A Control Method for ZVS-DSR Bilateral Feedback Converter

Abstract

The present invention provides a control method for a ZVS-DSR bilateral feedback converter, including: when the input unit is powered, the first switch is closed and the second switch is opened, so that the input current of the input unit is stored in the transformer; the first switch is opened and the second switch is closed to transfer the current stored in the transformer to the output capacitor and the output unit for output; the input of the input unit and the first switch are opened and the second switch is closed to make the electric energy in the output capacitor be reversely output to the transformer through the secondary winding; the second switch is opened to demagnetize the transformer, reduce the voltage of the primary winding, and reduce the mutual inductance voltage of the primary winding or the auxiliary winding; when the voltage is lower than the first preset voltage or the falling slope reaches the preset slope, the first switch is turned on to make the first loop conduct at the valley or conduct with zero voltage, and corresponding energy is transferred to the output unit according to the signal time. The present invention can achieve the first loop to conduct at the valley or conduct with zero voltage, avoiding the waste of electric energy when the converter conducts.

Description

Technical Field

[0001] The present invention relates to the technical field of converters, and particularly relates to a control method for a ZVS-DSR bilateral feedback converter. Background Art

[0002] Compared with the traditional optocoupler structure of secondary-side feedback, the primary-side feedback architecture (PSR) has the greatest advantage in that it eliminates these two chips and a set of components that work with them. Therefore, it has a broad market and prospects in the mobile phone charger market. However, the primary-side feedback usually has only one output voltage feedback loop, and the change of the secondary-side voltage can only be detected when the secondary side of the transformer demagnetizes. Therefore, the concept of the bilateral feedback architecture (DSR) is also proposed, hoping to detect the change of the secondary-side voltage through the primary side, so as to realize the control of the secondary-side and primary-side switching tubes. However, the biggest problem in the actual application of DSR control is the detection of primary and secondary signals. Since the signals and the transformer waveforms share the transformer, it is very difficult to solve the signal detection problem in the application. In addition, in DSR, due to too many functions, there is a problem of insufficient VCC power supply, and there is also a problem of excessive energy loss after increasing the power supply. Therefore, how to achieve zero-voltage switching (ZVS) has become an urgent problem to be solved. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a control method for a ZVS-DSR bilateral feedback converter.

[0004] The present invention provides the following technical solutions:

[0005] The present application provides a control method for a ZVS-DSR bilateral feedback converter, which is applied to a converter. The converter includes: a primary side, a transformer, and a secondary side. The transformer includes a primary winding and a secondary winding;

[0006] The primary side includes: an input unit, a first switch, and a primary winding. The secondary side includes: a secondary winding, an output capacitor, a second switch, and an output unit; the input unit, the first switch, and the primary winding are sequentially connected to form a first loop; the secondary winding, the second switch, and the output capacitor are sequentially connected to form a second loop; the output unit is connected to the output capacitor;

[0007] The method includes:

[0008] When the input unit supplies power, the first switch is in the closed state, and the second switch is in the open state, so that the input current of the input unit is stored in the transformer. Then, the first switch is disconnected and the second switch is closed to transfer the current stored in the transformer to the output capacitor and the output unit for output;

[0009] Disconnect the input of the input unit and the first switch, and close the second switch, so that the electric energy in the output capacitor is reversely output to the transformer through the secondary winding;

[0010] Disconnect the second switch to demagnetize the transformer, so that the voltage of the primary winding is reduced, or an auxiliary winding is added to reduce the mutual inductance voltage of the primary winding or the auxiliary winding; when the voltage is lower than the first preset voltage or the falling slope reaches the preset slope, the first switch is turned on to make the valley of the first loop conduct or conduct at zero voltage, and corresponding energy is transmitted to the output unit according to the signal time.

[0011] In one embodiment, the method further includes:

[0012] Obtain the output energy formula of the converter, and determine the switching signal on the secondary side according to the output energy formula;

[0013] The output energy formula is: 0.5×IPK 2 ×FL; where IPK is the primary peak current, F is the frequency, and L is the transformer inductance. After the primary side self-establishes the initial operating voltage, the frequency is controlled by the secondary side;

[0014] The primary side controls the current on the primary side according to the switching signal on the secondary side to form a bilateral feedback.

[0015] In one embodiment, the method further includes:

[0016] The primary side takes the closing time of the first loop, or the last reverse time, or the demagnetization time after the second loop is closed as the initial moment, and obtains the conduction moment of the reverse current of the second loop, and calculates the time difference between the initial moment and the conduction moment;

[0017] Set the peak current value of the primary side conduction according to the time difference, and the setting method is:

[0018] Set at least one time period, which corresponds to a fixed current in the time period range, and / or the peak current decreases with the increase of the time difference in a time period interval.

