CN110011537B - Switch converter and control method thereof - Google Patents
Switch converter and control method thereof Download PDFInfo
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- CN110011537B CN110011537B CN201910381972.2A CN201910381972A CN110011537B CN 110011537 B CN110011537 B CN 110011537B CN 201910381972 A CN201910381972 A CN 201910381972A CN 110011537 B CN110011537 B CN 110011537B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of DC power input into DC power output
- H02M3/02—Conversion of DC power input into DC power output without intermediate conversion into AC
- H02M3/04—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters
- H02M3/10—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
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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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Power Engineering (AREA)
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Abstract
The invention discloses a switching converter and a control method thereof, wherein the switching converter comprises an input power supply positive electrode, an output voltage positive electrode, a power supply common ground, a switching tube Q1, a switching tube Q2, a switching tube Q3, a switching tube Q4, an inductor L1 and a capacitor C1; the drain electrode of the switching tube Q1 and the drain electrode of the switching tube Q3 are connected to the positive input power supply, the source electrode of the switching tube Q1 and the drain electrode of the switching tube Q2 are connected to one end of the inductor L1, the source electrode of the switching tube Q3 and the drain electrode of the switching tube Q4 are connected to the other end of the inductor L1, the source electrode of the switching tube Q4 is connected to one end of the capacitor C1, and the source electrode of the switching tube Q2 and the other end of the capacitor C1 are connected to the common ground of the power supply.
Description
Technical Field
The present invention relates to switching power supplies, and more particularly, to a switching converter circuit and a control method thereof.
Background
Fig. 1 shows a conventional voltage reduction circuit, which has a large effective current value when the circuit operates in an intermittent mode, a MOS transistor Q1 is a hard switch, and the diode D1 has a large conduction loss.
Fig. 2 is a voltage-reducing circuit with a synchronous rectification function, which reduces the conduction loss at the freewheeling stage compared with the conventional voltage-reducing circuit, and can also realize ZVS switching of a MOS transistor Q1 in the FCCM mode, because the ZVS switching and high-efficiency working ranges of the MOS transistor Q1 are relatively narrow, the problem of relatively low comprehensive efficiency exists in the full-load range in the wide voltage input range.
Fig. 3 is a drawing of the abstract of the united states patent with the application number of 13/794,588, entitled "apparatus METHODS FOR controlling currents in control currents MODE POWER CONVERTERS", and the core idea of the patent is that a unidirectional switch is connected in parallel at two ends of an inductor to clamp the reverse current of the inductor, so that ZVS turning-on of a main MOS transistor Q1 is realized under a large input voltage range and a large load range. However, the patent does not solve the problems that the effective value of current is large and the conduction loss is large when the voltage reduction circuit works in an intermittent mode; in addition, when the ratio of the discontinuous mode to the input-output voltage is greater than 3, the ton time of the MOS transistor Q1 is too small, the free-wheeling time of the MOS transistor Q2 is too long and high in frequency, and the high current output and high-efficiency operation are difficult to realize compromise.
Disclosure of Invention
In view of the technical defects of the existing voltage reduction circuit, the improved patent circuit and the control mode thereof, the invention provides a switch converter and the control mode thereof, and solves the problems that the effective value of current is large and the conduction loss is large when the voltage reduction circuit works in an intermittent mode. And the problems that when the ratio of the input voltage to the output voltage is larger than 3, the ton time of the MOS transistor Q1 is too small, the follow current time of the MOS transistor Q2 is too long, high frequency is difficult to realize, and the high current output and high-efficiency operation are in compromise are solved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a switching converter comprises an input power supply positive electrode, an output voltage positive electrode, a power supply common ground, a switching tube Q1, a switching tube Q2, a switching tube Q3, a switching tube Q4, an inductor L1 and a capacitor C1; the drain of the switching tube Q1 and the drain of the switching tube Q3 are connected to the positive input power supply, the source of the switching tube Q1 and the drain of the switching tube Q2 are connected to one end of an inductor L1, the source of the switching tube Q3 and the drain of the switching tube Q4 are connected to the other end of the inductor L1, the source of the switching tube Q4 is connected to one end of a capacitor C1, and the source of the switching tube Q2 and the other end of the capacitor C1 are connected to the power supply common ground.
Preferably, the ratio of the input to output voltages is greater than 3.
Preferably, the switching tube Q1, the switching tube Q2, the switching tube Q3 and the switching tube Q4 are MOS tubes, triodes or IGBTs.
