A non-isolated clamp circuit, a method for feeding back high-voltage spike energy and a switching power supply for an input-output common ground power converter

Abstract

The application discloses a non-isolated clamping circuit, a feedback high-voltage spike energy method and a switching power supply for an input-output common ground power converter. The power converter comprises a primary side switching circuit, a transformer, a secondary side rectifier circuit and an input capacitor. The clamping circuit comprises at least one feedback diode. The anode of the feedback diode is connected to a stress spike node of a rectifier tube in the secondary side rectifier circuit, and the cathode of the feedback diode is connected to a stable voltage node on the input side. The potential of the stable voltage node is higher than the theoretical platform voltage of the cathode node of the rectifier tube in the normal working state. The application discards the traditional idea of connecting the rectifier tube in parallel to absorb spike energy, and instead constructs a new energy feedback path to guide the high-voltage spike energy generated when the rectifier tube is turned off to a stable voltage node, thereby realizing efficient, low-stress and high-reliability clamping.

Description

Technical Field

[0001] This application relates to the field of switching power supply technology, specifically to a non-isolated clamping circuit for an input-output common-ground power converter, a method for feeding back high-voltage spike energy, and a switching power supply, which is particularly suitable for non-isolated high-power power modules based on isolation topologies such as full-bridge and implemented through an input-output common-ground method. Background Technology

[0002] In modern power supply design, which pursues high power density and high efficiency, converting mature isolated topologies (such as LLC resonant full-bridge) into non-isolated power supplies through a common input-output grounding approach has become a preferred solution in fields such as servers, communications, and high-end industrial equipment. This design retains the excellent soft-switching characteristics and magnetic component design of the original topology, while eliminating optocouplers, isolation drivers, and other components, achieving a good balance between performance, cost, and size.

[0003] However, while this "common-ground non-isolated" architecture simplifies the system, it also introduces a unique and severe engineering challenge: the extreme deterioration of the operating potential environment of the secondary power loop. Take, for example, a circuit using full-wave rectification on the secondary side: In standard isolated applications, the secondary circuit uses its own independent "floating ground" as a reference potential, and its voltage waveform oscillates symmetrically near zero potential. The steady-state reverse voltage that the rectifier diodes withstand when turned off is determined by the transformer turns ratio, and the potentials of each node in the circuit relative to ground (or the primary side) are isolated and uncertain.

[0004] In a non-isolated architecture with common input and output ground, the negative terminal of the secondary output is forcibly connected to the negative terminal of the primary input, forming a common system reference ground. This critical connection leads to: The potential reference is forcibly bound: the "absolute potential" (i.e. the potential relative to the system common ground) of the entire secondary circuit, including the rectifier diodes, synchronous rectifier driver ICs and their auxiliary circuits, no longer floats, but is strongly modulated by the operation of the primary-side switching transistors.

[0005] Harsh common-mode operating environment: The drastic voltage jumps (dv / dt) between zero volts and hundreds of volts at the primary-side switching node, coupled through transformers, force the corresponding potential at the secondary winding terminals to oscillate rapidly between large positive and negative values. Although the relative voltage difference across the rectifier diodes (i.e., the reverse voltage plateau they withstand) is the same under ideal conditions as in isolated applications, the absolute potentials of their cathodes and anodes may be at vastly different high-voltage positive and negative potentials, respectively. This effectively "immerses" the entire secondary circuit in a harsh electromagnetic environment with high dv / dt and a wide common-mode voltage range.

[0006] The most direct consequence of this harsh environment is the suppression of turn-off voltage spikes. In practical circuits, transformer leakage inductance and parasitic parameters inevitably cause turn-off voltage oscillations (spikes). In isolated applications, this spike is superimposed on a lower floating potential. However, in common-ground non-isolated applications, the same spike is superimposed on a stable voltage that has been significantly raised or lowered by the primary-side switching action, causing its peak absolute voltage to far exceed the device's safety margin, posing a fatal threat to the rectifier diode.

[0007] To address this threat, existing technologies typically directly port parallel active clamping schemes suitable for isolated architectures. This scheme connects a branch consisting of capacitors, switching transistors, and complex control circuitry in parallel across the rectifier diodes to actively absorb peak energy. However, this approach has inherent limitations when dealing with non-isolated environments: The clamping device itself experiences a significant increase in stress and losses: the parallel clamping branch must withstand the same harsh absolute potential and high dv / dt as the main rectifier. Its switching transistor must be a high-voltage device, resulting in high on-resistance and high switching losses. When handling high-energy spikes, this transistor becomes a localized hotspot, significantly reducing reliability.