[0019] In one embodiment, the obtaining of the conduction moment of the reverse current of the second loop includes:

[0020] Obtain the first voltage waveform on the secondary side. If the first voltage waveform changes from a resonant waveform to a flat waveform, obtain the change moment and take the change moment as the conduction moment;

[0021] And / or, obtain the waveform of the second voltage on the primary side or the secondary side, determine whether the falling speed of the waveform of the second voltage is greater than a speed threshold, and use the moment when the falling speed is greater than the speed threshold as the conduction moment.

[0022] In one embodiment, the determining whether the falling speed of the waveform of the second voltage is greater than a speed threshold includes:

[0023] The threshold setting is corrected according to the secondary output requirement and / or the product itself frequency;

[0024] If it is greater than the preset slope, it is determined that the speed of the waveform of the second voltage is greater than the speed threshold, and it is determined as a DSR signal, and the energy matching the first loop transfer is conducted according to its signal time.

[0025] In one embodiment, the slope signal acquisition method corresponding to the slope adopts at least one of the following: triggering by the voltage change value in a specified time interval, acquiring in a passband mode, acquiring by RC damping, and acquiring by the sudden change of the loop current.

[0026] In one embodiment, the converter further includes a fourth switch, and the fourth switch is connected in parallel with the output unit; when the output voltage is higher than a preset value, at least one of the following methods is adopted to reduce the output voltage:

[0027] Method 1: Turn on the fourth switch to reduce the output voltage;

[0028] Method 2: Turn on the second loop to transfer the excess voltage back to the primary side;

[0029] Method 3: Increase the dummy load to consume the excess voltage.

[0030] In one embodiment, the converter further includes a filter capacitor and a third switch, and the filter capacitor, the output capacitor, the secondary winding and the third switch are sequentially connected to form a third loop; the method further includes:

[0031] Obtain the voltage difference between the filter capacitor voltage and the output capacitor voltage;

[0032] According to the voltage difference, at least one of the following methods is adopted to supply power:

[0033] Method 1: If the voltage difference is greater than or equal to a preset voltage difference, first turn on the second loop to store the electric energy in the output capacitor into the transformer, and then turn on the third loop to supply power to the filter capacitor;

[0034] Method 2: If the voltage difference is less than the preset voltage difference, turn on the third loop, or alternately turn on the third loop and the second loop to supply power to the filter capacitor.

[0035] In one embodiment, to avoid the occurrence of common mode or non-loss of devices after common mode in the control process of the bilateral feedback converter, at least one of the following control methods is adopted:

[0036] Method 1: Piecewise misaligned control of the output voltage;

[0037] Method 2: Piecewise control of the voltage waveform during resonance after demagnetization. On one side of the resonance waveform after demagnetization, it is controlled by the secondary control window, and on the other side, it is the primary control window, with a preset gap margin reserved;

[0038] Method 3: Timing piecewise control, divided into at least one or more timing segments, and each timing segment can only be controlled by one side;

[0039] Method 4: Quickly disconnect when common mode occurs;

[0040] Method 5: Absorb energy when common mode occurs.

[0041] In one embodiment, when the supply voltage on the primary side is insufficient, at least one of the following methods is adopted to increase the supply voltage:

[0042] Method 1: Increase the supply voltage on the primary side by increasing the dummy load and raising the frequency on the primary side;

[0043] Method 2: Put the supply voltage on the primary side into sleep or hiccup restart;

[0044] Method 3: Increase the frequency or current on the primary side. When the energy transferred to the secondary side is too large, retransmit it back to the primary side by increasing the DSR current.

[0045] The embodiments of the present invention have the following beneficial effects:

[0046] The ZVS-DSR bilateral feedback converter control method provided by the present invention charges the transformer by using the secondary winding after demagnetization, and then disconnects the second switch to demagnetize the transformer, so that the first voltage at the connection end of the primary winding and the first switch decreases; when the first voltage is lower than the first preset voltage, the first switch conducts, so that the first loop valley conducts or zero voltage conducts, avoiding the waste of electric energy when the converter conducts, and can also ensure the safety of the circuit.

