A wide-voltage output circuit and power supply system suitable for LLC resonant circuits

Abstract

This invention relates to a wide output voltage circuit and power supply system suitable for LLC resonant circuits. The circuit, applied to a power supply system, includes a buck power factor correction (Buck PFC) circuit and an LLC half-bridge resonant circuit. The LLC half-bridge resonant circuit includes an LLC control circuit, a transformer with at least three windings, a voltage integration and regulation circuit, a reference voltage generation circuit, an operational amplifier voltage output circuit, and a feedback circuit. The three windings include a main winding, an output winding, and an auxiliary winding. The auxiliary winding monitors changes in the output voltage. When a change occurs, the induced voltage in the auxiliary winding changes accordingly and is converted into a DC voltage by the voltage integration and regulation circuit. This voltage is then provided to the Buck PFC circuit via the operational amplifier voltage output circuit and the feedback circuit, causing the output voltage of the Buck PFC circuit to change synchronously and linearly with the output voltage. This synchronizes the resonant frequency of the LLC resonant circuit with the switching frequency of the power supply system, thereby improving the efficiency of the power supply system.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and more particularly to a wide voltage output circuit and power supply system suitable for LLC resonance. Background Technology

[0002] As people become increasingly reliant on mobile phones, and with the widespread use of power-intensive features such as high refresh rates and 2K screens, battery life has become a common problem. To improve user experience, reduce charging time, and increase charging speed, fast charging technology has rapidly emerged, representing an inevitable trend in the mobile phone industry to meet the needs of modern fast-paced lifestyles. Fast charging technology adjusts the output voltage through protocol communication to adapt to different load requirements, switching between multiple voltage levels such as 5V, 9V, 15V, and 20V. Therefore, charging devices with a wide range of output voltages are becoming increasingly common.

[0003] Half-bridge resonant (LLC) circuits are widely used in fast charging power supplies because their primary-side power switches achieve zero-voltage turn-on (ZVS) and secondary-side power switches achieve zero-current turn-off (ZCS), resulting in high efficiency and higher switching frequencies. Typically, this circuit employs a two-stage structure, first using a boost power factor correction (PFC) circuit, such as... Figure 1 As shown, however, due to the characteristics of the Boost PFC topology, its output voltage must be higher than the input voltage. Considering that the general input voltage range varies from 85Vac to 265Vac, the output voltage of the Boost PFC is typically set at 400Vdc.

[0004] LLC circuits achieve maximum efficiency by adjusting the switching frequency to vary the output voltage, typically reaching peak efficiency when the switching frequency equals the resonant frequency. However, when the output voltage varies significantly (e.g., from 20V to 5V), the switching frequency adjustment range is large. If the switching frequency deviates too far from the resonant frequency, the power supply system's efficiency drops drastically, potentially damaging the system. Therefore, the combination of a Boost PFC front-end and an LLC resonant circuit back-end in a traditional two-stage architecture is unsuitable for power supplies with a wide output voltage range. Summary of the Invention

[0005] The purpose of this invention is to provide a wide voltage output circuit suitable for LLC resonant circuits, which can be applied to power supply systems with a wide range of output voltages.

[0006] Therefore, in a first aspect, embodiments of the present invention provide a wide output voltage circuit suitable for LLC resonance, applied to a power supply system, the wide output voltage circuit comprising: a buck power factor correction (Buck PFC) circuit and an LLC half-bridge resonant circuit;

[0007] The LLC half-bridge resonant circuit includes: an LLC control circuit, a transformer with at least three windings, a voltage integration and regulation circuit, a reference voltage generation circuit, an operational amplifier voltage output circuit, and a feedback circuit; wherein, the three windings include a main winding, an output winding, and an auxiliary winding;

[0008] The output terminal of the Buck PFC circuit is connected to the input terminal of the LLC control circuit, and the output terminal of the LLC control circuit is connected to the main winding; the output winding is connected to the output voltage node, and the output voltage is output through the output voltage node; the auxiliary winding is connected to the input terminal of the voltage integration and regulation circuit.

[0009] The reference voltage generation circuit is connected to the first input terminal of the operational amplifier voltage output circuit to provide a reference voltage Vref; the output terminal of the voltage integration and regulation circuit is connected to the second input terminal of the operational amplifier voltage output circuit; the output terminal of the operational amplifier voltage output circuit is connected to the input terminal of the feedback circuit, and the output terminal of the feedback circuit is connected to the voltage sampling terminal of the Buck PFC circuit.

