Power management system, control circuit and control method for llc converter

Abstract

One aspect of this disclosure is a control module for an LLC converter with a PFC circuit and an LLC circuit. A bulk capacitor is located between the PFC circuit and the LLC circuit. The control module includes a secondary-side controller coupled to the output of the LLC circuit for receiving the output current of the LLC circuit. The control module also includes an optocoupler circuit coupled to the secondary-side controller. The control module also includes a primary-side controller coupled to both the optocoupler circuit and the PFC circuit. The secondary-side controller generates a PWM signal based on fluctuations in the output current and outputs it to the optocoupler circuit. The optocoupler circuit converts the PWM signal into an analog signal and sends it to the primary-side controller. The primary-side controller adjusts the input current of the PFC circuit based on the analog signal to maintain a stable capacitor voltage across the bulk capacitor.

Description

Technical Field

[0001] This invention relates to a power management system and a control technique for LLC converters, particularly a control technique for controlling relevant electrical parameters between the primary and secondary sides using an optocoupler. Prior Technology

[0002] In modern high-power-density and high-power-output power supply units (PSUs), when the output load undergoes large changes—for example, when the output load increases significantly due to electronic data peak processing (EDPP) settings (e.g., from 20% to 170%)—the front-end power factor correction (PFC) circuit reacts slowly to load changes. This causes the voltage of the large-capacity capacitors within the PFC circuit to continuously decrease, gradually increasing the resonant current on the primary side of the LLC circuit until it triggers cycle-by-cycle protection (CBC) or lowers the PFC output voltage, ultimately triggering under-voltage protection (UVP) and shutting down the system. Therefore, there is a need for technology that can maintain a balance between the input and output power of the PFC circuit and stabilize the voltage of the large-capacity capacitors based on output current fluctuations. Summary of the Invention

[0003] The technology provided by this invention transmits the output current fluctuation information obtained by the secondary controller to the primary controller through an optocoupler circuit. When the primary controller receives the relevant information, it adjusts the input current of the PFC circuit to compensate the large-capacity capacitor in real time to stabilize its capacitor voltage.

[0004] According to a first aspect of the present invention, a control module is provided for an LLC converter having a power factor correction (PFC) circuit and an inductor-inductor-capacitor (LLC) circuit. A bulk capacitor is provided between the PFC circuit and the LLC circuit. The control module includes a secondary-side controller coupled to the output of the LLC circuit for receiving the output current of the LLC circuit. The control module also includes an optocoupler circuit coupled to the secondary-side controller. The control module also includes a primary-side controller coupled to the optocoupler circuit and the PFC circuit. The secondary-side controller generates a PWM signal based on fluctuations in the output current and outputs it to the optocoupler circuit. The optocoupler circuit converts the PWM signal into an analog signal and sends it to the primary-side controller. The primary-side controller adjusts the input current of the PFC circuit based on the analog signal to maintain the stability of the capacitor voltage of the bulk capacitor.

[0005] According to a second aspect of the present invention, a control method is provided for an LLC converter having a PFC circuit and an LLC circuit. A large-capacity capacitor is provided between the PFC circuit and the LLC circuit. The control method includes receiving the output current of the LLC circuit by a secondary-side controller. The control method also includes generating a PWM signal based on fluctuations in the output current by the secondary-side controller and outputting it to an optocoupler circuit. The control method also includes converting the PWM signal into an analog signal by the optocoupler circuit and sending it to a primary-side controller. The control method also includes adjusting the input current of the PFC circuit based on the analog signal by the primary-side controller to maintain the stability of the capacitor voltage of the large-capacity capacitor.

[0006] According to a third aspect of the present invention, a power management system is provided. The power management system includes an LLC converter. The LLC converter includes a PFC circuit and an LLC circuit. A large-capacity capacitor is located between the PFC circuit and the LLC circuit. The power management system also includes a control module. The control module includes a secondary-side controller coupled to the output of the LLC circuit for receiving the output current of the LLC circuit. The control module also includes an optocoupler circuit coupled to the secondary-side controller. The control module also includes a primary-side controller coupled to the optocoupler circuit and the PFC circuit. The secondary-side controller generates a PWM signal based on fluctuations in the output current and outputs it to the optocoupler circuit. The optocoupler circuit converts the PWM signal into an analog signal and sends it to the primary-side controller. The primary-side controller adjusts the input current of the PFC circuit based on the analog signal to maintain the stability of the capacitor voltage of the large-capacity capacitor.

