CN108880252B - Linear constant current circuit - Google Patents
Linear constant current circuit Download PDFInfo
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- CN108880252B CN108880252B CN201810769376.7A CN201810769376A CN108880252B CN 108880252 B CN108880252 B CN 108880252B CN 201810769376 A CN201810769376 A CN 201810769376A CN 108880252 B CN108880252 B CN 108880252B
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- 239000003990 capacitor Substances 0.000 claims abstract description 43
- 238000005070 sampling Methods 0.000 claims abstract description 28
- 238000012512 characterization method Methods 0.000 claims abstract description 17
- 230000003321 amplification Effects 0.000 claims description 4
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000007599 discharging Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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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
- 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
- H02M1/08—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
- H02M1/14—Arrangements for reducing ripples from DC input or output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0006—Arrangements for supplying an adequate voltage to the control circuit of 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
- H02M1/0045—Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Continuous-Control Power Sources That Use Transistors (AREA)
Abstract
Disclosed is a linear constant current circuit, comprising a first and a second power switch, an output capacitor, a current sampling resistor, an operational amplifier, and a control circuit of the second power switch, wherein: the positive end of the output capacitor is connected with the positive voltage end of the circuit load, the drain electrode of the first power switch is connected with the negative voltage end of the circuit load, the source electrode of the first power switch is connected to the system ground through the current sampling resistor, the grid electrode of the first power switch is connected with the output end of the operational amplifier, the drain electrode of the second power switch is connected with the drain electrode of the first power switch, the source electrode of the second power switch is connected with the negative end of the output capacitor and serves as the reference ground of the control circuit, the grid electrode of the second power switch is connected with the output end of the control circuit, and the control circuit generates a second switch control signal for controlling the on and off of the second power switch based on output characterization voltage, second reference voltage and third reference voltage which characterize the output voltage at the two ends of the circuit load or the output capacitor.
Description
Technical Field
The invention relates to the field of circuits, in particular to a linear constant-current circuit.
Background
Fig. 1 shows an operation principle diagram of a conventional linear constant current circuit. In the linear constant current circuit shown in fig. 1, the positive terminal and the negative terminal of the output capacitor Co are connected to both ends of the load, respectively; the drain of the power switch S1 is connected with the negative end of the output capacitor Co; the source of power switch S1 is connected to system ground via current sampling resistor Rcs; the gate of the power switch S1 is connected to the output of the operational amplifier (EA), wherein: the current sampling resistor Rcs samples an output current Io flowing through a load to generate a current sampling voltage Vcs; the operational amplifier (EA) generates a switch control signal Out1 for controlling on and off of the power switch S1 based on the current sampling voltage Vcs and the reference voltage Vref to realize constant current control of the output current Io by control of the power switch S1 when the output voltage Vin fluctuates.
Fig. 2 shows waveforms of voltages and currents at some key points in the linear constant current circuit shown in fig. 1, in which: vin denotes an input voltage obtained by rectifying an ac voltage, Vo denotes an output voltage across a load or an output capacitor Co, Vcs denotes a current sampling voltage across a current sampling resistor Rcs, Vref denotes a reference voltage, and Io denotes an output current flowing through the load.
As shown in fig. 2, when the input voltage Vin is greater than the output voltage Vo, the power switch S1 works in the amplification region to control the current sampling voltage Vcs on the current sampling resistor Rcs to be equal to the reference voltage Vref, and the input voltage Vin charges the output capacitor Co while providing the output current Io to the load; when the input voltage Vin is smaller than the output voltage Vo, the power switch S1 is in a conducting state, but the input voltage Vin cannot provide the output current Io to the load, the current sampling voltage Vcs on the current sampling resistor Rcs is zero, and the output current Io flowing through the load is provided by the output capacitor Co (i.e., the output capacitor Co discharges to the load).
Specifically, in each low-frequency period, the time for the input voltage Vin to be smaller than the output voltage Vo is Tdis, the ripple magnitude of the voltage across the output capacitor Co (i.e., the ripple magnitude of the output voltage Vo) is △ V ═ Io Tdis/Co, the smaller the capacity of the output capacitor Co, the larger the ripple of the output voltage Vo is, the larger the ripple of the output current Io is, and the larger the capacity of the output capacitor Co, the smaller the ripple of the output voltage Vo is, and the smaller the ripple of the output current Io is.
In some application scenarios, the low-frequency ripple of the output current Io is required to be as small as possible, which requires that the capacity of the output capacitor Co is large, but the output capacitor Co is generally an electrolytic capacitor, and the larger the capacity is, the larger the volume is, so that the miniaturization of the power supply volume cannot be realized.
