CN110518807B - Method and system for adjusting resonant frequency of push-pull soft switching circuit - Google Patents

Method and system for adjusting resonant frequency of push-pull soft switching circuit Download PDF

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CN110518807B
CN110518807B CN201910733564.9A CN201910733564A CN110518807B CN 110518807 B CN110518807 B CN 110518807B CN 201910733564 A CN201910733564 A CN 201910733564A CN 110518807 B CN110518807 B CN 110518807B
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current
switching frequency
turn
switching
tube
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CN110518807A (en
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赵鹏
贾正胜
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Shenzhen Hpmont Technology Co Ltd
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Shenzhen Hpmont Technology Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/337—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only in push-pull configuration
    • H02M3/3376—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only in push-pull configuration with automatic control of output voltage or current
    • 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
    • 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

Abstract

The invention relates to the technical field of electronic circuits, in particular to a method and a system for adjusting the resonant frequency of a push-pull soft switching circuit, wherein the push-pull circuit comprises a first switching tube and a second switching tube, and the adjusting method comprises the following steps: detecting the turn-off current of the circuit when the on-off state of a first switch tube or a second switch tube is switched in real time; the switching frequency of the first switching tube and the switching frequency of the second switching tube are adjusted in real time according to the turn-off current and a preset switching frequency adjusting method, so that closed-loop adjustment is realized by continuously obtaining the turn-off current, the turn-off current is stabilized at the minimum turn-off current of the circuit, or the turn-off current floats near the minimum turn-off current of the circuit, the electric energy loss on the first switching tube and the second switching tube is reduced, and the electric energy is saved.

Description

Method and system for adjusting resonant frequency of push-pull soft switching circuit
Technical Field
The invention relates to the technical field of electronic circuits, in particular to a method and a system for adjusting the resonant frequency of a push-pull soft switching circuit.
Background
With the wide use of batteries, in the field of UPS or emergency power supply, a high-transformation-ratio high-power boosting technology is widely researched, wherein a high-frequency push-pull boosting topology is widely applied to a battery boosting link because the high-frequency push-pull boosting topology has a simple structure, high boosting efficiency and high output power and transmits energy outwards in the whole switching period.
In a boost circuit, particularly under the condition of a large transformation ratio, as shown in fig. 1, the low-voltage side current is large, so that the loss of a low-voltage side power device becomes the main loss of the circuit operation, and the loss mainly comes from the switching loss and the conduction loss of a boost MOSFET, and the copper loss and the iron loss of a boost transformer.
Disclosure of Invention
In order to solve the technical problem that the switching loss is large when a hardware control circuit is simply adopted in the prior art, the application provides a method and a system for adjusting the resonant frequency of a push-pull soft switching circuit, and the method and the system specifically comprise the following steps:
a method for adjusting a resonant frequency of a push-pull circuit, wherein the push-pull circuit comprises a first switch tube and a second switch tube, and the method comprises the following steps:
detecting the turn-off current of the circuit when the on-off state of a first switch tube or a second switch tube is switched in real time;
and adjusting the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method, so that the turn-off current is stabilized at the minimum turn-off current of the circuit.
The real-time adjustment of the switching frequencies of the first switching tube and the second switching tube according to the turn-off current and a preset switching frequency adjustment method comprises the following steps:
step 101: obtaining and recording the current of the current moment, and increasing the switching frequency;
step 102: acquiring corresponding turn-off current after the switching frequency is increased, judging whether the corresponding turn-off current after the switching frequency is increased is smaller than the corresponding turn-off current before the switching frequency is increased, if so, returning to the step 101, and if not, executing the step 103;
step 103: reducing the switching frequency;
step 104: and acquiring the corresponding turn-off current after the switching frequency is reduced, and judging whether the corresponding turn-off current after the switching frequency is reduced is smaller than the corresponding turn-off current before the switching frequency is reduced, if so, returning to the step 103, otherwise, returning to the step 101.
