A control circuit, a flyback circuit and a charger

Abstract

The present application relates to the technical field of electronic circuit, disclose a kind of control circuit, flyback circuit and charger.Control circuit is applied to flyback circuit, control circuit includes feedback control circuit, isolated transmission circuit and primary side control circuit, feedback control circuit is based on at least one of the direct current component of the output voltage signal of the secondary side of flyback circuit or the direct current component of output current signal, and the current ripple signal of the transformer of flyback circuit, generates secondary side control signal, secondary side control signal can be used as the turn-off control signal of secondary side rectifier tube, after isolated transmission circuit, it can also be used as the conduction control signal of primary side switch tube.Therefore, because secondary side control signal dominates the switching frequency of primary side switch tube, so that the primary side can respond to the output change of secondary side in time, and control primary side switch tube conduction and secondary side rectifier tube turn-off are based on secondary side control signal, can guarantee that both will not be turned on simultaneously.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and in particular to a control circuit, a flyback circuit, and a charger. Background Technology

[0002] A flyback circuit is a power supply circuit that converts alternating current (AC) into direct current (DC) and can step up or step down the voltage. Due to its advantages such as high efficiency, small size, and light weight, it is widely used in the charging field. For example, a charger that includes this flyback circuit can use the DC power obtained after AC / DC conversion to charge various electronic devices or rechargeable batteries.

[0003] When flyback circuits are used in chargers, in order to facilitate the adjustment of output power, the conventional approach is to add a feedback circuit to sense changes in output voltage or output current, and use the signal that indicates the change to adjust the output power.

[0004] like Figure 1 As shown, Figure 1 This is a schematic diagram of a flyback circuit. (Example) Figure 1 As shown, the flyback circuit includes a primary-side controller, a secondary-side controller, a transformer T, a primary-side switch Q1, a secondary-side switch Q2, an optocoupler OC, and an output capacitor Co.

[0005] The primary-side controller controls the on / off state of the primary-side switch Q1 to regulate the output power. The secondary-side controller controls the on / off state of the secondary-side rectifier Q2 to achieve synchronous rectification. When the primary-side switch Q1 is on and the secondary-side rectifier Q2 is off, the primary winding Np of the transformer T is directly coupled to the input power supply VIN. The current in the primary winding Np gradually increases, and the primary winding Np stores energy. At the same time, the output capacitor Co supplies power to the load using the previously stored energy. When the primary-side switch Q1 is off and the secondary-side rectifier Q2 is on, the energy stored in the primary winding Np begins to be transferred to the secondary winding Ns. Current flows from the secondary winding Ns, and the output capacitor Co is charged to store energy.

[0006] The optocoupler OC acts as a feedback circuit to sense output signals such as output voltage on the secondary side and generate auxiliary control signals on the primary side to assist the primary side controller in controlling the primary side switch Q1, thereby obtaining the desired output voltage level or output current level on the secondary side.

[0007] However, the auxiliary control signal generated by the optocoupler OC does not reflect the actual output voltage or output current. In other words, it does not directly extract the real-time changing load voltage or load current from the load side. Therefore, there will inevitably be a delay effect in the feedback process. This will prevent the primary side from responding quickly and timely to the constantly changing output voltage or output current of the secondary side. This lag will prevent the primary side controller from keeping synchronized with the output voltage or output current to control the primary side switch Q1 in real time. This will cause a certain deviation between the current output voltage or output current output to the load and the actual voltage or current required by the load, thus bringing instability to the output voltage or output current. Meanwhile, since the control of the primary-side switch Q1 by the primary-side controller and the control of the secondary-side rectifier Q2 by the secondary-side controller are relatively independent, in continuous conduction mode (CCM), this lag will cause the primary-side switch Q1 to be turned on before the secondary-side rectifier Q2 is turned off. In other words, there is a situation where the primary-side switch Q1 and the secondary-side rectifier Q2 are turned on at the same time. This will cause the primary-side switch Q1 to be subjected to a very large transient input surge current. The continuous transient input surge current will reduce the reliability of circuit components such as the primary-side switch Q1, and in severe cases, it will burn out these circuit components.

[0008] Therefore, the flyback circuits in the related technologies that can adjust the output power in a feedback manner have the disadvantage that the primary side cannot respond to the output changes of the secondary side in a timely manner or that the primary side switching transistor and the secondary side rectifier transistor are simultaneously turned on. Therefore, it is necessary to improve the flyback circuits in the related technologies. Summary of the Invention

[0009] To address the aforementioned technical problems, embodiments of the present invention provide a control circuit, a flyback circuit, and a charger, which can solve the technical problems in the prior art where the primary-side controller cannot respond promptly to changes in the secondary-side output when controlling the primary-side switching transistor, and where the primary-side switching transistor and the secondary-side rectifier transistor are simultaneously turned on due to the relative independence of the control.

[0010] The present invention provides the following technical solutions to solve the above-mentioned technical problems:

[0011] In a first aspect, embodiments of the present invention provide a control circuit applied to a flyback circuit, the flyback circuit including a primary-side switch, a secondary-side rectifier, and a transformer for isolating current. The control circuit includes: a feedback control circuit configured to generate a secondary-side control signal based on at least one of a DC component of an output voltage signal or a DC component of an output current signal from the secondary side of the flyback circuit, and a current ripple signal from the transformer, the secondary-side control signal being used to control the secondary-side rectifier to turn off; an isolation transmission circuit connected to the feedback control circuit, configured to generate a first primary-side control signal based on the secondary-side control signal; and a primary-side control circuit connected to the isolation transmission circuit, configured to control the primary-side switch to turn on when receiving the first primary-side control signal of a first mode from the isolation transmission circuit.

[0012] Optionally, the primary-side control circuit is further configured to simultaneously receive the first primary-side control signal and the second primary-side control signal, and control the primary-side switching transistor to turn on and off based on the first primary-side control signal and the second primary-side control signal.

