A voltage holding circuit

Abstract

This utility model discloses a voltage holding circuit, including: a rectifier bridge unit, a PFC unit, and an LLC unit; the PFC unit includes: a boost module, capacitor C1, capacitor C3, a first switch Q4, a second switch Q5, and a control module; the output terminal of the rectifier bridge unit is connected to the input terminal of the boost module and the first terminal of the second switch Q5; the second terminal of the second switch Q5 is connected to the first terminal of capacitor C3 and the first terminal of the first switch Q4; the second terminal of capacitor C3 is connected to the first terminal of capacitor C1; the second terminal of the first switch Q4 is connected to the second terminal of capacitor C1, the output terminal of the boost module, and the input terminal of the LLC unit; the control module is connected to the first switch Q4 and the second switch Q5. This voltage holding circuit has the advantages of high component utilization and low power loss. While extending the power-down hold time, it can also improve power efficiency and has good application prospects.

Description

Technical Field

[0001] This utility model relates to the field of power supply design technology, and in particular to a voltage holding circuit. Background Technology

[0002] In a typical server power supply design, the AC input power is rectified by a rectifier bridge into a full-wave DC sine wave. This wave is then boosted by a boost circuit to charge the energy storage capacitor C1. Capacitor C1 is a high-voltage, high-capacitance energy storage capacitor. When the power input voltage drops, capacitor C1 discharges to maintain a stable power output voltage. During normal operation, the B+ voltage output by the boost circuit is typically around 400V. The subsequent LLC circuit converts the B+ voltage to the required output voltage, such as 12V.

[0003] However, the LLC circuit has a narrow operating range. When the B+ voltage drops below 340V, the output voltage cannot remain stable. When the power input voltage drops, the boost circuit stops working, but the LLC circuit continues to operate for a period of time, transferring the energy stored in capacitor C1 to the secondary side. When the voltage of capacitor C1 drops from 400V to 340V, the DSP chip inside the power supply detects that the B+ voltage is too low and shuts down the LLC circuit, causing the output voltage to drop.

[0004] A current technique for improving the power-down protection time involves adding a secondary boost circuit (comprised of a switch, inductor, diode, and capacitor) after the PFC circuit and before the LLC circuit. This circuit activates after a power input failure, boosting the voltage across capacitor C1 before inputting it to the LLC circuit to extend the power-down protection time. However, this approach has significant drawbacks: firstly, the components in the secondary boost circuit have low utilization, only activating after a power input voltage failure and failing during normal operation; secondly, the added inductor and diode in the LLC's input current path result in substantial power loss and reduced power efficiency. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of low component utilization and high power loss in existing voltage holding circuits, and to provide a voltage holding circuit.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This utility model embodiment provides a voltage holding circuit, including: a rectifier bridge unit, a PFC unit, and an LLC unit; The PFC unit includes: a boost module, capacitor C1, capacitor C3, a first switch Q4, a second switch Q5, and a control module; The output terminal of the rectifier bridge unit is connected to the input terminal of the boost module and the first terminal of the second switch Q5; the second terminal of the second switch Q5 is connected to the first terminal of the capacitor C3 and the first terminal of the first switch Q4; the second terminal of the capacitor C3 is connected to the first terminal of the capacitor C1; the second terminal of the first switch Q4 is connected to the second terminal of the capacitor C1, the output terminal of the boost module, and the input terminal of the LLC unit; the control module is connected to the first switch Q4 and the second switch Q5.

[0007] In one embodiment, the control module includes a control chip, which has a first output pin and a second output pin; the first output pin is connected to the first switch Q4; and the second output pin is connected to the second switch Q5.

[0008] In one embodiment, the control module further includes a power supply VCC1, resistors R1 and R2, and an optocoupler IC1; the first end of resistor R1 is connected to the second output pin, and the second end is connected to pin 1 of the optocoupler IC1; pin 3 of the optocoupler IC1 is connected to the second switch Q5 and the first end of resistor R2; the second end of resistor R2 is connected to the output terminal of the rectifier bridge unit; and the power supply VCC1 is connected to pin 4 of the optocoupler IC1.

[0009] In one embodiment, the control module further includes a power supply VCC2, resistors R3 and R4, and an optocoupler IC2; the first end of resistor R3 is connected to the first output pin, and the second end is connected to pin 1 of the optocoupler IC2; pin 3 of the optocoupler IC2 is connected to the first switch Q4 and the first end of resistor R4; the second end of resistor R4 is connected to the first end of capacitor C3; and the power supply VCC2 is connected to pin 4 of the optocoupler IC2.

