CN118900035B - DC chopper circuit soft switch control method and DC chopper circuit - Google Patents
DC chopper circuit soft switch control method and DC chopper circuit 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
- H02M3/00—Conversion of DC power input into DC power output
- H02M3/02—Conversion of DC power input into DC power output without intermediate conversion into AC
- H02M3/04—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters
- H02M3/10—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
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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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- 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
- H02M3/02—Conversion of DC power input into DC power output without intermediate conversion into AC
- H02M3/04—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters
- H02M3/10—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/1557—Single ended primary inductor converters [SEPIC]
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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 application relates to a direct-current chopper circuit soft switch control method and a direct-current chopper circuit. The method comprises the steps of obtaining target frequency of a direct current chopper circuit when a valley is opened, wherein the target frequency is calculated based on a target frequency expression and a condition of opening a first valley, the target frequency expression is obtained by analyzing target waveforms of all target devices in the direct current chopper circuit when the switching frequency of a switching tube of the direct current chopper circuit is changed to enable the direct current chopper circuit to be in a critical continuous state, and driving the switching tube of the direct current chopper circuit to work based on the target frequency. The method can improve the circuit efficiency.
Description
Technical Field
The application relates to the technical field of circuits, in particular to a direct-current chopper circuit soft switch control method and a direct-current chopper circuit.
Background
The direct current chopper circuit (SINGLE ENDED PRIMARY Inductor Converter) has the advantages of voltage rising and falling, homopolarity of input and output, and the like. The coupling inductance in the DC chopper circuit is replaced by a transformer to realize the input and output electrical isolation, however, in order to improve the working efficiency of the sepic DC chopper circuit, for example, in order to realize the soft start of a switching tube in the sepic DC chopper circuit, the auxiliary components are added, thus not only improving the design cost of the circuit, but also lowering the overall efficiency of the circuit compared with Buck or Boost circuits.
Disclosure of Invention
In view of the above, it is desirable to provide a dc chopper circuit soft switching control method and a dc chopper circuit capable of improving circuit efficiency.
The application provides a direct current chopper circuit soft switch control method, which comprises the following steps:
Acquiring a target frequency of a direct current chopper circuit when a valley is opened, wherein the target frequency is calculated based on a target frequency expression and a condition of opening a first valley, and the target frequency expression is obtained by analyzing a target waveform of each target device in the direct current chopper circuit when the switching frequency of a switching tube of the direct current chopper circuit is changed so that the direct current chopper circuit is in a critical continuous state;
and driving the operation of the switching tube of the direct current chopper circuit based on the target frequency.
In one embodiment, the operation of the switching tube driving the dc chopper circuit based on the target frequency includes:
Driving the switching tube of the direct current chopper circuit to operate based on the current frequency under the condition that the target frequency is equal to the current frequency of the direct current chopper circuit;
determining the sequence number of the open valley bottom of the switching tube under the condition that the target frequency is larger than a set value;
Obtaining a correction frequency based on the sequence number of the open valley bottom of the switching tube and the target frequency expression;
And driving the switching tube of the direct current chopper circuit to work based on the correction frequency.
In one embodiment, the target frequency expression is:
fs=Vin×D×(1-D)/(2L×Iout+Vin×D×K×0.5Tcr)
Wherein fs is the target frequency, vin is the input voltage of the dc chopper circuit, D is the duty ratio of the switching tube of the dc chopper circuit, L is the parallel inductance of the first inductor and the second inductor in the dc chopper circuit, iout is the dc current output by the dc chopper circuit, tcr is the resonance period of the dc chopper circuit, k=2n-1, where n is the resonance valley bottom, and n is a positive integer.
In one embodiment, the method further comprises:
obtaining target waveforms of all target devices in the direct current chopper circuit when the direct current chopper circuit is in a critical continuous state, wherein the direct current chopper circuit is in the critical continuous state by changing the switching frequency of a switching tube;
analyzing the target waveforms of the target devices to determine that the maximum value of the current of the switching tube is equal to the maximum value of the current of the diode;
obtaining a first relation between the maximum value of the current of the diode and the output current of the direct current chopper circuit, the duty cycle of the direct current chopper circuit, the resonance period and the switching frequency based on the current of the diode;
Acquiring a node current change relation, wherein the node current change relation is a relation among the current change quantity of a first inductor of the direct current chopper circuit, the current change quantity of a second inductor of the direct current chopper circuit and the current change quantity of the switching tube;
Determining a current change relation of a first inductor, wherein the current change relation of the first inductor is a relation between a current change amount of the first inductor and an input voltage, a duty ratio of the switching tube, a switching frequency of the switching tube and an inductance value of the first inductor;
determining a current change relation of a second inductor, wherein the current change relation of the second inductor is a relation between a current change amount of the second inductor and an input voltage, a duty ratio of the switching tube, a switching frequency of the switching tube and an inductance value of the second inductor;
And obtaining the target frequency expression based on the first relation, the node current change relation, the current change relation of the first inductor and the current change relation of the second inductor.
