CN109921618B - Constant conduction time control method, control circuit and switching circuit - Google Patents
Constant conduction time control method, control circuit and switching circuit Download PDFInfo
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- CN109921618B CN109921618B CN201910135081.9A CN201910135081A CN109921618B CN 109921618 B CN109921618 B CN 109921618B CN 201910135081 A CN201910135081 A CN 201910135081A CN 109921618 B CN109921618 B CN 109921618B
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention discloses a constant-conduction time control method for a switching circuit, a control circuit and the switching circuit, wherein a compensation voltage is larger than a first voltage and is a second interval, the compensation voltage is smaller than the first voltage and is a first interval, and in the first interval, the slope of the conduction time of a main switching tube, which is increased along with the rising of the compensation voltage, is a first slope; in the second interval, the on time of the main switching tube increases along with the rising of the compensation voltage to form a second slope, and the second slope is larger than the first slope, wherein the compensation voltage is obtained by carrying out operational amplification on a feedback value and a reference voltage.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a constant conduction time control method, a control circuit and a switching circuit.
Background
The switch conversion circuit is widely applied in the field of power supply conversion due to the advantages of high efficiency, easiness in control and the like. In alternating current-direct current (AC-DC) conversion, in order to prevent the input current of the converter from polluting the grid, the converter is generally required to meet the power factor and harmonic requirements specified by the industry or by various countries/regions.
Among various control modes of the switching conversion circuit, constant On Time (COT) control is widely adopted due to advantages of fast transient response speed, simple structure and the like.
In the constant on-time control, the on-time is controlled by the compensation voltage COMP. In the conventional scheme, the on-time rises with the rise of the compensation voltage, and the slope is a fixed value, as shown in fig. 1. Because the compensation voltage COMP has the secondary power frequency ripple, the on time of the main switching tube of the switching conversion circuit also has the secondary power frequency ripple. This results in a decrease in THD of the switching converter circuit and a deterioration in the power factor correction effect. And when the input voltage is high, THD is worse than when the input voltage is low, and the secondary power frequency ripple on the compensation voltage is worse, so that THD when the input voltage is high.
Disclosure of Invention
Therefore, the present invention is directed to a constant on-time control method, a control circuit and a switching circuit, which are used for solving the problem of poor THD of the circuit with power factor correction in the prior art when high voltage is input.
The technical scheme of the invention is that a constant conduction time control method for a switching circuit is provided, and the conduction time of a main switching tube increases along with the rising of a compensation voltage, but the nonlinear increase of the compensation voltage is the voltage obtained by carrying out operational amplification on a feedback value and a reference voltage.
Optionally, the compensation voltage is larger than the first voltage and is a second interval, the compensation voltage is smaller than the first voltage and is a first interval, and in the first interval, the slope of the increase of the on time of the main switch tube along with the rising of the compensation voltage is a first slope; in the second interval, the slope of the conduction time of the main switch tube increasing along with the rise of the compensation voltage is a second slope, and the second slope is larger than the first slope.
Alternatively, the first slope is a constant value or increases with an increase in the compensation voltage, and the second slope is a constant value or increases with an increase in the compensation voltage.
Optionally, the switching circuit is a BUCK circuit with Power Factor Correction (PFC) or a FLYBACK circuit.
Alternatively, the switching circuit operates in a critical conduction mode or an intermittent conduction mode.
The invention also provides a constant conduction time control circuit for the switching circuit, wherein the conduction time of the main switching tube increases along with the rising of the compensation voltage to enable the compensation voltage to be a voltage obtained by carrying out operational amplification on the feedback value and the reference voltage.
Optionally, the compensation voltage is greater than the first voltage and is a second interval, the compensation voltage is less than the first voltage and is a first interval, the constant-on-time control circuit is in the first interval, and the slope of the on-time of the main switching tube increased along with the rising of the compensation voltage is a first slope; in the second interval, the slope of the conduction time of the main switching tube increased along with the rise of the compensation voltage is a second slope, the second slope is larger than the first slope, and the switching circuit works in a critical conduction mode or an intermittent conduction mode.
Alternatively, the first slope is a constant value or increases with an increase in the compensation voltage, and the second slope is a constant value or increases with an increase in the compensation voltage.
Optionally, the circuit comprises a conduction time generation circuit, wherein the conduction time generation circuit comprises a comparison circuit, a variable current source and a capacitor, the variable current source charges the capacitor, the capacitor is connected to a first input end of the comparison circuit, the compensation voltage is connected to a second input end of the comparison circuit, and the output voltage of the comparison circuit controls the main switching tube to be turned on or off; the variable current source is controlled by the compensation voltage, the variable current source having a value in the first interval that is greater than a value in the second interval.