[0010] In one embodiment, the capacitance of capacitor C3 is greater than the capacitance of capacitor C1.

[0011] In one embodiment, the boost module includes an inductor L1, a diode D2, and a third switch Q3; the first end of the inductor L1 is connected to the output end of the rectifier bridge unit, and the second end is connected to the first end of the diode D2; the second end of the diode D2 is connected to the input end of the LLC unit; the first end of the third switch Q3 is connected to the second end of the capacitor C3, and the second end is connected to the second end of the inductor L1 and the first end of the diode D2.

[0012] In one embodiment, the control chip has a PWM output pin, and the third switch Q3 is connected to the PWM output pin.

[0013] In one embodiment, the first switch Q4, the second switch Q5, and the third switch Q3 are MOSFETs or IGBTs; the control chip is connected to the gate of the MOSFET or the gate of the IGBT; the first terminal of the first switch Q4, the first terminal of the second switch Q5, and the first terminal of the third switch Q3 are the source of the MOSFET or the emitter of the IGBT; the second terminal of the first switch Q4, the second terminal of the second switch Q5, and the second terminal of the third switch Q3 are the drain of the MOSFET or the collector of the IGBT.

[0014] In one embodiment, the first switch Q4 and the second switch Q5 are surface mount components.

[0015] In one embodiment, the control chip is model DSPIC33FJ64GS606.

[0016] The voltage holding circuit of this invention has the following advantages compared with the prior art: By adding a first switch Q4, a second switch Q5, and a capacitor C3 to the PFC unit, and controlling the first switch Q4 and the second switch Q5 through the control module to dynamically switch the charging and discharging path of capacitor C3, when the power supply is working normally, capacitor C3 and capacitor C1 are connected in parallel and together serve as the output capacitor of the PFC unit, supplying power to the LLC unit; when the power supply is off, capacitor C3 switches to the input capacitor of the PFC unit, the boost module continues to work, boosts the voltage of capacitor C3 and sends it to capacitor C1, and then supplies power to the LLC unit, thereby extending the working time of the LLC unit. The circuit has high component utilization and low power loss. While extending the power outage holding time, it can also improve power efficiency and has good application prospects.

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the voltage holding circuit provided by this utility model; Figure 2 A schematic diagram of the voltage holding circuit provided by this utility model when the input voltage is in a normal state; Figure 3A schematic diagram of the voltage holding circuit provided by this utility model when the input voltage is in a power-off state; Figure 4 A schematic diagram of the control module provided by this utility model.

[0020] Figure Labels 1. Rectifier bridge unit; 2. PFC unit; 21. Boost module; 3. LLC unit. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0023] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0025] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0026] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0027] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0028] See Figures 1 to 4 As shown, this utility model provides a specific embodiment of a voltage holding circuit, including: a rectifier bridge unit 1, a PFC unit 2 (Power Factor Correction unit), and an LLC unit 3 (LLC Resonant Converter unit); the PFC unit 2 includes: a boost module 21, a capacitor C1, a capacitor C3, a first switch Q4, a second switch Q5, and a control module; The output terminal of rectifier bridge unit 1 is connected to the input terminal of boost module 21 and the first terminal of second switch Q5; the second terminal of second switch Q5 is connected to the first terminal of capacitor C3 and the first terminal of first switch Q4; the second terminal of capacitor C3 is connected to the first terminal of capacitor C1; the second terminal of first switch Q4 is connected to the second terminal of capacitor C1, the output terminal of boost module 21 and the input terminal of LLC unit 3; the control module is connected to first switch Q4 and second switch Q5.