The real-time adjustment of the switching frequencies of the first switching tube and the second switching tube according to the turn-off current and a preset switching frequency adjustment method comprises the following steps:
step 201: obtaining and recording the turn-off current at the current moment, and reducing the switching frequency;
step 202: acquiring corresponding turn-off current after the switching frequency is reduced, and judging whether the corresponding turn-off current after the reduction is smaller than the corresponding turn-off current before the reduction, if so, returning to the step 201, otherwise, executing the step 203;
step 203: increasing the switching frequency;
step 204: and acquiring the corresponding turn-off current after the switching frequency is increased, and judging whether the corresponding turn-off current after the switching frequency is increased is smaller than the corresponding turn-off current before the switching frequency is increased, if so, returning to the step 203, and otherwise, returning to the step 201.
Further, the method also comprises the following steps:
and after the switching frequency is increased or reduced each time, judging whether the increased or reduced switching frequency is in a preset switching frequency range, and if not, judging that the circuit has a fault.
Wherein the preset adjustment amount is 3% -6% of the switching frequency range.
Wherein the upper and lower limits of the switching frequency range are obtained by:
respectively obtaining the maximum value and the minimum value of LC in the circuit, and substituting the maximum value of LC into the following formula to calculate the lower limit of the switching frequency; substituting the minimum value of LC into the following formula to calculate the upper limit of the switching frequency;
Figure BDA0002161418780000021
in the above formula, frIs the switching frequency.
A push-pull circuit resonant frequency adjustment system, the push-pull circuit including a first switch tube and a second switch tube, the system comprising: the device comprises an acquisition module and a processor;
the acquisition module is used for acquiring the turn-off current in the circuit when the on-off state of the first switch tube or the second switch tube is switched in real time and transmitting the acquired turn-off current to the processor;
the processor is used for adjusting the switching frequency of the first switching tube and the switching frequency of the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method, so that the turn-off current is stabilized at the minimum turn-off current of the circuit.
The processor is used for adjusting the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method and comprises the following steps:
the processor is used for adjusting the switching frequency of the first switching tube and the second switching tube, obtaining the turn-off current of the circuit before and after the switching frequency is adjusted, obtaining the variation trend of the turn-off current, and continuously adjusting the switching frequency of the first switching tube and the second switching tube according to the variation trend so as to reduce the turn-off current of the circuit.
Wherein, the obtaining of the turn-off current of the circuit before and after the switching frequency adjustment to obtain a variation trend of the turn-off current, and the continuing to adjust the switching frequencies of the first switching tube and the second switching tube according to the variation trend comprises:
obtaining the turn-off current of the circuit before and after the switching frequency is adjusted, if the adjusted turn-off current is smaller than the turn-off current before the adjustment, continuing to adjust the switching frequency of the first switching tube and the second switching tube according to the last adjustment mode, otherwise, continuing to adjust the switching frequency of the first switching tube and the second switching tube by adopting the adjustment mode opposite to the last time;
the adjustment mode comprises increasing the switching frequency of the first switching tube and the second switching tube and decreasing the switching frequency of the first switching tube and the second switching tube.
Preferably, the preset adjustment amount is 3% -6% of the switching frequency range.
According to the resonance frequency adjusting method of the push-pull soft switching circuit in the embodiment, the turn-off current of the first switching tube or the second switching tube in the circuit during switching of the on-off state is acquired in real time, and the switching frequency of the first switching tube and the second switching tube is adjusted in real time according to the preset switching frequency adjusting method, so that the turn-off current at the current moment floats near the minimum turn-off current value of the circuit, the switching loss is reduced, and the whole circuit is more energy-saving.
Drawings
FIG. 1 is a push-pull circuit diagram according to an embodiment of the present application;
FIG. 2 is a state diagram of an operation mode of a push-pull circuit according to an embodiment of the present application;
FIG. 3 is a diagram illustrating voltage and current states of a portion of a push-pull circuit according to an embodiment of the present application in modes 1-4;
FIG. 4 is a flowchart of an adjustment method according to an embodiment of the present application;
fig. 5 is a flowchart of a switching frequency adjustment method according to an embodiment of the present application;
fig. 6 is a flowchart of another switching frequency adjustment method according to an embodiment of the present application.
