Control method and device and switching power supply

Abstract

The invention discloses a control method and device and a switching power supply. The control method comprises the following steps: detecting the loading capacity of the switching power supply; whether the driving signals of the third and first diagonal switching tubes shift phases and the size of a phase shift angle are controlled according to the load capacity, and the control strategy is as follows: when the load capacity is normal, control is performed according to a first phase shift logic; when the loading capacity is insufficient, controlling according to a second phase-shifting logic, and controlling according to a third phase-shifting logic if it is detected that the load is reduced to be smaller than or equal to a first set value during the period; the first phase shift logic is no phase shift; the second phase-shifting logic is as follows: circularly shifting the phase at a set first phase-shifting angle, and controlling the phase-shifting angle of each working period to be less than or equal to the set maximum phase-shifting angle all the time during the period; the third phase-shifting logic is that the phase-shifting angle is reduced in each working period, so that the final phase-shifting angle is the set second phase-shifting angle; wherein the first phase shift angle is larger than the second phase shift angle and smaller than the maximum phase shift angle. According to the invention, higher power can be provided for the switching power supply.

Description

Technical Field

[0001] The present invention relates to the field of power switch control, and in particular to a control method, a control device and a switching power supply. Background Art

[0002] As the mainstream topology in DC converters, full-bridge converters have the characteristics of high power, high efficiency, and high reliability, and are widely used in battery charging, energy storage, and other occasions. Since full-bridge converters have zero voltage conduction, switching losses are greatly reduced. Combined with wide bandgap devices, the switching frequency of the converter can be greatly increased, thereby reducing the size of passive components such as transformers. Therefore, full-bridge converters continue to develop in the direction of high frequency and high integration, which is in line with the development trend of today's energy applications.

[0003] like Figure 1 The figure shows the basic topology of the full-bridge converter. The driving signal of the primary switch tube S5 is consistent with that of the switch tube S2, and the driving signal of the switch tube S6 is consistent with that of the switch tube S1. The two signals are complementary and alternate, and there is a dead time in between. The signals of the diagonal switches on the secondary side are also consistent. KP is the leakage inductance of the primary transformer inductance, L m is the primary equivalent inductance, L ks is the secondary transformer leakage inductance, N P With N S They are the number of turns of the original secondary side, I KP is the primary current, I KS is the current on the secondary side, Vth1 is the voltage on the primary bridge arm, Vth2 is the voltage on the secondary bridge arm, and Vout is the output voltage of the switching power supply.

[0004] Figure 1 When the circuit is just powered on, the secondary side has no power and can only use the body diode for freewheeling. When the output voltage rises to a certain value, the secondary side can work normally, the global enable is turned on, and the synchronous rectifier starts working. If the load of the switching power supply is heavy, the output of the switching power supply will drop and the output voltage of the switching power supply will be unstable. In severe cases, the switching power supply will not be able to provide the required power and cannot carry the load. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present application is to provide a control method, device and switching power supply, which can at least to some extent solve the deficiencies of the above-mentioned prior art.

[0006] As a first aspect of the present invention, the technical solution of the control method provided is as follows: A control method is applied to a switching power supply, wherein the switching power supply adopts a full-bridge converter topology, including a primary full-bridge circuit and a secondary full-bridge synchronous rectification circuit, wherein the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm in the primary full-bridge circuit are first diagonal switch tubes with consistent drive signals, the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are second diagonal switch tubes with consistent drive signals, and the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm in the secondary full-bridge synchronous rectification circuit are third diagonal switch tubes with consistent drive signals, and the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are fourth diagonal switch tubes with consistent drive signals, the drive signal of the first diagonal switch tube is complementary to the drive signal of the second diagonal switch tube and there is a dead time in between, and the drive signal of the third diagonal switch tube is complementary to the drive signal of the fourth diagonal switch tube and there is a dead time in between, wherein the control method comprises: Detect the load capacity of the switching power supply; Whether the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube are phase-shifted and the size of the phase-shift angle are controlled according to the load capacity, and the control strategy is as follows: When the load capacity of the switching power supply is normal, the first phase shift logic is used for control; When the load carrying capacity of the switching power supply is insufficient, the second phase-shift logic control is performed. During this period, if it is detected that the load of the switching power supply is reduced to less than or equal to the first set value, the third phase-shift logic control is performed. The first phase shift logic is: in each working cycle, the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube have no phase shift; The second phase shift logic is: the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube start to cyclically shift phases at a set first phase shift angle, and the cyclic phase shift will make the phase shift angle of the next working cycle equal to the phase shift angle of the previous cycle plus 2 times the first phase shift angle, and during this period, the phase shift angle of each working cycle needs to be controlled to be always less than or equal to the set maximum phase shift angle; The third phase shift logic is: reducing the phase shift angle in each working cycle so that the final phase shift angle is the set second phase shift angle; Wherein: the second phase shift angle < the first phase shift angle < the maximum phase shift angle.

[0007] Furthermore, the load capacity of the switching power supply is detected by detecting the output voltage of the switching power supply. When the output voltage of the switching power supply drops to a second set value, it is considered that the load capacity of the switching power supply is insufficient; otherwise, it is considered that the load capacity of the switching power supply is normal.

[0008] Furthermore, in the first phase-shift logic, by controlling the closing time of the falling edge of the driving signal of the third diagonal switch tube in each working cycle to be earlier than the closing time of the falling edge of the driving signal of the first diagonal switch tube, the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube in each working cycle are achieved without phase shift.

[0009] Furthermore, in the second phase shift logic, the set maximum phase shift angle is .

[0010] Furthermore, in the second phase-shift logic, the delay time of the falling edge of the driving signal of the third diagonal switch tube is controlled to perform phase shift, and the period of the driving signal of the third diagonal switch tube is greater than the period of the driving signal of the first diagonal switch tube.

[0011] Furthermore, in the second phase shift logic, the phase shift angle is forcibly cleared to zero every m cycles, and then the cyclic phase shift is restarted with the set first phase shift angle, so as to control the phase shift angle of each working cycle to always be less than or equal to the set maximum phase shift angle.

[0012] Furthermore, by forcibly stopping the sending of the driving signal of the first diagonal switch tube, the driving signal of the second diagonal switch tube, the driving signal of the third diagonal switch tube and the driving signal of the fourth diagonal switch tube, the phase shift angle is forcibly cleared.

[0013] Furthermore, in the third phase-shift logic, the initial phase-shift angle of the initial working cycle is divided into n parts, and in each working cycle, the phase-shift angle of the driving signal of the third diagonal switch tube is reduced by 1 part compared with the phase-shift angle of the driving signal of the first diagonal switch tube, and the phase-shift angle of the driving signal of the fourth diagonal switch tube is reduced by 1 part compared with the phase-shift angle of the driving signal of the second diagonal switch tube, thereby achieving the final phase-shift angle being the set second phase-shift angle.

[0014] Furthermore, the set second phase shift angle is 0.

[0015] As a second aspect of the present invention, the technical solution of the embodiment of the control device provided is as follows: A control device is applied to a switching power supply, wherein the switching power supply adopts a full-bridge converter topology, and includes a primary full-bridge circuit and a secondary full-bridge synchronous rectification circuit. In the primary full-bridge circuit, the first bridge arm upper switch tube and the second bridge arm lower switch tube are first diagonal switches controlled by a drive signal of the first diagonal switch tube, and the first bridge arm lower switch tube and the second bridge arm upper switch tube are second diagonal switches controlled by a drive signal of the second diagonal switch tube. In the secondary full-bridge synchronous rectification circuit, the first bridge arm upper switch tube and the second bridge arm lower switch tube are first diagonal switches controlled by a drive signal of a third diagonal switch tube, and the first bridge arm lower switch tube and the second bridge arm upper switch tube are second diagonal switches controlled by a drive signal of a fourth diagonal switch tube. The drive signal of the first diagonal switch tube is complementary to the drive signal of the second diagonal switch tube and alternates with a dead time in between, and the drive signal of the third diagonal switch tube is complementary to the drive signal of the fourth diagonal switch tube and alternates with a dead time in between. The control device includes: A detection module is used to detect the load capacity of the switching power supply; The phase shift logic processing module is used to control whether the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube are phase-shifted and the size of the phase shift angle according to the load capacity. The control strategy is as follows: When the load capacity of the switching power supply is normal, the first phase shift logic is used for control; When the load carrying capacity of the switching power supply is insufficient, the second phase-shift logic control is performed. During this period, if it is detected that the load of the switching power supply is reduced to less than or equal to the first set value, the third phase-shift logic control is performed. The first phase shift logic is: in each working cycle, the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube have no phase shift; The second phase shift logic is: the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube start to cyclically shift phases at a set first phase shift angle, and the cyclic phase shift will make the phase shift angle of the next working cycle equal to the phase shift angle of the previous cycle plus 2 times the first phase shift angle, and during this period, the phase shift angle of each working cycle needs to be controlled to be always less than or equal to the set maximum phase shift angle; The third phase shift logic is: reducing the phase shift angle in each working cycle so that the final phase shift angle is the set second phase shift angle; Wherein: the second phase shift angle < the first phase shift angle < the maximum phase shift angle.