The first control method of the switching converter described above includes the steps of:
stage t 0-t 1: at time t0, switching tube Q4 is turned on, the voltage across inductor L1 is Vin-Vo, inductor L1 is excited, the current IL of inductor L1 rises, and switching tube Q1 is turned off at time t 1;
stage t 1-t 2: after the switching tube Q1 is turned off, the current IL of the inductor L1 charges the output capacitor Coss1 of the switching tube Q1, discharges the output capacitor Coss2 of the switching tube Q2, the voltage at one end of the inductor L1 is reduced from Vin to 0V at the time of t2, and the switching tube Q2 realizes ZVS switching-on;
stage t 2-t 3: the voltage at the two ends of the inductor L1 is Vo, the inductor L1 is demagnetized, the current IL is reduced, and the switching tube Q4 is turned off at the time t 3;
stage t 3-t 4: the current IL of the inductor L1 charges an output capacitor Coss4 of the switching tube Q4, discharges the output capacitor Coss3 of the switching tube Q3, the voltage at the other end of the inductor L1 rises from Vo to Vin at the time of t4, and the switching tube Q3 realizes ZVS on;
stage t 4-t 5: the current IL of the inductor L1 has one phase change, and the switching tube Q2 is turned off at the time t5 from positive to negative;
stage t 5-t 6: the current IL of the inductor L1 charges an output capacitor Coss2 of the switching tube Q2, discharges the output capacitor Coss1 of the switching tube Q1, the voltage at one end of the inductor L1 rises from 0V to Vin at the time of t6, and the switching tube Q1 realizes ZVS switching-on;
stage t 6-t 7: the voltage across the inductor L1 is Vin, and the voltage difference is zero, so the current IL of the inductor L1 remains unchanged, and the switching tube Q3 is turned off at time t 7;
t 7-t 0+ Tx stage: the current IL of the inductor L1 charges an output capacitor Coss3 of the switching tube Q3, discharges the output capacitor Coss4 of the switching tube Q4, the voltage at the other end of the inductor L1 drops to Vo from Vin at the time of t0+ Tx, and the switching tube Q4 realizes ZVS switching-on;
when the period is finished, the next working period is started, and the above steps are repeated;
vin is the input supply voltage, Vo is the output voltage, and Tx is the time duration of the xth period.
As an improvement of the first control method, characterized in that: when the load is reduced to a constant value, the load starts to decrease at the stages t0 to t1, t2 to t3 and t4 to t5, and the load becomes longer at the stages t6 to t 7.
The second control method of the switching converter described above includes the steps of:
stage t 0-t 1: at time t0, switching tube Q1 is turned on, the voltage across inductor L1 is Vin-Vo, inductor L1 is excited, the current IL of inductor L1 rises, and switching tube Q1 is turned off at time t 1;
stage t 1-t 2: after the switching tube Q1 is turned off, the current IL of the inductor L1 charges the output capacitor Coss1 of the switching tube Q1, discharges the output capacitor Coss2 of the switching tube Q2, the voltage at one end of the inductor L1 is reduced from Vin to 0V at the time of t2, and the switching tube Q2 realizes ZVS switching-on;
stage t 2-t 3: the voltage at the two ends of the inductor L1 is Vo, the inductor L1 is demagnetized, the current IL is reduced, and the switching tube Q4 is turned off at the time t 3;
stage t 3-t 4: the current IL of the inductor L1 charges an output capacitor Coss4 of the switching tube Q4, discharges the output capacitor Coss3 of the switching tube Q3, the voltage at the other end of the inductor L1 rises from Vo to Vin at the time of t4, and the switching tube Q3 realizes ZVS on;
stage t 4-t 5: the current IL of the inductor L1 drops to zero at time t5, at which time the switching tube Q3 is turned off;
stage t 5-t 6: an output capacitor Coss3 of a switch tube Q3 is charged, an output capacitor Coss4 of a switch tube Q4 is discharged, the current IL of an inductor L1 is reduced from zero to negative current, the voltage at the other end of the inductor L1 is reduced from Vin to Vo at the time of t6, and ZVS (zero voltage switching on) is realized by the switch tube Q4;
stage t 6-t 7: the voltage at the two ends of the inductor L1 is Vo, the Vo reversely excites the inductor L1, and the switching tube Q2 is turned off at the time t 7;
t 7-t 0+ Tx stage: the current of the inductor L1 discharges the output capacitor Coss1 of the switching tube Q1, the output capacitor Coss2 of the switching tube Q2 is charged, the voltage of one end of the inductor L1 rises to Vin from zero at the time of t0+ Tx, and the switching tube Q1 realizes ZVS switching-on;
when the period is finished, the next working period is started, and the above steps are repeated;
vin is the input supply voltage, Vo is the output voltage, and Tx is the time duration of the xth period.
As an improvement of the second control method, characterized in that: when the load is reduced to a constant value, the load starts to decrease at the stages t0 to t1, t2 to t3 and t4 to t5, and the load becomes longer at the stages t6 to t 7.
