CN108696105B - Switching power supply control circuit and switching power supply - Google Patents
Switching power supply control circuit and switching power supply Download PDFInfo
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- CN108696105B CN108696105B CN201810742941.0A CN201810742941A CN108696105B CN 108696105 B CN108696105 B CN 108696105B CN 201810742941 A CN201810742941 A CN 201810742941A CN 108696105 B CN108696105 B CN 108696105B
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- 239000003990 capacitor Substances 0.000 claims description 65
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- 230000001939 inductive effect Effects 0.000 abstract description 10
- 238000010586 diagram Methods 0.000 description 15
- 238000000034 method Methods 0.000 description 5
- 230000003111 delayed effect Effects 0.000 description 4
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Classifications
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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
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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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
- H02M1/0003—Details of control, feedback or regulation circuits
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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 discloses a switching power supply control circuit and a switching power supply, comprising an error amplifier, wherein a first input end of the error amplifier receives a feedback signal representing the output voltage of the switching power supply, a second input end of the error amplifier receives a reference signal, and the error amplifier outputs a compensation signal; the switching power supply control circuit further comprises a slope compensation circuit, and the slope compensation circuit outputs a slope signal until the switching-off time of the switching tube at a certain time in the switching tube conduction period of the switching power supply; the compensation signal and the slope signal are subjected to difference to obtain a first signal, the first signal is compared with a current sampling signal representing the inductance current to obtain a control signal, and the control signal is used for controlling the on or off of a main power tube of the switching power supply. The invention improves the variation range of the peak value of the inductive current by adjusting the starting point of the ramp signal.
Description
Technical Field
The present disclosure relates to power electronics, and particularly to a switching power supply control circuit and a switching power supply.
Background
The control circuit of the prior art switching power supply generally adds a ramp signal to increase the stability of the circuit. As shown in fig. 1, the switching power supply control circuit of the prior art includes an error amplifier having one end receiving a sampling signal V of an output voltage FB The other end receives a reference signal Vref, the error amplifier outputs a compensation signal Vc, the compensation signal Vc and the ramp signal Vr are input into a first input end of a comparator after being subjected to difference, a second input end of the comparator receives a current sampling signal Vil representing inductive current, and an output end of the comparator is connected to a control end of a switching tube of a switching circuit through a driving circuit. The rising and falling processes of the ramp signal are controlled by the on signal Ton and the off signal Bon of the switching tube. As shown in fig. 2, the switching power supply control circuit shown in fig. 1 has an operating waveform in which the trend of the ramp signal Vr is opposite to the inductance current in the switching circuit, and starts to decrease at the time of switching on the switching transistor, and stops at the time of switching off the switching transistor. Wherein Vsw is the voltage of the common terminal of the main power tube and the rectifying tube of the switching power supply, and iL is the inductance current of the switching power supply.
In the prior art, the first signal Vc-Vr obtained by the difference between the compensation signal Vc and the ramp signal Vr is compared with the current sampling signal vii representing the inductor current, wherein the compensation signal Vc can be regarded as a constant value, so that the larger the ramp signal Vr is, the smaller the inductor current is. If the on period of the switching tube is larger, the value of the ramp signal at the switching tube turn-off time of the current period is larger, so that the peak value change range of the inductance current is lower.
Disclosure of Invention
The invention aims to provide a switching power supply control circuit capable of improving the variation range of an inductance current peak value and a switching power supply, and solves the technical problem of low variation range of the inductance current peak value in the prior art.
In order to achieve the above object, the present invention provides a switching power supply control circuit, including an error amplifier, a first input terminal of the error amplifier receives a feedback signal representing an output voltage of the switching power supply, a second input terminal of the error amplifier receives a reference signal, and the error amplifier outputs a compensation signal;
the switching power supply control circuit further comprises a slope compensation circuit, and the slope compensation circuit outputs a slope signal until the switching-off time of the switching tube at a certain time in the switching tube conduction period of the switching power supply;
the compensation signal and the slope signal are subjected to difference to obtain a first signal, the first signal is compared with a current sampling signal representing the inductance current to obtain a control signal, and the control signal is used for controlling the on or off of a switching tube of the switching power supply.
