CN111049368A - Soft switch control method, totem-pole bridgeless circuit and totem-pole bridgeless system - Google Patents
Soft switch control method, totem-pole bridgeless circuit and totem-pole bridgeless system Download PDFInfo
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
- H02M1/4208—Arrangements for improving power factor of AC input
- H02M1/4233—Arrangements for improving power factor of AC input using a bridge converter comprising active switches
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
- H02M1/0054—Transistor switching losses
- H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
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- 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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Abstract
The invention relates to the technical field of power electronics, and discloses a soft switch control method, a totem-pole bridgeless circuit and a totem-pole bridgeless system, wherein the totem-pole bridgeless circuit comprises at least two bridge arms, one of the bridge arms comprises a third switching tube, a first current transformer, a fourth switching tube and a second current transformer which are connected in series, when the voltage polarity change of the voltage at two ends of a secondary winding of the first current transformer is detected, a period of time is delayed, the third switching tube is continuously conducted within the period of time to enable the current flowing through the third switching tube to be reversed, the third switching tube is turned off after the period of time, and the fourth switching tube is conducted after the further period of time is delayed when the third switching tube is turned off. According to the embodiment of the invention, the reverse current flowing through the third switching tube is used for charging the junction capacitor of the third switching tube and discharging the junction capacitor of the fourth switching tube to be conducted, so that zero-voltage switching-on of the switching tubes is realized, the switching-on loss of the switching tubes is reduced, and the power supply efficiency is improved.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a soft switch control method, a totem-pole bridgeless circuit and a totem-pole bridgeless system.
Background
The main trends of power electronic devices are miniaturization, light weight, high efficiency, and low cost. The PFC circuit is divided into two categories, namely a bridge PFC circuit and a bridgeless PFC circuit, and the traditional bridge PFC circuit has many conducting devices, large switching loss and on-state loss and can not be applied to occasions with medium and high power. Compared with the traditional bridge PFC circuit, the bridge-free PFC circuit has fewer conducting devices and less on-state loss, and is beneficial to improving the power density.
The control method of the totem-pole bridgeless PFC circuit can be divided into two types according to the working mode of PFC inductive current, namely an inductive current Continuous Control Method (CCM) and an inductive current critical continuous control method (CRM), and the conventional totem-pole bridgeless PFC control circuit generally adopts a CCM mode to realize power factor correction.
In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art: in a CCM mode, a power switch tube is switched on hard, the switching loss is large, and the problems of loss and EMI (electro-magnetic interference) caused by reverse recovery of a parasitic body diode of the power switch tube exist, so that the efficiency of a totem-pole bridgeless PFC circuit is low, and the power density is limited.
Disclosure of Invention
In order to solve the above technical problems, embodiments of the present invention provide a soft switch control method, a totem-pole bridgeless circuit, and a totem-pole bridgeless system, which can solve the technical problems of low power density or low efficiency of a totem-pole bridgeless PFC circuit in the related art.
The embodiment of the invention provides the following technical scheme for solving the technical problems:
in a first aspect, an embodiment of the present invention provides a soft switching control method applied to a totem-pole bridgeless circuit, where the totem-pole bridgeless circuit includes a first bridge arm and a second bridge arm connected in parallel between a first parallel connection point and a second parallel connection point, the first bridge arm includes a first switching tube and a second switching tube connected in series in the same direction, the second bridge arm includes a third switching tube and a fourth switching tube connected in series in the same direction, a connection point between the first switching tube and the second switching tube is a first series connection point, a connection point between the third switching tube and the fourth switching tube is a second series connection point, a power supply and an inductor are connected in series between the first series connection point and the second series connection point, a capacitor and a load are further connected in parallel between the first parallel connection point and the second parallel connection point, a first current transformer is connected in series between the first parallel connection point and the second series connection point, a second current transformer is connected in series between the second parallel connection point and the second series connection point, and the method comprises the following steps: after the fourth switching tube is turned off, when voltage polarity change of voltages at two ends of a secondary winding of the second current transformer is detected, delaying a first preset time, and after the first preset time, turning on the third switching tube to convert a first current from a body diode flowing through the third switching tube into a channel flowing through the third switching tube; when voltage polarity change of voltages at two ends of a secondary winding of the first current transformer is detected, delaying a second preset time, and continuing to conduct the third switching tube within the second preset time so as to enable a second current to flow through the third switching tube, wherein the second current is opposite to the first current in flow direction, and the second current is used for charging a junction capacitor of the third switching tube and discharging the junction capacitor of the fourth switching tube to be conducted; and after the second preset time period, the third switching tube is turned off, the third preset time period is delayed when the third switching tube is turned off, and the fourth switching tube is turned on after the third preset time period.
