A high-power synchronous rectification module and switching power supply

Abstract

This utility model discloses a high-power synchronous rectification module and a switching power supply, relating to the field of switching power supply technology. Specifically, it includes at least two parallel rectifier units, with the first end of each rectifier unit connected to one end of the secondary winding and the second end connected to the other end of the secondary winding. Each rectifier unit includes a synchronous rectifier controller and a power transistor. The synchronous rectifier controller is connected to the power transistor and is used to drive the power transistor to turn on and off. The synchronous rectifier controller and the power transistor are integrated within the same package frame. The at least two rectifier units rectify the secondary winding of the transformer and combine the rectified current for output. This module not only reduces the input capacitance of multiple MOSFETs, reduces parasitic parameters in the power and drive circuits, and lowers switching losses and electromagnetic interference, but also suppresses waveform oscillations, improves current sharing, and achieves high current or high power output.

Description

Technical Field

[0001] This utility model relates to the field of switching power supply technology, and in particular to a high-power synchronous rectification module and a switching power supply. Background Technology

[0002] Synchronous rectifier controllers (SR ICs) are a technology that can significantly improve power efficiency by replacing traditional rectifier diodes with MOSFETs that have extremely low on-resistance, thereby greatly reducing losses in the rectifier section.

[0003] Currently, flyback power supplies often use synchronous rectifiers to replace the original Schottky diodes at the output, utilizing a single synchronous rectifier to drive multiple MOSFETs in the switching power supply, such as... Figure 1 As shown, this method can save space, as well as cost and standby power consumption.

[0004] However, the above solution still has shortcomings in use. In high-current loads, since a single synchronous rectifier is used to drive multiple MOSFETs, the length of the trace needs to be increased. The long trace itself and its return path will introduce a high parasitic inductance. This parasitic inductance, together with the input capacitance of each MOSFET and the larger total input capacitance after parallel connection, constitutes a series LC resonant circuit. During high-frequency switching, it is prone to serious gate drive oscillation, resulting in increased switching losses, drive waveform oscillation, and current imbalance.

[0005] Therefore, this application aims to solve the problems that a single synchronous rectifier driving multiple MOSFETs can easily increase the input capacitance, resulting in increased switching losses, waveform oscillations, and current imbalances. Utility Model Content

[0006] The main purpose of this invention is to provide a high-power synchronous rectification module and switching power supply, which aims to reduce the input capacitance of multiple MOSFETs, reduce switching losses, suppress waveform oscillations, and improve current sharing.

[0007] To achieve the above objectives, this utility model proposes a high-power synchronous rectifier module for connecting the secondary winding of a transformer, comprising: At least two rectifier units connected in parallel, wherein the first end of the rectifier unit is connected to one end of the secondary winding and the second end of the rectifier unit is connected to the other end of the secondary winding; the at least two rectifier units rectify the secondary winding and combine the rectified currents for output. Each of the rectifier units includes a synchronous rectifier controller and a power transistor, the synchronous rectifier controller being connected to the power transistor, and the synchronous rectifier controller and the power transistor being integrated within the same package frame.

[0008] Furthermore, the drain of the power transistor is connected to one end of the secondary winding, the source of the power transistor is connected to the other end of the secondary winding, the synchronous rectification controller includes a driving unit, and the gate of the power transistor is connected to the driving unit.

[0009] Furthermore, the synchronous rectification controller includes a power supply unit, which is connected to the drain of the power transistor through its own charging path.

[0010] Furthermore, the synchronous rectification controller includes a detection unit, the input terminal of which is connected to the drain of the power transistor. The detection unit receives the voltage of the power transistor and outputs a control signal according to the voltage of the power transistor. The gate of the power transistor receives the control signal.

[0011] Furthermore, the detection unit includes a voltage comparator, a logic controller, and a driver, wherein the voltage comparator is connected to the logic controller, and the logic controller is connected to the driver; The input terminal of the voltage comparator is connected to the drain voltage of the power transistor and compared with a preset conduction threshold to generate a level signal that is transmitted to the logic controller. The logic controller receives the level signal, converts the level signal into a digital signal, and transmits it to the driver; The driver receives the digital signal and generates the control signal, which is transmitted to the gate of the power transistor.

