Patent Application
20240195312
The described embodiments relate to synchronous rectifier power circuits.
Synchronous rectifier technology uses a low on-resistance metal oxide semiconductor field effect transistor MOSFET to replace the rectifier diode, which can effectively reduce the conduction loss of the converter. Synchronous rectifier circuits are widely used in switching power supplies to improve efficiency. Although they have a reduced loss in comparison to diode rectifiers they have losses associated with conduction and driving losses
In some embodiments a power conversion circuit comprises a transformer having a primary winding coupled to a secondary winding, wherein the primary winding is arranged to receive AC power from a power source and wherein the secondary winding is arranged to transfer power to a load, the secondary winding extending between a first terminal and a second terminal and including a tapped output disposed between the first and second terminals. A synchronous switch is disposed between the secondary winding and the load. A controller is arranged to operate the synchronous switch to rectify the power transferred to the load, the controller arranged to receive power from the tapped output.
In some embodiments the synchronous switch is formed from gallium nitride. In various embodiments the controller is formed from silicon. In some embodiments the synchronous switch and the controller are formed from gallium nitride and are monolithically formed on a single die. In various embodiments the power conversion circuit further comprises a diode positioned between the tapped output and the controller. In some embodiments the tapped output includes a fraction of a number of secondary winding turns. In various embodiments the secondary winding includes N turns between the first terminal and the second terminal and wherein the tapped output includes M turns between the first terminal and the tapped output, wherein M is less than N.
In some embodiments a power conversion circuit comprises a transformer having a primary winding arranged to receive power from a power source, a secondary winding arranged to transfer power to a load, and a tapped output arranged to transfer power to a controller circuit, wherein the secondary winding includes N turns between a first terminal and a second terminal and wherein the tapped output is formed from a portion of the secondary winding, the tapped output including M turns between the first terminal and the tapped output, where M is less than N. A synchronous switch disposed between the secondary winding and the load.
In some embodiments the controller circuit is arranged to operate the synchronous switch to rectify the power transferred to the load. In various embodiments the synchronous switch is formed from gallium nitride. In some embodiments the controller is formed from silicon. In various embodiments the synchronous switch and the controller are formed from gallium nitride and are monolithically formed on a single die. In some embodiments the conversion circuit further comprises a diode positioned between the tapped output and the controller circuit.
In some embodiments a method of operating a rectification circuit comprises receiving AC power at a primary winding of a transformer, coupling power from the primary winding of the transformer to a secondary winding of the transformer and rectifying power received from the secondary winding with a switch and transferring DC power to a load, wherein the switch is operated by a controller that receives power from a portion of the secondary winding.
In some embodiments the method further comprises receiving power at the controller from a tapped output of the secondary winding, wherein the secondary winding includes N turns between a first terminal and a second terminal and wherein the tapped output includes M turns between the first terminal and the tapped output, where M is less than N. In various embodiments the method further comprises a diode positioned between the tapped output and the controller circuit, the diode arranged to rectify power transferred to the controller. In some embodiments the synchronous switch is formed from gallium nitride. In various embodiments the controller is formed from silicon. In some embodiments the synchronous switch and the controller are formed from gallium nitride and are monolithically formed on a single die. In some embodiments the synchronous switch and the controller are co-packaged in a single electronic package.
To better understand the nature and advantages of the present disclosure, reference should be made to the following description and the accompanying figures. It is to be understood, however, that each of the figures is provided for the purpose of illustration only and is not intended as a definition of the limits of the scope of the present disclosure. Also, as a general rule, and unless it is evident to the contrary from the description, where elements in different figures use identical reference numbers, the elements are generally either identical or at least similar in function or purpose.
In the following description, various embodiments will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the embodiments may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.
Techniques disclosed herein relate generally to synchronous rectifier circuits. More specifically, techniques disclosed herein relate to self-powered synchronous rectifier circuits that operate with improved efficiency and have lower cost as compared to traditional synchronous rectifier circuits. Various inventive embodiments are described herein, including methods, processes, systems, devices, and the like.