Disclosure of Invention
In view of one or more of the problems set forth above, the present invention provides a novel linear constant current circuit.
The linear constant current circuit comprises a first power switch, a second power switch, an output capacitor, a current sampling resistor, an operational amplifier and a control circuit of the second power switch, wherein: the positive end of an output capacitor is connected with the positive voltage end of a circuit load, the drain electrode of a first power switch is connected with the negative voltage end of the circuit load, the source electrode of the first power switch is connected to the system ground through a current sampling resistor, the grid electrode of the first power switch is connected with the output end of an operational amplifier, the drain electrode of a second power switch is connected with the drain electrode of the first power switch, the source electrode of the second power switch is connected with the negative end of the output capacitor and serves as the reference ground of a control circuit, the grid electrode of the second power switch is connected with the output end of the control circuit, the current sampling resistor samples output current flowing through the circuit load to generate current sampling voltage, the operational amplifier generates a first switch control signal for controlling the on and off of the first power switch based on the current sampling voltage and the first reference voltage, and the control circuit generates output characterization voltage for characterizing the circuit load or the output voltage at the two ends of the output capacitor, The second reference voltage and the third reference voltage generate a second switch control signal for controlling the on and off of the second power switch.
In some embodiments, the linear constant current circuit further includes a voltage divider network, one end of the voltage divider network is connected to the negative terminal of the output capacitor, the other end of the voltage divider network is connected to the source of the first power switch, and the output characterization voltage is obtained by dividing a voltage between a reference ground of the control circuit and a system ground by the voltage divider network.
In some embodiments, when the input voltage of the linear constant current circuit is greater than the output voltage, the first power switch operates in the amplification region, the second power switch is in the conducting state, and the input voltage charges the output capacitor while providing the output current to the circuit load.
In some embodiments, when the input voltage of the linear constant current circuit drops to a level where the output capacitor cannot be charged but is still greater than the output voltage, the control circuit controls the second power switch to change from the on state to the off state based on the output characterization voltage and the second reference voltage to cut off a path through which the output capacitor discharges to the circuit load.
In some embodiments, when the input voltage of the linear constant current circuit drops below the output voltage so as to be unable to provide the output current to the circuit load, the first power switch is in the conducting state, and the control circuit controls the second power switch to change from the off state to the conducting state based on the output characterization voltage and the third reference voltage, so that the output capacitor provides the output current to the circuit load.
In some embodiments, when the output characterization voltage is greater than the second reference voltage, the control circuit outputs a low level second switch control signal to control the second power switch to change from the on state to the off state.
In some embodiments, when the output characterization voltage is greater than a third reference voltage, the control circuit outputs a second switch control signal with a high level to control the second power switch to change from an off state to an on state, and the third reference voltage is greater than the second reference voltage.
According to the linear constant current circuit provided by the embodiment of the invention, the current average value near the peak value of the output current in each power frequency period can be reduced, so that the low-frequency ripple of the output current is reduced.
Drawings
The invention may be better understood from the following description of specific embodiments thereof taken in conjunction with the accompanying drawings, in which:
fig. 1 shows an operating schematic diagram of a conventional linear constant current circuit;
FIG. 2 illustrates waveforms of voltage and current at some key points in the linear constant current circuit shown in FIG. 1;
FIG. 3 illustrates a schematic diagram of the operation of a linear constant current circuit according to an embodiment of the present invention;
fig. 4 shows waveforms of voltages and currents at some key points in the linear constant current circuit shown in fig. 3.
Detailed Description
Features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is in no way limited to any specific configuration set forth below, but rather covers any modification, substitution, and improvement of elements, components, and algorithms without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present invention.
Fig. 3 shows a schematic diagram of the operation of a linear constant current circuit according to an embodiment of the invention. As shown in fig. 3, the linear constant current circuit according to the embodiment of the present invention includes a power switch S2 and its control circuit, in addition to the circuit parts that are identical to those of the linear constant current circuit shown in fig. 1.
In the linear constant current circuit shown in fig. 3, the drain of the power switch S2 is connected to the drain of the power switch S1; the source of the power switch S2 is connected to the negative terminal of the output capacitor Co and serves as the reference ground for the control circuit of the power switch S2; the grid of the power switch S2 is connected with the output end of the control circuit; a voltage division network consisting of resistors R1 and R2 divides the voltage between the reference ground of the control circuit of the power switch S2 and the system ground to generate an output characterization voltage VFB which characterizes the output voltage Vo; the control circuit of the power switch S2 generates a switch control signal Out2 for controlling on and off of the power switch S2 based on the output characterization voltage VFB, the reference voltage Vref1, and the reference voltage Vref2 to reduce the magnitude of ripple of the output current Io when the input voltage Vin fluctuates at a low frequency.
