CN111628654A - Switching power supply circuit - Google Patents
Switching power supply circuit Download PDFInfo
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- CN111628654A CN111628654A CN201910151825.6A CN201910151825A CN111628654A CN 111628654 A CN111628654 A CN 111628654A CN 201910151825 A CN201910151825 A CN 201910151825A CN 111628654 A CN111628654 A CN 111628654A
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- 238000005070 sampling Methods 0.000 claims description 107
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- 238000000034 method Methods 0.000 description 11
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- 238000010586 diagram Methods 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 5
- 230000003071 parasitic effect Effects 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 3
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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
- H02M3/33569—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 having several active switching elements
- H02M3/33576—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 having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
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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
- H02M1/14—Arrangements for reducing ripples from dc input or output
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
- H02M1/0054—Transistor switching losses
- H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The invention relates to a switching power supply circuit, comprising: the main circuit comprises a transformer, a primary winding of the transformer is connected with a first switching tube in series, a secondary winding of the transformer is connected with a second switching tube in series, and a resonant capacitor is connected between the second switching tube and the secondary winding and connected with the secondary winding in parallel; the control circuit is connected with the control end of the first switch tube on one hand and used for controlling the first switch tube to be switched on and off, and is connected with the control end of the second switch tube on the other hand and used for controlling the second switch tube to be switched off when the secondary side current is reduced to zero during the conduction period of the first switch tube, and controlling the second switch tube to be switched on when the resonant capacitor is charged during the switching off period of the second switch tube. The switching power supply uses the switching tube for rectification, and compared with the traditional diode rectification, the rectification loss of the circuit can be reduced.
Description
Technical Field
The invention relates to the field of switching power supplies, in particular to a switching power supply circuit.
Background
The switching power supply circuit generally comprises a power conversion circuit at an input end and a rectification filter circuit at an output end, wherein the power conversion circuit comprises a transformer and a switching tube connected with the transformer, and power conversion is performed by controlling the on and off of the switching tube; the rectifying and filtering circuit comprises a rectifying diode and outputs direct current by utilizing the unidirectional conduction characteristic of the diode. Fig. 1 shows a switching power supply circuit in the conventional technology, in which a switching tube Q is connected to a primary winding of a transformer, and a rectifying diode D is connected to a secondary winding of the transformer to control on and off of the switching tube Q, and during the on and off process of the switching tube Q, when a current of the secondary winding is positive, the rectifying diode is turned on, and when a current of the secondary winding is negative, the rectifying diode is turned off, so that the unidirectional conduction of the diode is used to perform rectification to output a direct current. However, since the rectifier diode has a certain on-resistance, the rectifier diode also generates a certain loss during the operation of the switching power supply circuit, which increases the overall power consumption of the switching power supply circuit and is not favorable for increasing the power density of the switching power supply circuit.
Disclosure of Invention
In view of this, it is necessary to provide a new switching power supply circuit in order to solve the problem of a large loss of the rectifier diode in the switching power supply circuit.
A switching power supply circuit comprising:
the main circuit comprises a transformer, a resonant capacitor, a first switching tube and a second switching tube, wherein the transformer comprises a primary winding and a secondary winding, the primary winding is connected with the input end and the output end of the first switching tube in series to form a primary branch, the primary branch is used for being connected with an input power supply, the secondary winding is connected with the input end and the output end of the second switching tube in series to form a secondary branch, the resonant capacitor is connected between the second switching tube and the secondary winding and connected with the secondary winding in parallel, and the secondary branch is used for being connected with a load;
the control circuit controls the connection and disconnection of the first switching tube and the second switching tube, wherein when the first switching tube is connected and the current flowing from the input end of the second switching tube to the output end of the second switching tube is reduced to zero, the second switching tube is controlled to be disconnected; and when the first switching tube is switched off and the resonant capacitor is charged, the second switching tube is controlled to be switched on.
Above-mentioned switching power supply circuit, vice limit branch road adopt the second switch tube to carry out the rectification, because second switch tube itself does not possess one-way conduction characteristic, in order to utilize the second switch tube to carry out the rectification, this application adopts switching on and the shutoff of control circuit in good time control second switch tube. In the switching and switching-off process of the first switching tube, the current of the secondary side branch is controlled by the current of the primary side branch to fluctuate, the current flowing from the input end of the second switching tube to the output end of the second switching tube in the secondary side branch is defined as forward current, the current in the secondary side branch in the direction opposite to the direction of the forward current is defined as reverse current, after the first switching tube is switched on, the forward current in the secondary side branch gradually decreases, and when the forward current in the secondary side branch decreases to zero, the second switching tube is controlled to be switched off, which is equivalent to that when the secondary side branch generates reverse current in the prior art, a diode is switched off; after the first switch tube is turned off, the secondary resonant capacitor resonates with an inductor in the circuit, such as a leakage inductor of a transformer, the resonant capacitor is charged in a forward direction after being discharged in a reverse direction in the resonant process, when the resonant capacitor is charged, the charging current is a forward current, the control circuit controls the second switch tube to be conducted, and when the secondary branch circuit generates the forward current in the traditional technology, the diode is conducted. The on-off of the second switching tube is timely controlled by the control circuit, so that the second switching tube has a rectifying characteristic and can replace a traditional rectifying diode. Meanwhile, the second switch tube has lower on-resistance compared with the rectifier diode, so that the forward voltage drop of the second switch tube is smaller and the rectification loss is lower in the working process of the switching power supply circuit, and the overall power consumption of the switching power supply circuit is favorably reduced.