[0013] Optionally, the second primary-side control signal is generated based on a primary-side current detection signal that indicates the current flowing through the primary winding of the transformer.

[0014] Optionally, the primary-side control circuit includes a first comparator, which includes a first input terminal, a second input terminal, and an output terminal. The first input terminal of the first comparator is used to receive the primary-side current detection signal, the second input terminal of the first comparator is applied with a first reference voltage, and the output terminal of the first comparator outputs a second primary-side control signal based on the primary-side current detection signal and the first reference voltage.

[0015] Optionally, the primary-side control circuit includes a logic driving circuit, which includes a first input terminal, a second input terminal, and an output terminal. The first input terminal of the logic driving circuit receives a first primary-side control signal, and the second input terminal receives a second primary-side control signal. The output terminal of the logic driving circuit is connected to the primary-side switching transistor. The logic driving circuit outputs a primary-side driving signal based on the first and second primary-side control signals to control the on and off states of the primary-side switching transistor.

[0016] Optionally, the logic driving circuit includes an RS flip-flop, which includes a set input, a reset input, and an output. The set input of the RS flip-flop is the first input of the logic driving circuit, the reset input of the RS flip-flop is the second input of the logic driving circuit, and the output of the RS flip-flop is the output of the logic driving circuit.

[0017] Optionally, the logic driving circuit further includes a driver, which includes an input terminal and an output terminal; the input terminal of the driver is connected to the output terminal of the RS flip-flop, and the output terminal of the driver is connected to the primary-side switching transistor.

[0018] Optionally, a secondary-side controller is also included. The secondary-side controller is connected to both the feedback control circuit and the secondary-side rectifier. When the secondary-side controller receives a secondary-side control signal from the first mode of the feedback control circuit, it controls the secondary-side rectifier to turn off.

[0019] Optionally, the feedback control circuit includes at least one of a first feedback control circuit and a second feedback control circuit, wherein the secondary-side control signal is generated by the first feedback control circuit based on the DC component of the output voltage signal and the current ripple signal of the transformer, and / or is generated by the second feedback control circuit based on the DC component of the output current signal and the current ripple signal of the transformer.

[0020] Optionally, the first feedback control circuit includes a first compensation circuit and a second comparator; the first compensation circuit includes a first input terminal, a second input terminal, and an output terminal, and the second comparator includes a first input terminal, a second input terminal, and an output terminal; the first input terminal of the first compensation circuit is used to receive the DC component of the output voltage signal and the current ripple signal of the transformer; the second input terminal of the first compensation circuit is used to receive a second reference voltage; the output terminal of the first compensation circuit is connected to the first input terminal of the second comparator; the second input terminal of the second comparator is used to receive a third reference voltage; and the output terminal of the second comparator is connected to the secondary rectifier and the isolation transmission circuit, respectively.

[0021] Optionally, the first compensation circuit includes a first operational amplifier, a first resistor, and a first capacitor; the non-inverting input of the operational amplifier is the first input of the first compensation circuit, the inverting input of the operational amplifier is the second input of the first compensation circuit, and the output of the operational amplifier is the output of the first compensation circuit; the first resistor and the first capacitor are connected in series, one end of the series connection is connected to the output of the first operational amplifier and the first input of the second comparator, and the other end of the series connection is grounded.

[0022] Optionally, the first feedback control circuit further includes a first preprocessing circuit, which is connected to the positive terminal of the output voltage and the non-inverting input terminal of the first operational amplifier, respectively.

[0023] Optionally, the first preprocessing circuit includes a second resistor, a third resistor, a fourth resistor, and a second capacitor; one end of the second resistor and one end of the second capacitor are connected to the positive terminal of the output voltage, the other end of the second capacitor and one end of the third resistor are connected together to the non-inverting input terminal of the first operational amplifier, the other end of the third resistor, the other end of the second resistor and one end of the fourth resistor are connected together, and the other end of the fourth resistor is grounded.

[0024] Optionally, the second feedback control circuit includes a second compensation circuit and a third comparator; the second compensation circuit includes a first input terminal, a second input terminal, and an output terminal; the third comparator includes a first input terminal, a second input terminal, and an output terminal; the first input terminal of the second compensation circuit is used to receive the DC component of the output current and the current ripple signal of the transformer; the second input terminal of the second compensation circuit is used to receive a fourth reference voltage; the output terminal of the second compensation circuit is connected to the first input terminal of the third comparator; the second input terminal of the third comparator is used to receive a fifth reference voltage; and the output terminal of the third comparator is connected to the secondary rectifier and the isolation transmission circuit respectively.

[0025] Optionally, the second compensation circuit includes a second operational amplifier, a fifth resistor, and a third capacitor; the non-inverting input of the second operational amplifier is the first input of the second compensation circuit, the inverting input of the second operational amplifier is the second input of the second compensation circuit, and the output of the second operational amplifier is the output of the second compensation circuit; the fifth resistor and the third capacitor are connected in series, one end of which is connected to the output of the second operational amplifier and the first input of the third comparator, and the other end of which is grounded.

[0026] Optionally, the second feedback control circuit further includes a second preprocessing circuit, which is connected to the positive terminal of the output voltage and the non-inverting input terminal of the second operational amplifier, respectively.

[0027] Optionally, the second preprocessing circuit includes an amplifier circuit, a sixth resistor, and a fourth capacitor; the amplifier circuit includes a first input terminal, a second input terminal, and an output terminal; the first input terminal of the amplifier circuit receives the DC component of the output current signal, the second input terminal of the amplifier circuit is grounded, the output terminal of the amplifier circuit is connected to one end of the sixth resistor, the other end of the sixth resistor and one end of the fourth capacitor are connected to the non-inverting input terminal of the second operational amplifier, and the other end of the fourth capacitor is used to connect to the positive terminal of the output voltage.