[0010] The auxiliary winding monitors changes in the output voltage. When a change occurs, the induced voltage of the auxiliary winding changes accordingly. This change is then converted into a DC voltage by a voltage integration and regulation circuit. The DC voltage is then fed to the Buck PFC circuit via the operational amplifier voltage output circuit and the feedback circuit. This allows the output voltage of the Buck PFC circuit to change synchronously and linearly with the output voltage. Consequently, the resonant frequency of the LLC resonant circuit is synchronized with the switching frequency of the power supply system, thereby improving the efficiency of the power supply system.

[0011] Preferably, during normal operation, the output voltage of the buck power factor correction (BFC) circuit is 100V DC, suitable for power supply systems with an input voltage range of 85V AC to 265V AC.

[0012] Preferably, the voltage integration and regulation circuit includes: resistor R4, diode D5, capacitor C1 and a first voltage divider circuit;

[0013] One end of resistor R4 is connected to the same-name terminal of the auxiliary winding, and the other end is connected to the input terminal of diode D5. The output terminal of diode D5 is connected to one end of capacitor C1 and then to the first voltage divider circuit. The first voltage divider circuit includes voltage divider resistors R8 and R10. The first voltage divider circuit and capacitor C1 are connected in parallel to ground.

[0014] The induced voltage of the auxiliary winding is integrated through resistor R4, diode D5 and capacitor C1 to generate a DC voltage on capacitor C1. The voltage on capacitor C1 is divided by resistors R8 and R10 and then sent to the second input terminal of the operational amplifier voltage output circuit.

[0015] Preferably, the reference voltage generation circuit includes a controllable precision voltage regulator.

[0016] More preferably, the reference voltage Vref is a 2.5V reference voltage.

[0017] Preferably, the operational amplifier voltage output circuit includes an operational amplifier;

[0018] The first input terminal is the positive input terminal of the operational amplifier; the second input terminal is the inverting input terminal of the operational amplifier.

[0019] The output terminal of the voltage integration and regulation circuit is connected in series with resistor R9 and then connected to the second input terminal of the operational amplifier voltage output circuit.

[0020] The second input terminal of the operational amplifier voltage output circuit is connected in series with resistor R11 and then connected to the output terminal of the operational amplifier voltage output circuit.

[0021] More preferably, the output voltage Vop of the operational amplifier voltage output circuit is determined by the following formula:

[0022] Vop = R11 × (Vref - V1) / R9;

[0023] Wherein, V1 is the output voltage of the voltage integration and regulation circuit;

[0024] When the output voltage decreases, V1 decreases, causing Vop to increase; when the output voltage increases, V1 increases, causing Vop to decrease.

[0025] Preferably, the feedback circuit includes diode D4;

[0026] The output voltage of the operational amplifier voltage output circuit is fed into the second voltage divider circuit of the Buck PFC circuit through the diode D4. After being divided by the second voltage divider circuit, the divided voltage is sent to the voltage sampling terminal of the PFC controller of the Buck PFC circuit.

[0027] More preferably, the second voltage divider circuit includes series resistors R1, R2, and R3;

[0028] The second voltage divider circuit is connected in series between the output of the Buck PFC circuit and ground;

[0029] The input node between resistors R1 and R2 is the output terminal of the feedback circuit; the output node between series resistors R2 and R3 is the output terminal of the second voltage divider circuit.

[0030] Secondly, embodiments of the present invention provide a power supply system including the wide output voltage circuit suitable for LLC resonance described in the first aspect above.

[0031] The wide output voltage circuit suitable for LLC resonance provided in this invention has the following main technical advantages:

[0032] 1. High-efficiency power conversion: By combining a buck power factor correction (Buck PFC) circuit and an LLC half-bridge resonant circuit, the power supply system achieves high-efficiency power conversion. The Buck PFC circuit improves the power factor and reduces reactive power loss, while the LLC resonant circuit operates in a resonant state, reducing switching losses, thereby improving the efficiency of the entire system.

[0033] 2. Wide input voltage adaptability: This circuit makes the power supply system suitable for a wide range of input voltages, from 85VAC to 265V AC. This increases the adaptability of the power supply system, enabling it to cope with grid voltage fluctuations in different regions and applications.

[0034] 3. Voltage Stability: Through the combined action of the LLC control circuit, voltage integration and regulation circuit, reference voltage generation circuit, and operational amplifier voltage output circuit, precise voltage control and stability are achieved. This helps ensure that the output voltage remains at the required level to meet load demands.