In one embodiment, the main circuit further comprises a resonant inductor, and the resonant inductor is connected in series in the primary side branch.
In one embodiment, in the primary side branch, an input end of the resonant inductor is configured to be connected to an input power supply, an output end of the resonant inductor is connected to a first end of the primary side winding, a second end of the primary side winding is connected to an input end of the first switching tube, and an output end of the first switching tube is grounded;
in the secondary branch, a third end of the secondary winding is connected with an input end of the second switching tube, a fourth end of the secondary winding and an output end of the second switching tube are used for connecting a load, the resonant capacitor is connected with the secondary winding in parallel, one end of the resonant capacitor is connected with the input end of the second switching tube, and the second end and the third end are homonymous ends.
In one embodiment, the main circuit further includes an input filter capacitor and an output filter capacitor, the input filter capacitor is connected between the input end of the resonant inductor and ground, and the output filter capacitor is connected between the output end of the second switching tube and the fourth end of the secondary winding.
In one embodiment, the control circuit is configured to control the second switching tube to conduct when a potential between the input terminal of the second switching tube and the output terminal of the second switching tube drops to zero during charging of the resonant capacitor.
In one embodiment, the control circuit is configured to control the first switching tube to be turned on when a potential between the input terminal and the output terminal of the first switching tube is at a valley, and to control the first switching tube to be turned off when a current flowing through the first switching tube is zero.
In one embodiment, the transformer further comprises a primary side auxiliary winding, the main circuit further comprises a first sampling resistor, a second sampling resistor and a delay resistor, the first sampling resistor and the second sampling resistor are connected in series between a fifth end and a sixth end of the primary side auxiliary winding, the sixth end of the primary side auxiliary winding is grounded, one end of the first sampling resistor connected with the second sampling resistor is used as a first sampling point, one end of the delay resistor is connected with the first sampling point, the other end of the delay resistor is used as a second sampling point, and the fifth end of the primary side auxiliary winding and the third end of the secondary side winding are homonymous ends;
the control circuit comprises a sampling module, a calculating module and a driving module, wherein the sampling module is respectively connected with the first sampling point and the second sampling point to sample a first sampling voltage of the first sampling point and a second sampling voltage of the second sampling point, the calculating module comprises a comparator, the positive input end of the comparator is connected with the first sampling voltage, the negative input end of the comparator is connected with the second sampling voltage, and the driving module is connected with the calculating module and used for controlling the conduction of the second switching tube when the output end of the comparator jumps from a high level to a low level; the calculation module is further used for calculating a first inflection point of the first sampling voltage during the conduction period of the first switching tube, and the driving module is used for controlling the second switching tube to be turned off at the inflection point.
In one embodiment, the calculating module further includes a delay circuit and an xor gate, an output end of the comparator is connected to a first input end of the xor gate on the one hand, and is connected to an input end of the delay circuit on the other hand, an output end of the delay circuit is connected to a second input end of the xor gate, and the driving module is configured to control the second switch tube to be turned on when the output end of the xor gate outputs a high level, and keep a state of the second switch tube unchanged when the output end of the xor gate outputs a low level.
In one embodiment, the second sampling voltage is delayed by 1ns to 2ns compared with the first sampling voltage.
In one embodiment, the main circuit further includes a third sampling resistor, the primary winding is sequentially connected in series with the first switching tube and the third sampling resistor and then grounded, one end of the third sampling resistor connected to the first switching tube is used as a third sampling point, the control circuit is configured to sample a third sampling voltage at the third sampling point, and is configured to control the first switching tube to be turned on when the third sampling voltage reaches an even number of zero points, and control the first switching tube to be turned off when the third sampling voltage reaches the even number of zero points during the turn-on period of the first switching tube.
