LLC resonant converter control circuit and LLC resonant conversion circuit

Abstract

This invention provides an LLC resonant converter control circuit and an LLC resonant converter circuit. The LLC resonant converter control circuit includes an output current sampling module, an output voltage feedback module, and a power controller connected in sequence. The output current sampling module collects the current signal output by the LLC resonant converter and amplifies the current signal according to a preset ratio before inputting it to the output voltage feedback module. The output voltage feedback module converts the amplified current signal into a voltage signal, compares the voltage signal with a reference voltage, increases the output feedback voltage when the voltage signal is lower than the reference voltage, and decreases the output feedback voltage when the voltage signal is higher than the reference voltage. The power controller receives the feedback voltage and adjusts the operating frequency of the LLC resonant converter according to the feedback voltage. The LLC resonant converter control circuit of this invention can avoid intermittent driving of the LLC resonant converter under no-load or light-load conditions and reduce the dynamic overshoot swing of the LLC resonant converter.

Description

Technical Field

[0001] This invention relates to the field of control circuits, and more specifically, to an LLC resonant converter control circuit and an LLC resonant converter circuit. Background Technology

[0002] In existing technologies, LLC resonant converters have become one of the mainstream DC-DC converters due to their high efficiency, high power density, and soft-switching characteristics. However, under simple closed-loop control, LLC resonant converters can experience large output ripple under no-load or light-load conditions, or during intermittent drive states. Furthermore, when the intermittent drive frequency is within the audio frequency range, it can produce a whistling sound. When switching between no-load and full-load output states, the large change in operating frequency can cause excessive dynamic overshoot swing of the load. Summary of the Invention

[0003] In view of the above problems, the present invention provides an LLC resonant converter control circuit and an LLC resonant converter circuit to avoid intermittent driving of the LLC resonant converter under no-load or light-load conditions, and to reduce the dynamic overshoot swing of the LLC resonant converter.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An LLC resonant converter control circuit includes an output current sampling module, an output voltage feedback module, and a power controller connected in sequence.

[0006] The output current sampling module is used to collect the current signal output by the LLC resonant converter, and amplify the current signal according to a preset ratio before inputting it to the output voltage feedback module;

[0007] The output voltage feedback module is used to convert the amplified current signal into a voltage signal, compare the voltage signal with a reference voltage, increase the output feedback voltage when the voltage signal is lower than the reference voltage, and decrease the output feedback voltage when the voltage signal is higher than the reference voltage.

[0008] The power controller is used to receive the feedback voltage and adjust the operating frequency of the LLC resonant converter according to the feedback voltage.

[0009] Preferably, in the LLC resonant converter control circuit, the power controller increases the operating frequency of the LLC resonant converter when the received feedback voltage increases, and decreases the operating frequency of the LLC resonant converter when the received feedback voltage decreases.

[0010] Preferably, in the LLC resonant converter control circuit, the output current sampling module includes a differential operational amplifier circuit.

[0011] Preferably, in the LLC resonant converter control circuit, the differential operational amplifier circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a differential operational amplifier, and a first capacitor;

[0012] The negative input pin of the differential operational amplifier is connected to the first resistor, and the positive input pin is connected to the second resistor. The current signal output by the LLC resonant converter is acquired through the first resistor and the second resistor.

[0013] One end of the third resistor is connected to the positive input pin of the differential operational amplifier, and the other end is grounded;

[0014] One end of the fourth resistor is connected to the negative input pin of the differential operational amplifier, and the other end is connected to the output pin of the differential operational amplifier.

[0015] One end of the first capacitor is connected to the drive power supply pin of the differential operational amplifier, and the other end is grounded.

[0016] Preferably, in the LLC resonant converter control circuit, the output voltage feedback module includes a voltage divider circuit and a voltage comparison circuit connected in sequence;

[0017] The voltage divider circuit is used to receive the current signal, convert the current signal into a voltage signal, and perform voltage division.