[0035] 4. Synchronous Resonant Frequency: By monitoring output voltage changes through the auxiliary winding, the induced voltage is converted into a DC voltage and provided to the Buck PFC circuit via the operational amplifier voltage output circuit and feedback circuit. This allows the output voltage of the Buck PFC circuit to change synchronously and linearly with the output voltage. This helps maintain the resonant frequency of the LLC resonant circuit close to the switching frequency of the power supply system, improving the efficiency of the entire power supply system.

[0036] The circuit of this invention features high-efficiency power conversion, wide input voltage adaptability, voltage stability, and synchronous resonant frequency. It can be used to realize a high-performance power supply system, which helps to reduce power waste, improve the efficiency of the power supply system, and maintain voltage stability, making it suitable for various application fields. Attached Figure Description

[0037] Figure 1 A circuit diagram of a boost power factor correction (PFC) circuit is provided for the prior art;

[0038] Figure 2 This is a circuit diagram for a buck power factor correction (Buck PFC) circuit.

[0039] Figure 3 This invention provides a wide voltage output circuit diagram suitable for LLC resonance. Detailed Implementation

[0040] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0041] To address the issue that the combination of a Boost PFC front-end and an LLC resonant circuit back-end is not suitable for power supply systems with a wide range of output voltages, such as... Figure 2 The buck power factor correction (BFC) circuit shown has different output voltage requirements than Boost PFC; its output voltage must be lower than the minimum input voltage. Taking an input voltage range of 90Vac to 264Vac as an example, the minimum voltage requirement is 127Vdc. Therefore, the output voltage of the Buck PFC can be set at 127Vdc. Through a scientifically designed circuit, this invention allows the Buck PFC to be combined with an LLC resonant circuit, enabling stable operation over a wide range of output voltage conditions.

[0042] This invention provides a wide output voltage circuit suitable for LLC resonant circuits, applied to power supply systems. The circuit structure is as follows: Figure 3 As shown, it includes: a buck power factor correction (BFC) circuit and an LLC half-bridge resonant circuit;

[0043] Buck PFC circuit, such as Figure 3 As shown, it includes a bridge rectifier circuit BD1, a PFC controller U2, a power MOSFET Q1, a diode D1, a capacitor EC1, an inductor L1, and a second voltage divider circuit. Under normal operation, the output voltage of the buck PFC circuit is approximately 100V DC, which is suitable for power supply systems with an input voltage range of 85V AC to 265V AC.

[0044] The LLC half-bridge resonant circuit includes: an LLC control circuit, a transformer T1 with at least three windings, a voltage integration and regulation circuit, a reference voltage generation circuit, an operational amplifier voltage output circuit, and a feedback circuit.

[0045] The LLC control circuit includes an LLC controller U1, power MOSFETs Q2 and Q3, a series capacitor Lr, and an inductor Cr. Power MOSFETs Q2 and Q3 are connected to the high-side (Vgh) and low-side (Vgl) terminals of the LLC controller U1, respectively. The high-side switching power MOSFET Q2 controls the power output and works in conjunction with the inductor Cr and capacitor Lr in the resonant circuit. The low-side switching power MOSFET Q3 works in conjunction with the high-side switching to achieve efficient power conversion. The control and coordination of the two signals on the high and low sides is a crucial part of the LLC resonant circuit, ensuring effective power conversion and minimizing losses.

[0046] The transformer T1 has three windings: the main winding Np, the output winding Ns, and the auxiliary winding Na.

[0047] The voltage integration and regulation circuit includes: resistor R4, diode D5, capacitor C1, and a first voltage divider circuit; one end of resistor R4 is connected to the same-name terminal of the auxiliary winding Na, and the other end is connected to the input terminal of diode D5. The output terminal of diode D5 is connected to one end of capacitor C1 and connected to the first voltage divider circuit; the first voltage divider circuit includes voltage dividing resistors R8 and R10; the first voltage divider circuit is connected to ground in parallel with capacitor C1; the induced voltage of the auxiliary winding Na is integrated through resistor R4, diode D5, and capacitor C1, thereby generating a DC voltage on capacitor C1. The voltage on capacitor C1 is divided by resistors R8 and R10 and then sent to the second input terminal of the operational amplifier voltage output circuit.

[0048] The reference voltage generation circuit includes a controllable precision voltage regulator Q4. In this specific application of the invention, Q4 uses a TL431 controllable precision voltage regulator, and the reference voltage generation circuit is implemented with two resistors R5 and R6, providing a reference voltage of Vref = 2.5V, which is fed into the first input terminal of the operational amplifier voltage output circuit.

