Driving circuit of symmetrical half-bridge LLC

Abstract

The utility model discloses a drive circuit of a symmetrical half-bridge LLC. The drive circuit comprises an upper half-bridge drive circuit and a lower half-bridge drive circuit which have the same circuit structure. The upper half-bridge driving circuit comprises a driving transformer T1, a current-limiting resistor R1, a current-limiting resistor R2, a pull-down resistor R3, a first driving positive voltage clamping circuit, a first negative voltage clamping circuit, a first acceleration turn-off circuit and a first voltage stabilizing circuit; the lower half-bridge driving circuit comprises a driving transformer T1, a current-limiting resistor R4, a current-limiting resistor R5, a pull-down resistor R6, a second driving positive voltage clamping circuit, a second negative voltage clamping circuit, a second acceleration turn-off circuit and a second voltage stabilizing circuit. According to the utility model, a half-bridge circuit can be driven by using fewer devices, the clamping of the turn-on voltage and the turn-off voltage of the switching tube can be realized, extra electrolytic capacitor voltage stabilization is not needed, the switching tube is protected from being damaged due to abnormal driving, the switching tube is introduced to accelerate the turn-off of the circuit, the efficiency is improved, and the heating of the system is reduced.

Description

Technical Field

[0001] This utility model relates to the field of switching power supply technology, and in particular to a driving circuit for a symmetrical half-bridge LLC. Background Technology

[0002] In traditional switching power supply designs, hard switching technology leads to higher switching losses and electromagnetic interference (EMI), which limits the improvement of power supply efficiency and power density. To address these issues, soft switching technology has emerged, and LLC resonant circuits are an excellent example of soft switching technology.

[0003] The LLC resonant circuit consists of two inductors (L) and one capacitor (C). One inductor is the magnetizing inductance of the transformer, the other is a series inductance, and the capacitor is the resonant capacitor connected in series in the circuit. This structure enables the LLC resonant circuit to achieve zero-voltage switching (ZVS) over a wide range of input voltages and loads, thereby significantly reducing switching losses and improving conversion efficiency.

[0004] However, traditional symmetrical half-bridge LLC drive circuits are complex in structure and have many components, especially requiring two isolation transformers, which not only occupy a lot of space but also increase circuit costs. The complex structure also requires dual power supply. Therefore, there is an urgent need to provide a new type of symmetrical half-bridge LLC drive circuit to solve the above problems. Utility Model Content

[0005] The technical problem to be solved by this utility model is to provide a low-cost, bidirectional voltage-driven clamping, and easy-to-maintain symmetrical half-bridge LLC drive circuit.

[0006] To solve the above-mentioned technical problems, the present invention adopts a technical solution as follows: a driving circuit for a symmetrical half-bridge LLC is provided, including an upper half-bridge driving circuit, a lower half-bridge driving circuit and a voltage stabilizing capacitor C3 with the same circuit structure.

[0007] The upper half-bridge drive circuit includes a drive transformer T1, a current-limiting resistor R1, a current-limiting resistor R2, a pull-down resistor R3, a first drive positive voltage clamping circuit, a first negative voltage clamping circuit, a first acceleration shutdown circuit, and a first voltage regulation circuit.

[0008] One end of the current-limiting resistor R1 is connected to pin 4 of transformer T1, and the other end is connected to one end of the current-limiting resistor R2, the pull-down resistor R3, and the control terminal of the upper bridge; the input terminal of the upper bridge is connected to one end of capacitor C3, and the output terminal of the upper bridge is connected to the input terminal of the lower bridge; the other end of capacitor C3 is connected to the output terminal of the lower bridge.

[0009] The first driving positive voltage clamping circuit includes an input terminal and an output terminal. The input terminal is the negative terminal of the Zener diode ZD1, which is connected to pin 3 of the transformer T1 and the input terminal of the accelerated shutdown circuit. The output terminal is the positive terminal of the Zener diode ZD1, which is connected to the input terminal of the first driving negative voltage clamping circuit, the output terminal of the accelerated shutdown circuit, and one end of the first voltage regulator circuit.