[0007] The foregoing description is not intended to represent every embodiment or aspect of the invention. Rather, it provides only examples of some novel aspects and features of the invention. The foregoing description will become apparent, as well as other features and advantages of the invention, from the following detailed description of representative embodiments and modes of implementation when taken in conjunction with the accompanying drawings and the claims. Other aspects of the invention will be apparent to those skilled in the art from the detailed description of various embodiments with reference to the drawings and the brief description provided below.

[0008] To provide a better understanding of the above and other aspects of the present invention, specific embodiments are described below in conjunction with the accompanying drawings: Simple Explanation of the Diagram

[0009] Figure 1 illustrates a functional block diagram of a control module for an LLC converter according to various embodiments of the present invention. Figure 2 illustrates the waveform of the control module controlling the PFC circuit according to various embodiments of the present invention. Figure 3 illustrates a flowchart of a control program for an LLC converter according to various embodiments of the present invention. Implementation

[0010] The following detailed embodiments of the present invention, illustrated in the accompanying drawings. In addition to these detailed descriptions, the present invention can be widely implemented in other embodiments, and any easy substitutions, modifications, or equivalent changes to the described embodiments are included within the scope of the present invention and are subject to the following patent claims. In the description of the specification, many specific details and implementation examples are provided to give the reader a more complete understanding of the present invention; however, these specific details and implementation examples should not be considered as limitations on the present invention. Furthermore, well-known steps or elements are not described in the details to avoid unnecessary limitations on the present invention. In the drawings, the same or similar element symbols are used to represent the same or similar elements.

[0011] Figure 1 illustrates a functional block diagram of a control module 200 for an LLC converter 1000 according to various embodiments of the present invention. The LLC converter 1000 includes a PFC circuit 110, a large-capacity capacitor 130, and an LLC circuit 120. The large-capacity capacitor 130 is disposed between the PFC circuit 110 and the LLC circuit 120, and the discharge output of the large-capacity capacitor 130 is related to the output power (or voltage) of the PFC circuit. The LLC circuit 120 is coupled to a load 140 and provides output current to the load 140.

[0012] The control module 200 includes a secondary-side controller 210, an optocoupler circuit 230, and a primary-side controller 220. The secondary-side controller 210 is coupled to the output of the LLC circuit 120 and can receive the output current of the LLC circuit 120 and generate a corresponding PWM signal, which can respond to fluctuations in the output current, as shown in Figure 1. In some embodiments, the secondary-side controller 210 may be part of the LLC circuit 120, or it may be implemented by the controller originally used in the LLC circuit 120, such as a digital signal processor (DSP) for controlling the LLC circuit 120. The optocoupler circuit 230 includes an optocoupler 231 and a filter circuit 232, and is coupled to the secondary-side controller 210 and the primary-side controller 220. Optocoupler 231 can be used to transmit the PWM signal generated by secondary controller 210 to primary controller 220. The transmitting and receiving ends of optocoupler 231 are connected, while filter circuit 232 converts the PWM signal received from the receiving end of optocoupler 231 into an analog signal and provides the analog signal to primary controller 220. Primary controller 220 is coupled to optocoupler circuit 230 and PFC circuit 110. When primary controller 220 receives an analog signal corresponding to the output current fluctuation, it can adjust the input current of PFC circuit 110 according to the analog signal, that is, make the input power of PFC circuit 110 greater than or equal to its output power, i.e., satisfying (Vin*Iin)≥ (Vout*Iout) / η, where Vin and Iin are the input voltage and input current of PFC circuit 110, respectively, Vout and Iout are the output voltage and output current of LLC circuit 120, respectively, and η is the conversion efficiency. For example, when the primary-side controller 220 receives an analog signal corresponding to an output current fluctuation (or jump), it can quickly adjust the input current of the PFC circuit 110, causing the input current to increase rapidly. In some embodiments, the primary-side controller 220 may be part of the PFC circuit 110, or it may be implemented by the controller originally used in the PFC circuit 110, such as a digital signal processor (DSP) for controlling the PFC circuit 110. Through the above operations, by adjusting the input current of the PFC circuit 110, the input / output power is balanced, and the capacitor voltage of the large-capacity capacitor 130 can be kept stable.