Optionally, the slope compensation circuit outputs a slope signal after the switching tube is turned on and delayed for a first time.
Optionally, the first time is a time when the switching tube of the previous period is turned on multiplied by a proportionality coefficient, and the proportionality coefficient is greater than 0 and less than 1.
Optionally, the time from the start point of the ramp signal to the end point of the ramp signal is a fixed value.
Optionally, in the fixed frequency control, the on time of the switching tube decreases with an increase of the input voltage.
Optionally, the first capacitor is charged during the on period of the switching tube, the voltage on the first capacitor is a first voltage at the off time of the switching tube in the previous period, and when the voltage on the first capacitor in the current period reaches an expected voltage, a ramp signal is output, wherein the expected voltage is lower than the first voltage and is in proportional relation with the first voltage.
Optionally, during the on period of the switching tube, the first capacitor is charged, the voltage on the first capacitor is the first voltage at the off time of the switching tube in the previous period, and when the voltage on the first capacitor in the current period reaches the expected voltage, a ramp signal is output, wherein the expected voltage is equal to the difference value between the first voltage and the voltage signal representing the fixed value.
Optionally, the slope compensation circuit includes a first capacitor, a first control circuit and a slope generation circuit, the first capacitor is charged during the conduction period of the switch tube, the first control circuit receives the first voltage to obtain the expected voltage, the voltage on the first capacitor in the current period is compared with the expected voltage, when the voltage on the first capacitor in the current period reaches the expected voltage, a slope generation signal is output, and the slope generation circuit receives the slope generation signal and outputs the slope signal.
Optionally, the first control circuit includes a second capacitor, a first switch, an operational amplifier, a first switching tube and a comparator, a first input end of the operational amplifier is connected to a high potential end of the first capacitor through the first switch, a first input end of the operational amplifier is connected to one end of the second capacitor, another end of the second capacitor is grounded, a second input end of the operational amplifier is connected to a second end of the first switching tube, an output end of the operational amplifier is connected to a control end of the first switching tube, a first input end of the comparator is connected to a second end of the first switching tube, a second input end of the comparator is connected to a high potential end of the first capacitor, an output end of the comparator is connected to a control end of the ramp generating circuit, a first input end or a second input end of the comparator is overlapped with a bias voltage, and the bias voltage characterizes the constant value.
Optionally, the first control circuit includes second electric capacity, first switch, operational amplifier, first switch tube and comparator, operational amplifier's first input is connected at the high potential end of first electric capacity through first switch, operational amplifier's first input is connected the one end of second electric capacity, and the other end ground connection of second electric capacity, operational amplifier's second input is connected the second end of first switch tube, operational amplifier's output is connected the control end of first switch tube, the one end of the series connection structure that first resistance and second resistance constitute is connected to the second end of first switch tube, the other end ground connection of series connection structure, the common end of first resistance and second resistance is connected to the first input of comparator, the second input of comparator is connected the high potential end of first electric capacity, and the control end of slope generating circuit is connected to the output of comparator.
Optionally, in the previous period, at the time of switching off the switching tube, the first switch is turned on, after the first control circuit samples the first voltage, the first switch is turned off, and the voltage of the second capacitor is the first voltage.
Optionally, the ramp generating circuit includes a third capacitor, and the third capacitor is charged when the ramp generating circuit receives the ramp generating signal, and is discharged when the switching tube is turned off.
The invention also provides another switching power supply control circuit, which comprises an error amplifier, wherein a first input end of the error amplifier receives a feedback signal representing the output voltage of the switching power supply, a second input end of the error amplifier receives a reference signal, and the error amplifier outputs a compensation signal, and the switching power supply control circuit is characterized in that:
the switching power supply control circuit further comprises a slope compensation circuit, and the slope compensation circuit outputs a slope signal until the switching-off time of the switching tube at a certain time in the switching tube conduction period of the switching power supply;
the current sampling signal representing the inductive current and the slope signal are superposed to obtain a first signal, the first signal is compared with the compensation signal to obtain a control signal, and the control signal is used for controlling the on or off of a main power tube of the switching power supply.