The invention also provides another switch converter with the same inventive concept, and the technical scheme is as follows:
a switching converter comprises an input power supply positive electrode, an output voltage positive electrode, a power supply common ground, a switching tube Q1, a switching tube Q2, a switching tube Q4, a diode D1, an inductor L1 and a capacitor C1; the drain of the switch tube Q1 and the cathode of the diode D1 are connected to the positive input power supply, the source of the switch tube Q1 and the drain of the switch tube Q2 are connected to one end of the inductor L1, the anode of the diode D1 and the drain of the switch tube Q4 are connected to the other end of the inductor L1, the source of the switch tube Q4 is connected to one end of the capacitor C1, and the source of the switch tube Q2 and the other end of the capacitor C1 are connected to the power supply common ground.
Preferably, the ratio of the input to output voltages is greater than 3.
Preferably, the switching tube Q1, the switching tube Q2 and the switching tube Q4 are MOS tubes, triodes or IGBTs.
The control method of the switching converter comprises the following steps:
stage t 0-t 1: at time t0, switching tube Q1 is turned on, the voltage across inductor L1 is Vin-Vo, inductor L1 is excited, the current IL of inductor L1 rises, and switching tube Q1 is turned off at time t 1;
stage t 1-t 2: after the switching tube Q1 is turned off, the current IL of the inductor L1 charges the output capacitor Coss1 of the switching tube Q1, discharges the output capacitor Coss2 of the switching tube Q2, the voltage at one end of the inductor L1 is reduced from Vin to 0V at the time of t2, and the switching tube Q2 realizes ZVS switching-on;
stage t 2-t 3: the voltage at the two ends of the inductor L1 is Vo, the inductor L1 is demagnetized, the current IL is reduced, and the switching tube Q4 is turned off at the time t 3;
stage t 3-t 4: the current IL of the inductor L1 charges an output capacitor Coss4 of the switching tube Q4, the voltage at the other end of the inductor L1 rises from Vo to Vin, the voltage at the two ends of the inductor L1 is clamped by Vin, when the current IL drops to zero, the current IL is reversed, the output capacitor Coss4 of the switching tube Q4 starts to discharge, the voltage at the other end of the inductor L1 drops from Vin to Vo at the time of t4, and the switching tube Q4 realizes ZVS on;
stage t 4-t 5: the voltage at the two ends of the inductor L1 is Vo, the Vo reversely excites the inductor L1, and the switching tube Q2 is turned off at the time t 5;
t 5-t 0+ Tx stage: the current IL of the inductor L1 charges the output capacitor Coss2 of the switching tube Q2, discharges the output capacitor Coss1 of the switching tube Q1, the voltage at one end of the inductor L1 rises from 0V to Vin at the time t6, and the switching tube Q1 realizes ZVS switching-on at the time t0+ Tx;
when the period is finished, the next working period is started, and the above steps are repeated;
vin is the input supply voltage, Vo is the output voltage, and Tx is the time duration of the xth period.
As an improvement of the above control method, characterized in that: when the load is reduced to a constant value, the load starts to decrease at the stages t0 to t1, t2 to t3 and t4 to t5, and the load becomes longer at the stages t6 to t 7.
Description of the meaning of the terms:
drain electrode of the switching tube: for the MOS tube, a drain electrode is referred, for the triode, a collector electrode is referred, for the IGBT, a drain electrode is referred, and other switching tubes can correspond to each other according to the knowledge of a person skilled in the art and are not listed one by one;
source electrode of the switching tube: for the MOS transistor, the source electrode, the emitter electrode, and the source electrode, the other switching transistors may correspond to each other according to the knowledge of those skilled in the art, and are not listed.
Compared with the prior art, the invention has the following beneficial effects:
1) the circuit works in an intermittent mode, and ZVS (zero voltage switching) of all MOS (metal oxide semiconductor) tubes is realized;
2) the waveform of the inductive current is changed from a triangle to a quadrangle, the effective value of the inductive current is reduced under the same output power, the conduction loss is reduced, the efficiency is improved, and the large current output is easy to realize;
3) when the ratio of the input voltage to the output voltage is large, the turn-off of the MOS transistor Q4 greatly shortens the follow current time of the MOS transistor Q2, high frequency is achieved, and the inductance value and the capacitance value of the capacitor are reduced due to the high frequency, so that the size of a power supply is reduced, and the cost is reduced.
Drawings
FIG. 1 is a schematic diagram of a conventional voltage step-down circuit;
FIG. 2 is a schematic diagram of a voltage step-down circuit with synchronous rectification;
FIG. 3 is a schematic diagram of the voltage reduction circuit of patent application No. 13/794,588;
FIG. 4 is a schematic circuit diagram of a first embodiment of the present invention;
FIG. 5 is a graph of input-to-output voltage ratio versus switching frequency;
FIG. 6 is a timing diagram illustrating a first operation of the first embodiment of the present invention;
FIG. 7 is a timing diagram illustrating a second operation of the first embodiment of the present invention;
FIG. 8 is a circuit schematic of a second embodiment of the present invention;
FIG. 9 is a timing diagram illustrating operation of the second embodiment of the present invention.