[0016] Further, the phase shift logic processing module includes a phase shift control module, a phase shift module and a phase shift clearing module; The phase shift control module is used to compare the signal representing the size of the switching power supply with the second set value, and generate an enable signal to enable the phase shift module to work; The phase shift module is used to generate a basic pulse width when the enable signal enables its operation, and generate a driving signal for the third diagonal switch tube based on the basic pulse width, and the phase shift is selected on the basic pulse width through the transmission gate; The phase shift clearing module is used to forcibly clear the phase shift angle every m cycles during the operation of the phase shift module, and then restart the cyclic phase shift with the set first phase shift angle, so as to control the phase shift angle of each working cycle to be always less than or equal to the set maximum phase shift angle.

[0017] Furthermore, the period of the driving signal of the third diagonal switch tube generated by the phase shift module is greater than the period of the driving signal of the first diagonal switch tube. The phase shift module performs phase shift by controlling the delay time of the falling edge of the driving signal of the third diagonal switch tube, and the step of the cyclic phase shift is the difference between the period of the driving signal of the third diagonal switch tube and the period of the driving signal of the first diagonal switch tube.

[0018] Preferably, the phase shift module includes a Schmitt trigger, an inverter, a D flip-flop, a pulse generating circuit, a delay module and a transmission gate. When the output of the phase shift clearing module is a high level, the phase shift module shapes the falling edge of the midpoint voltage of the first bridge arm in the secondary full-bridge synchronous rectification circuit through the Schmitt trigger and the inverter in turn and inputs it into the D flip-flop, so that the first diagonal switch tube in the secondary full-bridge synchronous rectification circuit is turned on, and then the first diagonal switch tube in the secondary full-bridge synchronous rectification circuit is turned off after passing through the pulse generating circuit and the delay module. The enabling of the transmission gate is controlled by the phase shift control module, which has a basic delay, and this basic delay is the basic pulse width of the driving signal of the third diagonal switch tube. The phase shift operation of the phase shift module is achieved by controlling the time of the basic delay to control the closing time of the falling edge of the driving signal of the third diagonal switch tube.

[0019] Preferably, the phase shift control module comprises: A first phase-subtraction enable, a second two-input AND gate, a third two-input AND gate, a fourth inverter, a first phase-shift control D flip-flop to an nth phase-shift control D flip-flop, a first decoder, a first resistor R1, a second resistor R2, a first transconductance operational amplifier, a third resistor R3, a first capacitor C1, and a first comparator, where n is a natural number greater than or equal to 1; The first phase-subtraction enable includes a three-input OR gate arranged in a geometric series, which is used to stop the phase-shift control when the phase is subtracted to the lowest bit, and each input of the first phase-subtraction enable is connected to the first phase-shift control D flip-flop to the nth phase-shift control D flip-flop. The output terminal is connected to an input terminal of a second two-input AND gate; The output terminal of the second two-input AND gate is connected to the CLK terminal of the first phase-shift controlled D flip-flop, and the D input terminal of each phase-shift controlled D flip-flop is connected to the CLK terminal of the first phase-shift controlled D flip-flop. The output terminals are connected, the Q output terminal of the nth phase-shift controlled D flip-flop is connected to the input of the first decoder, and the Q output terminals of the previous phase-shift controlled D flip-flops are connected to the CLK terminal of the next one; The input of the fourth inverter is connected to the enable signal generated by the phase shift control module, and the output is connected to the Reset end of each phase shift control D flip-flop at the same time; One end of the first resistor R1 is used to connect to the output of the switching power supply, and the other end is connected to the second resistor R2 and the non-inverting end of the first transconductance operational amplifier. The other end of the second resistor R2 is used to be grounded. The reverse end of the first transconductance operational amplifier is used to connect to a reference voltage Vref3, and the output is connected to one side of the third resistor R3. The other side of the third resistor R3 is connected to one end of the first capacitor C1 and the non-inverting end of the first comparator. The other end of the first capacitor C1 is used to be grounded. The inverting end of the first comparator is connected to a reference voltage Vref4. The output of the first comparator is connected to an input end of the third two-input AND gate. The other input end of the third two-input AND gate is used to connect to the output of the hysteresis comparator in the switching power supply control loop. The output end of the third two-input AND gate is connected to the other input end of the second two-input AND gate.

[0020] Preferably, the phase shift module comprises: The first inverter group, the first delay module to the second n Delay module, first transmission gate to 2 n A transmission gate, a first inverter, a first delayed pulse module, a first two-input NOR gate, a second inverter, a first D flip-flop, a third inverter, a first Schmitt trigger, a first two-input AND gate, wherein n is a natural number greater than or equal to 1; The input of the first inverter group is connected to the output D<2 of the phase shift control module. n :1>, output is DN<2 n :1>, the number is 2 n , respectively control 2 n a transmission gate among transmission gates; The input of the first delay module is connected to the output of the second inverter, and the output is connected to the input of the second delay module and the input of the first transmission gate. n The delay modules are connected in series, and the output of each delay module is connected to the input of the corresponding transmission gate at the same time. The output of each transmission gate is connected to the secondn The outputs of the delay modules are connected together and then connected to the Reset terminal of the first D flip-flop; The input of the first Schmitt trigger is used to connect to the midpoint of the first bridge arm in the secondary full-bridge synchronous rectification circuit, and the output is connected to the input of the third inverter, and the output of the third inverter is connected to the CLK terminal of the first D flip-flop; The D terminal of the first D flip-flop is connected to the power supply voltage VCC, and the Q output terminal is connected to the input of the first two-input AND gate. The output terminal is connected to the input of the first inverter and one input terminal of the first two-input NOR gate; The output of the first inverter is connected to the input of the first delayed pulse module, the output of the first delayed pulse module is connected to the other end of the first two-input NOR gate, and the output of the first two-input NOR gate is connected to the input of the second inverter; The other input end of the first two-input AND gate is connected to the output signal of the phase shift clearing module, and the output of the first two-input AND gate outputs the driving signal of the third diagonal switch tube.

[0021] Preferably, the phase-shift clear module comprises a first phase-shift clear D flip-flop to an mth phase-shift clear D flip-flop, a first counting state machine and a fifth inverter, where m is a natural number greater than or equal to 1; The CLK terminal of the first phase-shift-clear D flip-flop is connected to the signal shaped by the falling edge of the midpoint voltage of the first bridge arm in the secondary full-bridge synchronous rectification circuit through the Schmitt trigger and the inverter in sequence. The CLK terminals of the remaining phase-shift-clear D flip-flops are connected to the Q output terminal of the previous phase-shift-clear D flip-flop and an input terminal of the first counting state machine. The D input terminal of each phase-shift-clear D flip-flop is connected to the Q output terminal of the previous phase-shift-clear D flip-flop and an input terminal of the first counting state machine. At the output end, the Reset terminal of each phase-shifted reset D flip-flop is connected to the overall enable signal of the switching power supply. When the switching power supply is initialized and the output rises, the overall enable signal is at a high level. The first counting state machine includes a two-input AND gate arranged in a geometric progression, and the output end of the first counting state machine outputs a counting state. The output of the first counting state machine is 1 only when all inputs are 1, otherwise the output is 0; The input terminal of the fifth inverter is connected to the output terminal of the first counting state device. When the signal output by the output terminal is at a high level, it indicates that the phase shift module needs to forcibly clear the phase shift angle.