Drawings
FIG. 1 is a circuit diagram of a switching power supply according to a conventional technique;
FIG. 2 is a circuit diagram of a switching power supply according to an embodiment of the present invention;
FIG. 3 is a circuit diagram of a switching power supply according to another embodiment of the present invention;
FIG. 4 is a waveform diagram of the related current and voltage during a control period of the switching power supply circuit according to an embodiment of the present invention;
FIG. 5 is a block diagram of a computing module architecture in accordance with an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating waveform processing in a computing module according to an embodiment of the invention;
fig. 7 is a schematic diagram of a secondary side branch resonant capacitor and parasitic inductor resonant circuit according to an embodiment of the invention.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Fig. 2 shows a switching power supply circuit according to an embodiment of the present application, which includes a main circuit and a control circuit. The main circuit comprises a transformer Lp, a resonant capacitor Cr, a first switching tube Q1 and a second switching tube Q2, the transformer Lp comprises a primary winding Np and a secondary winding Ns, the primary winding Np and the input end and the output end of the first switching tube Q1 are connected in series to form a primary branch, the primary branch is used for being connected with an input power supply, current of the input power supply sequentially flows through the input end and the output end of the first switching tube Q1 and then flows back to the input power supply, the secondary winding Ns is connected in series with the input end and the output end of the second switching tube Q2 to form a secondary branch, in the secondary branch, the resonant capacitor Cr is connected between the second switching tube Q2 and the secondary winding Ns and connected in parallel with the secondary winding Ns, the secondary branch is used for being connected with an external load and providing an output voltage V for the external loadOThe induced current generated by the secondary winding Ns flows into the external load after sequentially passing through the input terminal and the output terminal of the second switching tube Q2. The control circuit is connected to the control terminal of the first switching tube Q1 for outputting a first control signal duty to control the on/off of the first switching tube Q1, and connected to the control terminal of the second switching tube Q2 for outputting a second control signal duty sr to control the on/off of the second switching tube Q2. The control of the second switch tube Q2, specifically, during the on-state of the first switch tube Q1, when the current flowing from the input end to the output end of the second switch tube Q2 drops to zero, the second switch tube Q2 is controlled to be turned off, and during the off-state of the first switch tube Q1, the resonant capacitor Cr resonates with the inductor in the circuit, the resonant capacitor Cr is charged in the forward direction after being discharged in the reverse direction, and when the resonant capacitor Cr is charged in the forward direction, the second switch tube Q2 is controlled to be turned on.
In the present application, the control circuit controls the on and off of the first switching tube Q1 by the first control signal duty, the primary side current Ip fluctuates during the on and off period of the first switching tube Q1, and the secondary side branch is controlled by the primary side branch and the secondary side current IDWill fluctuate as well, since the second switching transistor Q2 for rectification in the secondary branch itself does not have the conventional rectifying diodeThe unidirectional conduction characteristic of the tube can not be automatically switched off and switched on according to the fluctuation of the current, so that a control circuit is required to timely control the on and off of the second switching tube Q2 and define the secondary current I in the secondary branchDThe direction from the input end to the output end of the second switch tube Q2 is positive, otherwise, the direction is reverse, when the secondary side current IDWhen the current is reversed, the second switch tube Q2 is turned off, and the secondary side current I isDIn the forward direction, the second switching tube Q2 is turned on. The control circuit is used for timely controlling the on and off of the second switching tube Q2, and specifically comprises: after the first switch tube Q1 is turned on, the primary current Ip will rise, and the secondary current I in the positive directionDWill drop when the secondary side current IDWhen the current drops to zero, the current is the secondary side current IDWhen the reverse direction is about to occur, the control circuit is used for judging the secondary side current IDWhether the voltage drops to zero or not, if so, controlling the second switching tube Q2 to be switched off; after the first switch tube Q1 is turned off, the resonant capacitor Cr resonates with an inductor in the circuit, such as a leakage inductance of the transformer Lp, the resonant capacitor Cr is charged in a forward direction after being discharged in a reverse direction, a current generated by the charging in the forward direction is a forward current, the control circuit is used for judging whether the resonant capacitor is charged in the forward direction, and if the resonant capacitor is charged in the forward direction, the second switch tube Q2 is controlled to be switched on. During the control process, when the secondary side current IDWhen the current is reversed, the second switch tube Q2 is turned off, and the secondary side current I isDIn the forward direction, the second switch Q2 is turned on, which is equivalent to that the rectifying diode in the conventional technology is turned off when receiving the reverse current and turned on when receiving the forward current, thereby realizing the rectifying function of the secondary branch. In the present application, the second switching tube Q2 is sampled for rectification, and since the second switching tube Q2 has a lower on-resistance than a conventional diode, the on-voltage drop is lower, and the rectification loss is smaller.