[0049] The operational amplifier voltage output circuit includes an operational amplifier U3; the first input terminal is the positive input terminal of the operational amplifier U3; the second input terminal is the inverting input terminal of the operational amplifier U3; the output terminal of the voltage integration and regulation circuit is connected to the second input terminal of the operational amplifier voltage output circuit via a series resistor R9; the second input terminal of the operational amplifier voltage output circuit is connected to the output terminal of the operational amplifier voltage output circuit via a series resistor R11.

[0050] The output voltage Vop of the op-amp voltage output circuit is determined by the following formula:

[0051] Vop = R11 × (Vref - V1) / R9;

[0052] Wherein, V1 is the output voltage of the voltage integration and regulation circuit; when the output voltage decreases, V1 decreases, causing Vop to increase; when the output voltage increases, V1 increases, causing Vop to decrease.

[0053] The feedback circuit includes diode D4. The output voltage of the operational amplifier voltage output circuit is fed into the second voltage divider circuit of the Buck PFC circuit through diode D4. After being divided by the second voltage divider circuit, the divided voltage is sent to the voltage sampling terminal of the PFC controller of the Buck PFC circuit. The second voltage divider circuit includes series resistors R1, R2, and R3. The second voltage divider circuit is connected in series between the output terminal of the Buck PFC circuit and ground. The input node between resistors R1 and R2 is the output terminal of the feedback circuit; the output node between series resistors R2 and R3 is the output terminal of the second voltage divider circuit.

[0054] Therefore, in the wide output voltage circuit of the present invention, the output terminal of the Buck PFC circuit is connected to the input terminal of the LLC control circuit, and the output terminal of the LLC control circuit is connected to the main winding Np; the output winding Ns is connected to the output voltage node, and the output voltage Vout is output through the output voltage node; the auxiliary winding Na is connected to the input terminal of the voltage integration and voltage regulation circuit.

[0055] The reference voltage generation circuit is connected to the first input terminal of the op-amp voltage output circuit to provide the reference voltage Vref; the output terminal of the voltage integration and regulation circuit is connected to the second input terminal of the op-amp voltage output circuit; the output terminal of the op-amp voltage output circuit is connected to the input terminal of the feedback circuit, and the output terminal of the feedback circuit is connected to the voltage sampling terminal of the Buck PFC circuit.

[0056] The auxiliary winding Na monitors the change in output voltage Vout. When the output voltage Vout changes, the induced voltage in the auxiliary winding Na changes accordingly. This change is then converted into a DC voltage through a voltage integration and regulation circuit. The voltage is then fed to the Buck PFC circuit via the operational amplifier voltage output circuit and feedback circuit. This allows the output voltage of the Buck PFC circuit to change synchronously and linearly with the output voltage Vout. Consequently, the resonant frequency of the LLC resonant circuit is synchronized with the switching frequency of the power supply system, thereby improving the efficiency of the power supply system.

[0057] For example, when the output voltage decreases, the voltage across capacitor C1 also decreases, as does the voltage across voltage divider resistor R10. After passing through operational amplifier U3, the voltage increases, thus increasing the voltage sampled by the Buck PFC controller, and decreasing the Vout_PFC voltage. Through this adjustment, changes in Vout will also cause a linear change in Vout_PFC, maintaining the resonant frequency of the LLC resonant circuit in the second stage near the switching frequency. Conversely, the opposite is also true.

[0058] This invention monitors output voltage changes via an auxiliary winding, converts the induced voltage into a DC voltage, and provides it to the Buck PFC circuit for voltage sampling through an operational amplifier voltage output circuit and a feedback circuit. This enables the Buck PFC circuit's output voltage to change synchronously and linearly with the output voltage. This helps maintain the LLC resonant circuit's resonant frequency close to the power supply system's switching frequency, improving the overall power supply system efficiency.

[0059] The circuit of this invention features high-efficiency power conversion, wide input voltage adaptability, voltage stability, and synchronous resonant frequency. It can be used to realize a high-performance power supply system, which helps to reduce power waste, improve the efficiency of the power supply system, and maintain voltage stability, making it suitable for various application fields.

