Synchronous rectification controller, switching power supply
By switching transistors and transferring charge, the size and efficiency issues of synchronous rectifier controller power supply methods are solved, achieving high-efficiency power supply and output voltage sampling, improving system energy conversion efficiency and reducing application costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUXI CHIPOWN MICROELECTRONICS
- Filing Date
- 2023-01-16
- Publication Date
- 2026-07-03
AI Technical Summary
Existing synchronous rectifier controllers suffer from problems such as increased transformer size, increased cost, or severe losses affecting efficiency, especially in high-side synchronous rectification applications where EMI performance is poor.
By switching between switching transistors, the synchronous rectifier controller is efficiently powered through charge transfer. The power switching transistor and synchronous rectifier control circuit are integrated into a single chip, and energy transfer is achieved by connecting the energy storage capacitor and the power supply capacitor in parallel.
It improves the system's energy conversion efficiency, reduces the system's application size and cost, and enables sampling of the output voltage in high-side applications.
Smart Images
Figure CN116094339B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of switching power supply technology, specifically to a synchronous rectification controller and a switching power supply. Background Technology
[0002] In recent years, with the increasing market demand for power supply chips, flyback switching power supplies have been widely used due to their unique structure, lower cost, and smaller size. Traditional diode rectification suffers from a large forward voltage drop, which significantly reduces power supply efficiency. To improve conversion efficiency, power MOSFETs are used instead of diodes for rectification, controlled by a synchronous rectification controller. In synchronous rectification low-side applications, EMI (Electromagnetic Interference) is poor. Although common-mode noise can be canceled by the transformer shielding layer, more turns are required. High-side applications, on the other hand, have better EMI performance. Therefore, in fast charging applications, planar transformers (i.e., transformers with high frequency, low profile, small height, and high operating frequency) are preferred for high-side structures.
[0003] Figure 1 and Figure 2 Two configurations for high-side power supply of existing synchronous rectifier controllers are shown.
[0004] like Figure 1 The diagram shown is a schematic of the circuit structure of an existing high-side synchronous rectifier controller powered by an auxiliary winding. This circuit mainly includes a power circuit and a control circuit, wherein the power circuit includes transformer T1 and primary-side power transistors. Secondary rectifier power transistor Diode D0; the control circuit is a synchronous rectifier controller 101. In the primary side power transistor... When turned on, through the input source For the primary winding of transformer T1 Charge and store energy, when disconnect, When the circuit is turned on, energy is induced to the secondary winding through the mutual inductance of the transformer T1 windings. And on the auxiliary winding Naux, the auxiliary winding Naux stores energy in capacitor C1 through diode D0, and capacitor C1 supplies power to the synchronous rectifier controller.
[0005] like Figure 2 The diagram shown is a schematic of the circuit structure of an existing high-side synchronous rectifier controller that uses a self-powered drain circuit. This circuit also includes a power circuit and a control circuit, wherein the power circuit includes a transformer T2 and a primary-side power switch transistor. Secondary rectifier power transistor The control circuit is a synchronous rectifier controller 201. First, the primary-side power switching transistor... The circuit is turned on, storing energy in the primary winding of transformer T2. Above; next should Closed, second side When conducting, the primary winding Energy is sensed in the secondary winding. At this time, the power supply of the secondary synchronous rectifier controller 201 is provided by the output capacitor C0 storing energy in C2 through the internal voltage regulation circuit of the synchronous rectifier controller to provide a stable power supply to the synchronous rectifier controller 201.
[0006] Both of the above methods provide power to the high-side synchronous rectification, but they also have several problems, mainly the following two:
[0007] (1) Figure 1 The power supply method adds an auxiliary winding for power supply, which not only increases the size of the transformer and reduces the integration, but also increases the application cost.
[0008] (2) Figure 2 The energy from the output capacitor C0 is transferred to capacitor C2, which then powers the synchronous rectifier controller. Although no auxiliary winding is added, this self-powered method suffers from significant losses, severely impacting the system's efficiency. Summary of the Invention
[0009] This invention provides a synchronous rectifier controller and a switching power supply to improve energy conversion efficiency and achieve efficient power supply.
