CN116073662A - Soft switching device of switching power supply, switching power supply and control method of switching power supply - Google Patents

Soft switching device of switching power supply, switching power supply and control method of switching power supply Download PDF

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Publication number
CN116073662A
CN116073662A CN202211640061.5A CN202211640061A CN116073662A CN 116073662 A CN116073662 A CN 116073662A CN 202211640061 A CN202211640061 A CN 202211640061A CN 116073662 A CN116073662 A CN 116073662A
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Prior art keywords
switching
power supply
switching tube
tube
voltage
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Inventor
何雪冬
张祥
宋蒙恩
翟志伟
霍星星
李白雪
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Gree Electric Appliances Inc of Zhuhai
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Gree Electric Appliances Inc of Zhuhai
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/26—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes without control electrode or semiconductor devices without control electrode to produce the intermediate ac
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/14—Arrangements for reducing ripples from dc input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
    • H02M7/068—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode mounted on a transformer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a soft switching device of a switching power supply, the switching power supply and a control method thereof, wherein the device comprises: a transformer and a switching tube, the transformer having a primary winding and a secondary winding, the primary winding including a first winding; a power bus of the switching power supply is connected to the homonymous end of the first winding; the synonym end of the first winding is connected to the first connecting end of the switch end, the second connecting end of the switch tube is grounded; the secondary winding is output to a load; the first connecting end of the switching tube is connected to the second connecting end of the switching tube after passing through the absorption unit and the resonance unit to form a resonance absorption loop, so that leakage inductance energy of the transformer is absorbed and resonated at the moment that the switching tube is turned off under the condition that the switching tube is turned off, and peak voltage of the switching tube is reduced when the switching tube is turned on in the next period to realize soft switching. According to the scheme, soft switching of the switching tube is realized by utilizing energy of leakage inductance in the switching power supply, so that the switching loss and the switching loss of the switching power supply are reduced.

Description

Soft switching device of switching power supply, switching power supply and control method of switching power supply
Technical Field
The invention belongs to the technical field of switching power supplies, and particularly relates to a soft switching device of a switching power supply, a switching power supply and a control method thereof, in particular to a soft switching circuit of a novel low-loss power supply topology, a switching power supply (such as a flyback isolated switching power supply) of the soft switching circuit with the novel low-loss power supply topology, and a control method of the switching power supply.
Background
The switching power supply is particularly required to pay attention to the control of the loss in the design process, and the loss of the switching power supply mainly comprises an on loss, an on loss and an off loss. In the related scheme, in the topology of a switching power supply (such as a flyback switching power supply) with low power application, a hard switching mode is still adopted, that is, a given driving signal switching tube is turned on, and at the on time or the off time, an included angle between voltage and current is generated due to a platform voltage caused by a miller capacitor, so that the on loss and the off loss of the switching power supply are very large.
The foregoing is provided merely for the purpose of facilitating understanding of the technical solutions of the present invention and is not intended to represent an admission that the foregoing is prior art.
Disclosure of Invention
The invention aims to provide a soft switching device of a switching power supply, the switching power supply and a control method thereof, which are used for solving the problems that the switching power supply adopts a hard switching mode to control the on or off of a switching tube, and the voltage and the current generate an included angle to generate loss due to the platform voltage caused by a Miller capacitor at the on time or the off time of the switching tube, so that the on loss and the off loss of the switching power supply are large, and the effects of realizing the soft switching of the switching tube by utilizing the energy of leakage inductance in the switching power supply and reducing the on loss and the off loss of the switching power supply are achieved.
The invention provides a soft switching device of a switching power supply, which comprises: a transformer and a switching tube, the transformer having a primary winding and a secondary winding, the primary winding comprising a first winding; the power bus of the switching power supply is connected to the homonymous end of the first winding; the synonym end of the first winding is connected to the first connecting end of the switch end, and the second connecting end of the switch tube is grounded; the secondary winding is output to a load; the soft switching device of the switching power supply comprises: an absorption unit and a resonance unit; the first connecting end of the switching tube is connected to the second connecting end of the switching tube after passing through the absorption unit and the resonance unit to form a resonance absorption loop, so that leakage inductance energy of the transformer is absorbed and resonated at the moment when the switching tube is turned off under the condition that the switching tube is turned off, peak voltage of the switching tube is reduced when the switching tube is turned on in the next period, and soft switching of the switching tube is realized.