[0047] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following specific preferred embodiments are given, and in conjunction with the accompanying drawings, the detailed description is as follows. Description of the Drawings

[0048] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0049] Figure 1 It shows a schematic diagram of the circuit structure of a ZVS-DSR bilateral feedback converter in this embodiment;

[0050] Figure 2 It shows a schematic diagram of the flow of a control method for a ZVS-DSR bilateral feedback converter in this embodiment;

[0051] Figure 3 It shows a schematic diagram of the transformation of the control circuit of a ZVS-DSR bilateral feedback converter in this embodiment;

[0052] Figure 4 It shows a schematic diagram of the flow of a method for setting the peak current value in this embodiment;

[0053] Figure 5 It shows a schematic diagram of a waveform change in this embodiment;

[0054] Figure 6 It shows another schematic diagram of a waveform change in this embodiment;

[0055] Figure 7 It shows a schematic diagram of the first power supply for the filter capacitor in this embodiment;

[0056] Figure 8 It shows a schematic diagram of the second power supply for the filter capacitor in this embodiment;

[0057] Figure 9 It shows a schematic diagram of the third power supply for the filter capacitor in this embodiment;

[0058] Figure 10 It shows a schematic diagram of the fourth power supply for the filter capacitor in this embodiment.

[0059] Main element symbol description:

[0060] T1, transformer; NP, primary winding; NS, secondary winding; K1, first switch; K2, second switch; K3, third switch; K4, fourth switch; EC1, input capacitor; EC2, output capacitor; EC3, filter capacitor; D1, diode; R1, load resistor. Specific embodiments

[0061] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0062] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. On the contrary, when an element is referred to as being "directly on" another element, there is no intermediate element. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0063] In the present invention, unless otherwise clearly defined and limited, terms such as "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0064] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise clearly and specifically defined.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this template herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. When there is a disagreement in the understanding of the embodiments, the description in the claims shall prevail. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0066] Embodiment 1

[0067] See Figure 1 , Figure 1Schematic diagram of the circuit structure of a ZVS-DSR bilateral feedback converter provided in this embodiment. The converter includes: a primary side, a transformer T1, and a secondary side. The transformer T1 includes a primary winding NP and a secondary winding NS.

[0068] The primary side includes: an input unit, a first switch K1, and a primary winding NP. The secondary side includes: a secondary winding NS, an output capacitor EC2, a second switch K2, and an output unit. The input unit, the first switch K1, and the primary winding NP are sequentially connected to form a first loop. The secondary winding NS, the second switch K2, and the output capacitor EC2 are sequentially connected to form a second loop. The output unit is connected to the output capacitor EC2.

[0069] See Figure 2 , Figure 2 Schematic diagram of the control method flow of a ZVS-DSR bilateral feedback converter provided in this embodiment. The method includes:

[0070] S201. When the input unit is powered, the first switch is in the closed state, and the second switch is in the open state, so that the input current of the input unit is stored in the transformer. Then, the first switch is opened and the second switch is closed to transfer the current stored in the transformer to the output capacitor and the output unit for output.

[0071] S202. Disconnect the input of the input unit and the first switch, and close the second switch, so that the electrical energy in the output capacitor is reversely output to the transformer through the secondary winding.

[0072] See Figure 3 , Figure 3 Schematic diagram of the circuit transformation of a ZVS-DSR bilateral feedback converter control circuit provided in this embodiment.

[0073] Specifically, when the ZVS-DSR bilateral feedback converter control circuit is in normal operation, its state is as shown in a of Figure 3 . At this time, the input unit can store energy in the transformer T1. When the first switch K1 is opened, the state of the control circuit is as shown in b of Figure 3 and c of Figure 3 . At this time, the input unit no longer supplies power to the transformer T1. Then, the second switch K2 is closed, so that the electrical energy in the output capacitor EC2 on the secondary side is reversely output to the transformer T1 through the secondary winding NS.

[0074] S203. Disconnect the second switch to demagnetize the transformer, thereby reducing the voltage of the primary winding, or add an auxiliary winding to reduce the mutual inductance voltage of the primary winding or the auxiliary winding; when the voltage is lower than the first preset voltage or the falling slope reaches the preset slope, the first switch is turned on to enable the valley conduction or zero-voltage conduction of the first loop, and transfer the corresponding energy to the output unit according to the signal time.

[0075] After the electric energy of the output capacitor EC2 is input into the transformer T1, disconnect the second switch K2 again. As shown in d of Figure 3 , at this time, since the electric energy in the secondary-side output capacitor EC2 cannot be reversely output to the transformer T1 through the secondary winding NS, the transformer T1 starts to demagnetize, and the first voltage at the connection end of the primary winding NP and the first switch K1 decreases. When the first voltage is lower than the first preset voltage, control the first switch K1 to turn on, thereby realizing the first loop, that is, the valley conduction or zero-voltage conduction of the primary-side circuit. Thus, the switch junction capacitance and the transformer T1 junction capacitance losses are reduced. The saved junction capacitance loss is: 0.5 * C * V * V * F, where C is the junction capacitance of the switch tube and the transformer T1, V is the voltage across the switch tube, and F is the frequency.