[0012] Furthermore, the detection unit includes a delay unit, which is connected to the logic controller.

[0013] Furthermore, the synchronous rectification controller and the power transistor are integrated within the same package frame, which includes SOP, QFN / DFN, or TO.

[0014] Furthermore, at least two of the rectifier units are spaced apart on the printed circuit board.

[0015] This application also discloses a switching power supply, including a primary-side switching circuit, a transformer, and the aforementioned high-power synchronous rectification module. The primary-side switching circuit is connected to the primary winding of the transformer, and the high-power synchronous rectification module is connected to the secondary winding of the transformer.

[0016] The above technical solution has the following advantages: This application connects multiple rectifier units in parallel, with each rectifier unit integrating an independent synchronous rectifier controller and power transistors to form a distributed autonomous control unit. The synchronous rectifier controller turns on or off the corresponding power transistors, which not only reduces the input capacitance of multiple MOSFETs, but also reduces parasitic parameters in the power circuit and drive circuit, reduces switching losses and electromagnetic interference, suppresses waveform oscillations, improves current sharing, and achieves high current or high power output.

[0017] The parallel connection of multiple rectifier units achieves heat dispersion, avoiding localized overheating, and improves system reliability through redundancy design. The synchronous rectifier controller adopts self-powered operation without auxiliary windings, directly charging through the secondary winding of the transformer. It utilizes a delay unit to optimize the initial ringing interference of the power transistors, thereby improving system efficiency and reliability. Attached Figure Description

[0018] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a schematic diagram of a traditional high-current structure; Figure 2 This is a schematic diagram of the structure of this utility model; Figure 3 This is a schematic diagram of the rectifier unit of this utility model; Figure 4 This is a schematic diagram of the detection unit of this utility model.

[0019] In the diagram: 1. Transformer; 2. Rectifier unit; 21. Power transistor; 22. Synchronous rectifier controller; 221. Power supply unit; 222. Detection unit; 2221. Voltage comparator; 2222. Logic controller; 2223. Driver; 2224. Delay unit; 223. Drive unit; 3. Load. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain this utility model and do not constitute a limitation on this utility model.

[0021] like Figure 1 As shown, in switching power supplies, especially in high-power, high-current output applications, multiple MOSFETs are typically connected in parallel to share the current and reduce conduction losses. In existing technologies, a single synchronous rectifier controller (SR IC) is commonly used to drive these parallel MOSFETs. This "one-to-many" drive architecture suffers from the following insurmountable technical drawbacks: a. A single SR IC needs to drive the total input capacitance of multiple MOSFETs, resulting in insufficient drive capability. More seriously, it is difficult to make the PCB trace path length and impedance from the SR IC to the gate of each MOSFET completely consistent. These differences in parasitic parameters will generate severe gate drive oscillations during high-frequency switching, which not only increases switching losses but also causes the electromagnetic interference problem to worsen dramatically.

[0022] b. Due to slight differences in the parameters of the parallel MOSFETs, such as turn-on voltage Vth and transconductance gm, and switching timing deviations caused by asynchronous drive paths, the transient switching current of each MOSFET will be severely uneven. This will cause some MOSFETs to experience current stress far exceeding the average value, generating local hot spots. Although the positive temperature coefficient of DC on-resistance has a certain DC current sharing effect, in high-frequency applications where switching losses dominate, local overheating caused by dynamic current imbalance will accelerate aging and may even trigger a chain reaction leading to thermal runaway and burnout of the entire unit.

[0023] c. Deviations in drive timing prevent parallel MOSFETs from switching synchronously and quickly, leading to an increase in the total switching time and a significant increase in common switching losses, which limits the improvement of system efficiency and switching frequency.