In some embodiments, the switching tube is a MOS tube, the first connection end of the switching tube is a drain electrode of the MOS tube, and the second connection end of the switching tube is a source electrode of the MOS tube.
In some embodiments, the absorption unit comprises: a first diode module and a first capacitor module; wherein the synonym end of the first winding is connected to the anode of the first diode module; the cathode of the first diode module is connected to the second connecting end of the first capacitor module; the first connecting end of the first capacitor module is connected to the first connecting end of the resonance unit; the second connecting end of the resonance unit is connected to the first connecting end of the first capacitance module; the second connecting end of the resonance unit is also connected to the second connecting end of the switching tube.
In some embodiments, the soft switching device of the switching power supply further comprises: a second diode module; the second connecting end of the first capacitor module is connected to the anode of the second diode module; and the cathode of the second diode module is connected to the second connecting end of the resonance unit.
In some embodiments, the soft switching device of the switching power supply further comprises: a third diode module; the first connecting end of the first capacitor module is connected to the cathode of the third diode module; the anode of the third diode module is connected to the first connection terminal of the resonance unit.
In some embodiments, the resonant unit includes: an inductance module and a second capacitance module; the inductance module and the second capacitance module are connected in parallel to form an LC resonance circuit; a first connection terminal of the LC resonant circuit as a first connection terminal of the resonant unit; the second connection end of the LC resonance circuit is used as the second connection end of the resonance unit and is connected to the second connection end of the switching tube.
In accordance with another aspect of the present invention, there is provided a switching power supply comprising: the soft switching device of the switching power supply.
In accordance with another aspect of the present invention, in a control method of a switching power supply, the method includes: acquiring the voltage reflected from the secondary winding to the primary winding of the transformer, and recording the voltage as reflected voltage; obtaining leakage inductance voltage of the transformer; determining parameters of components in the absorption unit and the resonance unit according to the reflected voltage and the leakage inductance voltage, so as to set the components in the absorption unit and the resonance unit according to the parameters of the components in the absorption unit and the resonance unit; when the switching tube is turned on, the primary winding of the transformer receives the bus voltage of the power bus to store energy; when the switching tube is turned off, the primary winding of the transformer faces the resonant absorption loop; at the moment of switching tube turn-off, the resonance absorption loop absorbs leakage inductance energy generated by the leakage inductance voltage of the transformer and resonates, so that peak voltage of the switching tube is reduced when the switching tube is turned on in the next period, and soft switching of the switching tube is realized.
In some embodiments, further comprising: obtaining bus voltage of the power bus, obtaining current between a first connecting end of the switching tube and a second connecting end of the switching tube, and obtaining output voltage of the secondary winding; determining a duty ratio signal of a control end of the switching tube according to the bus voltage of the power bus, the current between a first connecting end of the switching tube and a second connecting end of the switching tube and the output voltage of the secondary winding; and controlling the switching-on or switching-off of the switching tube according to the duty ratio signal of the control end of the switching tube.
Therefore, according to the scheme of the invention, through the RCD circuit based on the switching power supply (such as a flyback isolation type switching power supply), the RCD circuit is composed of a resistor module, a capacitor module (such as a capacitor C1) and a diode module (such as a diode D1), an LC resonance circuit is arranged to replace the resistor module in the RCD circuit, so that the leakage inductance voltage of a transformer T in the switching power supply is utilized to supply power for the LC resonance circuit, the resonance of the resonance circuit is enabled to realize the resonance of a switching tube (such as a MOS tube M1) in the switching power supply, so that the switching loss and the switching loss of the switching tube are reduced, and the soft switching of the switching tube is realized by utilizing the energy of the leakage inductance in the switching power supply, so that the switching loss and the switching loss of the switching power supply are reduced.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIG. 1 is a schematic diagram of a soft switching device of a switching power supply according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a soft switching circuit with a novel low-loss power topology according to an embodiment of the present invention, specifically, an improved flyback power topology;
FIG. 3 is a flow chart of an embodiment of a control method of the present invention;
fig. 4 is a flow chart of an embodiment of a duty cycle signal for controlling a switching tube in the method of the present invention.
