Supercritical voltage boosting circuit and switching power supply

Abstract

The application relates to the technical field of power supply, and provides a supercritical voltage boosting circuit and a switching power supply. The application comprises a rectification and filtration unit, a main switch unit comprising a first switch tube, a gate of the first switch tube being connected with a driving signal end, a transformer unit comprising a first transformer and a second transformer, a main winding of the first transformer being connected with the rectification and filtration unit and the main switch unit, a main winding of the second transformer being coupled with the first transformer, an auxiliary switch unit comprising a second switch tube, a gate of the second switch tube being connected with a secondary winding of the first transformer, a drain of the second switch tube being connected with a voltage boosting output end, a trigger control unit comprising a transistor control circuit connected with a source of the second switch tube, and a diode group connected through the main winding of the second transformer. The application greatly reduces current and voltage peaks in the output power supply and greatly reduces power supply noise.

Description

Technical Field

[0001] This application relates to the field of power supply technology, specifically to a supercritical boost circuit and a switching power supply. Background Technology

[0002] A switching power supply is a type of power supply that converts electrical energy using high-frequency switching technology. It is widely used in electronic equipment, communication systems, and industrial control. While switching power supplies offer advantages such as small size, light weight, and high efficiency, their inherent switching action results in high-frequency ripple in the output voltage. This high-frequency ripple is one of the main sources of power supply noise. Compared to linear regulated power supplies, switching power supplies naturally have a higher power supply noise level. Unlike ordinary operating environments, in precision measuring equipment, power supply noise has a significant impact on measurement results, and can even completely drown out the measurement signal.

[0003] In typical critical mode, the voltage drop edge has a brief period of free swing before the subsequent rapid steep change is caused by the lower transistor turning on. For example... Figure 1 , 2 The diagram shows a traditional critical boost circuit. When the lower transistor Q1 is turned on (corresponding to...) Figure 2 At point e), Uds is very small, the bus magnetizes the inductor, and the current in the inductor continuously increases. When Q1 is turned off (corresponding to...), Figure 2 At point a), Uds gradually increases, and at point b, the upper transistor D turns on, charging the capacitor and simultaneously superimposing the input voltage to boost the voltage and supply power to subsequent circuits. At point c, the magnetic energy in the inductor is completely released, entering a critical state, and the Uds voltage of Q1 slowly decreases. At point e, the lower transistor Q1 turns on again, and this cycle repeats. Starting from point e, the falling edge of Uds is steep, generating voltage and current spikes, which introduce noise into the output of the switching power supply.

[0004] Therefore, how to solve the noise problem of switching power supplies is a problem that needs to be addressed. Summary of the Invention

[0005] In view of this, the embodiments of this application provide a supercritical boost circuit and a switching power supply, which can significantly reduce current and voltage spikes in the output power supply, greatly reduce power supply noise, and achieve the indicators required for precision measurement.

[0006] A first aspect of this application provides a supercritical boost circuit, comprising:

[0007] Rectifier and filter unit;

[0008] The main switching unit includes a first switching transistor, the gate of which is connected to a drive signal terminal;

[0009] The transformer unit includes a first transformer and a second transformer. The main winding of the first transformer is connected to the rectifier and filter unit and the main switch unit. The main winding of the second transformer is coupled to the first transformer.

[0010] An auxiliary switching unit includes a second switching transistor, the gate of which is connected to the secondary winding of the first transformer, and the drain of which is connected to the boost output terminal.

[0011] The trigger control unit includes a transistor control circuit connected to the source of the second switching transistor; and a diode group connected via the main winding of the second transformer.

[0012] In one embodiment, one end of the main winding of the first transformer is connected to a rectifier and filter unit, and the other end is connected to a second transformer and the drain of the first switching transistor. The source of the first switching transistor is grounded through a first resistor.

[0013] In one embodiment, one end of the secondary winding of the first transformer is connected to one end of the second capacitor, the other end of the second capacitor is connected to the cathode of the first diode and one end of the third resistor, the anode of the first diode is connected to one end of the main winding of the second transformer, and the other end of the main winding of the second transformer is connected to the source of the second switching transistor.

[0014] In one embodiment, the trigger control unit includes a first transistor and a second transistor, wherein the collector of the first transistor is connected to the base of the second transistor, and the collector of the second transistor is connected to the base of the first transistor.

[0015] In one embodiment, the emitter of the first transistor is connected to the other end of the third resistor, the collector is connected to one end of the third capacitor and one end of the fourth resistor, the emitter of the second transistor is connected to the drain of the second switching transistor and the other end of the third capacitor, and the other end of the fourth resistor is connected to the diode group.