[0010] Therefore, the embodiments of the present invention provide the following technical solutions:
[0011] On one hand, embodiments of the present invention provide a synchronous rectification controller, the synchronous rectification controller including: a power switch Q0, a drive circuit 303, a power supply control circuit 304, and a switching circuit; the switching circuit includes: a first switch Q1, a second switch Q2, a third switch Q3, and a fourth switch Q4;
[0012] The first switching transistor Q1 is connected to the third output terminal of the power supply control circuit 304;
[0013] The third switch Q3 is connected to the first output terminal of the power supply control circuit 304;
[0014] The second switch Q2 and the fourth switch Q4 are respectively connected to the second output terminal of the power supply control circuit 304;
[0015] The drive circuit 303 is used to control the power switch Q0 to turn on or off, so that the synchronous rectifier controller can perform synchronous rectification or stop synchronous rectification.
[0016] The power supply control circuit 304 is used to control the on or off of each power supply switch in the switching circuit.
[0017] Optionally, the power switch Q0, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 are all NMOS transistors.
[0018] Optionally, the power switch Q0 and the first switch Q1 are integrated on a single silicon chip and integrated with a synchronous rectification control circuit that does not contain high-voltage devices on a single chip.
[0019] Optionally, the source of the power switch Q0 is connected to the internal ground GND, the drain of the power switch Q0 is connected to the external power supply VD, and the gate of the power switch Q0 is connected to the driving circuit 303.
[0020] Optionally, the gate of the first switch Q1 is connected to the third output terminal of the power supply control circuit 304; the source of the first switch Q1 is connected to the source of the second switch Q2; and the drain of the first switch Q1 is connected to external ground VSS.
[0021] The gate of the second switching transistor Q2 is connected to the second output terminal of the power supply control circuit 304, and the drain of the second switching transistor Q2 is connected to the internal ground GND.
[0022] The gate of the third switch Q3 is connected to the second output terminal of the power supply control circuit 304, the source of the third switch Q3 is connected to the internal ground GND, and the drain of the third switch Q3 is connected to the source of the fourth switch Q4.
[0023] The gate of the fourth switch Q4 is connected to the second output terminal of the power supply control circuit 304, and the drain of the fourth switch Q4 is connected to the internal power supply VDD.
[0024] On the other hand, embodiments of the present invention also provide a switching power supply, the switching power supply including a transformer, a charge transfer circuit, and the aforementioned synchronous rectification controller;
[0025] During the demagnetization phase of the transformer, the drive circuit 303 controls the power switch Q0 to turn on, enabling the synchronous rectifier controller to perform synchronous rectification, and the energy stored on the transformer is transferred to the charge transfer circuit.
[0026] During the excitation phase of the transformer, the drive circuit 303 controls the power switch Q0 to disconnect, causing the synchronous rectifier controller to stop synchronous rectification, and the charge transfer circuit supplies power to the synchronous rectifier controller.
[0027] Optionally, the power switch Q0 is connected to the high-voltage side of the secondary winding of the transformer;
[0028] The charge transfer circuit includes: a power supply capacitor C3 and an energy storage capacitor C4;
[0029] The power supply capacitor C3 is connected between the internal ground GND and the internal power supply VDD.
[0030] The energy storage capacitor C4 is connected between the source of the first switch Q1 and the source of the third switch Q3;
[0031] During the demagnetization phase of the transformer, the energy stored on the transformer is transferred to the energy storage capacitor C4;
[0032] During the excitation phase of the transformer, the energy on the energy storage capacitor C4 is transferred to the power supply capacitor C3 for storage, and the power supply capacitor C3 provides power to the synchronous rectifier controller.
[0033] Optionally, during the demagnetization phase of the transformer, the first output terminal of the power supply control circuit 304 outputs a high level, the second output terminal of the power supply control circuit 304 outputs a low level, the third switch Q3 is turned on, and the second switch Q2 and the fourth switch Q4 are turned off.
[0034] During the excitation phase of the transformer, the first output terminal of the power supply control circuit 304 outputs a low level, the second output terminal of the power supply control circuit 304 outputs a high level, the third switch Q3 is turned off, and the second switch Q2 and the fourth switch Q4 are turned on.
[0035] Optionally, the power switch Q0 is connected to the low-voltage side of the transformer secondary winding; the charge transfer circuit includes: an energy storage capacitor C4;
[0036] The energy storage capacitor C4 is connected between the internal power supply VDD and the internal ground GND.