FIG. 5 is a flow chart of an embodiment of a control method of a soft switching circuit of a novel low loss power topology according to the present invention;
fig. 6 is a schematic diagram of the workflow of the PI controller.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments of the present invention and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In consideration of the fact that the switching power supply adopts a hard switching mode to control the on or off of a switching tube (such as a MOS tube), the voltage and the current generate an included angle to generate loss due to the platform voltage caused by the Miller capacitance at the on time or the off time of the switching tube, and the on loss and the off loss of the switching power supply are large. In addition, the MOSFET (namely MOS tube) is turned off very high at the moment of turning off by the miller capacitance
Figure BDA0004008523150000041
Coupled to v gs On the voltage, the driving voltage of the MOS tube is caused to oscillate and heat during the period of the driving voltage platform, and even the MOS tube is damaged. In addition, energy of leakage inductance in the switching power supply is discharged by the RCD (i.e., residual current device) circuit only as idle work, resulting in energy waste.
For the conduction loss of the switching power supply, once the MOSFET (i.e., the MOS transistor) is selected, the conduction loss of the switching power supply is determined only by the effective current flowing through the MOS transistor and the equivalent internal resistance of the MOSFET, so the conduction loss of the switching power supply is an unchangeable value. Therefore, in order to reduce the loss of the switching power supply, only the on-loss of the switching power supply and the off-loss of the switching power supply can be started, and it is considered that leakage inductance energy of the switching power supply is often wasted as idle work. Therefore, the scheme of the invention provides a technical scheme for realizing soft switching of the switching power supply by using leakage inductance voltage, in particular to a novel soft switching circuit of low-loss power supply topology and a switching circuit control scheme thereof, so that soft switching of a switching tube is realized by using the energy of leakage inductance in the switching power supply, and the switching loss of the switching power supply are reduced.
According to an embodiment of the present invention, there is provided a soft switching device of a switching power supply. Referring to fig. 1, a schematic diagram of an embodiment of the apparatus of the present invention is shown. The switching power supply includes: a transformer and a switching tube, the transformer having a primary winding and a secondary winding, the primary winding comprising a first winding; the power bus of the switching power supply is connected to the homonymous end of the first winding; the synonym end of the first winding is connected to a first connecting end (such as the drain electrode of the MOS tube M1) of the switch end, and a second connecting end (such as the source electrode of the MOS tube M1) of the switch tube is grounded; the secondary winding is output to a load. The soft switching device of the switching power supply comprises: an absorption unit such as an absorption circuit composed of a capacitor C1 and a diode D1, and a resonance unit such as an LC resonance circuit.
The first connecting end of the switching tube is connected to the second connecting end of the switching tube after passing through the absorption unit and the resonance unit to form a resonance absorption loop, so that leakage inductance energy of the transformer is absorbed and resonated at the moment when the switching tube is turned off under the condition that the switching tube is turned off, peak voltage of the switching tube is reduced when the switching tube is turned on in the next period, soft switching of the switching tube is realized, on loss and off loss of the switching power supply are reduced, and utilization rate of the leakage inductance energy of the transformer in the switching power supply is improved.
The soft switching circuit of the novel low-loss power supply topology provided by the scheme of the invention adopts the frequently wasted leakage inductance voltage to provide the resonant network and realize the soft switching of the switching power supply, and realizes the soft switching of the switching tube by utilizing the energy of the leakage inductance, thereby reducing the turn-on loss and improving the performance of the switching power supplyThe utilization efficiency of the energy of the leakage inductance can also prevent the switching tube from being turned off very high by the Miller capacitor at the moment of turning off
Figure BDA0004008523150000051
Is coupled to the voltage between the first connection of the switching tube and the second connection of the switching tube, thereby avoiding the risk of the driving voltage oscillating during the platform voltage and heating up or even damaging the switching tube. By utilizing the soft switching technology, the stress of the switching tube of the switching power supply is relieved, the effect of protecting the switching tube is achieved, and the working stability of the switching power supply can be improved.
In some embodiments, the switching tube is a MOS tube, the first connection end of the switching tube is a drain electrode of the MOS tube, and the second connection end of the switching tube is a source electrode of the MOS tube.
According to the scheme of the invention, the leakage inductance voltage which is always wasted is provided for the resonant network and the soft switch of the switching power supply is realized, the soft switch of the MOS tube is realized by utilizing the energy of the leakage inductance, the switching-on loss is reduced, the utilization efficiency of the energy of the leakage inductance is improved, and the MOS tube can be prevented from switching off very high peak voltage by the Miller capacitor at the switching-off moment
Figure BDA0004008523150000052
A voltage v coupled between the gate of the MOS transistor and the source of the MOS transistor gs The voltage is high, so that the danger that the driving voltage oscillates during the voltage of the platform to heat and even damage the MOS tube is avoided. By utilizing the soft switching technology, the stress of the MOS tube of the switching power supply is lightened, the effect of protecting the switching tube is achieved, and the working stability of the switching power supply can be improved. The MOS tube has a Miller capacitance, so that a stage of rising the gate-source voltage of the MOS tube has a period of platform time, and the voltage value is unchanged in the period of time, so that the period of time is called a period of platform voltage.