[0016] In one embodiment, the diode group includes a second diode and a third diode. The anode of the second diode is connected to one end of the main winding of the second transformer, and the cathode of the second diode is connected to the anode of the third diode. The cathode of the third diode is connected to one end of a second resistor and the other end of a fourth resistor. The other end of the second resistor is connected to one end of the main winding of the second transformer.

[0017] In one embodiment, the rectifier-filter unit includes a first capacitor, the positive terminal of which is connected to the rectifier-filter output terminal, and the negative terminal is grounded.

[0018] In one embodiment, a fourth capacitor is also included, wherein the positive terminal of the fourth capacitor is connected to the boost output terminal and the negative terminal is grounded.

[0019] A second aspect of this application provides a switching power supply, including a supercritical boost circuit as provided in the first aspect.

[0020] The first aspect of this application provides a supercritical boost circuit, including a rectifier and filter unit; a main switching unit including a first switching transistor, the gate of which is connected to a drive signal terminal; a transformer unit including a first transformer and a second transformer, the main winding of the first transformer being connected to the rectifier and filter unit and the main switching unit, and the main winding of the second transformer being coupled to the first transformer; an auxiliary switching unit including a second switching transistor, the gate of which is connected to the secondary winding of the first transformer, and the drain of which is connected to the boost output terminal; a trigger control unit including a transistor control circuit connected to the source of the second switching transistor; and a diode group connected via the main winding of the second transformer. This circuit adjusts the steep voltage drop formed when the rectifier diode is turned off in ordinary critical mode to a gentle slope of MOSFET drain voltage drop at a controllable turn-off time, thereby significantly reducing current and voltage spikes in the output power supply and greatly reducing power supply noise. The noise is reduced from 1% in ordinary switching power supplies to 0.1% or even 0.01%, expanding the application of switching power supplies in precision measurement equipment.

[0021] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the connection of an existing critical boost circuit;

[0024] Figure 2 This is a waveform diagram of the lower transistor voltage in an existing critical boost circuit;

[0025] Figure 3 This is a connection diagram of a supercritical boost circuit provided in an embodiment of this application;

[0026] Figure 4 This is a waveform diagram of the lower transistor voltage in the supercritical boost circuit of this application. Detailed Implementation

[0027] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0028] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0030] like Figure 3 As shown, this application provides a supercritical boost circuit, including:

[0031] Rectifier and filter unit;

[0032] The main switching unit includes a first switching transistor Q1, the gate of which is connected to a drive signal terminal;

[0033] The transformer unit includes a first transformer T1 and a second transformer T2. The main winding of the first transformer T1 is connected to the rectifier and filter unit and the main switch unit. The main winding of the second transformer T2 is coupled to the first transformer T1.

[0034] The auxiliary switching unit includes a second switching transistor Q2, the gate of which is connected to the secondary winding of the first transformer T1, and the drain of which is connected to the boost output terminal.

[0035] The trigger control unit includes a transistor control circuit connected to the source of the second switch Q2;

[0036] The diode group is connected through the main winding of the second transformer T2.

[0037] This application embodiment, through the coordinated design of Q1, Q2, trigger circuits TR1 / TR2, and current transformer L2 in the supercritical boost circuit, dynamically controls the turn-on and turn-off times of Q2 when Q1 is turned off. This transforms the steep voltage drop formed when the rectifier diode is turned off in ordinary critical mode into a gentle slope of MOSFET drain voltage drop at a controllable turn-off time. This significantly reduces current and voltage spikes in the output power supply, greatly minimizing power supply noise. Noise is reduced from 1% in ordinary switching power supplies to 0.1% or even 0.01%, expanding the application of switching power supplies in precision measurement equipment.

[0038] In one embodiment, one end of the main winding of the first transformer T1 is connected to a rectifier and filter unit, and the other end is connected to the drain of the second transformer T2 and the first switching transistor Q1. The source of the first switching transistor Q1 is grounded through the first resistor R1.

[0039] In one embodiment, one end of the secondary winding of the first transformer T1 is connected to one end of the second capacitor C2, the other end of the second capacitor C2 is connected to the cathode of the first diode D1 and one end of the third resistor R3, the anode of the first diode D1 is connected to one end of the main winding of the second transformer T2, and the other end of the main winding of the second transformer T2 is connected to the source of the second switching transistor Q2.

[0040] This application embodiment uses a composite trigger circuit composed of TR1 and TR2 to amplify the trigger signal and shorten the response time to the nanosecond level with a dual-transistor cascade structure. It quickly establishes the turn-off voltage at the gate of Q2, eliminates the voltage sway noise caused by the delay in traditional single-transistor triggering, and improves the circuit's anti-interference capability.