[0022] As a third aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows: A switching power supply adopts a full-bridge converter topology, including a primary full-bridge circuit and a secondary full-bridge synchronous rectification circuit, wherein the switch tube on the first bridge arm and the switch tube on the second bridge arm in the primary full-bridge circuit are first diagonal switch tubes with consistent drive signals, the switch tube on the first bridge arm and the switch tube on the second bridge arm are second diagonal switch tubes with consistent drive signals, the switch tube on the first bridge arm and the switch tube on the second bridge arm in the secondary full-bridge synchronous rectification circuit are third diagonal switch tubes with consistent drive signals, the switch tube on the first bridge arm and the switch tube on the second bridge arm are fourth diagonal switch tubes with consistent drive signals, the drive signal of the first diagonal switch tube is complementary to the drive signal of the second diagonal switch tube and there is a dead time in between, the drive signal of the third diagonal switch tube is complementary to the drive signal of the fourth diagonal switch tube and there is a dead time in between, wherein: the switching power supply also includes the control device described in any one of the second aspects above.

[0023] The theoretical basis of the present application is that the inventor has found that when there is a phase shift in the control of the secondary full-bridge synchronous rectification circuit and the primary full-bridge circuit of the full-bridge converter topology, it is beneficial to improve the load capacity of the switching power supply, but it will reduce the efficiency of the switching power supply. Based on this discovery, the present application is proposed, and the beneficial effects of the present application are analyzed as follows: (1) When the load capacity of the switching power supply is normal, the first phase shift logic is used for control, and the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube in each working cycle have no phase shift, thereby ensuring that the switching power supply has a better efficiency; (2) For the full-bridge converter topology, the technical personnel in this field believe that the movement of the secondary side phase will cause the secondary side to produce a cyclic phase shift during phase shift. Assuming that the newly generated phase shift angle in each cycle is a fixed phase shift angle, since two bridge arms work alternately in each cycle, the phase shift angle in each cycle will be based on the phase shift angle of the previous cycle plus twice the above-mentioned fixed phase shift angle. The cycle-by-cycle accumulation of the secondary side phase shift angle will cause the power of the switching power supply to be greatly reduced, thereby not only failing to improve the load-carrying capacity of the switching power supply, but also causing the load-carrying capacity to deteriorate rapidly, and ultimately the output cannot carry the load. The phenomenon of cyclic phase shift on the secondary side is something that the technical personnel in this field want to avoid. The inventor of the present application has turned a disadvantage into an advantage. When the load-carrying capacity of the switching power supply is insufficient, the second phase shift logic is used to control the third diagonal switch tube. The driving signal and the driving signal of the first diagonal switch tube start to cyclically shift the phase with the set first phase shift angle. The cyclic phase shift will make the phase shift angle of the next working cycle equal to the phase shift angle of the previous cycle plus 2 times the first phase shift angle. The phase shift angle increases rapidly through accumulation. The output power of the switching power supply is increased by increasing the phase shift angle, so that the load capacity of the switching power supply is improved. If it is detected that the load of the switching power supply is reduced to less than or equal to the first set value during the period, the third phase shift logic control is used to reduce the phase shift angle in each working cycle to avoid the increase of the phase shift angle reducing the efficiency of the switching power supply. If the load capacity of the switching power supply is insufficient in the process of reducing the phase shift angle, the second phase shift logic control is used again. In this way, the control strategy is continuously adjusted, so that the load capacity of the switching power supply and the better efficiency can be taken into account at the same time. (3) Since the primary and secondary sides of the full-bridge converter switching power supply will instinctively start cyclic phase shifting once they start to shift phase at a certain phase shift angle, the implementation of cyclic phase shifting in the embodiment of the present invention becomes simpler compared to some solutions that require providing a reference point to solve the cyclic phase shift problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the topology diagram of the full-bridge converter; Figure 2 is a flow chart of a control method according to a first embodiment of the present invention; Figure 3 is a principle block diagram of a control device according to a second embodiment of the present invention; Figure 4 is a key signal waveform diagram of a specific embodiment of the control device of the second embodiment of the present invention; Figure 5 This is a specific circuit block diagram of the control device of the second embodiment of the present invention applied to a switching power supply; Figure 6 yes Figure 5 A specific circuit diagram of a phase shift control module inside a phase shift logic processing module; Figure 7 yes Figure 5 A specific circuit diagram of a phase shift module inside a phase shift logic processing module; Figure 8 yes Figure 5 A specific circuit diagram of a phase-shift clearing module within a phase-shift logic processing module. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0026] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application are described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, switching power supply, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] It should be understood that, in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

[0029] In addition, the drawings of the present disclosure are only schematic diagrams of the present disclosure and are not necessarily drawn to scale. The same symbols in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented using software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontrollers.

[0030] The inventive concept of the present application is: to utilize the unfavorable characteristic of the natural cyclic phase shift of the full-bridge converter switching power supply to increase the average phase; after a certain cyclic phase shift, the accumulated phase shift angle is forcibly cleared to zero to interrupt the cyclic phase shift, thereby turning harm into benefit, thereby improving the load-carrying capacity of the switching power supply, and the switching power supply will not be unable to carry the load, so that the operation of the switching power supply is more stable.

[0031] At the same time, by consulting relevant literature, it is found that the phase difference between the primary and secondary sides of the full-bridge converter switching power supply is related to the output power of the switching power supply. Under ideal conditions, the proportional relationship between the output power and the phase shift angle is: Pn∝θ(π-θ) Pn is power, θ is the phase shift angle between the primary and secondary sides. It can be seen that the relationship between power and phase shift angle has a maximum value, which is the maximum at π / 2. Therefore, the present invention needs to always control the phase shift angle within π / 2 during the cyclic phase shift process. In specific implementation, the accumulated phase shift angle can be cleared by setting the number of cycles, thereby interrupting the cyclic phase shift. By reasonably setting the cyclic phase shift step and number, the average phase shift of the switching power supply is increased, so that it is always within π / 2 while providing higher power.

[0032] First embodiment This embodiment provides a control method, which is applied to a switching power supply. The circuit topology of the switching power supply can refer to Figure 1 and Figure 5 The switching power supply adopts a full-bridge converter topology, including a primary full-bridge circuit and a secondary full-bridge synchronous rectification circuit. In the primary full-bridge circuit, the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm are first diagonal switch tubes with consistent driving signals, the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are second diagonal switch tubes with consistent driving signals, in the secondary full-bridge synchronous rectification circuit, the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm are third diagonal switch tubes with consistent driving signals, the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are fourth diagonal switch tubes with consistent driving signals, the driving signal of the first diagonal switch tube is complementary to the driving signal of the second diagonal switch tube and there is a dead time in between, and the driving signal of the third diagonal switch tube is complementary to the driving signal of the fourth diagonal switch tube and there is a dead time in between.

[0033] It should be noted that: Figure 1 Each open tube in the first diagonal switch tube to the fourth diagonal switch tube is an other-driven switch tube; Figure 5 In the middle, the upper switch tube of each bridge arm is a self-driven switch tube, and the lower switch tube is an other-driven switch tube. The self-driven switch tube of the primary side selects a path by the primary winding of the transformer, and the self-driven switch tube of the secondary side selects a path by the secondary winding of the transformer. This is common knowledge for those skilled in the art. Figure 1 and Figure 5 The switching power supply topology is only an example and should not be regarded as limiting the scope of protection of the present invention. The driving mode and type of the switch tube can be selected by those skilled in the art as needed based on the inventive concept of the present application.

