Feed-forward boost converter for flyback switch-mode power supply and method thereof

Abstract

Various embodiments relate to a flyback SMPS comprising a primary side controller on a primary side, a first switch on the primary side, a transformer comprising a primary side winding on the primary side, a secondary side winding on a secondary side, and an auxiliary winding on the primary side connected to a first switching regulator, wherein the first switching regulator is powered from the auxiliary winding during a primary stroke when the first switch is turned on.

Description

Technical Field

[0001] The present disclosure relates generally to switched mode power supplies ("SMPS") and, more particularly, but not exclusively, to a feed-forward boost converter for a flyback SMPS. Background Art

[0002] An SMPS is a known electronic power supply that uses a switching regulator to convert electrical power as efficiently as possible.

[0003] Therefore, to optimize the efficiency of the SMPS, it is advantageous to power the controller's integrated circuit ("IC") from a low voltage.

[0004] When supplying a high voltage to the controller IC, an internal series regulator is required, which results in increased losses. In addition, with an internal series regulator, the dissipation within the IC becomes higher. Summary of the invention

[0005] A brief overview of various embodiments is presented below. Embodiments address the need to create a feed-forward boost converter for a flyback SMPS.

[0006] To overcome these and other shortcomings of the prior art, and in view of the need to create a boost mode converter for flyback SMPS feedforward, a brief summary of various exemplary embodiments is presented. Some simplifications and omissions may be made in the following summary, which is intended to highlight and introduce some aspects of the various exemplary embodiments, rather than to limit the scope of the invention.

[0007] A detailed description of preferred exemplary embodiments suitable for enabling one of ordinary skill in the art to make and use the inventive concept will follow in the following sections.

[0008] Various embodiments described herein relate to a flyback switch mode power supply comprising a primary side controller on a primary side, a first switch on the primary side, a transformer comprising a primary side winding on the primary side, a secondary side winding on a secondary side, and an auxiliary winding on the primary side connected to a first switching regulator, wherein the first switching regulator is powered from the auxiliary winding during a primary stroke when the first switch is turned on.

[0009] In an embodiment of the present disclosure, the flyback SMPS further includes the transformer, the transformer including a secondary auxiliary winding connected to a second switching regulator at the secondary side, wherein the second switching regulator is powered from the secondary auxiliary winding during a primary stroke.

[0010] In an embodiment of the present disclosure, the flyback SMPS further includes a startup resistor connected to the first switching regulator at the primary side.

[0011] In an embodiment of the present disclosure, the flyback SMPS further includes a second switch on the secondary side, the second switch being driven by the second switching regulator having an integrated synchronous rectification controller.

[0012] In an embodiment of the present disclosure, the first switching regulator and the second switching regulator are boost regulators.

[0013] In an embodiment of the present disclosure, the boost regulator includes a pulse width modulator regulator, a switch, a rectifier diode, an inductor, and an output capacitor.

[0014] In an embodiment of the present disclosure, the PWM regulator is configured to regulate the internal operating voltage of the boost regulator to a fixed voltage greater than or equal to the input voltage of the boost regulator.

[0015] In an embodiment of the present disclosure, a source of the switch of the boost regulator is grounded.

[0016] Various embodiments described herein relate to a method for powering a controller using a flyback switch mode power supply, the SMPS comprising a primary side controller on a primary side, a first switch on the primary side, a transformer, the transformer comprising a primary side winding on the primary side, a secondary side winding on the secondary side, and an auxiliary winding on the primary side connected to a first switching regulator, the method comprising the steps of turning on the first switch, and supplying power to the first switching regulator from the auxiliary winding during a primary stroke.

[0017] In an embodiment of the present disclosure, the method for powering a controller using a flyback SMPS, the SMPS includes the transformer, the transformer includes a secondary auxiliary winding connected to a second switching regulator on the secondary side, and the method further includes: powering the second switching regulator from the secondary auxiliary winding during the primary stroke.

[0018] In an embodiment of the present disclosure, the method for powering a controller using a flyback SMPS further includes connecting a startup resistor on the primary side to the first switching regulator.

[0019] In an embodiment of the present disclosure, the method for powering a controller using a flyback SMPS further includes driving a second switch on the secondary side by the second switching regulator having an integrated synchronous rectification controller.

[0020] In an embodiment of the present disclosure, the first switching regulator and the second switching regulator are boost regulators.

[0021] In an embodiment of the present disclosure, the boost regulator includes a pulse width modulator regulator, a switch, a rectifier diode, an inductor, and an output capacitor.