In a second aspect, an embodiment of the present invention provides a totem-pole bridgeless circuit, including a first bridge arm and a second bridge arm connected in parallel between a first parallel connection point and a second parallel connection point, where the first bridge arm includes a first switching tube and a second switching tube connected in series in the same direction, the second bridge arm includes a third switching tube and a fourth switching tube connected in series in the same direction, a connection point between the first switching tube and the second switching tube is a first series connection point, a connection point between the third switching tube and the fourth switching tube is a second series connection point, a power supply and an inductor are connected in series between the first series connection point and the second series connection point, a capacitor and a load are further connected in parallel between the first parallel connection point and the second parallel connection point, and a first current transformer is connected in series between the first parallel connection point and the second series connection point, a second current transformer is connected in series between the second parallel connection point and the second series connection point, and the totem-pole bridgeless circuit further includes: the first voltage polarity detection circuit is connected with the first current transformer and is used for detecting the voltage polarity of the voltage at two ends of the secondary winding of the first current transformer; the second voltage polarity detection circuit is connected with the second current transformer and is used for detecting the voltage polarity of the voltage at the two ends of the secondary winding of the second current transformer; the controller is respectively connected with the first voltage polarity detection circuit, the second voltage polarity detection circuit, the third switch tube and the fourth switch tube and is used for controlling the switching state of the third switch tube or the fourth switch tube according to the voltage polarity of the voltage at two ends of the secondary winding of the first current transformer or the voltage polarity of the voltage at two ends of the secondary winding of the second current transformer; wherein the controller includes: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method as described above.
Optionally, the first current transformer includes a first primary winding and at least one first secondary winding, and the second current transformer includes a second primary winding and at least one second secondary winding.
Optionally, the first voltage polarity detection circuit includes: the first transformer magnetic resetting unit is connected with the first current transformer and is used for carrying out magnetic resetting on the first current transformer when the current flowing through the third switching tube is in a zero crossing point state; and the first voltage polarity comparison unit is respectively connected with the first current transformer and the first transformer magnetic reset unit and is used for detecting the voltage polarity of the first secondary winding after the first current transformer is magnetically reset.
Optionally, the second voltage polarity detection circuit includes: the second transformer magnetic resetting unit is connected with the second current transformer and is used for performing magnetic resetting on the second current transformer when the fourth switching tube is turned off; and the second voltage polarity comparison unit is respectively connected with the second current transformer and the second transformer magnetic reset unit and is used for detecting the voltage polarity of the second secondary winding after the second current transformer is magnetically reset.
Optionally, the controller is a complex programmable logic device CPLD, a field programmable gate array FPGA, a digital signal processor DSP, or a microcontroller MCU.
Optionally, the third switching tube and the fourth switching tube are N-channel metal-oxide semiconductor field effect transistors MOSFET or insulated gate bipolar transistors IGBT.
In a third aspect, embodiments of the present invention provide a totem-pole bridgeless system, including the totem-pole bridgeless circuit described above.
In various embodiments of the present invention, when detecting a voltage polarity change of the voltage across the secondary winding of the first current transformer, delaying a period of time, and continuing to turn on the third switching tube during the period of time to reverse the current flowing through the third switching tube, after the period of time, turning off the third switching tube, and when turning off the third switching tube, turning on the fourth switching tube after delaying a further period of time. According to the embodiment of the invention, the reverse current flowing through the third switching tube is used for charging the junction capacitor of the third switching tube and discharging the junction capacitor of the fourth switching tube to be conducted, so that zero-voltage switching-on of the switching tubes is realized, the switching-on loss of the switching tubes is reduced, and the power supply efficiency is improved.
Drawings
The embodiments are illustrated by way of example only in the accompanying drawings, in which like reference numerals refer to similar elements and which are not to be construed as limiting the embodiments, and in which the figures are not to scale unless otherwise specified.