The invention also provides a switching power supply, which comprises any one of the switching power supply control circuit and the power circuit.
Compared with the prior art, the technical scheme of the invention has the following advantages: the invention outputs the slope signal at a certain moment in the switching tube conduction period of the switching power supply, delays the starting point of the slope signal, the slope of the slope signal is unchanged, the value of the slope signal at the switching tube turn-off moment after the starting point is delayed is reduced, and the compensation signal is basically constant because the compensation signal is compared with the current sampling signal representing the inductive current after the difference is made between the compensation signal and the slope signal, so that the inductive current is increased when the slope signal is reduced, and the value of the slope signal at the switching tube turn-off moment in the current period is reduced, thereby the variation range of the peak value of the inductive current is increased.
Drawings
FIG. 1 is a circuit schematic diagram of a prior art switching power supply control circuit;
FIG. 2 is a waveform diagram illustrating the operation of a prior art switching power supply control circuit;
FIG. 3 is a schematic diagram of a switching power supply control circuit according to the present invention;
FIG. 4 is a waveform diagram of the peak variation range of inductor current according to the prior art and the present invention;
FIG. 5 is a waveform diagram illustrating operation of the switching power supply control circuit of the present invention;
FIG. 6 is a diagram of another waveform of operation of the switching power supply control circuit of the present invention;
FIG. 7 is a schematic diagram of an embodiment of a slope compensation circuit;
FIG. 8 is a schematic diagram of a second embodiment of a slope compensation circuit;
FIG. 9 is a schematic diagram of an embodiment of a slope compensation circuit;
FIG. 10 is a schematic diagram of a second embodiment of a slope compensation circuit;
fig. 11 is another schematic diagram of the switching power supply control circuit of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments only. The invention is intended to cover any alternatives, modifications, equivalents, and variations that fall within the spirit and scope of the invention.
In the following description of preferred embodiments of the invention, specific details are set forth in order to provide a thorough understanding of the invention, and the invention will be fully understood to those skilled in the art without such details.
The invention is more particularly described by way of example in the following paragraphs with reference to the drawings. It should be noted that the drawings are in a simplified form and are not to scale precisely, but rather are merely intended to facilitate and clearly illustrate the embodiments of the present invention.
As shown in fig. 3, a specific structural principle of the switching power supply control circuit is illustrated. Comprising an error amplifier having a first input receiving a feedback signal V indicative of the output voltage of the switching power supply FB A second input end of the error amplifier receives a reference signal Vref, and the error amplifier outputs a compensation signal Vc;
the switching power supply control circuit also comprises a slope compensation circuit, and the slope compensation circuit outputs a slope signal V at a certain moment in the conduction period of the switching tube of the switching power supply r Until the switching-off time of the switching tube;
the compensation signal Vc and the ramp signal V r And obtaining a first signal V2 after the difference is made, wherein the first signal V2 is compared with a current sampling signal Vil representing the inductance current to obtain a control signal Vctrl, and the control signal Vctrl is used for controlling the on or off of a main power tube of the switching power supply.
The switching power supply control circuit also comprises a driving circuit for driving the switching tube to be turned on or turned off.
In the fixed frequency control, the on time of the switching tube decreases with an increase in the input voltage.
Fig. 4 is a waveform diagram of peak variation ranges of inductor current according to the prior art and the present invention. Wherein the solid line is the waveform of the first signal V2 of the present invention, and the dotted line is the waveform of the first signal V2 in the prior art. t1 is the starting point of the ramp signal, and t2 is the end point of the ramp signal, namely the turn-off time of the switching tube. V21 is the value of the switching tube at the switching-off time V2 in the present invention, V22 is the value of the switching tube at the switching-off time V2 in the prior art, the compensation signal Vc is basically a constant value, and the ramp signal Vr decreases, so that the first signal v2=vc-Vr becomes larger.