[0022] In an embodiment of the present disclosure, the PWM regulator is configured to regulate the internal operating voltage of the boost regulator to a fixed voltage greater than or equal to the input voltage of the boost regulator.

[0023] In an embodiment of the present disclosure, a source of the switch of the boost regulator is grounded. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings and the following detailed description are incorporated into and form a part of the specification and are used to further illustrate embodiments of the concepts embodying the claimed invention and to explain various principles and advantages of those embodiments. In the accompanying drawings, like reference numerals refer to the same or functionally similar elements in various views.

[0025] These and other more detailed and specific features are more fully disclosed in the following specification, with reference to the accompanying drawings, in which:

[0026] Figure 1 shows a timing diagram of a flyback SMPS for smart charging applications;

[0027] Figure 2 A circuit diagram of a flyback SMPS for charging applications with a primary side forward supply is shown;

[0028] Figure 3 Shows Figure 2 A timing diagram of a flyback SMPS for a charging application having a primary side forward supply;

[0029] Figure 4 shows a circuit diagram of the present embodiment for a smart charger application having a buck-type SMPS for primary-side power supply;

[0030] Figure 5 A circuit diagram of a smart charger application with a startup resistor is shown;

[0031] Figure 6 shows a circuit diagram of the present embodiment for a smart charger application with a startup resistor and primary stroke power supply by a boost SMPS;

[0032] Figure 7 shows a circuit diagram of the current embodiment with primary stroke powering by a boost SMPS on both the primary and secondary sides; and

[0033] Figure 8 A circuit diagram of the present embodiment for a smart charger application with primary stroke charging by a boost SMPS with synchronous rectification on both the primary and secondary sides is shown. DETAILED DESCRIPTION

[0034] It should be understood that the drawings are merely schematic and not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to indicate the same or similar parts.

[0035] Description and accompanying drawings illustrate the principle of various example embodiments. It will therefore be appreciated that those skilled in the art will be able to design various arrangements, which, although not explicitly described or shown herein, embody the principle of the present invention and are included within its scope. In addition, all examples listed herein are primarily intended to be used for teaching purposes to help readers understand the principle of the present invention and the concept that the inventors contribute to promote this area, and should be interpreted as not being limited to such specific examples and conditions. In addition, unless otherwise specified (e.g., "otherwise" or "or replaceable"), the term "or" as used herein refers to non-exclusive or (i.e., and / or). Moreover, the various embodiments described herein are not necessarily mutually exclusive, because some embodiments can be combined with one or more other embodiments to form new embodiments. Descriptors such as "first", "second", "third", etc. do not mean to limit the order of the elements discussed, but are used to distinguish an element from the next element, and are generally interchangeable.

[0036] An isolated flyback SMPS for smart charging applications includes an alternating current ("AC") mains supply that powers the circuit on the primary side. The AC mains supply is connected to an input capacitor via a bridge rectifier diode.

[0037] The primary side of the circuit contains the SMPS controller IC, which drives the MOSFET switch, and through the transformer, energy is transferred to the output capacitor.

[0038] The output voltage is controlled by a controller IC on the secondary side via a signal transformer. The output voltage setting is usually set by a smartphone or tablet via a USB connection.

[0039] The input and output sides are galvanically isolated by two transformers on the primary and secondary sides of the circuit.

[0040] The controller IC on the primary side is powered by the auxiliary winding of the transformer.

[0041] The internal operating voltage of the controller IC on the primary side is generated by an internal series regulator.

[0042] Figure 1A timing diagram 100 of a flyback SMPS for smart charging applications is shown.

[0043] The timing diagram 100 includes separate timing diagrams for the gate 1101 , the drain 1102 , and the auxiliary winding 103 .

[0044] In a flyback converter, the input switch is turned on, and while it is on, energy is stored in transformer T1 during the primary stroke 104 .

[0045] During the secondary stroke 105, energy is released to the secondary side through the rectifier diode. In addition, during the secondary stroke 105, energy is also fed to V via the auxiliary winding using the rectifier diode. cc In capacitor.

[0046] The voltage across the auxiliary winding 103 during the primary stroke 104 is equal to equation 106, which is: N a / N p ×V in . N p Defined as the number of turns in the primary transformer winding. N a Defined as the number of turns of the auxiliary transformer winding. V in Defined as the input voltage.

[0047] The voltage across the auxiliary transformer winding 103 during the secondary stroke 105 is equal to equation 107, which is: N a / N s ×(V out +V diodc6 ). s Defined as the number of turns in the secondary transformer winding. V out Defined as the output voltage. V diode6 Defined as the forward voltage of diode D6.