Optionally, the circuit comprises an on-time generation circuit, wherein the on-time generation circuit comprises a comparison circuit, a current source and a nonlinear capacitor, the current source charges the nonlinear capacitor, the nonlinear capacitor is connected to a first input end of the comparison circuit, the compensation voltage is connected to a second input end of the comparison circuit, and the output voltage of the comparison circuit controls the main switching tube to be switched on or off; the nonlinear capacitance is controlled by the compensation voltage, and the value of the nonlinear capacitance in the first interval is smaller than that in the second interval.
Another technical solution of the present invention is to provide a switching circuit.
Compared with the prior art, the circuit structure and the method have the following advantages: the circuit with power factor correction has improved THD at high voltage input and good transient response at low voltage input.
Drawings
Fig. 1 schematically shows a graph of the compensation voltage COMP and the on-time TON in a conventional scheme;
Fig. 2 (a) schematically shows a graph of the compensation voltage COMP and the on-time TON according to an embodiment of the invention;
fig. 2 (b) schematically shows a graph of the compensation voltage COMP and the on-time TON according to another embodiment of the invention;
fig. 2 (c) schematically shows a graph of the compensation voltage COMP and the on-time TON according to a further embodiment of the invention;
fig. 2 (d) schematically shows a graph of the compensation voltage COMP and the on-time TON according to a further embodiment of the invention;
fig. 3 (a) schematically shows a schematic diagram of the structure of a constant on-time generating circuit and a logic circuit according to an embodiment of the present invention;
fig. 3 (b) schematically shows a circuit schematic of a constant on-time generating circuit according to another embodiment of the present invention;
fig. 3 (c) schematically shows a circuit schematic of a constant on-time generating circuit according to a further embodiment of the 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.
Constant on-time control is widely used in circuits with power factor compensation, and the on-time TON of the main switching tube is controlled by the compensation voltage COMP. In the conventional scheme, the on-time increases with the rise of the compensation voltage, and the slope is a fixed value, as shown in fig. 1. Because the compensation voltage COMP has the secondary power frequency ripple, the on time of the main switching tube of the switching conversion circuit also has the secondary power frequency ripple. This results in a decrease in THD of the switching converter circuit and a deterioration in the power factor correction effect. And when the input voltage is high, THD is worse than when the input voltage is low, and the secondary power frequency ripple on the compensation voltage is worse, so that THD when the input voltage is high.
In order to improve the input current waveform at high input voltage, the invention provides a constant conduction time control method for a switching circuit, wherein the conduction time of a main switching tube increases along with the rising of a compensation voltage to a voltage obtained by performing operational amplification on a feedback value and a reference voltage in a nonlinear manner. It should be noted that the nonlinear increase includes piecewise linearity.
In one embodiment, the compensation voltage is greater than the first voltage and is in a second interval, the compensation voltage is smaller than the first voltage and is in a first interval, and the slope of the on time of the main switch tube, which increases with the rising of the compensation voltage, is a first slope; in the second interval, the slope of the conduction time of the main switch tube increasing along with the rise of the compensation voltage is a second slope, and the second slope is larger than the first slope. When the input voltage is high, the compensation voltage COMP is low, the on time TON is small, and the compensation voltage TON is in a first interval, and when the input voltage is low, the compensation voltage COMP is in a second interval. The slope of the first interval is small, which makes the change of the on-time caused by the change of the compensation voltage small, that is, the secondary power frequency ripple on the same compensation voltage COMP, and the secondary power frequency ripple on the on-time TON is smaller. And when the input voltage is low, i.e. the second slope is large, this makes the on-time TON follow the compensation voltage COMP fast and the system response fast.
Alternatively, the first slope is a constant value or increases with an increase in the compensation voltage, and the second slope is a constant value or increases with an increase in the compensation voltage.
Referring to fig. 2 (a), the first slope and the second slope are both constant values; the first slope in fig. 2 (a) is a direct transition to the second slope. Whereas in an actual circuit the first slope transitions smoothly to the second slope. Referring to fig. 2 (b), the first slope is a constant value, and the second slope is variable and increases as the compensation voltage COMP increases; referring to fig. 2 (c), the second slope is a constant value, and the first slope is variable and increases as the compensation voltage COMP increases; referring to fig. 2 (d), both the first slope and the second slope are variable and increase with the rising of the compensation voltage COMP.
In one embodiment, the switching circuit is a BUCK circuit with Power Factor Correction (PFC) or a fliback FLYBACK circuit.