[0018] The voltage comparison circuit is used to receive the voltage signal after voltage division, compare the voltage signal with a reference voltage, increase the output feedback voltage when the voltage signal is lower than the reference voltage, and decrease the output feedback voltage when the voltage signal is higher than the reference voltage.

[0019] Preferably, in the LLC resonant converter control circuit, the voltage comparison circuit includes a voltage comparator and a second capacitor;

[0020] The positive input terminal of the voltage comparator is used to receive the reference voltage, the negative input terminal is used to receive the voltage signal, and the output pin is used to connect to the power controller.

[0021] One end of the second capacitor is connected to the drive power supply pin of the voltage comparator, and the other end is grounded.

[0022] Preferably, in the LLC resonant converter control circuit, the voltage divider circuit includes a fifth resistor, a sixth resistor, and a seventh resistor;

[0023] One end of the fifth resistor is used to connect to the negative input terminal, and the other end is used to receive the amplified current signal;

[0024] One end of the sixth resistor is used to connect to the negative input terminal, and the other end is used to connect to the voltage output terminal;

[0025] One end of the seventh resistor is used to connect to the negative input terminal, and the other end is used to ground.

[0026] Preferably, in the LLC resonant converter control circuit, the voltage comparison circuit includes a TL431.

[0027] The present invention also provides an LLC resonant converter circuit, including an LLC resonant converter and an LLC resonant converter control circuit connected to the LLC resonant converter.

[0028] Preferably, in the LLC resonant converter circuit, the LLC resonant converter includes a full-bridge LLC resonant converter and a half-bridge LLC resonant converter.

[0029] This invention provides a control circuit for an LLC resonant converter. The control circuit includes an output current sampling module, an output voltage feedback module, and a power controller connected in sequence. The output current sampling module collects the current signal output by the LLC resonant converter and amplifies the current signal according to a preset ratio before inputting it to the output voltage feedback module. The output voltage feedback module converts the amplified current signal into a voltage signal, compares the voltage signal with a reference voltage, increases the output feedback voltage when the voltage signal is lower than the reference voltage, and decreases the output feedback voltage when the voltage signal is higher than the reference voltage. The power controller receives the feedback voltage and adjusts the operating frequency of the LLC resonant converter according to the feedback voltage. This LLC resonant converter control circuit can increase the operating frequency of the LLC resonant converter when it is lightly loaded or unloaded, thus avoiding intermittent drive. When the LLC resonant converter transitions from unloaded to heavy load, it can decrease the operating frequency of the LLC resonant converter to reduce dynamic overshoot.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0031] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope of protection of the present invention. In the various drawings, similar components are numbered similarly.

[0032] Figure 1This is a schematic diagram of the structure of an LLC resonant converter control circuit provided in Embodiment 1 of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of an LLC resonant converter control circuit provided in Embodiment 2 of the present invention;

[0034] Figure 3 This is a schematic diagram of the structure of an LLC resonant converter control circuit provided in Embodiment 3 of the present invention. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0036] The components of the embodiments of the invention described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0037] In the following, the terms “comprising,” “having,” and their cognates, which may be used in various embodiments of the invention, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as excluding, firstly, the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more features, numbers, steps, operations, elements, components, or combinations thereof.

[0038] Furthermore, the terms "first," "second," and "third" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0039] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the invention pertain. Terms (such as those defined in commonly used dictionaries) shall be interpreted as having the same meaning as in their contextual meaning in the relevant technical field and shall not be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of the invention.

[0040] Example 1

[0041] Figure 1This is a schematic diagram of the structure of an LLC resonant converter control circuit provided in Embodiment 1 of the present invention.

[0042] The LLC resonant converter control circuit 100 includes an output current sampling module 110, an output voltage feedback module 120, and a power controller 130 connected in sequence.

[0043] The output current sampling module 110 is used to collect the current signal output by the LLC resonant converter, and amplify the current signal according to a preset ratio before inputting it to the output voltage feedback module 120.