[0076] In one implementation, the method further includes:

[0077] Obtain the output energy formula of the converter, and determine the switching signal on the secondary side according to the output energy formula;

[0078] The output energy formula is: 0.5 × IPK 2 × FL; where IPK is the primary peak current, F is the frequency, and L is the transformer inductance. After the primary side self-establishes the initial operating voltage, the frequency is controlled by the secondary side;

[0079] The primary side controls the current on the primary side according to the switching signal on the secondary side to form a bilateral feedback.

[0080] According to the output energy formula, the primary side can use the secondary switch as a signal to control the primary current to form a DSR bilateral feedback, thereby realizing the removal of the optocoupler to meet different output requirements, including realizing variable voltage output and forming a new ZVS-DSR bilateral feedback circuit.

[0081] See Figure 4 , the ZVS-DSR bilateral feedback converter control method further includes:

[0082] S301. The primary side takes the closing time of the first loop, or the last reverse time, or the demagnetization time after the second loop is closed as the initial moment, obtains the conduction moment of the reverse current of the second loop this time, and calculates the time difference between the initial moment and the conduction moment.

[0083] Specifically, the second loop can simultaneously achieve at least two or more of the following functions: synchronous rectification can be achieved during demagnetization. Also, it continues to conduct after demagnetization to achieve reverse inrush current to realize primary valley or zero-voltage turn-on soft switching. Define the reverse conduction time of the second loop according to the output demand to transmit the secondary signal; it can replace the dummy load to discharge the excess energy to the primary; achieve the bidirectional conduction function of output power supply to input according to the requirements of both sides.

[0084] S302. Set the peak current value of the primary side conduction according to the time difference, and the setting method is: at least set a time period, which corresponds to a fixed current within the time period range, and / or the peak current decreases with the increase of the time difference within a time period interval.

[0085] In this embodiment, the secondary side feeds back the signal to the primary side by using the length of the time sequence instead of the level of the optocoupler feedback voltage, and directly corresponds or dynamically controls the current of the primary side conduction by the feedback time of the secondary side, so as to achieve the balanced energy transfer.

[0086] See Figure 5 , Figure 5 which is a schematic diagram of waveform change provided for this embodiment.

[0087] Among them, Figure 5 a in is the voltage waveform diagram of the switching tube or transformer in the discontinuous mode, Figure 5 b in is the current waveform diagram in the transformer in the discontinuous mode.

[0088] In one implementation manner, the obtaining the conduction moment of the reverse current of the second loop this time includes:

[0089] Obtain the first voltage waveform of the secondary side. If the first voltage waveform changes from the resonant waveform to the flat waveform, obtain the change moment and take the change moment as the conduction moment.

[0090] See Figure 6 , Figure 6 which is another schematic diagram of waveform change provided for this embodiment.

[0091] Among them, Figure 6 a in is the voltage waveform diagram of the switching tube or transformer in the critical mode, Figure 6 b in is the current waveform diagram in the transformer in the critical mode.

[0092] And / or, obtain the waveform of the second voltage on the primary side or the secondary side, determine whether the falling speed of the waveform of the second voltage is greater than the speed threshold, and use the moment when the falling speed is greater than the speed threshold as the conduction moment.

[0093] As Figure 5 shown, when zero-voltage conduction is not achieved on the primary side, the voltage waveform detected on the primary side is a resonant waveform. After zero-voltage conduction is achieved on the primary side, its voltage waveform will be converted into a flat waveform. Therefore, the moment of voltage waveform conversion is the zero-voltage conduction moment on the primary side.

[0094] Or, as Figure 6 shown, when zero-voltage conduction is not achieved on the primary side, the voltage waveform detected on the primary side is in a steady decline state. When zero-voltage conduction occurs, the voltage waveform will drop rapidly. Therefore, by obtaining the falling speed of the voltage waveform at each moment and determining whether the falling speed at each moment is greater than the speed threshold, if it is greater than the speed threshold, it indicates that zero-voltage conduction is achieved on the primary side.