[0013] Specifically, the secondary-side controller 210, by acquiring the output current of the LLC circuit 120, can determine whether a dynamic load has occurred, i.e., a large fluctuation, such as when the load suddenly increases from 20% to 170% (e.g., the output current increases by 1.4 to 1.8 times). Based on this change in output current, it can generate a PWM signal to the optocoupler circuit 230. After being transmitted and converted by the optocoupler circuit 230, the PWM signal is converted into an analog signal. The primary-side controller 220 can read this analog signal to obtain the load change (or change value) of the output current. Based on this change value, the primary-side controller 220 can calculate the change value of the LLC circuit output power, and then calculate the corresponding change in input current, so that the integral value of the PFC circuit 110 (e.g., through a proportional-integral (PI) controller) increases to a corresponding value, balancing the input / output power. This prevents the capacitor voltage of the large-capacity capacitor from dropping below the lower limit, ensuring that the capacitor voltage fluctuation range is controlled within a certain range, thereby stabilizing the output voltage.

[0014] In some implementations, when the primary-side controller 220 increases the input current of the PFC circuit 110, causing the capacitor voltage of the large-capacity capacitor 130 to increase, if the capacitor voltage exceeds an upper limit, for example, above 435V, the primary-side controller 220 shuts off the input current of the PFC circuit 110 until the capacitor voltage of the large-capacity capacitor 130 drops below a lower limit, for example, below 415V, at which point the input current of the PFC circuit 110 is turned on again. This ensures that the capacitor voltage of the large-capacity capacitor 130 does not exceed the upper voltage limit of the large-capacity capacitor 130.

[0015] Figure 2 illustrates waveforms of the control module controlling the PFC circuit according to various embodiments of the present invention. Through the operations described above, as shown in waveform 200A, by adjusting the input current of the PFC circuit (corresponding to changes in the output current of the LLC circuit), the capacitor voltage of the large-capacity capacitor between the PFC circuit and the LLC circuit can be controlled between 470V and 390V. That is, the fluctuation range of the capacitor voltage is controlled and stabilized within a certain range. Therefore, the overall output voltage of the system can be stabilized, and the CBC protection will not be triggered due to a sudden and significant change in the output current caused by a large change in EDPP.

[0016] Figure 3 illustrates a flowchart of a control procedure for an LLC converter according to various embodiments of the present invention. In step S310, the secondary-side controller (e.g., the secondary-side controller 210 of Figure 1) receives the output current of the LLC circuit (e.g., the LLC circuit 120 of Figure 1).

[0017] In step S320, the control method also includes generating a PWM signal by the secondary-side controller based on the fluctuation of the output current and outputting it to the optocoupler circuit (e.g., optocoupler circuit 230 in Figure 1).

[0018] In step S330, the optocoupler circuit converts the PWM signal into an analog signal and sends it to the primary side controller (e.g., the primary side controller 220 in Figure 1).

[0019] In step S340, the primary-side controller adjusts the input current of the PFC circuit (e.g., PFC circuit 110 in Figure 1) according to the analog signal to maintain the stability of the capacitor voltage of the large-capacity capacitor (e.g., large-capacity capacitor 130 in Figure 1). Then, it can return to step S310 to continue receiving the output current of the LLC circuit to maintain the stability of the capacitor voltage.

[0020] In some specific setups, the optocoupler circuit includes an optocoupler and a filter circuit. The optocoupler is used to transmit PWM signals, and the filter circuit is used to convert the PWM signals into analog signals.

[0021] In certain configurations, adjusting the input current of the PFC circuit via a primary-side controller includes: calculating the change in the output power of the LLC circuit based on fluctuations in the output current corresponding to the analog signal; and calculating the change in the input current based on the change in output power, and adjusting the input current so that the input power of the PFC circuit is greater than or equal to the output power. The input power is the product of the input voltage and input current of the PFC circuit.

[0022] In certain settings, the output power corresponds to a change in the output current, which can increase from the original output current to 1.4 to 1.8 times.

[0023] In some specific settings, the secondary controller generates a PWM signal to the optocoupler circuit based on the output current increasing by 1.4 to 1.8 times.

[0024] In certain settings, the primary-side controller can calculate the change in output power of the LLC circuit based on the increase in output current from 1.4 to 1.8 times, and then calculate the required change in input current of the PFC circuit, so that the PFC circuit increases the corresponding value of the integral value of the proportional-integral controller to the input current.

[0025] In certain specific settings, adjusting the input current of the PFC circuit by the primary-side controller includes: when the primary-side controller increases the input current of the PFC circuit, causing the capacitor voltage of the large-capacity capacitor to increase, if the capacitor voltage exceeds the upper limit, the primary-side controller shuts off the input current of the PFC circuit.

[0026] In certain specific settings, adjusting the input current of the PFC circuit by the primary-side controller includes: when the primary-side controller shuts off the input current of the PFC circuit, causing the capacitor voltage of the large-capacity capacitor to drop, and when the capacitor voltage drops below the lower limit, turning on the input current of the PFC circuit.