In one embodiment, the switching circuit operates in a critical conduction mode or an intermittent conduction mode.
The invention also provides a constant conduction time control circuit for the switching circuit, wherein the slope of the conduction time of the main switching tube, which is increased along with the rising of the compensation voltage, is a variable slope, and the compensation voltage is the voltage obtained by carrying out operational amplification on the feedback value and the reference voltage.
In one embodiment, the compensation voltage is greater than the first voltage and is in a second interval, the compensation voltage is less than the first voltage and is in a first interval, and the constant on-time control circuit is in the first interval, and the slope of the increase of the on-time of the main switching tube along with the increase of the compensation voltage is a first slope; in the second interval, the slope of the conduction time of the main switching tube increased along with the rise of the compensation voltage is a second slope, the second slope is larger than the first slope, and the switching circuit works in a critical conduction mode or an intermittent conduction mode.
In one embodiment, the first slope is a constant value or increases with increasing compensation voltage, and the second slope is a constant value or increases with increasing compensation voltage.
In one embodiment, referring to fig. 3 (a), the constant on-time control circuit includes an on-time generating circuit, the on-time generating circuit includes a comparing circuit U40, a variable current source I40, and a capacitor C40, the variable current source I40 charges the capacitor C40, the capacitor C40 is connected to a first input terminal of the comparing circuit U40, the compensation voltage COMP is connected to a second input terminal of the comparing circuit U40, and an output voltage of the comparing circuit U40 controls the main switching tube to be turned on or off; the variable current source I40 is controlled by the compensation voltage COMP, and the value of the variable current source I40 is greater in the first interval than in the second interval. Before the main switching tube is conducted, the capacitor C40 is reset, when the main switching tube is conducted, the PWM signal is changed from invalid to valid, the switching tube K40 is conducted, the variable current source I40 charges the capacitor C40, and when the voltage on the capacitor C40 reaches the compensation voltage COMP, the output of the comparison circuit U40 is turned over. The logic circuit U50 receives the output voltage of the comparison circuit U40, and when the output of the comparison circuit U40 turns over, the output of the logic circuit U50 changes from active to inactive, and the main switching tube is turned off. Since the main switching tube on time ton=c40 COMP/I40, that is, the larger the current value, the smaller the variation in TON with COMP. Therefore, it is necessary to set the value of the variable current source I40 in the first section to be larger than that in the second section.
In one embodiment, please refer to fig. 3 (b), a series circuit formed by connecting a current source I43 and a switch K41 in series is connected in parallel with a current source I42 as a variable current source I40, wherein the switch K41 is controlled by a compensation voltage COMP. In the first interval, the compensation voltage COMP controls the switch K41 to be turned on; in the second interval, the compensation voltage COMP controls the switch K41 to be turned off. The curve in fig. 2 (a) can be realized with the circuit of this embodiment.
In another embodiment, referring to fig. 3 (C), the constant on-time control circuit includes an on-time generating circuit, the on-time generating circuit includes a comparing circuit U40, a current source I45, and a nonlinear capacitor C40, the current source I45 charges the nonlinear capacitor C40, the nonlinear capacitor C40 is connected to a first input terminal of the comparing circuit U40, the compensation voltage COMP is connected to a second input terminal of the comparing circuit U40, and an output voltage of the comparing circuit U40 controls the main switching tube to be turned on to off; the nonlinear capacitance C40 has a smaller value in the first interval than in the second interval. The variable capacitance C40 is controlled by the compensation voltage COMP. The variable capacitance C40 may be implemented by a MOS capacitance, wherein the gate of the MOS capacitance is controlled by the compensation voltage COMP. When the compensation voltage COMP is high, the MOS capacitance value is large; when the compensation voltage COMP is low, the MOS capacitance value is small.
Another technical solution of the present invention is to provide a switching circuit.
In addition, although the embodiments are described and illustrated separately above, it will be apparent to those skilled in the art that some common techniques may be substituted and integrated between the embodiments, and that reference may be made to another embodiment without explicitly recited in one of the embodiments.
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 (11)
1. A constant on time control method for a switching circuit is characterized in that: the method comprises the steps that the conduction time of a main switching tube increases nonlinearly along with the rising of a compensation voltage, wherein the compensation voltage is obtained by performing operational amplification on a feedback value and a reference voltage, the compensation voltage is larger than a first voltage and is a second interval, the compensation voltage is smaller than the first voltage and is a first interval, and the slope of the conduction time of the main switching tube, which increases along with the rising of the compensation voltage, is a first slope; in the second section, the slope of the conduction time of the main switching tube increasing along with the rising of the compensation voltage is a second slope, and the second slope is larger than the first slope.