The first signal, i.e. v2=vc-Vr, after the difference between the compensation signal and the ramp signal is compared with the current sampling signal vii representing the inductor current, so that the value of V2 can represent the magnitude of the inductor current, and the value of V2 represents the magnitude of the inductor current peak value at the time t2, i.e. at the time when the switching tube is turned off, so that V21 and V22 represent the maximum value of the inductor current peak value in the present invention and the prior art, respectively. As can be seen from fig. 4, compared with the prior art, the starting point of the ramp signal is delayed, the slope of the ramp signal is unchanged, and V21 is greater than V22 at time t2, i.e. the maximum value of the peak value of the inductor current of the present invention is greater than the maximum value of the peak value of the inductor current of the prior art, so that the peak variation range of the inductor current of the present invention is greater than the variation range of the peak value of the inductor current of the prior art, and the greater range is determined by V21-V22.
The switching tube is generally referred to as a main switching tube of the switching power supply in peak control, and an auxiliary switching tube in valley control, and the invention does not limit the invention.
The principle of the slope compensation circuit is to adjust the starting point of the slope signal, and the slope of the slope signal is unchanged, so that the value of the slope signal at the switching-off moment of the switching tube is reduced after the starting point is delayed.
The invention provides two ways to adjust the starting point of the ramp signal, which are respectively:
first kind: and delaying the first time T1 after the switching tube is conducted, wherein the slope compensation circuit outputs a slope signal, the first time is the conduction time of the switching tube in the previous period multiplied by a proportionality coefficient, and the proportionality coefficient is larger than 0 and smaller than 1.
Second kind: and the time from the starting point of the ramp signal to the ending point of the ramp signal is a fixed value T2.
In the present invention, the first time T1 may be adjusted according to the on time TON of the switching tube in the previous period, or may be other time, for example, a fixed time. And the first time T1 may be other expression forms.
The waveform diagrams of the first and second modes of adjusting the starting point of the ramp signal are shown in fig. 5 and 6, respectively, where Vsw is the voltage of the common terminal of the main power tube and the rectifying tube of the switching power supply, vr is the ramp signal, iL is the inductor current signal of the switching power supply, and it can be seen in fig. 5 that after the ramp signal Vr delays the first time T1 from the on time of the switching tube, the ramp signal Vr starts to be output until the off time of the switching tube. As can be seen in fig. 6, in each period, the end point of the ramp signal is the switching off time of the switching tube, and the time from the start point to the end point of the ramp signal is a constant value T2.
The first time T1 may be adjusted according to the on-time TON of the switching tube of the previous cycle. For example, the value of T1 may be the last period switch on time Ton multiplied by a scaling factor K,0 < K < 1, and the value of the specific scaling factor K may be adjusted according to the specific circuit, but the invention is not limited to T1. The constant value T2 may also be adjusted according to the specific circuit.
Fig. 7 shows an embodiment of the ramp generating circuit of the present invention, illustrating an implementation of the first approach. And charging the first capacitor during the on period of the switching power supply switching tube, wherein the voltage on the first capacitor is the first voltage V1 at the switching-off moment of the switching tube in the previous period, and the ramp signal Vr is generated when the voltage on the first capacitor in the current period reaches the expected voltage Vth until the switching-off moment of the switching tube. The expected voltage Vth is lower than the first voltage V1 and is proportional to the first voltage, that is, the expected voltage Vth is the first voltage V1 multiplied by a scaling factor k, where k is greater than 0 and less than 1.
Fig. 8 shows a second embodiment of the ramp generating circuit of the present invention, illustrating an implementation of the second approach. And charging the first capacitor during the on period of the switching tube, outputting a ramp signal Vr when the voltage on the first capacitor in the current period reaches the expected voltage Vth at the turn-off time of the switching tube in the last period, wherein the voltage on the first capacitor is the first voltage V1. The expected voltage Vth is equal to the difference between the first voltage V1 and a voltage signal Δv characterizing the constant value T2.
It should be noted that fig. 7 and 8 are merely given as basic implementations thereof, and the final voltage of the current period in fig. 7 and 8 is greater than the previous period, and may be equal to or less than the previous period, which the present invention is not limited to.