[0008] The complexity of the control circuit increases dramatically: To achieve nanosecond-level precise driving of the clamping switch under wide common-mode noise, complex level shifting, isolation driving or synchronization circuits are required, which greatly increases the system complexity and failure probability.

[0009] This approach attempts to solve the spike problem caused by harsh environments by adding a complex active circuit that also operates in harsh environments. This is a fundamental contradiction and is not the optimal solution in terms of efficiency, reliability, and cost.

[0010] Therefore, existing technologies lack a solution that can innovate at the energy path topology level, enabling the clamping circuit itself to avoid harsh common-mode operating environments, thereby solving the problem of voltage spikes in the secondary rectifier diodes of non-isolated power supplies in a simpler, more efficient, and reliable manner. Summary of the Invention

[0011] To overcome the shortcomings of existing technologies using traditional parallel active clamping circuits in non-isolated power supply architectures with common input and output ground, which result in clamping devices operating in harsh potential environments, high stress, high losses, complex control, and low reliability, this application provides a non-isolated clamping circuit, a method for feeding back high-voltage spike energy, and a switching power supply for input-output common-ground power converters. It abandons the traditional approach of connecting the clamping circuit in parallel with the rectifier diode to absorb spike energy, instead constructing a new energy feedback path to guide the high-voltage spike energy generated when the rectifier diode is turned off to a stable potential node, thereby achieving efficient, low-stress, and highly reliable clamping.

[0012] In one embodiment, this application provides a non-isolated clamping circuit for an input-output common-ground power converter. The power converter includes a primary-side switching circuit, a transformer, a secondary-side rectifier circuit, and an input capacitor. The clamping circuit includes at least one feedback diode. The anode of the feedback diode is connected to the stress spike node of the rectifier diode in the secondary-side rectifier circuit, and the cathode of the feedback diode is connected to a stable voltage node on the input side. The potential of the stable voltage node is higher than the theoretical plateau voltage of the rectifier diode's cathode node under normal operating conditions. The stress spike node is the location where a high-voltage spike occurs when the rectifier diode is turned off.

[0013] In one alternative, the stabilizing voltage node is the positive terminal of the input capacitor.

[0014] In an alternative embodiment, the stable voltage node further includes: A voltage divider circuit connected in parallel with the input capacitor; the voltage divider circuit includes a first resistor, a second resistor, a first capacitor, and a second capacitor, the first resistor and the first capacitor are connected in parallel, the second resistor and the second capacitor are connected in parallel, one end of the first resistor and the first capacitor is connected to the positive terminal of the input capacitor, the other end of the second resistor and the second capacitor is grounded, and the other end of the first resistor and one end of the second resistor are the stable voltage node.

[0015] In one alternative, the feedback diode is a diode or a MOSFET.

[0016] In one alternative, the secondary-side rectifier circuit is a bridge rectifier circuit, a half-wave rectifier circuit, a full-wave rectifier circuit, or a current multiplier circuit.

[0017] In one embodiment, this application provides a non-isolated clamping circuit for an input-output common-ground power converter. The power converter includes a primary-side switching circuit, a transformer, a secondary-side rectifier circuit, and an input capacitor. The secondary-side rectifier circuit includes multiple rectifier diodes. The clamping circuit includes multiple feedback diodes. The stress spike node of each rectifier diode is connected to a stable voltage node on the input side through an independent feedback diode. The potential of the stable voltage node is higher than the theoretical plateau voltage of the cathode node of the rectifier diode under normal operating conditions.

[0018] In one alternative embodiment, the secondary-side rectifier circuit is a full-wave rectifier circuit, and the clamping circuit includes a first feedback diode and a second feedback diode; the anode of the first feedback diode is connected to the cathode of a half-wave rectifier diode of the full-wave rectifier circuit, the anode of the second feedback diode is connected to the cathode of another half-wave rectifier diode of the full-wave rectifier circuit, and the other ends of the first feedback diode and the second feedback diode are connected to a stable voltage node on the input side.