[0034] Figure 2 is a flow chart of the control method of the first embodiment of the present invention, see Figure 2 , the control method of this embodiment includes: Detect the load capacity of the switching power supply; Whether the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube are phase-shifted and the size of the phase-shift angle are controlled according to the load capacity. The control strategy is as follows: When the load capacity of the switching power supply is normal, it is controlled according to the first phase shift logic; When the load carrying capacity of the switching power supply is insufficient, the second phase-shift logic control is performed. During this period, if it is detected that the load of the switching power supply is reduced to less than or equal to the first set value, the third phase-shift logic control is performed. The first phase shift logic is: the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube in each working cycle have no phase shift; The second phase shift logic is: the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube start to cyclically shift phases at a set first phase shift angle, and the cyclic phase shift will make the phase shift angle of the next working cycle equal to the phase shift angle of the previous cycle plus 2 times the first phase shift angle, and during this period, the phase shift angle of each working cycle needs to be controlled to be always less than or equal to the set maximum phase shift angle; The third phase shift logic is: reducing the phase shift angle in each working cycle so that the final phase shift angle is the set second phase shift angle; Among them: the second phase shift angle < the first phase shift angle < the maximum phase shift angle.

[0035] In this embodiment, when the load capacity of the switching power supply is normal, the first phase-shift logic control can ensure that the switching power supply has a better efficiency; when the load capacity of the switching power supply is insufficient, the second phase-shift logic control is performed. During this period, if it is detected that the load of the switching power supply is reduced to less than or equal to the first set value, the third phase-shift logic control is performed, thereby taking into account both the load capacity of the switching power supply and the better efficiency.

[0036] As a specific implementation of this embodiment, the load capacity of the switching power supply is detected by detecting the output voltage of the switching power supply. When the output voltage of the switching power supply drops to a second set value, it is considered that the load capacity of the switching power supply is insufficient; otherwise, it is considered that the load capacity of the switching power supply is normal.

[0037] As a specific implementation of this embodiment, in the first phase shift logic, by controlling the closing time of the falling edge of the driving signal of the third diagonal switch tube in each working cycle to be earlier than the closing time of the falling edge of the driving signal of the first diagonal switch tube, the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube in each working cycle are achieved without phase shift.

[0038] As a specific implementation of this embodiment, in the second phase shift logic, the maximum phase shift angle is set to π / 2.

[0039] As a specific implementation of this embodiment, in the second phase-shift logic, the delay time of the falling edge of the driving signal of the third diagonal switch tube is controlled to perform phase shift, and the period of the driving signal of the third diagonal switch tube is greater than the period of the driving signal of the first diagonal switch tube.

[0040] As a specific implementation of this embodiment, in the second phase shift logic, the phase shift angle is forcibly cleared to zero every m cycles, and then the cyclic phase shift is restarted with the set first phase shift angle, so as to control the phase shift angle of each working cycle to always be less than or equal to the set maximum phase shift angle.

[0041] As a specific implementation of this embodiment, the phase shift angle is forced to be cleared by forcibly stopping the driving signal of the first diagonal switch tube, the driving signal of the second diagonal switch tube, the driving signal of the third diagonal switch tube and the driving signal of the fourth diagonal switch tube.

[0042] As a specific implementation of this embodiment, in the third phase shift logic, the initial phase shift angle of the initial working cycle is divided into n parts, and the phase shift angle of the driving signal of the third diagonal switch tube in each working cycle is reduced by 1 part compared with the phase shift angle of the driving signal of the first diagonal switch tube, and the phase shift angle of the driving signal of the fourth diagonal switch tube is reduced by 1 part compared with the phase shift angle of the driving signal of the second diagonal switch tube, thereby achieving the final phase shift angle being the set second phase shift angle.

[0043] As a specific implementation of this embodiment, the second phase shift angle is set to 0, in order to improve the efficiency of the switching power supply.

[0044] Second embodiment This embodiment provides a control device, which is applied to a switching power supply. The circuit topology of the switching power supply can also refer to Figure 1 and Figure 5The switching power supply adopts a full-bridge converter topology, including a primary full-bridge circuit and a secondary full-bridge synchronous rectification circuit. In the primary full-bridge circuit, the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm are first diagonal switch tubes with consistent driving signals, the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are second diagonal switch tubes with consistent driving signals, in the secondary full-bridge synchronous rectification circuit, the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm are third diagonal switch tubes with consistent driving signals, the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are fourth diagonal switch tubes with consistent driving signals, the driving signal of the first diagonal switch tube is complementary to the driving signal of the second diagonal switch tube and there is a dead time in between, and the driving signal of the third diagonal switch tube is complementary to the driving signal of the fourth diagonal switch tube and there is a dead time in between. Figure 1 and Figure 5 The topology is also just an example and should not limit the scope of protection of the present invention.

[0045] Figure 3 : is a principle block diagram of a control device according to a second embodiment of the present invention, wherein the control device comprises: A detection module is used to detect the load capacity of the switching power supply; The phase shift logic processing module is used to control whether the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube are phase-shifted and the size of the phase shift angle according to the load capacity. The control strategy is as follows: When the load capacity of the switching power supply is normal, it is controlled according to the first phase shift logic; When the load carrying capacity of the switching power supply is insufficient, the second phase-shift logic control is performed. During this period, if it is detected that the load of the switching power supply is reduced to less than or equal to the first set value, the third phase-shift logic control is performed. The first phase shift logic is: the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube in each working cycle have no phase shift; The second phase shift logic is: the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube start to cyclically shift phases at a set first phase shift angle, and the cyclic phase shift will make the phase shift angle of the next working cycle equal to the phase shift angle of the previous cycle plus 2 times the first phase shift angle, and during this period, the phase shift angle of each working cycle needs to be controlled to be always less than or equal to the set maximum phase shift angle; The third phase shift logic is: reducing the phase shift angle in each working cycle so that the final phase shift angle is the set second phase shift angle; Among them: the second phase shift angle < the first phase shift angle < the maximum phase shift angle.

[0046] The technical means adopted by the control device of this embodiment correspond to and are consistent with the control method of the first embodiment, and have the same beneficial effects, so they will not be described in detail. In addition, some specific implementation methods provided in the control method of the first embodiment can be extended to the corresponding units of this embodiment, and this embodiment will not describe them one by one.

[0047] As a specific implementation of this embodiment, the phase shift logic processing module includes a phase shift control module, a phase shift module and a phase shift clearing module; The phase shift control module is used to compare the signal representing the size of the switching power supply with the second set value, and generate an enable signal to enable the phase shift module to work; The phase shift module is used to generate a basic pulse width when the enable signal enables its operation, and generate a driving signal for the third diagonal switch tube based on the basic pulse width, and the phase shift is selected on the basic pulse width through the transmission gate; The phase shift clearing module is used to forcibly clear the phase shift angle every m cycles during the operation of the phase shift module, and then restart the cyclic phase shift with the set first phase shift angle, so as to control the phase shift angle of each working cycle to always be less than or equal to the set maximum phase shift angle.

[0048] As a specific implementation of this embodiment, the period of the driving signal of the third diagonal switch tube generated by the above-mentioned phase shift module is greater than the period of the driving signal of the first diagonal switch tube. The phase shift module performs phase shift by controlling the delay time of the falling edge of the driving signal of the third diagonal switch tube. The step of the cyclic phase shift is the difference between the period of the driving signal of the third diagonal switch tube and the period of the driving signal of the first diagonal switch tube.

[0049] As a specific implementation method of this embodiment, the above-mentioned phase shift module includes a Schmitt trigger, an inverter, a D flip-flop, a pulse generating circuit, a delay module and a transmission gate. When the output of the phase shift clearing module is a high level, the phase shift module shapes the falling edge of the midpoint voltage of the first bridge arm in the secondary full-bridge synchronous rectification circuit through the Schmitt trigger and the inverter in turn and inputs it into the D flip-flop, so that the first diagonal switch tube in the secondary full-bridge synchronous rectification circuit is turned on, and then the first diagonal switch tube in the secondary full-bridge synchronous rectification circuit is turned off after passing through the pulse generating circuit and the delay module. The enabling of the transmission gate is controlled by the phase shift control module, which has a basic delay, and this basic delay is the basic pulse width of the driving signal of the third diagonal switch tube. The phase shift operation of the phase shift module is achieved by controlling the closing time of the falling edge of the driving signal of the third diagonal switch tube by controlling the time of the basic delay.