In one embodiment, as shown in fig. 3, the main circuit further includes a resonant inductor Lres, and the resonant inductor Lres is connected in series in the primary side branch. In the switching power supply circuit, the leakage inductance exists in the transformer Lp, the leakage inductance can participate in resonance, and when the leakage inductance of the current transformer Lp meets the requirement of resonance frequency, the extra resonance inductance Lres is not needed. When the resonant frequency is required to be in the megahertz level, the required resonant inductance Lres is in the microhenry level, and the leakage inductance of the transformer Lp is generally in the nanohenry level and is smaller than the required resonant inductance Lres, so that the additional resonant inductance Lres needs to be added to enable the resonant parameters to meet the requirements.
In a specific embodiment, as shown in fig. 3, the primary side branch of the main circuit is: the input end of the resonant inductor Lres serves as the input end of the switching power supply circuit and is used for being connected with an input power supply, the output end of the resonant inductor Lres is connected with the first end of the primary winding Np, the second end of the primary winding Np is connected with the input end of the first switching tube Q1, and the output end of the first switching tube Q1 is grounded; the secondary branch of the main circuit is as follows: the third end of the secondary winding Ns is connected with the input end of the second switching tube Q2, the fourth end of the secondary winding Ns and the output end of the second switching tube Q2 are used as the output end of the switching power supply circuit and are used for connecting a load, one end of the resonant capacitor Cr is connected with the input end of the second switching tube Q2, the resonant capacitor Cr is connected with the secondary winding Ns in parallel, and the second end of the primary winding Np and the third end of the secondary winding Ns are the same-name ends. In this embodiment, in the primary side branch, a direction from the input end of the resonant inductor Lres to the output end of the resonant inductor Lres is defined as a forward direction, and vice versa. When the control circuit controls the first switch tube Q1 to be conducted, the primary side current Ip is a forward current and gradually increases, and the secondary side current IDIs a forward current and gradually decreases when the secondary side current IDWhen the current is reduced to zero, the control circuit controls the second switch tube Q2 to be switched off, which is equivalent to the secondary side current IDIn the reverse direction, the diode is turned off. And then the first switch tube Q1 is controlled to be turned off, during the turn-off period of the first switch tube Q1, the resonant capacitor Cr, the leakage inductance of the transformer Lp, the resonant inductor Lres and the output capacitor Coss of the first switch tube Q1 form a resonant loop, the resonant capacitor Cr is charged in the forward direction after being discharged in the reverse direction, a forward charging current is formed in the charging process of the resonant capacitor Cr, at the moment, the control circuit conducts the second switch tube Q2, and when the forward current is induced by the secondary side branch circuit, the diode is conducted. The on and off of the second switching tube Q2 are timely controlled by the control circuit to realize the rectification characteristic of the secondary side branch.
In one embodiment, as shown in fig. 3, the main circuit further includes an input filter capacitor C1 and an output filter capacitor CLFilter for filtrationThe wave capacitor C1 is arranged in the primary side branch and connected between the input end of the resonant inductor Lres and the ground, and the output filter capacitor CLAnd is located in the secondary branch and connected between the output terminal of the second switching tube Q2 and the fourth terminal of the secondary winding Ns. By arranging an input filter capacitor C1 and an output filter capacitor CLThe filter can filter the input electric signal and the output electric signal to generate stable direct current. In an embodiment, as shown in fig. 3, the primary side branch further includes a rectifier bridge, an output end of the rectifier bridge is connected to an input end of the resonant inductor Lres, an input end of the rectifier bridge is used as an input end of the switching power supply circuit, and the switching power supply circuit can be connected with an alternating current, an external alternating current is rectified by the rectifier bridge and then is converted into a direct current, and then pulse width modulation is performed to obtain a required output voltage.
In an embodiment, the control circuit is configured to control the second switching transistor Q2 to be turned on, and in particular, to control the second switching transistor Q2 to be turned on when the potential between the input terminal and the output terminal of the second switching transistor Q2 drops to zero during the charging process of the resonant capacitor Cr. In the forward charging process of the resonant capacitor Cr, the voltage V at two ends of the resonant capacitor CrCrAnd when the potential between the output end and the output end of the second switch tube Q2 is reduced to zero, the second switch tube Q2 is controlled to be switched on. Because the Switching tube has Switching loss in the Switching process, in order to reduce the Switching loss, a soft Switching technology is generally adopted at present, and the soft Switching technology refers to a Zero Voltage Switching (ZVS) or a Zero Current Switching (ZCS), when the Voltage is Zero, the device is switched on, and when the Current is Zero, the device is switched off, so that the Switching loss is Zero, and the power consumption of the circuit is reduced. In this embodiment, the second switching tube Q2 in the switching power supply circuit is turned off when the current drops to zero and turned on when the voltage drops to zero, so as to implement Zero Voltage Switching (ZVS) or Zero Current Switching (ZCS), reduce the switching loss of the second switching tube Q2, and further reduce the power consumption of the circuit. In one embodiment, when the resonant capacitor Cr is directly connected to the external load through the second switch tube Q2, the voltage of the resonant capacitor Cr rises to the output voltage V of the switching power supply circuitOWhen the temperature of the water is higher than the set temperature,the potential between the input and output of the second switching tube Q2 is zero.