[0028] Optionally, the isolated transmission circuit includes a transmitter, an isolation device, and a receiver; the transmitter includes an input terminal and an output terminal, the isolation device includes an input terminal and an output terminal, and the receiver includes an input terminal and an output terminal; the input terminal of the transmitter is connected to the feedback control circuit, the output terminal of the transmitter is connected to the input terminal of the isolation device, the output terminal of the isolation device is connected to the input terminal of the receiver, and the output terminal of the receiver is connected to the primary-side control circuit.

[0029] Optionally, the isolation device includes one or more of capacitors, magnetic elements, and optocouplers.

[0030] In a second aspect, embodiments of the present invention provide a flyback circuit, including a primary-side switching transistor, a transformer for isolating current, a secondary-side rectifier transistor, and a control circuit as described above.

[0031] Optionally, it also includes a ripple feedforward circuit, which is connected in parallel between the two ends of the secondary winding of the transformer.

[0032] Optionally, the ripple feedforward circuit includes a seventh resistor and a fifth capacitor. One end of the seventh resistor is connected to one end of the secondary winding of the transformer, and the other end of the seventh resistor is connected to one end of the fifth capacitor. The other end of the fifth capacitor is connected to the other end of the secondary winding of the transformer.

[0033] In a third aspect, embodiments of the present invention provide a charger including the flyback circuit described above.

[0034] The beneficial effects of this invention are: it provides a control circuit, a flyback circuit, and a charger. The control circuit is applied to the flyback circuit and includes a feedback control circuit, an isolation transmission circuit, and a primary-side control circuit. The feedback control circuit generates a secondary-side control signal based on at least one of the DC component of the output voltage signal or the DC component of the output current signal on the secondary side of the flyback circuit, and the current ripple signal of the transformer in the flyback circuit. The secondary-side control signal can be used as the turn-off control signal for the secondary-side rectifier diode, and after passing through the isolation transmission circuit, it can also be used as the turn-on control signal for the primary-side switch diode. Therefore, since the secondary-side control signal dominates the switching frequency of the primary-side switch diode, the primary side can respond promptly to changes in the output of the secondary side. Furthermore, since both the turn-on of the primary-side switch diode and the turn-off of the secondary-side rectifier diode are based on the secondary-side control signal, it can be ensured that the two will not be turned on simultaneously. Attached Figure Description

[0035] One or more embodiments are illustrated by way of example only, and these illustrative examples do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements, and unless otherwise stated, the figures in the drawings do not constitute a limitation on scale.

[0036] Figure 1 This is a schematic diagram of a flyback circuit.

[0037] Figure 2 This is a schematic diagram of a flyback circuit provided in an embodiment of the present invention;

[0038] Figure 3 yes Figure 2 A schematic diagram of the control circuit structure;

[0039] Figure 4 yes Figure 3 A schematic diagram of the working waveforms of a control circuit.

[0040] Figure 5 This is a schematic diagram of another control circuit provided in an embodiment of the present invention;

[0041] Figure 6 yes Figure 5 A schematic diagram of a feedback control circuit is provided.

[0042] Figure 7 yes Figure 6 The diagram above provides a schematic of the working waveform of a feedback control circuit.

[0043] Figure 8 yes Figure 5 The diagram below shows another feedback control circuit.

[0044] Figure 9 yes Figure 5 The diagram provides another structural schematic of a feedback control circuit;

[0045] Figure 10 yes Figure 5 A schematic diagram of an isolated transmission circuit is provided.

[0046] Figure 11 yes Figure 5 A schematic diagram of a primary-side control circuit is provided.

[0047] Figure 12 This is a schematic diagram of another flyback circuit provided in an embodiment of the present invention;

[0048] Figure 13 yes Figure 12 The diagram above provides a schematic diagram of the principle waveform of a ripple feedforward circuit. Detailed Implementation

[0049] To facilitate understanding of this application, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as "connected" to another element, it can be directly connected to the other element, or there may be one or more intervening elements. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0050] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0051] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0052] This invention provides a flyback circuit, such as... Figure 2 As shown, the flyback circuit 100 includes a control circuit 10, a primary-side switch Q1, a secondary-side rectifier Q2, a transformer T for current isolation, and an output capacitor Co. The flyback circuit 100 receives the input voltage VIN and outputs the resulting output voltage Vo to the load.

[0053] The control circuit 10 is connected to the primary-side switch Q1 and the secondary-side rectifier Q2 respectively to control the primary-side switch Q1 and the secondary-side rectifier Q2. One end of the primary winding Np of the transformer T is used to couple the input power supply VIN. The other end of the primary winding Np of the transformer T is grounded through the primary-side switch Q1. The output capacitor Co is connected in parallel between the positive and negative terminals of the output voltage. One end of the secondary winding Ns of the transformer T is connected to one end of the output capacitor Co through the secondary-side rectifier Q2. The other end of the secondary winding Ns of the transformer T is connected to the other end of the output capacitor Co.

[0054] Specifically, such as Figure 2 As shown, the primary-side switch Q1 is an NMOS transistor (it can actually be any other type of switch), its drain is connected to one end of the primary winding Np of transformer T, its source is grounded, and its gate is connected to control circuit 10. The secondary-side rectifier Q2 is an NMOS transistor (it can actually be any other type of switch), its drain is connected to one end of the secondary winding Ns of transformer T, its source is grounded, and its gate is connected to control circuit 10.

[0055] The control circuit 10 acquires the output signal from the secondary side in real time and generates a secondary side control signal based on the output signal. The secondary side control signal serves as the turn-off control signal for the secondary side rectifier Q2 and the turn-on control signal for the primary side switch Q1. Through this feedback control method, the output voltage or output current can be adaptively adjusted in real time to obtain the expected and stable output voltage or output current. In applications where the magnitude of the output voltage or output current needs to be switched, it can obtain a precise output voltage or output current.