[0010] The first driving negative voltage clamping circuit includes an input terminal and an output terminal. The input terminal is the negative terminal of the Zener diode ZD2, which is connected to the other end of the first voltage regulator circuit, the other end of the pull-down resistor R3, and the common terminal of the upper and lower bridges. The output terminal is the positive terminal of the Zener diode ZD2, which is connected to the output terminal of the driving positive voltage clamping circuit, the output terminal of the first acceleration shutdown circuit, and one end of the first voltage regulator circuit.

[0011] The first acceleration shutdown circuit includes a control terminal, an input terminal, and an output terminal. The control terminal is connected to pin 3 of transformer T1 and the input terminal of the first driving positive voltage clamping circuit. The input terminal is connected to resistor R2. The output terminal is connected to the output terminal of the first driving positive voltage clamping circuit, the output terminal of the first driving negative voltage clamping circuit, and one end of the first voltage regulator circuit.

[0012] One end of the first voltage regulator circuit is connected to the output terminal of the first acceleration shutdown circuit, the output terminal of the first driving positive voltage clamping circuit, and the output terminal of the first driving negative voltage clamping circuit.

[0013] In a preferred embodiment of the present invention, the lower half-bridge drive circuit includes a drive transformer T1, a current-limiting resistor R4, a current-limiting resistor R5, a pull-down resistor R6, a second positive drive clamping circuit, a second negative drive clamping circuit, a second acceleration shutdown circuit, and a second voltage regulator circuit.

[0014] One end of the current-limiting resistor R4 is connected to pin 6 of transformer T1, and the other end is connected to one end of the current-limiting resistor R5, the pull-down resistor R6, and the control terminal of the lower bridge; the input terminal of the lower bridge is connected to the output terminal of the upper bridge, and the output terminal of the lower bridge is connected to the other end of capacitor C3.

[0015] The second driving positive voltage clamping circuit includes an input terminal and an output terminal. The input terminal is the negative terminal of the Zener diode ZD3, which is connected to pin 5 of the transformer T1 and the input terminal of the second acceleration shutdown circuit. The output terminal is the positive terminal of the Zener diode ZD3, which is connected to the input terminal of the second driving negative voltage clamping circuit, the output terminal of the acceleration shutdown circuit, and one end of the second voltage regulator circuit.

[0016] The second driving negative voltage clamping circuit includes an input terminal and an output terminal. The input terminal is the negative terminal of the Zener diode ZD4, which is connected to the other end of the second voltage regulator circuit, the other end of the pull-down resistor R6, and the output terminal of the lower bridge. The output terminal is the positive terminal of the Zener diode ZD4, which is connected to the output terminal of the second driving positive voltage clamping circuit, the output terminal of the second acceleration turn-off circuit, and one end of the second voltage regulator circuit.

[0017] The second acceleration shutdown circuit includes a control terminal, an input terminal, and an output terminal. The control terminal is connected to pin 5 of transformer T1 and the input terminal of the second driving positive voltage clamping circuit. The input terminal is connected to resistor R5. The output terminal is connected to the output terminal of the second driving positive voltage clamping circuit, the output terminal of the second driving negative voltage clamping circuit, and one end of the first voltage regulator circuit.

[0018] One end of the second voltage regulator circuit is connected to the output terminal of the second acceleration shutdown circuit, the output terminal of the second driving positive voltage clamping circuit, and the output terminal of the second driving negative voltage clamping circuit.

[0019] Furthermore, either the first or second voltage regulator circuit uses a capacitor.

[0020] Furthermore, the first or second accelerated shutdown circuit employs a field-effect transistor.

[0021] Furthermore, the upper or lower bridge is a field-effect transistor or an insulated-gate bipolar transistor.

[0022] The beneficial effects of this utility model are:

[0023] (1) The symmetrical half-bridge LLC drive circuit of this utility model has the characteristics of simple and reliable structure, small space occupation, and realizes electrical isolation, which can be used in medium and high power applications; it only requires fewer components to clamp the positive and negative drive voltages of the symmetrical half-bridge LLC switching transistors, protects the drive voltage of the switching transistors from damage at a safe threshold, and adds an accelerated turn-off circuit to increase the turn-off speed, reduce switching losses, reduce heat generation, increase system reliability, and improve efficiency. Replacing the integrated chip circuit with a drive circuit composed of discrete components reduces maintenance costs;

[0024] (2) The circuit structure is relatively simple and reliable, and has electrical isolation function. With a fixed duty cycle, this drive circuit has a fast switching speed through reasonable parameter design; and the circuit only needs one power supply, that is, it works with a single power supply. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the drive circuit of the symmetrical half-bridge LLC of this utility model;

[0026] Figure 2 This is a schematic diagram of a preferred embodiment of the drive circuit for the symmetrical half-bridge LLC;

[0027] Figure 3 This is the circuit schematic diagram of the driving circuit of the symmetrical half-bridge LLC in working mode one.