[0095] In one implementation, determining whether the falling speed of the waveform of the second voltage is greater than the speed threshold includes:

[0096] The threshold setting is corrected according to the secondary output demand and / or the product's own frequency;

[0097] If it is greater than the preset slope, it is determined that the speed of the waveform of the second voltage is greater than the speed threshold, and it is judged as a DSR signal, and the energy matching the first loop transfer is conducted according to its signal time.

[0098] Among them, the demand of the secondary side load can also be judged according to the zero-voltage conduction signal. As a timing signal to judge the load demand of the secondary side, immediately achieving zero-voltage conduction after demagnetization completion indicates that the secondary side requires the maximum energy supply, and when there is a zero-voltage conduction signal long after demagnetization completion, it indicates that the secondary energy demand is small.

[0099] Whether it is a secondary feedback signal is judged by the different primary resonance slopes formed after conduction on the secondary side. The further slope can be directly captured by the slope integration method or the automatic trigger and hold method. Among them, the automatic trigger and hold adopts the existing voltage capacitor hold, oscillates to generate a pressure difference, the pressure difference enters the capacitor hold through the diode D1 and triggers the comparator, and re-resets for control.

[0100] Specifically, the conduction moment is determined by obtaining the falling speed of the primary side voltage waveform at each moment in real time, or the change state of the voltage waveform. Since there will be a certain delay, that is, hysteresis, when determining the conduction moment by calculating the waveform characteristics or calculating the falling speed. And by obtaining the slope of the voltage waveform, the zero-voltage conduction moment on the primary side can be better captured.

[0101] Among them, the slope signal acquisition method corresponding to the slope adopts at least one of the following: triggering by voltage change value in a specified time interval, acquiring by passband method, acquiring by RC damping, and acquiring by sudden change of loop current.

[0102] In one implementation, obtaining the slope of the second waveform includes:

[0103] Obtaining the slope of the second waveform through a slope calculation formula, and the slope calculation formula is:

[0104] K = △V / △T, where K is the slope, △V is the voltage change amount, and △T is the time change amount;

[0105] Among them, V = △I*L / △T, △I is the Ipk current on the transformer T1, and L is the inductance of the transformer T1.

[0106] Specifically, the voltage in the △T change time can be equivalent to the slope K. Since L is fixed in a transformer T1, it can be simplified to only consider △I, that is, the Ipk current, to distinguish different signal values. Usually, the reverse current needs to be greater than the self-resonant current after the demagnetization of the secondary side is completed. Similarly, whether the secondary side detects the energy transmitted from the primary side or the reverse energy generated by the secondary side itself is also judged by this.

[0107] Further, the formula is deformed into V△T = △I*L. The energy transmitted from the primary side and the secondary DSR signal can be judged and distinguished by integrating V△T. Through the slope judgment method of the above deformation method, the interference of noise can be effectively removed, and at the same time, signal transmission and reception can be truly realized only by this in any time period.

[0108] See Figure 7 , Figure 7 which is the first power supply schematic diagram of the filter capacitor EC3 provided in this embodiment.

[0109] The converter further includes a filter capacitor EC3. The filter capacitor EC3, the output capacitor EC2, the secondary winding NS, and the second switch K2 are sequentially connected to form a third loop; the method further includes:

[0110] Obtaining the voltage difference between the voltage of the filter capacitor EC3 and the voltage of the output capacitor EC2;

[0111] If the voltage difference is greater than or equal to a preset voltage difference, first turn on the second loop to store the electric energy in the output capacitor EC2 into the transformer T1, and then turn on the third loop to supply power to the filter capacitor EC3.

[0112] See Figure 8 and Figure 9 ,Figure 8 And Figure 9 It is a schematic diagram of supplying power to two other filter capacitors EC3 provided in this embodiment.

[0113] Specifically, when the second switch K2 is closed and the first switch K1 is opened, the output unit is no longer powered. At this time, the third loop is turned on to form a closed loop, and the electrical energy of the output capacitor EC2 will supply power to the filter capacitor EC3 through the second switch K2.

[0114] If the pressure difference is greater than or equal to the preset pressure difference, that is, the voltage of the filter capacitor EC3 is higher than the voltage of the output capacitor EC2, or the pressure difference between the two is small. If normal power supply is adopted, it will take a long time to conduct the electrical energy of the output capacitor EC2 into the secondary winding NS of the transformer T1, and then conduct it into the filter capacitor EC3 through the secondary winding NS. At this time, the second loop can be turned on first to store the electrical energy in the output capacitor EC2 into the transformer T1, and then the third loop is turned on to realize low-power boost to supply power to the filter capacitor EC3.

