Power conversion circuit and control method thereof

Abstract

The invention discloses a power conversion circuit and a control method thereof. The circuit comprises a transformer, an upper bridge switch, a lower bridge switch and a control circuit. The transformer comprises a primary coil and a secondary coil. The secondary coil generates an output voltage of the power conversion circuit. The upper bridge switch and the lower bridge switch are coupled to the primary coil and serve as half-bridge circuits to magnetize and demagnetize the transformer. The control circuit respectively turns on the upper bridge switch and the lower bridge switch to adjust the output voltage based on the feedback signal and the current detection signal. The feedback signal is related to the output voltage, and the current detection signal represents the current flowing through the primary coil. The control circuit further generates a power signal related to the output current of the power conversion circuit based on the state of the upper bridge switch and the feedback signal.

Description

Technical Field

[0001] The present invention relates to a power conversion circuit and a control method thereof, and more particularly to an asymmetric half-bridge flyback power conversion circuit and a control method thereof that can directly obtain output power information without isolation. Background Art

[0002] A flyback converter is a voltage conversion circuit derived from a buck-boost converter. The buck-boost converter's single-winding inductor is replaced with a two-winding transformer, which then rectifies the output voltage using a rectifier (e.g., a diode).

[0003] To accurately control the output voltage of a flyback converter, closed-loop control is essential. To further precisely control the flyback converter's output power, output current detection is necessary. However, the output current detection signal must be provided to the primary-side control circuit through an isolation device, increasing the complexity of output current detection. Therefore, it is necessary to optimize the output current detection method. Summary of the Invention

[0004] The present invention proposes a power conversion circuit and a control method thereof that can directly obtain output power information without isolation, and protects the power conversion circuit through power information, and even uses the power information to control the power factor correction circuit of the previous stage, thereby increasing the overall conversion efficiency of the power system.

[0005] In view of the above, the present invention proposes a power conversion circuit, comprising a transformer, an upper bridge switch, a lower bridge switch, and a control circuit. The transformer comprises a primary coil and a secondary coil, wherein the secondary coil generates an output voltage of the power conversion circuit. The upper bridge switch and the lower bridge switch are coupled to the primary coil and, as a half-bridge circuit, magnetize and demagnetize the transformer. The control circuit adjusts the output voltage by turning on the upper bridge switch and the lower bridge switch, respectively, based on a feedback signal and a current detection signal. The feedback signal is related to the output voltage, and the current detection signal represents the current flowing through the primary coil. The control circuit further generates a power signal related to an output current of the power conversion circuit based on the state of the upper bridge switch and the feedback signal.

[0006] According to another embodiment of the present invention, the control circuit generates the power signal based on the on-time of the upper bridge switch, the on-time of the lower bridge switch, and the feedback signal.

[0007] According to one embodiment of the present invention, the transformer magnetization time is equal to the conduction time of the upper bridge switch, and the transformer demagnetization time is equal to the conduction time of the lower bridge switch.

[0008] According to an embodiment of the present invention, the control circuit generates the power signal based on an average of the feedback signals.

[0009] According to an embodiment of the present invention, the control circuit includes a low-pass filter, wherein the low-pass filter is configured to average the feedback signal to generate the power signal.

[0010] According to an embodiment of the present invention, when the power signal exceeds a threshold value, the control circuit drives the high-bridge switch and the low-bridge switch to reduce the output current.

[0011] According to another embodiment of the present invention, when the power signal exceeds a threshold value, the control circuit drives the upper bridge switch and the lower bridge switch so that the output current flowing through the secondary coil is a constant current.

[0012] According to an embodiment of the present invention, a power factor correction circuit is used to convert an AC voltage into an input voltage, and the power conversion circuit is used to convert the input voltage into the output voltage.

[0013] According to an embodiment of the present invention, when the power signal exceeds a threshold value, the power factor correction circuit increases the voltage value of the input voltage based on the power signal.

[0014] According to another embodiment of the present invention, when the power signal does not exceed a threshold value, the control circuit disables the power factor correction circuit. When the power signal exceeds the threshold value, the control circuit enables the power factor correction circuit.