In an embodiment, the control circuit is configured to control the first switching transistor Q1 to turn on and off, specifically, to control the first switching transistor Q1 to turn on when the potential between the input terminal and the output terminal of the first switching transistor Q1 is at the valley, and to control the first switching transistor Q1 to turn off when the current flowing through the first switching transistor Q1 is zero. The switching of the first switching tube is designed to be in a soft switching mode, Zero Voltage Switching (ZVS) or Zero Current Switching (ZCS) is realized, the switching loss of the first switching tube Q1 is reduced, and the power consumption of the circuit is further reduced.
In the above embodiment, the control circuit controls the on and off of the second switching tube Q2 according to the current and voltage information in the main circuit, and specifically, the control circuit may directly acquire the required voltage and current information, or may indirectly acquire the required voltage or current information. In a specific embodiment, as shown in fig. 3, in the main circuit, the transformer Lp further includes a primary side auxiliary winding Naux, the main circuit further includes a first sampling resistor R1, a second sampling resistor R2 and a delay resistor Rs, the first sampling resistor R1 and the second sampling resistor R2 are connected in series between a fifth end and a sixth end of the primary side auxiliary winding Naux, the sixth end of the primary side auxiliary winding Naux is grounded, one end of the first sampling resistor R1 connected to the second sampling resistor R2 serves as a first sampling point, one end of the delay resistor Rs is connected to the first sampling point, the other end of the delay resistor Rs serves as a second sampling point, and the fifth end of the primary side auxiliary winding Naux and the third end of the secondary winding Ns are homonymous ends; in the control circuit, the control circuit comprises a sampling module, a calculating module and a driving circuit module, wherein the sampling module is connected with the first sampling point to sample a first sampling voltage Vsense of the first sampling point, the sampling module is further connected with the second sampling point to sample a second sampling voltage V 'sense of the second sampling point, the calculating module comprises a comparator, a positive input end of the comparator is connected with the first sampling voltage Vsense, a negative input end of the comparator is connected with the second sampling voltage V' sense, the driving module is connected with the calculating module and used for controlling the second switching tube Q2 to be switched on when an output end of the comparator jumps from a high level to a low level, the calculating module is further used for calculating a first inflection point of the first sampling voltage Vsense during the switching-on period of the first switching tube Q1, and the driving module is used for controlling the second switching tube Q2 to be switched off at the inflection point. In this embodiment, adopt the primary side modulation mode, adopt the primary side auxiliary winding Naux to obtain the current and voltage information in primary side branch road and the secondary side branch road promptly, compare in adopting optical coupling element to obtain the secondary side signal of telecommunication, the primary side modulation mode need not use optical coupling element, and the cost is lower, and has reduced the design degree of difficulty of peripheral feedback loop, and the reliability is higher.
In the above embodiment, as shown in fig. 4, after the first switch Q1 is turned on at time t0, the secondary side current IDWhen the voltage is gradually decreased to zero, an inflection point appears in the waveform of the first sampling voltage Vsense, and the inflection point is a first inflection point of the first sampling voltage Vsense during the turn-on period of the first switching tube Q1 and is defined as a turn-off inflection point B, the calculating module is configured to detect the turn-off inflection point B, and the driving module turns off the second switching tube Q2 at a time t1 when the turn-off inflection point appears. In this embodiment, after the second switch Q2 is turned off, the resonant capacitor Cr is reversely discharged to zero and then charged in a positive direction, the first sampling voltage Vsense rapidly decreases to a negative value and then gradually increases, and when the resonant capacitor Cr voltage increases to an output voltage, the first sampling voltage Vsense has an inflection point, which is defined as a turn-on inflection point C, so that the calculation module is configured to detect the turn-on inflection point C, and the driving module can turn on the second switch Q2. In this embodiment, the calculation module detects the turn-on inflection point C through a comparator. As shown in fig. 6, the second sampling voltage V 'sense is obtained by delaying the first sampling voltage Vsense through a delay resistor Rs, the delay range of the delay resistor Rs is 1 ns-2 ns, the first sampling voltage Vsense and the second sampling voltage V' sense are input to a comparator during the turn-off period of the second switching tube Q2, the first time the output voltage Vcomp of the comparator jumps from high level to low level is the first intersection point a of the two voltage waveforms during this period, that is, the first sampling voltage Vsense is greater than the second sampling voltage V 'sense before the intersection point a, the output of the comparator is high level, the first sampling voltage Vsense is less than the second sampling voltage V' sense after the intersection point a, the output of the comparator is low level, the intersection point a lags behind the turn-on inflection point C, and the calculating module detects that the output voltage is at the second switching tubeWhen the off period jumps from the high level to the low level for the first time, the driving module turns on the second switch tube Q2 when the intersection point a appears. It should be noted that the second switching tube Q2 is controlled to be turned on at the time of the intersection point a, and the actual time of the intersection point a lags behind the turn-on inflection point, and when the turn-on time of the second switching tube Q2 is greater than the ideal value, the current flows back to the primary side branch, the first switching tube Q1 is damaged, and the second switching tube Q2 is turned on after a period of time delay after the turn-on inflection point C is reached, so that the circuit can be protected.