In one embodiment, the obtaining, based on the current of the diode, a first relationship between a maximum value of the current of the diode and the output current of the dc chopper circuit, a duty cycle, a resonance period of the dc chopper circuit, and the switching frequency includes:
Obtaining a maximum value of the current of the diode, a duty cycle, a resonance period of the direct current chopper circuit and a second relation between the switching frequency and the output current of the direct current chopper circuit based on the current of the diode;
And sorting the second relation to obtain a first relation between the maximum value of the current of the diode and the output current of the direct current chopper circuit, the duty ratio of the direct current chopper circuit, the resonance period and the switching frequency.
In one embodiment, the acquiring the node current change relation includes:
Acquiring a node current relation when the switching tube is conducted, wherein the node current relation is the sum of the current of the first inductor and the current of the second inductor and is the current of the switching tube;
and obtaining a node current change relation based on the volt-second law and the node current relation.
In one embodiment, the determining the current variation relation of the first inductor includes:
obtaining an inductance value of the first inductor based on the switching frequency of the switching tube and the inductance value of the first inductor;
obtaining an effective voltage of the first inductor based on the input voltage and a duty cycle of the switching tube;
And obtaining a current change relation of the first inductor based on the inductance value of the first inductor and the effective voltage of the first inductor.
In one embodiment, the determining the current variation relationship of the second inductor includes:
obtaining an inductance value of the second inductor based on the switching frequency of the switching tube and the inductance value of the second inductor;
obtaining an effective voltage of the second inductor based on the input voltage and the duty cycle of the switching tube;
And obtaining the current change relation of the second inductor based on the inductance value of the second inductor and the effective voltage of the second inductor.
In one embodiment, the obtaining the target frequency expression based on the first relationship, the node current change relationship, the current change relationship of the first inductor, and the current change relationship of the second inductor includes:
obtaining a target relationship between the current change of the second inductor and the output current of the direct current chopper circuit, the duty ratio of the direct current chopper circuit, the resonance period, the switching frequency, the input voltage and the inductance value of the first inductor based on the first relationship, the node current change relationship and the current change relationship of the first inductor;
And obtaining the target frequency expression based on the target relation and the current change relation of the second inductor.
In one embodiment, the second inductor is a transformer, and the determining the current variation relationship of the second inductor includes:
obtaining an inductance value of the second inductor based on the switching frequency of the switching tube, the inductance value of the second inductor and the transformation ratio of the transformer;
obtaining an effective voltage of the second inductor based on the input voltage and the duty cycle of the switching tube;
And obtaining the current change relation of the second inductor based on the inductance value of the second inductor and the effective voltage of the second inductor.
In a second aspect, the present application further provides a dc chopper circuit driven by the method described above.
According to the direct-current chopper circuit soft switching control method and the direct-current chopper circuit, the switching frequency of the switching tube of the direct-current chopper circuit is changed firstly, so that the direct-current chopper circuit is in a critical continuous state, target waveforms of all target devices in the direct-current chopper circuit are obtained, the target waveforms are analyzed to obtain the target frequency of the direct-current chopper circuit when the valley bottom is opened, and then the switching tube of the direct-current chopper circuit is driven to work based on the target frequency, so that the opening of the direct-current chopper circuit at the valley bottom is realized, the opening of the direct-current chopper circuit at the valley bottom can be realized without additional power devices, the circuit loss is reduced, and the circuit efficiency is improved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the related art, the drawings that are needed in the description of the embodiments of the present application or the related technologies will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other related drawings may be obtained according to these drawings without inventive effort to those of ordinary skill in the art.