[0115] Among them, an input capacitor EC1 can also be provided on the primary side. The input capacitor EC1 is connected in parallel with the input unit. A diode D1 and a load resistor R1 can also be provided on the secondary side. The positive electrode of the diode D1 is connected to the secondary winding NS, the negative electrode of the diode D1 is connected to the load resistor R1, and the load resistor R1 is connected to the filter capacitor EC3 through the third switch K3.

[0116] The filter capacitor, the output capacitor, the secondary winding and the third switch are sequentially connected to form a third loop; the method further includes:

[0117] Obtain the pressure difference between the voltage of the filter capacitor and the voltage of the output capacitor;

[0118] According to the pressure difference, supply power in at least one of the following ways:

[0119] Method 1: If the pressure difference is greater than or equal to the preset pressure difference, first turn on the second loop to store the electrical energy in the output capacitor into the transformer, and then turn on the third loop to supply power to the filter capacitor;

[0120] Method 2: If the pressure difference is less than the preset pressure difference, turn on the third loop, or alternately turn on the third loop and the second loop to supply power to the filter capacitor.

[0121] In one implementation, if the pressure difference is less than the preset pressure difference, the third loop can be directly turned on, or the third loop and the second loop can be alternately turned on, and the transformer T1 is used for low-power step-up to supply power to the filter capacitor EC3.

[0122] Alternatively, the filtering capacitor EC3 is powered by using the mutual inductance voltage of the first loop conduction or the leakage inductance voltage of the second loop.

[0123] In one embodiment, referring to Figures 7 - 9 , the output unit in Figures 7 - 9 can be regarded as the first output unit, and a second output unit is provided on the side of the filtering capacitor EC3. Then, the voltage conversion of the ZVS-DSR bilateral feedback converter can be divided into two aspects.

[0124] First aspect, when , V o1 , V o2 are the voltages of the first output unit and the second output unit respectively.

[0125] Step-down power supply: In stage 1, the first output unit stores energy in the transformer, and the current of the second loop increases in the reverse direction. Let the duration of stage 1 be T 1 , and the duration of stage 2 be T 2 . At the end of stage 1, the secondary-side current is , n is the turns ratio of the primary side and the secondary side of the transformer, is the magnetizing inductance. In stage 2, i s continues to increase in the reverse direction. At the end of stage 2, the secondary-side current is . Among them, stage 1 is the power supply stage when the second loop is closed, and stage 2 is the power supply stage when the third loop is closed.

[0126] 2. When .

[0127] Step-up power supply: In stage 1, the first output unit charges the transformer, and the energy is stored in the transformer. At the end of stage 1, the secondary-side current is . In stage 2, the first output unit and the energy stored in the transformer in stage 1 jointly provide energy for the second output, and the secondary-side current increases. At the end of stage 2, the secondary-side current is .

[0128] Thus, the current and power expressions of the dual output can be obtained as follows:

[0129]

[0130]

[0131]

[0132]

[0133] In the formula,I o1 and P o1 and I o2 and P o2 respectively represent the first output current, the first output power, the second output current, and the second output power. I peak is the peak current on the primary side, T s is the demagnetization time on the secondary side, T is the duty cycle.

[0134] In one embodiment, referring to Figure 10 , the converter further includes a fourth switch K4, and the fourth switch K4 is connected in parallel with the output unit; when the output voltage is higher than a preset value, at least one of the following methods is used to reduce the output voltage:

[0135] Method 1: Turn on the fourth switch to reduce the output voltage;

[0136] Method 2: Turn on the second loop to transfer the excess voltage back to the primary side;

[0137] Method 3: Increase the dummy load to consume the excess voltage.

[0138] In one embodiment, to avoid common conduction or non-loss of devices after common conduction during the control process of the bilateral feedback converter, at least one of the following control methods is used:

[0139] Method 1: Segmented misalignment control of the output voltage;

[0140] Method 2: Segmented control of the voltage waveform during resonance after demagnetization. On one side of the resonance waveform after demagnetization, there is a secondary control window, and on the other side, there is a primary control window, with a preset gap margin reserved;

[0141] Method 3: Timing segmented control, divided into at least one or more timing segments, and each timing segment can only be controlled by one side;

[0142] Method 4: Quickly disconnect when common conduction occurs;

[0143] Method 5: Absorb energy when common conduction occurs.