[0015] The present invention further provides a control method for controlling a power conversion circuit. The power conversion circuit includes a transformer and a half-bridge circuit, wherein the transformer includes a primary coil and a secondary coil, wherein the half-bridge circuit includes an upper bridge switch and a lower bridge switch for magnetizing and demagnetizing the primary coil, respectively, so that the secondary coil generates an output voltage of the power conversion circuit. The control method includes: based on a feedback signal and a current detection signal, turning on the upper bridge switch and the lower bridge switch respectively to adjust the output voltage; and based on the state of the upper bridge switch and the feedback signal, generating a power signal related to an output current of the power conversion circuit. The feedback signal is related to the output voltage, and the current detection signal represents the current flowing through the primary coil.

[0016] According to another embodiment of the present invention, the step of generating the power signal related to the output current of the power conversion circuit based on the state of the upper bridge switch and the feedback signal further includes: generating the power signal based on the conduction time of the upper bridge switch, the conduction time of the lower bridge switch and the feedback signal.

[0017] According to one embodiment of the present invention, the transformer magnetization time is equal to the conduction time of the upper bridge switch, and the transformer demagnetization time is equal to the conduction time of the lower bridge switch.

[0018] According to an embodiment of the present invention, the step of generating the power signal related to the output current of the power conversion circuit based on the state of the upper bridge switch and the feedback signal further includes: generating the power signal based on an average of the feedback signal.

[0019] According to an embodiment of the present invention, the step of generating the power signal based on the average of the feedback signal further includes: averaging the feedback signal using a low-pass filter to generate the power signal.

[0020] According to an embodiment of the present invention, the control method further comprises: when the power signal exceeds a threshold value, driving the high-bridge switch and the low-bridge switch to reduce the output current.

[0021] According to another embodiment of the present invention, when the power signal exceeds a threshold value, the upper bridge switch and the lower bridge switch are driven such that the output current flowing through the secondary coil is a constant current.

[0022] According to an embodiment of the present invention, a power factor correction circuit is used to convert an AC voltage into an input voltage, wherein the power conversion circuit is used to convert the input voltage into the output voltage.

[0023] According to an embodiment of the present invention, the control method further comprises: when the power signal exceeds a threshold value, controlling the power factor correction circuit to increase the voltage value of the input voltage.

[0024] According to another embodiment of the present invention, the control method further includes: disabling the power factor correction circuit when the power signal does not exceed a threshold value; and enabling the power factor correction circuit when the power signal exceeds the threshold value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A circuit diagram showing a power conversion circuit according to an embodiment of the present invention;

[0026] Figure 2A block diagram showing a control circuit according to an embodiment of the present invention;

[0027] Figure 3 A block diagram showing a control circuit according to another embodiment of the present invention;

[0028] Figure 4 A block diagram showing a control circuit according to another embodiment of the present invention;

[0029] Figure 5 A block diagram of a judgment circuit according to an embodiment of the present invention is shown;

[0030] Figure 6 A block diagram showing a control circuit according to another embodiment of the present invention;

[0031] Figure 7 A schematic diagram showing a power system according to an embodiment of the present invention; and

[0032] Figure 8 A flowchart of a control method according to an embodiment of the present invention is shown.