[0060] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wide output voltage circuit suitable for LLC resonant circuits, applied in power supply systems, characterized in that, The wide output voltage circuit includes: a buck power factor correction (BFC) circuit and an LLC half-bridge resonant circuit; The LLC half-bridge resonant circuit includes: an LLC control circuit, a transformer with at least three windings, a voltage integration and regulation circuit, a reference voltage generation circuit, an operational amplifier voltage output circuit, and a feedback circuit; wherein, the three windings include a main winding, an output winding, and an auxiliary winding; The output terminal of the Buck PFC circuit is connected to the input terminal of the LLC control circuit, and the output terminal of the LLC control circuit is connected to the main winding; the output winding is connected to the output voltage node, and the output voltage is output through the output voltage node; the auxiliary winding is connected to the input terminal of the voltage integration and regulation circuit. The reference voltage generation circuit is connected to the first input terminal of the operational amplifier voltage output circuit to provide a reference voltage Vref; the output terminal of the voltage integration and regulation circuit is connected to the second input terminal of the operational amplifier voltage output circuit; the output terminal of the operational amplifier voltage output circuit is connected to the input terminal of the feedback circuit, and the output terminal of the feedback circuit is connected to the voltage sampling terminal of the Buck PFC circuit. The auxiliary winding monitors changes in the output voltage. When a change occurs, the induced voltage of the auxiliary winding changes accordingly. This change is then converted into a DC voltage by a voltage integration and regulation circuit. The voltage is then fed to the Buck PFC circuit via the operational amplifier voltage output circuit and the feedback circuit. This allows the output voltage of the Buck PFC circuit to change synchronously and linearly with the output voltage. Consequently, the resonant frequency of the LLC half-bridge resonant circuit is synchronized with the switching frequency of the power supply system, thereby improving the efficiency of the power supply system.

2. The wide output voltage circuit according to claim 1, characterized in that, During normal operation, the output voltage of the buck power factor correction (BFC) circuit is 100V DC, which is suitable for power supply systems with an input voltage range of 85V AC to 265V AC.

3. The wide output voltage circuit according to claim 1, characterized in that, The voltage integration and regulation circuit includes: resistor R4, diode D5, capacitor C1, and a first voltage divider circuit; One end of resistor R4 is connected to the same-name terminal of the auxiliary winding, and the other end is connected to the input terminal of diode D5. The output terminal of diode D5 is connected to one end of capacitor C1 and then to the first voltage divider circuit. The first voltage divider circuit includes voltage divider resistors R8 and R10. The first voltage divider circuit and capacitor C1 are connected in parallel to ground. The induced voltage of the auxiliary winding is integrated through resistor R4, diode D5 and capacitor C1 to generate a DC voltage on capacitor C1. The voltage on capacitor C1 is divided by resistors R8 and R10 and then sent to the second input terminal of the operational amplifier voltage output circuit.

4. The wide output voltage circuit according to claim 1, characterized in that, The reference voltage generation circuit includes a controllable precision voltage regulator.

5. The wide output voltage circuit according to claim 4, characterized in that, The reference voltage Vref is a 2.5V reference voltage.

6. The wide output voltage circuit according to claim 1, characterized in that, The operational amplifier voltage output circuit includes an operational amplifier; The first input terminal is the non-inverting input terminal of the operational amplifier; the second input terminal is the inverting input terminal of the operational amplifier. The output terminal of the voltage integration and regulation circuit is connected in series with resistor R9 and then connected to the second input terminal of the operational amplifier voltage output circuit. The second input terminal of the operational amplifier voltage output circuit is connected in series with resistor R11 and then connected to the output terminal of the operational amplifier voltage output circuit.

7. The wide output voltage circuit according to claim 6, characterized in that, The output voltage Vop of the operational amplifier voltage output circuit is determined by the following formula: Vop = R11 × (Vref - V1) / R9; Wherein, V1 is the output voltage of the voltage integration and regulation circuit; When the output voltage decreases, V1 decreases, causing Vop to increase; when the output voltage increases, V1 increases, causing Vop to decrease.

8. The wide output voltage circuit according to claim 1, characterized in that, The feedback circuit includes diode D4; The output voltage of the operational amplifier voltage output circuit is fed into the second voltage divider circuit of the Buck PFC circuit through the diode D4. After being divided by the second voltage divider circuit, the divided voltage is sent to the voltage sampling terminal of the PFC controller of the Buck PFC circuit.

9. The wide output voltage circuit according to claim 8, characterized in that, The second voltage divider circuit includes series resistors R1, R2, and R3; The second voltage divider circuit is connected in series between the output of the Buck PFC circuit and ground; The input node between resistors R1 and R2 is the output terminal of the feedback circuit; the output node between series resistors R2 and R3 is the output terminal of the second voltage divider circuit.

10. A power supply system, characterized in that, The power supply system includes the wide output voltage circuit suitable for LLC resonance as described in any one of claims 1-9.

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