[0050] Figure 4 is a key signal waveform diagram of a specific embodiment of the control device of the second embodiment of the present invention, combined with Figure 5 The detailed analysis is as follows: There will be no phase shift within the normal load range of the switching power supply, ensuring the efficiency of the switching power supply. When the load capacity of the switching power supply is insufficient, the output voltage will drop and touch the phase shift reference line, triggering the phase shift angle of the drive signal of the third diagonal switch tube and the drive signal of the first diagonal switch tube to move to the set first phase shift angle, and then the output of the switching power supply will rise, and the secondary side of the switching power supply and the corresponding primary side drive signal will also begin cyclic phase shift. After the switching power supply has undergone m-1 cycles of cyclic phase shift, the mth cycle is cleared to zero, so that the cyclic phase shift stops and the phase shift starts again in the next cycle. During the cyclic phase shift process, an integral circuit can be used to detect changes in the output load of the switching power supply. When the load is heavy, the switching power supply will not reduce the phase, ensuring that the output ripple is stable under heavy load. When the load of the switching power supply drops to a light load, the switching power supply does not need to shift the phase to increase the power, and the phase reduction operation is enabled. Figure 5 The output signal VEN of the hysteresis comparator 306 in the circuit will flip back and forth. The signal is a low-frequency signal, and the initial phase shift can be reduced by using the signal to improve the efficiency of the switching power supply. Figure 3 The phase shift is divided into n parts in the setting, and each flip is reduced by 1 part, and the final phase shift is minimized. If the switching power supply cannot carry the load during the process of reducing the phase shift, the phase will shift to the set first phase shift angle, and the cyclic phase shift control will begin. During the operation of the switching power supply, the drive signal of the third diagonal switch tube and the drive signal of the first diagonal switch tube will be regularly detected and adjusted to see whether the phase is shifted and the size of the phase shift angle, ensuring that the load capacity of the switching power supply and the best efficiency can be taken into account at the same time under all working conditions.

[0051] In terms of circuits, Figure 5 As shown, it is a specific circuit block diagram of the control device of the second embodiment of the present invention applied to the switching power supply, which includes: the basic framework circuit of the full-bridge converter; the primary side switch tubes MP1, MP2, MN1 and MN2; the secondary side synchronous rectification switch tubes MP3, MP4, MN3 and MN4; the feedback network 310, comparator 306, reference voltage Vref1, digital isolator 305 and primary side chip 304 in feedback control; the phase comparator 307 and phase shift logic processing modules 308 and 309 of the secondary side phase shift enable detection.

[0052] Specifically, Figure 5 Including: PMOS tube MP1 and PMOS tube MP2, PMOS tube MP3 and PMOS tube MP4; primary leakage inductor L KP , primary inductance L M , secondary leakage inductance L KS, transformer 314, NMOS tube MN1 and NMOS tube MN2, NMOS tube MN3 and NMOS tube MN4; driving module 302, driving module 303, driving module 311, driving module 312, primary chip 304, digital isolator 305, comparator 306, comparator 307, phase shift logic processing modules 308, 309, feedback network 310, input power supply 301, output load 313. PMOS tube MP1 and PMOS tube MP2 are connected in a cross-coupling form, that is, the source of PMOS tube MP1 and the source of PMOS tube MP2 are both connected to the input power supply 301, the gate of MP1 is connected to the drain of MP2, and the gate of MP2 is connected to the drain of MP1. The gate of NMOS tube NM1 is connected to the output of driving module 302, and the gate of NMOS tube NM2 is connected to the output of driving module 303. The sources of NM1 and NM2 are connected to the primary GND, the drain of NM1 is connected to the drain of PM1, and the drain of NM2 is connected to the drain of PM2. The PMOS tube MP3 and the PMOS tube MP4 are connected in a cross-coupling form, that is, the source of the PMOS tube MP3 and the source of the PMOS tube MP4 are both connected to Vout, the gate of MP3 is connected to the drain of MP4, and the gate of MP4 is connected to the drain of MP3. The gate of the NMOS tube NM3 is connected to the output of the driving module 311, and the gate of the NMOS tube NM4 is connected to the output of the driving module 312. The sources of NM3 and NM4 are connected to the secondary VSS, the drain of NM3 is connected to the drain of PM3, and the drain of NM4 is connected to the drain of PM4. The input of the feedback network 310 is connected to Vout, and the output is connected to the inverting terminal of the comparator 306. The in-phase terminal of the comparator 306 is connected to the reference voltage Vref1. The comparator 306 outputs the VEN signal connected to the input of the digital isolator 305. The output of the digital isolator 305 is connected to the primary chip 304. The primary chip outputs S1_D and S2_D, which are input to the input terminals of the driver module 302 and the driver module 303. The output of the feedback network is also connected to the inverting terminal of the comparator 307. The in-phase terminal of the comparator 307 is connected to the reference voltage Vref2. The comparator 307 outputs Shift_EN. The phase shift logic processing 308 and 309 inputs Shift_EN, VS, VD, and VEN signals, and outputs S3_D and S4_D signals, which are input to the driver module 311 and the driver module 312.

[0053] Figure 5The driving modules 302, 303, 311 and 312 of each power tube of the circuit. The switching power supply is mainly hysteresis control. When the output voltage drops to the lower limit of hysteresis, the output of comparator 306 is high level, which is transmitted to the primary chip 304 through the digital isolator 305 to control the primary side to drive and provide energy. When the output voltage rises to the upper limit of hysteresis, the output of comparator 306 is low, and the primary side is no longer driven. When the output of the phase shift comparator 307 is triggered to flip, the phase shift logic processing module 308 starts to enable phase shift, so that the output power of the switching power supply increases and the output voltage recovers upward.

[0054] As Figure 5 A specific embodiment of the phase shift logic processing module in the embodiment includes a phase shift module, a phase shift control module, and a phase shift clearing module. The signal passes through the phase shift module to generate a basic pulse width, which is the basic conduction time of the secondary side synchronous rectification switch tube, and the phase shift is selected through the transmission gate on this basis. The phase shift control module controls the phase shift enable and detects the output load condition, so that the switching power supply can balance between output power and efficiency. The phase shift clearing module is configured to clear the accumulated phase shift angle of its cyclic phase shift after a certain period, so that the average phase shift angle of the switching power supply is within π / 2.

[0055] The phase shift in this specific implementation is achieved by controlling the delay time of the falling edge of the synchronous rectifier tube to move the phase. The condition for generating cyclic phase shift is that the period of the secondary side after phase shift is greater than the primary side driving period, and the step size of the cyclic phase shift is the difference between the two times.

[0056] In the above-mentioned phase shift module, when the output signal CLR of the phase shift clear module is high, the falling edge of the midpoint voltage VS of the first bridge arm in the secondary full-bridge synchronous rectification circuit is input to the D trigger through the Schmitt trigger and the inverter, so that the secondary synchronous rectifier tube is turned on, and then the secondary synchronous rectifier tube is turned off after passing through the pulse generation circuit and the delay module. The transmission gate enable of the delay module is controlled by the phase shift control module, which has a basic delay. This delay is the initial pulse width of the synchronous rectification. The phase shift operation is to control the closing time of the falling edge of the voltage VS by controlling the delay time.

[0057] Figure 6 yes Figure 5 For a specific circuit diagram of the phase-shift control module inside the phase-shift logic processing module, see Figure 6, wherein the phase shift control module includes: phase subtraction enable 501, AND gate 502, inverter 503, phase shift control D flip-flop 504, phase shift control D flip-flop 505, phase shift control D flip-flop 506, all the way to the nth phase shift control D flip-flop, decoder 507, transconductance operational amplifier 508, comparator 509, AND gate 510, resistor R1, resistor R2, resistor R3 and capacitor C1. The phase subtraction enable 501 is composed of three-input OR gates arranged in a geometric progression, which is mainly to make the phase shift control stop when the phase is subtracted to the lowest bit. Each input of the phase subtraction enable 501 is connected to the first phase shift control D flip-flop (504) to a D flip-flop in the nth phase shift control D flip-flop. At the output end, the output of the phase-subtraction enable 501 is connected to one end of the AND gate 502, the other end of the AND gate 502 is connected to the output of the AND gate 510, one end of the input of the AND gate 510 is connected to the signal VEN output by the hysteresis comparator 306, and the other end is connected to the signal sub_EN output by the comparator 509, the in-phase terminal of the comparator 509 is connected to the resistor R3 and one end of the capacitor C1, the inverting terminal is connected to the reference voltage Vref4, the other end of the capacitor C1 is grounded, the other end of the resistor R3 is connected to the output of the transconductance operational amplifier 508, the inverting terminal of the transconductance operational amplifier 508 is connected to the reference resistor Vref3, one end of the resistor R1 is connected to the output voltage Vout of the switching power supply, the other end of the transconductance operational amplifier 508 is connected to the voltage divider end of the resistor R1 and the resistor R2, and the other end of the resistor R2 is grounded. The output of the AND gate 502 is connected to the CLK end of the phase-shift control D flip-flop 504. In addition, the D input ends of all the phase-shift control D flip-flops are connected to the output of the flip-flop. The Q terminal is connected to the CLK terminal of the next phase-shift controlled D flip-flop. The output of each phase-shift controlled D flip-flop is The n outputs are connected to the input of the decoder 507, the Reset terminals of all the phase-shift-controlled D flip-flops are connected to the output of the inverter 503, and the input of the inverter 503 is connected to the output shift_EN signal of the comparator 307.