[0033] Explanation of symbols

[0034] 100: Power conversion circuit

[0035] 110: Feedback circuit

[0036] 120: Signal processing circuit

[0037] 130, 200, 300, 400, 600: Control circuit

[0038] 210: Buffer circuit

[0039] 220: Low-pass filter

[0040] 410: Operational circuit

[0041] TM: Transformer

[0042] CR: resonant capacitor

[0043] QH: Upper bridge switch

[0044] QL: Lower bridge switch

[0045] RCS: Current detection resistor

[0046] CO: output capacitance

[0047] DR: Rectifier

[0048] PS: Primary coil

[0049] SS: Secondary coil

[0050] Lr: leakage inductance

[0051] Lm: Magnetizing inductance

[0052] HS: upper bridge drive signal

[0053] LS: lower bridge drive signal

[0054] VO: output voltage

[0055] VIN: input voltage

[0056] VCS: Current detection voltage

[0057] ILm: Excitation current

[0058] IC: Capacitor current

[0059] IO: output current

[0060] SFB: Feedback signal

[0061] SCS: Current detection signal

[0062] SPWR: power signal

[0063] AMP:Amplifier

[0064] OR: OR gate

[0065] SW1: First switch

[0066] SW2: Second switch

[0067] INV:Inverter

[0068] SINT: Transmission signal

[0069] RLP: Low pass resistance

[0070] CLP: Low-pass capacitor

[0071] SW3: The third switch

[0072] SW4: The fourth switch

[0073] 500: Judgment circuit

[0074] 510: Delay circuit

[0075] CMP: Comparator

[0076] TH: threshold value

[0077] CRT: Comparison Results

[0078] ST: Status signal

[0079] OFT:Offset

[0080] CSAMP: sampling capacitor

[0081] POR: Power-on reset signal

[0082] RD1: The first voltage divider resistor

[0083] RD2: The second voltage divider resistor

[0084] Q1: First transistor

[0085] VD: divided voltage

[0086] 700: Power System

[0087] 710: Power factor correction circuit

[0088] 720: Power conversion circuit

[0089] VIN_AC: AC input voltage

[0090] RD3: The third voltage divider resistor

[0091] RD4: The fourth voltage divider resistor

[0092] VFB_PFC: Power factor feedback voltage

[0093] Q2: Second transistor

[0094] RPD: Pull-down resistor

[0095] EN: Enable signal

[0096] 800: Control Method

[0097] S810~S820: Step Flow DETAILED DESCRIPTION

[0098] The following descriptions are examples of the present disclosure. Their purpose is to illustrate the general principles of the present disclosure and should not be considered as limiting the present disclosure, the scope of which should be determined by the scope of the claims.

[0099] It is worth noting that the following disclosure provides multiple embodiments or examples for practicing different features of the present disclosure. The specific component examples and arrangements described below are intended only to briefly illustrate the spirit of the present disclosure and are not intended to limit the scope of the present disclosure. In addition, the following description may reuse the same component symbols or characters in multiple examples. However, this repetition is intended only to provide simplified and clear descriptions and is not intended to define the relationship between the various embodiments and / or configurations discussed below.

[0100] In addition, the description of a feature being connected to, coupled to, and / or formed on another feature described in the following specification may actually include multiple different embodiments, including these features being in direct contact, or including other additional features formed between these features, etc., so that these features are not in direct contact.

[0101] In addition, relative terms such as "lower" or "bottom" and "upper" or "top" may be used in the embodiments to describe the relative relationship of one element to another element in the drawings. It is understood that if the device in the drawings is turned upside down, the element described as being on the "lower" side will become the element on the "upper" side.

[0102] It is understood that although the terms "first," "second," "third," etc. may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms, and these terms are merely used to distinguish different elements, components, regions, layers, and / or parts. Thus, a first element, component, region, layer, and / or part discussed below may be referred to as a second element, component, region, layer, and / or part without departing from the teachings of some embodiments of the present disclosure.

[0103] Some embodiments of the present disclosure can be understood in conjunction with the accompanying drawings, which are considered part of the description of the present disclosure. It should be noted that the drawings of the present disclosure are not drawn to scale for actual devices and components. The shapes and thicknesses of the embodiments may be exaggerated in the drawings to clearly illustrate the features of the present disclosure. Furthermore, the structures and devices in the drawings are schematically illustrated to clearly illustrate the features of the present disclosure.

[0104] Here, the terms "about," "approximately," and "substantially" generally mean within 20%, preferably within 10%, and more preferably within 5%, or within 3%, or within 2%, or within 1%, or within 0.5% of a given value or range. The quantities given here are approximate quantities, that is, in the absence of specific description of "about," "approximately," or "substantially," the meaning of "about," "approximately," or "substantially" may still be implied.

[0105] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meanings as commonly understood by one of ordinary skill in the art. It is understood that these terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with the background or context of the relevant art and this disclosure, and should not be interpreted in an idealized or overly formal manner unless specifically defined in the present disclosure.

[0106] In some embodiments of the present disclosure, terms such as "connected" and "interconnected," unless otherwise specified, may refer to two structures being in direct contact, or may refer to two structures not being in direct contact, with another structure positioned between them. Furthermore, such terms may include situations where both structures are movable or both structures are fixed.