[0056] Furthermore, during the transmission of the secondary-side control signal, the secondary-side rectifier Q2 is turned off first, and then the primary-side switch Q1 is turned on. Therefore, even under CCM (Continuous Computational Mode), the secondary-side rectifier Q2 and the primary-side switch Q1 will not be turned on simultaneously. Simultaneously, the conduction of the primary-side switch Q1 is directly controlled by the secondary-side control signal, which dominates the switching frequency of the primary-side switch Q1. This enables the primary side to respond quickly and promptly to changes in output voltage, output current, or abnormal output conditions, thus improving the reliability and stability of the entire flyback circuit.

[0057] Specifically, such as Figure 3 As shown, the control circuit 10 includes a feedback control circuit 11, an isolation transmission circuit 12, and a primary-side control circuit 13.

[0058] The feedback control circuit 11 generates a secondary-side control signal based on at least one of the DC component of the output voltage signal or the DC component of the output current signal of the secondary side of the flyback circuit 100, and the current ripple signal of the transformer T. The secondary-side control signal can be used as a turn-off control signal to turn off the secondary-side rectifier Q2.

[0059] In one scenario, when the DC component of the output voltage signal and the current ripple signal of the transformer T meet the preset conditions, the feedback control circuit 11 outputs a turn-off control signal to control the secondary rectifier Q2 to turn off. When the DC component of the output voltage signal and the current ripple signal of the transformer T do not meet the preset conditions, the feedback control circuit 11 does not output a turn-off control signal.

[0060] In another scenario, when the DC component of the output current signal and the current ripple signal of the transformer T meet the preset conditions, the feedback control circuit 11 outputs a turn-off control signal to control the secondary rectifier Q2 to turn off. When the DC component of the output current signal and the current ripple signal of the transformer T do not meet the preset conditions, the feedback control circuit 11 does not output a turn-off control signal.

[0061] The secondary-side control signal has a first mode and a second mode. The first mode and the second mode can be regarded as two different level signals, such as a high-level signal and a low-level signal. The turn-off control signal can be the secondary-side control signal of the first mode (e.g., a high-level signal) or the secondary-side control signal of the second mode (e.g., a low-level signal). In this embodiment, the secondary-side control signal of the first mode is used as the turn-off control signal of the secondary-side rectifier Q2.

[0062] The isolation transmission circuit 12 is connected to the feedback control circuit 11, and it generates a first primary-side control signal based on the secondary-side control signal. The isolation transmission circuit 12 is used to transmit the secondary-side control signal to the primary side in a timely manner to form a first primary-side control signal. The waveform of the first primary-side control signal changes with the waveform of the secondary-side control signal, and there is a certain transmission delay time between the two. For example, when the secondary-side control signal changes from the first mode to the second mode, after the transmission delay time, the first primary-side control signal changes from the first mode to the second mode. The first primary-side control signal in the first mode and the second mode can also be regarded as two different level signals, such as a high-level signal and a low-level signal.

[0063] The primary-side control circuit 13 is connected to the isolation transmission circuit 12. When it receives a first primary-side control signal of the first mode from the isolation transmission circuit 12, it controls the primary-side switch Q1 to turn on. For example, when the first primary-side control signal of the first mode is high, the primary-side control circuit 13 controls the primary-side switch Q1 to turn on according to the high-level signal.

[0064] like Figure 4 As shown, at time T1, the secondary-side control signal Q2_Ctrl changes from a low level to a high level, and the secondary-side rectifier Q2 is immediately turned off. After a propagation delay time Td, at time T2, the primary-side control signal also changes from a low level to a high level, and the primary-side switch Q1 is immediately turned on. Since the primary-side switch Q1 always turns on after the secondary-side rectifier Q2 is turned off, even under CCM, the primary-side switch Q1 and the secondary-side rectifier Q2 will not be simultaneously turned on.

[0065] Furthermore, since the feedback control circuit 11 responds to changes in the secondary side output voltage or output current and generates a secondary side control signal accordingly, the secondary side control signal has an almost transient response to changes in the output voltage or output current. The first primary side control signal also responds to changes in the secondary side control signal in real time. Therefore, the first primary side control signal is equivalent to tracking changes in the output voltage or output current in real time, so as to switch the primary side switching transistor Q1 in a timely manner.

[0066] like Figure 5 As shown, the flyback circuit 100 also includes a secondary-side controller 14, which is connected to the feedback control circuit 11 and the secondary-side rectifier Q2. When the secondary-side controller 14 receives a secondary-side control signal (e.g., a high-level signal) from the feedback control circuit 11 in the first mode, it controls the secondary-side rectifier Q2 to turn off.

[0067] In the process of generating secondary-side control signals based on the DC component of the output voltage signal and the current ripple signal of the transformer T, the feedback control circuit 11, such as... Figure 6 As shown, the secondary-side control signal is generated by the first feedback control circuit 111 based on the DC component of the output voltage and the current ripple signal of the transformer T.

[0068] The first feedback control circuit 111 is for output ripple control to reduce DC error.

[0069] Specifically, the first feedback control circuit 111 includes a first preprocessing circuit 1111, a first compensation circuit 1112, and a comparator 1113.

[0070] The first preprocessing circuit 1111 is used to acquire the DC component of the output current and the current ripple signal of the transformer T. The first compensation circuit 1112 and the comparator 1113 are used to process these signals to obtain a pulse-shaped secondary side control signal.

[0071] The first compensation circuit 1112 includes a first operational amplifier A1, a first resistor R1 and a first capacitor C1, and the first preprocessing circuit 1111 includes a second resistor R2, a third resistor R3, a fourth resistor R4 and a second capacitor C2.

[0072] One end of the second resistor R2 and one end of the second capacitor C2 are connected to the positive terminal Vo+ of the output voltage. The other end of the second capacitor C2 and one end of the third resistor R3 are connected to the non-inverting input terminal of the first operational amplifier A1. The other end of the third resistor R3, the other end of the second resistor R2 and one end of the fourth resistor R4 are connected together, and the other end of the fourth resistor R4 is grounded.