Fig. 9 shows a specific circuit diagram of the first embodiment of the slope compensation circuit in fig. 7, where t1=k is Ton (0 < k < 1) of the previous period. Wherein the realization of k is accomplished by a voltage dividing resistor.
The slope compensation circuit comprises a first current source 11, a third switch S3, a first capacitor C1, a first control circuit and a slope generation circuit, wherein the first control circuit comprises a second capacitor C2, a first switch S1, an operational amplifier U1, a first switch tube M1, a comparator comp1, a first resistor R1 and a second resistor R2, the slope generation circuit comprises a second current source I2, a second switch S2 and a third capacitor C3, a series structure 1 consisting of the first current source 11, the third switch S3 and the first capacitor C1 is formed, one end of the series structure 1 is connected with a power supply end, and the other end of the series structure is grounded. The first input end of the operational amplifier U1 is connected to the high potential end of the first capacitor C1 through the first switch S1, the first input end of the operational amplifier is connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is grounded. The first end of the first switching tube M1 is connected with a power supply end, the second input end of the operational amplifier U1 is connected with the second end of the first switching tube M1, the output end of the operational amplifier U1 is connected with the control end of the first switching tube M1, the second end of the first switching tube M1 is connected with one end of a series structure 2 formed by a first resistor R1 and a second resistor R2, the second end of the series structure 2 is grounded, the first input end of the comparator comp1 is connected with the common end of the first resistor R1 and the second resistor R2, the second input end of the comparator comp1 is connected with the high potential end of the first capacitor C1, and the output end of the comparator comp1 is connected with the control end of the second switch S2. The series structure 3 composed of the second current source I2, the second switch S2 and the third capacitor C3 is characterized in that one end of the series structure 3 is connected with a power supply end, and the other end of the series structure 3 is grounded.
The first capacitor C1, the second capacitor C2, and the third capacitor C3 are each connected to a discharge circuit, and are discharged, which are not shown in the figure for simplicity.
In fig. 9, during the on period of the switching tube, the current source I1 is used to charge the first capacitor C1, the third switch S3 is closed at the on time of the switching tube of the switching power supply, and is opened at the off time of the switching tube, so that the voltage on the first capacitor C1 represents the on time of the switching tube of the switching power supply in the current period.
Before the switching tube of the previous period is turned off and the third switch is turned on, a first control circuit is used for sampling to obtain a voltage signal representing the on time of the switching tube of the previous period, namely a first voltage V1, and the voltage signal is firstly locked in a second capacitor C2. The voltage dividing circuit composed of the operational amplifier, the first switching tube, the first resistor R1 and the second resistor R2 is used for obtaining the expected voltage Vth, and the voltage of the common end of the first resistor R1 and the second resistor R2 is the expected voltage Vth. The expected voltage Vth characterizes the on-time TON of the last cycle multiplied by the scaling factor k, which is equal to the first voltage V1 multiplied by the scaling factor k.
In a specific operation process, the switch S3 is closed at the on time of the switching tube in the previous period, the switch S1 is closed at the off time of the switching tube, the first control circuit samples to obtain a first voltage V1 which is a voltage signal of the on time of the switching tube in the previous period, the first voltage V1 is locked in the second capacitor C2, the switch S1 is turned off (the switch S1 only plays a role of sampling at the off time of the switching tube), and then the switch S3 is turned off.
In the current period, the switch S3 is closed at the on time of the switching tube, and since the first voltage V1 representing the on time of the switching tube in the previous period is electrically latched in the second capacitor C2, the expected voltage Vth of the voltage at the common end of the first resistor R1 and the second resistor R2 is the first voltage V1 multiplied by k, the voltage V3 on the first capacitor C1 in the current period represents the on time of the switching tube in the current period, when the voltage V3 reaches the expected voltage Vth, the output ramp generating signal Vctr1 of the comparator comp1 controls the second switch S2 to be turned on, and starts to output a ramp signal, after the switching tube is turned off, the second switch S2 is turned off, the first switch S1 is turned on, the voltage on the second capacitor is updated, the first voltage V1 in the next period is obtained, and then the switch S1 is turned off, and the switch S3 is turned off.