[0107] In the drawings, similar elements and / or features may have the same reference numerals. Various elements of the same type may be distinguished by adding letters or numbers after the reference numerals to distinguish similar elements and / or similar features.

[0108] Figure 1 A circuit diagram of a power conversion circuit according to an embodiment of the present invention is shown. Figure 1 As shown, power conversion circuit 100 includes a transformer TM, a resonant capacitor CR, a high-bridge switch QH, a low-bridge switch QL, a current sense resistor RCS, an output capacitor CO, and a rectifier element DR. According to one embodiment of the present invention, power conversion circuit 100 can be an asymmetrical half-bridge flyback power converter.

[0109] The transformer TM includes a primary winding PS and a secondary winding SS. The primary winding PS is equivalent to a leakage inductance Lr and a magnetizing inductance Lm, which are connected in series. A resonant capacitor CR is coupled to one end of the primary winding PS.

[0110] Based on the high-bridge drive signal HS, the high-bridge switch QH magnetizes the primary winding PS of the transformer TM using the input voltage VIN and charges the resonant capacitor CR. Based on the low-bridge drive signal LS, the low-bridge switch QL demagnetizes the transformer TM and discharges the resonant capacitor CR.

[0111] According to one embodiment of the present invention, the high-bridge switch QH and the low-bridge switch QL form a half-bridge circuit to store and release energy in the transformer TM and the resonant capacitor CR. According to one embodiment of the present invention, the on-time of the high-bridge switch QH is equal to the magnetization time of the transformer TM. According to one embodiment of the present invention, the on-time of the low-bridge switch QL is equal to the demagnetization time of the transformer TM. In other words, the on-time of the low-bridge switch QL is not fixed.

[0112] The current sense resistor RCS is coupled between the resonant capacitor CR and ground and is used to detect the capacitance current IC of the resonant capacitor CS. According to one embodiment of the present invention, the current sense resistor RCS is used to detect the current flowing through the transformer TM and the resonant capacitor CR when the high-bridge switch QH is on, and to detect the discharge current of the resonant capacitor CR when the low-bridge switch QL is on, thereby generating a current sense voltage VCS. Furthermore, the current sense voltage VCS is also the voltage across the current sense resistor RCS. When the low-bridge switch QL is on, the transformer TM transfers the energy stored in the primary winding PS and the resonant capacitor CR to the secondary winding SS. The energy in the secondary winding SS is then used to charge the output capacitor CO via the rectifier element DR, generating the output voltage VO.

[0113] like Figure 1 As shown, the power conversion circuit 100 further includes a feedback circuit 110, a signal processing circuit 120, and a control circuit 130. The feedback circuit 110 is configured to generate a feedback signal SFB based on the output voltage VO. In other words, the feedback signal SFB is related to the output voltage VO. According to some embodiments of the present invention, the feedback circuit 110 includes an isolation element to isolate signals from the primary winding PS and the secondary winding SS of the transformer TM.

[0114] The signal processing circuit 120 generates a current detection signal SCS based on the current detection voltage VCS. In other words, the current detection signal SCS represents the current flowing through the primary winding PS. Based on the feedback signal SFB related to the output voltage VO and the current detection signal SCS representing the current flowing through the primary winding PS, the control circuit 130 generates a high-bridge drive signal HS and a low-bridge drive signal LS to drive the high-bridge switch QH and the low-bridge switch QL, respectively, thereby regulating the output voltage VO.

[0115] like Figure 1 As shown, the relationship between the output voltage VO and the input voltage VIN is shown in Formula 1, where the primary coil PS has a primary turn number Np, the secondary coil SS has a secondary turn number Ns, and the on-time of the high-bridge switch QH is t QH , the conduction time of the lower bridge switch QL is t QL .

[0116]

[0117]

[0118] When the power conversion circuit 100 operates in critical resonance mode (CRM), the output current IO of the power conversion circuit 100 is expressed as Equation 2, where ILm,max and ILm,min are the maximum and minimum values ​​of the magnetizing current ILm flowing through the magnetizing inductor Lm, respectively. According to one embodiment of the present invention, ILm,min can be a negative value.