[0073] It is worth noting that the first preprocessing circuit 1111 can be constructed in other forms, and is not limited to being composed of the second resistor R2, the third resistor R3, the fourth resistor R4, and the second capacitor C2, as long as it can obtain the DC component of the output voltage signal and the current ripple signal of the transformer T and input the signal to the first compensation circuit 1112 for processing. Furthermore, the first compensation circuit 1112 and the comparator 1113 can also be constructed in other forms, as long as they can obtain a pulse-form secondary-side control signal based on the DC component of the output voltage signal and the current ripple signal of the transformer T.

[0074] The inverting input of the first operational amplifier A1 is supplied with a reference voltage Vr1. The output of the first operational amplifier A1 is connected to the first input (e.g., the inverting input) of the comparator 1113. The first resistor R1 and the first capacitor C1 are connected in series. One end of the series connection is connected to the output of the first operational amplifier A1, and the other end is grounded. The second input (e.g., the non-inverting input) of the comparator 1113 is supplied with a reference voltage Vr2. The output of the comparator 1113 is connected to the secondary rectifier Q2 and the isolation transmission circuit 12, respectively.

[0075] In constant voltage regulation mode, the output voltage signal is divided by the second resistor R2 and the fourth resistor R4 and fed forward by the second capacitor C2 and the third resistor R3. The DC component of the output voltage signal and the current ripple signal of the transformer T are obtained at the connection point of the second capacitor C2 and the third resistor R3 and then input to the non-inverting input of the first operational amplifier A1.

[0076] The first operational amplifier A1, the first resistor R1, and the first capacitor C1 constitute a second-order compensation circuit structure. The first capacitor C1 acts as an integrator to reduce DC error. The first resistor R1 can amplify the amplitude of the current ripple signal of the transformer T, which is beneficial for the comparator 1113 to generate digital signals. At the same time, the ripple control in the frequency response will eliminate the low-frequency pole formed by the output capacitor Co. Therefore, its frequency response is quite fast, and the second-order compensation circuit structure can be designed in the high-frequency range.

[0077] In this way, the secondary-side control signal output by comparator 1113 can respond instantly to changes in the output voltage. At the same time, the secondary-side control signal obtains the control signal for each switching cycle based on the current ripple signal of transformer T.

[0078] The following is combined with Figure 7 This embodiment will be described in detail. It is worth noting that, for ease of explanation, the transmission delay of the isolation transmission circuit 12 is ignored here.

[0079] like Figure 7 As shown, at time T6, the signal V2 output by the first operational amplifier A1 responds to the signal resulting from the superposition of the DC component of the output voltage and the current ripple signal of the transformer T (hereinafter referred to as voltage signal V1). When the signal V2 output by the first operational amplifier A1 is less than the reference voltage Vr1, the comparator 1113 outputs a high-level signal. The secondary-side controller uses this high-level signal as a turn-off control signal to immediately turn off the secondary-side rectifier Q2. Simultaneously, this high-level signal serves as a turn-on control signal for the primary-side switch Q1 to immediately turn on the primary-side switch Q1. The same applies at time T8, which will not be elaborated further here.

[0080] In the process of generating secondary-side control signals based on the DC component of the output current signal and the current ripple signal of transformer T, the feedback control circuit 11, such as... Figure 8 As shown, the secondary side control signal is generated by the second feedback control circuit 112 based on the DC component of the output current and the current ripple signal of the transformer T.

[0081] Specifically, the second feedback control circuit 112 includes a second preprocessing circuit 1121, a second compensation circuit 1122, and a comparator 1123.

[0082] The second preprocessing circuit 1121 is used to acquire the DC component of the output current and the current ripple signal of the transformer T. The second compensation circuit 1122 and the comparator 1123 are used to process these signals to obtain a pulse-shaped secondary side control signal.

[0083] The second compensation circuit 1122 includes a second operational amplifier A2, a fifth resistor R5 and a third capacitor C3, and the second preprocessing circuit 1121 includes an amplifier circuit Acs, a sixth resistor R6 and a fourth capacitor C4.

[0084] The amplifier circuit Acs is connected to one end of the sensing resistor Rcc, and the other end of the sensing resistor Rcc is grounded. Therefore, the voltage input to the first input terminal of the amplifier circuit Acs can indicate the DC component of the output current signal. The other end of the amplifier circuit Acs is grounded. The output terminal of the amplifier circuit Acs is connected to one end of the sixth resistor R6. The other end of the sixth resistor R6 and one end of the fourth resistor R4 are connected to the non-inverting input terminal of the second operational amplifier A2. The other end of the fourth capacitor C4 is connected to the positive terminal of the output voltage.

[0085] It is worth noting that the second preprocessing circuit 1121 can be constructed in other forms, and is not limited to consisting of the amplifier circuit Acs, the sixth resistor R6, and the fourth capacitor C4, as long as it can obtain the DC component of the output current signal and the current ripple signal of the transformer T and input the signal to the second compensation circuit 1122 for processing. Furthermore, the second compensation circuit 1122 and the comparator 1123 can also be constructed in other forms, as long as they can obtain a pulse-form secondary-side control signal based on the DC component of the output current signal and the current ripple signal of the transformer T.

[0086] The inverting input of the second operational amplifier A2 is supplied with a reference voltage Vr3. The output of the second operational amplifier A2 is connected to the first input (e.g., the inverting input) of the comparator 1123. The fifth resistor R5 and the third capacitor C3 are connected in series. One end of the series connection is connected to the output of the second operational amplifier A2, and the other end is grounded. The second input (e.g., the non-inverting input) of the comparator 1123 is supplied with a reference voltage Vr4. The output of the comparator 1123 is connected to the secondary rectifier Q2 and the isolation transmission circuit 12.

[0087] In constant current regulation mode, the voltage signal obtained after the output current passes through the sensing resistor Rcc is used as the DC component of the output current signal. The amplifier circuit Acs amplifies the DC component of the output current signal to a preset factor. At the same time, through the feedforward effect of the sixth resistor R6 and the fourth capacitor C4, the DC component of the output current signal and the current ripple signal of the transformer T are obtained at the connection point of the sixth resistor R6 and the fourth capacitor C4 and input to the non-inverting input terminal of the second operational amplifier A2.