[0029] Specifically, rectifier bridge unit 1 is used to connect to external AC voltage and convert AC voltage to DC voltage, PFC unit 2 is used to boost DC voltage and adjust power factor to obtain stable DC high voltage, LLC unit 3 is used to convert DC high voltage to DC low voltage and supply it to the load, and the control module is used to control the state switching of the first switch Q4 and the second switch Q5 according to the input voltage of the entire circuit (i.e., the external AC voltage connected to rectifier bridge unit 1). When the circuit's input voltage is working normally, the rectifier bridge unit 1, boost module 21, and LLC unit 3 all operate normally. At this time, the control module controls the second switch Q5 to be in the off state and the first switch Q4 to be in the on state. Capacitor C3 is charged and discharged only through the path of the first switch Q4, so that capacitor C3 and capacitor C1 are connected in parallel and together serve as the output capacitor of the PFC unit, supplying power to LLC unit 3. When the circuit's input voltage drops, the control module controls the first switch Q4 to be in the off state and the second switch Q5 to be in the on state. Capacitor C3 is discharged only through the path of the second switch Q5, so that capacitor C3 switches to the input capacitor of PFC unit 2. The voltage of capacitor C3 is boosted by boost module 21 and sent to capacitor C1, and then supplied to LLC unit 3. In this way, the charge stored in capacitor C3 can be fully utilized, achieving the purpose of extending the power-off protection time. This embodiment fully utilizes each circuit element under both normal and power-off conditions, improving the efficiency of these elements and avoiding the need for additional components specifically designed for voltage boosting during power loss. This avoids additional power loss caused by extra components, achieving both extended power-off hold-up time and improved power efficiency, demonstrating promising application prospects.

[0030] In one embodiment, the control module includes a control chip, which has a first output pin and a second output pin; the first output pin is connected to a first switch Q4; and the second output pin is connected to a second switch Q5.

[0031] Specifically, both the first and second output pins have two states: high and low. When the input voltage is normal, the control chip controls the first output pin to be high to turn on the first switch Q4 and the second output pin to be low to turn off the second switch Q5, thus achieving parallel connection of capacitors C1 and C3. When the input voltage is off, the control chip controls the first output pin to be low to turn off the first switch Q4 and the second output pin to be high to turn on the second switch Q5, thus switching capacitor C1 from an output capacitor to an input capacitor. This design enables precise and reliable control of the different connection methods of capacitors C3 and C1 under normal power supply and power-off conditions. The control is precise and reliable, and can quickly respond to changes in the power input voltage, ensuring stable operation of the circuit under different conditions and effectively extending the power-off retention time.

[0032] In one embodiment, the control module further includes a power supply VCC1, resistors R1 and R2, and an optocoupler IC1. The first end of resistor R1 is connected to the second output pin, and the second end is connected to pin 1 of optocoupler IC1. Pin 3 of optocoupler IC1 is connected to the second switch Q5 and the first end of resistor R2. The second end of resistor R2 is connected to the output of rectifier bridge unit 1; power supply VCC1 is connected to pin 4 of optocoupler IC1.

[0033] Specifically, the core purpose of using optocoupler IC1 in the control module is to achieve electrical isolation between the control signal and the main circuit. The control signal output from the second output pin of the control chip is typically a low-voltage, low-power logic signal, while the second switch Q5 operates in the main circuit and may withstand high voltage and high current. Optocoupler IC1 can convert the electrical signal into an optical signal and then back into an electrical signal, transmitting the control signal while avoiding strong electrical interference from the main circuit to the control chip, ensuring the accuracy and stability of the control signal. Power supply VCC1 serves as the driving voltage for the second switch Q5, providing the necessary energy for its conduction and cutoff. Since the signal power output from the control chip may not be sufficient to directly drive the second switch Q5, the cooperation of optocoupler IC1 and power supply VCC1 can amplify the control signal to a suitable power level, enabling the second switch Q5 to operate reliably. Resistor R1 acts as a current limiter, protecting the input terminal of optocoupler IC1; resistor R2 is used to adjust the signal level at the output terminal of optocoupler IC1 to match the driving requirements of the second switch Q5. This design allows the control module to flexibly adjust parameters according to different application scenarios and the characteristics of the second switch Q5, ensuring circuit stability.

[0034] More specifically, the specific operation of this circuit structure is as follows: The control chip outputs a control signal through the second output pin based on the detected power input voltage state. When the power input voltage is normal, the output signal is low; when the power input voltage is low, the output signal is high. After being current-limited by resistor R1, the control signal enters pin 1 of optocoupler IC1. If the control signal is high, the LED inside optocoupler IC1 conducts and emits light. After receiving the light signal, the photosensitive device inside optocoupler IC1 generates a corresponding current at pin 3. Power supply VCC1 provides energy for this process, ensuring sufficient power for the output signal. The signal output from pin 3, after being leveled by resistor R2, is applied as the driving voltage to the control terminal of the second switch Q5. When the driving voltage reaches the conduction threshold of the second switch Q5, the second switch Q5 conducts; when the driving voltage is below the threshold, the second switch Q5 is turned off.