[0044] In this embodiment of the invention, the LLC resonant converter, due to its high efficiency, high power density, and soft-switching characteristics, has become one of the mainstream DC-DC converters. However, under simple closed-loop control, the LLC resonant converter will experience large output ripple under no-load or light-load conditions, or during intermittent drive, and will generate howling when the intermittent drive frequency is within the audio range. When switching between no-load and full-load output states, the large change in operating frequency will cause excessive load dynamic overshoot. That is, the control logic of the LLC resonant converter under different output load conditions is as follows: when the output load is light, the required gain is low, and the operating frequency needs to be adjusted to be higher; when the output load is heavy, the required gain is high, and the operating frequency needs to be adjusted to be lower. Secondly, the control logic corresponding to the output voltage adjustment direction is as follows: when the output voltage is increased, the gain decreases, and the operating frequency needs to be adjusted to be lower; when the output voltage is decreased, the gain increases, and the operating frequency needs to be adjusted to be higher. Therefore, by connecting the output current sampling module 110, the output voltage feedback module 120, and the power controller 130 in sequence, the operating frequency of the LLC resonant converter can be adjusted to achieve the above control logic, thereby avoiding intermittent drive and excessive load dynamic overshoot.

[0045] In this embodiment of the invention, the output current sampling module 110 can be connected to the output terminal of the LLC resonant converter via a branch to collect the current signal output by the LLC resonant converter. Then, the operational amplifier circuit set in the output current sampling module 110 amplifies the current signal linearly, which facilitates the subsequent analysis and comparison of the amplified current signal, thereby obtaining the current working state of the LLC resonant converter.

[0046] The output voltage feedback module 120 is used to convert the amplified current signal into a voltage signal, compare the voltage signal with a reference voltage, increase the output feedback voltage when the voltage signal is lower than the reference voltage, and decrease the output feedback voltage when the voltage signal is higher than the reference voltage.

[0047] In this embodiment of the invention, the output voltage feedback module 120 is provided with a voltage comparison circuit. After receiving the amplified current signal, the corresponding voltage signal can be collected through a resistor and then compared with the input reference voltage. The magnitude of the reference voltage is set by the user. Usually, the reference voltage is set higher than the conventional design value to ensure that high-frequency interruptions are avoided under no-load conditions, and the feedback voltage is reduced accordingly as the output load increases.

[0048] The power controller 130 is used to receive the feedback voltage and adjust the operating frequency of the LLC resonant converter according to the feedback voltage.

[0049] In this embodiment of the invention, the power controller 130 increases the operating frequency of the LLC resonant converter when the received feedback voltage increases, and decreases the operating frequency of the LLC resonant converter when the received feedback voltage decreases. That is, when the LLC resonant converter is under light load or no load, the power controller 130 increases the operating frequency of the LLC resonant converter to avoid intermittent driving; when the LLC resonant converter transitions from no load to heavy load, the power controller 130 decreases the operating frequency of the LLC resonant converter to reduce the dynamic overshoot swing of the LLC resonant converter.

[0050] Example 2

[0051] Figure 2 This is a schematic diagram of the structure of an LLC resonant converter control circuit provided in Embodiment 2 of the present invention.

[0052] The LLC resonant converter control circuit 200 includes an output current sampling module 210, an output voltage feedback module 220, and a power controller 230 connected in sequence.

[0053] The output current sampling module 210 is used to collect the current signal output by the LLC resonant converter, and amplify the current signal according to a preset ratio before inputting it to the output voltage feedback module 220.

[0054] The output voltage feedback module 220 is used to convert the amplified current signal into a voltage signal, compare the voltage signal with a reference voltage, increase the output feedback voltage when the voltage signal is lower than the reference voltage, and decrease the output feedback voltage when the voltage signal is higher than the reference voltage.