Detailed Description
The present invention will be described in further detail with reference to the following detailed description and accompanying drawings. Wherein like elements in different embodiments are numbered with like associated elements. In the following description, numerous details are set forth in order to provide a better understanding of the present application. However, those skilled in the art will readily recognize that some of the features may be omitted or replaced with other elements, materials, methods in different instances. In some instances, certain operations related to the present application have not been shown or described in detail in order to avoid obscuring the core of the present application from excessive description, and it is not necessary for those skilled in the art to describe these operations in detail, so that they may be fully understood from the description in the specification and the general knowledge in the art.
Furthermore, the features, operations, or characteristics described in the specification may be combined in any suitable manner to form various embodiments. Also, the various steps or actions in the method descriptions may be transposed or transposed in order, as will be apparent to one of ordinary skill in the art. Thus, the various sequences in the specification and drawings are for the purpose of describing certain embodiments only and are not intended to imply a required sequence unless otherwise indicated where such sequence must be followed.
A push-pull circuit is an output circuit connected between two transistors with different polarities. The push-pull circuit adopts two power BJT (bipolar junction transistor) tubes or MOSFET (metal-oxide-semiconductor field effect transistor) tubes with the same parameters, the two power BJT tubes or MOSFET tubes exist in the circuit in a push-pull mode, and are respectively responsible for positive and negative half-cycle waveform amplification tasks. The push-pull output can not only pour current into the load, but also draw current from the loadAnd taking the current. Referring to fig. 1, the present embodiment describes the method of the present application by taking a push-pull circuit as an example, where the push-pull circuit includes a first switch tube S1And a second switching tube S2And a power supply VinThe load circuit comprises a load capacitor CBAnd a load resistance RL. The push-pull circuit is divided according to the input side and the output side of a transformer thereof and comprises a low-voltage side circuit and a high-voltage side circuit, wherein the low-voltage side circuit comprises a first switching tube S1Inductor L1, second switch tube S2Power supply VinAnd a load R1. Power supply VinIs electrically connected with the midpoint of an inductor L1, and a power supply VinThe negative electrode series resistors R1 are connected with the first switch tube S1First pole and second switch tube S2A first pole of (1), a first switch tube S1Is connected to one end of an inductor L1, a second switching tube S2Is connected to the other end of the inductor L1. First switch tube S1Control electrode and second switch tube S2The control electrodes are all connected with the processor. The high-voltage side circuit comprises an inductor L2 (secondary winding of the transformer), an inductor Lr(leakage inductance of transformer in this embodiment), and a capacitor CrA first diode D1A second diode D2A third diode D3A fourth diode D4Capacitor CBAnd a load RL. One end of the inductor L2 passes through the inductor LrConnecting capacitor CrOne terminal of (C), a capacitorrIs connected with a first diode D1And a fourth diode D4The negative electrode of (1). First diode D1Negative pole of the first diode D is connected with the second diode D2Negative electrode of (1), capacitor CBAnd a load RLOne end of (a); second diode D2Is connected with the other end of the inductor L2 and a third diode D3Negative pole of (2), third diode D3Is connected with a fourth diode D4Positive electrode and capacitor CBAnother end of (1) and a load RLAnd the other end of the same. Capacitor CBAre respectively a first output terminal a and a second output terminal B. The first output end A and the second output end B are used for outputting the amplified voltage VB. The push-pull switchFour operation modes as shown in fig. 2 and a circuit schematic diagram of current in the circuit in each operation mode can appear in the circuit during operation, fig. 3 is a voltage and voltage change state in the circuit when the circuit operates in the four operation modes in fig. 2, and Vg1 and Vg2 in fig. 3 are diodes D in fig. 1 respectively1And D2Voltage of i1And i2Respectively represent the current on the first switch tube and the second switch tube, wherein CS1 and CS2 respectively represent the turn-off current on the first switch tube and the second switch tube, VS1And VS2Respectively representing the voltage, i, across the first and second switching tubesrRepresents the capacitor C in FIG. 1rCurrent flowing in, VdShows the diode D in FIG. 14Current of (V)BIs R in FIG. 1LThe voltage across the terminals. Wherein the first switch tube and the second switch tube work at a fixed switching frequency and are at S1And S2A certain dead zone is left between the