[0019] In one embodiment, this application provides a method for feeding back high-voltage spike energy. The method is applied to the aforementioned non-isolated clamping circuit. When the rectifier diode of the secondary rectifier circuit is turned off, and the stress spike node of the secondary rectifier circuit generates a voltage higher than the theoretical plateau voltage, the potential of the stress spike node rises instantaneously. When the potential of the stress spike node exceeds the voltage of the stable voltage node, the feedback diode is forward-biased, and the spike energy is fed back to the stable voltage node through the feedback diode.

[0020] In one embodiment, this application provides a switching power supply equipped with the aforementioned non-isolated clamping circuit and the aforementioned method for feeding back high-voltage spike energy.

[0021] Compared with the prior art, this application has the following beneficial effects: Effective clamping voltage: The feedback diode clamps the highest potential of the stress peak node of the rectifier tube below the stable voltage node voltage and the voltage drop of the feedback diode, thereby reliably protecting the rectifier tube.

[0022] Avoiding harsh environments: The cathode of the core component of the clamping action (feedback diode) is connected to the midpoint of the input capacitor, which has a relatively stable potential and is not severely affected by the primary-side switching, so that it does not need to operate in the harsh wide-range common-mode voltage environment of the secondary side.

[0023] Simplified circuitry and reduced stress: The entire clamping circuit does not require a separate switching transistor and its complex isolation drive circuit, nor does it require a high-voltage, high-current clamping capacitor.

[0024] Energy reuse: The peak energy fed back to the midpoint of the input capacitor can be partially reused by the system, which helps to improve the overall conversion efficiency.

[0025] Compared with the prior art, the beneficial effects of this application are as follows: High reliability: By simplifying the clamping circuit structure, the reliability risks caused by complex timing control and single-point failure of high-voltage MOSFETs are eliminated, making it particularly suitable for fields with stringent reliability requirements such as automotive electronics and industrial control.

[0026] High efficiency and low heat loss: The clamping path has low conduction loss and avoids the high switching and conduction losses of high voltage MOSFETs, which significantly reduces the system temperature rise and is conducive to improving power density.

[0027] Low cost and easy implementation: It eliminates the need for expensive control chips, high-voltage MOSFETs and isolation drive circuits, and only adds a few passive components, which greatly reduces the cost and board layout difficulty.

[0028] By innovating at the topological level of energy paths, this approach fundamentally solves the compatibility problem of traditional solutions in non-isolated, shared-ground applications, providing a simpler, more stable, and more efficient solution that is more fundamental. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the circuit principle in some embodiments of this application; Figure 2 This is a schematic diagram of the circuit principle after setting the voltage divider circuit in some embodiments of this application; Figure 3 This is a schematic diagram showing that the secondary circuit of this application is a full-bridge rectifier circuit in some embodiments; Figure 4 This is a circuit schematic diagram of a second embodiment of a non-isolation clamping circuit according to this application. Detailed Implementation

[0030] The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application. Similarly, the following examples are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0032] In this application, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly, meaning electrical connection or intercommunication, or connection through other equivalent means; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal connection of two elements or the interaction between two elements, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0033] In some implementations, please refer to Figure 1This application provides a non-isolated clamping circuit for a common-ground input / output power converter, applicable to power converters with common-ground input / output. The power converter includes a primary-side switching circuit, a transformer, a secondary-side rectifier circuit, and an input capacitor Cin; the clamping circuit includes at least one feedback diode Q1; the anode of the feedback diode Q1 is connected to the stress spike node of the rectifier diode in the secondary-side rectifier circuit, and the cathode of the feedback diode Q1 is connected to the stable voltage node on the input side; wherein, the stress spike node can be any location where a high-voltage spike is generated when the rectifier diode is turned off, and the potential of the stable voltage node is higher than the theoretical plateau voltage of the rectifier diode cathode node under normal operating conditions.

[0034] When the secondary rectifier diode is turned off, a voltage spike higher than the theoretical stress plateau is generated at its stress peak node due to factors such as transformer leakage inductance. The potential at this node will rise instantaneously. Once this spike potential exceeds the stable voltage node voltage, the feedback diode Q1 will immediately turn on in the forward direction. At this time, the spike energy is no longer limited to dissipation or storage in the secondary circuit, but is fed back to the stable voltage node on the input side.

[0035] Thus, an energy feedback guiding path is formed through the clamping circuit composed of feedback diode Q1.