Specifically, fig. 2 is a schematic structural diagram of an embodiment of a soft switching circuit of a novel low-loss power topology according to the present invention, specifically an improved flyback power topology. In the example shown in fig. 2, the power supply energy is rectified and filtered through the mains supply input to integrate alternating current into direct current to act on the power bus, the MOS transistor M1 is a MOSFET for switching adjustment output, the dummy load simulates electric equipment, the control IC monitors the bus voltage, current and condition of the output voltage VO, and controls the duty ratio of the switching transistor (such as the MOS transistor) to stabilize the output voltage of the switching power supply.
In some embodiments, the absorption unit comprises: the first diode module, such as diode D1, and the first capacitor module, such as capacitor C1. Wherein the synonym end of the first winding is connected to the anode of the first diode module. And the cathode of the first diode module is connected to the second connecting end of the first capacitor module. The first connecting end of the first capacitor module is connected to the first connecting end of the resonance unit. The second connecting end of the resonance unit is connected to the first connecting end of the first capacitance module. The second connecting end of the resonance unit is also connected to the second connecting end of the switching tube. In the example shown in fig. 2, the diode D1 prevents the parasitic inductance of the transformer T from resonating with the absorption capacitance.
In some embodiments, the soft switching device of the switching power supply further comprises: a second diode module, such as diode D2. The second connecting end of the first capacitor module is connected to the anode of the second diode module. And the cathode of the second diode module is connected to the second connecting end of the resonance unit. In the example shown in fig. 2, diode D2 isolates the cavity of the cavity tank from the tank circuit to prevent mutual interference.
In some embodiments, the soft switching device of the switching power supply further comprises: a third diode module, such as diode D3. The first connecting end of the first capacitor module is connected to the cathode of the third diode module. The anode of the third diode module is connected to the first connection terminal of the resonance unit. In the example shown in fig. 2, diode D3 prevents the power bus from charging the cavity of the cavity absorption loop.
In some embodiments, the resonant unit includes: an inductance module, such as inductance L1, and a second capacitance module, such as capacitance C2. The inductance module and the second capacitance module are connected in parallel to form an LC resonance circuit. The first connection terminal of the LC resonant circuit is used as the first connection terminal of the resonant unit. The second connection end of the LC resonance circuit is used as the second connection end of the resonance unit and is connected to the second connection end of the switching tube.
Specifically, as shown in fig. 2, the soft switching circuit of the novel low-loss power supply topology provided by the scheme of the invention comprises: transformer T, MOS transistor M1, inductor L1, capacitor C2, diode D1, diode D2, diode D3, driving resistor, ground resistor, and controller (e.g., control IC). The primary windings of the transformer T are two groups, namely a first winding and a second winding, a power bus of the switching power supply is connected to the homonymous end of the first winding, and the heteronymous end of the first winding is connected to the drain electrode of the MOS tube M1. The source electrode of the MOS tube M1 is grounded after passing through a grounding resistor. The same-name end of the first winding is connected to the first end of the capacitor C1, the second end of the capacitor C1 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the different-name end of the first winding. The same-name end of the first winding is also connected to the cathode of a diode D3, the anode of the diode D3 is connected to the first end of an inductor L1 and a capacitor C2 which are connected in parallel, and the second end of the inductor L1 and the capacitor C2 which are connected in parallel is connected to the source electrode of the MOS tube M1. The first ends of the parallel inductor L1 and the capacitor C2 are also connected to the drain of the MOS transistor M1. The second ends of the parallel inductor L1 and capacitor C2 are also connected to the cathode of the diode D2, and the anode of the diode D2 is connected to the cathode of the diode D1. The synonym terminal of the secondary winding of the transformer T is connected to the anode of the diode. The cathode of the diode is connected with the same-name end of the secondary winding of the transformer T through a capacitor on the one hand and the first end of the dummy load on the other hand. The same-name end of the secondary winding of the transformer T is connected to the second end of the dummy load. The controller receives the busbar voltage VP detected by the synonym end of the first winding, the switching current detected by the grounding resistor connected with the source electrode of the MOS tube M1 and the output voltage VO detected by the dummy load, and determines a driving signal for driving the MOS tube M1. The driving signal output by the controller is input to the grid electrode of the MOS tube M1 after passing through the driving resistor.