2. The constant on-time control method according to claim 1, characterized in that: the main switching tube conduction time increases piecewise and linearly with the rise of the compensation voltage.
3. The constant on-time control method according to claim 2, characterized in that: the first slope is a constant value or increases with the rise of the compensation voltage, and the second slope is a constant value or increases with the rise of the compensation voltage.
4. The constant on-time control method according to claim 1, characterized in that: the switch circuit is a BUCK step-down circuit or an FLYBACK FLYBACK circuit with Power Factor Correction (PFC).
5. The constant on-time control method according to claim 1, characterized in that: the switching circuit operates in a critical conduction mode or an intermittent conduction mode.
6. A constant on-time control circuit for a switching circuit, characterized by: the method comprises the steps that the conduction time of a main switching tube increases nonlinearly along with the rising of a compensation voltage, wherein the compensation voltage is obtained by performing operational amplification on a feedback value and a reference voltage, the compensation voltage is larger than a first voltage and is a second interval, the compensation voltage is smaller than the first voltage and is a first interval, and a slope of the conduction time of the main switching tube, which is increased along with the rising of the compensation voltage, is a first slope of a constant conduction time control circuit in the first interval; in the second section, the slope of the conduction time of the main switching tube increasing along with the rising of the compensation voltage is a second slope, and the second slope is larger than the first slope.
7. The constant on-time control circuit of claim 6, wherein: the switching circuit operates in a critical conduction mode or an intermittent conduction mode.
8. The constant on-time control circuit of claim 7, wherein: the first slope is a constant value or increases with the rise of the compensation voltage, and the second slope is a constant value or increases with the rise of the compensation voltage.
9. The constant on-time control circuit of claim 6, wherein: the switching circuit comprises a switching time generation circuit, a voltage compensation circuit and a switching circuit, wherein the switching time generation circuit comprises a comparison circuit, a variable current source and a capacitor, the variable current source charges the capacitor, the capacitor is connected to a first input end of the comparison circuit, the compensation voltage is connected to a second input end of the comparison circuit, and the output voltage of the comparison circuit controls the main switching tube to be switched on or off; the variable current source is controlled by the compensation voltage, the variable current source having a value in the first interval that is greater than a value in the second interval.
10. The constant on-time control circuit of claim 6, wherein: the circuit comprises a conduction time generation circuit, a control circuit and a control circuit, wherein the conduction time generation circuit comprises a comparison circuit, a current source and a nonlinear capacitor, the current source charges the nonlinear capacitor, the nonlinear capacitor is connected to a first input end of the comparison circuit, the compensation voltage is connected to a second input end of the comparison circuit, and the output voltage of the comparison circuit controls the main switching tube to be turned on or off; the nonlinear capacitance is controlled by the compensation voltage, and the value of the nonlinear capacitance in the first interval is smaller than that in the second interval.
11. A switching circuit, characterized in that: comprising a control circuit according to any of claims 6-10.
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| CN201910135081.9A CN109921618B (en) | 2019-02-19 | 2019-02-19 | Constant conduction time control method, control circuit and switching circuit |
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| CN201910135081.9A CN109921618B (en) | 2019-02-19 | 2019-02-19 | Constant conduction time control method, control circuit and switching circuit |
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| CN109921618B true CN109921618B (en) | 2024-09-17 |
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| CN112910225B (en) * | 2021-01-18 | 2022-01-07 | 杰华特微电子股份有限公司 | Control method and control circuit of switch circuit and switch circuit |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101728954A (en) * | 2008-10-21 | 2010-06-09 | 成都芯源系统有限公司 | Control circuit for DC-DC converter and method thereof |
| CN102364854A (en) * | 2011-06-30 | 2012-02-29 | 成都芯源系统有限公司 | Quasi-fixed on-time control circuit and buck switch regulating circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103532383A (en) * | 2013-10-29 | 2014-01-22 | 成都芯源系统有限公司 | Switch conversion device and control circuit and method thereof |
| CN106253661B (en) * | 2016-08-05 | 2018-12-28 | 矽力杰半导体技术(杭州)有限公司 | Control circuit, control method and the power inverter using it |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101728954A (en) * | 2008-10-21 | 2010-06-09 | 成都芯源系统有限公司 | Control circuit for DC-DC converter and method thereof |
| CN102364854A (en) * | 2011-06-30 | 2012-02-29 | 成都芯源系统有限公司 | Quasi-fixed on-time control circuit and buck switch regulating circuit |
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