For example, in some embodiments an AC source powers a primary winding of a transformer that couples energy to a secondary winding of the transformer according to a turns ratio of the number of primary turns to the number of secondary turns. A synchronous control circuit is powered from a tapped output off of the secondary winding where a voltage from the tapped output is less than a voltage across the secondary winding. The synchronous control circuit powers a synchronous switch that turns on and off to rectify the output of the secondary winding such that a DC voltage can be supplied to a load. The tapped output off of the secondary winding is more cost-efficient than providing an auxiliary winding to power the synchronous control circuit and provides improved control of the voltage supplied to the synchronous control circuit such that the switch can be driven efficiently.
In order to better appreciate the features and aspects of the present disclosure, further context for the disclosure is provided in the following section by discussing one particular implementation of a self-powered synchronous rectifier circuit that is powered off a portion of a secondary transformer winding according to embodiments of the disclosure. These embodiments are for explanatory purposes only and other embodiments may be employed in other types of circuits and/or electronic devices. For example, embodiments of the disclosure can be used with any type of circuit that converts power including but not limited to: flyback converters, active clam flyback converters, dual-tube flyback converters, asymmetric half-bridges, forward converters, dual-tube forward converters and LLC converters. In some instances, embodiments of the disclosure are particularly well suited for use with fast chargers the convert AC power to DC power for charging one or more electronic devices because of their potentially small form factor, low-cost and high efficiency.
Several illustrative embodiments will now be described with respect to the accompanying drawings, which form a part hereof. The ensuing description provides embodiment(s) only and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the embodiment(s) will provide those skilled in the art with an enabling description for implementing one or more embodiments. It is understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of this disclosure. In the following description, for the purposes of explanation, specific details are set forth in order to provide a thorough understanding of certain inventive embodiments. However, it will be apparent that various embodiments may be practiced without these specific details. The figures and description are not intended to be restrictive. The word “example” or “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or design described herein as “exemplary” or “example” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.
Output winding 118 has an alternating voltage that is coupled to a load 130 via a synchronous switch 124 that turns on and off to rectify the voltage supplied by the output winding such that the load receives a DC voltage. The synchronous switch 124 is controlled by the SRCC 110 that is “self-powered” by the transformer 112. More specifically output winding 118 includes a tapped output terminal 116 that includes a portion of the number of turns Ns of the output winding 118. Thus, a voltage at the tapped output terminal 116 is less than the voltage across the secondary winding 118. The tapped output terminal 116 is connected to a Vcc terminal 128 of the SRCC 110 via a diode 126. The SR 110 also includes a Vss terminal 120 connected to first terminal 119a of output winding 118 and a VD terminal 122 connected to load 130 where the synchronous switch 124 has a source terminal 133 coupled to the first terminal 119a and a drain terminal 134 coupled to the load 130. The SRCC 110 controls the synchronous switch 124 via gate terminal 132.
As described above, tapped output terminal 116 includes a portion of the number of turns of the secondary winding 118 and includes Nto turns. The voltage supplied to the Vcc terminal 128 by the tapped output terminal 116 is the ratio of the number of turns of the tapped output Nto divided by the number of turns of the primary winding Np times the input voltage Vp.
The voltage at tapped output terminal 116 will be lower voltage than the voltage across the secondary winding 118. The voltage at the tapped output terminal 116 is rectified by the diode 126 and drives the Vcc terminal 128 of the SRCC 110.
The transformer 112 has an inverted polarity such that when the input voltage Vp 104 is positive the voltage across the output winding 118 is negative. Similarly, the voltage at output tap 116 is also negative, however it has a higher voltage than the Vss 120 connection of the SRCC 110. The diode 126 will be forward biased since the anode is positive with respect to the cathode generating the voltage Vcc 128 input to the SRCC 110. When the input voltage Vp 104 is negative the output of the tapped output 116 will be positive and the diode 126 will be reverse biased. The synchronous switch 124 will be in an on state and the full voltage of the secondary winding 118 will be present at the load 130.
