Driving circuit and switching power supply
By designing a transformer-isolated drive circuit and a voltage-limiting circuit, the high loss and high cost issues of SiC MOS drive circuits are solved, providing a stable negative voltage drive signal and realizing low-cost and high-efficiency SiC MOS drive, which is suitable for fields such as car charging, photovoltaic power generation and rail transportation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- MORNSUN GUANGZHOU SCI & TECH
- Filing Date
- 2025-03-26
- Publication Date
- 2026-05-12
AI Technical Summary
现有SiC MOS驱动电路存在高损耗、成本高的问题，尤其在半桥拓扑中驱动能力受限，且需要额外供电。
采用变压器隔离驱动电路，通过限压电路和负压模块设计，提供稳定的负压驱动信号，利用变压器次级绕组和限压电容构成的驱动回路，实现开关管的快速放电和稳定导通，避免额外电流回路和供电。
It achieves low-loss, low-cost SiC MOS driving, fast switching speed, reduced switching losses, is suitable for high-frequency designs, and requires no additional power supply.
Smart Images
Figure CN224233544U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of power electronics, and specifically relates to a drive circuit and a switching power supply. Background Technology
[0002] With the development of power electronics technology, SiC MOSFETs have been widely used in many fields such as car charging, photovoltaic power generation, rail transportation, and data centers due to their advantages such as high voltage withstand, fast switching speed, and low reverse recovery. To better utilize the conduction performance of SiC MOSFETs, the gate voltage during SiC MOSFET turn-on is typically controlled between 15 and 18V. Simultaneously, to avoid false turn-on, the gate voltage during SiC MOSFET turn-off is typically controlled between -3 and -5V. Using an integrated negative voltage isolation driver IC is costly, has limited driving capability, and requires additional power supply costs for half-bridge topologies.
[0003] Transformer-isolated drive solutions are a low-cost solution. Figure 1 The isolated SiC drive circuit shown is the scheme proposed in patent document CN 116388534 A. In this circuit, the secondary winding of the transformer forms a loop through two resistors R1 and R2. If the resistance values of R1 and R2 are small, it will result in a large load current in the secondary winding of the transformer, increasing drive losses and the burden on the preceding stage. If the resistance values of R1 and R2 are too large, the switching speed of the switching transistor Q1 will be limited, thereby affecting the switching speed of the replaced switching transistor U1 and resulting in large switching losses. In addition, in order to accelerate the switching process of the switching transistor Q1, the switching transistor Q1 is usually a low-voltage MOSFET, and the drive power supply it withstands is usually not too high.
[0004] In summary, CN 116388534 A uses a series voltage divider method with resistors R1 and R2 to obtain a suitable driving voltage for the switch Q1. As explained above, small resistor values R1 and R2 result in large load current and losses, while large resistor values R1 and R2 cause large switching losses. Therefore, there is an urgent need to provide a low-loss, low-cost, and stable SiC driving circuit solution that can fully utilize the excellent performance of SiC while bringing higher economic benefits. Utility Model Content
[0005] In view of this, the technical problem to be solved by this utility model is to provide a solution that at least partially solves one of the technical problems existing in the prior art.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] As a first aspect of this utility model, the technical solution of the provided driving circuit embodiment is as follows:
[0008] A driving circuit includes: a transformer core; a primary winding for inputting a driving signal source; a first primary winding and a first output circuit connected thereto; a second primary winding and a second output circuit connected thereto; one end of the first primary winding and one end of the second primary winding are opposite ends to each other.
[0009] The first output circuit and the second output circuit have the same structure, both including:
[0010] The system comprises a first diode, a first MOSFET, a voltage limiting circuit, and a negative voltage module. One end of the negative voltage module and the drain of the first MOSFET are simultaneously connected to one end of the corresponding secondary winding. The other end of the negative voltage module is used to connect to the gate of the driven switching transistor. The first end of the voltage limiting circuit and the cathode of the first diode are simultaneously connected to the other end of the corresponding secondary winding. The second end of the voltage limiting circuit is connected to the gate of the first MOSFET. The third end of the voltage limiting circuit, the anode of the first diode, and the source of the first MOSFET are connected together to connect to the source of the driven switching transistor. A first capacitor is provided between the first and second ends of the voltage limiting circuit, and a second capacitor is provided between the second and third ends.
[0011] When the input drive signal source is high, the first primary winding, the corresponding negative voltage module, the gate capacitor of the corresponding driven switch and the corresponding first diode constitute the first drive circuit to provide the first drive voltage.