two, and the switching frequency of the LC resonant frequency switching tube and the quality factor Q are reasonably set to ensure that the resonant current is in a discontinuous state. FIG. 2 shows four modes of circuit operation, mode 1, S1On, after a resonant half-cycle, the battery current approaches zero, at which point S is turned off1(ii) a In mode 2, S1And S2Are all turned off, due to the follow current of the transformer exciting current, at this time S1The junction capacitance on the switching tube will be charged to 2 times the battery voltage (battery voltage + transformer voltage) while S2The junction capacitance at is discharged to 0, at which time S2A zero voltage turn-on condition exists; in mode 3, S2Switching on at zero voltage state and S at zero current resonance2Turning off; mode 4, similar to mode 2, when S2The junction capacitance on the switch tube will be charged to 2 times the battery voltage while S1The junction capacitance on is discharged to 0. Thereby realizing S1And S2In mode 2 and mode 4, zero-voltage switching-on and zero-current switching-off of the switching tube are realized. The switching frequency is the on/off frequency of the first switching tube and the second switching tube, and when the switching frequency is equal to the resonant frequency of the circuit, the circuit works according to the four modes. In this embodiment, the circuit is further connectedThe sampling hold circuit is connected and used for detecting the current in the push-pull circuit in real time, particularly for detecting the turn-off current when the on-off state of a first switch tube or a second switch tube in the circuit is switched and outputting a current feedback signal.
In the push-pull circuit, particularly under the condition of a large transformation ratio, as the circuit shown in fig. 1, the low-voltage side current is large, which causes the loss of a low-voltage side power device to become the main loss of the circuit operation, and the loss mainly comes from the switching loss and the conduction loss of a boost MOSFET (metal-oxide-semiconductor field effect transistor), and the copper loss and the iron loss of a boost transformer, in the embodiment, the turn-off current when the on-off state of a first switch tube or a second switch tube in the circuit is switched is obtained in real time, and the switching frequencies of the first switch tube and the second switch tube are adjusted in real time according to the turn-off current and a preset switching frequency adjusting method, so that the turn-off current is stabilized at the minimum turn-off current of the circuit, closed-loop adjustment is realized by continuously obtaining the turn-off current, and the turn-off current flowing in the circuit is ensured to be stabilized at the minimum turn-off circuit when, or the turn-off current is enabled to float near the minimum turn-off current of the circuit, so that the electric energy loss on the first switch tube and the second switch tube can be reduced, and the electric energy is saved.
The first embodiment is as follows:
referring to fig. 4, the present embodiment provides a method for adjusting a resonant frequency of a push-pull circuit, including the following steps:
step 11: detecting the turn-off current of a first switch tube or a second switch tube in the circuit when the on-off state is switched in real time; in the working process of the push-pull circuit, the first switch tube and the second switch tube are alternately conducted, for example, a transient state can occur in the alternating conduction process of the first switch tube and the second switch tube, namely, the state that the first switch tube and the second switch tube are simultaneously conducted is detected, and the turn-off current when the on-off state of the first switch tube or the second switch tube is switched is detected in real time.
Step 12: and adjusting the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method, so that the turn-off current is stabilized at the minimum turn-off current of the circuit, or the turn-off current floats near the minimum turn-off current of the circuit. The switching frequency of the first switching tube and the switching frequency of the second switching tube are adjusted in real time according to the switching-off current detected in real time and a preset switching frequency adjusting method, so that compared with the switching-off circuit before adjustment, the switching-off current of the adjusted switching-off circuit always changes towards the direction of reduction, namely the switching-off current is stabilized at the minimum switching-off current of the circuit, and therefore the electric energy loss on the first switching tube and the second switching tube can be reduced.
Specifically, in this embodiment, two methods for adjusting the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off current are provided, where, as shown in fig. 5, the first method includes:
step 101: obtaining and recording the turn-off current at the current moment, and increasing the switching frequency corresponding to the current moment by a preset adjustment amount; wherein the current at the moment of current turn-off is recorded each time as a reference for turning off the circuit the next time.