[0088] The second operational amplifier A2, the fifth resistor R5, and the third capacitor C3 constitute a second-order compensation circuit structure. The third capacitor C3 acts as an integrator to reduce DC error. The fifth resistor R5 can amplify the amplitude of the current ripple signal of the transformer T, which is beneficial for the comparator 1123 to generate digital signals. At the same time, the ripple control in the frequency response will eliminate the low-frequency pole formed by the output capacitor Co. Therefore, its frequency response is quite fast, and the second-order compensation circuit structure can be designed in the high-frequency range.

[0089] In this way, the secondary-side control signal output by comparator 1123 can respond instantly to changes in the output current. At the same time, the secondary-side control signal obtains the control signal for each switching cycle based on the current ripple signal of transformer T.

[0090] Understandably, in order to enable the control circuit 10 to operate in both constant voltage and constant current regulation modes, the feedback control circuit 11 includes the aforementioned first feedback control circuit 111, second feedback control circuit 112, and logic processing circuit 113. The logic processing circuit 113 includes a first input terminal, a second input terminal, and an output terminal. The output terminal of the first feedback control circuit 111 is connected to the first input terminal of the logic processing circuit 113, the output terminal of the second feedback control circuit 112 is connected to the second input terminal of the logic processing circuit 113, and the output terminal of the logic processing circuit 113 is connected to the secondary-side switch Q2 and the isolation transmission circuit 12, respectively.

[0091] The logic processing circuit 113 can select the signal output by the first feedback control circuit 111 as the secondary side control signal, or select the signal output by the second feedback control circuit 112 as the secondary side control signal, or combine the signal output by the first feedback control circuit 111 and the signal output by the second feedback control circuit 112 to obtain the secondary side control signal.

[0092] In some embodiments, such as Figure 9 As shown, the logic processing circuit 113 is an AND gate logic circuit.

[0093] The isolation transmission circuit 12 enables the isolated transmission of secondary-side control signals to the primary-side controller 13. Specifically, as shown... Figure 10 As shown, the isolated transmission circuit 12 includes a transmitter 121, an isolation device 122, and a receiver 123.

[0094] The transmitter 121 includes an input terminal and an output terminal, the isolation device 122 includes an input terminal and an output terminal, and the receiver 123 includes an input terminal and an output terminal.

[0095] The input terminal of transmitter 121 is connected to feedback control circuit 11, the output terminal of transmitter 121 is connected to input terminal of isolation device 122, the output terminal of isolation device 122 is connected to input terminal of receiver 123, and the output terminal of receiver 123 is connected to primary side control circuit 13.

[0096] Isolation device 122 includes one or more of the following: capacitor, magnetic element, and optocoupler. For example... Figure 10 As shown, the isolation device 122 includes a capacitor, one end of which is connected to the output terminal of the transmitter 121, and the other end of which is connected to the input terminal of the receiver 123.

[0097] In order to enable the primary-side control circuit 13 to control the primary-side switch Q1 to turn on and off, the primary-side control circuit 13 is also configured to simultaneously receive a first primary-side control signal and a second primary-side control signal, and control the primary-side switch Q1 to turn on and off based on the first primary-side control signal and the second primary-side control signal.

[0098] In some embodiments, the second primary-side control signal is generated based on a primary-side current detection signal that indicates the current flowing through the primary winding Np of transformer T.

[0099] In the process of generating the second control signal, specifically, such as Figure 11 As shown, the primary-side control circuit 13 includes a comparator 131, which includes a first input terminal, a second input terminal, and an output terminal.

[0100] The sensing resistor Rcs is used to detect the current in the primary winding Np of transformer T, and a voltage indicating the current is obtained at one end of it. This voltage is used as the primary current detection signal CS. The first input terminal (e.g., the non-inverting input terminal) of comparator 131 is connected to one end of the sensing resistor Rcs to receive the primary current detection signal CS. The second input terminal (e.g., the inverting input terminal) of comparator 131 is given a reference voltage Vr5. Based on the comparison result between the primary current detection signal CS and the reference voltage Vr5, comparator 131 outputs a second primary-side control signal at its output terminal.

[0101] The primary-side control circuit 13 generates a primary-side drive signal based on the first primary-side control signal and the second primary-side control signal, to control the on and off of the primary-side switch Q1. Specifically, the primary-side control circuit 13 includes a logic drive circuit 132, which includes a first input terminal, a second input terminal, and an output terminal.

[0102] The first input terminal of the logic driver circuit 132 receives a first primary-side control signal, and the second input terminal receives a second primary-side control signal. The output terminal of the logic driver circuit 132 is connected to the primary-side switch Q1. Based on the first and second primary-side control signals, the logic driver circuit 132 outputs a primary-side drive signal to control the on / off state of the primary-side switch Q1. Specifically, when the first input terminal of the logic driver circuit 132 receives the first primary-side control signal of the first mode (e.g., a high-level signal), the logic driver circuit 132 immediately controls the primary-side switch Q1 to turn on.

[0103] like Figure 11 As shown, the logic drive circuit 132 includes an RS flip-flop 1321, which includes a set input S, a reset input R, and an output Q.

[0104] Specifically, the set input S of the RS flip-flop 1321 is the first input of the logic drive circuit 132, the reset input R of the RS flip-flop 1321 is the second input of the logic drive circuit 132, and the output of the RS flip-flop 1321 is the output of the logic drive circuit 132. It can be understood that the set input S of the RS flip-flop 1321 is input with a first primary-side control signal, and the reset input R of the RS flip-flop 1321 is input with a second primary-side control signal. The RS flip-flop 1321 performs logical operations on the first and second primary-side control signals and generates a primary-side drive signal, thereby controlling the on and off states of the primary-side switch Q1.