FIG. 1 is a circuit diagram of a DC chopper circuit in one embodiment;
FIG. 2 is a circuit diagram of a DC chopper circuit in another embodiment;
FIG. 3 is a flow chart of a method for controlling soft switching of a DC chopper circuit according to an embodiment;
FIG. 4 is a flow chart of the analysis steps of the target frequency expression in one embodiment;
FIG. 5 is a waveform diagram of current waveforms for respective target devices in one embodiment;
fig. 6 is a waveform diagram of the switching tube Q1 in one embodiment.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
The direct-current chopper circuit soft switch control method provided by the embodiment of the application can be applied to the direct-current chopper circuit shown in fig. 1. Optionally, the dc chopper circuit is a sepic circuit. The direct current chopper circuit comprises a first inductor Lr, a switching tube Q1, a second inductor Lm, a diode D1, a load RL, a blocking capacitor Cs and an output capacitor Co.
The first end of the first inductor Lr is connected with the first end of the voltage source Vin, the second end of the first inductor Lr is connected with the first end of the blocking capacitor Cs and the first end of the switching tube Q1, the control end of the switching tube Q1 is connected with the circuit controller, the second end of the switching tube Q1 is connected with the second end of the voltage source Vin, the second end of the blocking capacitor Cs is connected with the first end of the second inductor Lm and the positive input end of the diode D1, the negative input end of the diode D1 is connected with the first end of the output capacitor Co and the first end of the load RL, and the second end of the output capacitor Co and the second end of the load RL are connected with the second end of the voltage source Vin. The first parasitic capacitance Coss is the parasitic capacitance of the switching tube Q1, and the second parasitic capacitance Cd is the parasitic capacitance of the diode D1, and the parasitic meaning is that the capacitance is not designed in that place, but because the wires always have mutual capacitance, the mutual capacitance is as if the mutual capacitance is parasitic between the wires, the parasitic capacitance is called as stray capacitance.
In this embodiment, the capacity of the blocking capacitor Cs and the capacity of the output capacitor Co are large enough, and they can be approximated to the voltage source Vin.
When the switching tube Q1 is conducted, the input voltage source Vin charges the first inductor Lr, and a loop is formed by the positive electrode of the voltage source Vin, the first inductor Lr and the negative electrode of the voltage source Vin. The blocking capacitor Cs is full when the switching tube Q1 is turned off in the previous period, and when the switching tube Q1 is turned on in the present period, the energy is released to charge the second inductor Lm, at this time, the diode D1 is turned off, and the output voltage is maintained by the output capacitor Co.
When the switching tube Q1 is turned off, the output voltage is supplied by the input voltage source Vin and the first inductor Lr together, a loop is formed by the voltage source Vin, the first inductor Lr, the blocking capacitor Cs, the diode D1 and the load RL, the second inductor Lm also forms induced electromotive force, the freewheels through the diode D1, and a loop is formed by the second inductor Lm, the diode D1 and the load RL.
In other embodiments, as shown in fig. 2, fig. 2 is a circuit diagram of a dc chopper circuit in another embodiment, where the second inductor Lm in the dc chopper circuit is replaced with a transformer to achieve isolation between input and output.
In order to improve the circuit efficiency of the dc chopper circuit and realize zero voltage turn-on (ZVS) or valley turn-on of the switching transistor Q1 in the circuit without adding any additional power device, the application provides a method for controlling soft switch of the dc chopper circuit, as shown in fig. 3, comprising the following steps 302 to 304. Wherein:
S302, obtaining a target frequency of the direct current chopper circuit when the valley bottom is open, wherein the target frequency is calculated based on a target frequency expression and a condition that the first valley bottom is open, and the target frequency expression is obtained by analyzing current waveforms of all target devices in the direct current chopper circuit when the switching frequency of a switching tube Q1 of the direct current chopper circuit is changed so that the direct current chopper circuit is in a critical continuous state.
The target frequency is the frequency of the direct current chopper circuit when the first valley is on, and the target frequency can be calculated based on a target frequency expression and a condition of the first valley is on, wherein the condition of the first fixed on is that the frequency of the switching tube Q1 is equal to the target frequency. The target frequency expression is obtained based on circuit analysis, specifically, under the condition that the duty ratio of the switching tube Q1 is certain, the switching frequency of the switching tube Q1 of the direct current chopper circuit is changed to enable the direct current chopper circuit to be in a critical continuous state, current waveforms of all target devices in the direct current chopper circuit are obtained, the current waveforms of all target devices are analyzed to obtain the target frequency expression, and a specific analysis process can be seen below.
S304, driving a switching tube Q1 of the direct current chopper circuit to work based on the target frequency.
In order to realize zero-voltage turn-on or fixed turn-on of the switching tube Q1 of the dc chopper circuit, when the actual operating frequency of the dc chopper circuit is equal to the target frequency, it may be determined through circuit analysis that the dc chopper circuit enters a critical continuous mode, so that the switching tube Q1 may be turned on at the first valley.