In each period, at the switching-on time of the switching tube, the switch S3 is closed, the values of Vth and V3 are compared, when V3 reaches Vth, the comparator is turned over, the switch S2 is closed, and at the switching-off time of the switching tube, the switch S2 is opened, so that the output of a slope signal in the period is completed. At the switching-off time of the switching tube, the switch S1 is closed at the same time, a voltage signal representing the switching-on time of the switching tube in the previous period, namely a first voltage V1 is obtained by sampling, the switch S1 is turned off, the first voltage V1 is locked in the second capacitor C2 (the switch S1 only plays a role of sampling at the switching-off time of the switching tube), and the sampling has a pulse time, so that the voltage can be locked. Switch S3 is turned off. The expected voltage Vth compared in this period is sampled for the previous period, and then this period continues to sample Vth for the next period.
Fig. 10 shows a specific circuit diagram of the second embodiment of the slope compensation circuit of fig. 8, which is similar to the first embodiment, but does not need a voltage divider circuit, and is implemented by directly adding a bias voltage Voffset to the comparator comp2, where the bias voltage Voffset characterizes the fixed value, so that the time from the start point of the slope signal to the end point of the slope signal is a fixed value T2. The offset voltage Voffset overlaps the first input or the second input of the comparator.
The expected voltage Vth in fig. 10 is equal to the difference between the first voltage V1 and a voltage signal Δv characterizing the constant value T2. Therefore, if the offset voltage Voffset is superimposed on the output terminal of the switching tube, it is negative, and the offset voltage Voffset is superimposed on the other terminal of the comparator, it is positive. Other processes refer to embodiment one.
It should be noted that Vth and V3 in fig. 10 have the same meaning as that shown in fig. 9 for convenience of expression, and represent the voltage value after the bias voltage has been added, which is the value at which the comparison is made last.
The first and second embodiments are merely two implementations of the present invention, but other similar implementations are also within the scope of the present invention.
Fig. 11 illustrates another specific structural principle of the switching power supply control circuit. The switching power supply comprises an error amplifier, wherein a first input end of the error amplifier receives a feedback signal VFB representing the output voltage of the switching power supply, a second input end of the error amplifier receives a reference signal Vref, and the error amplifier outputs a compensation signal Vc;
the switching power supply control circuit further comprises a slope compensation circuit, and the slope compensation circuit outputs a slope signal Vr at a certain moment in the on period of a switching tube of the switching power supply until the switching-off moment of the switching tube;
the current sampling signal Vr1 representing the inductive current and the ramp signal Vr are superposed to obtain a first signal V2, the first signal V2 is compared with the compensation signal Vc to obtain a control signal Vctrl, and the control signal is used for controlling the on or off of a main power tube of the switching power supply.
Because the current sampling signal Vil and the ramp signal Vr representing the inductive current are overlapped, namely Vil+Vr is compared with the compensation signal Vc, the compensation signal Vc is basically constant, the ramp signal Vr is reduced, the inductive current i1 is increased, the value of the ramp signal Vr at the switching-off moment of the switching tube in the current period after the starting point delay is reduced, and therefore the peak value of the inductive current is increased.
The operation waveform of the switching power supply switch control circuit of fig. 11, the operation principle of the ramp circuit generating circuit, and other processes are the same as those of fig. 3.
Although the embodiments have been described and illustrated separately above, and with respect to a partially common technique, it will be apparent to those skilled in the art that alternate and integration may be made between embodiments, with reference to one embodiment not explicitly described, and reference may be made to another embodiment described.
The above-described embodiments do not limit the scope of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the above embodiments should be included in the scope of the present invention.