[0144] In one embodiment, when the supply voltage on the primary side is insufficient, at least one of the following methods is used to increase the supply voltage:

[0145] Method 1: Increase the supply voltage on the primary side by increasing the dummy load and increasing the frequency on the primary side;

[0146] Method 2: Put the primary side supply voltage into sleep or hiccup restart;

[0147] Method 3: Increase the frequency or current of the primary side. When the energy transferred to the secondary side is too large, the excessive energy is fed back to the primary side by increasing the DSR current.

[0148] In one implementation, this embodiment uses at least one of the following methods to prevent the secondary commutation from causing the converter to explode:

[0149] Method 1: During the resonance period after demagnetization is completed, the misaligned voltage conducts: Only the secondary signal of the second loop feedback conducts above the resonance zero-crossing voltage, and the primary side only conducts the first loop during the valley period above the zero voltage.

[0150] Method 2: Divide the period of the secondary feedback signal misaligned: For example, the resonance period and / or the period when resonance is almost completed are left for the second loop to conduct; After a preset period of time, signal feedback is no longer performed. At this time, if the primary side has not received the secondary side signal for the longest time, it will conduct by itself for detection.

[0151] Method 3: Voltage segmented control. Set a reference voltage V1 on the primary side. Before there is no ZVS feedback signal on the secondary side, the primary side controls the converter according to the PSR primary side feedback mode.

[0152] Set two reference voltages V2 and a reference voltage V3 on the secondary side, where the voltage of V3 is higher than that of V2. The ZVS-DSR signal is not fed back before the voltage of V2 is reached to prevent commutation with the primary side. After V2 is reached, according to the requirements of the output unit, the second loop is conducted to feedback the ZVS-DSR signal. When it reaches V3, the frequency is reduced or the feedback is turned off.

[0153] Method 4: The primary side and / or the secondary side has a commutation protection detection function. Once commutation is detected, it is quickly turned off.

[0154] In one implementation, the converter can be either a dual-winding or a triple-winding type; An EC2 capacitor is configured on the main control periphery or directly powered by the input; The output control can also be directly powered by the output or externally equipped with a separate capacitor; A voltage-dividing detection resistor is led from the T1 winding of the transformer to the inside of the chip to detect the output signal by voltage division. When using a triple-winding, the voltage-dividing detection resistor can also be integrated inside; The output voltage detection can be external or integrated into the chip; The secondary control chip can also integrate or externally configure an adjustment pin for the reverse current magnitude; The output primary chip can integrate or externally configure adjustment pins for the load voltage and current.

[0155] The ZVS-DSR converter can replace or add different components according to actual functional requirements: the diode D1 in the ZVS-DSR converter can be replaced with a switching tube; the first switch K1 can be a triode, a MOS tube, or a gallium nitride and Darlington tube; the converter can be electrically connected with EMC components and / or a multi-output module; diodes D1, resistors and other components can be added to the third loop according to its function.

[0156] The types of the input unit include at least one of the following: AC rectifier input, DC input, fluctuating voltage input, capacitor, and battery.

[0157] The output unit includes at least one output, and the at least one output includes but is not limited to: resistive load, capacitive load, motor, LED lamp, other electronic devices, etc.

[0158] In all the examples shown and described here, any specific value should be construed as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0159] It should be noted that like reference numerals and letters denote like items in the following figures, and thus, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0160] The above-described embodiments merely represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A ZVS-DSR bilateral feedback converter control method, applied to a converter, characterized in that: The converter comprises: a primary side, a transformer and a secondary side, wherein the transformer comprises a primary winding and a secondary winding; The primary side includes: an input unit, a first switch and a primary winding, and the secondary side includes: a secondary winding, an output capacitor, a second switch and an output unit; the input unit, the first switch and the primary winding are connected in sequence to form a first loop; the secondary winding, the second switch and the output capacitor are connected in sequence to form a second loop; the output unit is connected to the output capacitor; The method comprises: When the input unit supplies power, the first switch is in a closed state and the second switch is in an open state, so that the input current of the input unit is stored in the transformer, the first switch is opened and the second switch is closed, and the current stored in the transformer is transferred to the output capacitor and the output unit output; Disconnecting the input of the input unit and the first switch, and closing the second switch, so that the electric energy in the output capacitor is outputted to the transformer in reverse through the secondary winding; The second switch is turned off to demagnetize the transformer, thereby reducing the voltage of the primary winding, or an auxiliary winding is added to reduce the mutual inductance voltage of the primary winding or the auxiliary winding; when the voltage is lower than the first preset voltage or the falling slope reaches the preset slope, the first switch is turned on to make the first loop valley-turned on or zero-voltage-turned on, and the corresponding energy is transferred to the output unit according to the signal time; The method further comprises: The primary side uses the closing time of the first loop, or the last reverse time, or the demagnetization time after the second loop is closed as the initial time, obtains the current reverse current conduction time of the second loop, and calculates the time difference between the initial time and the conduction time; The peak current value of the primary side conduction is set according to the time difference, and the setting method is: At least one time period is set, which corresponds to a fixed current within the time period range, and / or the peak current is reduced as the time difference increases within a time period interval.