Fig. 1 is a schematic circuit diagram of a totem-pole bridgeless circuit according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart illustrating a soft switching control method according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a controller of FIG. 1;
fig. 4 is a schematic circuit diagram of a totem-pole bridgeless circuit according to another embodiment of the present invention;
fig. 5 is a schematic circuit diagram of a totem-pole bridgeless circuit according to yet another embodiment of the present invention;
fig. 6 is a schematic diagram illustrating an operating state of a totem-pole bridgeless circuit according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a totem-pole bridgeless circuit according to yet another embodiment of the present invention;
FIG. 8 is a schematic diagram of a totem-pole bridgeless circuit according to yet another embodiment of the present invention;
fig. 9 is a schematic diagram of an operating state of a totem-pole bridgeless circuit according to another embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As an aspect of the embodiments of the present invention, there is provided a totem pole bridgeless circuit, as shown in fig. 1, in which a totem pole bridgeless circuit 100 includes a first arm 10 and a second arm 20 connected in parallel between a first parallel connection point 1A and a second parallel connection point 1B, the first arm 10 includes a first switching tube Q1 and a second switching tube Q2 connected in series in the same direction, the second arm 20 includes a third switching tube Q3 and a fourth switching tube Q4 connected in series in the same direction, a connection point between the first switching tube Q1 and the second switching tube Q2 is a first series connection point 2A, a connection point between the third switching tube Q3 and the fourth switching tube Q4 is a second series connection point 2B, a power source AC and an inductor L1 are connected in series between the first series connection point 2A and the second series connection point 2B, a capacitor 30 and a load 40 are connected in parallel between the first parallel connection point 1A and the second parallel connection point 1B, a first current transformer CT1 is connected in series between the first parallel connection point 1A and the second series connection point 2B, and a second current transformer CT2 is connected in series between the second parallel connection point 1B and the second series connection point 2B.
In some embodiments, the first switch Q1 and the second switch Q2 may be diodes, MOSFETs, IGBTs, bipolar transistors or the like, and the first switch Q1 and the second switch Q2 are diodes, for example.
In some embodiments, the third switching transistor Q3 and the fourth switching transistor Q4 may be metal-oxide semiconductor field effect transistors MOSFET or insulated gate bipolar transistors IGBT, which may be GaN, SiC, or the like, and the N-channel MOSFET is exemplified as the third switching transistor Q3 and the fourth switching transistor Q4.
Referring to fig. 2, fig. 2 is a flow chart illustrating a soft switch control method according to an embodiment of the present invention. The soft switching control method is applied to the totem-pole bridgeless circuit 100 as described above, and as shown in fig. 2, the soft switching control method includes:
step S10, after the fourth switching tube Q4 is turned off, when it is detected that the voltage polarity of the voltage at the two ends of the secondary winding of the second current transformer CT2 changes, delaying a first preset time period, and after the first preset time period, turning on the third switching tube Q3, so that the first current is converted from the body diode flowing through the third switching tube Q3 to the channel flowing through the third switching tube Q3;
when the L-port of the power supply AC is positive, the fourth switching tube Q4 is turned on, and the third switching tube Q3 is turned off, the power supply AC, the inductor L1, the channel of the fourth switching tube Q4, the second switching tube Q2, and the power supply AC form a current loop.
After the fourth switching tube Q4 is turned off, the power supply AC, the inductor L1, the body diode of the third switching tube Q3, the capacitor 30 and the load 40, the second switching tube Q2 and the power supply AC form a current loop, when the voltage polarity change of the voltage at the two ends of the secondary winding of the second current transformer CT2 is detected, a first preset time is delayed, and after the first preset time, the third switching tube Q3 is turned on, so that the power supply AC, the inductor L1, the channel of the third switching tube Q3, the capacitor 30 and the load 40, the second switching tube Q2 and the power supply AC form a current loop, and the first current flows through the current loop.
When the voltage polarity change of the voltage at the two ends of the secondary winding of the second current transformer CT2 is detected, the first preset time period is delayed, and after the first preset time period, the third switching tube Q3 is turned on, so that the current flowing through the body diode of the third switching tube Q3 is converted to flow through the channel of the third switching tube Q3, and the conduction loss of the third switching tube Q3 is effectively reduced.
Step S20, when detecting that the voltage polarity of the voltage at the two ends of the secondary winding of the first current transformer changes, delaying a second preset time, and continuing to conduct the third switch tube Q3 within the second preset time, so that a second current flows through the third switch tube Q3, wherein the second current is opposite to the first current in flow direction, and is used for charging the junction capacitor of the third switch tube and discharging the junction capacitor of the fourth switch tube to be conducted;
in step S30, after a second preset time period, the third switching tube Q3 is turned off, and when the third switching tube Q3 is turned off, the third preset time period is delayed, and after the third preset time period, the fourth switching tube Q4 is turned on.