Step 102: and acquiring the corresponding turn-off current after the switching frequency is increased, judging whether the corresponding turn-off current after the switching frequency is increased is smaller than the corresponding turn-off current before the switching frequency is increased, if so, returning to the step 101, and if not, executing the step 103. Wherein step 102 includes 1021 and 1022. If the corresponding turn-off current after the switching frequency is increased and the corresponding turn-off current after the switching frequency is increased is determined to be decreased, it is indicated that the switching frequency is decreased so that the turn-off current changes to be close to the minimum turn-off current, and therefore the step 101 is returned, and the switching frequency is continuously decreased so that the turn-off current is closer to the minimum turn-off current.
Step 103: reducing the switching frequency corresponding to the current moment by a preset adjustment amount; the switching frequency corresponding to the current moment can be reduced by twice the preset adjustment amount when the switching frequency is reduced for the first time, because the corresponding turn-off current is increased on the contrary after the switching frequency of the first switching tube and the second switching tube is increased by twice the preset adjustment amount, which indicates that the switching frequency needs to be reduced, and if the switching frequency is reduced by one time, the switching frequency is restored to a state without being increased, so that the sense is not provided, and therefore, the switching frequency corresponding to the current moment is reduced by twice the preset adjustment amount, and the adjustment is faster.
Step 104: and acquiring the corresponding turn-off current after the switching frequency is reduced, and judging whether the corresponding turn-off current after the switching frequency is reduced is smaller than the corresponding turn-off current before the switching frequency is reduced, if so, returning to the step 103, otherwise, returning to the step 101. Step 104 includes steps 1041 and 1042, similarly, if the corresponding off current decreases after the switching frequency is decreased, step 103 is returned to continue decreasing the switching frequency, if the corresponding off current increases after the switching frequency is decreased, it indicates that the off current deviates from the minimum off current, the switching frequency is reversely adjusted, that is, step 101 is returned to increase the switching frequency.
In addition, the present embodiment further provides a second method for adjusting the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off current, as shown in fig. 6, where the second method includes:
step 201: obtaining and recording the turn-off current at the current moment, and reducing the switching frequency corresponding to the current moment by a preset adjustment amount;
step 202: obtaining the turn-off current corresponding to the moment after the switching frequency is reduced, and judging whether the turn-off current corresponding to the moment after the switching frequency is reduced is smaller than the turn-off current corresponding to the moment before the switching frequency is reduced, if so, returning to the step 201, otherwise, executing the step 203; wherein step 203 includes 2031 and 2032.
Step 203: increasing the switching frequency corresponding to the current moment by a preset adjustment amount;
step 204: and acquiring the turn-off current corresponding to the moment after the switching frequency is increased, and judging whether the turn-off current corresponding to the moment after the switching frequency is increased is smaller than the turn-off current corresponding to the moment before the switching frequency is increased, if so, returning to the step 203, and otherwise, returning to the step 201. Wherein step 204 includes 2041 and 2042.
The second adjustment method is opposite to the first method, and firstly reduces the switching frequency, but the adjustment principles of the two methods are similar, and the switching frequency is adjusted to reduce the turn-off current as much as possible compared with the previous time by judging the change of the turn-off current before and after adjustment, so that the turn-off current is stabilized at the minimum turn-off current of the circuit, or the turn-off current floats near the minimum turn-off current of the circuit. The electric energy loss on the first switch tube and the second switch tube is reduced, and the electric energy is saved.
Wherein, increase at every turn or when reducing the switching frequency of first switch tube and second switch tube, in order to guarantee the adjustment speed, the difficult undersize of adjustment volume at every turn, avoided the adjustment too big simultaneously to lead to the turn-off current to miss minimum turn-off current, adjustment volume at every turn should not too big yet, wherein minimum turn-off current is different according to actual circuit and design, minimum turn-off current design undersize can exceed detection circuitry's precision range, set up too big then can not play soft switching's effect. This embodiment is implemented by multiple times, and it is most suitable to set the preset adjustment amount to 3% -6% of the switching frequency range, for example, in this embodiment, the preset adjustment amount is set to 5% of the switching frequency range. For example, in the switching frequency range of 10-30Hz, the adjustment amount is set to 1Hz, i.e. the switching frequency is increased or decreased by 1Hz each time.