[0024] Designers need to spend a lot of effort on complex symmetry design in PCB layout to balance the drive path, but this is not very effective in high-density layouts. At the same time, the failure of any MOSFET can impact the driver IC and other parallel MOSFETs, reducing system reliability.

[0025] Therefore, this application aims to provide a novel synchronous rectification module that fundamentally solves the technical problems of drive oscillation, dynamic current sharing difference, large switching losses, and low reliability in existing high-current parallel solutions. The specific solution is as follows: like Figure 2 and Figure 3 As shown, a high-power synchronous rectification module includes at least two parallel rectifier units 2. The first end of the rectifier unit 2 is connected to one end of the secondary winding, and the second end of the rectifier unit 2 is connected to the other end of the secondary winding. The rectifier unit 2 includes a synchronous rectifier controller 22 and a power transistor 21. The synchronous rectifier controller 22 is connected to the power transistor 21 and is used to drive the power transistor 21 to turn on and off. The synchronous rectifier controller 22 and the power transistor 21 are integrated in the same package frame. The at least two rectifier units 2 rectify the secondary winding of the transformer 1 and combine the rectified current for output.

[0026] Specifically, multiple rectifier units 2 are connected in parallel on the secondary winding of transformer 1. The first and second ends of rectifier unit 2 refer to the current inflow end and the current outflow end, respectively, and can also be arranged in reverse. The specific configuration can be selected according to the needs. For example, this application selects three rectifier units 2, which are connected in parallel synchronously. The current of the secondary winding of transformer 1 is distributed to multiple rectifier units 2, realizing a balanced current distribution of the load 3 and supporting high-current and high-power loads 3. For the multiple rectifier units 2 on the load 3, each rectifier unit 2 is integrated with an independent synchronous rectifier unit 2 and a power transistor 21. This not only reduces wiring and simplifies electrical circuits, but also reduces parasitic inductance introduced by power transistors 21 and circuits, and reduces parasitic parameters in power and drive circuits. This effectively suppresses voltage spikes and oscillations in VDS, reduces switching losses and electromagnetic interference (EMI), and also suppresses waveform oscillations, resulting in faster and cleaner switching action. After multiple rectifier units 2 rectify the secondary windings of transformer 1, the current is combined and input to the high-power load 3. This not only meets the requirements for high-power or high-current output, but also ensures current balance among multiple rectifier units 2 to prevent thermal runaway and burnout.

[0027] Under the premise of achieving high current and high power load 3, this application independently controls the rectifier unit 2, realizing natural and dynamic current sharing without external intervention. This fundamentally eliminates the current sharing problem caused by inconsistent parameters and asymmetrical layout, and also avoids the complex current sharing and heat dissipation design around the power transistor 21, greatly reducing the design cost. At the same time, it also eliminates single point of failure. If a single rectifier unit 2 fails, it will not affect the normal operation of the system. The remaining rectifier units 2 will still maintain the normal operation of the system, improving the fault tolerance of the system.

[0028] like Figure 3 As shown, the drain and source of the power transistor 21 are connected to the two ends of the secondary winding of the transformer 1, respectively. The synchronous rectifier controller 22 includes a drive unit 223, which is connected to the gate of the power transistor 21.

[0029] Specifically, the power transistor 21 in this application is selected as a synchronous rectifier MOSFET, i.e., SR MOS. The driving unit 223 of the synchronous rectifier controller 22 is connected to the gate of the power transistor 21. The driving unit 223 of the synchronous rectifier controller 22 controls the turn-on and turn-off of the power transistor 21. When the gate of the power transistor 21 is turned on, the source and drain of the power transistor 21 can be turned on.