Within a third preset time period, the junction capacitor of the fourth switching tube Q4 to be conducted is discharged while the junction capacitor of the third switching tube Q3 is charged, and the fourth switching tube Q4 is conducted after the third preset time period, so that Zero Voltage Switching (ZVS) or Valley Switching (VS) of the fourth switching tube Q4 is realized, and further, the switching loss of the fourth switching tube Q4 is effectively reduced.
Under the continuous mode (CCM) of the inductive current, the switching tube is switched on hard, and after one switching tube is switched off, the other switching tube is switched on, on one hand, when the switching tube works on hard, the current rise and the voltage fall of the switching device are carried out simultaneously, the overlapping of voltage and current waveforms generates the switching loss, and the switching loss is increased rapidly along with the increase of the switching frequency; on the other hand, because the reverse recovery time of the switching tubes is relatively long (the reverse recovery characteristics of the switching tubes depend on the parasitic body diode in the switching tubes), when one switching tube is in a reverse recovery state for a long time after being turned off, the generated reverse recovery current will have an adverse effect on the other switching tube which is just turned on.
In view of the above technical drawbacks, in the present embodiment, by detecting a change in voltage polarity of the voltage across the secondary winding of the second current transformer CT2, delaying a first preset time period, turning on the third switching tube Q3 to convert the current from the body diode flowing through the third switching tube to the channel flowing through the third switching tube, delaying a second preset time period and continuing to turn on the third switching tube Q3 for the second preset time period when a change in voltage polarity of the voltage across the secondary winding of the first current transformer is detected, reversing the current flowing through the third switching tube Q3, turning off the third switching tube Q3 for the second preset time period, delaying a third preset time period when the third switching tube is turned off, and turning on the fourth switching tube Q4 for the third preset time period, discharging the junction capacitance of the fourth switching tube Q4 to be turned on while charging the junction capacitance of the third switching tube Q3 for the third preset time period, the inductor current works in a CRM mode, so that ZVS or VS within a full-alternating-current input voltage and a full-load range can be realized, the switching-on loss of the switching tube is effectively reduced, meanwhile, as the reverse current flowing through the third switching tube Q3 does not flow through the body diode of the third switching tube Q3 but flows through the channel of the third switching tube Q3, the conduction loss of the switching tube is reduced, and the problem of loss caused by reverse recovery of the body diode parasitic in the switching tube is solved, therefore, the embodiment can meet the requirements of high power density or high efficiency.
The soft switch control method of the above embodiment may be implemented by a hardware platform, or may be implemented by a corresponding software system. For example, the soft-switching control method may be implemented in any suitable type of electronic device having a processor with computing capability, such as a complex programmable logic device CPLD, a field programmable gate array FPGA, a digital signal processor DSP, a microcontroller MCU, a single chip microcomputer, or the like.
The functions corresponding to the soft switching control method of the above embodiment are stored in the form of instructions in the memory of the electronic device, and when the functions corresponding to the soft switching control method of the above embodiment are to be executed, the processor of the electronic device accesses the memory to call and execute the corresponding instructions, so as to implement the functions corresponding to the soft switching control method of the above embodiment.
The memory, which is a non-volatile computer-readable storage medium, may be used to store a non-volatile software program and a non-volatile computer-executable program, such as the steps corresponding to the soft switching control method in the foregoing embodiments. The processor executes the functions of the steps corresponding to the soft switch control method of the above-described embodiments by executing the nonvolatile software program, instructions, and modules stored in the memory.
The memory may include high speed random access memory and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some embodiments, the memory optionally includes memory located remotely from the processor, and such remote memory may be coupled to the processor via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The program instructions/modules described above are stored in memory and, when executed by one or more processors, perform the soft-switching control method of the above-described method embodiments, e.g., perform the various steps shown in fig. 2 described in the above-described method embodiments.
As another aspect of the embodiments of the present invention, as shown in fig. 1, the totem-pole bridgeless circuit includes the totem-pole bridgeless circuit, and further includes a first voltage polarity detection circuit 50, a second voltage polarity detection circuit 60, and a controller 70, the first voltage polarity detection circuit 50 is connected to the first current transformer CT1 for detecting the voltage polarity of the voltage across the secondary winding of the first current transformer, the second voltage polarity detection circuit 60 is connected to the second current transformer CT2 for detecting the voltage polarity of the voltage across the secondary winding of the second current transformer, and the controller 70 is connected to the first voltage polarity detection circuit 50, the second voltage polarity detection circuit 60, the third switch Q3, and the fourth switch Q4 for detecting the voltage polarity of the voltage across the secondary winding of the first current transformer 1 or the voltage across the secondary winding of the second current transformer CT2 according to the voltage polarity of the voltage across the secondary winding of the first current transformer CT1 or the voltage across the secondary winding of the second current transformer CT2 The voltage polarity controls the switching state of the third switching tube Q3 or the fourth switching tube Q4.