[0037] During the demagnetization phase of the transformer, the second output terminal of the power supply control circuit 304 outputs a high level, and the fourth switching transistor Q4 is turned on; the energy stored on the transformer is transferred to the energy storage capacitor C4.
[0038] During the excitation phase of the transformer, the second output terminal of the power supply control circuit 304 outputs a low level, the fourth switch Q4 is turned off, and the energy storage capacitor C4 supplies power to the synchronous rectifier controller.
[0039] Optionally, the voltage across the energy storage capacitor C4 is the same as the output voltage of the transformer. It has a proportional relationship.
[0040] The synchronous rectifier controller and switching power supply provided in this invention achieve efficient power supply by switching between switching transistors and transferring charge, thereby improving the system's energy conversion efficiency.
[0041] Furthermore, integrating the high-voltage power supply switch and the power switch onto a single silicon chip, along with a synchronous rectification control circuit that does not contain high-voltage components, not only improves the reliability of the invention but also significantly reduces the system application size and effectively lowers application costs.
[0042] Furthermore, the synchronous rectifier controller provided in this embodiment of the invention can also be used to sample the output voltage in high-side applications.
[0043] Furthermore, the synchronous rectifier controller provided in this embodiment of the invention can be applied not only to the high-voltage side of the secondary side of the transformer, but also to the low-voltage side of the secondary side of the transformer. Attached Figure Description
[0044] Figure 1 This is a schematic diagram of the circuit structure of an existing high-side synchronous rectifier controller that uses auxiliary winding power supply;
[0045] Figure 2 This is a schematic diagram of the circuit structure of an existing high-side synchronous rectifier controller that uses drain-side self-powered power.
[0046] Figure 3 This is a schematic block diagram of the synchronous rectification controller provided in an embodiment of the present invention;
[0047] Figure 4 This is a schematic diagram of a specific structure of the synchronous rectifier controller provided in an embodiment of the present invention;
[0048] Figure 5 This is a schematic diagram of a switching power supply provided in an embodiment of the present invention;
[0049] Figure 6 yes Figure 5 The diagram shows a specific structure of a switching power supply.
[0050] Figure 7 yes Figure 6 The diagram shows the operating waveforms of the synchronous rectifier controller in the switching power supply.
[0051] Figure 8 This is another schematic diagram of the switching power supply provided in an embodiment of the present invention;
[0052] Figure 9 yes Figure 8 The diagram shows a specific structure of a switching power supply. Detailed Implementation
[0053] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0054] like Figure 3 The diagram shown is a schematic block diagram of the synchronous rectification controller provided in an embodiment of the present invention.
[0055] The synchronous rectification controller 300 includes: a power switch Q0, a drive circuit 303, a power supply control circuit 304, and a switching circuit 305; the switching circuit 305 includes multiple power supply switches. Wherein:
[0056] The drive circuit 303 is used to control the power switch Q0 to turn on or off, so that the synchronous rectification controller 300 can perform synchronous rectification or stop synchronous rectification.
[0057] The power supply control circuit 304 is used to control the on or off of each power supply switch in the switching circuit 305.
[0058] like Figure 4 The diagram shown is a specific structural schematic of a synchronous rectifier controller provided in an embodiment of the present invention.
[0059] In this embodiment, Figure 1 The switching circuit 305 includes: a first switching transistor Q1, a second switching transistor Q2, a third switching transistor Q3, and a fourth switching transistor Q4;
[0060] The first switching transistor Q1 is connected to the third output terminal ON3 of the power supply control circuit 304;
[0061] The third switch Q3 is connected to the first output terminal ON1 of the power supply control circuit 304;
[0062] The second switch Q2 and the fourth switch Q4 are respectively connected to the second output terminal ON2 of the power supply control circuit 304.
[0063] In a non-limiting embodiment, the power switch Q0, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 can all be NMOS transistors.
[0064] To save system application size, such as Figure 4 As shown, the power switch Q0 and the first switch Q1 can be integrated on a single silicon chip, and this part can be used as the power and supply module 301.
[0065] Taking an NMOS transistor as an example, the following will be combined with... Figure 4 Explain the specific connection method for each NMOS transistor.
[0066] like Figure 4 As shown, the source of the power switch Q0 is connected to the internal ground GND, the drain of the power switch Q0 is connected to the external power supply VD, and the gate of the power switch Q0 is connected to the driving circuit 303.