[0030] The following is a detailed description of the synchronous rectifier controller 22: like Figure 3As shown, the synchronous rectifier controller 22 includes a power supply unit 221, which is connected to the drain of the power transistor 21 through its own charging path. The secondary winding of the transformer 1 supplies power to the power supply unit 221. The power supply unit 221 can be powered by an external power source. Preferably, the secondary winding of the transformer 1 charges the power supply unit 221 to ensure the normal operation of the synchronous rectifier controller 22. The charging path of the power supply unit 221 includes a bandgap reference source, a pulsed low-dropout linear regulator, and a switch. The bandgap reference source provides a stable voltage or current reference. When the switch is closed, the pulsed low-dropout linear regulator outputs a stable driving voltage. The driving voltage of the power supply unit 221 acts on the driving unit 223, thereby controlling the on and off states of the power transistor 21 through the driving unit 223.

[0031] like Figure 3 As shown, the synchronous rectification controller 22 includes a detection unit 222. The input terminal of the detection unit 222 is connected to the drain of the power transistor 21 to receive the drain voltage of the power transistor 21. Based on the voltage of the power transistor 21, a control signal is output, and the gate of the power transistor 21 receives the control signal. Specifically, the detection unit 222 receives the drain voltage of its power transistor 21 and compares this voltage with a preset conduction threshold to determine the difference between the drain voltage signal of the power transistor 21 and the conduction threshold. Based on the difference, different control signals are output. The control signal is connected to the gate of the power transistor 21 to turn the power transistor 21 on or off. By using the extremely low on-resistance of the power transistor 21 to replace traditional diode rectification, the losses during secondary winding current flow are significantly reduced, ensuring efficient energy transfer to the load 3 and preventing reverse current flow into the secondary winding of transformer 1. At the same time, the detection unit 222 monitors the drain voltage of the power transistor 21 in real time. When the drain voltage is abnormal or voltage oscillation occurs, the detection unit 222 can also turn off the power transistor 21 in time through the drive unit 223 to prevent the device from overheating or being damaged.

[0032] like Figure 3 and Figure 4As shown, the detection unit 222 includes a voltage comparator 2221, a logic controller 2222, and a driver 2223. The voltage comparator 2221 is connected to the logic controller 2222, and the logic controller 2222 is connected to the driver 2223. The input terminal of the voltage comparator 2221 is connected to the drain voltage of the power transistor 21. After comparing with a preset turn-on threshold, a level signal is generated. The level signal is output to the logic controller 2222. The logic controller 2222 receives the level signal and converts it into a digital signal. Then, the digital signal is sent to the driver 2223. The driver 2223 receives the digital signal and generates the control signal mentioned above through the digital signal. The control signal is used to drive the gate of the power transistor 21 to realize the turn-on and turn-off of the power transistor 21. The power supply unit 221 supplies power to the detection unit 222 and the drive unit 223. In the detection unit 222, the voltage comparator 2221 compares the voltage of the drain with the voltage of the turn-on threshold to obtain the potential of the drain. Based on this potential, high-level and low-level signals are generated. The logic controller 2222 receives the high-level and low-level signals and can combine them with timing signals to generate timing-based digital signals. The driver 2223 receives the digital signals and converts them into high-voltage or high-current control signals to realize the turn-on or turn-off of the power transistor 21.

[0033] Among them, the voltage comparator 2221 can be an LM393 or TLV3501, which outputs high and low level signals; the logic controller 2222 can be an AND gate, an OR gate, or an SR flip-flop to make judgments and generate digital signals; the driver 2223 can be an IR2110 or a Soft Driver, which converts low voltage / small current digital signals into high voltage / large current drive signals to match the requirements of the power transistor 21.

[0034] Based on the above scheme, the detection unit 222 also includes a delay unit 2224. The delay unit 2224 is connected to the logic controller 2222. The delay unit 2224 is used to delay the turn-off time of the drive unit 223. The delay unit 2224 preferably adopts a monostable trigger. When the power transistor 21 is turned on, it forces it to maintain the on state of the logic controller 2222. The duration of this state can be set as needed, preferably the minimum time, which can avoid maloperation caused by the initial ringing of the power transistor 21.