In some embodiments the synchronous switch 124 is a semiconductor switch formed from silicon, gallium nitride, silicon carbide, gallium arsenide, diamond or other suitable semiconductor material. In various embodiments the synchronous switch 124 is a MOSFET, a HEMT, a PHEMT or other suitable type of semiconductor device.
In some embodiments the SRCC 110 is a semiconductor circuit formed from silicon, gallium nitride, silicon carbide, gallium arsenide, diamond or other suitable semiconductor material. In various embodiments the synchronous switch 125 is made from gallium nitride and the SRCC 110 is made from silicon. In other embodiments the synchronous switch 125 is made from gallium nitride and the SRCC 110 is made from gallium nitride. In some embodiments the synchronous switch 125 is made from gallium nitride and is monolithically formed on a single die with the SRCC 110 which is also made from gallium nitride. In various embodiments the synchronous switch 125 is formed on a first die and co-packaged with the SRCC 110 that is formed on a second die.
In contrast to
The transformer may be configured as a flyback transformer that stores energy though a first half cycle and releases it in a second half cycle. A flyback transformer stores energy in its primary winding magnetics and releases it through the secondary. In this way a flyback transformer operates as a pair of coupled inductors. When the input Vin 310 goes positive the switch 316 closes and charges both the mutual inductance and the leakage inductance of the primary winding 314. During this period the diode 334 is forward biased because the voltage of the tap 318 is higher than the voltage of the SRCC 328 reference node Vss 326. The diode produces a half wave rectified voltage Vcc 320 powering the SRCC 328 controller circuit. When Vin 310 becomes negative, the switch 316 is opened. The secondary 322 becomes positive while the primary windings 314 stored energy discharges. The stored energy is output through the secondary 322. The secondary becoming positive reverse biases the diode 334. The synchronous switch 330 closes when the switch 316 is opened so that power flows from the secondary to the output. It is important that the switch 316 and synchronous switch 330 operate in a complementary fashion. When 316 is closed synchronous switch 330 is open and when 316 is closed synchronous switch 330 is open. When the synchronous switch 330 is closed the output voltage Vo 324 in parallel with the output capacitance 328 is equal to the voltage across the entire secondary winding Ns 322.
By using a synchronous rectifier for its output, the losses associated with a diode rectification are replaced by the on resistance of the synchronous switch 330 and its driving loss. The driving loss is significantly reduced by the use of the tap 318 to produce a low voltage Vcc 320 magnitude.
Flyback converter circuit 400 operates in a manner similar to the converter circuit 300 of
While the input source is positive, the switch 414 closes. When the switch 414 closes the primary winding 314 stores energy by ramping the current of the primary winding magnetics. The primary winding magnetics consists of its coupling inductance and a leakage inductance. During this period the secondary winding 322 is negative. The tap 318 voltage is positive with respect to the SRCC 328 common node 326 Vd and forward biases the diode 334. The diode 334 half-wave rectifies the voltage at the tap to produce the voltage input Vcc 320 of the SRCC 328. While the switch 414 remains closed, the switch 412 and synchronous switch 330 are open. When the switch 414 is opened, the primary 314 winding discharges through the secondary 322. The energy stored in the mutual inductance is transferred to the secondary. However, the energy stored in the leakage inductance can be lost. The clamp capacitance 410 is used to recapture the energy of the leakage inductance. When switch 414 opens switch 412 closes so that the energy stored in the leakage inductance is that stored in the capacitor. It also has a smoothing effect of the voltage across the switch. The synchronous switch 330 is controlled by the Vg 332 output of the SRCC 328.
The secondary 322 has Ns windings and has a tapped output 318 that connects to the secondary a number of windings from the end. The voltage across the tapped output 318 is lower than a voltage across the entire secondary winding 322. The top of the secondary 322 is connected to the common point 326 Vss of the SRCC 328 and is also connected to the source of synchronous switch 330. The tap 318 is connected to the anode of diode 334. The cathode of diode 324 is connected to the Vcc 320 input of the SRCC 328. The drain of synchronous switch 330 is connected to the Vdd 336 input of the SRCC 328 and is connected to the positive rail of Vout 324. Vout is in parallel with the output capacitor 328. Switch 330 is controlled by the Vg output 332 of the SRCC 328.