[0119]

[0120] When the power conversion circuit 100 operates in a discontinuous current mode (DCM), the output current IO of the power conversion circuit 100 is expressed as Formula 3, where t S Represents the sum of the on-time of the high-bridge switch QH, the on-time of the low-bridge switch QL, and the time when both the high-bridge switch QH and the low-bridge switch QL are not conducting. The on-time of the high-bridge switch QH is t QH , the conduction time of the lower bridge switch QL is t QL .

[0121]

[0122] According to one embodiment of the present invention, when the feedback signal SFB is equal to the current detection signal SCS, the control circuit 130 does not turn on the high bridge switch QH. In other words, the feedback signal SFB can be regarded as equal to the maximum value of the current flowing through the magnetizing inductor Lm, which is used to approximate That is, the control circuit 130 can use the feedback signal SFB to know the size of the output current IO. Figure 1 As shown, the control circuit 130 generates a power signal SPWR based on the upper bridge driving signal HS and the feedback signal SFB, wherein the power signal SPWR is related to the output current IO.

[0123] Figure 2 A block diagram of a control circuit according to an embodiment of the present invention is shown. Figure 2 As shown, the control circuit 200 includes a buffer circuit 210 and a low-pass filter 220. The buffer circuit 210 includes an amplifier AMP, an OR gate OR, a first switch SW1, an inverter INV, and a second switch SW2. The amplifier AMP is used to increase the current driving capability of the feedback signal SFB. The OR gate OR is used to perform a logical OR operation on the high-bridge drive signal HS and the low-bridge drive signal LS, thereby turning on the first switch SW1. The inverter INV is used to invert the output of the OR gate OR, thereby turning on the second switch SW2.

[0124] According to one embodiment of the present invention, when the high-bridge switch QH or the low-bridge switch QL is turned on, the high-bridge drive signal HS or the low-bridge drive signal LS is in an enabled state, thereby turning on the first switch SW1 and providing the feedback signal SFB to the transmission signal SINT. According to another embodiment of the present invention, when both the high-bridge drive signal HS and the low-bridge drive signal LS are disabled, rendering the high-bridge switch QH or the low-bridge switch QL non-conductive, the second switch SW2 is turned on to discharge the transmission signal SINT.

[0125] like Figure 2 As shown, the low-pass filter 220 includes a low-pass resistor RLP and a low-pass capacitor CLP. The low-pass resistor RLP is coupled between the transmission signal SINT and the power signal SPWR, and the low-pass capacitor CLP is coupled between the power signal SPWR and ground. According to one embodiment of the present invention, the low-pass filter 220 is configured to average the feedback signal SFB to generate the power signal SPWR. According to some embodiments of the present invention, the power signal SPWR is proportional to the output current IO of the power conversion circuit 100.

[0126] Figure 3 A block diagram of a control circuit according to another embodiment of the present invention is shown. Figure 3 The control circuit 300 and Figure 2 Compared to control circuit 200, control circuit 300 further includes a third switch SW3 and a sampling capacitor CSAMP. Third switch SW3 is configured to capture the maximum value of current sense voltage VCS based on upper bridge drive signal HS and store it in sampling capacitor CSAMP. The maximum value of current sense voltage VCS stored in sampling capacitor CSAMP is then provided to buffer circuit 210.

[0127] According to one embodiment of the present invention, since the output current IO is related to the maximum value of the capacitor current IC (equivalent to the magnetizing current ILm) when the high-side switch is on, and the capacitor current IC is represented by the current sense voltage VCS, the maximum value of the captured current sense voltage VCS is equivalent to the maximum value of the captured capacitor current IC. In other words, the power signal SPWR generated by the control circuit 300 is proportional to the output current IO.

[0128] Figure 4 A block diagram of a control circuit according to another embodiment of the present invention is shown. Figure 4 The control circuit 400 and Figure 2 Compared to the control circuit 200, the control circuit 400 further includes a calculation circuit 410 and a fourth switch SW4. The calculation circuit 410 is configured to subtract the offset OFT from the feedback signal SFB to generate a correction signal CAL.

[0129] According to some embodiments of the present invention, since there is still an offset OFT between the feedback signal SFB and the maximum value of the current detection signal SCS, and the offset OFT is related to the input voltage VIN or a ramp signal, the operation of the operation circuit 410 can make the feedback signal SFB and the current detection signal SCS closer. According to some embodiments of the present invention, the offset OFT can be the input voltage VIN multiplied by a ratio. According to another embodiment of the present invention, the offset OFT can also be slope compensation. According to other embodiments of the present invention, the offset can be the sum of the input voltage VIN multiplied by a ratio and the slope compensation.