[0035] In one embodiment, the control module further includes a power supply VCC2, resistors R3 and R4, and an optocoupler IC2. The first end of resistor R3 is connected to the first output pin, and the second end is connected to pin 1 of optocoupler IC2. Pin 3 of optocoupler IC2 is connected to the first switch Q4 and the first end of resistor R4. The second end of resistor R4 is connected to the first end of capacitor C3. Power supply VCC2 is connected to pin 4 of optocoupler IC2. Similar to the connection between the second switch Q5 and the control chip, this embodiment uses components such as optocoupler IC2 to achieve electrical isolation between the control chip and the first switch Q4. The signal from the first output pin of the control chip is transmitted to pin 1 of optocoupler IC2 via resistor R3. After photoelectric conversion, the output signal from pin 3 of optocoupler IC2 controls the conduction and cutoff of the first switch Q4 via resistor R4. This design further improves the circuit's anti-interference capability and ensures the stable operation of the first switch Q4.

[0036] It is understandable that pin 2 of optocoupler IC1 and pin 2 of optocoupler IC2 are both grounded, thereby ensuring that the input side circuit of the optocoupler has an independent potential reference, avoiding the influence of the potential change on the output side circuit on the input side, thus effectively preventing electrical interference and signal crosstalk between the input and output circuits, improving the anti-interference capability and stability of the entire circuit, and thus accurately transmitting the control signal of the control chip to the control terminal of the switching transistor (such as Q4, Q5).

[0037] In one embodiment, the capacitance of capacitor C3 is greater than that of capacitor C1.

[0038] Specifically, after the power input voltage drops, capacitor C3, acting as the PFC input capacitor, stores energy that is boosted by the boost module 21 and then transferred to capacitor C1, which in turn powers LLC unit 3. By selecting a capacitor C3 with a larger capacitance, more energy can be provided to LLC unit 3 after a power outage, thus providing power to LLC unit 3 for a longer period, significantly extending the power outage hold-up time and improving power supply reliability.

[0039] In one embodiment, the boost module 21 includes an inductor L1, a diode D2, and a third switch Q3; the first end of the inductor L1 is connected to the output end of the rectifier bridge unit 1, and the second end is connected to the first end of the diode D2; the second end of the diode D2 is connected to the input end of the LLC unit 3; the first end of the third switch Q3 is connected to the second end of the capacitor C3, and the second end is connected to the second end of the inductor L1 and the first end of the diode D2.

[0040] Specifically, inductor L1 acts as an energy storage element. When the third switch Q3 is on, inductor L1 forms a path with the output terminal of rectifier bridge unit 1, and current flows through inductor L1, storing energy. When the third switch Q3 is off, the energy stored in inductor L1 begins to be released. Diode D2 serves as isolation and unidirectional conduction. When the third switch Q3 is on, diode D2 is reverse biased, preventing current from flowing to LLC unit 3. When the third switch Q3 is off, the energy released by inductor L1 causes diode D2 to conduct in the forward direction, transferring the energy in inductor L1 to LLC unit 3. The third switch Q3 is used to control the energy storage and release process of inductor L1. By periodically turning the third switch Q3 on and off, continuous boost operation can be achieved. When the third switch Q3 is on, inductor L1 stores energy; when the third switch Q3 is off, inductor L1 releases energy, which is transferred to capacitor C1 and LLC unit 3 through diode D2, achieving boost. The boost module 21 utilizes the energy storage and release characteristics of an inductor to efficiently raise a lower input voltage to a higher output voltage. Compared to other boost methods, such as linear regulator boost, this inductor-based boost method is more efficient because energy loss during inductor energy storage and release is mainly concentrated in the conduction losses of the switching element (third switch Q3) and diode D2. These losses are relatively small, and the output voltage of the boost module 21 can be precisely controlled by reasonably controlling the on and off times (i.e., duty cycle) of the third switch Q3. Simultaneously, capacitor C3 acts as a filter and energy storage unit at the output, smoothing output voltage fluctuations and ensuring a stable DC voltage for LLC unit 3, meeting the power supply stability requirements of subsequent circuits.

[0041] In one embodiment, the control chip has a PWM output pin, and a third switch Q3 is connected to the PWM output pin.

[0042] Specifically, the control chip controls the third switch Q3 through the PWM output pin, and precisely controls the boost process of the boost module 21 by adjusting the duty cycle of the PWM signal. During operation, the control chip can adjust the duty cycle of the PWM signal according to the power supply's operating state and output requirements, thereby changing the on and off times of the third switch Q3, achieving precise control of the output voltage of the boost module 21, thus improving the control accuracy of the boost module 21 and ensuring the stability and accuracy of the power supply's output voltage.