[0058] The shift_EN signal is the output of the phase-shift enable comparator. The output of the decoder is connected to the phase-shift module to control the falling edge delay time. If the first phase-subtraction enable is not a multiple of 3, the input can be filled with VSS to form a multiple of 3. Vref3 is the reference value of the integral circuit, and its value should be proportional to the output hysteresis range. Vref4 is the reference line for whether the switching power supply is phase-shifted when the load changes.

[0059] The phase shift reset module outputs a reset signal after counting the mth cycle, interrupting the synchronous rectification in the cyclic phase shifting process, so that it will not continue to circulate, and restart the phase shifting in the next cycle. The switching power supply utilizes the characteristics of cyclic phase shifting to shift the phase, but due to the reset module, the switching power supply will not be unable to carry the load during the cyclic phase shifting process. By adjusting the delay and reset signal, the switching power supply phase will be shifted up and output higher power.

[0060] Figure 7 yes Figure 5 For a specific circuit diagram of the phase-shift module inside the phase-shift logic processing module, see Figure 7 The phase shift module includes: inverter group 401, delay module 402, delay module 403, delay module 404, nth delay module 405, delay module 412, transmission gate 406, transmission gate 407, transmission gate 408, nth transmission gate 409, inverter 410, NOR gate 411, delay module 412, inverter 413, D flip-flop 414, AND gate 415, inverter 416, Schmitt trigger 417. The input of inverter group 401 is connected to the phase shift control The output of the control module is D<2n:1>, and the output is DN<2n:1>, which is 2n in number, and controls 2n transmission gates in sequence respectively. The input of the delay module 402 is connected to the output of the inverter 410, and the output of 402 is connected to the delay module 403 and the transmission gate 406. The delay module 403 to the 2nth delay module 409 are connected in series, and the output of each delay module is connected to the input of the corresponding transmission gate at the same time. The outputs of the transmission gates are connected together and then connected to the Reset terminal of the D flip-flop 414. The D terminal of the D flip-flop 414 is connected to VCC, the CLK terminal is connected to the output VS1 of the inverter 416, and the output Q of the flip-flop is connected to the input of the AND gate 415. The AND gate 415 is connected to the input of the inverter 413 and one input of the NOR gate 411. The output of the inverter 413 is connected to the other end of the NOR gate 411, and the output of the NOR gate 411 is connected to the input of the inverter 410. The other input of the AND gate 415 is connected to the output CLR signal of the phase shift clear module. The AND gate 415 outputs the S3_D signal. The input of the Schmitt trigger 417 is connected to VS, and the output is connected to the input of the inverter 416.

[0061] See also Figure 5 The S3_D signal is the control signal of the synchronous rectifier tube of a bridge arm on the secondary side, which is connected to the driving module to drive the corresponding synchronous rectifier tube, and VS is the midpoint voltage of the bridge arm.

[0062] The above phase shift control module, when the output belt does not move and the load decreases, when it touches the phase shift reference line, enables the control to trigger the phase shift, QN <n:1>The output is all 1, which is input to the decoder for processing. An integral circuit is designed to detect the output load. When the load is heavy, the switching power supply phase reduction operation is prohibited to ensure output stability. When the load becomes light, phase shifting is no longer needed to ensure power output. In order to improve efficiency, the phase reduction operation is enabled, and the comparator output in the hysteresis control is used to control the phase shift for subtraction, which is a low-frequency signal. When it can flip back and forth, it means that the output power of the switching power supply can carry the current load.

[0063] Figure 8 yes Figure 5 For a specific circuit diagram of the phase-shift clearing module inside the phase-shift logic processing module, see Figure 8 The phase-shift clear module includes: phase-shift clear D flip-flop 601, phase-shift clear D flip-flop 602, phase-shift clear D flip-flop 603, until the mth phase-shift clear D flip-flop, counting state machine 604, inverter 605. The CLK of the phase-shift clear D flip-flop 601 is connected to the signal VS1, and the other phase-shift clear D flip-flops are all connected to the output of D input terminal The output terminal Q is connected to the CLK terminal of the next D flip-flop, and this is repeated. The output Q terminal of each phase-shifted and cleared D flip-flop is input to the counting state machine 604. The counting state machine 604 is composed of a two-input AND gate, which is arranged in a geometric series, and finally outputs a counting state, which is connected to the input of the inverter 605, and the output CLR signal of the inverter 605. The Reset of all D flip-flops is connected to the overall enable signal ENP of the switching power supply.

[0064] The signal VS1 is the signal after the falling edge of the midpoint voltage of the first bridge arm in the secondary full-bridge synchronous rectification circuit is shaped by the Schmitt trigger and the inverter in sequence. Figure 7 , which is the signal output by the inverter 416.

[0065] Figure 8 The counter state machine 604 in the circuit has an output of 1 only when all inputs are 1, otherwise the output is 0. The ENP signal is the overall enable signal of the switching power supply. When the switching power supply is initialized and the output rises, ENP is high level, so the phase shift clearing module will work even if the switching power supply has no phase shift.

[0066] Optionally, in the mth cycle, regardless of whether the switching power supply has phase shifting, the synchronous rectifier is turned off in this cycle and the current is continued through the body diode.

[0067] Figure 5 The phase shift logic processing module in the circuit adopts Figure 6 , Figure 7 and Figure 8 After the circuit is implemented, the timing of the switching power supply is: when the switching power supply is just powered on, the secondary side has no power and can only use the body diode to continue current. When the output voltage rises to a certain value, the secondary side can work normally, the global enable is turned on, and the synchronous rectifier starts to work. If the switching power supply can carry the load, the output Shift_EN signal of the phase shift comparator 307 is always low, and the phase shift control module 500 drops to the lowest level after a certain period, that is, there is no phase shift. When the load is heavy, the switching power supply power cannot provide the required output power, and the output will drop. When the phase shift comparison reference line (and reference voltage Vref2) is triggered, the phase shift comparator 307 outputs a high level. At this time, the QN output of the phase shift control module 500 <n:1>The outputs are all 1, and the phase moves to the set first phase shift angle. The switching power supply meets the condition of cyclic phase shift, and the switching power supply starts cyclic phase shift. After m cycles, the phase shift clearing module 600 outputs CLR low level, so that the synchronous rectifier is turned off in this cycle, and the body diode is used for continuous current, thereby interrupting the cyclic phase shift of the switching power supply. When the switching power supply detects that the load becomes light load, the phase reduction is enabled. At this time, after the output of the hysteresis comparator 306 is flipped n times, the switching power supply returns to the zero phase state. In this process, if the load suddenly increases and triggers the phase shift comparison reference line, the switching power supply will promptly add the phase to the set first phase shift angle.

[0068] The above specific implementation method utilizes the characteristics of the cyclic phase shift of the switching power supply. Under the appropriate cyclic phase shift, the cyclic phase shift can be interrupted at the appropriate time by setting the reset signal, so that the average phase shift of the switching power supply can be increased. The average phase shift of the switching power supply increases and does not exceed π / 2, so there is a certain improvement in power. The reference line is set to trigger the phase reduction function to ensure output stability when overloaded, and to improve the efficiency of the switching power supply by reducing the phase when lightly loaded.