As shown in fig. 3, the controller 70 includes at least one processor 701 and a memory 702 communicatively coupled to the at least one processor 701, for example, one processor 701 in fig. 3.
The processor 701 and the memory 702 may be connected by a bus or other means, such as the bus connection shown in fig. 3.
The memory 702 stores instructions executable by the at least one processor 701 to cause the at least one processor 701 to perform the steps illustrated in fig. 2.
In some embodiments, the first switch Q1 and the second switch Q2 may be diodes, MOSFETs, IGBTs, bipolar transistors or the like, and the first switch Q1 and the second switch Q2 are diodes, for example.
In some embodiments, the third switch Q3 and the fourth switch Q4 may be metal-oxide semiconductor field effect transistors (MOSFETs) or Insulated Gate Bipolar Transistors (IGBTs), which may be GaN, SiC, or the like, and the N-channel MOSFETs are exemplified as the third switch Q3 and the fourth switch Q4.
In some embodiments, the first current transformer CT1 may be connected between the first parallel connection point 1A and the drain of the third switch tube Q3, or between the source of the third switch tube Q3 and the second series connection point 2B, and the second current transformer CT1 may be connected between the second series connection point 2B and the drain of the fourth switch tube Q4, or between the source of the fourth switch tube Q4 and the second parallel connection point 1B, which is not limited herein.
In some embodiments, as shown in fig. 1, the first current transformer CT1 includes a first primary winding and at least one first secondary winding, and the second current transformer CT2 includes a second primary winding and at least one second secondary winding, where the number of the first secondary winding and the second secondary winding may be one or more, and the specific number is not limited herein.
In some embodiments, the first voltage polarity detection circuit 50 includes a first transformer magnetic reset unit 501 and a first voltage polarity comparison unit 502, the first transformer magnetic reset unit 501 is connected to the first current transformer CT1 and is configured to perform magnetic reset on the first current transformer CT1 when the current flowing through the third switching tube Q3 is in a zero-crossing state, and the first voltage polarity comparison unit 502 is respectively connected to the first current transformer CT1 and the first transformer magnetic reset unit 501 and is configured to detect the voltage polarity of the first secondary winding after the first current transformer CT1 is magnetically reset.
In some embodiments, the second voltage polarity detection circuit 60 includes a second transformer magnetic reset unit 601 and a second voltage polarity comparison unit 602, the second transformer magnetic reset unit 601 is connected to the second current transformer CT2 for performing magnetic reset on the second current transformer CT2 when the fourth switch Q4 is turned off, and the second voltage polarity comparison unit 602 is respectively connected to the second current transformer CT2 and the second transformer magnetic reset unit 601 for detecting the voltage polarity of the second secondary winding after the second current transformer CT2 is magnetically reset.
In some embodiments, the controller 70 is a complex programmable logic device CPLD or a field programmable gate array FPGA or a digital signal processor DSP or a microcontroller MCU.
In some embodiments, the third switch Q3 and the fourth switch Q4 are N-channel MOSFETs or IGBTs.
In order to explain the working principle of the totem-pole bridgeless circuit provided by the embodiment of the present invention in detail, the embodiment of the present invention is explained in detail with reference to fig. 4 to 9, and it should be noted that the timing diagrams shown in fig. 6 and 9 are only used for explaining the embodiment of the present invention, and do not limit the scope of the embodiment of the present invention in any way. The working principle is as follows:
the parameters in the timing diagrams shown in fig. 4 and 9 are:
i _ L1: the current through inductor L1;
i _ Q3: current flowing through the third switching tube Q3;
i _ Q4: the current flowing through the fourth switching tube Q4;
u _ AB: the potential difference across the secondary winding A, B of the first current transformer CT 1;
u _ BA: the potential difference across the secondary winding B, A of the first current transformer CT 1;
u _ CD: the potential difference across the secondary winding C, D of the second current transformer CT 2;
u _ DC: the potential difference across the secondary winding D, C of the second current transformer CT 2;
o _ 502: an output level signal of the first voltage polarity comparison unit;
o _ 602: an output level signal of the second voltage polarity comparison unit;
d _ Q3: a gate driving signal of the third switching tube Q3;
d _ Q4: and a gate driving signal of the fourth switching tube Q4.