[0012] When the input drive signal source is switched to a low level, the voltage across the first primary winding is zero. The gate capacitor of the corresponding driven switch, the corresponding negative voltage module, the first primary winding, and the corresponding voltage limiting circuit form a first loop. The gate capacitor of the corresponding driven switch discharges, and at the same time, the capacitor in the corresponding voltage limiting circuit charges, causing the voltage across the second capacitor in the corresponding voltage limiting circuit to rise and stably turn on the corresponding first MOS transistor through the corresponding voltage limiting circuit. This allows the corresponding negative voltage module to provide a negative drive voltage to the corresponding driven switch.
[0013] Preferably, the voltage limiting circuit further includes three diodes. The anode of the first diode and the cathode of the second diode are connected together and then connected to the second terminal of the voltage limiting circuit. The cathode of the first diode and one end of the first capacitor are connected together and then connected to the first terminal of the voltage limiting circuit. The anode of the second diode and the cathode of the third diode are simultaneously connected to the other end of the first capacitor. The anode of the third diode is connected to the third terminal of the voltage limiting circuit.
[0014] Preferably, the negative pressure module includes a capacitor and a resistor, with one end of the capacitor connected to one end of the negative pressure module and the other end connected to one end of the resistor, and the other end of the resistor connected to the other end of the negative pressure module.
[0015] Furthermore, the negative voltage module also includes a Zener diode, with the cathode of the Zener diode connected to one end of the negative voltage module and the anode connected to the other end of the capacitor.
[0016] Furthermore, the negative voltage module also includes a diode, with the cathode of the diode connected to one end of the negative voltage module and the anode connected to the other end of the resistor.
[0017] Furthermore, the driving circuit also includes a resistor, one end of which is connected to the connection point of the other end of the negative voltage module, the other end of which is connected to the anode of the first diode, the other end of the first charge storage unit, and the source of the first MOS transistor.
[0018] Furthermore, the driving circuit also includes two Zener diodes, one of which has its cathode connected to the other end of the negative voltage module and its anode connected to the anode of the other Zener diode, and the other Zener diode has its cathode connected to the junction of the anode of the first diode, the other end of the first charge storage unit, and the source of the first MOS transistor.
[0019] As a second aspect of this utility model, the technical solution of the provided switching power supply embodiment is as follows:
[0020] A switching power supply employing a half-bridge topology, wherein the switching power supply includes the driving circuit described in any of the first aspects above.
[0021] This utility model includes two complementary output circuits. Each output circuit forms a fast discharge circuit for the corresponding driven switch through the conduction of the corresponding first MOSFET, and generates a negative voltage drive signal for the corresponding driven switch during its non-conducting time to achieve controllable negative voltage turn-off. The second capacitor in the voltage limiting circuit stores the charge required to keep the first MOSFET conducting during the drive dead time. The specific working principle will be analyzed in detail with reference to specific embodiments. The beneficial effects of this utility model embodiment are as follows:
[0022] 1. When the input drive signal source of the drive circuit in this embodiment of the utility model is switched to a low level, the voltage across the first winding is zero. The voltage across the second capacitor in the corresponding voltage limiting circuit increases and the corresponding first MOS transistor is stably turned on through the corresponding voltage limiting circuit. It can provide a stable and reliable negative voltage drive signal for the corresponding driven switch transistor within the dead time, and has high reliability.
[0023] 2. When the input drive signal source of the drive circuit in the embodiment of this utility model is switched to a low level, the voltage across the first stage winding is zero. Through the stable conduction of the corresponding first MOS transistor, the negative voltage module provides a negative drive voltage to the corresponding driven switch transistor, thereby achieving fast switching speed, reducing switching losses, and meeting the requirements of high-frequency design.
[0024] 3. In the driving circuit of this utility model embodiment, a first capacitor and a second capacitor with voltage limiting are set in the voltage limiting circuit in the gate capacitor discharge circuit of each driven switch. By adjusting the capacitance ratio of the two capacitors in the voltage limiting circuit, the driving voltage and switching speed of the negative voltage clamp MOS (i.e., the first MOS transistor) can be adjusted. Furthermore, since the voltage limiting circuit uses capacitor voltage division, the discharge constant is small, and the switching speed of the negative voltage clamp MOS is fast, which is beneficial to reducing the switching loss of the main power MOS transistor (i.e., the driven switch).