In the linear constant current circuit shown in fig. 3, when the input voltage Vin is greater than the output voltage Vo, the power switch S1 operates in the amplification region to control the current sampling voltage Vcs flowing through the current sampling resistor Rcs to be constant; when the input voltage Vin is smaller than the output voltage Vo, the power switch S1 is in a conducting state, the input voltage Vin cannot provide the output current Io to the load, the current sampling voltage Vcs on the current sampling resistor Rcs is zero, and the output current Io flowing through the load is provided by the output capacitor Co (i.e., the output capacitor Co discharges to the load).
Fig. 4 shows waveforms of voltages and currents at some key points in the linear constant current circuit shown in fig. 3, where: vin denotes an input voltage obtained by rectifying an alternating voltage, Vo denotes an output voltage across the load, Vcs denotes a current sampling voltage across a current sampling resistor Rcs, ref1 and ref2 denote two reference voltages in a control circuit for the power switch S2, Io denotes an output current flowing through the load, and Out2 denotes a switch control signal generated by the control circuit for the power switch S2 for controlling on and off of the power switch S2.
As shown in fig. 4, when the input voltage Vin is greater than the output voltage Vo, the input voltage Vin charges the output capacitor Co while providing the output current Io to the load, and the power switch S2 is in a conducting state.
As shown in fig. 4, when the input voltage Vin drops to near the output voltage Vo, the input voltage Vin cannot charge the output capacitor Co but can still provide the output current Io to the load; at this time, the output characterization voltage FB is greater than the reference voltage ref2, and the comparator 2 outputs a high-level control signal off; the control circuit of the power switch S2 outputs a low level switch control signal Out2 to control the power switch S2 to change from an on state to an off state, thereby cutting off the path of the output capacitor Co discharging the load.
As shown in fig. 4, when the input voltage Vin drops to be less than the output voltage Vo, the input voltage Vin cannot charge the output capacitor Co nor provide the output current Io to the load; at this time, the output characterization voltage FB is greater than the reference voltage ref1, and the comparator 1 outputs a high-level control signal on; the control circuit of the power switch S2 outputs a high level of the switch control signal Out2 to control the power switch S2 to change from an off state to an on state, so that the output capacitor Co provides the output current Io to the load.
Here, it should be noted that the control signals on and off are control signals whose rising edges are active, that is, they are active at the moment of changing from the low level to the high level.
The linear constant current circuit shown in fig. 3 can reduce the average value of the current in the vicinity of the peak value of the output current Io in each power frequency cycle, thereby reducing the low-frequency ripple of the output current Io.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the algorithms described in the specific embodiments may be modified without departing from the basic spirit of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (6)
1. A linear constant current circuit comprises a first power switch, a second power switch, an output capacitor, a current sampling resistor, an operational amplifier and a control circuit of the second power switch, wherein:
the positive end of the output capacitor is connected with the positive voltage end of a circuit load, the drain electrode of the first power switch is connected with the negative voltage end of the circuit load, the source electrode of the first power switch is connected to the system ground through the current sampling resistor, the grid electrode of the first power switch is connected with the output end of the operational amplifier,
the drain of the second power switch is connected with the drain of the first power switch, the source of the second power switch is connected with the negative end of the output capacitor and is used as the reference ground of the control circuit, the grid of the second power switch is connected with the output end of the control circuit,
the current sampling resistor samples an output current flowing through the circuit load to generate a current sampling voltage, the operational amplifier generates a first switch control signal for controlling on and off of the first power switch based on the current sampling voltage and a first reference voltage,
the control circuit generates a second switch control signal for controlling the turning on and off of the second power switch based on an output characterization voltage characterizing an output voltage across the circuit load or the output capacitor, a second reference voltage, and a third reference voltage,
when the input voltage of the linear constant current circuit is larger than the output voltage, the first power switch works in an amplification area, the second power switch is in a conducting state, and the input voltage provides the output current for the circuit load and charges the output capacitor at the same time.
2. The linear constant current circuit of claim 1, further comprising a voltage divider network having one end connected to the negative terminal of the output capacitor and the other end connected to the source of the first power switch, wherein the output characterization voltage is obtained by dividing a voltage between a reference ground of the control circuit and a system ground by the voltage divider network.
3. The linear constant current circuit of claim 1, wherein the control circuit controls the second power switch from an on state to an off state based on the output characterization voltage and the second reference voltage to break a path through which the output capacitor discharges the circuit load when an input voltage of the linear constant current circuit drops to a level that cannot charge the output capacitor but is still greater than the output voltage.