In an embodiment, as shown in fig. 5, the calculating module further includes a delay circuit and an xor gate, an output of the comparator is connected to a first input terminal of the xor gate on the one hand and an input terminal of the delay circuit on the other hand, an output terminal of the delay circuit is connected to a second input terminal of the xor gate, and the driving module is configured to control the second switch Q2 to be turned on when the output terminal of the xor gate outputs a high level, and keep a state of the second switch Q2 unchanged when the output terminal of the xor gate outputs a low level. In this embodiment, as shown in fig. 6, the comparator output voltage Vcomp is a rectangular pulse, the comparator output voltage Vcomp jumps from a high level to a low level at the intersection point a, the comparator output voltage Vcomp is delayed by the delay circuit to generate a delay pulse Vcomp _ de, the delay pulse Vcomp _ de and the comparator output voltage Vcomp generate a voltage dutySR 'through an exclusive or logic operation, when the delay pulse Vcomp _ de is opposite to the comparator output voltage Vcomp level, the xor gate output voltage dutySR' is a high level, and the rest is a low level, so that the xor gate output voltage dutySR 'is a high level, when the xor gate output voltage dutySR' is a high level, the second switch Q2 can be controlled to be turned on, and when the xor gate output is a low level, the state of the second switch Q2 is maintained.
In an embodiment, the main circuit further includes a third sampling resistor Rsense, the primary winding Np is sequentially connected in series with the first switching tube Q1 and the third sampling resistor Rsense and then grounded, one end of the third sampling resistor Rsense connected with the first switching tube Q1 serves as a third sampling point, and the control circuit uses the control circuit to control the on and off of the first switching tube Q1 according to the current and voltage information of the primary branchWhen the third sampling voltage Vp sampled at the third sampling point reaches an even number of zero points, the first switch Q1 is controlled to be turned on, and when the third sampling voltage Vp reaches an even number of zero points, the first switch Q1 is controlled to be turned off during the period that the first switch Q1 is turned on. The third sampling voltage Vp is positively correlated with the primary current Ip, VP＝Rsense*IPWhen the third sampling voltage Vp is at the even-numbered zero point, that is, the primary current Ip is at the even-numbered zero point, the potential between the input end and the output end of the first switching tube Q1 is at the valley bottom, and at this time, the first switching tube Q1 is turned on, so that zero voltage conduction is realized; during the on period of the first switching tube Q1, when the third sampling voltage Vp is at even numbers of zero points, that is, when the primary current Ip is at even numbers of zero points, the first switching tube Q1 is controlled to be turned off, so that zero current turn-off is realized, and therefore, the switching loss of the first switching tube Q1 is reduced.
In an embodiment, the first switch Q1 and the second switch Q2 are Metal-Oxide-Semiconductor Field-Effect transistors (MOS transistors), and the first switch Q1 and the second switch Q2 are NMOS transistors. The working process of the switching power supply circuit in the present application is described below by taking the first switching transistor Q1 as a first NMOS transistor and the second switching transistor Q2 as a second NMOS transistor as an example, where a potential between an input end and an output end of the first switching transistor Q1 is a source-drain voltage V of the first NMOS transistords. As shown in fig. 4, in one control cycle, the operation process is divided into the following four time phases:
time period t 0-t 1: at the time t0, the primary current Ip passes through the even numbered zero points, and the source-drain voltage V of the first NMOS tubedsAt the valley bottom, at this time, the first control signal duty is at a high level, the first switching tube Q1 is controlled to be switched on, the primary side current Ip is linearly increased, and the secondary side current IDLinearly decreasing, at time t1, secondary side current IDWhen the voltage drops to zero, the first sampling voltage Vsense generates a turn-off inflection point B, and at the moment, the second control signal dutySR jumps to high level to control the second switching tube Q2 to be turned off, so that zero current turn-off is realized;
time period t 1-t 2: at the time t1, the second switching tube Q2 is turned off, the resonant capacitor Cr, the resonant inductor Lres and the leakage inductance of the transformer Lp resonate, the energy of the primary winding Np is transferred to the secondary winding Ns, and the resonant capacitor Cr is charged in the positive direction after being discharged in the reverse direction, so that the third sampling voltage Vp is rapidly reduced to the negative value and then gradually increased. The primary side current Ip gradually rises and then resonates to a negative value, and when the primary side current Ip reaches an even number of zero points, the first control signal duty jumps to a low level to control the first switching tube Q1 to be switched off. In this embodiment, the device is turned on in the first switching tube Q1, and when the primary current Ip reaches the second zero point, the first switching tube Q1 is controlled to be turned off, so as to implement zero current turn-off. Turning off a first switching tube Q1 at a second even number of primary side current Ip zero points, so that the primary side branch circuit performs switching action after an integer number of resonance cycles;