The upper limit and the lower limit of a switching frequency range in the circuit are obtained by the following method:
respectively obtaining the maximum value and the minimum value of LC in the circuit, and substituting the maximum value of LC into the following formula to calculate the lower limit of the switching frequency; substituting the minimum value of LC into the following formula to calculate the upper limit of the switching frequency, wherein LC in the embodiment is Lr and Cr in FIG. 1;
Figure BDA0002161418780000071
in the above formula, frThe switching frequency is the switching frequency, so that the switching frequency range of the circuit can be obtained through the method, the preset adjustment amount is further set, the switching frequency is adjusted through the adjustment, and the fact that the turn-off circuit is stabilized at the minimum turn-off current of the circuit is guaranteed.
The LC is an overall value of all inductors and capacitors in the low-voltage side circuit, and the calculation method is the same as that of the LC in the existing LC oscillating circuit, and is not described herein again.
The switching frequency range of the circuit is obtained, namely the upper limit and the lower limit of the theoretical change of the switching frequency are determined, the switching frequency can be changed in the switching frequency range in the working process and cannot exceed the upper limit and the lower limit, whether the increased or decreased switching frequency is in the preset switching frequency range is judged after the switching frequency is increased or decreased every time, if not, the switching frequency is beyond the maximum adjusting range, the current circuit is judged to be in fault, and an alarm signal is sent out after the circuit is in fault, for example, an alarm sound or a fault lamp flickers, so that a worker is reminded of timely processing.
Example two
The embodiment provides a push-pull circuit resonant frequency adjusting system, which is described by taking a circuit shown in fig. 1 as an example, and includes an acquisition module and a processor, wherein the acquisition module includes a sampling protection circuit, and two ends of the acquisition circuit are connected in parallel to two ends of a load resistor in the push-pull circuit, and are used for acquiring a turn-off current in real time when the on-off state of a first switch tube or a second switch tube in the circuit is switched, and sending the acquired turn-off current to the processor.
The processor is connected with the acquisition module and the control ends of the first switching tube and the second switching tube and is used for adjusting the switching frequency of the first switching tube and the switching frequency of the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method so that the turn-off current is stabilized at the minimum turn-off current of the circuit; or the off current is made to float around the minimum off current value of the circuit, the processor of the present embodiment adopts a Stm32f103C8T6 chip.
The processor is used for adjusting the switching frequency of the first switching tube and the switching frequency of the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method and comprises the following steps:
step 301: the processor is used for acquiring and recording the turn-off current at the current moment;
step 302: the processor is also used for increasing the switching frequency by a preset adjustment amount; acquiring corresponding turn-off current after the switching frequency is increased, and judging whether the corresponding turn-off current after the switching frequency is increased is smaller than the corresponding turn-off current before the switching frequency is increased, if so, returning to the step 301, otherwise, executing the step 303;
step 303: the processor is also used for reducing the switching frequency by a preset adjustment amount; and acquiring the corresponding turn-off current after the switching frequency is reduced, judging whether the corresponding turn-off current after the switching frequency is reduced is smaller than the corresponding turn-off current before the switching frequency is reduced, if so, continuing to execute the step 303, and otherwise, returning to the step 301.
Or, the processor is configured to adjust the switching frequencies of the first switching tube and the second switching tube in real time according to the turn-off current and a preset switching frequency adjustment method, and includes:
step 401: the processor is used for acquiring and recording the current of the current moment,
step 402: the processor is also used for reducing the switching frequency by a preset adjustment amount; obtaining the corresponding turn-off current after the switching frequency is reduced, and judging whether the corresponding turn-off current after the switching frequency is reduced is smaller than the corresponding turn-off current before the switching frequency is reduced, if so, continuing to execute the step 402, otherwise, executing the step 403;
step 403: the processor is also used for increasing the switching frequency by a preset adjustment amount; and acquiring the corresponding turn-off current after the switching frequency is increased, and judging whether the corresponding turn-off current after the switching frequency is increased is smaller than the corresponding turn-off current before the switching frequency is increased, if so, continuing to execute the step 403, otherwise, returning to the step 401.
In the method, the preset adjustment amount of each increase or decrease is 3% -6% of the switching frequency range of the first switching tube or the second switching tube.
Wherein, a program is preset in the processor, and executing the program can adjust the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off circuit and a preset switching frequency adjusting method, wherein the adjusting method is the same as that in embodiment 1, and is not described herein again.