[0035] like Figure 3As shown, in this application, the synchronous rectification controller 22 and the power transistor 21 are integrated within the same package frame, which may include SOP, QFN / DFN, or TO. Various package frames can be used, such as SOP-8 / EP, QFN / DFN, or TO-252 / 263 5-pin, encapsulating the synchronous rectification controller 22 and the power transistor 21 within a single package frame to form a distributed autonomous control unit. Each synchronous rectification controller 22 independently determines and drives the power transistor 21 based solely on its corresponding drain-source voltage, achieving natural current sharing. The parallel connection of multiple rectification units 2 disperses heat distribution, avoiding localized overheating, and improves system reliability through redundancy design. Simultaneously, this structure effectively reduces the influence of parasitic parameters in the gate drive circuit and power circuit, decreasing switching losses and voltage stress peaks.

[0036] At least two rectifier units 2 are spaced apart on the printed circuit board. To further improve the heat distribution, multiple rectifier units 2 are spaced apart on the printed circuit board and evenly arranged on the secondary winding of the transformer 1, keeping the line length consistent and minimizing the timing differences between the rectifier units 2.

[0037] like Figures 1-3 As shown, a switching power supply includes a primary-side switching circuit, a transformer 1, and the aforementioned high-power synchronous rectifier module. The primary-side switching circuit is connected to the primary winding of the transformer 1, and the high-power synchronous rectifier module is connected to the secondary winding of the transformer 1. The switching power supply can be a flyback converter and is configured to operate stably in continuous conduction mode, intermittent conduction mode, and quasi-resonant mode.

[0038] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the inventive concept of the present utility model using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A high power synchronous rectification module for connecting to a secondary winding of a transformer, characterized in that, include: At least two rectifier units connected in parallel, wherein the first end of the rectifier unit is connected to one end of the secondary winding, and the second end of the rectifier unit is connected to the other end of the secondary winding; At least two of the rectifier units rectify the secondary windings and combine the rectified currents for output; Each of the rectifier units includes a synchronous rectifier controller and a power transistor, the synchronous rectifier controller being connected to the power transistor, and the synchronous rectifier controller and the power transistor being integrated within the same package frame.

2. The high power synchronous rectification module of claim 1, wherein, The drain of the power transistor is connected to one end of the secondary winding, and the source of the power transistor is connected to the other end of the secondary winding. The synchronous rectification controller includes a driving unit, and the gate of the power transistor is connected to the driving unit.

3. The high power synchronous rectification module of claim 1, wherein, The synchronous rectification controller includes a power supply unit, which is connected to the drain of the power transistor through its own charging path.

4. The high power synchronous rectification module of claim 3, wherein, The synchronous rectification controller includes a detection unit. The input terminal of the detection unit is connected to the drain of the power transistor. The detection unit receives the voltage of the power transistor and outputs a control signal according to the voltage of the power transistor. The gate of the power transistor receives the control signal.

5. A high power synchronous rectification module as claimed in claim 4, wherein, The detection unit includes a voltage comparator, a logic controller, and a driver. The voltage comparator is connected to the logic controller, and the logic controller is connected to the driver. The input terminal of the voltage comparator is connected to the drain voltage of the power transistor and compared with a preset conduction threshold to generate a level signal that is transmitted to the logic controller. The logic controller receives the level signal, converts the level signal into a digital signal, and transmits it to the driver; The driver receives the digital signal and generates the control signal, which is transmitted to the gate of the power transistor.

6. A high power synchronous rectification module as claimed in claim 5, wherein, The detection unit includes a delay unit, which is connected to the logic controller.

7. A high power synchronous rectification module as claimed in any one of claims 1 to 6, characterized in that, The synchronous rectification controller and the power transistor are integrated in the same package frame, which includes SOP, QFN / DFN or TO.

8. The high power synchronous rectification module of claim 1, wherein, At least two of the rectifier units are spaced apart on the printed circuit board.

9. A switching power supply, characterized by It includes a primary-side switching circuit, a transformer, and a high-power synchronous rectification module as described in any one of claims 1 to 8, wherein the primary-side switching circuit is connected to the primary winding of the transformer, and the high-power synchronous rectification module is connected to the secondary winding of the transformer.

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