[0055] The power controller 230 is used to receive the feedback voltage and adjust the operating frequency of the LLC resonant converter according to the feedback voltage.

[0056] The output current sampling module 210 includes a differential operational amplifier circuit 211.

[0057] The output voltage feedback module 220 includes a voltage divider circuit 221 and a voltage comparator circuit 222 connected in sequence.

[0058] The voltage divider circuit 221 is used to receive the current signal, convert the current signal into a voltage signal, and perform voltage division.

[0059] The voltage comparison circuit 222 is used to receive the voltage signal after voltage division, compare the voltage signal with a reference voltage, increase the output feedback voltage when the voltage signal is lower than the reference voltage, and decrease the output feedback voltage when the voltage signal is higher than the reference voltage.

[0060] In this embodiment of the invention, the voltage comparison circuit 222 includes an operational amplifier circuit and a TL431 circuit (TL431, a controllable precision voltage regulator).

[0061] Example 3

[0062] Figure 3 This is a schematic diagram of the structure of an LLC resonant converter control circuit provided in Embodiment 3 of the present invention.

[0063] The LLC resonant converter control circuit 300 includes a differential operational amplifier circuit 310, a voltage divider circuit 320, a voltage comparator circuit 330, and a power controller 340 connected in sequence.

[0064] The differential operational amplifier circuit 310 is used to acquire the current signal output by the LLC resonant converter and amplify the current signal according to a preset ratio.

[0065] The voltage divider circuit 320 is used to receive the amplified current signal, convert the current signal into a voltage signal, and perform voltage division.

[0066] The voltage comparison circuit 330 is used to receive the voltage signal after voltage division, compare the voltage signal with a reference voltage, increase the output feedback voltage when the voltage signal is lower than the reference voltage, and decrease the output feedback voltage when the voltage signal is higher than the reference voltage.

[0067] When the received feedback voltage increases, the power controller 340 increases the operating frequency of the LLC resonant converter; when the received feedback voltage decreases, the power controller 340 decreases the operating frequency of the LLC resonant converter.

[0068] The differential operational amplifier circuit 310 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a differential operational amplifier U1, and a first capacitor C1.

[0069] The negative input pin INA- of the differential operational amplifier U1 is connected to the first resistor R1, and the positive input pin INA+ is connected to the second resistor R2. The current signal output by the LLC resonant converter is acquired through the first resistor R1 and the second resistor R2.

[0070] One end of the third resistor R3 is connected to the positive input pin INA+ of the differential operational amplifier U1, and the other end is grounded.

[0071] One end of the fourth resistor R4 is connected to the negative input pin INA- of the differential operational amplifier U1, and the other end is connected to the output pin OUT_A of the differential operational amplifier U1.

[0072] One end of the first capacitor C1 is connected to the drive power supply pin V+ of the differential operational amplifier U1, and the other end is grounded.

[0073] The voltage divider circuit 320 includes a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7;

[0074] One end of the fifth resistor R5 is used to connect to the negative input terminal INA-, and the other end is used to receive the amplified current signal;

[0075] One end of the sixth resistor R6 is used to connect to the negative input terminal INA-, and the other end is used to connect to the voltage output terminal VOUT; wherein, the voltage output terminal VOUT outputs voltage to the power supply system of the LLC resonant converter to provide voltage feedback to the power supply system.

[0076] One end of the seventh resistor R7 is used to connect to the negative input terminal INA-, and the other end is used to ground.

[0077] The voltage comparison circuit 330 includes a voltage comparator and a second capacitor;

[0078] The positive input terminal INA+ of the voltage comparator is used to receive the reference voltage VREF, the negative input terminal INA- is used to receive the voltage signal, and the output pin is used to connect to the power controller 340.

[0079] One end of the second capacitor C2 is connected to the drive power supply pin V+ of the voltage comparator, and the other end is grounded.