In addition, the system also comprises a fault alarm module connected with the processor, the fault alarm module can be a buzzer and an alarm lamp, after the switching frequency is increased or decreased every time, the processor also judges whether the increased or decreased switching frequency is in a preset switching frequency range, if the switching frequency is not beyond the maximum adjusting range, the current circuit is judged to have a fault, a fault signal is output to the fault alarm module, and the fault alarm module sends out an alarm sound or the alarm lamp flickers to remind a worker that the current circuit has a fault.
The present invention has been described in terms of specific examples, which are provided to aid understanding of the invention and are not intended to be limiting. For a person skilled in the art to which the invention pertains, several simple deductions, modifications or substitutions may be made according to the idea of the invention.

Claims (10)

1. A method for adjusting the resonant frequency of a push-pull circuit,
the push-pull circuit comprises a power supply VinA load capacitor CBAnd a load resistance RLThe push-pull circuit further comprises a low-voltage side circuit and a high-voltage side circuit, wherein the low-voltage side circuit comprises a first switch tube S1Inductor L1, second switch tube S2Power supply VinAnd a load R1, a power supply VinIs electrically connected with the midpoint of an inductor L1, and a power supply VinThe negative electrode series resistors R1 are connected with the first switch tube S1First pole and second switch tube S2A first pole of (1), a first switch tube S1Is connected to one end of an inductor L1, a second switching tube S2Is connected with the other end of the inductor L1, and the high-voltage side circuit comprises an inductor L2 and an inductor LrCapacitor CrA first diode D1A second diode D2A third diode D3A fourth diode D4Capacitor CBAnd a load RLOne end of the inductor L2 passes through the inductor LrConnecting capacitor CrOne terminal of (C), a capacitorrIs connected with a first diode D1And a fourth diode D4Negative electrode of (1), first diode D1Negative pole of the first diode D is connected with the second diode D2Negative electrode of (1), capacitor CBAnd a load RLOne end of (a); second diode D2Is connected with the other end of the inductor L2 and a third diode D3Negative pole of (2), third diode D3Positive electrode of (2) is connected with the fourthDiode D4Positive electrode and capacitor CBAnother end of (1) and a load RLAnother terminal of (1), a capacitor CBIs respectively a first output end A and a second output end B, the first output end A and the second output end B are used for outputting the amplified voltage VB；
The adjusting method comprises the following steps:
detecting the turn-off current of the circuit when the on-off state of a first switch tube or a second switch tube is switched in real time;
and adjusting the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method, so that the turn-off current is stabilized at the minimum turn-off current of the circuit.
2. The adjusting method of claim 1, wherein the adjusting the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method comprises:
step 101: obtaining and recording the current of the current moment, and increasing the switching frequency;
step 102: acquiring corresponding turn-off current after the switching frequency is increased, judging whether the corresponding turn-off current after the switching frequency is increased is smaller than the corresponding turn-off current before the switching frequency is increased, if so, returning to the step 101, and if not, executing the step 103;
step 103: reducing the switching frequency;
step 104: and acquiring the corresponding turn-off current after the switching frequency is reduced, and judging whether the corresponding turn-off current after the switching frequency is reduced is smaller than the corresponding turn-off current before the switching frequency is reduced, if so, returning to the step 103, otherwise, returning to the step 101.
3. The adjusting method of claim 1, wherein the adjusting the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method comprises:
step 201: obtaining and recording the turn-off current at the current moment, and reducing the switching frequency;
step 202: acquiring corresponding turn-off current after the switching frequency is reduced, and judging whether the corresponding turn-off current after the reduction is smaller than the corresponding turn-off current before the reduction, if so, returning to the step 201, otherwise, executing the step 203;
step 203: increasing the switching frequency;
step 204: and acquiring the corresponding turn-off current after the switching frequency is increased, and judging whether the corresponding turn-off current after the switching frequency is increased is smaller than the corresponding turn-off current before the switching frequency is increased, if so, returning to the step 203, and otherwise, returning to the step 201.
4. The adjustment method according to claim 2 or 3, further comprising:
and after the switching frequency is increased or reduced each time, judging whether the increased or reduced switching frequency is in a preset switching frequency range, and if not, judging that the circuit has a fault.