In the example shown in fig. 2, an LC resonant structure formed by combining an inductance L1 and a capacitance C2 in an RCD circuit of a switching power supply forms a resonant cavity absorption loop, and the original wasted leakage inductance energy is supplied to an LC resonant cavity.
By adopting the technical scheme of the invention, the RCD circuit based on the switching power supply (such as a flyback isolation type switching power supply) consists of a resistor module, a capacitor module (such as a capacitor C1) and a diode module (such as a diode D1), and an LC resonance circuit is arranged to replace the resistor module in the RCD circuit so as to supply power to the LC resonance circuit by using the leakage inductance voltage of a transformer T in the switching power supply, so that the resonance of the resonance circuit realizes the resonance of a switching tube (such as a MOS tube M1) in the switching power supply to reduce the on-off loss and the on-off loss of the switching tube, thereby realizing the soft switching of the switching tube by using the energy of the leakage inductance in the switching power supply and reducing the on-off loss and the on-off loss of the switching power supply.
There is also provided, in accordance with an embodiment of the present invention, a switching power supply corresponding to a soft switching device of a switching power supply. The switching power supply may include: the soft switching device of the switching power supply.
Since the processing and functions implemented by the switching power supply of the present embodiment basically correspond to the embodiments, principles and examples of the device, the description of the present embodiment is not exhaustive, and reference may be made to the related description in the foregoing embodiments, which is not repeated herein.
By adopting the technical scheme of the invention, the RCD circuit based on the switching power supply (such as a flyback isolation type switching power supply) consists of a resistor module, a capacitor module (such as a capacitor C1) and a diode module (such as a diode D1), and an LC resonance circuit is arranged to replace the resistor module in the RCD circuit so as to utilize the leakage inductance voltage of a transformer T in the switching power supply to supply power to the LC resonance circuit, so that the resonance of the resonance circuit realizes the resonance of a switching tube (such as a MOS tube M1) in the switching power supply to reduce the on loss and the off loss of the switching tube, so that the stress of a switching device (such as the MOS tube) of the switching power supply is relieved, the effect of protecting the switching tube is achieved, and the working stability of the switching power supply is improved.
According to an embodiment of the present invention, there is further provided a control method of a switching power supply corresponding to the switching power supply, as shown in fig. 3, which is a schematic flow chart of an embodiment of the method of the present invention. The control method of the switching power supply may include: step S110 to step S140.
At step S110, the voltage reflected from the secondary winding to the primary winding of the transformer is acquired and is denoted as reflected voltage. And obtaining the leakage inductance voltage of the transformer.
At step S120, parameters of components in the absorption unit and the resonance unit are determined according to the reflected voltage and the leakage inductance voltage, so as to set the components in the absorption unit and the resonance unit according to the parameters of the components in the absorption unit and the resonance unit.
At step S130, with the switching tube turned on, the primary winding of the transformer receives a bus voltage storage energy of the power bus.
At step S140, the primary winding of the transformer is directed towards the resonant tank with the switching tube turned off. At the moment of switching tube turn-off, the resonance absorption loop absorbs leakage inductance energy generated by the leakage inductance voltage of the transformer and resonates, so that peak voltage of the switching tube is reduced when the switching tube is turned on in the next period, and soft switching of the switching tube is realized.
Specifically, fig. 5 is a schematic flow chart of an embodiment of a control method of a soft switching circuit of a novel low-loss power topology according to the present invention. As shown in fig. 5, a control method of a soft switching circuit of a novel low-loss power supply topology according to the present invention includes:
and 11, rectifying and filtering the alternating current and outputting the alternating current to a power bus.
Step 12, under the condition that the MOS transistor M1 is turned on, the primary winding of the transformer T stores energy.
Step 13, under the condition that the MOS tube M1 is turned off, the transformer T absorbs the loop through the primary winding to release energy to the resonant cavity. At the moment when the MOS tube M1 is turned off, the resonant cavity of the resonant cavity absorption loop absorbs leakage inductance energy of the transformer T1 and resonates through the resonant circuit. The resonant circuit can resonate within a small amplitude range in advance by calculating parameters of resonant components (such as the inductor L1 and the capacitor C2) in the selected resonant circuit.