When the L terminal of the power supply AC is positive with respect to the N terminal, the fourth switching tube Q4 is turned on, and the third switching tube Q3 is turned off, as shown in fig. 4, the power supply AC, the inductor L1, the channel of the fourth switching tube Q4, the second current transformer CT2, the second switching tube Q2, and the power supply AC form a current loop, and the polarity of the potential difference U _ DC across the secondary winding D, C of the second current transformer CT2 is negative.
At time t1, the fourth switching tube Q4 starts to turn off, the current direction is as shown in fig. 5, the power supply AC, the inductor L1, the body diode of the third switching tube Q3, the first current transformer CT1, the capacitor 30, the load 40, the second switching tube Q2 and the power supply AC form a current loop, at this time, the second current transformer CT2 enters a magnetic reset state, the polarity of U _ DC is positive, when the second voltage polarity comparison unit 602 detects that the polarity of U _ DC is changed, the controller 70 controls the third switching tube Q3 to be turned on after delaying a period of time according to the polarity change, or controls the third switching tube Q3 to be turned on after delaying a period of time when the fourth switching tube Q4 is turned off, that is, at time t2, so that the current flowing through the body diode of the third switching tube Q3 is changed to flow through the channel of the third switching tube Q3, thereby effectively reducing the conduction loss of the third switching tube Q3.
Before the current flowing through the third switch tube Q3 crosses zero, the polarity of U _ AB is negative, when the current flowing through the third switch tube Q3 crosses zero, that is, at time t3, the first current transformer CT1 enters a magnetic reset state, at which the polarity of U _ AB is positive, when the first voltage polarity comparison unit 502 detects that the polarity of U _ AB is changed, the controller 70 continues to turn on the third switch tube Q3 for a time period from t3 to t4 according to the polarity change, turns off the third switch tube Q3 at time t4, reverses the current flowing through the third switch tube Q3 during time t3 to t4, and the current still flows through the channel of the third switch tube Q3, which is used to discharge the junction capacitance of the fourth switch tube Q4 to be turned on while charging the junction capacitance of the third switch tube Q3.
After the third switching tube Q3 is turned off at time t4, the controller 70 delays a period of time, that is, the fourth switching tube Q4 is turned on at time t5, and within a time period from t4 to t5, the junction capacitor of the fourth switching tube Q4 to be turned on is discharged while the junction capacitor of the third switching tube Q3 is charged, and after the period of time, the fourth switching tube Q4 is turned on, so that ZVS or VS of the fourth switching tube Q4 is realized, and the turn-on loss of the fourth switching tube Q4 is reduced.
Compared to the inductor Current Continuous Mode (CCM), in this embodiment, by detecting the voltage polarity change of the voltage across the secondary winding of the second current transformer CT2, delaying the first preset time period, and after the first preset time period, turning on the third switch tube Q3 to change the current from flowing through the body diode of the third switch tube Q3 to flowing through the channel of the third switch tube Q3, by detecting the voltage polarity change of the voltage across the secondary winding of the first current transformer CT1, delaying the second preset time period according to the polarity change, and continuing turning on the third switch tube Q3 for the second preset time period to reverse the current flowing through the third switch tube Q3, after the second preset time period, turning off the third switch tube Q3, when the third switch tube Q3 is turned off, delaying the third preset time period, and after the third preset time period, turning on the fourth switch tube Q4, in a third preset time period, the junction capacitor of the third switching tube Q3 is charged and the junction capacitor of the fourth switching tube Q4 to be conducted is discharged, so that the inductor current works in a CRM mode, ZVS or VS in a full alternating current input voltage and full load range can be realized, the turn-on loss of the switching tubes is effectively reduced, and meanwhile, since the reverse current flowing through the third switching tube Q3 does not flow through the body diode of the third switching tube Q3 but flows through the channel of the third switching tube Q3, the conduction loss of the switching tubes is reduced, and the loss problem caused by the reverse recovery of the body diode parasitic in the switching tubes is solved, so that the embodiment can meet the requirements of high power density or high efficiency.
When the L terminal of the power supply AC is negative with respect to the N terminal, the third switching tube Q3 is turned on, and the fourth switching tube Q4 is turned off, as shown in fig. 7, the power supply AC, the first switching tube Q1, the first current transformer CT1, the channel of the third switching tube Q3, the inductor L1, and the power supply AC form a current loop, and the polarity of the potential difference U _ BA across the secondary winding B, A of the first current transformer CT1 is negative.