[0067] The gate of the first switch Q1 is connected to the third output terminal of the power supply control circuit 304; the source of the first switch Q1 is connected to the source of the second switch Q2; the drain of the first switch Q1 is connected to the external ground VSS.
[0068] The gate of the second switching transistor Q2 is connected to the second output terminal of the power supply control circuit 304, and the drain of the second switching transistor Q2 is connected to the internal ground GND.
[0069] The gate of the third switch Q3 is connected to the first output terminal of the power supply control circuit 304, the source of the third switch Q3 is connected to the internal ground GND, and the drain of the third switch Q3 is connected to the source of the fourth switch Q4.
[0070] The gate of the fourth switch Q4 is connected to the second output terminal of the power supply control circuit 304, and the drain of the fourth switch Q4 is connected to the internal power supply VDD.
[0071] Accordingly, this embodiment of the invention also provides a switching power supply. By utilizing the aforementioned synchronous rectifier controller, efficient power supply of the synchronous rectifier controller can be achieved, thereby improving the system's energy conversion efficiency.
[0072] It should be noted that, in practical applications, the synchronous rectifier controller provided in this embodiment of the invention can be applied to the high-side or low-side of the secondary winding of a transformer, which will be described in detail below.
[0073] like Figure 5 The diagram shown is a structural schematic of a switching power supply provided in an embodiment of the present invention.
[0074] In this embodiment, the synchronous rectification controller 300 is applied to the high side of the secondary winding of transformer T3. The switching power supply includes transformer T3, charge transfer circuit, and the aforementioned synchronous rectification controller 300.
[0075] Figure 5 middle, and These are the primary winding and secondary winding of transformer T3, respectively. A primary power transistor is installed on the primary winding of transformer T3. .capacitance This is the filter capacitor at the output terminal of transformer T3. This is the output voltage of transformer T3. It is the primary input source for transformer T3.
[0076] In this embodiment, the power switch Q0 and the first switch Q1 can be integrated together as the power and power supply module 301, and the drive circuit 303, the power supply control circuit 304, and the other three switches can be integrated together as the power supply setting module 302.
[0077] During the demagnetization phase of the transformer T3, the drive circuit 303 controls the power switch Q0 to turn on, so that the synchronous rectifier controller 300 performs synchronous rectification, and the energy stored on the transformer T3 is transferred to the charge transfer circuit.
[0078] During the excitation phase of the transformer T3, the drive circuit 303 controls the power switch Q0 to disconnect, causing the synchronous rectifier controller 300 to stop synchronous rectification, and the charge transfer circuit supplies power to the synchronous rectifier controller 300.
[0079] In this embodiment, the charge transfer circuit includes a power supply capacitor C3 and an energy storage capacitor C4.
[0080] The power supply capacitor C3 is connected between the internal ground GND and the internal power supply VDD.
[0081] The energy storage capacitor C4 is connected between the source CN of the first switch Q1 and the drain CP of the third switch Q3.
[0082] During the demagnetization phase of the transformer, the energy stored on the transformer is transferred to the energy storage capacitor C4;
[0083] During the excitation phase of the transformer, the energy on the energy storage capacitor C4 is transferred to the power supply capacitor C3 for storage, and the power supply capacitor C3 provides power to the synchronous rectifier controller 300.
[0084] To further explain the operation of this switching power supply Figure 6 A specific structure of this switching power supply is shown.
[0085] Reference Figure 6 The working process of this switching power supply is as follows:
[0086] primary power transistor When turned on, through the input source For the primary winding of transformer T3 Energy is stored during charging, and transformer T3 enters the excitation stage; when the primary power transistor... When disconnected, transformer T3 enters the demagnetization stage, and energy is induced to the secondary winding through the mutual inductance of transformer T3 windings. superior.
[0087] When transformer T3 enters the demagnetizing stage, the drive circuit 303 outputs a high level, controlling the power switch Q0 to conduct, causing the secondary winding of transformer T3 to begin rectification. At this time, the third output terminal ON3 of the power supply control circuit 304 outputs a high level, controlling the first switch Q1 to conduct, and the first output terminal ON1 outputs a high level, controlling the third switch Q3 to conduct. The second output terminal ON2 outputs a low level, controlling the second switch Q2 and the fourth switch Q4 to turn off, forming a path from the same-name terminal of the secondary winding of transformer T3 through the third switch Q3 and capacitor C4 to the external ground VSS. This path stores the demagnetizing stage in the secondary winding of transformer T3. Part of the energy is transferred to the energy storage capacitor C4 for temporary storage. This process not only transfers the charge but also makes the voltage across the energy storage capacitor C4 equal to the output voltage of the transformer T3. It has a proportional relationship, thus enabling control over the output voltage. Sampling.