[0025] 4. The driving circuit of this utility model embodiment does not add an extra current loop, can maintain low driving loss, and has strong driving capability;
[0026] 5. The driving circuit of this utility model embodiment adopts transformer isolation drive, which does not require additional power supply and has low cost. Attached Figure Description
[0027] Figure 1 The schematic diagram of the driving circuit proposed in patent document CN 116388534 A;
[0028] Figure 2 This is a specific schematic diagram of the driving circuit of this utility model;
[0029] Figure 3 for Figure 2 Waveform diagram of the circuit. Detailed Implementation
[0030] To make the above-mentioned objectives, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.
[0031] It should be noted that the terms "comprising" and "having" and any variations thereof described in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, including a series of components, unit circuits or control timings is not necessarily limited to those components, unit circuits or control timings that are explicitly listed, but may include components, unit circuits or control timings that are not explicitly listed or that are inherent to these circuits.
[0032] Furthermore, unless otherwise specified, the embodiments and features described in this application may be combined with each other.
[0033] It should be understood that, in the specification and claims, when an element is described as being "connected" to another element, that element may be "directly connected" to that other element or "connected" to that other element through a third element; when a step is described as being connected to another step, that step may be connected directly to that other step or connected to that other step through a third step.
[0034] The utility model concept of this application is that the driving circuit includes two complementary output circuits, providing reliable negative voltage turn-off during the non-conduction time. Each output circuit includes a negative voltage clamping MOSFET (i.e., the first MOSFET), a negative voltage clamping diode (i.e., the first diode), a voltage limiting circuit, and a negative voltage module. A first capacitor is disposed between the first and second terminals of the voltage limiting circuit, and a second capacitor is disposed between the second and third terminals. The output circuit forms a fast discharge circuit for the gate capacitance of the driven switch transistor through the conduction of the negative voltage clamping MOSFET, and generates a negative voltage driving signal for the driven switch transistor during the non-conduction time. The second capacitor in the voltage limiting circuit stores the charge required to keep the negative voltage clamping MOSFET Sa0 conducting during the drive dead time.
[0035] Based on the above-mentioned utility model concept, the present utility model provides a driving circuit, which includes: a transformer core; a primary winding for inputting a driving signal source; a first primary winding and a first output circuit connected thereto; a second secondary winding and a second output circuit connected thereto; one end of the first secondary winding and one end of the second secondary winding are opposite ends to each other;
[0036] The first output circuit and the second output circuit have the same structure, both including:
[0037] The circuit comprises a first diode, a first MOSFET, a voltage limiting circuit, and a negative voltage module. One end of the negative voltage module and the drain of the first MOSFET are simultaneously connected to one end of the corresponding secondary winding. The other end of the negative voltage module is used to connect to the gate of the driven switching transistor. The first end of the voltage limiting circuit and the cathode of the first diode are simultaneously connected to the other end of the corresponding secondary winding. The second end of the voltage limiting circuit is connected to the gate of the first MOSFET. The third end of the voltage limiting circuit, the anode of the first diode, and the source of the first MOSFET are connected together to connect to the source of the driven switching transistor. A first capacitor is provided between the first and second ends of the voltage limiting circuit, and a second capacitor is provided between the second and third ends of the voltage limiting circuit.
[0038] When the input drive signal source is high, the first primary winding, the corresponding negative voltage module, the gate capacitor of the corresponding driven switch and the corresponding first diode constitute the first drive circuit to provide the first drive voltage.
[0039] When the input drive signal source switches to a low level, the voltage across the primary winding is zero. The gate capacitor of the corresponding driven switch, the corresponding negative voltage module, the primary winding, and the corresponding voltage limiting circuit form a first loop. The gate capacitor of the corresponding driven switch discharges, and at the same time, the capacitor in the corresponding voltage limiting circuit charges, causing the voltage across the second capacitor in the corresponding voltage limiting circuit to rise and stably turn on the corresponding first MOSFET through the corresponding voltage limiting circuit. This allows the corresponding negative voltage module to provide a negative drive voltage to the corresponding driven switch.
[0040] Since the first end of the primary winding and the second end of the secondary winding are opposite ends, the first driving voltage provided by the first output circuit and the second driving voltage provided by the second output circuit are symmetrical and complementary driving signals. In practical applications, by controlling the emission time of the driving signal source input to the primary winding, a dead zone can be created between the two complementary driving signals, thereby avoiding the simultaneous conduction of the two switching transistors in the half-bridge circuit, which would cause them to burn out.
[0041] Figure 3 This is a circuit diagram of the first specific embodiment of the driving circuit of this utility model, wherein:
[0042] The primary winding is P1, the first secondary winding is S1, the second secondary winding is S2, the driven switch connected to the first output circuit is Sa1, and the driven switch connected to the second output circuit is Sa2.