[0041] In one embodiment, the trigger control unit includes a first transistor TR1 and a second transistor TR2, wherein the collector of the first transistor TR1 is connected to the base of the second transistor TR2, and the collector of the second transistor TR2 is connected to the base of the first transistor TR1.

[0042] In one embodiment, the emitter of the first transistor TR1 is connected to the other end of the third resistor R3, and the collector is connected to one end of the third capacitor C3 and one end of the fourth resistor R4. The emitter of the second transistor TR2 is connected to the drain of the second switch Q2 and the other end of the third capacitor C3. The other end of the fourth resistor R4 is connected to the diode group.

[0043] In one embodiment, the diode group includes a second diode D2 and a third diode D3. The anode of the second diode D2 is connected to one end of the main winding of the second transformer T2, and the cathode of the second diode D2 is connected to the anode of the third diode D3. The cathode of the third diode is connected to one end of the second resistor R2 and the other end of the fourth resistor. The other end of the second resistor R2 is connected to one end of the main winding of the second transformer.

[0044] In one embodiment, the rectifier-filter unit includes a first capacitor C1, the positive terminal of which is connected to the rectifier-filter output terminal, and the negative terminal is grounded.

[0045] In one embodiment, a fourth capacitor C4 is also included, wherein the positive terminal of the fourth capacitor C4 is connected to the boost output terminal and the negative terminal is grounded.

[0046] In applications, such as Figure 4 As shown, when Q1 is turned off ( Figure 4 At point a), the Uds voltage of Q1 begins to rise, the voltage at pin 3 of T1 rises, the voltage at pin 2 rises, and the voltage flows through C2 and R3 to the gate of Q2. At point b, Q2 turns on, and the energy stored in T1 enters the boosted DC circuit to charge capacitor C4. After the energy stored in T1 is released, Q2 remains on, C4 discharges in reverse, and the energy returns to the bus through L2 (multiplexed by T2) and T1.

[0047] L2 is a current transformer that samples the reverse discharge current. When the sampled current reaches a certain value, the corresponding... Figure 4 At point d, TR1 and TR2 together form the trigger circuit and conduct. Q2 turns off due to the decrease in gate-source voltage. The Uds voltage of the lower transistor Q1 decreases slowly until point e, at which point Q1 turns on again. The reverse current in T1 forms a relatively smooth falling edge. Therefore, by appropriately selecting the magnitude of the sampling current of the current transformer, the conduction time of TR1 and TR2 can be artificially controlled, thereby controlling the turn-off time of Q2.

[0048] contrast Figure 2 and Figure 4 The steep slope of the Uds voltage drop edge of the lower transistor Q1 becomes gentler, voltage and current spikes are effectively controlled, and the power supply output noise index is greatly improved.

[0049] Specifically, the working process of this circuit is as follows:

[0050] Phase 1: Main switch Q1 conducts and stores energy (corresponding to segment ea in the waveform diagram)

[0051] When the drive signal is applied to the gate of the main switch Q1 to turn it on, the rectified and filtered DC voltage at the input terminal forms a current loop through the main winding (pins 1 to 3) of transformer T1. At this time, the main winding of T1 acts as an energy storage inductor, and its core begins to linearly store magnetic energy, causing the current flowing through the drain to the source of Q1 to continuously increase. The secondary winding (pin 2) of T1 generates a negative voltage due to electromagnetic induction. This voltage signal is transmitted to the cathode of diode D1 through the coupling effect of capacitor C2. After D1 turns on, it applies the negative voltage signal of the secondary winding to one end of resistor R3. The other end of R3 is connected to the gate of auxiliary switch Q2, forming a reverse bias voltage to ensure that Q2 remains reliably off during this stage. At the same time, transistor TR1 in the trigger circuit is in the off state because there is no forward bias voltage at its base, and the base of transistor TR2 is grounded through resistor R2, maintaining its off state.

[0052] Phase Two: Q1 Turn-Off and Energy Transfer (Waveform Segment ab)

[0053] When the drive signal of Q1 goes low and enters the off state, the current flowing through the main winding of T1 changes abruptly, causing the voltage at pin 3 of T1 to rise rapidly. At this time, the gate-source drive voltage of Q2 has not yet been established through the C2 / R3 network (the gate voltage is below the threshold). Its internal parasitic diode is in reverse cutoff state because the anode (drain) voltage is lower than the cathode (source connected to the T2 winding), resulting in no current flowing to the output capacitor C4 in the boost circuit. The secondary winding (pin 2) of T1 generates a positive voltage due to magnetic coupling. This voltage signal is coupled to resistor R3 through capacitor C2, but because the gate drive of Q2 has not reached the conduction threshold, Q2 remains off during this stage.