[0028] Figure 4This is the circuit schematic diagram of the driving circuit of the symmetrical half-bridge LLC in working mode two. Detailed Implementation

[0029] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the scope of protection of the present invention.

[0030] Please see Figure 1 The embodiments of this utility model include:

[0031] A driving circuit for a symmetrical half-bridge LLC includes an upper half-bridge driving circuit, a lower half-bridge driving circuit, and a voltage-regulating capacitor C3, all with identical circuit structures. The upper half-bridge driving circuit includes a driving transformer T1, current-limiting resistors R1 and R2, a pull-down resistor R3, a first positive voltage clamping circuit, a negative voltage clamping circuit, a first acceleration shutdown circuit, and a first voltage-regulating circuit. The lower half-bridge driving circuit includes a driving transformer T1, current-limiting resistors R4 and R5, a pull-down resistor R6, a second positive voltage clamping circuit, a negative voltage clamping circuit, a second acceleration shutdown circuit, and a second voltage-regulating circuit. In this example, the first driving positive voltage clamping circuit uses Zener diode ZD1, the first driving negative voltage clamping circuit uses Zener diode ZD2, the second driving positive voltage clamping circuit uses Zener diode ZD3, and the second driving negative voltage clamping circuit uses Zener diode ZD4; the first accelerated turn-off circuit uses N-channel insulated-gate transistor Q1, and the second accelerated turn-off circuit uses N-channel insulated-gate transistor Q2; the first voltage regulator circuit uses capacitor C1, the second voltage regulator circuit uses capacitor C2, the upper bridge uses P-channel insulated-gate transistor Q3, and the lower bridge uses P-channel insulated-gate transistor Q4.

[0032] Specifically, in combination Figure 2 Taking the upper half-bridge drive circuit as an example, the input terminal is connected to pin 4 of the secondary side of transformer T1 and the common terminal of resistor R1, and the output terminal is connected to the control terminal of the upper bridge. One end of the current-limiting resistor R1 is connected to pin 4 of transformer T1, and the other end is connected to one end of the current-limiting resistor R2, the pull-down resistor R3, and the control terminal of the upper bridge (drain of switching transistor Q3); the input terminal (drain) of the upper bridge is connected to one end of capacitor C3, and the output terminal (source) of the upper bridge is connected to the input terminal (drain) of the lower bridge; the other end of capacitor C3 is connected to the output terminal (source) of the lower bridge.

[0033] The first driving positive voltage clamping circuit includes an input terminal and an output terminal. The input terminal is the negative terminal of the Zener diode ZD1, which is connected to pin 3 of the transformer T1 and the input terminal of the first acceleration turn-off circuit (the gate of the switching transistor Q1). The output terminal is the positive terminal of the Zener diode ZD1, which is connected to the input terminal of the first driving negative voltage clamping circuit (the positive terminal of the Zener diode ZD2), the output terminal of the acceleration turn-off circuit (the source of the switching transistor Q1), and one end of the first voltage regulator circuit (capacitor C1).

[0034] The first driving negative voltage clamping circuit includes an input terminal and an output terminal. The input terminal is the negative terminal of the Zener diode ZD2, which is connected to the other end of the first voltage regulator circuit (capacitor C1), the other end of the pull-down resistor R3, and the common terminal of the upper and lower bridges (the source of the switching transistor Q3). The output terminal is the positive terminal of the Zener diode ZD2, which is connected to the positive terminal of the Zener diode ZD1, the output terminal of the first acceleration turn-off circuit (the source of the switching transistor Q1), and one end of the first voltage regulator circuit (capacitor C1).