[0048] The auxiliary transformer winding voltage during the secondary stroke 105 is used to power the primary side controller IC. Therefore, V cc The voltage across the capacitor is equal to N a / N s ×(V out +V diode6 )-V diode5 , where V diode5 is defined as the forward voltage of diode D5.

[0049] Since V cc =N a / N s ×(V out +V diode6 )-V diode5 , so the change in output voltage will also change Vcc voltage. For the minimum output voltage setting, V cc must be high enough to power the primary side controller IC. For the maximum output voltage setting, V cc will be much higher than required, resulting in additional losses inside the controller IC.

[0050] For example, a USB Type-C smart charger adapter supports an approximate output voltage range between 3V and 20V.

[0051] If the primary side controller IC and diode D5 have a minimum V cc The voltage is 10V, and the forward voltage of the diode D6 is 0.7V, so Na / Ns=(10+0.7) / (3+0.7)=2.89.

[0052] In V out =20V, V cc =N a / N s ×(V out +V diode6 )-V diode5 =59V.

[0053] Therefore, V cc The voltage is much higher than required and most of the energy to power the primary-side controller IC is dissipated in the required internal series regulator.

[0054] If the internal series regulator is regulating to the minimum required voltage of 10V, then V out = 20V, approximately 83% of the energy used to power the primary-side controller IC is dissipated in the internal series regulator. In addition, V cc The voltage will increase at higher output loads because the peak of the high frequency ringing voltage 108 on the auxiliary winding 103 will cause V cc The capacitor is charged to an even higher voltage.

[0055] The high frequency ringing voltage 108 is caused by the leakage inductance of the transformer. cc The voltage can be raised by up to an additional 50%. Therefore, the maximum V cc The voltage may be 59V+50%=88V.

[0056] In normal operation, the power supplied by the primary side is low (only up to about 2% of the output power), but this dissipation in the primary side controller IC may become too high to keep the primary side controller IC below its maximum operating temperature.

[0057] Furthermore, in high power density chargers where the total efficiency from input to output exceeds 90%, losses of about 2% are significant (i.e., 90% efficiency means 10% losses. The 2% losses used to power the primary side IC are a significant portion of the 10%). Therefore, in order to limit V cc supply voltage range, it is advantageous to power the primary-side IC during the primary stroke (ie, feed-forward) rather than during the secondary stroke.

[0058] Figure 2 A circuit diagram 200 of a flyback SMPS for charging applications with a primary side forward supply is shown.

[0059] The isolated flyback SMPS for smart charging applications comprises an alternating current (“AC”) mains 202 that powers a circuit 200 at a primary side 203 . The AC mains 202 is connected to an input capacitor 206 via a bridge rectifier diode 205 .

[0060] The primary side 203 contains a primary side controller IC 207 which drives a MOSFET switch 208 and through a transformer 209, energy is transferred to an output capacitor 210. The output voltage 211 is controlled by a secondary side controller IC 212 on the secondary side 204 through a signal transformer 213. The output voltage 211 setting is typically set by a smartphone or tablet through a USB connection 214.

[0061] The input side and the output side are electrically isolated by the transformer 209 on the primary side 203 and the transformer 213 on the secondary side 204. The primary side controller IC 207 on the primary side 203 is powered by the auxiliary winding 201 of the transformer 209.

[0062] The internal operating voltage of IC 207 on the primary side 203 is generated by an internal series regulator 215 .

[0063] exist Figure 2 , the polarity of the auxiliary winding 215 is reversed.

[0064] Figure 3 Shows Figure 2 A timing diagram 300 of a flyback SMPS for a charging application with a primary side forward supply is shown.

[0065] V cc The voltage is now equal to Equation 301, which is defined as N a / N p ×V in -V diode5 .

[0066] For a universal mains input adapter, the input voltage range is about 85Vac to 264Vac. Therefore, the rectified mains peak voltage is equal to √2×85 to √2×264, which is about 120V to 373V.

[0067] During operation of a universal mains input adapter, there will be a 120Hz ripple on the capacitor on the primary side (with a 60Hz mains). Under maximum load conditions, the lowest voltage on the capacitor on the primary side may be about 70V.

[0068] For V cc When the minimum is 10V, N a / N p Calculated at the minimum input voltage (10+0.7) / 70=0.15. For the maximum input voltage: V cc =N a / N p ×V in -V diode5 =56V.