[0130] Next, the fourth switch SW4 provides the correction signal CAL to the buffer circuit 210 and the low-pass filter 220 based on the high-bridge driving signal HS (ie, the on-time of the high-bridge switch QH), thereby generating a power signal SPWR proportional to the output current IO.

[0131] Figure 5 A block diagram of a judgment circuit according to an embodiment of the present invention is shown. According to an embodiment of the present invention, Figure 1 The control circuit 130 further includes a judgment circuit 500. Figure 5 As shown, the determination circuit 500 includes a comparator CMP and a delay circuit 510. The comparator CMP is configured to compare the power signal SPWR with a threshold value TH to generate a comparison result CRT. According to one embodiment of the present invention, when the power signal SPWR exceeds the threshold value TH, the comparator CMP outputs an enabled comparison result CRT. According to another embodiment of the present invention, when the power signal SPWR does not exceed the threshold value TH, the comparator CMP outputs a disabled comparison result CRT.

[0132] When the comparison result CRT changes, the delay circuit 510 is configured to delay the comparison result CRT for a predetermined time before outputting it as the status signal ST. According to one embodiment of the present invention, when the status signal ST is enabled, it indicates that the power conversion circuit 100 is in an overcurrent state. The control circuit 130 can implement protective measures for the power conversion circuit 100 based on the enabled status signal ST. According to one embodiment of the present invention, the control circuit 130 reduces the output current IO by controlling the high-bridge switch QH and the low-bridge switch QL based on the enabled status signal ST.

[0133] like Figure 5 As shown, the delay circuit 510 further receives a power-on reset signal POR. For example, when Figure 1 When the input voltage VIN gradually rises from 0V to a certain potential, the power-on reset signal POR generates a pulse to reset the state signal ST of the delay circuit 510.

[0134] Figure 6 A block diagram of a control circuit according to another embodiment of the present invention is shown. According to one embodiment of the present invention, the control circuit 600 corresponds to Figure 1 The control circuit 130. Figure 6 As shown, the control circuit 600 further includes a first voltage-dividing resistor RD1, a second voltage-dividing resistor RD2, and a first transistor Q1. The first voltage-dividing resistor RD1 and the second voltage-dividing resistor RD2 are used to divide the power signal SPWR to generate a divided voltage VD. When the divided voltage VD turns on the first transistor Q1 as the power signal SPWR increases, the first transistor Q1 pulls down the feedback signal SFB.

[0135] According to one embodiment of the present invention, when the current sense signal SCS exceeds the feedback signal SFB, the control circuit 600 turns off the high-side switch QH. In other words, when the power signal SPWR increases and pulls the feedback signal SFB low, the on-time of the high-side switch QH decreases, thereby reducing the output current I0. On the other hand, when the power signal SPWR increases and pulls the feedback signal SFB low, the on-time of the high-side switch QH is reduced, thereby achieving a constant output current I0 flowing through the secondary winding SS of the transformer TM.

[0136] Figure 7 A schematic diagram showing a power system according to an embodiment of the present invention is shown. Figure 7 As shown, the power system 700 includes a power factor correction circuit 710 and a power conversion circuit 720. According to an embodiment of the present invention, the power conversion circuit 720 corresponds to Figure 1 A power conversion circuit 100 is provided.

[0137] like Figure 7 As shown, the power factor correction circuit 710 is configured to convert the AC input voltage VIN_AC into an input voltage VIN. Furthermore, the input voltage VIN is divided by a third voltage-dividing resistor RD3 and a fourth voltage-dividing resistor RD4 to generate a power factor feedback voltage VFB_PFC. The power factor correction circuit 710 further adjusts the voltage level of the input voltage VIN based on the power factor feedback voltage VFB_PFC. According to one embodiment of the present invention, when the power factor feedback voltage VFB_PFC decreases, the power factor correction circuit 710 increases the voltage level of the input voltage VIN.