[0105] It can be understood that the first primary-side control signal from the isolation transmission circuit 12 is used to set the RS flip-flop 1321 so that the RS flip-flop 1321 outputs a primary-side drive signal that can control the primary-side switch Q1 to turn on. Since the first primary-side control signal comes directly from the secondary-side control signal, it is equivalent to the secondary-side control signal dominating the switching frequency of the primary-side switch Q1. The secondary-side control signal is also an instantaneous response to the output voltage or output current of the secondary side. Therefore, the primary side can react instantly to the changes in the output signal of the secondary side, which is beneficial to improving the working performance of the entire flyback circuit.

[0106] Furthermore, the second primary-side control signal input to the reset input terminal R of the RS flip-flop 1321 can be any suitable input control signal. For example, the second primary-side control signal can be generated by the aforementioned primary-side current detection signal. This signal serves as an energy limit to prevent the primary-side current flowing through the primary-side switch Q1 from becoming too large and burning out the primary-side switch Q1. When the primary-side current is too large, the primary-side switch Q1 can be turned off in time through this signal, thereby protecting the primary-side switch Q1.

[0107] To facilitate the control of the primary-side switch Q1, such as Figure 11 As shown, the logic drive circuit 132 also includes a driver 1322, which includes an input terminal and an output terminal.

[0108] The input terminal of driver 1322 is connected to the output terminal of RS flip-flop 1321, and the output terminal of driver 1322 is connected to primary-side switch Q1 to control the on and off of primary-side switch Q1.

[0109] In order to use the magnetizing inductance current of the complete transformer T as the ripple feedforward of the feedback control circuit 11, such as Figure 12 As shown, the flyback circuit 100 also includes a ripple feedforward circuit 20, which is connected in parallel between the two ends of the secondary winding Ns of the transformer T.

[0110] Specifically, the ripple feedforward circuit 20 includes a seventh resistor R7 and a fifth capacitor C5. One end of the seventh resistor R7 is connected to one end (e.g., the same-name end) of the secondary winding Ns of the transformer, and the other end of the seventh resistor R7 is connected to one end of the fifth capacitor C5. The other end of the fifth capacitor C5 is connected to the other end (e.g., the opposite-name end) of the secondary winding Ns of the transformer.

[0111] Wherein, the product of the seventh resistor R7 and the fifth capacitor C5 satisfies R*C=Lm / n, where R is the resistance of the seventh resistor R7, C is the capacitance of the fifth capacitor C5, Lm is the magnetizing inductance of the primary winding Np, and n is the turns ratio of the primary winding Np to the secondary winding Ns.

[0112] like Figure 13 As shown, the voltage V across the fifth capacitor C5 is... C The magnetizing inductance current of the primary winding Np changes with the change in the magnetizing inductance current, so that the magnetizing inductance current of the primary winding Np can be converted into a voltage that can be calculated.

[0113] As another aspect of this invention, an embodiment provides a charger that includes the flyback circuit 100 described above. This charger can process input power to charge various electronic devices.

[0114] Finally, it should be noted that the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not intended to impose additional limitations on the content of the present invention; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of the present invention. Furthermore, within the framework of the present invention, the above-mentioned technical features can be combined with each other, and many other variations of different aspects of the present invention as described above exist, all of which are considered to be within the scope of the present invention specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A control circuit, characterized in that, Applied to a flyback circuit, the flyback circuit includes a primary-side switching transistor, a secondary-side rectifier transistor, and a transformer for isolating current; the control circuit includes: A feedback control circuit includes at least one of a first feedback control circuit and a second feedback control circuit, wherein the feedback control circuit is configured to generate a secondary-side control signal for controlling the secondary-side rectifier diode to turn off, wherein the secondary-side control signal is generated by the first feedback control circuit based on the DC component of the output voltage signal of the flyback circuit secondary side and the current ripple signal of the transformer, and / or is generated by the second feedback control circuit based on the DC component of the output current signal of the flyback circuit secondary side and the current ripple signal of the transformer; An isolated transmission circuit, connected to the feedback control circuit, is configured to generate a first primary-side control signal based on the secondary-side control signal; The primary-side control circuit, connected to the isolation transmission circuit, is configured to control the conduction of the primary-side switching transistor when it receives the first primary-side control signal of the first mode from the isolation transmission circuit.

2. The control circuit according to claim 1, characterized in that, The primary-side control circuit is further configured to simultaneously receive the first primary-side control signal and the second primary-side control signal, and to control the on and off of the primary-side switching transistor based on the first primary-side control signal and the second primary-side control signal.

3. The control circuit according to claim 2, characterized in that, The second primary-side control signal is generated based on a primary-side current detection signal that indicates the current flowing through the primary winding of the transformer.

4. The control circuit according to claim 3, characterized in that, The primary-side control circuit includes a first comparator, which includes a first input terminal, a second input terminal, and an output terminal. The first input terminal of the first comparator is used to receive the primary-side current detection signal, the second input terminal of the first comparator is applied with a first reference voltage, and the output terminal of the first comparator outputs the second primary-side control signal according to the primary-side current detection signal and the first reference voltage.

5. The control circuit according to claim 2, characterized in that, The primary-side control circuit includes a logic driving circuit, which includes a first input terminal, a second input terminal, and an output terminal. The first input terminal of the logic driving circuit is input with the first primary-side control signal, the second input terminal of the logic driving circuit is input with the second primary-side control signal, the output terminal of the logic driving circuit is connected to the primary-side switching transistor, and the logic driving circuit outputs the primary-side driving signal according to the first primary-side control signal and the second primary-side control signal to control the conduction and turn-off of the primary-side switching transistor.

6. The control circuit according to claim 5, characterized in that, The logic driving circuit includes an RS flip-flop, which includes a set input terminal, a reset input terminal, and an output terminal. The set input of the RS flip-flop is the first input of the logic driving circuit, the reset input of the RS flip-flop is the second input of the logic driving circuit, and the output of the RS flip-flop is the output of the logic driving circuit.