[0088] When transformer T3 enters the excitation stage, drive circuit 303 outputs a low level, controlling power switch Q0 to turn off. Synchronous rectifier controller 300 does not perform rectification. At this time, power supply control circuit 304 outputs a low level at its third output terminal, controlling the first switch Q1 to turn off. The first output terminal ON1 outputs a low level, controlling the third switch Q3 to turn off. The second output terminal ON2 outputs a high level, controlling the second switch Q2 and the fourth switch Q4 to conduct. This forms two paths on energy storage capacitor C4. The first path connects the lower plate of energy storage capacitor C4 to external ground GND via the conduction of the second switch Q2. The second path connects the upper plate of energy storage capacitor C4 to the internal power supply VDD via the conduction of the fourth switch Q4. During this stage, energy storage capacitor C4 is connected in parallel with power supply capacitor C3, thus achieving charge sharing. The energy stored in energy storage capacitor C4 during the demagnetization stage is transferred to power supply capacitor C3 for storage, thus powering synchronous rectifier controller 300.
[0089] Figure 7 yes Figure 6 The diagram shows the operating waveforms of the synchronous rectifier controller in the switching power supply.
[0090] Between times t0 and t1, transformer T3 enters the demagnetization stage. At this time, drive circuit 303 outputs a high level, controlling power switch Q0 to conduct. Ideally, after power switch Q0 is turned on, the voltage difference between its drain and source is 0, meaning the source node VD voltage of the power switch is zero. Power supply control circuit 304 outputs a low level at its second output terminal ON2, and simultaneously outputs a high level at its first output terminal ON1 and third output terminal ON3. This disconnects the second and fourth switches Q2 and Q4, while turning on the first and third switches Q1 and Q3. At this time, some energy from transformer T3 begins to charge energy storage capacitor C4. At time t1, the voltage across energy storage capacitor C4... Reaching a maximum voltage.
[0091] During the transition from time t1 to t2, transformer T3 switches to the excitation stage. At this time, power switch Q0 is disconnected due to receiving a low-level signal from the drive circuit 303. Therefore, the voltage drop from the drain to the source of power switch Q0 becomes the output voltage. Due to the voltage drop to ground, the second output terminal ON2 of the power supply control circuit 304 outputs a high level during this stage, while the first output terminal ON1 and the third output terminal ON3 simultaneously output a low level. This causes the second switch Q2 and the fourth switch Q4 to conduct, while the first switch Q1 and the third switch Q3 are turned off. At this time, the energy storage capacitor C4 and the power supply capacitor C3 are in parallel. During the t0 to t1 stage, the energy stored in the energy storage capacitor C4 is transferred to the power supply capacitor C3, and the voltage VDD on the power supply capacitor C3 reaches its maximum at this time. Since it is also necessary to supply power to the synchronous rectifier controller 300, the voltage VDD on the power supply capacitor C3 will decrease during the t1 to t2 stage.
[0092] like Figure 8 The diagram shown is a schematic diagram of another principle of the switching power supply provided in an embodiment of the present invention.
[0093] In this embodiment, the synchronous rectification controller 300 is applied to the low side of the secondary winding of transformer T3. The switching power supply includes transformer T4, charge transfer circuit, and the aforementioned synchronous rectification controller 300.
[0094] Figure 8 middle, and These are the primary and secondary windings of transformer T4, respectively. A primary power transistor is installed on the primary winding of transformer T4. .capacitance This is the filter capacitor at the output terminal of transformer T4. This is the output voltage of transformer T4. It is the primary input source for transformer T4.
[0095] In this embodiment, the power switch Q0 and the first switch Q1 can also be integrated together as the power and power supply module 301, and the drive circuit 303, the power supply control circuit 304, and the other three switches can be integrated together as the power supply setting module 302.