Alternatively, driving the switching tube Q1 of the DC chopper circuit based on the target frequency includes driving the switching tube of the DC chopper circuit to operate based on the current frequency if the current frequency of the DC chopper circuit is equal to the target frequency.
Optionally, the switching tube Q1 of the direct current chopper circuit is driven based on the target frequency, and comprises the steps of determining the sequence number of the open valley bottom of the switching tube Q1 under the condition that the current frequency of the direct current chopper circuit is larger than a set value, obtaining the correction frequency based on the sequence number of the open valley bottom of the switching tube Q1 and the target frequency expression, and driving the switching tube Q1 of the direct current chopper circuit to work based on the correction frequency.
Specifically, when the output voltage is greater than the input voltage, the current frequency of the switching tube Q1 is the target frequency, and the DS voltage can be completely reduced to 0 at the first valley time when the switching tube Q1 is turned off, so that zero voltage turn-on (ZVS) of the switching tube Q1 can be realized, the turn-on loss of the switching tube Q1 is reduced to the minimum under zero voltage turn-on, and the circuit efficiency can be remarkably improved.
When the calculated target frequency exceeds a set value, the n-th valley is turned on in order to reduce the switching frequency of the direct current chopper circuit and reduce electromagnetic interference or switching loss, namely, the sequence number of the on valley of the switching tube Q1 is determined first, and the correction frequency is obtained based on the sequence number of the on valley of the switching tube Q1 and a target frequency expression, wherein the target frequency expression is as follows:
fs=Vin×D×(1-D)/(2L×Iout +Vin×D×K×0.5Tcr)
Wherein k=2n—1, n is taken to be 1, 2..n represents the first and second..n.n represents the first and second..n resonant valley, fs is the calculated target frequency, vin is the input voltage of the dc chopper circuit, D is the duty cycle of the dc chopper circuit, L is the parallel inductance of the first inductance Lr and the second inductance Lm of the dc chopper circuit, iout is the output dc current of the dc chopper circuit, and Tcr is the resonant period of the dc chopper circuit.
In other alternative embodiments, for the dc chopper circuit shown in fig. 2, since the second inductance Lm is replaced with a transformer, the target frequency expression is:
fs= Vin×Ntr×D×(1-D)/(2L×Iout +Vin×D×K×0.5Tcr)
Where Ntr is the transformation ratio of the transformer.
Thus, the correction frequency is obtained based on the sequence number of the open valley bottom of the switching tube Q1 and the target frequency expression, and the switching tube Q1 of the direct current chopper circuit is driven based on the correction frequency so as to realize the opening of any valley bottom.
According to the direct-current chopper circuit soft switch control method, the switching frequency of the direct-current chopper circuit switching tube Q1 is changed firstly, so that the direct-current chopper circuit is in a critical continuous state, current waveforms of all target devices in the direct-current chopper circuit are obtained, the current waveforms are analyzed to obtain the target frequency of the direct-current chopper circuit when the valley bottom is opened, and then the switching tube Q1 of the direct-current chopper circuit is driven to work based on the target frequency, so that the direct-current chopper circuit is opened at the valley bottom, the direct-current chopper circuit can be opened at the valley bottom without additional power devices, the circuit loss is reduced, and the circuit efficiency is improved.
In one alternative embodiment, as shown in connection with fig. 4, fig. 4 is a flow chart of the steps of analyzing a target frequency expression in one embodiment, the steps of analyzing the target frequency expression may include:
S402, when the direct current chopper circuit is in a critical continuous state, the target waveforms of all target devices in the direct current chopper circuit are obtained, wherein the direct current chopper circuit is in the critical continuous state and is realized by changing the switching frequency of the switching tube Q1.
In this embodiment, by changing the switching frequency of the switching tube Q1, the current or voltage of each target device in the dc chopper circuit may be changed, and the current or voltage of each target device may be collected by an oscilloscope or other devices to obtain a current waveform or voltage waveform, where when the current of the diode D1 is determined to be in a critical continuous state based on the current waveform of the diode D1, that is, when the dc chopper circuit is in a critical continuous state, the frequency of the switching tube Q1 is not changed any more, and the current waveform of each target device in the dc chopper circuit is obtained. As shown in fig. 5, fig. 5 is a waveform diagram of current waveforms of the respective target devices. Including the current of diode D1, the current of switching tube Q1, the sum of the currents of first inductance Lr and second inductance Lm, the voltage of switching tube Q1, and the control signal of switching tube Q1.