The switches 514 and 516 close connecting the winding 518 across Vin 510. The inductances of the primary winding 518 store energy ramping up the magnetic flux. The diode 334 is forward biased producing a half wave rectified Vcc 320 and the synchronous switch 330 is open. Switches 514 and 516 open when the magnetization reaches a desired level. The energy stored in the magnetization inductance of the primary winding 518 drains into the secondary winding 322. The secondary winding 322 changes polarity reverse biasing diode 334. The full voltage of the secondary drives Vo 324. When the switches 514 and 516 open the voltage at each side of the winding is clamped to within one diode drop of the rails of Vin 510 relieving the stress across switches 514 and 516.
Asymmetric half-bridge converter circuit 600 operates as a resonant converter and uses inductance 610, and 612 along with capacitance 614. The inductor 612 represents the inductance of the primary winding 620. The circuit has an input voltage 602 and a parallel input capacitance 604. The cycle begins with closing of switch 616 which charges the resonant input circuit. The diode 334 is forward biased, and the synchronous switch 330 and switch 618 are open. The switch 616 is then opened and switch 618 is closed and the current circulates through the resonant circuit. When switch 618 is closed the energy from the resonant circuit is transferred though the magnetics to reverse bias the diode 334. The synchronous switch 330 is closed so that the full voltage of the secondary is applied to the output voltage Vo 324. This is a general description of the operation of the circuit in
Forward converter circuit 700 operates by the switch 722 closes causing current to flow through the primary winding 714. The transformer causes current to flow through the secondary winding also. This causes the diode 744 to reverse bias. The synchronous switch 730 is shorted to allow the full voltage of the secondary to cause current to flow through inductor 734 to ramp its current producing an output voltage Vo. Switch 736 is open. When the switch 722 is opened the synchronous switch 730 is also open. Switch 736 is closed as a free-wheeling device so that the inductor 734 can continue to conduct current as it slowly decays. Switch 720 is closed so that the energy in the leakage inductance of the primary winding can be dissipated through the winding 718. This protects the switch from a voltage stress due to the opening of switch 722. The diode 744 is forward biased producing a voltage which powers the Vcc 742 input of the SRCC 728 electronics.
The converter circuit 800 operates by switch 814 and switch 816 closing allowing the input voltage to cause current to flow in the primary winding 818. The transformer is designed so that when the input to the primary winding is positive the output of the secondary winding is also positive which reverse biases the diode 744. The synchronous switch 730 is closed by the gate drive 732. The voltage output of the secondary charges the inductor 734 and supplies the output voltage Vo 740. Switch 736 is open. When the switches 814 and 816 open the voltage stress is applied over the two switches reducing the stress than it would be with just one switch. When switches 816 and 814 open the diodes D1820 and D2822 clamp the voltage on the switches to be within one diode drop of each rail. When switch 814 and switch 816 open the synchronous switch 730 opens and switch 736 closes. Switch 736 closes to allow the inductor to continue to conduct current as a freewheeling device without the associated diode voltage drop. The diode DA 744 forward biases and supplies the voltage Vcc 742 to power the SRCC electronics.
The converter circuit 900 operates such that switch 916 closes so that Vin 910 charges the inductor Lr 918 in series with the primary winding 920 and the capacitor Cr 922. The voltage on the secondaries 930 and 932 is the same phase of the voltage on the primary 920. When the voltage on the secondary 930 is positive the diode Da 950 is reverse biased. When the secondary NS2932 is positive switch SR2948 closes and Vo 944 is driven by the second secondary Ns2932. When the switch SW1916 opens switch Sw2914 is closed so that the resonant current can circulate through the inductor Lr 918 the winding 920 and the capacitor Cr 922. When the voltage across the primary is negative the output of the secondary is negative. The synchronous switch 938 is closed and synchronous switch 954 is open. The first secondary drives the output voltage 944. The synchronous switch cross-connects the output voltage Vo 944 so that the negative output voltage of the first secondary is reversed. The output voltage Vo 944 is positive when the output of the first secondary is negative. Vo 944 is a full wave rectified output of the two secondaries. When the first secondary is negative diode Da 950 is forward biased and produces a half wave rectified Vcc 952 derived from the tap 936 voltage.