[0069] If the primary stroke is used for power supply, the peak rectification will have little effect. The losses in the internal series regulator will be reduced as the maximum voltage drops from 88V to 56V.

[0070] To reduce the losses in the power supply regulator, an SMPS can be used to generate the internal operating voltage, which means that the linear regulator is replaced by a switching regulator. The switching regulator can be a buck topology or a boost topology. Other topologies such as buck-boost, switched capacitor or any other topology are also possible.

[0071] Figure 4 A circuit diagram 400 of the present embodiment is shown for a smart charger application having a buck-type SMPS for primary-side power supply.

[0072] The step-down switching regulator is integrated in the primary side controller IC 401 of the primary side 402 .

[0073] The buck switching regulator includes a PWM regulator 404 , a switch 405 , a rectifier diode 406 , an inductor 407 , and an output capacitor 408 .

[0074] PWM regulator 404 converts V int 409 is regulated to be lower than or equal to the input voltage V cc Voltage of 410 V int The voltage 409 may be a fixed voltage or may depend on operating conditions. At low loads, the drive voltage of switch 411 and gate 1412 may be lower because the peak current through switch 411 is lower at low loads. Therefore, at low loads, V int409 is adjusted to a lower voltage.

[0075] In the current embodiment, a boost SMPS is preferred over a buck SMPS.

[0076] An example of this advantage of the boost type over the buck type is that the boost SMPS requires only one additional IC pin (i.e., pin SW). In contrast, the buck SMPS requires an additional IC pin and an additional V cc Pins. Low pin count is good for SMPS.

[0077] Another example of this advantage of the boost type over the buck type is that the maximum internal IC voltage is equal to V int +V diode7 (See Figure 4 ). Because the maximum voltage of small feature size IC processes is limited, it is beneficial for the maximum internal IC voltages to be equal.

[0078] For example, for a step-down SMPS, V cc Must be at least the required minimum V int voltage. Therefore, if a minimum of 10V is required, if the V in = 373V during the primary stroke supply V cc , then the maximum V cc will be 56V.

[0079] For example, for a boost SMPS, the maximum V cc The voltage is V int +V diode7 =10.7V. Therefore, for V cc =N a / N p ×V in -V diode5 =10.7V, at V in =373V, then N a / N p =0.03. At V in =70V, minimum V cc The voltage will be V cc =N a / N p ×V in -V diode5 =1.4V. Therefore, for a boost SMPS, the V in voltage, generating a V between 1.4V and 10.7V cc voltage and generates a fixed 10V V int voltage, which is suitable for high-density IC processes.

[0080] Another example of this advantage of the boost type over the buck type is the switch S2 (see Figure 6 ) is connected to ground, so it is connected to the high voltage V cc Switch S2 405 (see Figure 4 ) is easier to drive.

[0081] As shown, by using the present embodiment, the losses in the primary side supply are reduced by a factor of about three. In addition, the maximum voltage on the IC is reduced from 88V to 10.7V.

[0082] The overall efficiency of the smart charger is improved and the dissipation in the primary-side IC is significantly reduced, allowing for a higher power density charger and a smaller primary-side IC package.

[0083] Figure 5 A circuit diagram 500 of a smart charger application with a startup resistor is shown.

[0084] Figure 5 5 is a circuit diagram 500 including a startup resistor R2501. If there is no high voltage startup circuit inside the IC, startup is performed using an external (high ohmic) resistor.

[0085] A high voltage startup circuit allows for fast startup and low standby power of the charger, however, requires a high voltage IC process which increases the cost and is therefore not preferred.

[0086] To initially start up the primary side IC, V cc 502 is charged to a startup voltage that is several volts higher than the minimum supply voltage (for example, if the minimum supply voltage is 10V, then V cc 502 is charged to 15V). When the smart charger starts switching, V out 503 is initially zero, so the voltage N a / N s ×(V out +V diode6 )-V diode5 will be approximately zero.

[0087] Therefore, V cc 502 is not initially powered from auxiliary winding 504. Only when V out When 503 reaches the minimum level, the auxiliary winding 504 takes over V cc 502 power supply.

[0088] In V out Before 503 rises to the minimum level, the supply current comes from V cc 502 capacitor C Vcc 505. V cc Capacitor C Vcc 505 requires several microfarads toout 503 does not reach its minimum level during V cc 502. When the charger starts, the output capacitor C2 506 is charged to the minimum output voltage level, which takes about a few milliseconds.