S404, analyzing the current waveform of each target device to determine that the maximum value of the current of the switching tube Q1 is equal to the maximum value of the current of the diode D1.
Referring to fig. 5, when the current of the diode D1 is in the critical continuous state, the current of the switching transistor Q1 is in the critical continuous state, and the minimum value I (Q1) _min_0 of the current of the switching transistor Q1, the maximum value I (Q1) _max of the current of the switching transistor Q1 is equal to the maximum value I (D1) _max of the current of the diode D1. And when VQ1 is 0, the switching tube Q1 is turned on to realize the turn-on of the valley bottom.
S406, obtaining a first relation between the maximum value of the current of the diode D1 and the output current of the direct current chopper circuit, the duty ratio of the direct current chopper circuit, the resonance period and the switching frequency based on the current of the diode D1.
Wherein the first relationship is obtained by analyzing the current waveform of the diode D1.
In one alternative embodiment, a first relation between the maximum value of the current of the diode D1 and the output current of the direct current chopper circuit, the duty cycle of the direct current chopper circuit, the resonance period and the switching frequency is obtained based on the current of the diode D1, a second relation between the maximum value of the current of the diode, the duty cycle of the direct current chopper circuit, the resonance period and the switching frequency and the output current of the direct current chopper circuit is obtained based on the current of the diode, and the second relation is arranged to obtain a first relation between the maximum value of the current of the diode and the output current of the direct current chopper circuit, the duty cycle of the direct current chopper circuit, the resonance period and the switching frequency.
When the switching tube Q1 is turned off, the output voltage is provided by the input voltage source Vin and the first inductor Lr together, and the currents generated by the two loops are rectified by the diode D1 to obtain the output current, and since the output current is direct current, the output current is equal to the integral of the current of the diode D1, that is, the area of the target triangle ABC in fig. 5, and the target triangle ABC is analyzed, it can be determined that the maximum value I (D1) _max of the current of the diode D1 of the target triangle ABC is high, the bottom is bc=de-DB-CE, where DE is one switching period of the switching tube Q1, DB is on time, DE-DB is off time, and thus DE-DB can be 1-D, where D is the duty cycle of the direct current chopper circuit, and CE is the resonance time, and in order to realize that the bottom of the triangle is 1-D-0.5tcr×fs, where 0.5tcr×is the position of the first resonance wave bottom of the oscillating voltage, and can be combined with fig. 5.
The area based on the triangle is the output current Iout of the direct current chopper circuit, and can be obtained through a triangle calculation formula, namely the area of the target triangle ABC=1/2×I (D1) _max (1-D-0.5 Tcr×fs), so that a second relation can be obtained, namely Iout=1/2×I (D1) _max (1-D-0.5 Tcr×fs), and a first relation can be obtained through arrangement:
I(Q1)_max=I(D1)_max=2Iout/(1-D-0.5Tcr×fs)
And S408, acquiring a node current change relation, wherein the node current change relation is a relation among the current change amount of the first inductor Lr of the direct current chopper circuit, the current change amount of the second inductor Lm of the direct current chopper circuit and the current change amount of the switching tube Q1.
In one optional embodiment, acquiring the node current change relation comprises acquiring the node current relation when the switching tube Q1 is conducted, wherein the node current relation is that the sum of the current of the first inductor Lr and the current of the second inductor Lm is the current of the switching tube Q1, and acquiring the node current change relation based on the volt-second law and the node current relation.
When the switching tube Q1 is turned on, it is known that I (Lr) +I (Lm) =I (Q1) is the current of the first inductor Lr, I (Lm) is the current of the second inductor Lm, and I (Q1) is the current of the switching tube Q1 according to the node current.
Due to the volt-second principle, that is, under the steady working state of the switching power supply, the voltage applied to the two ends of the inductor is multiplied by the on time, which is equal to the voltage of the two ends of the inductor at the off time multiplied by the off time, or the positive volt-second value of the two ends of the inductor is equal to the negative volt-second value in the steady working switching power supply.
Thus, a node current change relationship, that is, Δi (Lr) +Δi (Lm) = Δi (Q1) can be obtained, wherein the duration in which the current change becomes high for the driving signal of the switching tube Q1 corresponds to the current change, Δi (Lr) is the current change amount of the first inductance Lr of the dc chopper circuit, Δi (Lm) is the current change amount of the second inductance Lm of the dc chopper circuit, and Δi (Q1) is the current change amount of the switching tube Q1.