[0035] The first acceleration shutdown circuit includes a control terminal, an input terminal, and an output terminal. The control terminal (gate) is connected to pin 3 of transformer T1 and the input terminal of the first driving positive voltage clamping circuit (the negative terminal of Zener diode ZD1). The input terminal (drain) is connected to resistor R2. The output terminal (source) is connected to the output terminal of the first driving positive voltage clamping circuit (the positive terminal of Zener diode ZD1), the output terminal of the first driving negative voltage clamping circuit (the positive terminal of Zener diode ZD2), and one end of the first voltage regulating circuit (capacitor C1).

[0036] One end of the first voltage regulator circuit (capacitor C1) is connected to the output terminal of the first acceleration shutdown circuit (the source of the switching transistor Q1), the output terminal of the first driving positive voltage clamping circuit (the positive terminal of the Zener diode ZD1), and the output terminal of the first driving negative voltage clamping circuit (the positive terminal of the Zener diode ZD2).

[0037] The lower half-bridge drive circuit has the same circuit structure as the upper half-bridge drive circuit. Its input terminal is connected to pin 6 of the secondary side of transformer T1 and the common terminal of resistor R4, and its output terminal is connected to the control terminal of the lower bridge. The connections of other circuit components are not detailed here. Figure 2 As shown.

[0038] The two operating modes of the drive circuit for the symmetrical half-bridge LLC are described in detail below:

[0039] Combination Figure 3When a high-level output is observed between pins 2 and 1 of the primary side of transformer T1, a high-level output is also observed between pins 4 and 3 of the secondary side of transformer T1. The drive current flows along the curve indicated by the black arrow: Switch Q1 is off, Zener diode ZD2 is reverse-biased, clamping the turn-on voltage GS of switch Q3; Zener diode ZD1 is forward-biased; capacitor C1 regulates the voltage of Zener diode ZD2; and the upper half-bridge switch Q3 is on. At this time, switch Q4 in the lower half-bridge is off, Zener diode ZD3 is reverse-biased, clamping the turn-off voltage of switch Q4; Zener diode ZD4 is forward-biased; and capacitor C2 regulates the voltage. Switch Q2 is on, accelerating the turn-off of switch Q4 in the lower half-bridge.

[0040] Combination Figure 4 When the primary side of transformer T1 outputs a low level at pins 2 and 1, the secondary side of transformer T1 also outputs a low level between pins 4 and 3. The drive current flows along the curve indicated by the black arrow: Switch Q1 is turned on, accelerating the turn-off of switch Q3; Zener diode ZD2 is forward-biased, and Zener diode ZD1 is reverse-biased, clamping the turn-off voltage of switch Q3; capacitor C1 regulates the voltage of Zener diode ZD2; and the upper half-bridge Q3 is turned off. At this time, the lower bridge arm switch Q4 is turned on, switch Q2 is turned off, Zener diode ZD4 is reverse-biased, and Zener diode ZD3 is forward-biased; capacitor C2 acts as a voltage regulator.

[0041] The circuit described in this invention utilizes fewer components to drive a half-bridge circuit and clamps the turn-on and turn-off voltages of the switching transistor without requiring additional electrolytic capacitors for voltage regulation. This protects the switching transistor from damage due to driving abnormalities. Simultaneously, the introduction of an accelerated turn-off circuit for the switching transistor improves efficiency and reduces system heat generation. The circuit structure is simple and reliable, providing electrical isolation. With a fixed duty cycle, this drive circuit achieves a fast switching speed through reasonable parameter design. Furthermore, this circuit requires only one power supply and operates with a single power supply.