The selection of the resonant cavity inductance (e.g., inductance L1), the resonant capacitance (e.g., capacitance C2) and the absorption capacitance (e.g., capacitance C1) is calculated as: bus voltage V IN ＝1.414×V ac ，V ac Is an ac input voltage.
Figure BDA0004008523150000091
V OR For the secondary reflection of the transformer T to the primary voltage, np is the primary smash number, ns is the secondary smash number, vo is the output voltage, V F Is a diode drop. When the switch tube (such as MOS tube M1) is turned off, the leakage inductance energy is absorbed by the capacitor C1, and the voltage between the resistor R1 (i.e. equivalent resistance of resonant cavity) in the absorption loop and the network of the capacitor C1 is V OR +V PEAK (i.e., the sum of the reflected voltage and the leakage inductance voltage), V PEAK Is leakage inductance voltage. When the switch tube (such as MOS tube M1) is turned on, the capacitor C1 discharges via the resistor R1 to turn V before the switch is turned off in the next period PEAK Since the reset is performed, the discharge time is controlled strictly, and R1C1 having a discharge time constant of 2 to 4 times is taken here, where R1 is the resistance value of the resistor R1, and C1 is the capacitance value of the capacitor C1. From an energy perspective, there is the formula (1): w (W) c1 +W l ＝W c2 Wherein W is c1 Is the original energy of the capacitor C1, W l Energy supplied to leakage inductance, W c2 The total energy across the capacitor.
The expansion of the formula (1) is as follows:
Figure BDA0004008523150000092
wherein L is leakage inductance voltage, I is source current, C is capacitance value of capacitor C1, after leakage inductance energy is given to capacitor C1, voltage of capacitor C1 increases by delta, namely voltage change delta V, voltage V at two ends of voltage capacitor is obtained by the formula (2)>
Figure BDA0004008523150000093
Can be obtained by combining the above
Figure BDA0004008523150000094
f is the switching frequency, and in practical application, the capacitance is larger, and the resistance is smaller to satisfy the requirement, because of considering the influence of other parasitic parameters, in this circuit, R1 is the equivalent total impedance value of the parallel resonant cavity. Inductance impedance X L =ωl, where ω=2pi f, capacitive reactance is +.>
Figure BDA0004008523150000095
C 2 Is the capacitance of capacitor C2, thus equivalent impedance +.>
Figure BDA0004008523150000096
Therefore, the inductance value can be fixed at first and then the capacitance value can be combined and matched during the value selection.
In step 14, the voltage at two ends of the MOS transistor M1 (i.e., the drain of the MOS transistor M1 and the source of the MOS transistor M1) is clamped by the resonant capacitor (e.g., the capacitor C2) at a small voltage value, and the peak voltage is greatly reduced when the MOS transistor M1 is turned on again in the next cycle.
Wherein, the composition of spike voltage: the peak voltage is generated by the primary leakage inductance of the high-frequency transformer, and is superposed with the direct-current high voltage and the secondary induced voltage and then applied to a switching tube (such as a MOS tube M1), if the voltage exceeds the drain-source voltage, breakdown damage occurs, so that the switching tube is used for derating the reference chip manual at the beginning of design, wherein the voltage applied to the drain-source voltage of the switching tube is composed of the following parts by a formula: spike voltage V DS ＝V IN +V OR +V PEAK Wherein V is IN Is the bus voltage, V OR Is a reflected voltage, V PEAK Is leakage inductance voltage.
Referring to the example shown in fig. 5, when the switching tube (e.g., MOS tube M1) is turned on, a power supply loop of the switching power supply is established, and the energy of the power supply bus stores the energy for the primary coil of the transformer T1. When the switch tube (such as MOS tube M1) is turned off, the switch tube is flybackThe power supply topology structure is that energy is transmitted backwards at the moment, and meanwhile reverse voltage is transmitted from the secondary winding of the transformer T to the primary winding of the transformer T through a coil (namely, the connection position of the primary winding of the transformer T1 and a bus), leakage inductance voltage of the transformer T is overlapped, so that the diode D1 is conducted, the absorption and resonance circuit (namely, the resonant cavity absorption loop) starts to work, and leakage inductance current of the transformer T flows through the diode D1 to charge the capacitor C1. When the switch tube (such as the MOS tube M1) is turned on again, the absorption capacitor (such as the capacitor C1) supplies power to the resonant cavity (namely the resonant circuit formed by the capacitor C2 and the inductor L1) to start resonance and control the resonant cavity to oscillate within a very small amplitude range, when the switch tube (such as the MOS tube M1) is turned off, the drain-source voltage of the MOS tube M1 is clamped in a very small voltage range by the resonant capacitor (such as the capacitor C2), at the moment, the voltage is approximately ZVS (zero voltage switch) to turn off the MOS tube M1, the ZVS turn-off can be realized in the following period, and the situation that the MOS tube M1 is turned off at the moment and is turned off very high by the Miller capacitor is avoided
Figure BDA0004008523150000101
Coupled to v gs The voltage is applied so as to avoid the risk of heating and even damaging the switching tube due to oscillation of the driving voltage during the platform voltage, and greatly reduce the turn-off loss.