[0096] During the demagnetization phase of the transformer T4, the drive circuit 303 controls the power switch Q0 to turn on, so that the synchronous rectifier controller 300 performs synchronous rectification, and the energy stored on the transformer T4 is transferred to the charge transfer circuit.
[0097] During the excitation phase of the transformer T4, the drive circuit 303 controls the power switch Q0 to disconnect, causing the synchronous rectifier controller 300 to stop synchronous rectification, and the charge transfer circuit supplies power to the synchronous rectifier controller 300.
[0098] In this embodiment, the charge transfer circuit includes: an energy storage capacitor C4; the energy storage capacitor C4 is connected between the internal power supply VDD and the internal ground GND;
[0099] During the demagnetization phase of the transformer, the second output terminal ON2 of the power supply control circuit 304 outputs a high level, and the fourth switch Q4 is turned on; the energy stored on the transformer T4 is transferred to the energy storage capacitor C4.
[0100] During the excitation phase of the transformer, the second output terminal ON2 of the power supply control circuit 304 outputs a low level, the fourth switch Q4 is turned off, and the energy storage capacitor C4 supplies power to the synchronous rectifier controller 300.
[0101] To further explain the operation of this switching power supply Figure 9 A specific structure of this switching power supply is shown.
[0102] Reference Figure 9 The working process of this switching power supply is as follows:
[0103] primary power transistor When turned on, through the input source For the primary winding of transformer T4 Energy is stored during charging, and transformer T4 enters the excitation stage; when the primary power transistor... When disconnected, transformer T4 enters the demagnetization stage, and energy is induced to the secondary winding through the mutual inductance of transformer T4 windings. superior.
[0104] When transformer T4 enters the demagnetizing stage, the drive circuit 303 outputs a high level, controlling the power switch Q0 to conduct, causing the secondary winding of transformer T4 to begin rectification. At this time, the second output terminal ON2 of the power supply control circuit 304 outputs a high level, controlling the fourth switch Q4 to conduct, forming a current generated by the secondary winding of transformer T4. Same terminal -> Source node CP of fourth switch Q4 -> Energy storage capacitor C4 -> Secondary winding of transformer T4 The current path at the opposite end stores the demagnetization phase in the secondary winding of transformer T4. Part of the energy is transferred to the energy storage capacitor C4 for temporary storage. This process not only transfers the charge but also makes the voltage across the energy storage capacitor C4 equal to the output voltage of the transformer T4. It has a proportional relationship, thus enabling control over the output voltage. Sampling.
[0105] When transformer T4 enters the excitation stage, drive circuit 303 outputs a low level, controlling power switch Q0 to turn off, and synchronous rectifier controller 300 does not perform rectification. At this time, the second output terminal ON2 of power supply control circuit 304 outputs a low level, controlling the fourth switch Q4 to turn off, and energy storage capacitor C4 uses the energy stored in the demagnetization stage to power synchronous rectifier controller 300.
[0106] The synchronous rectifier controller and switching power supply provided in this invention achieve efficient power supply by switching between switching transistors and transferring charge, thereby improving the system's energy conversion efficiency.
[0107] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article indicates that the preceding and following related objects have an "or" relationship.
[0108] In the embodiments of this invention, "multiple" refers to two or more.
[0109] The descriptions of "first," "second," etc., appearing in the embodiments of this invention are for illustrative purposes and to distinguish the objects being described. They do not indicate any particular order and do not imply any special limitation on the number of devices in the embodiments of this invention. They do not constitute any limitation on the embodiments of this invention.
[0110] In the several embodiments provided by this invention, it should be understood that the disclosed methods and apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for example, the division of units is merely a logical functional division, and other division methods may exist in actual implementation; for example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, indirect coupling or communication connection between devices or units, and may be electrical, mechanical, or other forms.
[0111] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can be physically arranged separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional units.