[0042] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made based on the description and drawings of this utility model, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. A drive circuit for a symmetric half-bridge LLC, characterized by, The upper half bridge driving circuit, the lower half bridge driving circuit and the voltage stabilizing capacitor C3 have the same circuit structure; The upper half bridge driving circuit comprises a driving transformer T1, a current limiting resistor R1, a current limiting resistor R2, a pull-down resistor R3, a first driving positive voltage clamping circuit, a first negative voltage clamping circuit, a first acceleration turn-off circuit and a first voltage stabilizing circuit; One end of the current limiting resistor R1 is connected to the 4-pin of the transformer T1, and the other end is connected with the current limiting resistor R2, one end of the pull-down resistor R3 and the control end of the upper bridge; The input end of the upper bridge is connected with one end of the capacitor C3, the output end of the upper bridge is connected with the input end of the lower bridge, and the other end of the capacitor C3 is connected with the output end of the lower bridge; The first driving positive voltage clamping circuit comprises an input end and an output end, the input end is the negative electrode of a voltage stabilizing tube ZD1, is connected with the 3-pin of the transformer T1 and the input end of the acceleration turn-off circuit, and the output end is the positive electrode of the voltage stabilizing tube ZD1, is connected with the input end of the first driving negative voltage clamping circuit, the output end of the acceleration turn-off circuit and one end of the first voltage stabilizing circuit; The first driving negative voltage clamping circuit comprises an input end and an output end, the input end is the negative electrode of a voltage stabilizing tube ZD2, is connected with the other end of the first voltage stabilizing circuit, the other end of the pull-down resistor R3 and the common end of the upper bridge and the lower bridge, and the output end is the positive electrode of the voltage stabilizing tube ZD2, is connected with the output end of the driving positive voltage clamping circuit, the output end of the first acceleration turn-off circuit and one end of the first voltage stabilizing circuit; The first acceleration turn-off circuit comprises a control end, an input end and an output end, the control end is connected with the 3-pin of the transformer T1 and the input end of the first driving positive voltage clamping circuit, the input end is connected with the resistor R2, and the output end is connected with the output end of the first driving positive voltage clamping circuit, the output end of the first driving negative voltage clamping circuit and one end of the first voltage stabilizing circuit; One end of the first voltage stabilizing circuit is connected with the output end of the first acceleration turn-off circuit, the output end of the first driving positive voltage clamping circuit and the output end of the first driving negative voltage clamping circuit.

2. The drive circuit for a symmetric half bridge LLC according to claim 1, characterized in that, The lower half bridge driving circuit comprises a driving transformer T1, a current limiting resistor R4, a current limiting resistor R5, a pull-down resistor R6, a second driving positive voltage clamping circuit, a second negative voltage clamping circuit, a second acceleration turn-off circuit and a second voltage stabilizing circuit; One end of the current limiting resistor R4 is connected to the 6-pin of the transformer T1, and the other end is connected with the current limiting resistor R5, one end of the pull-down resistor R6 and the control end of the lower bridge; The input end of the lower bridge is connected with the output end of the upper bridge, and the output end of the lower bridge is connected with the other end of the capacitor C3; The second driving positive voltage clamping circuit comprises an input end and an output end, the input end is the negative electrode of a voltage stabilizing tube ZD3, is connected with the 5-pin of the transformer T1 and the input end of the second acceleration turn-off circuit, and the output end is the positive electrode of the voltage stabilizing tube ZD3, is connected with the input end of the second driving negative voltage clamping circuit, the output end of the acceleration turn-off circuit and one end of the second voltage stabilizing circuit; The second driving negative voltage clamping circuit comprises an input end and an output end, the input end is the negative electrode of the voltage stabilizing tube ZD4, and is connected with the other end of the second voltage stabilizing circuit, the other end of the pull-down resistor R6 and the output end of the lower bridge; the output end is the positive electrode of the voltage stabilizing tube ZD4, and is connected with the output end of the second driving positive voltage clamping circuit, the output end of the second acceleration turn-off circuit and one end of the second voltage stabilizing circuit; The second acceleration turn-off circuit comprises a control end, an input end and an output end, the control end is connected with the 5th pin of the transformer T1 and the input end of the second driving positive voltage clamping circuit; the input end is connected with the resistor R5; The output end is connected with the output end of the second driving positive voltage clamping circuit, the output end of the second driving negative voltage clamping circuit and one end of the first voltage stabilizing circuit; One end of the second voltage stabilizing circuit is connected with the output end of the second acceleration turn-off circuit, the output end of the second driving positive voltage clamping circuit and the output end of the second driving negative voltage clamping circuit.

3. The drive circuit of a symmetrical half bridge LLC according to claim 1 or 2, characterized in that, The first voltage stabilizing circuit or the second voltage stabilizing circuit adopts a capacitor.

4. The drive circuit of a symmetrical half bridge LLC according to claim 1 or 2, characterized in that, The first acceleration turn-off circuit or the second acceleration turn-off circuit adopts a field effect transistor.

5. The drive circuit of a symmetrical half bridge LLC according to claim 1 or 2, characterized in that, The upper bridge or the lower bridge adopts a field effect transistor or an insulated gate bipolar transistor.

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