[0089] When V cc Capacitor C Vcc When 505 is a few microfarads and the starting resistor R2 501 is about several megohms, V cc It may take one second for the 502 voltage to reach its starting voltage of 15V. Therefore, it may take one second for the smart charger to start running after it is plugged into the mains.

[0090] Figure 6 A circuit diagram 600 of the current embodiment is shown for a smart charger application with a startup resistor and primary stroke power supply with a boost SMPS.

[0091] In the current embodiment, since the primary side 601 is powered during the primary stroke, the power supply from the auxiliary winding 603 takes over the power supply at the first switching cycle.

[0092] C Vcc 604 Charge to N a / N p ×V in -V diode5 . C Vint The capacitor 605 can be a relatively small value (e.g., 100 nF). vint 605, so start-up after plugging the smart charger into the AC mains 606 occurs almost immediately (ie, less than 100 milliseconds).

[0093] If the maximum allowed start-up time is about one second (which is typical for charger applications), R2607 may also be a larger value (e.g., 20 megohms instead of 2 megohms). A larger value for R2607 can reduce losses during standby operation of the smart charger.

[0094] When the AC mains 606 is 230V, the loss in the 2 megohm resistor is about (230×√2) 2 / 2meg = 53 milliwatts. For a 20 megohm resistor, these losses drop to 5 milliwatts. So, to optimize the efficiency of the power supply on the secondary side, a similar concept can be used.

[0095] Figure 7 A circuit diagram 700 of the current embodiment is shown with primary stroke powering with a boost SMPS on both the primary and secondary sides.

[0096] exist Figure 7In the embodiment of the present invention, an additional secondary auxiliary winding 701 is included, and a boost converter including PWMregSec 702 , an inductor L2 703 , a switch S3 704 and a diode D9 705 is included on the secondary side 706 .

[0097] The secondary side 706 is connected from V int Sec 707 power supply. V out 708 connection is used to measure and control the output voltage V out 708. Since the maximum output voltage of the secondary side 706 is lower than the maximum output voltage of the primary side 709, the efficiency advantage is lower than that of the primary side.

[0098] Figure 8 A circuit diagram 800 of the present embodiment is shown for a smart charger application having a primary stroke powered by a boost SMPS with synchronous rectification on both the primary and secondary sides.

[0099] exist Figure 8 In the rectifier diode D6 710 (see Figure 7 , Figure 8 The synchronous rectifier switch S4 801 is replaced by the synchronous rectifier switch S4 801. The switch S4 801 is driven by a secondary side controller IC (IC2 802) with an integrated synchronous rectifier controller (SRctrl 803).

[0100] At the lowest output voltage of the smart charger (i.e., 3V), if only 3V is supplied to gate 4804, switch S4801 will not be driven to the lowest on-state resistance. Using the boost converter from the current embodiment, V int Sec 805 adjusts to a voltage that drives switch S4 801 to a minimum on-state resistance.

[0101] At the highest output voltage of the smart charger (i.e., 20V), when the boost converter from the current embodiment is added, the gate 4 804 can be driven with an optimal voltage. Without the boost converter, an integrated linear regulator is required to reduce the 20V output voltage to a voltage (e.g., 5V to 8V) to drive the switch S4 801.

[0102] Integrating a linear regulator will increase the power dissipated in IC2802, and a boost regulator can be used to increase V int Sec 805 voltage regulator is used to drive the synchronous rectifier switch S4 801, which is independent of the output voltage V out 806 constant voltage.

[0103] By implementing the current embodiment, the losses within the primary and secondary IC controllers are reduced by approximately six times, the maximum IC voltage is reduced by eight times, and the standby power loss is reduced by two times. In addition, the overall efficiency of the smart charger can be improved by up to approximately 0.15%.

[0104] It should be apparent from the foregoing description that various exemplary embodiments of the present invention can be implemented in hardware. In addition, various exemplary embodiments can be implemented as instructions stored on a non-transitory machine-readable storage medium, such as a volatile or non-volatile memory, which can be read and executed by at least one processor to perform the operations described in detail herein. The non-transitory machine-readable storage medium can include any mechanism for storing information in a machine-readable form, such as a personal or laptop computer, a server, or other computing device. Therefore, the non-transitory machine-readable storage medium can include a read-only memory (ROM), a random access memory (RAM), a magnetic disk storage medium, an optical storage medium, a flash memory device, and similar storage media, and does not include a transient signal.