At time t6, the third switch tube Q3 starts to turn off, the current direction is as shown in fig. 8, the power supply AC, the first switch tube Q1, the capacitor 30, the second current transformer CT2, the body diode of the fourth switch tube Q4, the inductor L1 and the power supply AC form a current loop, at this time, the first current transformer CT1 enters a magnetic reset state, the polarity of U _ BA is positive, when the first voltage polarity comparison unit 502 detects that the polarity of U _ BA is changed, the controller 70 controls the fourth switch tube Q4 to be turned on after delaying for a certain time according to the polarity change, or controls the fourth switch tube Q4 to be turned on after delaying for a certain time when the third switch tube Q3 is turned off, that is, at time t7, so that the current flowing through the body diode of the fourth switch tube Q4 is changed to flow through the channel of the fourth switch tube Q4, thereby effectively reducing the conduction loss of the fourth switch tube Q4.
Before the current flowing through the fourth switching tube Q4 crosses zero, the polarity of U _ CD is negative, when the current flowing through the fourth switching tube Q4 crosses zero, that is, at time t8, the second current transformer CT2 enters a magnetic reset state, at which the polarity of U _ CD is positive, when the second voltage polarity comparison unit 602 detects that the polarity of U _ CD is changed, the controller 70 delays the switching on of the fourth switching tube Q4 for a period of time from t8 to t9, turns off the fourth switching tube Q4 at time t9, reverses the current flowing through the fourth switching tube Q4 for a period from t8 to t9, and the current still flows through the channel of the fourth switching tube Q4, which is used to discharge the junction capacitor of the forthcoming third switching tube Q3 while charging the junction capacitor of the fourth switching tube Q4.
After the fourth switching tube Q4 is turned off at time t9, the controller 60 delays for a period of time, that is, the third switching tube Q3 is turned on at time t10, and within a time period from t9 to t10, the junction capacitor of the fourth switching tube Q4 is charged while the junction capacitor of the third switching tube Q3 to be turned on is discharged, and after the period of time, the third switching tube Q3 is turned on, so that ZVS or VS of the third switching tube Q3 is realized, and the turn-on loss of the third switching tube Q3 is reduced.
In the present embodiment, by detecting a change in the voltage polarity of the voltage across the secondary winding of first current transformer CT1, delaying a fourth predetermined time period, and turning on fourth switching tube Q4 after the fourth predetermined time period, so that the current is switched from flowing through the body diode of fourth switching tube Q4 to flowing through the channel of fourth switching tube Q4, by detecting a change in the voltage polarity of the voltage across the secondary winding of second current transformer CT2, delaying a fifth predetermined time period according to the polarity change, and continuing to turn on fourth switching tube Q4 for the fifth predetermined time period, so that the current flowing through fourth switching tube Q4 is reversed, after the fifth predetermined time period, fourth switching tube Q4 is turned off, while turning off the fourth switching tube, delaying a sixth predetermined time period, and turning on third switching tube Q3 after the sixth predetermined time period, while discharging the third junction Q3 to be turned on by charging the capacitance junction of fourth switching tube Q4, the inductor current works in a CRM mode, full alternating current input voltage and ZVS or VS within a full load range can be achieved, the switching loss of the switching tube is effectively reduced, meanwhile, since reverse current flowing through the fourth switching tube Q4 does not flow through a body diode of the fourth switching tube Q4 but flows through a channel of the fourth switching tube Q4, the conduction loss of the switching tube is reduced, and the problem of loss caused by reverse recovery of a parasitic body diode in the switching tube is solved, so that the embodiment can meet the requirements of high power density or high efficiency.
As yet another aspect of the embodiments of the present invention, there is provided a totem-pole bridgeless system, including the totem-pole bridgeless circuit as described above.