[0043] In one embodiment, the first switch Q4, the second switch Q5, and the third switch Q3 are MOSFETs or IGBTs; the control module is connected to the gate of the MOSFET or the gate of the IGBT; the first terminal of the first switch Q4, the first terminal of the second switch Q5, and the first terminal of the third switch Q3 are the source of the MOSFET or the emitter of the IGBT; the second terminal of the first switch Q4, the second terminal of the second switch Q5, and the second terminal of the third switch Q3 are the drain of the MOSFET or the collector of the IGBT.

[0044] Specifically, both MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and IGBTs (Insulated-Gate Bipolar Transistors) can rapidly switch between on and off states. In power supply circuits, frequent control of current flow is necessary to achieve functions such as power conversion and voltage regulation. For example, in boost module 21, the third switch Q3 needs to be rapidly switched on and off to allow inductor L1 to alternately store and release energy, thereby achieving voltage boost. Both MOSFETs and IGBTs are voltage-controlled devices; by applying a suitable voltage signal to the gate (the gate for IGBTs, and the same applies to MOSFETs), their on / off states can be controlled. By connecting the control module to the gate, precise control of the switch can be easily achieved, enabling different operating modes of the circuit. When the gate receives a suitable control voltage, the MOSFET or IGBT will correspondingly turn on or off. Taking a MOSFET as an example, when the gate voltage is higher than the threshold voltage, the MOSFET is on, and current can flow from the source to the drain; when the gate voltage is lower than the threshold voltage, the MOSFET is off, and current cannot flow. This embodiment utilizes the fast switching characteristics of MOSFETs and IGBTs, enabling the circuit to complete the turn-on and turn-off processes in a short time, reducing energy loss during switching. Furthermore, because MOSFETs and IGBTs can adapt to higher switching frequencies, the circuit can use smaller inductors, capacitors, and other components, reducing the size and weight of the power supply and increasing power density. Additionally, the low on-resistance of MOSFETs and the low on-voltage drop of IGBTs result in minimal power loss of the switching elements in the on-state. This not only reduces energy waste but also reduces component heat generation, improving component reliability and lifespan. Moreover, since MOSFETs and IGBTs are voltage-controlled devices, applying a suitable voltage signal to the gate allows for convenient control of the switch's on / off state, enabling precise circuit adjustment. The control module can quickly adjust the switch state based on the real-time power supply status, ensuring stable power output.

[0045] In one embodiment, the first switch Q4 and the second switch Q5 are surface mount components.

[0046] Specifically, surface-mount (SMD) components are small in size, occupying a much smaller area on the circuit board than traditional through-hole components. Designing the first switch Q4 and the second switch Q5 as SMD components effectively reduces the space occupied by components on the circuit board, allowing for a more compact layout of the entire power supply circuit and facilitating the miniaturization of the power module. Furthermore, the shorter leads of SMD components significantly reduce parasitic parameters such as lead inductance and capacitance. In high-frequency circuits, these parasitic parameters can significantly impact circuit performance, such as causing signal distortion and increasing electromagnetic interference. Since the first switch Q4 and the second switch Q5 require frequent switching operations in the power supply circuit and operate at high frequencies, using SMD components reduces the impact of parasitic parameters, improves switching response speed and circuit stability, and ensures efficient operation of the power supply circuit. In addition, SMD components are well-suited for automated manufacturing processes. In mass production, pick-and-place machines can quickly and accurately install SMD components onto the circuit board, improving production efficiency and reducing production costs. In contrast, the installation of through-hole components requires manual labor or more complex insertion equipment, resulting in lower production efficiency and a higher risk of installation errors. Therefore, using surface-mount first switch Q4 and second switch Q5 helps to achieve large-scale automated production of power supply circuits.

[0047] In one embodiment, the control chip is model DSPIC33FJ64GS606.