In some embodiments, the method for controlling a switching power supply according to the present invention further includes: and controlling the duty ratio signal of the switching tube.
The following is a schematic flow chart of an embodiment of the duty cycle signal of the control switch in the method of the present invention in connection with fig. 4, which further describes a specific process of controlling the duty cycle signal of the control switch, including: step S210 to step S230.
Step S210, obtaining a bus voltage of the power bus, obtaining a current between a first connection end of the switching tube and a second connection end of the switching tube, and obtaining an output voltage of the secondary winding.
Step S220, determining a duty cycle signal of the control end of the switching tube according to the bus voltage of the power bus, the current between the first connection end of the switching tube and the second connection end of the switching tube, and the output voltage of the secondary winding.
Step S230, controlling the on or off of the switching tube according to the duty ratio signal of the control end of the switching tube.
Specifically, fig. 6 is a schematic diagram of the workflow of the PI controller. As shown in fig. 6, the controller of the switching power supply may be a PI controller, and the workflow of the PI controller includes:
step 21, reading the bus voltage VP of the power bus, and current sampling data (such as the switch current detected at the ground resistor connected from the source of the MOS transistor M1) of the power bus.
Step 22, the PI regulator regulates the output voltage VO of the switching power supply by regulating the duty ratio of the MOS transistor M1 according to the bus voltage VP and the current sampling data of the power supply bus.
Step 23, judging whether the output voltage VO of the switching power supply is within the calculated regulation range according to feedback of the output voltage VO of the switching power supply, and sequentially performing cycle control.
Referring to the example shown in fig. 6, voltage and current are collected on the power supply main loop of the switching power supply, whether overvoltage, undervoltage and overcurrent are detected by the internal circuit of the control IC chip, whether the circuit continues to work normally is determined, meanwhile, the output voltage V0 is fed back to the control IC through the controllable precision voltage stabilizing source TL431 to be a difference value with a set voltage value, the PWM duty ratio of the MOS transistor M1 is controlled through the PI regulator, the output voltage of the switching power supply is continuously adjusted, and finally, the deviation voltage between the output voltage of the switching power supply and the target voltage approaches to a zero value, so as to achieve the effect of stable output of the switching power supply (such as a flyback isolated switching power supply). According to experimental data, under the condition that the on-resistance of the MOS tube M1 is unchanged, the overall loss is obviously reduced, and the heating of the MOS tube M1 is greatly reduced.
Since the processes and functions implemented by the method of the present embodiment substantially correspond to the embodiments, principles and examples of the switching power supply described above, the descriptions of the present embodiment are not exhaustive, and reference may be made to the related descriptions of the foregoing embodiments, which are not repeated herein.
By adopting the technical scheme of the embodiment, the RCD circuit is composed of a resistor module, a capacitor module (such as a capacitor C1) and a diode module (such as a diode D1) based on a switching power supply (such as a flyback isolation type switching power supply), an LC resonance circuit is arranged to replace the resistor module in the RCD circuit, so that leakage inductance voltage of a transformer T in the switching power supply is utilized to supply power to the LC resonance circuit, resonance of a switching tube (such as a MOS tube M1) in the switching power supply is realized by resonance of the resonance circuit, on-off loss and on-off loss of the switching tube are reduced, soft switching of a MOSFET is realized by utilizing energy of leakage inductance, on-loss is reduced, and energy utilization efficiency of the leakage inductance is improved.
In summary, it is readily understood by those skilled in the art that the above-described advantageous ways can be freely combined and superimposed without conflict.