Detailed Description
First embodiment
Fig. 4 is a schematic circuit diagram of a first embodiment of the present invention. The power supply comprises an input power supply positive Vin, an output voltage positive Vo, a power supply common ground GND, a MOS tube Q1, a MOS tube Q2, a MOS tube Q3, a MOS tube Q4, an inductor L1 and a capacitor C1; the drain of the MOS transistor Q1 and the drain of the MOS transistor Q3 are connected to the input power positive Vin, the source of the MOS transistor Q1 and the drain of the MOS transistor Q2 are connected to one end of the inductor L1, the source of the MOS transistor Q3 and the drain of the MOS transistor Q4 are connected to the other end of the inductor L1, the source of the MOS transistor Q4 is connected to one end of the capacitor C1, and the source of the MOS transistor Q2 and the other end of the capacitor C1 are connected to the power common ground GND.
Coss1, Coss2, Coss3 and Coss4 in fig. 4 are output capacitances of the MOS transistor Q1, the MOS transistor Q2, the MOS transistor Q3 and the MOS transistor Q4, respectively, and fig. 4 also shows body diodes of the MOS transistor Q1, the MOS transistor Q2, the MOS transistor Q3 and the MOS transistor Q4.
It should be noted that: it is common practice for those skilled in the art to replace MOS transistor Q1, MOS transistor Q2, MOS transistor Q3, and MOS transistor Q4 with other types of switching transistors such as transistors and IGBTs.
Fig. 5 shows the waveform of the inductor L1 current IL and the output current Io when the buck circuit is operating in discontinuous mode,
according to the formula
The rising slope of the current IL is
The falling slope of the current IL is
The rise and fall times of the current IL are the same, corresponding to a duty cycle T1.
When in use
When the rising slope of the current IL is
The falling slope of the current IL is
The inductance of inductor L1 is changed to make the rising slope of current IL sum
The rising slope of the current is the same, the falling time of the current IL is
The working period is T2 which is 2 times of the falling time of the time current IL and is larger than T1.
When in use
When the rising slope of the current IL is
The falling slope of the current IL is
The inductance of inductor L1 is changed to make the rising slope of current IL sum
The rising slope of the current is the same, the falling time of the current IL is
The working period is T3 and is larger than T2, which is 4 times of the falling time of the current IL.
Therefore, in the discontinuous mode, the larger the ratio of the input voltage to the output voltage, the larger the corresponding switching period, the smaller the frequency, and the more difficult the realization of high frequency, and when the ratio of the input voltage to the output voltage is selected to be larger than 3, the invention can ensure that the invention obtains better beneficial effects.
Fig. 6 shows a first operation sequence of the first embodiment for a switching converter with Vin voltage of 380V, Vo voltage of 48V, inductor L1 of 1uH and output current of 20A, which is specifically as follows:
stage t 0-t 1: at time t0, MOS tube Q4 is turned on, the voltage across inductor L1 is Vin-Vo, inductor L1 is excited, the current IL of inductor L1 rises, and MOS tube Q1 is turned off at time t 1;
stage t 1-t 2: after the MOS transistor Q1 is turned off, the current IL of the inductor L1 charges the output capacitor Coss1 of the MOS transistor Q1, discharges the output capacitor Coss2 of the MOS transistor Q2, and reduces the voltage of the circuit node SW1 (i.e., one end of the inductor L1) from Vin to 0V at time t2, so that the MOS transistor Q2 realizes ZVS switching on;
stage t 2-t 3: the voltage at the two ends of the inductor L1 is Vo, the inductor L1 is demagnetized, the current IL is reduced, and the MOS transistor Q4 is turned off at the time t 3;
stage t 3-t 4: the current IL of the inductor L1 charges the output capacitor Coss4 of the MOS transistor Q4, discharges the output capacitor Coss3 of the MOS transistor Q3, and increases the voltage of the node SW2 (i.e., the other end of the inductor L1) from Vo to Vin at time t4, so that the MOS transistor Q3 realizes ZVS switching on;
stage t 4-t 5: the current IL of the inductor L1 has one phase change, and the MOS tube Q2 is turned off at the time t5 from positive to negative;
stage t 5-t 6: the current IL of the inductor L1 charges the output capacitor Coss2 of the MOS transistor Q2, discharges the output capacitor Coss1 of the MOS transistor Q1, and increases the voltage of the node SW1 (i.e., one end of the inductor L1) from 0V to Vin at time t6, so that the MOS transistor Q1 realizes ZVS switching on;
stage t 6-t 7: the voltage across the inductor L1 is Vin, and the voltage difference is zero, so the current IL of the inductor L1 remains unchanged, and the MOS transistor Q3 is turned off at time t 7;
t 7-t 0+ Tx stage: the current IL of the inductor L1 charges the output capacitor Coss3 of the MOS transistor Q3, the output capacitor Coss4 of the Q4 discharges, the voltage of the node SW2 (i.e., the other end of the inductor L1) drops from Vin to Vo at time t0+ Tx, and the MOS transistor Q4 realizes ZVS switching on;
the cycle is ended and the next duty cycle is started and the above stages are repeated.