S410, determining a current change relation of the first inductor Lr, wherein the current change relation of the first inductor Lr is a relation between the current change quantity of the first inductor Lr and the input voltage, the duty ratio of the switching tube Q1, the switching frequency of the switching tube Q1 and the inductance value of the first inductor Lr.
In one alternative embodiment, determining the current variation relation of the first inductor Lr includes obtaining an inductance value of the first inductor Lr based on the switching frequency of the switching tube Q1 and the inductance value of the first inductor Lr, obtaining an effective voltage of the first inductor Lr based on the input voltage and the duty cycle of the switching tube Q1, and obtaining the current variation relation of the first inductor Lr based on the inductance value of the first inductor Lr and the effective voltage of the first inductor Lr.
Here, since the inductance value of the first inductor Lr is the product of the switching frequency of the switching transistor Q1 and the inductance value of the first inductor Lr, and the effective voltage of the first inductor Lr is the product of the input voltage and the duty cycle of the switching transistor Q1, the current change relationship Δi (Lm) =vin×d/(lm×fs) of the first inductor Lr can be obtained.
In one optional embodiment, the target frequency expression is obtained based on the first relation, the node current change relation, the current change relation of the first inductor Lr and the current change relation of the second inductor Lm, and the target frequency expression is obtained based on the first relation, the node current change relation and the current change relation of the first inductor Lr, and the target relation of the current change of the second inductor Lm and the output current of the direct current chopper circuit, the duty cycle of the direct current chopper circuit, the resonance period, the switching frequency, the input voltage and the inductance value of the first inductor Lr is obtained.
Specifically, the first relationship, the node current change relationship, and the current change relationship of the first inductor Lr are sorted to obtain an expression of the current change of the second inductor Lm, that is:
△I(Lr)= △I(Q1)-△I(Lm)=I(Q1)_max-I(Q1)_min-△I(Lm)
The steps are finished to delta I (Lr) =2Iout/(1-D-0.5 Tcr×fs) -VinxD/(Lm×fs)
And S412, determining a current change relation of the second inductor Lm, wherein the current change relation of the second inductor Lm is a relation between the current change amount of the second inductor Lm and the input voltage, the duty ratio of the switching tube Q1, the switching frequency of the switching tube Q1 and the inductance value of the second inductor Lm.
In one alternative embodiment, determining the current change relation of the second inductor Lm includes obtaining an inductance value of the second inductor Lm based on the switching frequency of the switching tube Q1 and the inductance value of the second inductor Lm, obtaining an effective voltage of the second inductor Lm based on the input voltage and the duty cycle of the switching tube Q1, and obtaining the current change relation of the second inductor Lm based on the inductance value of the second inductor Lm and the effective voltage of the second inductor Lm.
Since the inductance value of the second inductor Lm is the product of the switching frequency of the switching transistor Q1 and the inductance value of the second inductor Lm, and the effective voltage of the second inductor Lm is the product of the input voltage and the duty cycle of the switching transistor Q1, the current change relationship Δi (Lr) =vin×d/(lr×fs) of the second inductor Lm can be obtained, and the current change relationship vin=lr×fs×Δi (Lr)/D of the second inductor Lm can be obtained.
And S414, obtaining a target frequency expression based on the first relation, the node current change relation, the current change relation of the first inductor Lr and the current change relation of the second inductor Lm.
Wherein the above-mentioned current variation relation of the second inductance Lm is substituted into Δi (Lr) =2iout/(1-D-0.5 tcr×fs) -vin×d/(lm×fs), and is arranged to obtain fs=vin×d× (1-D-0.5 tcr×fs)/(2 l×iout), that is, the target frequency expression fs=vin×d× (1-D)/(2 l×iout+vin×d×0.5 Tcr), where l=lr// Lm (that is, inductance of Lr in parallel with Lm).
Thus, when the actual working frequency of the circuit is equal to the calculated frequency fs, the I (Q1) enters a critical continuous mode, and the switching tube Q1 can realize the first valley opening.
When the frequency at which the first valley is employed exceeds a set value, the n-th valley may be turned on in order to reduce the switching frequency of the circuit by reducing electromagnetic interference or switching loss, and the target frequency expression may be modified to fs=vin×d× (1-D)/(2l×iout+vin×d×k×0.5 Tcr), where kk=2n-1, n is 1, 2.