time period t 2-t 3: at the time t2, the first switch tube Q1 is turned off, the resonant capacitor Cr, the resonant inductor Lres, the leakage inductor of the transformer Lp and the source-drain output capacitor of the first switch tube Q1 resonate, the resonant capacitor Cr is charged in the forward direction, and the output voltage V is reached at the time t3OAt this time, the source-drain voltage of the second switch tube Q2 is zero, the conducting inflection point C appears on the first sampling voltage Vsense, the second control signal dutySR jumps to high level, and the second switch tube Q2 is controlled to be conducted, so that zero-voltage conduction is realized;
time period t 3-t 4: at the time t3, the second switching tube Q2 is turned on, the primary side branch generates resonance, that is, the resonant inductor Lres, the leakage inductance of the transformer Lp and the source-drain output capacitance of the first switching tube Q1 form a resonant circuit, the primary side current Ip is a resonant current, during the turn-on period of the first switching tube Q1, when the primary side current Ip is at the even number zero point, the source-drain voltage of the first switching tube Q1 is just at the valley bottom, at this time, the first control signal duty is changed to be at a high level, the first switching tube Q1 is controlled to be turned on, and the zero voltage turn-on is realized. This completes one cycle of control, wherein the on-time and off-time of the first switch Q1 are determined according to specific situations.
It should be noted that during the time period from t3 to t4, during the conduction period of the second switching tube Q2, due to the parasitic inductance existing in the circuit, the parasitic circuit includes the leakage inductance of the transformer Lp and the parasitic inductance of the conducting wire, and in the secondary side branch, the parasitic inductance existsThe primary inductor and the resonant capacitor Cr form a resonant circuit as shown in FIG. 7, and the resonant capacitor Cr has a voltage
That is, the voltage of the resonant capacitor Cr at this stage fluctuates due to resonance, so that the first sampling voltage Vsense fluctuates in this period.
The above examples only show some embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A switching power supply circuit, comprising:
the main circuit comprises a transformer, a resonant capacitor, a first switching tube and a second switching tube, wherein the transformer comprises a primary winding and a secondary winding, the primary winding is connected with the input end and the output end of the first switching tube in series to form a primary branch, the primary branch is used for being connected with an input power supply, the secondary winding is connected with the input end and the output end of the second switching tube in series to form a secondary branch, the resonant capacitor is connected between the second switching tube and the secondary winding and connected with the secondary winding in parallel, and the secondary branch is used for being connected with a load; and
the control circuit controls the connection and disconnection of the first switching tube and the second switching tube, wherein when the first switching tube is connected and the current flowing from the input end of the second switching tube to the output end of the second switching tube is reduced to zero, the second switching tube is controlled to be disconnected; and when the first switching tube is switched off and the resonant capacitor is charged, the second switching tube is controlled to be switched on.
2. The switching power supply circuit according to claim 1, wherein said main circuit further comprises a resonant inductor, said resonant inductor being connected in series in said primary side branch.
3. The switching power supply circuit according to claim 2,
in the primary side branch, the input end of the resonant inductor is used for being connected with an input power supply, the output end of the resonant inductor is connected with the first end of the primary side winding, the second end of the primary side winding is connected with the input end of the first switching tube, and the output end of the first switching tube is grounded;
in the secondary branch, a third end of the secondary winding is connected with an input end of the second switching tube, a fourth end of the secondary winding and an output end of the second switching tube are used for connecting a load, the resonant capacitor is connected with the secondary winding in parallel, one end of the resonant capacitor is connected with the input end of the second switching tube, and the second end and the third end are homonymous ends.
4. The switching power supply circuit according to claim 3, wherein the main circuit further comprises an input filter capacitor and an output filter capacitor, the input filter capacitor is connected between the input end of the resonant inductor and the ground, and the output filter capacitor is connected between the output end of the second switching tube and the fourth end of the secondary winding.
5. The switching power supply circuit according to claim 1, wherein said control circuit is configured to control said second switching tube to conduct when a potential between said input terminal of said second switching tube and said output terminal of said second switching tube decreases to zero during charging of said resonant capacitor.
6. The switching power supply circuit according to claim 5, wherein the control circuit is configured to control the first switching tube to be turned on when a potential between the input terminal and the output terminal of the first switching tube is at a valley, and to control the first switching tube to be turned off when a current flowing through the first switching tube is zero.