[0036] Effective voltage clamping: The highest potential of the rectifier diode stress peak node can be clamped below the stable voltage node voltage and the voltage drop of the feedback diode Q1, thus reliably protecting the rectifier diode. Beneficial for avoiding harsh environments: The cathode of the feedback diode Q1, which performs the clamping action, is connected to the stable voltage node on the input side, where the potential is relatively stable and unaffected by the severe switching on the primary side. This eliminates the need for it to operate in the harsh, wide-range common-mode voltage environment on the secondary side. Simplified circuitry and reduced stress: The entire clamping circuit eliminates the need for a separate switching transistor and its complex isolation drive circuit, as well as high-voltage, high-current clamping capacitors. Energy reuse: The peak energy fed back to the stable voltage node on the input side can be partially reused by the system, helping to improve overall conversion efficiency.

[0037] In some implementations, please refer to Figure 1 The stable voltage node is the positive terminal of the input capacitor, which is then used as the intermediate potential point. The potential is relatively stable and unaffected by the drastic switching on the primary side. It does not need to operate in the harsh wide-range common-mode voltage environment of the secondary side, simplifying the circuit and reducing stress.

[0038] In some implementations, please refer to Figure 2 and Figure 3 The non-isolated clamping circuit of this application also includes: A voltage divider circuit is connected in parallel with the input capacitor Cin. The voltage divider circuit includes a first resistor R1, a second resistor R2, a first capacitor C1, and a second capacitor C2. The first resistor R1 and the first capacitor C1 are connected in parallel, and the second resistor R2 and the second capacitor C2 are connected in parallel. One end of the first resistor R1 and the first capacitor C1 is connected to the positive terminal of the input capacitor, and the other end of the second resistor R2 and the second capacitor C2 is grounded. The other end of the first resistor R1 and one end of the second resistor R2 form a stable voltage node. The anode of the feedback diode Q1 is connected to the top of the secondary rectifier bridge circuit, and the cathode of the feedback diode Q1 is connected to the stable voltage node.

[0039] See Figure 3 The input capacitor Cin serves as both the input capacitor of the primary-side switching circuit and the clamping capacitor. When the voltage stress of the bridge circuit exceeds the voltage drop across capacitor Cin, excess peak energy is directed to capacitor Cin. The voltage across capacitor Cin can be designed using the voltage drop across the first resistor R1 and the second resistor R2. Furthermore, capacitor Cin is also the input capacitor of the product, and the peak energy can ultimately be used in the main power circuit, achieving both peak suppression and peak energy absorption, as well as feedback to the main power to improve efficiency. The clamping circuit provided in this example embodiment has the advantages of fewer components and lower cost.

[0040] In some implementations, the feedback diode Q1 is a diode or a MOSFET.

[0041] In some embodiments, this application provides a non-isolated clamping circuit for an input-output common-ground power converter. The power converter includes a primary-side switching circuit, a transformer, a secondary-side rectifier circuit, and an input capacitor. The secondary-side rectifier circuit includes multiple rectifier diodes. The clamping circuit includes multiple feedback diodes. The stress spike node of each rectifier diode is connected to a stable voltage node on the input side through an independent feedback diode. The potential of the stable voltage node is higher than the theoretical plateau voltage of the cathode node of the rectifier diode under normal operating conditions.

[0042] In some implementations, please refer to Figure 4 This is a specific implementation example of a non-isolated clamping circuit in this embodiment, applied to a power converter with common input and output ground. The power converter includes a primary-side switching circuit, a transformer, a secondary-side rectifier circuit, and an input capacitor. The secondary-side rectifier circuit is a full-wave rectifier circuit. The clamping circuit includes a first feedback diode Q1 and a second feedback diode Q2; the anode of the first feedback diode Q1 is connected to the cathode of one half-wave rectifier diode in the full-wave rectifier circuit, and the anode of the second feedback diode Q2 is connected to the cathode of the other half-wave rectifier diode in the full-wave rectifier circuit. The other ends of the first feedback diode Q1 and the second feedback diode Q2 are connected to a stable voltage node on the input side, such as the positive terminal of the input capacitor Cin.

[0043] When the stress on the half-wave rectifier diode exceeds the input voltage, the excess peak energy is directed to the input capacitor Cin through the first feedback diode Q1 and the second feedback diode Q2, respectively. This allows the peak energy to be ultimately used in the main power circuit, thus achieving both peak suppression and peak energy absorption, as well as feedback to the main power circuit to improve efficiency. It also boasts the advantages of fewer components and lower cost.

[0044] In some implementations, the secondary-side rectifier circuit can be a bridge rectifier circuit, a half-wave rectifier circuit, a full-wave rectifier circuit, or a current multiplier circuit.