In one alternative embodiment, the second inductor Lm is a transformer, and determining the current variation relationship of the second inductor Lm includes obtaining an inductance value of the second inductor Lm based on a switching frequency of the switching tube Q1, an inductance value of the second inductor Lm, and a transformation ratio of the transformer, obtaining an effective voltage of the second inductor Lm based on an input voltage and a duty ratio of the switching tube Q1, and obtaining the current variation relationship of the second inductor Lm based on the inductance value of the second inductor Lm and the effective voltage of the second inductor Lm.
Specifically, for the isolated sepic circuit, the second inductance Lm may be replaced by a transformer, the derivation process is the same as that of fig. 4, the transformer transformation ratio Ntr is required to be increased in the formula, and the target frequency expression is as follows:
fs= Vin×Ntr×D×(1-D)/(2L×Iout +Vin×D×K×0.5Tcr)
also, where l=lr// Lm, tcr is the resonant period, and the resonant capacitance is the equivalent of Cd converted to the primary side of the transformer in parallel with Coss.
The switching frequency of the switching tube Q1 is calculated and adjusted according to each target frequency expression, so that the valley turn-on or zero voltage turn-on of the power tube can be realized, and the circuit efficiency can be improved, and particularly, the waveform diagram of the switching tube Q1 shown in fig. 6 can be seen, wherein I (Q1) is the current of the switching tube Q1, V (Q1) is the voltage of the switching tube Q1, g1 is the control signal of the switching tube Q1, and the frequency is calculated based on the target frequency expression.
It should be understood that, although the steps in the flowcharts related to the above embodiments are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.
Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above. Any reference to memory, database, or other medium used in embodiments provided herein may include at least one of non-volatile memory and volatile memory. The nonvolatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical Memory, high density embedded nonvolatile Memory, resistive random access Memory (RESISTIVE RANDOM ACCESS MEMORY, reRAM), magneto-resistive Memory (Magnetoresistive Random Access Memory, MRAM), ferroelectric Memory (Ferroelectric Random Access Memory, FRAM), phase change Memory (PHASE CHANGE Memory, PCM), graphene Memory, and the like. Volatile memory can include random access memory (Random Access Memory, RAM) or external cache memory, and the like. By way of illustration, and not limitation, RAM can be in various forms such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM), etc. The databases referred to in the embodiments provided herein may include at least one of a relational database and a non-relational database. The non-relational database may include, but is not limited to, a blockchain-based distributed database, and the like. The processor referred to in the embodiments provided in the present application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computation, an artificial intelligence (ARTIFICIAL INTELLIGENCE, AI) processor, or the like, but is not limited thereto.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the present application.
The foregoing examples illustrate only a few embodiments of the application and are described in detail herein without thereby limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of the application should be assessed as that of the appended claims.
Claims (10)
1. A method for controlling a soft switch of a direct current chopper circuit, the method comprising:
Acquiring a target frequency of a direct current chopper circuit when a valley is opened, wherein the target frequency is calculated based on a target frequency expression and a condition of opening a first valley, and the target frequency expression is obtained by analyzing a target waveform of each target device in the direct current chopper circuit when the switching frequency of a switching tube of the direct current chopper circuit is changed so that the direct current chopper circuit is in a critical continuous state;
driving operation of the switching tube of the direct current chopper circuit based on the target frequency;
the target frequency expression is:
fs=Vin×D×(1-D)/(2L×Iout +Vin×D×K×0.5Tcr)
wherein fs is the target frequency, vin is the input voltage of the dc chopper circuit, D is the duty ratio of the switching tube of the dc chopper circuit, L is the parallel inductance of the first inductor and the second inductor in the dc chopper circuit, iout is the dc current output by the dc chopper circuit, tcr is the resonance period of the dc chopper circuit, k=2n-1, wherein n is the resonance valley bottom, and n is a positive integer;
The method further comprises the steps of:
Acquiring target waveforms of all target devices in the direct current chopper circuit when the direct current chopper circuit is in a critical continuous state, wherein the direct current chopper circuit is in the critical continuous state by changing the switching frequency of the switching tube;
analyzing the target waveforms of the target devices to determine that the maximum value of the current of the switching tube is equal to the maximum value of the current of the diode;
obtaining a first relation between the maximum value of the current of the diode and the output current of the direct current chopper circuit, the duty cycle of the direct current chopper circuit, the resonance period and the switching frequency based on the current of the diode;
Acquiring a node current change relation, wherein the node current change relation is a relation among the current change quantity of a first inductor of the direct current chopper circuit, the current change quantity of a second inductor of the direct current chopper circuit and the current change quantity of the switching tube;
Determining a current change relation of a first inductor, wherein the current change relation of the first inductor is a relation between a current change amount of the first inductor and an input voltage, a duty ratio of the switching tube, a switching frequency of the switching tube and an inductance value of the first inductor;
determining a current change relation of a second inductor, wherein the current change relation of the second inductor is a relation between a current change amount of the second inductor and an input voltage, a duty ratio of the switching tube, a switching frequency of the switching tube and an inductance value of the second inductor;
And obtaining the target frequency expression based on the first relation, the node current change relation, the current change relation of the first inductor and the current change relation of the second inductor.