Since the circuit operates periodically, Tx in t0+ Tx means the time length of the xth period.
As shown in fig. 6, the waveform of the current IL of the inductor L1 is quadrilateral, and under the same output power, compared with the triangular waveform in the prior art, the peak value of the inductor current is reduced, and the effective value is reduced, so the conduction loss is reduced, the efficiency is improved, and the formula shows that
Obtaining L & ltdi & gt & ltN & gt dB & ltAe & gt, reducing di by the current peak value, and reducing the effective sectional area Ae of the magnetic core of the inductor under the condition that the inductance L of the inductor, the turn number N of the inductor and the dB of the magnetic core are not changed, so that the size of the magnetic core is reduced; if di is reduced under the same output ripple requirement, the capacitance value of the required filter capacitor is reduced, and the size of the capacitor is reduced; the turn-off of the MOS transistor Q4 greatly shortens the follow current time of the MOS transistor Q2, realizes high frequency, and further reduces the inductance value and the capacitance value of the capacitor due to the high frequency; the size of the power supply is reduced, and the cost is reduced.
Fig. 7 shows a second operation sequence of the first embodiment, which is as follows:
stage t 0-t 1: at time t0, MOS tube Q1 is turned on, the voltage across inductor L1 is Vin-Vo, inductor L1 is excited, the current IL of inductor L1 rises, and MOS tube Q1 is turned off at time t 1;
stage t 1-t 2: after the MOS transistor Q1 is turned off, the current IL of the inductor L1 charges the output capacitor Coss1 of the MOS transistor Q1, discharges the output capacitor Coss2 of the MOS transistor Q2, the voltage of the circuit node SW1 is reduced from Vin to 0V at the time t2, and the MOS transistor Q2 realizes ZVS switching on;
stage t 2-t 3: the voltage at the two ends of the inductor L1 is Vo, the inductor L1 is demagnetized, the current IL is reduced, and the MOS transistor Q4 is turned off at the time t 3;
stage t 3-t 4: the current IL of the inductor L1 charges an output capacitor Coss4 of the MOS transistor Q4, discharges the output capacitor Coss3 of the MOS transistor Q3, the voltage of a node SW2 rises from Vo to Vin at the time t4, and the MOS transistor Q3 realizes ZVS on;
stage t 4-t 5: the current IL of the inductor L1 drops to zero at time t5, at which time the MOS transistor Q3 is turned off;
stage t 5-t 6: an output capacitor Coss3 of the MOS transistor Q3 is charged, an output capacitor Coss4 of the MOS transistor Q4 is discharged, the current IL of the inductor L1 is reduced from zero to negative current, the voltage of a node SW2 is reduced from Vin to Vo at the time t6, and ZVS (zero voltage switching on) is realized by the MOS transistor Q4;
stage t 6-t 7: the voltage at the two ends of the inductor L1 is Vo, the Vo reversely excites the inductor L1, and the MOS tube Q2 is turned off at the time t 7;
t 7-t 0+ Tx stage: the current of the inductor L1 discharges the output capacitor Coss1 of the MOS transistor Q1, charges the output capacitor Coss2 of the MOS transistor Q2, the voltage of a node SW1 rises to Vin from zero at the time of t0+ Tx, and the MOS transistor Q1 realizes ZVS switching-on;
the cycle is ended and the next duty cycle is started and the above stages are repeated.
It can be seen from fig. 7 that the waveform of the current IL of the inductor L1 is also quadrilateral, and the object of the invention is also achieved.
It should be noted that, in addition to the switching converter having a Vin voltage of 380V, a Vo voltage of 48V, an inductor L1 of 1uH, and an output current of 20A, the switching converter having other parameters has a similar operation timing chart, and the waveform of the current IL of the inductor L1 is also a quadrangle, which is different only in amplitude at each time point.