[0048] Specifically, in the voltage holding circuit, multiple switches (such as the first switch Q4, the second switch Q5, and the third switch Q3) require precise control. The DSPIC33FJ64GS606 control chip has multiple output pins, such as the first output pin, the second output pin, and the PWM output pin mentioned in the technical solution. These pins can be connected to different switching elements to achieve independent control of each switch, thereby flexibly adjusting the connection state of capacitors C3 and C1 and the operating mode of the boost module 21 to adapt to different operating conditions such as normal power supply operation and power failure. Furthermore, this control chip possesses powerful analog and digital signal processing capabilities. In the power supply circuit, it is necessary to monitor analog signals such as input voltage and capacitor voltage in real time and make corresponding control decisions based on changes in these signals. The DSPIC33FJ64GS606 integrates an analog-to-digital converter (ADC) that can convert analog signals into digital signals for processing. For example, by detecting the output voltage of rectifier bridge unit 1 and the voltages of capacitors C3 and C1, the control chip can accurately determine the operating state of the power supply and adjust the on and off times of the switches in a timely manner to ensure the stability of the power supply output.

[0049] The above embodiments are preferred implementations of this utility model. In addition, this utility model can also be implemented in other ways. Any obvious substitutions without departing from the concept of this technical solution are within the protection scope of this utility model.

Claims

1. A voltage holding circuit, characterized in that, include: Rectifier bridge unit, PFC unit, LLC unit; The PFC unit includes: a boost module, capacitor C1, capacitor C3, a first switch Q4, a second switch Q5, and a control module; The output terminal of the rectifier bridge unit is connected to the input terminal of the boost module and the first terminal of the second switch Q5; the second terminal of the second switch Q5 is connected to the first terminal of the capacitor C3 and the first terminal of the first switch Q4; the second terminal of the capacitor C3 is connected to the first terminal of the capacitor C1; the second terminal of the first switch Q4 is connected to the second terminal of the capacitor C1, the output terminal of the boost module, and the input terminal of the LLC unit; the control module is connected to the first switch Q4 and the second switch Q5.

2. The voltage holding circuit according to claim 1, characterized in that, The control module includes a control chip, which has a first output pin and a second output pin; the first output pin is connected to the first switch Q4; and the second output pin is connected to the second switch Q5.

3. The voltage holding circuit according to claim 2, characterized in that, The control module also includes a power supply VCC1, resistors R1 and R2, and an optocoupler IC1; the first end of resistor R1 is connected to the second output pin, and the second end is connected to pin 1 of the optocoupler IC1; pin 3 of the optocoupler IC1 is connected to the second switch Q5 and the first end of resistor R2; the second end of resistor R2 is connected to the output terminal of the rectifier bridge unit; and the power supply VCC1 is connected to pin 4 of the optocoupler IC1.

4. The voltage holding circuit according to claim 2, characterized in that, The control module also includes a power supply VCC2, resistors R3 and R4, and an optocoupler IC2; the first end of resistor R3 is connected to the first output pin, and the second end is connected to pin 1 of the optocoupler IC2; pin 3 of the optocoupler IC2 is connected to the first switch Q4 and the first end of resistor R4; the second end of resistor R4 is connected to the first end of capacitor C3; and the power supply VCC2 is connected to pin 4 of the optocoupler IC2.

5. The voltage holding circuit according to claim 1, characterized in that, The capacitance of capacitor C3 is greater than that of capacitor C1.

6. The voltage holding circuit according to claim 2, characterized in that, The boost module includes an inductor L1, a diode D2, and a third switch Q3; the first end of the inductor L1 is connected to the output end of the rectifier bridge unit, and the second end is connected to the first end of the diode D2; the second end of the diode D2 is connected to the input end of the LLC unit; the first end of the third switch Q3 is connected to the second end of the capacitor C3, and the second end is connected to the second end of the inductor L1 and the first end of the diode D2.

7. The voltage holding circuit according to claim 6, characterized in that, The control chip has a PWM output pin, and the third switch Q3 is connected to the PWM output pin.

8. The voltage holding circuit according to claim 7, characterized in that, The first switch Q4, the second switch Q5, and the third switch Q3 are MOSFETs or IGBTs; the control chip is connected to the gate of the MOSFET or the gate of the IGBT; the first terminal of the first switch Q4, the first terminal of the second switch Q5, and the first terminal of the third switch Q3 are the source of the MOSFET or the emitter of the IGBT; the second terminal of the first switch Q4, the second terminal of the second switch Q5, and the second terminal of the third switch Q3 are the drain of the MOSFET or the collector of the IGBT.

9. The voltage holding circuit according to claim 1, characterized in that, The first switch Q4 and the second switch Q5 are surface mount components.

10. The voltage holding circuit according to claim 2, characterized in that, The control chip is model DSPIC33FJ64GS606.

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