CN107707124A - A kind of current sampling circuit - Google Patents
A kind of current sampling circuit Download PDFInfo
- Publication number
- CN107707124A CN107707124A CN201710862715.1A CN201710862715A CN107707124A CN 107707124 A CN107707124 A CN 107707124A CN 201710862715 A CN201710862715 A CN 201710862715A CN 107707124 A CN107707124 A CN 107707124A
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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
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
-
- 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
- H02M1/0009—Devices or circuits for detecting current in a converter
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses a kind of current sampling circuit, can be applied to the primary current sampling of the topology such as anti exciting converter, forward converter, by controlling IC current sample pin prebias DC voltage, can greatly reduce the sampled voltage of primary current sampling resistor.This current sample method is significantly reduced the resistance and power consumption of sampling resistor, lifts product efficiency and product power density, while has widened the application field for directly by power resistor sample primary current, and circuit easily realize with it is practical.
Description
Technical field
The present invention relates to the primary side electricity of a kind of primary current sample circuit of isolated converter, more particularly to anti exciting converter
Flow sample circuit.
Background technology
On lower-powered isolated converter, as power output be less than 10W DC/DC converters, due to cost, volume
Etc. limitation, the primary current sampling plan that circuit is more complicated or space-consuming is larger such as transformer should not be used.Tradition
Solution as shown in figure 1, by under the main power N-MOS pipes of anti exciting converter Series power resistance to input ground, directly
Connect overpower resistance to sample primary current, and input to control IC primary current sampling is drawn after LPF
Pin, while in order to ensure that wide input voltage product crosses the uniformity of flow point, in primary current sampling pin increase and input voltage
The electric voltage feed forward being inversely proportional.
Program circuit structure is easy and effective, can both ensure that the sampling of primary current is quick and undistorted, and cost is low, body
Product is small, therefore is widely applied on small-power product.
However, when the primary current increase of isolated converter, there is current sample in above-mentioned this current sampling circuit
The problem of resistance R1 power consumptions are larger, when product power is larger, more resistance need to be used to carry out used in parallel so that product is imitated
Rate is relatively low, temperature rise, cost increase, take fabric swatch space increase the problems such as, the current sampling circuit power it is larger every
It is restricted from the application in converter or the small-power product of high power density.
The content of the invention
The invention solves the sampling resistor power consumption of above-mentioned isolated converter primary current sample circuit it is larger the problem of,
A kind of isolated converter primary current method of sampling is provided so that sampling resistor power consumption is smaller, so as to reduce sampling resistor quantity,
Product efficiency and product power density are lifted, the application field of the current sample mode, and the letter of this method circuit structure can be widened
It is single, easily realize with it is practical.
The object of the present invention is achieved like this, a kind of current sampling circuit, including sampling resistor R1, low-pass filter circuit
The primary current of external circuit is sampled, is converted to voltage sampling signal with control IC, described sampling resistor R1；LPF electricity
The input on road is connected to described voltage sampling signal, for filtering out high frequency voltage spike present in voltage sampling signal,
Then current sample pin of the voltage sampling signal to control IC after exporting after filtering；It is characterized in that：It is inclined also to include direct current
Circuits, the first terminal connection control IC of DC bias circuit current sample pin, the Second terminal of DC bias circuit connect
It is connected to power input positive pole or controls IC power supply pin VCC, for reduces the power consumption of the sampling resistor R1.
Preferably, described DC bias circuit is included described in resistance R4, described resistance R4 the first terminal connection
Control IC current sample pin, the power supply pin VCC of the control IC described in described resistance R4 Second terminal connection.
Further, described DC bias circuit also includes linear voltage-stabilizing circuit, and the input of linear voltage-stabilizing circuit connects
Input voltage positive pole is connect, the current sample pin for the control IC provides a stable DC offset voltage；The resistance R4
Second terminal be changed to connect described linear voltage-stabilizing circuit output end by the power supply pin VCC for connecting described control IC.
Preferably, described linear voltage-stabilizing circuit includes NPN triode Q2, voltage-stabiliser tube D2 and resistance R5, the resistance R5
The first terminal connection power input positive pole, the Second terminal of the resistance R5 connects the negative electrode of the voltage-stabiliser tube D2 and described
NPN triode Q2 base stage, the anode connection power input negative pole of the voltage-stabiliser tube D2, the colelctor electrode of the NPN triode Q2
Connect power input positive pole, the emitter stage connection resistance R4 of NPN triode Q2 Second terminal.