[0138] The power conversion circuit 720 is used to convert the input voltage VIN into the output voltage VO and generate a state signal ST and a power signal SPWR. According to some embodiments of the present invention, the state signal ST corresponds to Figure 5 The status signal ST and the power signal SPWR correspond to Figure 2 、 Figure 3、 Figure 4 、 Figure 5 、 Figure 6 The power signal is not repeated here.

[0139] According to one embodiment of the present invention, when the power signal SPWR turns on the second transistor Q2, the second transistor Q2 and the pull-down resistor RPD are used to pull down the power factor feedback voltage VFB_PFC, allowing the power factor correction circuit 710 to further increase the input voltage VIN. When the power signal SPWR turns on the second transistor Q2, it indicates that the power conversion circuit 720 is generating a large output power. The power factor correction circuit 710 increases the input voltage VIN, which helps improve the conversion efficiency of the power conversion circuit 720.

[0140] According to an embodiment of the present invention, when the power signal SPWR is lower than the threshold value TH, the state signal ST (eg, Figure 5 As shown), the disabled state signal ST serves as the enable signal EN of the power factor correction circuit 710 to disable the power factor correction circuit 710, thereby increasing the conversion efficiency of the power system 700 under light load conditions.

[0141] According to another embodiment of the present invention, when the power signal SPWR is not lower than the threshold value TH, the state signal ST is enabled (eg, Figure 5 As shown), the enabled status signal ST serves as the enable signal EN of the power factor correction circuit 710 to enable the power factor correction circuit 710. Even a higher power signal SPWR can further prompt the power factor correction circuit 710 to increase the input voltage VIN and increase the conversion efficiency of the power system 700.

[0142] Figure 8 A flow chart showing a control method according to an embodiment of the present invention is shown. According to some embodiments of the present invention, Figure 8 The control method 800 is used to control Figure 1 The following description of the control method 800 will be combined with the power conversion circuit 100. Figure 1 The power conversion circuit 100 is shown in FIG.

[0143] First, the control circuit 130 turns on the high-bridge switch QH and the low-bridge switch QL, respectively, based on the feedback signal SFB and the current detection signal SCS, to regulate the output voltage VO (step S810). Next, the control circuit 130 generates a power signal SPWR related to the output current IO of the power conversion circuit 100 based on the state of the high-bridge switch QH and the feedback signal SFB (step S820). According to one embodiment of the present invention, the control circuit 130 generates the power signal SPWR based on the on-time of the high-bridge switch QH and the feedback signal SFB.

[0144] The present invention proposes a power conversion circuit and a control method thereof that can directly obtain output power information without isolation, and protects the power conversion circuit through power information, and even uses the power information to control the power factor correction circuit of the previous stage, thereby increasing the overall conversion efficiency of the power system.

[0145] Although the embodiments of the present disclosure and their advantages have been disclosed as above, it should be understood that any person skilled in the art may make changes, substitutions and modifications without departing from the spirit and scope of the present disclosure. In addition, the scope of protection of the present disclosure is not limited to the processes, machines, manufacturing, material compositions, devices, methods and steps in the specific embodiments described in the specification. Any person skilled in the art can understand from the disclosure of some embodiments of the present disclosure that the processes, machines, manufacturing, material compositions, devices, methods and steps currently or in the future are developed. As long as they can implement substantially the same functions or obtain substantially the same results in the embodiments described herein, they can be used according to some embodiments of the present disclosure. Therefore, the scope of protection of the present disclosure includes the above-mentioned processes, machines, manufacturing, material compositions, devices, methods and steps. In addition, each claim constitutes a separate embodiment, and the scope of protection of the present disclosure also includes the combination of each claim and embodiment.

Claims

1. A power conversion circuit, characterized in that: include: a transformer comprising a primary coil and a secondary coil, wherein the secondary coil generates an output voltage of the power conversion circuit; an upper bridge switch and a lower bridge switch coupled to the primary coil and functioning as a half-bridge circuit to magnetize and demagnetize the transformer; and a control circuit, based on a feedback signal and a current detection signal, turning on the upper bridge switch and the lower bridge switch respectively to adjust the output voltage; wherein the feedback signal is related to the output voltage, and the current detection signal represents the current flowing through the primary coil; The control circuit further generates a power signal related to an output current of the power conversion circuit based on the state of the upper bridge switch and the feedback signal.