[0043] The first diode in the first output circuit is Da1, and the first MOSFET is Sa0; the voltage limiting circuit in the first output circuit includes the first capacitor Ca01, the second capacitor Ca0, the diode Da01, the diode Da02, and the diode Da03; the negative voltage module in the first output circuit includes the capacitor Ca1, the resistor Ra1, the Zener diode Da2, and the diode Da3.
[0044] The first diode in the second output circuit is Db1, and the first MOSFET is Sb0; the voltage limiting circuit in the first output circuit includes the first capacitor Cb01, the second capacitor Cb0, diodes Db01, Db02, and Db03; the negative voltage module in the first output circuit includes capacitor Cb1, resistor Rb1, Zener diode Db2, and diode Db3.
[0045] Figure 3 for Figure 2 The waveform diagram shows that PWMSa1 is the 120kHz drive voltage output by the first output circuit, and PWMSa0 is the drive voltage of the negative clamp MOSFET Sa0 (i.e., the first MOSFET) in the first output circuit. The following is combined with... Figure 3 Waveform diagram Figure 2 A detailed analysis of the circuit's operating principle during one duty cycle is provided.
[0046] In the first stage, when the secondary winding S1 connected to the first output circuit is positively driven, the secondary winding S1, together with the negative voltage module, the gate capacitor of the switching transistor Sa1, and the negative voltage clamping diode Da1, forms the first driving circuit and outputs the first driving voltage required by the switching transistor Sa1. The driving voltage obtained by the switching transistor Sa1 is the voltage across the secondary winding S1 minus the voltage across the negative voltage module. Its advantage is that there are no resistive devices in the driving circuit, the loss is small, and the driving capability requirement of the transformer primary side can be reduced.
[0047] It should be noted that during the first one or two cycles of the drive circuit, capacitor Ca1 will be charged. During the subsequent normal operation, it is assumed that the voltage across capacitor Ca1 is stable, the current during charging and discharging is relatively small, and the drive process hardly consumes the charge in capacitor Ca1, so its discharge process does not need to be considered.
[0048] In the second stage, when the output voltage of the transformer secondary side S1 in the first drive circuit changes from positive voltage to 0, this is the dead time. The voltage across the transformer secondary winding S1 is zero. The gate capacitor of switch Sa1, the negative voltage module, the transformer secondary winding S1, the voltage limiting circuit, and the gate capacitor of switch Sa0 form the first discharge circuit for the gate capacitor of switch Sa1 at the moment when the drive voltage of switch Sa1 is turned off, and rapidly charge capacitors Ca0 and Ca01. When the gate voltage of switch Sa0 is charged to its turn-on threshold Vth0, it is critically turned on. After that, the negative voltage module clamps switch Sa1 with negative voltage through the conducting switch Sa0. The clamping voltage value is the voltage amplitude of the negative voltage module minus the turn-on threshold of switch Sa0. The advantage of this negative voltage control scheme is that it has a strong ability to maintain the negative voltage drive signal during the dead time and has high reliability.
[0049] It should be noted that during the dead time, the negative voltage clamping MOSFET Sa0 is preferably operating in the critical conduction state with a relatively large resistance to avoid current spikes in the discharge circuit; at the same time, the gate voltage of the switching transistor Sa0 discharges slowly, which can maintain the conduction of the switching transistor Sa0 during the dead time.
[0050] In the third stage, when the voltage across the secondary winding S1 of the transformer is negative, the voltage limiting circuit provides a driving voltage to the negative voltage clamping MOSFET Sa0. The negative voltage clamping MOSFET Sa0 is fully turned on and together with the negative voltage module, it forms a second discharge circuit to the gate capacitor of the switching transistor Sa1, thus forming a stable negative voltage driving voltage.
[0051] Figure 2 The voltage limiting circuit in the circuit constitutes the driving circuit for the negative voltage clamping MOSFET Sa0. The driving power obtained by the gate of the clamping MOSFET Sa0 can be adjusted by the voltage limiting circuit, providing adjustable driving voltage for the selection of the negative voltage clamping MOSFET.
[0052] In practical implementation, it is recommended that the voltage limiting circuit not include large-value resistors, so that the switching speed of the switching transistor Sao can be fast.
[0053] In addition, the driving voltage change rate can be adjusted by adjusting the voltage limit value of the voltage limiting circuit, the capacitance value of the first and second capacitors, or the impedance of the discharge circuit, so as to improve the driving speed of the switching transistor Sa1.