[0105] It should be understood by those skilled in the art that any block diagram herein represents a conceptual diagram of an illustrative circuit that embodies the principles of the present invention. Similarly, it should be recognized that any flow chart, flow chart, state transition diagram, pseudo code, etc. represent various processes that can be substantially represented in a machine-readable medium and thereby executed by a computer or processor, whether or not such a computer or processor is explicitly shown.

[0106] Therefore, it should be understood that the above description is intended to be illustrative and not restrictive. After reading the above description, many embodiments and applications other than the examples provided will be apparent. The scope should be determined with reference to the appended claims and the full range of equivalents to which such claims are entitled, rather than with reference to the above description or the following summary. It is anticipated and expected that future developments will occur in the technology discussed herein, and the disclosed systems and methods will be incorporated into such future embodiments. In short, it should be understood that the present application is capable of modification and variation.

[0107] Benefits, advantages, solutions to problems, and any one or more elements that may make any benefit, advantage, or solution occur or become more significant should not be construed as critical, required, or essential features or elements of any or all the claims. The present invention is defined solely by the appended claims, including any amendments made during the pendency of this application and all equivalents of those claims as issued.

[0108] Unless expressly indicated to the contrary herein, all terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by persons skilled in the art described herein. Specifically, unless a claim recites an express limitation to the contrary, use of singular articles such as "a," "an," "the," and "said" should be understood to describe one or more of the indicated elements.

[0109] An abstract of the present disclosure is provided to allow the reader to quickly determine the nature of the technical disclosure. The abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the aforementioned detailed description, it can be seen that various features are combined together into various embodiments for the purpose of connecting the present disclosure as a whole. The method of the present disclosure is not to be interpreted as reflecting the intention that the claimed embodiments require more features than those explicitly stated in each claim. On the contrary, as reflected in the following claims, the inventive subject matter lies in less than all the features of a single disclosed embodiment. Therefore, the following claims are hereby incorporated into the detailed description, wherein each claim itself represents a separate claimed subject matter.

Claims

1. A flyback switch mode power supply, characterized in that: It includes: A primary side controller on the primary side; a first switch on the primary side; as well as A transformer comprising a primary winding on the primary side, a secondary winding on the secondary side, and an auxiliary winding on the primary side connected to a first switching regulator, wherein When the first switch is turned on, the first switching regulator is powered from the auxiliary winding during a primary stroke, the first switching regulator being a step-up regulator; The boost regulator is used to increase the secondary supply voltage V int Sec is adjusted to a voltage for driving the second switch on the secondary side to a minimum on-state resistance.

2. The flyback switch mode power supply according to claim 1, characterized in that: It further includes: the transformer comprising a secondary auxiliary winding connected to a second switching regulator on the secondary side, wherein The second switching regulator is powered from the secondary auxiliary winding during the primary stroke.

3. The flyback switch mode power supply according to claim 1, characterized in that: It further includes: A startup resistor connected to the first switching regulator on the primary side.

4. The flyback switch mode power supply according to claim 2, characterized in that: It further includes: A second switch on the secondary side is driven by the second switching regulator with an integrated synchronous rectification controller.

5. The flyback switch mode power supply according to claim 2, characterized in that: The second switching regulator is a step-up regulator.

6. The flyback switch mode power supply according to claim 5, characterized in that: The boost regulator includes a pulse width modulator (PWM), a switch, a rectifier diode, an inductor and an output capacitor.

7. The flyback switch mode power supply according to claim 6, characterized in that: The PWM regulator is configured to regulate an internal operating voltage of the step-up regulator to a fixed voltage greater than or equal to an input voltage of the step-up regulator.

8. The flyback switch mode power supply according to claim 7, characterized in that: A source of the switch of the step-up regulator is connected to ground.

9. A method for powering a controller using a flyback switch mode power supply, characterized in that: The switch mode power supply comprises a primary side controller on the primary side, a first switch on the primary side, a transformer comprising a primary side winding on the primary side, a secondary side winding on the secondary side, and an auxiliary winding on the primary side connected to a first switching regulator, the method comprising the following steps: Turning on the first switch, and supplying power to the first switching regulator from the auxiliary winding during the primary stroke; the first switching regulator being a step-up regulator; The boost regulator is used to increase the secondary supply voltage V int Sec is adjusted to a voltage for driving the second switch on the secondary side to a minimum on-state resistance.

10. The method for powering a controller using a flyback switch mode power supply according to claim 9, characterized in that: The switched mode power supply comprises the transformer, the transformer comprising a secondary auxiliary winding connected to a second switching regulator on the secondary side, the method further comprising: The second switching regulator is powered from the secondary auxiliary winding during the primary stroke.

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