[0080] In this embodiment of the invention, the LLC resonant converter control circuit can effectively solve the problem of large output ripple during intermittent drive operation of the LLC resonant converter under no-load or light-load conditions, and improve the problem of large output dynamic overshoot when the LLC resonant converter switches between no-load and full-load states.

[0081] The present invention also provides an LLC resonant converter circuit, including an LLC resonant converter and the aforementioned LLC resonant converter control circuit connected to the LLC resonant converter. The LLC resonant converter includes a full-bridge LLC resonant converter and a half-bridge LLC resonant converter.

[0082] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An LLC resonant converter control circuit, characterized by, It includes an output current sampling module, an output voltage feedback module, and a power controller connected in sequence; The output current sampling module is used to collect the current signal output by the LLC resonant converter, and amplify the current signal according to a preset ratio before inputting it to the output voltage feedback module; The output voltage feedback module is used to convert the amplified current signal into a voltage signal, compare the voltage signal with a reference voltage, increase the output feedback voltage when the voltage signal is lower than the reference voltage, and decrease the output feedback voltage when the voltage signal is higher than the reference voltage, wherein the reference voltage is higher than a normal value; The power controller is used to receive the feedback voltage and adjust the operating frequency of the LLC resonant converter according to the feedback voltage; When the received feedback voltage increases, the power controller increases the operating frequency of the LLC resonant converter; when the received feedback voltage decreases, the power controller decreases the operating frequency of the LLC resonant converter. The output voltage feedback module includes a voltage divider circuit and a voltage comparison circuit connected in sequence; The voltage divider circuit is used to receive the current signal, convert the current signal into a voltage signal, and perform voltage division. The voltage comparison circuit is used to receive the voltage signal after voltage division, compare the voltage signal with a reference voltage, increase the output feedback voltage when the voltage signal is lower than the reference voltage, and decrease the output feedback voltage when the voltage signal is higher than the reference voltage.

2. The LLC resonant converter control circuit of claim 1, wherein, The output current sampling module includes a differential operational amplifier circuit.

3. The LLC resonant converter control circuit of claim 2, wherein, The differential operational amplifier circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a differential operational amplifier, and a first capacitor; The negative input pin of the differential operational amplifier is connected to the first resistor, and the positive input pin is connected to the second resistor. The current signal output by the LLC resonant converter is acquired through the first resistor and the second resistor. One end of the third resistor is connected to the positive input pin of the differential operational amplifier, and the other end is grounded; One end of the fourth resistor is connected to the negative input pin of the differential operational amplifier, and the other end is connected to the output pin of the differential operational amplifier. One end of the first capacitor is connected to the drive power supply pin of the differential operational amplifier, and the other end is grounded.

4. The LLC resonant converter control circuit of claim 1, wherein, The voltage comparison circuit includes a voltage comparator and a second capacitor; The positive input terminal of the voltage comparator is used to receive the reference voltage, the negative input terminal is used to receive the voltage signal, and the output pin is used to connect to the power controller. One end of the second capacitor is connected to the drive power supply pin of the voltage comparator, and the other end is grounded.

5. The LLC resonant converter control circuit of claim 4, wherein, The voltage divider circuit includes a fifth resistor, a sixth resistor, and a seventh resistor; One end of the fifth resistor is used to connect to the negative input terminal, and the other end is used to receive the amplified current signal; One end of the sixth resistor is used to connect to the negative input terminal, and the other end is used to connect to the voltage output terminal; One end of the seventh resistor is used to connect to the negative input terminal, and the other end is used to ground.

6. The LLC resonant converter control circuit of claim 1, wherein, The voltage comparator circuit includes a TL431.

7. An LLC resonant conversion circuit, characterized by, The LLC resonant converter comprises a full-bridge LLC resonant converter and a half-bridge LLC resonant converter.

8. The LLC resonant conversion circuit of claim 7, wherein, The LLC resonant converter comprises a full-bridge LLC resonant converter and a half-bridge LLC resonant converter.

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