In addition, the two working sequences are both directed at the application scene when the load is fully loaded, in the actual application occasion, the light load often occurs, and at this time, the efficiency of the circuit can be improved by mode switching, and the improvement method is as follows:
1. when the load is reduced to a certain value (namely the output current is reduced to a certain value), the driving of the Q3 is closed, the driving loss is reduced, and the efficiency is improved;
2. when the load is further reduced to a certain value (i.e., when the output current is further reduced to a certain value), the phases t0 to t1, t2 to t3 and t4 to t5 are greatly reduced, and the phases t6 to t7 are greatly lengthened, so that the total switching period is maintained to be almost unchanged. However, the effective current IL time is reduced, so that the effective value of the current IL is larger, the conduction loss is larger, the Q4 is in a continuous conduction state at this time, the driving loss is further reduced, the circuit is changed into a synchronous rectification step-down circuit, the waveform of the current IL of the inductor L1 is changed into a common triangle from a quadrilateral plus a longer t 6-t 7 stage, the effective value of the current is reduced under the same output current, and the efficiency is improved.
Second embodiment
Fig. 8 is a circuit schematic of a second embodiment of the present invention. On the basis of the first embodiment, the MOS transistor Q3 is replaced by a diode D1, a cathode of the diode D1 is connected to a drain of the MOS transistor Q1 and the input power positive Vin, and an anode of the diode D1 is connected to a drain of the MOS transistor Q4 and the other end of the inductor L1.
The time for the diode D1 to flow current is relatively short, compared with the MOS tube scheme, the conduction loss is not increased too much, one-way floating drive is omitted, the drive loss is reduced, the drive circuit is simplified, and the LED driving circuit is suitable for medium and small current output scenes.
The present embodiment has a ratio of input voltage to output voltage greater than 3, and can also obtain a better implementation effect, for a switching converter with Vin voltage of 380V, Vo voltage of 48V, inductor L1 of 1uH, and output current of 20A, fig. 9 shows the operation timing sequence of the second embodiment, which is as follows:
stage t 0-t 1: at time t0, MOS tube Q1 is turned on, the voltage across inductor L1 is Vin-Vo, inductor L1 is excited, the current IL of inductor L1 rises, and MOS tube Q1 is turned off at time t 1;
stage t 1-t 2: after the MOS transistor Q1 is turned off, the current IL of the inductor L1 charges the output capacitor Coss1 of the MOS transistor Q1, discharges the output capacitor Coss2 of the MOS transistor Q2, the voltage of the circuit node SW1 is reduced from Vin to 0V at the time t2, and the MOS transistor Q2 realizes ZVS switching on;
stage t 2-t 3: the voltage at the two ends of the inductor L1 is Vo, the inductor L1 is demagnetized, the current IL is reduced, and the MOS transistor Q4 is turned off at the time t 3;
stage t 3-t 4: the current IL of the inductor L1 charges an output capacitor Coss4 of the MOS transistor Q4, the voltage of a node SW2 rises from Vo to Vin, the voltage at two ends of the inductor L1 is clamped by Vin, when the current IL drops to zero, the current IL is reversed, the output capacitor Coss4 of the MOS transistor Q4 starts to discharge, the voltage of the node SW2 drops from Vin to Vo at the time of t4, and the ZVS is turned on by the MOS transistor Q4;
stage t 4-t 5: the voltage at the two ends of the inductor L1 is Vo, the Vo reversely excites the inductor L1, and the MOS tube Q2 is turned off at the time t 5;
t 5-t 0+ Tx stage: the current IL of the inductor L1 charges the output capacitor Coss2 of the MOS transistor Q2, discharges the output capacitor Coss1 of the MOS transistor Q1, the voltage of the node SW1 rises from 0V to Vin at the time t6, and the MOS transistor Q1 realizes ZVS switching at the time t0+ Tx;
the cycle is ended and the next duty cycle is started and the above stages are repeated.
As can be seen from fig. 9, the waveform of the current IL of the inductor L1 is also quadrilateral, and the object of the invention is also achieved.
In this embodiment, switching converters with other parameters may also be selected, and the efficiency of the circuit may also be improved by the mode switching, which is not described herein.
The above embodiments should not be construed as limiting the present invention, and the scope of the present invention should be determined by the scope of the appended claims. It will be apparent to those skilled in the art that many equivalent substitutions, modifications and alterations can be made without departing from the spirit and scope of the invention, such as fine tuning of the circuit by simple series-parallel connection of devices, etc., depending on the application, and such modifications and alterations should also be considered as the scope of the invention.
Claims (12)
1. A switching converter, characterized by: the power supply comprises an input power supply positive electrode, an output voltage positive electrode, a power supply common ground, a switching tube Q1, a switching tube Q2, a switching tube Q3, a switching tube Q4, an inductor L1 and a capacitor C1; the drain of the switching tube Q1 and the drain of the switching tube Q3 are connected to the positive input power supply, the source of the switching tube Q1 and the drain of the switching tube Q2 are connected to one end of an inductor L1, the source of the switching tube Q3 and the drain of the switching tube Q4 are connected to the other end of the inductor L1, the source of the switching tube Q4 is connected to one end of a capacitor C1, and the source of the switching tube Q2 and the other end of the capacitor C1 are connected to the power supply common ground.