[0027] Various embodiments are described with reference to the accompanying drawings, wherein all drawings use the same element reference numerals to denote similar or equivalent elements. The drawings are not necessarily drawn to scale and are provided only to illustrate aspects and features of the invention. Numerous specific details, relationships, and methods are set forth to provide a comprehensive understanding of certain aspects and features of the invention, although those skilled in the art will recognize that these aspects and features can be implemented without one or more of the specific details, relationships, or methods. In some cases, well-known structures or operations are not shown in detail for illustrative purposes. The various embodiments disclosed herein are not necessarily limited to the order of the described actions or events, as some actions may occur in a different order and / or simultaneously with other actions or events. Furthermore, not all actions or events in the drawings are necessary to realize certain aspects and features of the invention.

[0028] Although the invention has been described and illustrated with respect to one or more embodiments, other skilled in the art will recognize or understand equivalent changes and modifications upon reading and understanding this specification and the accompanying drawings. Furthermore, while a particular feature of the invention may be disclosed only in one of several embodiments, this feature may be combined with one or more other features of other embodiments, as these features may be desired and advantageous for any given or particular application.

[0029] While various embodiments of the invention have been described above, it should be understood that they are presented by way of example only and not as limitation. Many changes may be made to the disclosed embodiments based on the disclosure without departing from the spirit or scope of the invention. Therefore, the breadth and scope of the invention should not be limited by any of the above embodiments. Rather, the scope of the invention should be defined according to the appended claims and their equivalents.

[0030] 1000: LLC Converter 110: PFC circuit 120: LLC circuit 130: Large-capacity capacitor 140: Load 200: Control Module 200A: Waveform Diagram 210: Secondary side controller 220: Primary Side Controller 230: Optical coupling circuit 231: Optical Coupler 232: Filtering Circuit S310~S340: Steps

Claims

1. A control module for an LLC converter having a power factor correction (PFC) circuit and an LLC circuit, wherein a bulk capacitor is provided between the PFC circuit and the LLC circuit, the control module comprising: A primary and secondary side controller is coupled to an output of the LLC circuit to receive an output current of the LLC circuit. An optocoupler circuit is coupled to the secondary-side controller; a primary-side controller is coupled to the optocoupler circuit and the PFC circuit, wherein the secondary-side controller generates a PWM signal based on the fluctuation of the output current and outputs it to the optocoupler circuit, the optocoupler circuit converts the PWM signal into an analog signal and sends it to the primary-side controller, wherein the primary-side controller adjusts an input current of the PFC circuit based on the analog signal to maintain the stability of a capacitor voltage of the large-capacity capacitor.

2. The control module as described in claim 1, wherein the optocoupler circuit includes an optocoupler and a filter circuit, wherein the optocoupler is used to transmit the PWM signal, and the filter circuit is used to convert the PWM signal into the analog signal.

3. The control module as described in claim 1, wherein the primary-side controller adjusts the input current of the PFC circuit according to the analog signal by: calculating a change in the output power of the LLC circuit based on the fluctuation of the output current corresponding to the analog signal; and calculating a change in the input current based on the change in the output power, and adjusting the input current so that an input power of the PFC circuit is greater than or equal to the output power, wherein the input power is the product of an input voltage of the PFC circuit and the input current.

4. The control module as described in claim 3, wherein the output power corresponds to the change in the output current, which is an increase from the original output current to 1.4 to 1.8 times.

5. The control module as described in claim 4, wherein the secondary-side controller generates the PWM signal to the optocoupler circuit based on the change in the output current from 1.4 times to 1.8 times.

6. The control module as described in claim 4, wherein the primary-side controller calculates the change in the output power of the LLC circuit based on the change in the output current from 1.4 times to 1.8 times, and then calculates the required change in the input current of the PFC circuit, so that the PFC circuit increases the input current by a corresponding value through an integral value of a proportional-integral controller.

7. The control module as described in claim 4, wherein when the primary controller increases the input current of the PFC circuit, causing the capacitor voltage of the large-capacity capacitor to increase, if the capacitor voltage exceeds an upper limit, the primary controller shuts off the input current of the PFC circuit until the capacitor voltage drops below a lower limit, at which point the input current of the PFC circuit is turned on.

8. A control method for an LLC converter having a PFC circuit and an LLC circuit, wherein a large capacitance capacitor is provided between the PFC circuit and the LLC circuit, the control method comprising: The secondary-side controller receives an output current from the LLC circuit; the secondary-side controller generates a PWM signal based on the fluctuation of the output current and outputs it to an optocoupler circuit; the optocoupler circuit converts the PWM signal into an analog signal and sends it to a primary-side controller; and the primary-side controller adjusts an input current of the PFC circuit based on the analog signal to maintain the stability of a capacitor voltage of the large-capacity capacitor.