2. The ZVS-DSR bilateral feedback converter control method according to claim 1, characterized in that: The method further comprises: Obtaining an output energy formula of the converter, and determining a switching signal on the secondary side according to the output energy formula; The output energy formula is: 0.5×IPK 2 ×FL; where IPK is the primary peak current, F is the frequency, and L is the transformer inductance. When the primary side establishes the initial operating voltage, the frequency is controlled by the secondary side; The primary side controls the current of the primary side according to the switching signal of the secondary side to form a bilateral feedback.

3. The ZVS-DSR bilateral feedback converter control method according to claim 1, characterized in that: The obtaining the current reverse current conduction moment of the second loop includes: Acquire a first voltage waveform of the secondary side, and if the first voltage waveform changes from a resonant waveform to a smooth waveform, acquire a change time, and use the change time as the turn-on time; And / or, obtaining the waveform of the second voltage on the primary side or the secondary side, determining whether the waveform drop speed of the second voltage is greater than a speed threshold, and taking the moment when the drop speed is greater than the speed threshold as the turn-on moment.

4. The ZVS-DSR bilateral feedback converter control method according to claim 3, characterized in that: The determining whether the waveform drop speed of the second voltage is greater than a speed threshold comprises: Threshold settings are modified based on secondary output requirements and / or the product’s own frequency; If it is greater than the preset slope, it is determined that the speed of the waveform of the second voltage is greater than the speed threshold and is judged to be a DSR signal. The first loop is turned on to transfer matching energy according to its signal time.

5. The ZVS-DSR bilateral feedback converter control method according to claim 4, characterized in that: The slope signal capture method corresponding to the slope adopts at least one of the following: voltage change value triggering in a specified time interval, passband capture, RC damping capture and loop current sudden change capture.

6. The ZVS-DSR bilateral feedback converter control method according to claim 1, characterized in that: The converter further includes a fourth switch connected in parallel with the output unit; when the output voltage is higher than a preset value, the output voltage is reduced by at least one of the following methods: Mode 1: Turning on the fourth switch to reduce the output voltage; Method 2: Turn on the second loop and transfer the excess voltage back to the primary side; Method 3: Increase the dummy load to consume the excess voltage.

7. The ZVS-DSR bilateral feedback converter control method according to claim 1, characterized in that: The converter further includes a filter capacitor and a third switch, wherein the filter capacitor is connected in sequence with the output capacitor, the secondary winding and the third switch to form a third loop; the method further includes: Obtaining the voltage difference between the filter capacitor voltage and the output capacitor voltage; According to the voltage difference, power is supplied in at least one of the following ways: Method 1: If the voltage difference is greater than or equal to the preset voltage difference, the second loop is first turned on to store the electrical energy in the output capacitor into the transformer, and then the third loop is turned on to supply power to the filter capacitor; Mode 2: If the voltage difference is less than the preset voltage difference, the third loop is turned on, or the third loop and the second loop are turned on alternately to supply power to the filter capacitor.

8. The ZVS-DSR bilateral feedback converter control method according to claim 7, characterized in that: When a common problem occurs during the control process of the bilateral feedback converter, at least one of the following control methods is adopted: Method 1: Output voltage segmented staggered control; Method 2: After demagnetization is completed, the voltage waveform during the resonance period is segmented and controlled. On one side of the demagnetization completed resonance waveform, there is a secondary control window, and on the other side, there is a primary control window, and a preset gap margin is reserved; Method 3: Timing segment control, divided into at least one timing segment, each timing segment can only be controlled by one side; Method 4: Quickly disconnect when a common problem occurs; Method 5: Take energy absorption when common occurs.

9. The ZVS-DSR bilateral feedback converter control method according to claim 1, characterized in that: When the supply voltage on the primary side is insufficient, use at least one of the following methods to increase the supply voltage: Method 1: Increase the primary side supply voltage by increasing the dummy load and the primary side frequency; Method 2: Let the primary side power supply voltage enter sleep mode or hiccup and restart; Method 3: Increase the frequency or current on the primary side. When the energy transferred to the secondary side is too large, it is transferred back to the primary side by increasing the DSR current.

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