The above description is only an example of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims (9)

1. A soft switching device for a switching power supply, the switching power supply comprising: a transformer and a switching tube, the transformer having a primary winding and a secondary winding, the primary winding comprising a first winding; the power bus of the switching power supply is connected to the homonymous end of the first winding; the synonym end of the first winding is connected to the first connecting end of the switch end, and the second connecting end of the switch tube is grounded; the secondary winding is output to a load; the soft switching device of the switching power supply comprises: an absorption unit and a resonance unit; the first connecting end of the switching tube is connected to the second connecting end of the switching tube after passing through the absorption unit and the resonance unit to form a resonance absorption loop, so that leakage inductance energy of the transformer is absorbed and resonated at the moment when the switching tube is turned off under the condition that the switching tube is turned off, peak voltage of the switching tube is reduced when the switching tube is turned on in the next period, and soft switching of the switching tube is realized.
2. The soft switching device of a switching power supply according to claim 1, wherein the switching tube is a MOS tube, a first connection end of the switching tube is a drain electrode of the MOS tube, and a second connection end of the switching tube is a source electrode of the MOS tube.
3. The soft switching device of a switching power supply according to claim 1, wherein the absorption unit comprises: a first diode module and a first capacitor module; wherein,,
the synonym end of the first winding is connected to the anode of the first diode module; the cathode of the first diode module is connected to the second connecting end of the first capacitor module; the first connecting end of the first capacitor module is connected to the first connecting end of the resonance unit; the second connecting end of the resonance unit is connected to the first connecting end of the first capacitance module; the second connecting end of the resonance unit is also connected to the second connecting end of the switching tube.
4. A soft switching device of a switching power supply according to claim 3, further comprising: a second diode module; wherein,,
the second connecting end of the first capacitor module is connected to the anode of the second diode module; and the cathode of the second diode module is connected to the second connecting end of the resonance unit.
5. A soft switching device of a switching power supply according to claim 3, further comprising: a third diode module; wherein,,
the first connecting end of the first capacitor module is connected to the cathode of the third diode module; the anode of the third diode module is connected to the first connection terminal of the resonance unit.
6. A soft switching device of a switching power supply according to any one of claims 1 to 5, characterized in that the resonance unit comprises: an inductance module and a second capacitance module; wherein,,
the inductance module and the second capacitance module are connected in parallel to form an LC resonance circuit; a first connection terminal of the LC resonant circuit as a first connection terminal of the resonant unit; the second connection end of the LC resonance circuit is used as the second connection end of the resonance unit and is connected to the second connection end of the switching tube.
7. A switching power supply, comprising: a soft switching device of a switching power supply as claimed in any one of claims 1 to 6.
8. A control method of the switching power supply according to claim 7, comprising:
acquiring the voltage reflected from the secondary winding to the primary winding of the transformer, and recording the voltage as reflected voltage; obtaining leakage inductance voltage of the transformer;
determining parameters of components in the absorption unit and the resonance unit according to the reflected voltage and the leakage inductance voltage, so as to set the components in the absorption unit and the resonance unit according to the parameters of the components in the absorption unit and the resonance unit;
when the switching tube is turned on, the primary winding of the transformer receives the bus voltage of the power bus to store energy;
when the switching tube is turned off, the primary winding of the transformer faces the resonant absorption loop; at the moment of switching tube turn-off, the resonance absorption loop absorbs leakage inductance energy generated by the leakage inductance voltage of the transformer and resonates, so that peak voltage of the switching tube is reduced when the switching tube is turned on in the next period, and soft switching of the switching tube is realized.
9. The control method of a switching power supply according to claim 8, characterized by further comprising:
obtaining bus voltage of the power bus, obtaining current between a first connecting end of the switching tube and a second connecting end of the switching tube, and obtaining output voltage of the secondary winding;
determining a duty ratio signal of a control end of the switching tube according to the bus voltage of the power bus, the current between a first connecting end of the switching tube and a second connecting end of the switching tube and the output voltage of the secondary winding;
and controlling the switching-on or switching-off of the switching tube according to the duty ratio signal of the control end of the switching tube.
CN202211640061.5A 2022-12-20 2022-12-20 Soft switching device of switching power supply, switching power supply and control method of switching power supply Pending CN116073662A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116827140A (en) * 2023-08-30 2023-09-29 深圳市恒运昌真空技术有限公司 Soft switch resonant converter

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116827140A (en) * 2023-08-30 2023-09-29 深圳市恒运昌真空技术有限公司 Soft switch resonant converter
CN116827140B (en) * 2023-08-30 2023-12-19 深圳市恒运昌真空技术有限公司 Soft switch resonant converter

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