9. The control method as described in claim 8, wherein the optocoupler circuit includes an optocoupler and a filter circuit, wherein the optocoupler is used to transmit the PWM signal, and the filter circuit is used to convert the PWM signal into the analog signal.

10. The control method as described in claim 8, wherein adjusting the input current of the PFC circuit by the primary-side controller comprises: Based on the fluctuation of the output current corresponding to the analog signal, the change in the output power of the LLC circuit is calculated; And calculate the change in input current based on the change in output power, and adjust the input current so that an input power of the PFC circuit is greater than or equal to the output power, wherein the input power is the product of an input voltage and an input current of the PFC circuit.

11. The control method as described in claim 10, wherein the output power corresponds to a change in the output current, which is an increase from the original output current to 1.4 to 1.8 times.

12. The control method as described in claim 11, wherein the secondary-side controller generates the PWM signal to the optocoupler circuit based on the change in the output current from 1.4 times to 1.8 times.

13. The control method as described in claim 11, wherein the primary-side controller calculates the change in the output power of the LLC circuit based on the change in the output current from 1.4 times to 1.8 times, and then calculates the required change in the input current of the PFC circuit, so that the PFC circuit increases the input current by a corresponding value through an integral value of a proportional-integral controller.

14. The control method as described in claim 11, wherein adjusting the input current of the PFC circuit by the primary-side controller comprises: When the primary-side controller increases the input current of the PFC circuit, causing the capacitor voltage of the large-capacity capacitor to increase, if the capacitor voltage exceeds an upper limit, the primary-side controller shuts off the input current of the PFC circuit.

15. The control method as described in claim 11, wherein adjusting the input current of the PFC circuit by the primary-side controller includes: When the primary side controller shuts off the input current of the PFC circuit, causing the voltage of the large-capacity capacitor to drop, the input current of the PFC circuit is turned on when the voltage drops below a lower limit.

16. A power management system, comprising: An LLC converter includes: a PFC circuit; and an LLC circuit coupled to the PFC circuit, wherein a large-capacity capacitor is located between the PFC circuit and the LLC circuit; and a control module including: a secondary-side controller coupled to an output of the LLC circuit for receiving an output current of the LLC circuit; an optocoupler coupled to the secondary-side controller; and a primary-side controller coupled to the optocoupler circuit and the PFC circuit, wherein the secondary-side controller generates a PWM signal based on fluctuations in the output current and outputs it to the optocoupler circuit, the optocoupler circuit converts the PWM signal into an analog signal and sends it to the primary-side controller, wherein the primary-side controller adjusts an input current of the PFC circuit based on the analog signal to maintain a stable capacitor voltage of the large-capacity capacitor.

17. The power management system as claimed in claim 16, wherein the optocoupler circuit includes an optocoupler and a filter circuit, wherein the optocoupler is used to transmit the PWM signal, and the filter circuit is used to convert the PWM signal into the analog signal.

18. The power management system as claimed in claim 16, wherein the primary-side controller adjusts the input current of the PFC circuit according to the analog signal by: calculating a change in the output power of the LLC circuit based on fluctuations in the output current corresponding to the analog signal; and calculating a change in the input current based on the change in the output power, and adjusting the input current so that an input power of the PFC circuit is greater than or equal to the output power, wherein the input power is the product of an input voltage of the PFC circuit and the input current.

19. The power management system as described in claim 18, wherein the output power corresponds to a change in the output current, which is an increase from the original output current to 1.4 to 1.8 times.

20. The power management system as claimed in claim 19, wherein the secondary-side controller generates the PWM signal to the optocoupler circuit based on the change in the output current from 1.4 times to 1.8 times.

21. The power management system as claimed in claim 19, wherein the primary-side controller calculates the change in the output power of the LLC circuit based on the change in the output current from 1.4 times to 1.8 times, and then calculates the required change in the input current of the PFC circuit, so that the PFC circuit increases the input current by a corresponding value through an integral value of a proportional-integral controller.

22. The power management system as claimed in claim 19, wherein when the primary-side controller increases the input current of the PFC circuit, causing the capacitor voltage of the large-capacity capacitor to increase, if the capacitor voltage exceeds an upper limit, the primary-side controller shuts off the input current of the PFC circuit until the capacitor voltage drops below a lower limit, at which point the input current of the PFC circuit is turned on.

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