[0112] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A synchronous rectifier controller, characterized in that, The synchronous rectification controller includes: a power switch (Q0), a drive circuit (303), a power supply control circuit (304), and a switching circuit; the switching circuit includes: a first switch (Q1), a second switch (Q2), a third switch (Q3), and a fourth switch (Q4); The gate of the first switch (Q1) is connected to the third output terminal of the power supply control circuit (304), and the source of the first switch (Q1) is connected to the source of the second switch (Q2); the drain of the first switch (Q1) is connected to external ground (VSS). The gate of the third switch (Q3) is connected to the first output terminal of the power supply control circuit (304); the source of the third switch (Q3) is connected to the internal ground (GND), and the drain of the third switch (Q3) is connected to the source of the fourth switch (Q4); an energy storage capacitor (C4) is connected between the source of the first switch (Q1) and the drain of the third switch (Q3). The gates of the second switch (Q2) and the fourth switch (Q4) are respectively connected to the second output terminal of the power supply control circuit (304); the drain of the second switch (Q2) is connected to the internal ground (GND); and the drain of the fourth switch (Q4) is connected to the internal power supply (VDD). The drive circuit (303) is used to control the power switch (Q0) to turn on or off, so that the synchronous rectifier controller can perform synchronous rectification or stop synchronous rectification. The power supply control circuit (304) is used to control the conduction or disconnection of each power supply switch in the switching circuit.
2. The synchronous rectifier controller according to claim 1, characterized in that, The power switch (Q0), the first switch (Q1), the second switch (Q2), the third switch (Q3), and the fourth switch (Q4) are all NMOS transistors.
3. The synchronous rectification controller according to claim 2, characterized in that, The power switch (Q0) and the first switch (Q1) are integrated on a single silicon chip and are also integrated with a synchronous rectification control circuit that does not contain high-voltage devices on a single chip.
4. The synchronous rectification controller according to claim 2, characterized in that, The source of the power switch (Q0) is connected to internal ground (GND), the drain of the power switch (Q0) is connected to an external power supply (VD), and the gate of the power switch (Q0) is connected to the driving circuit (303).
5. A switching power supply, characterized in that, The switching power supply includes a transformer, a charge transfer circuit, and a synchronous rectification controller as described in any one of claims 1 to 4; During the demagnetization phase of the transformer, the drive circuit (303) controls the power switch (Q0) to turn on, enabling the synchronous rectifier controller to perform synchronous rectification, and the energy stored on the transformer is transferred to the charge transfer circuit. During the excitation phase of the transformer, the drive circuit (303) controls the power switch (Q0) to disconnect, causing the synchronous rectifier controller to stop synchronous rectification, and the charge transfer circuit supplies power to the synchronous rectifier controller.
6. The switching power supply according to claim 5, characterized in that, The power switch (Q0) is connected to the high-voltage side of the secondary side of the transformer; The charge transfer circuit includes: a power supply capacitor (C3) and an energy storage capacitor (C4); The power supply capacitor (C3) is connected between the internal ground (GND) and the internal power supply (VDD); During the demagnetization phase of the transformer, the energy stored on the transformer is transferred to the energy storage capacitor (C4); During the excitation phase of the transformer, the energy in the energy storage capacitor (C4) is transferred to the power supply capacitor (C3) for storage, and the power supply capacitor (C3) supplies power to the synchronous rectifier controller.
7. The switching power supply according to claim 6, characterized in that, During the demagnetization phase of the transformer, the first output terminal of the power supply control circuit (304) outputs a high level, the second output terminal of the power supply control circuit (304) outputs a low level, the third switch (Q3) is turned on, and the second switch (Q2) and the fourth switch (Q4) are turned off. During the excitation phase of the transformer, the first output terminal of the power supply control circuit (304) outputs a low level, the second output terminal of the power supply control circuit (304) outputs a high level, the third switch (Q3) is turned off, and the second switch (Q2) and the fourth switch (Q4) are turned on.
8. The switching power supply according to claim 5, characterized in that, The power switch (Q0) is connected to the low-voltage side of the transformer secondary winding; the charge transfer circuit includes an energy storage capacitor (C4). The energy storage capacitor (C4) is connected between the internal power supply (VDD) and the internal ground (GND); During the demagnetization phase of the transformer, the second output terminal of the power supply control circuit (304) outputs a high level, and the fourth switching transistor (Q4) is turned on; the energy stored on the transformer is transferred to the energy storage capacitor (C4); During the excitation phase of the transformer, the second output terminal of the power supply control circuit (304) outputs a low level, the fourth switch (Q4) is turned off, and the energy storage capacitor (C4) supplies power to the synchronous rectifier controller.
9. The switching power supply according to any one of claims 6 to 8, characterized in that, The voltage across the energy storage capacitor (C4) is the same as the output voltage of the transformer. They have a proportional relationship.