[0054] Phase 3: Reverse Discharge and Current Sampling (waveform bd segment)

[0055] When the voltage at pin 3 of T1 rises above the voltage of C4 (point b), the parasitic diode of Q2 conducts first. Subsequently, the gate drive voltage of Q2 is established through the C2 / R3 network, turning Q2 on. At this time, the reverse electromotive force of the main winding of T2 charges the output capacitor C4 through the reverse conduction of Q2, boosting the input voltage to the DC level after the step-up. In the early stage of this phase (segment bc), T1 stores energy and releases it through the active conduction of Q2, with current flowing to C4 to form a forward charging current. When the energy stored in T1 is completely released (point c), Q2 remains on, and capacitor C4 forms a reverse discharge circuit through the main winding of current transformer L2 and the main winding of transformer T1 (segment cd). As a current transformer, L2's secondary winding senses the reverse discharge current in real time and transmits the sampling signal to one end of resistor R4. This current signal is converted into a voltage signal across resistor R4, and after being filtered by capacitor C3, it is applied to the base of transistor TR2 in the trigger circuit. When the reverse discharge current reaches the preset threshold, the voltage across resistor R4 exceeds the conduction threshold of transistor TR2.

[0056] Phase 4: Triggering shutdown control (waveform segment de)

[0057] When the base voltage of transistor TR2 reaches the turn-on threshold, TR2 enters saturation conduction. Its collector current flows through resistor R1 and generates a voltage drop, giving the base of transistor TR1 a forward bias voltage. After TR1 turns on, a low-impedance path is formed between its collector and emitter, pulling the gate-source voltage of Q2 down to ground potential, and Q2 turns off. Subsequently, the main winding of transformer T1 and the drain-source parasitic capacitance of Q1 form a resonant circuit, forcing the drain-source voltage of Q1 to decrease at a gradual rate. When the voltage drops to near zero, the drive signal turns Q1 back on, achieving zero-voltage turn-on and starting the next operating cycle. During this process, the reverse current in the main winding of T1 gradually decays through the resonant circuit, forming a smooth voltage drop edge, thereby eliminating voltage spikes and current peaks in the traditional critical mode.

[0058] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A supercritical boost circuit, characterized in that, include: Rectifier and filter unit; The main switching unit includes a first switching transistor, the gate of which is connected to a drive signal terminal; The transformer unit includes a first transformer and a second transformer. The main winding of the first transformer is connected to the rectifier and filter unit and the main switch unit. The main winding of the second transformer is coupled to the first transformer. An auxiliary switching unit includes a second switching transistor, the gate of which is connected to the secondary winding of the first transformer, and the drain of which is connected to the boost output terminal. The trigger control unit includes a transistor control circuit connected to the source of the second switching transistor; The diode group is connected through the main winding of the second transformer.

2. The supercritical boost circuit as described in claim 1, characterized in that, One end of the main winding of the first transformer is connected to the rectifier and filter unit, and the other end is connected to the second transformer and the drain of the first switching transistor. The source of the first switching transistor is grounded through the first resistor.

3. The supercritical boost circuit as described in claim 1, characterized in that, One end of the secondary winding of the first transformer is connected to one end of the second capacitor, the other end of the second capacitor is connected to the cathode of the first diode and one end of the third resistor, the anode of the first diode is connected to one end of the main winding of the second transformer, and the other end of the main winding of the second transformer is connected to the source of the second switching transistor.

4. The supercritical boost circuit according to claim 3, characterized in that: The trigger control unit includes a first transistor and a second transistor, wherein the collector of the first transistor is connected to the base of the second transistor, and the collector of the second transistor is connected to the base of the first transistor.

5. The supercritical boost circuit according to claim 4, characterized in that: The emitter of the first transistor is connected to the other end of the third resistor, and the collector is connected to one end of the third capacitor and one end of the fourth resistor. The emitter of the second transistor is connected to the drain of the second switching transistor and the other end of the third capacitor. The other end of the fourth resistor is connected to the diode group.

6. The supercritical boost circuit according to claim 5, characterized in that: The diode group includes a second diode and a third diode. The anode of the second diode is connected to one end of the main winding of the second transformer, and the cathode of the second diode is connected to the anode of the third diode. The cathode of the third diode is connected to one end of a second resistor and the other end of a fourth resistor. The other end of the second resistor is connected to one end of the main winding of the second transformer.

7. The supercritical boost circuit according to claim 1, characterized in that: The rectifier and filter unit includes a first capacitor, the positive terminal of which is connected to the rectifier and filter output terminal, and the negative terminal is grounded.

8. The supercritical boost circuit according to claim 1, characterized in that: It also includes a fourth capacitor, the positive terminal of which is connected to the boost output terminal and the negative terminal is grounded.

9. A switching power supply, characterized in that, Includes the supercritical boost circuit as described in any one of claims 1-8.

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