Claims (8)
1. A switching power supply control circuit comprising an error amplifier, a first input terminal of the error amplifier receiving a feedback signal indicative of an output voltage of the switching power supply, a second input terminal of the error amplifier receiving a reference signal, the error amplifier outputting a compensation signal, characterized in that:
the switching power supply control circuit further comprises a slope compensation circuit, and the slope compensation circuit outputs a slope signal until the switching-off time of the switching tube at a certain time in the switching tube conduction period of the switching power supply;
the compensation signal and the slope signal are subjected to difference to obtain a first signal, the first signal is compared with a current sampling signal representing the inductance current to obtain a control signal, the control signal is used for controlling the on or off of a switching tube of the switching power supply,
delaying for a first time after the switching tube is conducted, the slope compensation circuit outputs a slope signal,
the first time is the on time of the switching tube in the previous period multiplied by a proportionality coefficient, the proportionality coefficient is more than 0 and less than 1,
and charging the first capacitor during the on period of the switching tube, wherein the voltage on the first capacitor is the first voltage at the off time of the switching tube in the previous period, and outputting a ramp signal when the voltage on the first capacitor in the current period reaches the expected voltage, wherein the expected voltage is lower than the first voltage and is in proportional relation with the first voltage.
2. The switching power supply control circuit according to claim 1, wherein: in the fixed frequency control, the on time of the switching tube decreases with an increase in the input voltage.
3. The switching power supply control circuit according to claim 1, wherein: the slope compensation circuit comprises a first capacitor, a first control circuit and a slope generation circuit, wherein the first capacitor is charged during the conduction period of the switch tube, the first control circuit receives the first voltage to obtain the expected voltage, the voltage on the first capacitor in the current period is compared with the expected voltage, when the voltage on the first capacitor in the current period reaches the expected voltage, a slope generation signal is output, and the slope generation circuit receives the slope generation signal and outputs the slope signal.
4. A switching power supply control circuit according to claim 3, wherein: the first control circuit comprises a second capacitor, a first switch, an operational amplifier, a first switch tube and a comparator, wherein a first input end of the operational amplifier is connected to a high potential end of the first capacitor through the first switch, the first input end of the operational amplifier is connected to one end of the second capacitor, the other end of the second capacitor is grounded, a second input end of the operational amplifier is connected to a second end of the first switch tube, an output end of the operational amplifier is connected to a control end of the first switch tube, a first input end of the comparator is connected to a second end of the first switch tube, a second input end of the comparator is connected to a high potential end of the first capacitor, an output end of the comparator is connected to a control end of the slope generating circuit, a first input end or a second input end of the comparator is overlapped with a bias voltage, and the bias voltage represents a constant value.
5. The switching power supply control circuit according to claim 4, wherein: the first control circuit comprises a second capacitor, a first switch, an operational amplifier, a first switch tube and a comparator, wherein a first input end of the operational amplifier is connected to a high potential end of the first capacitor through the first switch, a first input end of the operational amplifier is connected to one end of the second capacitor, the other end of the second capacitor is grounded, a second input end of the operational amplifier is connected to a second end of the first switch tube, an output end of the operational amplifier is connected to a control end of the first switch tube, a second end of the first switch tube is connected to one end of a series structure formed by a first resistor and a second resistor, the other end of the series structure is grounded, a first input end of the comparator is connected to a common end of the first resistor and the second resistor, a second input end of the comparator is connected to the high potential end of the first capacitor, and an output end of the comparator is connected to a control end of the slope generating circuit.
6. The switching power supply control circuit according to claim 5, wherein: in the last period, at the switching tube switching-off time, the first switch is closed, after the first control circuit samples the first voltage, the first switch is opened, and the voltage of the second capacitor is the first voltage.
7. The switching power supply control circuit according to claim 6, wherein: the ramp generating circuit comprises a third capacitor, and charges the third capacitor when the ramp generating circuit receives a ramp generating signal, and discharges the third capacitor when the switching tube is turned off.
8. A switching power supply comprising a switching power supply control circuit as claimed in any one of claims 1 to 7.
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| CN111371354B (en) * | 2020-04-24 | 2021-09-14 | 合肥为民电源有限公司 | Control method for output current and output power of wind driven generator and corresponding control device |
| CN111541371A (en) * | 2020-05-09 | 2020-08-14 | 湖南省计量检测研究院 | Direct current electric energy generation circuit for new energy application |
| CN115987068A (en) * | 2023-03-17 | 2023-04-18 | 苏州锴威特半导体股份有限公司 | Driving tube control circuit, control method and switching power supply |
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