Finally, it is to be understood that the present invention may be embodied in many different forms and is not limited to the embodiments described in the present specification, which are provided as additional limitations to the present disclosure, and which are provided for the purpose of providing a more thorough understanding of the present disclosure. In the light of the above, the above features are combined with each other and many other variations of the different aspects of the invention described above are considered to be within the scope of the present description; further, modifications and variations will occur to those skilled in the art in light of the foregoing description, and it is intended to cover all such modifications and variations as fall within the true spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. A soft switch control method is applied to a totem-pole bridgeless circuit and is characterized in that the totem-pole bridgeless circuit comprises a first bridge arm and a second bridge arm which are connected in parallel between a first parallel connection point and a second parallel connection point, the first bridge arm comprises a first switch tube and a second switch tube which are connected in series in the same direction, the second bridge arm comprises a third switch tube and a fourth switch tube which are connected in series in the same direction, the connection point between the first switch tube and the second switch tube is a first series connection point, the connection point between the third switch tube and the fourth switch tube is a second series connection point, a power supply and an inductor are connected in series between the first series connection point and the second series connection point, a capacitor and a load are further connected in parallel between the first parallel connection point and the second parallel connection point, a first current transformer is connected in series between the first parallel connection point and the second series connection point, a second current transformer is connected in series between the second parallel connection point and the second series connection point,
the method comprises the following steps:
after the fourth switching tube is turned off, when voltage polarity change of voltages at two ends of a secondary winding of the second current transformer is detected, delaying a first preset time, and after the first preset time, turning on the third switching tube to convert a first current from a body diode flowing through the third switching tube into a channel flowing through the third switching tube;
when voltage polarity change of voltages at two ends of a secondary winding of the first current transformer is detected, delaying a second preset time, and continuing to conduct the third switching tube within the second preset time so as to enable a second current to flow through the third switching tube, wherein the second current is opposite to the first current in flow direction, and the second current is used for charging a junction capacitor of the third switching tube and discharging the junction capacitor of the fourth switching tube to be conducted;
and after the second preset time period, the third switching tube is turned off, the third preset time period is delayed when the third switching tube is turned off, and the fourth switching tube is turned on after the third preset time period.
2. A totem pole bridgeless circuit comprises a first bridge arm and a second bridge arm which are connected in parallel between a first parallel connection point and a second parallel connection point, wherein the first bridge arm comprises a first switch tube and a second switch tube which are connected in series in the same direction, the second bridge arm comprises a third switch tube and a fourth switch tube which are connected in series in the same direction, the connection point between the first switch tube and the second switch tube is a first series connection point, the connection point between the third switch tube and the fourth switch tube is a second series connection point, a power supply and an inductor are connected in series between the first series connection point and the second series connection point, a capacitor and a load are further connected in parallel between the first parallel connection point and the second parallel connection point, a first current transformer is connected in series between the first parallel connection point and the second series connection point, and a second current transformer is connected in series between the second parallel connection point and the second series connection point, characterized in that, totem-pole bridgeless circuit still includes:
the first voltage polarity detection circuit is connected with the first current transformer and is used for detecting the voltage polarity of the voltage at two ends of the secondary winding of the first current transformer;
the second voltage polarity detection circuit is connected with the second current transformer and is used for detecting the voltage polarity of the voltage at the two ends of the secondary winding of the second current transformer;
the controller is respectively connected with the first voltage polarity detection circuit, the second voltage polarity detection circuit, the third switch tube and the fourth switch tube and is used for controlling the switching state of the third switch tube or the fourth switch tube according to the voltage polarity of the voltage at two ends of the secondary winding of the first current transformer or the voltage polarity of the voltage at two ends of the secondary winding of the second current transformer;
wherein the controller includes:
at least one processor; and
a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of claim 1.
3. The totem-pole bridgeless circuit of claim 2, wherein the first current transformer comprises a first primary winding and at least one first secondary winding, and the second current transformer comprises a second primary winding and at least one second secondary winding.
4. The totem-pole bridgeless circuit of claim 3, wherein the first voltage polarity detection circuit comprises:
the first transformer magnetic resetting unit is connected with the first current transformer and is used for carrying out magnetic resetting on the first current transformer when the current flowing through the third switching tube is in a zero crossing point state;
and the first voltage polarity comparison unit is respectively connected with the first current transformer and the first transformer magnetic reset unit and is used for detecting the voltage polarity wound by the first secondary side after the first current transformer is magnetically reset.
5. The totem-pole bridgeless circuit of claim 3, wherein the second voltage polarity detection circuit comprises:
the second transformer magnetic resetting unit is connected with the second current transformer and is used for performing magnetic resetting on the second current transformer when the fourth switching tube is turned off;
and the second voltage polarity comparison unit is respectively connected with the second current transformer and the second transformer magnetic reset unit and is used for detecting the voltage polarity of the second secondary winding after the second current transformer is magnetically reset.
6. The totem-pole bridgeless circuit of any one of claims 2 to 5, wherein the controller is a Complex Programmable Logic Device (CPLD) or a Field Programmable Gate Array (FPGA) or a Digital Signal Processor (DSP) or a Microcontroller (MCU).
7. The totem-pole bridgeless circuit of any one of claims 2 to 5, wherein the third switching tube and the fourth switching tube are N-channel metal-oxide semiconductor field effect transistors (MOSFETs) or Insulated Gate Bipolar Transistors (IGBTs).
8. A totem-pole bridgeless system comprising a totem-pole bridgeless circuit according to any of claims 2 to 7.
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