7. The control circuit according to claim 6, characterized in that, The logic driving circuit also includes a driver, which includes an input terminal and an output terminal; The input terminal of the driver is connected to the output terminal of the RS flip-flop, and the output terminal of the driver is connected to the primary-side switching transistor.

8. The control circuit according to claim 1, characterized in that, It also includes a secondary-side controller, which is connected to the feedback control circuit and the secondary-side rectifier. When the secondary-side controller receives a secondary-side control signal from the first mode of the feedback control circuit, it controls the secondary-side rectifier to turn off.

9. The control circuit according to any one of claims 1 to 8, characterized in that, The first feedback control circuit includes a first compensation circuit and a second comparator. The first compensation circuit includes a first input terminal, a second input terminal, and an output terminal; the second comparator includes a first input terminal, a second input terminal, and an output terminal. The first input terminal of the first compensation circuit is used to receive the DC component of the output voltage signal and the current ripple signal of the transformer. The second input terminal of the first compensation circuit is used to receive a second reference voltage. The output terminal of the first compensation circuit is connected to the first input terminal of the second comparator. The second input terminal of the second comparator is used to receive a third reference voltage. The output terminal of the second comparator is connected to the secondary rectifier and the isolation transmission circuit, respectively.

10. The control circuit according to claim 9, characterized in that, The first compensation circuit includes a first operational amplifier, a first resistor, and a first capacitor; The non-inverting input terminal of the operational amplifier is the first input terminal of the first compensation circuit, the inverting input terminal of the first operational amplifier is the second input terminal of the first compensation circuit, and the output terminal of the first operational amplifier is the output terminal of the first compensation circuit. The first resistor and the first capacitor are connected in series. One end of the series connection is connected to the output terminal of the first operational amplifier and the first input terminal of the second comparator, respectively, and the other end of the series connection is grounded.

11. The control circuit according to claim 10, characterized in that, The first feedback control circuit further includes a first preprocessing circuit, which is connected to the positive terminal of the output voltage and the non-inverting input terminal of the first operational amplifier, respectively.

12. The control circuit according to claim 11, characterized in that, The first preprocessing circuit includes a second resistor, a third resistor, a fourth resistor, and a second capacitor; One end of the second resistor and one end of the second capacitor are connected to the positive terminal of the output voltage. The other end of the second capacitor and one end of the third resistor are connected to the non-inverting input terminal of the first operational amplifier. The other end of the third resistor, the other end of the second resistor, and one end of the fourth resistor are connected together. The other end of the fourth resistor is grounded.

13. The control circuit according to any one of claims 1 to 8, characterized in that, The second feedback control circuit includes a second compensation circuit and a third comparator; The second compensation circuit includes a first input terminal, a second input terminal, and an output terminal; the third comparator includes a first input terminal, a second input terminal, and an output terminal. The first input terminal of the second compensation circuit is used to receive the DC component of the output current and the current ripple signal of the transformer. The second input terminal of the second compensation circuit is used to receive a fourth reference voltage. The output terminal of the second compensation circuit is connected to the first input terminal of the third comparator. The second input terminal of the third comparator is used to receive a fifth reference voltage. The output terminal of the third comparator is connected to the secondary rectifier and the isolation transmission circuit, respectively.

14. The control circuit according to claim 13, characterized in that, The second compensation circuit includes a second operational amplifier, a fifth resistor, and a third capacitor; The non-inverting input of the second operational amplifier is the first input of the second compensation circuit, the inverting input of the second operational amplifier is the second input of the second compensation circuit, and the output of the second operational amplifier is the output of the second compensation circuit. The fifth resistor is connected in series with the third capacitor. One end of the series connection is connected to the output terminal of the second operational amplifier and the first input terminal of the third comparator, respectively, and the other end of the series connection is grounded.

15. The control circuit according to claim 14, characterized in that, The second feedback control circuit also includes a second preprocessing circuit, which is connected to the positive terminal of the output voltage and the non-inverting input terminal of the second operational amplifier, respectively.

16. The control circuit according to claim 15, characterized in that, The second preprocessing circuit includes an amplifier circuit, a sixth resistor, and a fourth capacitor; The amplifier circuit includes a first input terminal, a second input terminal, and an output terminal; The first input terminal of the amplifier circuit is input with the DC component of the output current signal. The second input terminal of the amplifier circuit is grounded. The output terminal of the amplifier circuit is connected to one end of the sixth resistor. The other end of the sixth resistor and one end of the fourth capacitor are connected to the non-inverting input terminal of the second operational amplifier. The other end of the fourth capacitor is used to connect to the positive terminal of the output voltage.

17. The control circuit according to claim 1, characterized in that, The isolated transmission circuit includes a transmitter, an isolation device, and a receiver; The transmitter includes an input terminal and an output terminal, the isolation device includes an input terminal and an output terminal, and the receiver includes an input terminal and an output terminal; The input terminal of the transmitter is connected to the feedback control circuit, the output terminal of the transmitter is connected to the input terminal of the isolation device, the output terminal of the isolation device is connected to the input terminal of the receiver, and the output terminal of the receiver is connected to the primary-side control circuit.

18. The control circuit according to claim 17, characterized in that, The isolation device includes one or more of capacitors, magnetic components, and optocouplers.

19. A flyback circuit, characterized in that, This includes primary-side switching transistors, transformers for current isolation, secondary-side rectifier transistors, and... The control circuit as described in any one of claims 1 to 18.

20. The flyback circuit according to claim 19, characterized in that, It also includes a ripple feedforward circuit, which is connected in parallel between the two ends of the secondary winding of the transformer.

21. The flyback circuit according to claim 20, characterized in that, The ripple feedforward circuit includes a seventh resistor and a fifth capacitor. One end of the seventh resistor is connected to one end of the secondary winding of the transformer, and the other end of the seventh resistor is connected to one end of the fifth capacitor. The other end of the fifth capacitor is connected to the other end of the secondary winding of the transformer.

22. A charger, characterized in that, Includes the flyback circuit as described in any one of claims 19 to 21.

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