5. The method of adjusting of claim 4, wherein the predetermined amount of adjustment is 3% -6% of the switching frequency range.
6. The adjustment method according to claim 5, characterized in that the upper and lower limits of the switching frequency range are obtained by:
respectively obtaining the maximum value and the minimum value of LC in the circuit, and substituting the maximum value of LC into the following formula to calculate the lower limit of the switching frequency; substituting the minimum value of LC into the following formula to calculate the upper limit of the switching frequency;
Figure FDA0002635503270000021
in the above formula, frIs the switching frequency.
7. A push-pull circuit resonant frequency adjustment system is characterized in that the push-pull circuit comprises a power supply VinA load capacitor CBAnd a load resistance RLThe push-pull circuit further comprises a low-voltage side circuit and a high-voltage side circuit, wherein the low-voltage side circuit comprises a first switch tube S1Inductor L1, second switch tube S2Power supply VinAnd a load R1, a power supply VinIs electrically connected with the midpoint of an inductor L1, and a power supply VinThe negative electrode series resistors R1 are connected with the first switch tube S1First pole and second switch tube S2A first pole of (1), a first switch tube S1Is connected to one end of an inductor L1, a second switching tube S2Is connected with the other end of the inductor L1, and the high-voltage side circuit comprises an inductor L2 and an inductor LrCapacitor CrA first diode D1A second diode D2A third diode D3A fourth diode D4Capacitor CBAnd a load RLOne end of the inductor L2 passes through the inductor LrConnecting capacitor CrOne terminal of (C), a capacitorrIs connected with a first diode D1And a fourth diode D4Negative electrode of (1), first diode D1Negative pole of the first diode D is connected with the second diode D2Negative electrode of (1), capacitor CBAnd a load RLOne end of (a); second diode D2Is connected with the other end of the inductor L2 and a third diode D3Negative pole of (2), third diode D3Is connected with a fourth diode D4Positive electrode and capacitor CBAnother end of (1) and a load RLAnother terminal of (1), a capacitor CBIs respectively a first output end A and a second output end B, the first output end A and the second output end B are used for outputting the amplified voltage VB；
The system comprises: the device comprises an acquisition module and a processor;
the acquisition module is used for acquiring the turn-off current in the circuit when the on-off state of the first switch tube or the second switch tube is switched in real time and transmitting the acquired turn-off current to the processor;
the processor is used for adjusting the switching frequency of the first switching tube and the switching frequency of the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method, so that the turn-off current is stabilized at the minimum turn-off current of the circuit.
8. The adjusting system of claim 7, wherein the processor is configured to adjust the switching frequency of the first switching tube and the second switching tube in real time according to the turn-off current and a preset switching frequency adjusting method, and comprises:
the processor is used for adjusting the switching frequency of the first switching tube and the second switching tube, obtaining the turn-off current of the circuit before and after the switching frequency is adjusted, obtaining the variation trend of the turn-off current, and continuously adjusting the switching frequency of the first switching tube and the second switching tube according to the variation trend so as to reduce the turn-off current of the circuit.
9. The adjusting system of claim 8, wherein the obtaining of the turn-off current of the circuit before and after the adjustment of the switching frequency to obtain a variation trend of the turn-off current, and the continuing to adjust the switching frequency of the first switching tube and the second switching tube according to the variation trend comprises:
obtaining the turn-off current of the circuit before and after the switching frequency is adjusted, if the adjusted turn-off current is smaller than the turn-off current before the adjustment, continuing to adjust the switching frequency of the first switching tube and the second switching tube according to the last adjustment mode, otherwise, continuing to adjust the switching frequency of the first switching tube and the second switching tube by adopting the adjustment mode opposite to the last time;
the adjustment mode comprises increasing the switching frequency of the first switching tube and the second switching tube and decreasing the switching frequency of the first switching tube and the second switching tube.
10. The adjustment system of claim 8, wherein the preset adjustment amount is 3% -6% of the switching frequency range.
CN201910733564.9A 2019-08-09 2019-08-09 Method and system for adjusting resonant frequency of push-pull soft switching circuit Active CN110518807B (en)

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