[0045] In some embodiments, this application provides a method for feeding back high-voltage spike energy. This method is applied to the above-mentioned non-isolated clamping circuit. When the rectifier diode of the secondary rectifier circuit is turned off, and the stress spike node of the secondary rectifier circuit generates a voltage higher than the theoretical plateau voltage, the potential of the stress spike node rises instantaneously. When the potential of the stress spike node exceeds the voltage of the stable voltage node, the feedback diode is forward-biased, and the spike energy is fed back to the stable voltage node through the feedback diode.

[0046] In one embodiment, this application provides a switching power supply equipped with the aforementioned non-isolated clamping circuit and the aforementioned method for feeding back high-voltage spike energy.

[0047] The above embodiments are merely preferred embodiments of this application. It should be noted that the above preferred embodiments should not be considered as limitations on this application. Several improvements and modifications can be made without departing from the spirit and scope of this application. These improvements and modifications are obvious from existing well-known technologies and should also be considered within the protection scope of this application. They will not be elaborated further here using examples.

Claims

1. A non-isolated clamping circuit for an input-output common-ground power converter, the power converter comprising a primary-side switching circuit, a transformer, a secondary-side rectifier circuit, and an input capacitor; characterized in that: The clamping circuit includes at least one feedback diode. The anode of the feedback diode is connected to the stress peak node of the rectifier in the secondary rectifier circuit, and the cathode of the feedback diode is connected to the stable voltage node on the input side. The potential of the stable voltage node is higher than the theoretical plateau voltage of the stress peak node of the rectifier under normal operating conditions.

2. The non-isolated clamping circuit according to claim 1, characterized in that, The stable voltage node is the positive terminal of the input capacitor.

3. The non-isolated clamping circuit according to claim 1, characterized in that: The stable voltage node also includes: A voltage divider circuit connected in parallel with the input capacitor; the voltage divider circuit includes a first resistor, a second resistor, a first capacitor, and a second capacitor, the first resistor and the first capacitor are connected in parallel, the second resistor and the second capacitor are connected in parallel, one end of the first resistor and the first capacitor is connected to the positive terminal of the input capacitor, the other end of the second resistor and the second capacitor is grounded, and the other end of the first resistor and one end of the second resistor are the stable voltage node.

4. The non-isolated clamping circuit according to claim 1, characterized in that, The feedback diode is either a diode or a MOSFET.

5. The non-isolated clamping circuit according to claim 1, characterized in that, The secondary rectifier circuit is a bridge rectifier circuit, a half-wave rectifier circuit, a full-wave rectifier circuit, or a current multiplier circuit.

6. A non-isolated clamping circuit for an input-output common-ground power converter, the power converter comprising a primary-side switching circuit, a transformer, a secondary-side rectifier circuit, and an input capacitor, the secondary-side rectifier circuit comprising a plurality of rectifier diodes; characterized in that: The clamping circuit includes at least one feedback diode. The stress spike node of each rectifier is connected to the stable voltage node on the input side through an independent feedback diode. The potential of the stable voltage node is higher than the theoretical plateau voltage of the cathode node of the rectifier under normal operating conditions.

7. The non-isolated clamping circuit according to claim 1, characterized in that: The secondary rectifier circuit is a full-wave rectifier circuit, and the clamping circuit includes a first feedback diode and a second feedback diode. The anode of the first feedback diode is connected to the cathode of a half-wave rectifier diode of the full-wave rectifier circuit, and the anode of the second feedback diode is connected to the cathode of another half-wave rectifier diode of the full-wave rectifier circuit. The other ends of the first feedback diode and the second feedback diode are connected to the stable voltage node on the input side.

8. A method for feeding back high-voltage peak energy, characterized in that, The method is applied to the non-isolated clamping circuit as described in any one of claims 1 to 7. When the rectifier diode of the secondary rectifier circuit is turned off, and the stress spike node of the secondary rectifier circuit generates a voltage higher than the theoretical plateau voltage, the potential of the stress spike node rises instantaneously. When the potential of the stress spike node exceeds the voltage of the stable voltage node, the feedback diode is forward-biased, and the spike energy is fed back to the stable voltage node through the feedback diode.

9. A switching power supply, characterized in that, The circuit is equipped with a non-isolated clamping circuit as described in any one of claims 1 to 7, and employs a method for feeding back high-voltage spike energy as described in claim 8.

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