2. The method of claim 1, wherein said driving operation of the switching tube of the dc chopper circuit based on the target frequency comprises:
Driving the switching tube of the direct current chopper circuit to operate based on the current frequency under the condition that the target frequency is equal to the current frequency of the direct current chopper circuit;
determining the sequence number of the open valley bottom of the switching tube under the condition that the target frequency is larger than a set value;
Obtaining a correction frequency based on the sequence number of the open valley bottom of the switching tube and the target frequency expression;
And driving the switching tube of the direct current chopper circuit to work based on the correction frequency.
3. The method of claim 1, wherein the deriving a first relationship between a maximum value of the diode current and the output current of the dc chopper circuit, a duty cycle of the dc chopper circuit, a resonant period, and the switching frequency based on the diode current comprises:
Obtaining a maximum value of the current of the diode, a duty cycle, a resonance period of the direct current chopper circuit and a second relation between the switching frequency and the output current of the direct current chopper circuit based on the current of the diode;
And sorting the second relation to obtain a first relation between the maximum value of the current of the diode and the output current of the direct current chopper circuit, the duty ratio of the direct current chopper circuit, the resonance period and the switching frequency.
4. The method of claim 1, wherein the obtaining the node current change relationship comprises:
Acquiring a node current relation when the switching tube is conducted, wherein the node current relation is the sum of the current of the first inductor and the current of the second inductor and is the current of the switching tube;
and obtaining a node current change relation based on the volt-second law and the node current relation.
5. The method of claim 1, wherein determining the current variation relationship of the first inductor comprises:
obtaining an inductance value of the first inductor based on the switching frequency of the switching tube and the inductance value of the first inductor;
obtaining an effective voltage of the first inductor based on the input voltage and a duty cycle of the switching tube;
And obtaining a current change relation of the first inductor based on the inductance value of the first inductor and the effective voltage of the first inductor.
6. The method of claim 1, wherein determining the current variation relationship of the second inductance comprises:
obtaining an inductance value of the second inductor based on the switching frequency of the switching tube and the inductance value of the second inductor;
obtaining an effective voltage of the second inductor based on the input voltage and the duty cycle of the switching tube;
And obtaining the current change relation of the second inductor based on the inductance value of the second inductor and the effective voltage of the second inductor.
7. The method of claim 1, wherein the deriving the target frequency expression based on the first relationship, the node current variation relationship, the current variation relationship of the first inductor, and the current variation relationship of the second inductor comprises:
obtaining a target relationship between the current change of the second inductor and the output current of the direct current chopper circuit, the duty ratio of the direct current chopper circuit, the resonance period, the switching frequency, the input voltage and the inductance value of the first inductor based on the first relationship, the node current change relationship and the current change relationship of the first inductor;
And obtaining the target frequency expression based on the target relation and the current change relation of the second inductor.
8. The method of claim 1, wherein the second inductor is a transformer, and wherein determining the current change relationship of the second inductor comprises:
obtaining an inductance value of the second inductor based on the switching frequency of the switching tube, the inductance value of the second inductor and the transformation ratio of the transformer;
obtaining an effective voltage of the second inductor based on the input voltage and the duty cycle of the switching tube;
And obtaining the current change relation of the second inductor based on the inductance value of the second inductor and the effective voltage of the second inductor.
9. A dc chopper circuit driven by a method as claimed in any one of claims 1 to 8.
10. The dc chopper circuit of claim 9, wherein the dc chopper circuit is a sepic dc chopper circuit.
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| CN114759797A (en) * | 2022-04-20 | 2022-07-15 | 昂宝电子（上海）有限公司 | Quasi-resonance switching power supply and control chip and control method thereof |
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| CN114759797A (en) * | 2022-04-20 | 2022-07-15 | 昂宝电子（上海）有限公司 | Quasi-resonance switching power supply and control chip and control method thereof |
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