[0069] Third embodiment The present embodiment provides a switching power supply, which adopts a full-bridge converter topology and includes a primary full-bridge circuit and a secondary full-bridge synchronous rectification circuit. In the primary full-bridge circuit, the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm are first diagonal switch tubes with consistent drive signals, and the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are second diagonal switch tubes with consistent drive signals. In the secondary full-bridge synchronous rectification circuit, the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm are first diagonal switch tubes with consistent drive signals, and the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are second diagonal switch tubes with consistent drive signals. The drive signal of the first diagonal switch tube is complementary to the drive signal of the second diagonal switch tube and alternates with a dead time in between. The drive signal of the third diagonal switch tube is complementary to the drive signal of the fourth diagonal switch tube and alternates with a dead time in between. The switching power supply further includes the control device described in any one of the second embodiments above.

[0070] The switching power supply of this embodiment has the following beneficial effects because it includes the control device described in any one of the second embodiments above: 1. No reference point is required to solve the cyclic phase shift. The cyclic phase shift of the switching power supply is used to shift the phase. By setting a suitable cyclic step, the average phase shift of the switching power supply is increased and does not exceed the set range. 2. The switching power supply can determine whether to enable the switching power supply phase reduction operation by detecting the load condition, thereby ensuring that the output voltage of the switching power supply is stable when it is heavily loaded and the efficiency is improved when it is lightly loaded.

[0071] The above are only preferred embodiments of the invention. It should be noted that the above preferred embodiments should not be regarded as limitations of the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A control method, applied to a switching power supply, wherein the switching power supply adopts a full-bridge converter topology, including a primary full-bridge circuit and a secondary full-bridge synchronous rectification circuit, wherein the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm in the primary full-bridge circuit are first diagonal switches with consistent drive signals, the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are second diagonal switches with consistent drive signals, the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm in the secondary full-bridge synchronous rectification circuit are third diagonal switches with consistent drive signals, the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are fourth diagonal switches with consistent drive signals, the drive signal of the first diagonal switch tube is complementary to the drive signal of the second diagonal switch tube and there is a dead time in between, the drive signal of the third diagonal switch tube is complementary to the drive signal of the fourth diagonal switch tube and there is a dead time in between, characterized in that The control method comprises: Detect the load capacity of the switching power supply; Whether the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube are phase-shifted and the size of the phase-shift angle are controlled according to the load capacity, and the control strategy is as follows: When the load capacity of the switching power supply is normal, the first phase shift logic is used for control; When the load carrying capacity of the switching power supply is insufficient, the second phase-shift logic control is performed. During this period, if it is detected that the load of the switching power supply is reduced to less than or equal to the first set value, the third phase-shift logic control is performed. The first phase shift logic is: in each working cycle, the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube have no phase shift; The second phase shift logic is: the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube start to cyclically shift phases at a set first phase shift angle, and the cyclic phase shift will make the phase shift angle of the next working cycle equal to the phase shift angle of the previous cycle plus 2 times the first phase shift angle, and during this period, the phase shift angle of each working cycle needs to be controlled to be always less than or equal to the set maximum phase shift angle; The third phase shift logic is: reducing the phase shift angle in each working cycle so that the final phase shift angle is the set second phase shift angle; Wherein: the second phase shift angle < the first phase shift angle < the maximum phase shift angle.

2. The control method according to claim 1, characterized in that: The load capacity of the switching power supply is detected by detecting the output voltage of the switching power supply. When the output voltage of the switching power supply drops to a second set value, it is considered that the load capacity of the switching power supply is insufficient; otherwise, it is considered that the load capacity of the switching power supply is normal.

3. The control method according to claim 1, characterized in that: In the first phase-shift logic, by controlling the closing time of the falling edge of the driving signal of the third diagonal switch tube in each working cycle to be earlier than the closing time of the falling edge of the driving signal of the first diagonal switch tube, the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube in each working cycle are phase-shifted.

4. The control method according to claim 1, characterized in that: In the second phase shift logic, the set maximum phase shift angle is π / 2.

5. The control method according to claim 1, characterized in that: In the second phase-shift logic, the delay time of the falling edge of the driving signal of the third diagonal switch tube is controlled to perform phase shift, and the period of the driving signal of the third diagonal switch tube is greater than the period of the driving signal of the first diagonal switch tube.

6. The control method according to claim 1, characterized in that: In the second phase shift logic, the phase shift angle is forcibly cleared to zero every m cycles, and then the cyclic phase shift starts again with the set first phase shift angle, so as to control the phase shift angle of each working cycle to always be less than or equal to the set maximum phase shift angle.

7. The control method according to claim 6, characterized in that: By forcibly stopping the sending of the driving signal of the first diagonal switch tube, the driving signal of the second diagonal switch tube, the driving signal of the third diagonal switch tube and the driving signal of the fourth diagonal switch tube, the phase shift angle is forcibly cleared.

8. The control method according to claim 1, characterized in that: In the third phase-shift logic, the initial phase-shift angle of the initial working cycle is divided into n parts. In each working cycle, the phase-shift angle of the driving signal of the third diagonal switch tube is reduced by 1 part compared with the phase-shift angle of the driving signal of the first diagonal switch tube, and the phase-shift angle of the driving signal of the fourth diagonal switch tube is reduced by 1 part compared with the phase-shift angle of the driving signal of the second diagonal switch tube, thereby achieving the final phase-shift angle being the set second phase-shift angle.

9. The control method according to claim 8, characterized in that: The set second phase shift angle is 0.

10. A control device, applied to a switching power supply, the switching power supply adopts a full-bridge converter topology, including a primary full-bridge circuit and a secondary full-bridge synchronous rectification circuit, wherein the first bridge arm upper switch tube and the second bridge arm lower switch tube in the primary full-bridge circuit are first diagonal switches controlled by a drive signal of the first diagonal switch tube, the first bridge arm lower switch tube and the second bridge arm upper switch tube are second diagonal switches controlled by a drive signal of the second diagonal switch tube, and the first bridge arm upper switch tube and the second bridge arm lower switch tube in the secondary full-bridge synchronous rectification circuit are first diagonal switches controlled by a drive signal of a third diagonal switch tube, the first bridge arm lower switch tube and the second bridge arm upper switch tube are second diagonal switches controlled by a drive signal of a fourth diagonal switch tube, the drive signal of the first diagonal switch tube is complementary to the drive signal of the second diagonal switch tube and there is a dead time in between, and the drive signal of the third diagonal switch tube is complementary to the drive signal of the fourth diagonal switch tube and there is a dead time in between, characterized in that The control device comprises: A detection module is used to detect the load capacity of the switching power supply; The phase shift logic processing module is used to control whether the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube are phase-shifted and the size of the phase shift angle according to the load capacity. The control strategy is as follows: When the load capacity of the switching power supply is normal, the first phase shift logic is used for control; When the load carrying capacity of the switching power supply is insufficient, the second phase-shift logic control is performed. During this period, if it is detected that the load of the switching power supply is reduced to less than or equal to the first set value, the third phase-shift logic control is performed. The first phase shift logic is: in each working cycle, the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube have no phase shift; The second phase shift logic is: the driving signal of the third diagonal switch tube and the driving signal of the first diagonal switch tube start to cyclically shift phases at a set first phase shift angle, and the cyclic phase shift will make the phase shift angle of the next working cycle equal to the phase shift angle of the previous cycle plus 2 times the first phase shift angle, and during this period, the phase shift angle of each working cycle needs to be controlled to be always less than or equal to the set maximum phase shift angle; The third phase shift logic is: reducing the phase shift angle in each working cycle so that the final phase shift angle is the set second phase shift angle; Wherein: the second phase shift angle < the first phase shift angle < the maximum phase shift angle.

11. The control device according to claim 10, characterized in that: The phase shift logic processing module includes a phase shift control module, a phase shift module and a phase shift clearing module; The phase shift control module is used to compare the signal representing the size of the switching power supply with the second set value, and generate an enable signal to enable the phase shift module to work; The phase shift module is used to generate a basic pulse width when the enable signal enables its operation, and generate a driving signal for the third diagonal switch tube based on the basic pulse width, and the phase shift is selected on the basic pulse width through the transmission gate; The phase shift clearing module is used to forcibly clear the phase shift angle every m cycles during the operation of the phase shift module, and then restart the cyclic phase shift with the set first phase shift angle, so as to control the phase shift angle of each working cycle to be always less than or equal to the set maximum phase shift angle.