7. The switching power supply circuit according to claim 6,
the transformer further comprises a primary side auxiliary winding, the main circuit further comprises a first sampling resistor, a second sampling resistor and a delay resistor, the first sampling resistor and the second sampling resistor are connected in series between a fifth end and a sixth end of the primary side auxiliary winding, the sixth end of the primary side auxiliary winding is grounded, one end of the first sampling resistor, which is connected with the second sampling resistor, is used as a first sampling point, one end of the delay resistor is connected with the first sampling point, the other end of the delay resistor is used as a second sampling point, and the fifth end of the primary side auxiliary winding and the third end of the secondary side winding are homonymous ends;
the control circuit comprises a sampling module, a calculating module and a driving module, wherein the sampling module is respectively connected with the first sampling point and the second sampling point to sample a first sampling voltage of the first sampling point and a second sampling voltage of the second sampling point, the calculating module comprises a comparator, the positive input end of the comparator is connected with the first sampling voltage, the negative input end of the comparator is connected with the second sampling voltage, and the driving module is connected with the calculating module and used for controlling the conduction of the second switching tube when the output end of the comparator jumps from a high level to a low level; the calculation module is further used for calculating a first inflection point of the first sampling voltage during the conduction period of the first switching tube, and the driving module is used for controlling the second switching tube to be turned off at the inflection point.
8. The switching power supply circuit according to claim 7, wherein the computing module further comprises a delay circuit and an exclusive or gate, the output terminal of the comparator is connected to the first input terminal of the exclusive or gate, the output terminal of the delay circuit is connected to the second input terminal of the exclusive or gate, and the driving module is configured to control the second switch to be turned on when the output terminal of the exclusive or gate outputs a high level, and to keep the state of the second switch unchanged when the output terminal of the exclusive or gate outputs a low level.
9. The switching power supply circuit according to claim 7, wherein the second sampling voltage is delayed from the first sampling voltage by 1ns to 2 ns.
10. The switching power supply circuit according to claim 6, wherein the main circuit further includes a third sampling resistor, the primary winding is connected in series with the first switching tube and the third sampling resistor in sequence and then grounded, one end of the third sampling resistor connected to the first switching tube is used as a third sampling point, the control circuit is configured to sample a third sampling voltage at the third sampling point, and is configured to control the first switching tube to be turned on when the third sampling voltage reaches an even number of zero points, and to control the first switching tube to be turned off when the third sampling voltage reaches an even number of zero points during the turn-on period of the first switching tube.
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| CN113659837A (en) * | 2021-07-05 | 2021-11-16 | 华为技术有限公司 | Converter, converter control method and power adapter |
| CN113708640A (en) * | 2021-08-25 | 2021-11-26 | 深圳中科乐普医疗技术有限公司 | Active clamping flyback converter, control method thereof and switching power supply system |
| CN117498510A (en) * | 2024-01-03 | 2024-02-02 | 唐泽制动器(天津)有限公司 | Constant voltage charging circuit of electric vehicle battery |
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| CN107147298A (en) * | 2017-05-31 | 2017-09-08 | 青岛大学 | A kind of microwave oven magnetic supply unit with pull-up active clamp branch road |
| CN108539986A (en) * | 2017-12-15 | 2018-09-14 | 杰华特微电子（杭州）有限公司 | A kind of inverse-excitation type switch power-supply |
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| CN102386779A (en) * | 2011-12-06 | 2012-03-21 | 上海新进半导体制造有限公司 | Switching power supply |
| CN107147298A (en) * | 2017-05-31 | 2017-09-08 | 青岛大学 | A kind of microwave oven magnetic supply unit with pull-up active clamp branch road |
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| CN113659837A (en) * | 2021-07-05 | 2021-11-16 | 华为技术有限公司 | Converter, converter control method and power adapter |
| CN113659837B (en) * | 2021-07-05 | 2023-08-04 | 华为数字能源技术有限公司 | Converter, converter control method and power adapter |
| CN113708640A (en) * | 2021-08-25 | 2021-11-26 | 深圳中科乐普医疗技术有限公司 | Active clamping flyback converter, control method thereof and switching power supply system |
| CN113708640B (en) * | 2021-08-25 | 2023-01-20 | 深圳中科乐普医疗技术有限公司 | Active clamping flyback converter, control method thereof and switching power supply system |
| CN117498510A (en) * | 2024-01-03 | 2024-02-02 | 唐泽制动器(天津)有限公司 | Constant voltage charging circuit of electric vehicle battery |
| CN117498510B (en) * | 2024-01-03 | 2024-03-05 | 唐泽制动器(天津)有限公司 | Constant voltage charging circuit of electric vehicle battery |
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