2. The power conversion circuit according to claim 1, wherein: The control circuit generates the power signal based on the on-time of the upper bridge switch, the on-time of the lower bridge switch, and the feedback signal.

3. The power conversion circuit according to claim 2, wherein: The time for the transformer to be magnetized is equal to the conduction time of the upper bridge switch; The demagnetization time of the transformer is equal to the conduction time of the lower bridge switch.

4. The power conversion circuit according to claim 1, wherein: The control circuit generates the power signal based on an average of the feedback signals.

5. The power conversion circuit according to claim 4, wherein: The control circuit includes a low-pass filter, wherein the low-pass filter is used to average the feedback signal to generate the power signal.

6. The power conversion circuit according to claim 1, wherein: When the power signal exceeds a threshold value, the control circuit drives the upper bridge switch and the lower bridge switch to reduce the output current.

7. The power conversion circuit according to claim 1, wherein: When the power signal exceeds a threshold value, the control circuit drives the upper bridge switch and the lower bridge switch, so that the output current flowing through the secondary coil is a constant current.

8. The power conversion circuit according to claim 1, wherein: A power factor correction circuit is used to convert an AC voltage into an input voltage, wherein the power conversion circuit is used to convert the input voltage into the output voltage.

9. The power conversion circuit according to claim 8, wherein: When the power signal exceeds a threshold value, the power factor correction circuit increases the voltage value of the input voltage based on the power signal.

10. The power conversion circuit according to claim 8, wherein: When the power signal does not exceed a threshold value, the control circuit disables the power factor correction circuit; When the power signal exceeds the threshold value, the control circuit enables the power factor correction circuit.

11. A control method, characterized in that: The method is used to control a power conversion circuit, wherein the power conversion circuit includes a transformer and a half-bridge circuit, wherein the transformer includes a primary coil and a secondary coil, wherein the half-bridge circuit includes an upper bridge switch and a lower bridge switch, respectively used to magnetize and demagnetize the primary coil, so that the secondary coil generates an output voltage of the power conversion circuit, wherein the control method includes: Based on a feedback signal and a current detection signal, turning on the upper bridge switch and the lower bridge switch respectively to adjust the output voltage; and generating a power signal related to an output current of the power conversion circuit based on the state of the upper bridge switch and the feedback signal; The feedback signal is related to the output voltage, and the current detection signal represents the current flowing through the primary coil.

12. The control method according to claim 11, wherein: The step of generating the power signal related to the output current of the power conversion circuit based on the state of the upper bridge switch and the feedback signal further includes: The power signal is generated based on the on-time of the upper bridge switch, the on-time of the lower bridge switch, and the feedback signal.

13. The control method according to claim 12, wherein: The time for the transformer to be magnetized is equal to the conduction time of the upper bridge switch; The demagnetization time of the transformer is equal to the conduction time of the lower bridge switch.

14. The control method according to claim 11, wherein: The step of generating the power signal related to the output current of the power conversion circuit based on the state of the upper bridge switch and the feedback signal further includes: The power signal is generated based on an average of the feedback signals.

15. The control method according to claim 14, wherein: The step of generating the power signal based on the average of the feedback signal further includes: A low-pass filter is used to average the feedback signal to generate the power signal.

16. The control method according to claim 11, wherein: Also includes: When the power signal exceeds a threshold value, the upper bridge switch and the lower bridge switch are driven to reduce the output current.

17. The control method according to claim 11, wherein: Also includes: When the power signal exceeds a threshold value, the upper bridge switch and the lower bridge switch are driven, so that the output current flowing through the secondary coil is a constant current.

18. The control method according to claim 11, wherein: A power factor correction circuit is used to convert an AC voltage into an input voltage, wherein the power conversion circuit is used to convert the input voltage into the output voltage.

19. The control method according to claim 18, wherein: Also includes: When the power signal exceeds a threshold value, the power factor correction circuit is controlled to increase the voltage value of the input voltage.

20. The control method according to claim 18, wherein: Also includes: disabling the power factor correction circuit when the power signal does not exceed a threshold value; and When the power signal exceeds the threshold value, the power factor correction circuit is enabled.

Images