[0054] In addition, it should be noted that, Figure 2 In the circuit, Da2 is a Zener diode used to form a stable negative voltage drive signal V1; Da3 is a discharge diode that provides a discharge circuit for the gate capacitor of the switching transistor Sa1, enabling the rapid discharge of the gate capacitor of the switching transistor Sa1; Ra2 is an anti-static resistor for the switching transistor Sa1; a pair of Zener diodes connected in reverse series between the gate and source of the switching transistor Sa1 are overshoot protection devices to prevent damage to the switching transistor Sa1 due to excessively high or low drive voltage.
[0055] This utility model embodiment also provides a switching power supply, which adopts a half-bridge topology and includes any of the above-mentioned driving circuits.
[0056] The above are merely embodiments of this utility model. It should be particularly noted that the above embodiments should not be regarded as limitations on this utility model. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of this utility model, and these improvements and modifications should also be regarded as protection scope of this utility model.
Claims
1. A driving circuit, characterized in that, include: Transformer magnetic core; The primary winding is used to input the drive signal source; The primary winding and the first output circuit connected to it; The second-stage winding and the second output circuit connected thereto; One end of the first-stage winding and one end of the second-stage winding are opposite-named ends; The first output circuit and the second output circuit have the same structure, both including: The system comprises a first diode, a first MOSFET, a voltage limiting circuit, and a negative voltage module. One end of the negative voltage module and the drain of the first MOSFET are simultaneously connected to one end of the corresponding secondary winding. The other end of the negative voltage module is used to connect to the gate of the driven switching transistor. The first end of the voltage limiting circuit and the cathode of the first diode are simultaneously connected to the other end of the corresponding secondary winding. The second end of the voltage limiting circuit is connected to the gate of the first MOSFET. The third end of the voltage limiting circuit, the anode of the first diode, and the source of the first MOSFET are connected together to connect to the source of the driven switching transistor. A first capacitor is provided between the first and second ends of the voltage limiting circuit, and a second capacitor is provided between the second and third ends. When the input drive signal source is high, the first primary winding, the corresponding negative voltage module, the gate capacitor of the corresponding driven switch and the corresponding first diode constitute the first drive circuit to provide the first drive voltage. When the input drive signal source is switched to a low level, the voltage across the first primary winding is zero. The gate capacitor of the corresponding driven switch, the corresponding negative voltage module, the first primary winding, and the corresponding voltage limiting circuit form a first loop. The gate capacitor of the corresponding driven switch discharges, and at the same time, the capacitor in the corresponding voltage limiting circuit charges, causing the voltage across the second capacitor in the corresponding voltage limiting circuit to rise and stably turn on the corresponding first MOS transistor through the corresponding voltage limiting circuit. This allows the corresponding negative voltage module to provide a negative drive voltage to the corresponding driven switch.
2. The driving circuit according to claim 1, characterized in that: The voltage limiting circuit also includes three diodes. The anode of the first diode and the cathode of the second diode are connected together and then connected to the second terminal of the voltage limiting circuit. The cathode of the first diode and one end of the first capacitor are connected together and then connected to the first terminal of the voltage limiting circuit. The anode of the second diode and the cathode of the third diode are simultaneously connected to the other end of the first capacitor. The anode of the third diode is connected to the third terminal of the voltage limiting circuit.
3. The driving circuit according to claim 1, characterized in that: The negative pressure module includes a capacitor and a resistor. One end of the capacitor is connected to one end of the negative pressure module, and the other end is connected to one end of the resistor. The other end of the resistor is connected to the other end of the negative pressure module.
4. The driving circuit according to claim 3, characterized in that: The negative voltage module also includes a Zener diode, with the cathode of the Zener diode connected to one end of the negative voltage module and the anode connected to the other end of the capacitor.
5. The driving circuit according to claim 3 or 4, characterized in that: The negative voltage module also includes a diode, with the cathode of the diode connected to one end of the negative voltage module and the anode connected to the other end of the resistor.
6. The driving circuit according to claim 1, characterized in that: The driving circuit also includes a resistor, one end of which is connected to the other end of the negative voltage module, and the other end is connected to the junction of the anode of the first diode, the other end of the first charge storage unit, and the source of the first MOS transistor.
7. The driving circuit according to claim 1 or 6, characterized in that: The driving circuit also includes two Zener diodes. The cathode of one Zener diode is connected to the other end of the negative voltage module, and the anode is connected to the anode of the other Zener diode. The cathode of the other Zener diode is connected to the junction of the anode of the first diode, the other end of the first charge storage unit, and the source of the first MOS transistor.
8. A switching power supply, wherein the switching power supply adopts a half-bridge topology, characterized in that: The switching power supply includes the driving circuit described in any one of claims 1 to 7.