments of the present disclosure are applicable to QR flyback converters, asymmetric half-bridge (AHB), and power factor correction circuits (PFC), or any power electronic conversion architecture with DCM operation.

[0053] In the foregoing specification, embodiments of the disclosure have been described with reference to a number of specific details that can vary depending on specific implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the disclosure, and what is intended by the applicants to be the scope of the disclosure, is the literal and equivalent scope of the claims as publicated in the application as filed, along with any subsequent correction by the USPTO. Specific embodiments can be practiced with the specific details set forth above or modifications thereof, or equivalents thereof, without departing from the spirit and scope of embodiments of the disclosure.

[0054] In addition, spatially relative terms, such as "bottom" or "top" or the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the devices in use or operation in addition to the orientations depicted in the figures. For example, if a device described herein is inverted or flipped over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The devices can be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0055] As used herein, the terms “and”, “or”, and “and / or” can include a variety of meanings that also are expected to depend, at least partly, on the context in which these terms are used. Typically, “or” if used to associate a list, such as A, B, or C, is intended to mean A, B, and C, here used in the inclusive sense, as well as A, B or C, here used in the exclusive sense. In addition, the term “one or more” as used herein can be used to describe any feature, structure, or characteristic in the singular or can be used to describe some combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example and claimed subject matter is not limited to this example. Furthermore, the term “at least one of’ if used in association with a list of items, such as A, B, or C, can be interpreted to mean any combination of A, B, and / or C, including A, B, C, AB, AC, BC, AA, AAB, ABC, AABBCCC, etc.

[0056] Reference throughout the specification to “one example”, “an example”, “certain examples” or “exemplary implementation” means that a particular feature, structure, or characteristic described in connection with the feature and / or example can be included in at least one feature and / or example of claimed subject matter. Thus, the appearance of the phrases “in one example”, “an example”, “in certain examples” or “in certain implementations” or other similar phrases in various places throughout this specification are not necessarily all referring to the same feature, example, and / or limitation. Furthermore, the particular features, structures, or characteristics can be combined in one or more examples and / or features.

[0057] In the preceding detailed description, numerous specific details have been set forth in order to provide a thorough understanding of the claimed subject matter. However, it will be understood by those skilled in the art that the claimed subject matter can be practiced without these specific details. In other instances, methods and apparatuses that would be known by one of ordinary skill have not been described in detail in order to not obscure the claimed subject matter. Accordingly, it is intended that the claimed subject matter not be limited by the particular illustrative examples described in this disclosure, but only by the claims.

Claims

1. A circuit, comprising: a transformer having a primary winding magnetically coupled to a secondary winding, the primary winding extending from a first terminal to a second terminal, the first terminal connected to a power source; a switch having a gate terminal, a source terminal, and a drain terminal, the drain terminal connected to the second terminal, the source terminal coupled to ground; and a controller circuit connected to the gate terminal and arranged to transition the switch from a first on state to a first off state, wherein in response to the transition, a plurality of resonant voltage valleys occur at the drain terminal, the controller circuit further arranged to: determine an input power at the first terminal, and in response, and based at least in part on the input power, determine a resonant voltage valley number; and transition the switch from the first off state to a second on state when an ordinal number of the plurality of resonant voltage valleys is equal to the resonant voltage valley number.

2. The circuit of claim 1, wherein the transition from the first off state to the second on state is made after a predetermined time period.

3. The circuit of claim 2, wherein the resonant voltage valley number is a first resonant voltage valley number, the controller circuit further arranged to determine a second resonant voltage valley number and transition the switch to a third on state based at least in part on the second resonant voltage valley number.

4. The circuit of claim 3, wherein the transition to the third on state is made after the predetermined time period.

5. The circuit of claim 4, wherein the predetermined time period has a zero value.

6. The circuit of claim 5, wherein the controller circuit comprises a lookup table having a plurality of predetermined threshold values.

7. The circuit of claim 1, wherein the determining the input power comprises sensing an input voltage at the first terminal, sensing a current flowing through the drain terminal to the source terminal, and calculating the input power based on the sensed input voltage and the sensed current.

8. A power converter circuit, comprising: a solid state switch controlled by a control circuit, the control circuit arranged to transition the solid state switch from a first on state to a first off state, wherein in response to the transition, a plurality of resonant voltage valleys occur at a drain terminal of the solid state switch, the control circuit further arranged to: determine an input power to the power converter circuit, and in response, based at least in part on the input power, determine a resonant voltage valley number; and transition the solid state switch from the first off state to a second on state when an ordinal number of the plurality of resonant voltage valleys is equal to the resonant voltage valley number.

9. The power converter circuit of claim 8, wherein the transition from the first off state to the second on state is made after a predetermined time period.

10. The power converter circuit of claim 8, wherein the number of resonant voltage valleys is a first number of resonant voltage valleys, the control circuit being further arranged to determine a second number of resonant voltage valleys and to transition the solid state switch to a third on state based at least in part on the second number of resonant voltage valleys.

11. The power converter circuit of claim 10, wherein the transition to the third on state is made after a predetermined period of time.

12. The power converter circuit of claim 8, wherein the determining the number of resonant voltage valleys includes comparing the determined input power to a predetermined threshold.

13. The power converter circuit of claim 12, wherein the control circuit includes a lookup table having a plurality of predetermined thresholds.

14. The power converter circuit of claim 8, wherein the determining the input power includes sensing an input voltage to the power converter circuit, sensing a current flowing through the drain terminal to source terminal of the solid state switch, and calculating the input power based on the sensed input voltage and the sensed current.

15. A method of operating a power converter circuit, the method comprising: providing a solid state switch in the power converter circuit; controlling, by a control circuit, the solid state switch to transition from a first on state to a first off state, wherein in response to the transition, a plurality of resonant voltage valleys occur at a drain terminal of the solid state switch; determining, by the control circuit, an input power to the power converter circuit; in response to determining the input power, determining a number of resonant voltage valleys based at least in part on the input power; and controlling, by the control circuit, the solid state switch to transition from the first off state to a second on state when a sequential number of the plurality of resonant voltage valleys is equal to the number of resonant voltage valleys.

16. The method of claim 15, wherein the transition from the first off state to the second on state is made after a predetermined period of time.

17. The method of claim 15, wherein the number of resonant voltage valleys is a first number of resonant voltage valleys, and the method further comprises determining, by the control circuit, a second number of resonant voltage valleys, and controlling the solid state switch to transition to a third on state based at least in part on the second number of resonant voltage valleys.

18. The method of claim 15, wherein determining the number of resonant voltage valleys includes comparing the determined input power to a predetermined threshold.

19. The method of claim 18, wherein the control circuit includes a lookup table having a plurality of predetermined thresholds.

20. The method of claim 15, wherein determining the input power includes sensing an input voltage to the power converter circuit, sensing a current flowing through the drain terminal to source terminal of the solid state switch, and calculating the input power based on the sensed input voltage and the sensed current.

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