12. The control device according to claim 11, characterized in that: The period of the driving signal of the third diagonal switch tube generated by the phase shift module is greater than the period of the driving signal of the first diagonal switch tube. The phase shift module performs phase shift by controlling the delay time of the falling edge of the driving signal of the third diagonal switch tube. The step of the cyclic phase shift is the difference between the period of the driving signal of the third diagonal switch tube and the period of the driving signal of the first diagonal switch tube.

13. The control device according to claim 11, characterized in that: The phase shift module includes a Schmitt trigger, an inverter, a D flip-flop, a pulse generating circuit, a delay module and a transmission gate. When the output of the phase shift clearing module is a high level, the phase shift module shapes the falling edge of the midpoint voltage of the first bridge arm in the secondary full-bridge synchronous rectification circuit through the Schmitt trigger and the inverter in sequence and inputs it into the D flip-flop, so that the first diagonal switch tube in the secondary full-bridge synchronous rectification circuit is turned on, and then the first diagonal switch tube in the secondary full-bridge synchronous rectification circuit is turned off after passing through the pulse generating circuit and the delay module. The enabling of the transmission gate is controlled by the phase shift control module, which has a basic delay, and this basic delay is the basic pulse width of the driving signal of the third diagonal switch tube. The phase shift operation of the phase shift module is achieved by controlling the time of the basic delay to control the closing time of the falling edge of the driving signal of the third diagonal switch tube.

14. The control device according to claim 11, characterized in that: The phase shift control module comprises: A first phase-subtraction enable (501), a second two-input AND gate (502), a third two-input AND gate (510), a fourth inverter (503), a first phase-shift control D flip-flop (504) to an nth phase-shift control D flip-flop, a first decoder (507), a first resistor R1, a second resistor R2, a first transconductance operational amplifier (508), a third resistor R3, a first capacitor C1, and a first comparator (509), wherein n is a natural number greater than or equal to 1; The first phase subtraction enable includes a three-input OR gate arranged in a geometric series, which is used to stop the phase shift control when the phase is subtracted to the lowest bit, and each input of the first phase subtraction enable is connected to the first phase shift control D flip-flop (504) to a D flip-flop in the nth phase shift control D flip-flop. The output terminal is connected to an input terminal of a second two-input AND gate (502); The output terminal of the second two-input AND gate (502) is connected to the CLK terminal of the first phase-shift controlled D flip-flop (504), and the D input terminal of each phase-shift controlled D flip-flop is connected to the CLK terminal of the first phase-shift controlled D flip-flop. The output terminals are connected, the Q output terminal of the nth phase-shift controlled D flip-flop is connected to the input of the first decoder (507), and the Q output terminals of the previous phase-shift controlled D flip-flops are connected to the CLK terminals of the next ones; The input of the fourth inverter (503) is connected to the enable signal generated by the phase shift control module, and the output is simultaneously connected to the Reset end of each phase shift control D flip-flop; One end of the first resistor R1 is used to connect to the output of the switching power supply, and the other end is connected to the second resistor R2 and the non-inverting end of the first transconductance operational amplifier (508); the other end of the second resistor R2 is used to be grounded; the reverse end of the first transconductance operational amplifier (508) is used to connect to a reference voltage Vref3, and the output is connected to one side of the third resistor R3; the other side of the third resistor R3 is connected to one end of the first capacitor C1 and the non-inverting end of the first comparator (509); the other end of the first capacitor C1 is used to be grounded; the reverse end of the first comparator (509) is connected to a reference voltage Vref4; the output of the first comparator (509) is connected to one input end of the third two-input AND gate (510); the other input end of the third two-input AND gate (510) is used to connect to the output of the hysteresis comparator in the switching power supply control loop; the output end of the third two-input AND gate (510) is connected to the other input end of the second two-input AND gate (502).

15. The control device according to claim 11, characterized in that: The phase shift module comprises: The first inverter group (401), the first delay module (402) to the second n Delay module, first transmission gate (406) to 2 n A transmission gate, a first inverter (413), a first delayed pulse module (412), a first two-input NOR gate (411), a second inverter (410), a first D flip-flop (414), a third inverter (416), a first Schmitt trigger (417), a first two-input AND gate (415), wherein n is a natural number greater than or equal to 1; The input of the first inverter group (401) is connected to the output D<2 of the phase shift control module n :1>, output is DN<2 n :1>, the number is 2 n , respectively control 2 n a transmission gate among transmission gates; The input of the first delay module (402) is connected to the output of the second inverter (410), and the output is connected to the input of the second delay module (403) and the input of the first transmission gate (406). n The delay modules are connected in series, and the output of each delay module is connected to the input of the corresponding transmission gate at the same time. The output of each transmission gate is connected to the second n The outputs of the delay modules are connected together and then connected to the Reset terminal of the first D flip-flop (414); The input of the first Schmitt trigger (417) is used to connect to the midpoint of the first bridge arm in the secondary full-bridge synchronous rectification circuit, and the output is connected to the input of the third inverter (416), and the output of the third inverter (416) is connected to the CLK terminal of the first D flip-flop; The D terminal of the first D flip-flop is connected to the power supply voltage VCC, and the Q output terminal is connected to the input of the first two-input AND gate (415). The output end is connected to the input of the first inverter (413) and an input end of the first two-input NOR gate (411); The output of the first inverter (413) is connected to the input of the first delayed pulse module (412), the output of the first delayed pulse module (412) is connected to the other end of the first two-input NOR gate (411), and the output of the first two-input NOR gate (411) is connected to the input of the second inverter (410); The other input end of the first two-input AND gate (415) is connected to the output signal of the phase shift clearing module, and the output of the first two-input AND gate (415) outputs the driving signal of the third diagonal switch tube.

16. The control device according to claim 11, characterized in that: The phase shift clear module comprises a first phase shift clear D flip-flop (601) to an mth phase shift clear D flip-flop, a first counting state machine (604) and a fifth inverter (605), where m is a natural number greater than or equal to 1; The CLK terminal of the first phase-shift-clear D flip-flop (601) is connected to the signal after the falling edge of the midpoint voltage of the first bridge arm in the secondary full-bridge synchronous rectification circuit passes through the Schmitt trigger and the inverter in sequence, and the CLK terminals of the remaining phase-shift-clear D flip-flops are connected to the Q output terminal of the previous phase-shift-clear D flip-flop and an input terminal of the first counting state machine, and the D input terminal of each phase-shift-clear D flip-flop is connected to the Q output terminal of the previous phase-shift-clear D flip-flop and an input terminal of the first counting state machine. At the output end, the Reset terminal of each phase-shifted reset D flip-flop is connected to the overall enable signal of the switching power supply. When the switching power supply is initialized and the output rises, the overall enable signal is at a high level. The first counting state machine (604) comprises a two-input AND gate arranged in a geometric progression. The output terminal of the first counting state machine (604) outputs a counting state. The output of the first counting state machine (604) is 1 only when all inputs are 1, otherwise the output is 0. The input end of the fifth inverter (605) is connected to the output end of the first counting state device (604), and when the signal output by the output end is at a high level, it indicates that the phase shift module needs to forcibly clear the phase shift angle.

17. A switching power supply, the switching power supply adopts a full-bridge converter topology, including a primary full-bridge circuit and a secondary full-bridge synchronous rectification circuit, wherein the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm in the primary full-bridge circuit are first diagonal switch tubes with consistent drive signals, the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are second diagonal switch tubes with consistent drive signals, the upper switch tube of the first bridge arm and the lower switch tube of the second bridge arm in the secondary full-bridge synchronous rectification circuit are third diagonal switch tubes with consistent drive signals, the lower switch tube of the first bridge arm and the upper switch tube of the second bridge arm are fourth diagonal switch tubes with consistent drive signals, the drive signal of the first diagonal switch tube is complementary to the drive signal of the second diagonal switch tube and there is a dead time in between, the drive signal of the third diagonal switch tube is complementary to the drive signal of the fourth diagonal switch tube and there is a dead time in between, characterized in that: The switching power supply further comprises the control device according to any one of claims 10 to 16.

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