2. The switching converter according to claim 1, wherein: the ratio of the input voltage to the output voltage is greater than 3.
3. The switching converter according to claim 1, wherein: the switching tube Q1, the switching tube Q2, the switching tube Q3 and the switching tube Q4 are MOS tubes, triodes or IGBTs.
4. A control method of a switching converter according to any one of claims 1 to 3, characterized by comprising the steps of:
stage t 0-t 1: at time t0, switching tube Q4 is turned on, the voltage across inductor L1 is Vin-Vo, inductor L1 is excited, the current IL of inductor L1 rises, and switching tube Q1 is turned off at time t 1;
stage t 1-t 2: after the switching tube Q1 is turned off, the current IL of the inductor L1 charges the output capacitor Coss1 of the switching tube Q1, discharges the output capacitor Coss2 of the switching tube Q2, the voltage at one end of the inductor L1 is reduced from Vin to 0V at the time of t2, and the switching tube Q2 realizes ZVS switching-on;
stage t 2-t 3: the voltage at the two ends of the inductor L1 is Vo, the inductor L1 is demagnetized, the current IL is reduced, and the switching tube Q4 is turned off at the time t 3;
stage t 3-t 4: the current IL of the inductor L1 charges an output capacitor Coss4 of the switching tube Q4, discharges the output capacitor Coss3 of the switching tube Q3, the voltage at the other end of the inductor L1 rises from Vo to Vin at the time of t4, and the switching tube Q3 realizes ZVS on;
stage t 4-t 5: the current IL of the inductor L1 has one phase change, and the switching tube Q2 is turned off at the time t5 from positive to negative;
stage t 5-t 6: the current IL of the inductor L1 charges an output capacitor Coss2 of the switching tube Q2, discharges the output capacitor Coss1 of the switching tube Q1, the voltage at one end of the inductor L1 rises from 0V to Vin at the time of t6, and the switching tube Q1 realizes ZVS switching-on;
stage t 6-t 7: the voltage across the inductor L1 is Vin, and the voltage difference is zero, so the current IL of the inductor L1 remains unchanged, and the switching tube Q3 is turned off at time t 7;
t 7-t 0+ Tx stage: the current IL of the inductor L1 charges an output capacitor Coss3 of the switching tube Q3, discharges the output capacitor Coss4 of the switching tube Q4, the voltage at the other end of the inductor L1 drops to Vo from Vin at the time of t0+ Tx, and the switching tube Q4 realizes ZVS switching-on;
when the period is finished, the next working period is started, and the above steps are repeated;
vin is the input supply voltage, Vo is the output voltage, and Tx is the time duration of the xth period.
5. The control method according to claim 4, characterized in that: when the load is reduced to a constant value, the load starts to decrease at the stages t0 to t1, t2 to t3 and t4 to t5, and the load becomes longer at the stages t6 to t 7.
6. A control method of a switching converter according to any one of claims 1 to 3, characterized by comprising the steps of:
stage t 0-t 1: at time t0, switching tube Q1 is turned on, the voltage across inductor L1 is Vin-Vo, inductor L1 is excited, the current IL of inductor L1 rises, and switching tube Q1 is turned off at time t 1;
stage t 1-t 2: after the switching tube Q1 is turned off, the current IL of the inductor L1 charges the output capacitor Coss1 of the switching tube Q1, discharges the output capacitor Coss2 of the switching tube Q2, the voltage at one end of the inductor L1 is reduced from Vin to 0V at the time of t2, and the switching tube Q2 realizes ZVS switching-on;
stage t 2-t 3: the voltage at the two ends of the inductor L1 is Vo, the inductor L1 is demagnetized, the current IL is reduced, and the switching tube Q4 is turned off at the time t 3;
stage t 3-t 4: the current IL of the inductor L1 charges an output capacitor Coss4 of the switching tube Q4, discharges the output capacitor Coss3 of the switching tube Q3, the voltage at the other end of the inductor L1 rises from Vo to Vin at the time of t4, and the switching tube Q3 realizes ZVS on;
stage t 4-t 5: the current IL of the inductor L1 drops to zero at time t5, at which time the switching tube Q3 is turned off;
stage t 5-t 6: an output capacitor Coss3 of a switch tube Q3 is charged, an output capacitor Coss4 of a switch tube Q4 is discharged, the current IL of an inductor L1 is reduced from zero to negative current, the voltage at the other end of the inductor L1 is reduced from Vin to Vo at the time of t6, and ZVS (zero voltage switching on) is realized by the switch tube Q4;
stage t 6-t 7: the voltage at the two ends of the inductor L1 is Vo, the Vo reversely excites the inductor L1, and the switching tube Q2 is turned off at the time t 7;
t 7-t 0+ Tx stage: the current of the inductor L1 discharges the output capacitor Coss1 of the switching tube Q1, the output capacitor Coss2 of the switching tube Q2 is charged, the voltage of one end of the inductor L1 rises to Vin from zero at the time of t0+ Tx, and the switching tube Q1 realizes ZVS switching-on;
when the period is finished, the next working period is started, and the above steps are repeated;
vin is the input supply voltage, Vo is the output voltage, and Tx is the time duration of the xth period.