4. The linear constant current circuit of claim 1, wherein the first power switch is in an on state when an input voltage of the linear constant current circuit drops below the output voltage such that the output current cannot be provided to the circuit load, the control circuit controlling the second power switch from an off state to an on state based on the output characterization voltage and the third reference voltage such that the output capacitor provides the output current to the circuit load.
5. The linear constant current circuit of claim 3 or 4, wherein when the input voltage of the linear constant current circuit drops to a level where the output capacitor cannot be charged but is still greater than the output voltage, the output current is supplied to the circuit load, and the output characterization voltage is greater than the second reference voltage, the control circuit outputs the second switch control signal at a low level to control the second power switch to change from an on state to an off state.
6. The linear constant current circuit of claim 5, wherein when the input voltage of the linear constant current circuit drops below the output voltage so that the output current cannot be supplied to the circuit load and the output characterization voltage is greater than the third reference voltage, the control circuit outputs the second switch control signal at a high level to control the second power switch to change from an off state to an on state, and the third reference voltage is greater than the second reference voltage.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810769376.7A CN108880252B (en) | 2018-07-13 | 2018-07-13 | Linear constant current circuit |
| TW107129144A TWI674492B (en) | 2018-07-13 | 2018-08-21 | Linear constant current circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810769376.7A CN108880252B (en) | 2018-07-13 | 2018-07-13 | Linear constant current circuit |
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| Publication Number | Publication Date |
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| CN108880252A CN108880252A (en) | 2018-11-23 |
| CN108880252B true CN108880252B (en) | 2020-04-28 |
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| CN201810769376.7A Active CN108880252B (en) | 2018-07-13 | 2018-07-13 | Linear constant current circuit |
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| CN (1) | CN108880252B (en) |
| TW (1) | TWI674492B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109407744B (en) * | 2018-12-03 | 2020-03-27 | 昂宝电子（上海）有限公司 | Linear constant current control system and method for constant current control of a load |
| CN113992161B (en) * | 2021-10-27 | 2022-05-20 | 陕西亚成微电子股份有限公司 | Dynamic current supply circuit and method for reducing ripples |
| CN115932380A (en) * | 2023-02-23 | 2023-04-07 | 杰华特微电子股份有限公司 | Power detection circuit and detection method of switching circuit and switching circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2004062374A (en) * | 2002-07-26 | 2004-02-26 | Seiko Instruments Inc | Voltage regulator |
| TW200910044A (en) * | 2007-08-24 | 2009-03-01 | Vastview Tech Inc | Constant current regulating circuit with a current sensing loop |
| JP2009290937A (en) * | 2008-05-27 | 2009-12-10 | Toshiba Microelectronics Corp | Switching power supply |
| CN102064703B (en) * | 2010-11-04 | 2013-11-06 | 成都芯源系统有限公司 | Constant current output control device and method for switching power supply |
| JP6344956B2 (en) * | 2013-04-19 | 2018-06-20 | ローム株式会社 | Power circuit |
| CN104656728A (en) * | 2013-11-18 | 2015-05-27 | 西安丁子电子信息科技有限公司 | Negative voltage constant current source circuit |
| CN104122924B (en) * | 2014-07-18 | 2016-08-24 | 苏州华兴源创电子科技有限公司 | A kind of switching mode mu balanced circuit and the constant pressure and flow comprising this circuit produce circuit |
| CN104202874B (en) * | 2014-09-01 | 2016-10-05 | 矽力杰半导体技术(杭州)有限公司 | The LED drive circuit of a kind of single inductance and driving method |
| CN104821552B (en) * | 2014-10-20 | 2018-04-27 | 矽力杰半导体技术(杭州)有限公司 | Excess temperature protection method, circuit and the linear drive circuit with the circuit |
| CN105101539B (en) * | 2015-07-13 | 2018-06-29 | 矽力杰半导体技术(杭州)有限公司 | Constant current driver circuit for LED |
| JP6439653B2 (en) * | 2015-10-26 | 2018-12-19 | 株式会社デンソー | Constant voltage power circuit |
| CN107229302B (en) * | 2017-06-30 | 2018-08-03 | 西安理工大学 | The system on chip of voltage controlled current source driving circuit and put forward high-precision method using it |
| CN107979899A (en) * | 2017-12-27 | 2018-05-01 | 苏州菲达旭微电子有限公司 | A kind of linear general pump feeds constant-current circuit and has its LED light |
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2018
- 2018-07-13 CN CN201810769376.7A patent/CN108880252B/en active Active
- 2018-08-21 TW TW107129144A patent/TWI674492B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| TWI674492B (en) | 2019-10-11 |
| CN108880252A (en) | 2018-11-23 |
| TW202006494A (en) | 2020-02-01 |
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