For simplicity, various peripheral components, such as decoupling capacitors and other electronic components of the power conversion circuits are not shown in the figures.
In the foregoing specification, embodiments of the disclosure have been described with reference to numerous specific details that can vary from implementation to 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 set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. The specific details of particular embodiments can be combined in any suitable manner without departing from the spirit and scope of embodiments of the disclosure.
Additionally, spatially relative terms, such as “bottom or “top” and the like can be used to describe an element and/or feature's relationship to another element(s) and/or feature(s) as, for example, illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and/or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as a “bottom” surface can then be oriented “above” other elements or features. The device can be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
Terms “and,” “or,” and “an/or,” as used herein, may include a variety of meanings that also is expected to depend at least in part upon the context in which such 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 may be used to describe any feature, structure, or characteristic in the singular or may 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 to associate a list, such as A, B, or C, can be interpreted to mean any combination of A, B, and/or C, such as A, B, C, AB, AC, BC, AA, AAB, ABC, AABBCCC, etc.
Reference throughout this 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 may be included in at least one feature and/or example of claimed subject matter. Thus, the appearances of the phrase “in one example,” “an example,” “in certain examples,” “in certain implementations,” or other like 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 may be combined in one or more examples and/or features.
In some implementations, operations or processing may involve physical manipulation of physical quantities. Typically, although not necessarily, such quantities may take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, or otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to such signals as bits, data, values, elements, symbols, characters, terms, numbers, numerals, or the like. It should be understood, however, that all of these or similar terms are to be associated with appropriate physical quantities and are merely convenient labels. Unless specifically stated otherwise, as apparent from the discussion herein, it is appreciated that throughout this specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” or the like refer to actions or processes of a specific apparatus, such as a special purpose computer, special purpose computing apparatus or a similar special purpose electronic computing device. In the context of this specification, therefore, a special purpose computer or a similar special purpose electronic computing device is capable of manipulating or transforming signals, typically represented as physical electronic or magnetic quantities within memories, registers, or other information storage devices, transmission devices, or display devices of the special purpose computer or similar special purpose electronic computing device.
In the preceding detailed description, numerous specific details have been set forth to provide a thorough understanding of claimed subject matter. However, it will be understood by those skilled in the art that claimed subject matter may 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 so as not to obscure claimed subject matter. Therefore, it is intended that claimed subject matter not be limited to the particular examples disclosed, but that such claimed subject matter may also include all aspects falling within the scope of appended claims, and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202211598349.0 | Dec 2022 | CN | national |
| 202211600509.0 | Dec 2022 | CN | national |
This application claims priority to U.S. provisional patent application Ser. No. 63/486,942, for “SYNCHRONOUS RECTIFIER CIRCUIT POWERED BY POWER WINDINGS” filed on Feb. 24, 2023, which claims priority to commonly assigned Chinese provisional patent application Serial No. 202211598349.0, for “SYNCHRONOUS RECTIFIER CIRCUIT POWERED BY POWER WINDINGS,” filed on Dec. 12, 2022 and Serial No. 202211600509.0, for “SYNCHRONOUS RECTIFIER CIRCUIT POWERED BY AUXILIARY WINDINGS,” filed on Dec. 12, 2022. This application is also related to the following concurrently filed and commonly assigned U.S. patent application Ser. No. ______ entitled “POWER CONVERTERS HAVING SYNCHRONOUS RECTIFIER CIRCUITS POWERED BY AUXILIARY WINDINGS,” filed Dec. 6, 2023 (Atty. Docket No. 096868-1353393-006912US), the contents of all of which are hereby incorporated by reference in their entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63486942 | Feb 2023 | US |