7. The control method according to claim 6, characterized in that: when the load is reduced to a constant value, the load starts to decrease at the stages t0 to t1, t2 to t3 and t4 to t5, and the load becomes longer at the stages t6 to t 7.
8. A switching converter, characterized by: the power supply comprises an input power supply positive electrode, an output voltage positive electrode, a power supply common ground, a switching tube Q1, a switching tube Q2, a switching tube Q4, a diode D1, an inductor L1 and a capacitor C1; the drain of the switch tube Q1 and the cathode of the diode D1 are connected to the positive input power supply, the source of the switch tube Q1 and the drain of the switch tube Q2 are connected to one end of the inductor L1, the anode of the diode D1 and the drain of the switch tube Q4 are connected to the other end of the inductor L1, the source of the switch tube Q4 is connected to one end of the capacitor C1, and the source of the switch tube Q2 and the other end of the capacitor C1 are connected to the power supply common ground.
9. The switching converter according to claim 8, wherein: the ratio of the input voltage to the output voltage is greater than 3.
10. The switching converter according to claim 8, wherein: the switching tube Q1, the switching tube Q2 and the switching tube Q4 are MOS tubes, triodes or IGBTs.
11. The control method of the switching converter according to any one of claims 8 to 10, characterized by comprising the steps of:
stage t 0-t 1: at time t0, switching tube Q1 is turned on, the voltage across inductor L1 is Vin-Vo, inductor L1 is excited, the current IL of inductor L1 rises, and switching tube Q1 is turned off at time t 1;
stage t 1-t 2: after the switching tube Q1 is turned off, the current IL of the inductor L1 charges the output capacitor Coss1 of the switching tube Q1, discharges the output capacitor Coss2 of the switching tube Q2, the voltage at one end of the inductor L1 is reduced from Vin to 0V at the time of t2, and the switching tube Q2 realizes ZVS switching-on;
stage t 2-t 3: the voltage at the two ends of the inductor L1 is Vo, the inductor L1 is demagnetized, the current IL is reduced, and the switching tube Q4 is turned off at the time t 3;
stage t 3-t 4: the current IL of the inductor L1 charges an output capacitor Coss4 of the switching tube Q4, the voltage at the other end of the inductor L1 rises from Vo to Vin, the voltage at the two ends of the inductor L1 is clamped by Vin, when the current IL drops to zero, the current IL is reversed, the output capacitor Coss4 of the switching tube Q4 starts to discharge, the voltage at the other end of the inductor L1 drops from Vin to Vo at the time of t4, and the switching tube Q4 realizes ZVS on;
stage t 4-t 5: the voltage at the two ends of the inductor L1 is Vo, the Vo reversely excites the inductor L1, and the switching tube Q2 is turned off at the time t 5;
t 5-t 0+ Tx stage: the current IL of the inductor L1 charges the output capacitor Coss2 of the switching tube Q2, discharges the output capacitor Coss1 of the switching tube Q1, the voltage at one end of the inductor L1 rises from 0V to Vin at the time t6, and the switching tube Q1 realizes ZVS switching-on at the time t0+ Tx;
when the period is finished, the next working period is started, and the above steps are repeated;
vin is the input supply voltage, Vo is the output voltage, and Tx is the time duration of the xth period.
12. The control method according to claim 11, characterized in that: when the load is reduced to a constant value, the load starts to decrease at the stages t0 to t1, t2 to t3 and t4 to t5, and the load becomes longer at the stages t6 to t 7.
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| PCT/CN2019/113677 WO2020224200A1 (en) | 2019-05-09 | 2019-10-28 | Switching converter and control method therefor |
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| CN110086342B (en) * | 2019-05-23 | 2020-11-06 | 广州金升阳科技有限公司 | Switch converter and control method thereof |
| CN110504835B (en) * | 2019-08-26 | 2021-09-14 | 广州金升阳科技有限公司 | Switch converter and control method thereof |
| CN110474534B (en) * | 2019-09-05 | 2024-05-07 | 深圳市依崇微电子科技有限公司 | Improved non-isolated voltage converter |
| CN110719026A (en) * | 2019-09-11 | 2020-01-21 | 广州金升阳科技有限公司 | Boost converter and control method thereof |
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