Preferably, described DC bias circuit includes constant-current source IC2, and described constant-current source IC2 anodes connect described electricity
Source inputs positive pole, and described constant-current source IC2 negative electrodes connect described control IC current sample pin.
Preferably, a kind of current sampling circuit also includes electric voltage feed forward circuit, is connected to power input positive pole and control IC
Current sample pin between.
Preferably, described electric voltage feed forward circuit includes resistance R3, the resistance R3 one end connection power input positive pole,
The other end of the resistance R3 connects the current sample pin of the control IC.
Preferably, low-pass filter circuit is included described in resistance R2 and electric capacity C2, described resistance R2 the first terminal connection
Electric capacity C2 the first terminal and described control IC current sample pin, described resistance R2 Second terminal connection external electrical
The voltage sampling signal of sampling resistor in road, the Second terminal connection power input negative pole of the second described electric capacity C2.
Operation principle is：The described IC current sample pin CS that controls is current sampling signal input, for detecting primary side
Current signal；The primary current of anti exciting converter has also been superimposed because transformer parasitic capacitance produces in addition to primary side exciting curent
High frequency spikes electric current, first resistor R1 sampling voltage signal high frequency spikes voltage be present, low-pass filter circuit is to the high frequency
Due to voltage spikes is filtered, to avoid controlling IC false triggerings；
When output current increases, the primary side peak point current Ip of anti exciting converter can accordingly increase, when reaching described control
After IC current samples pin voltage processed reaches described control IC setting values, IC can enter overcurrent protection pattern；Due to inverse-excitation converting
The primary side peak point current Ip sizes of device are inversely proportional with input voltage, if no-voltage feed forward circuit, for wide input voltage range
Anti exciting converter, product cross the high limit of the small input of flow point input lower bound greatly, and increase feed forward circuit can be superimposed on ac voltage signal
One direct current signal being inversely proportional with input voltage so that crest voltage and input in described control IC current sample pin
Voltage is close to so as to cross flow point suitable in whole input voltage range section for product, being favorably improved the reliable of product
Property, fixed for input voltage or the less application of input voltage range, the primary side caused by without changing to input voltage
Curent change compensates, can be without described electric voltage feed forward circuit.
There are control IC current sample pin voltage waveforms during DC offset voltage as shown in figure 3, increased direct current biasing is electric
Road, the DC component VDC of VCS voltage can be made relatively stable, even if increasing larger bias voltage remains to the output for making product
Flow point keeps relative equilibrium, and because VCS crest voltages and traditional scheme difference are little, VCS AC portions VAC is significantly reduced,
VCS AC portions VAC is approximately equal to the voltage at first resistor both ends, therefore the resistance of first resistor can be obviously reduced, so as to drop
Low first resistor power consumption, reduce sampling resistor quantity, reach the beneficial effect for improving product efficiency, lifting product power density.
Brief description of the drawings
Fig. 1 is conventional current sampling principle figure；
Fig. 2 is first embodiment of the invention circuit block diagram；
Fig. 3 controls IC current sample pin voltage waveforms when increasing direct current biasing for the present invention；
Fig. 4 is the circuit theory diagrams that first embodiment of the invention circuit is applied to flyback topologies；
Fig. 5 is the circuit theory diagrams that second embodiment of the invention circuit is applied to flyback topologies；
Fig. 6 is the circuit theory diagrams that fourth embodiment of the invention circuit is applied to flyback topologies.
Embodiment
First embodiment
Fig. 4 shows the schematic diagram of first embodiment, and its power stage topology is flyback topologies.Flyback topologies circuit includes one
Transformer T1, a N-MOS pipes Q1, the first diode D1, the first electric capacity C1, described transformer include the first primary side around
Group, the first vice-side winding；The annexation of circuit of reversed excitation is：Described the first primary side winding different name end connection power input is just
Pole, the drain electrode of the N-MOS pipes Q1 described in described the first primary side winding termination of the same name, described N-MOS pipes Q1 source electrode output
Current sampling circuit of the electric current to the present invention；The Same Name of Ends of the first described vice-side winding connects the sun of the first diode D1
Pole, the negative electrode connection output head anode of the first diode D1, the different name end connection of the first described vice-side winding are described
Negative pole of output end, the first terminal of the first described electric capacity C1 connect output head anode, the Second terminal of the first described electric capacity C1
Connect negative pole of output end.
A kind of current sampling circuit of the present invention, including sampling resistor R1, low-pass filter circuit and control IC, in addition to it is straight
Flow biasing circuit.The primary current signal of described sampling resistor R1 sampling flyback topologies circuits, is converted to voltage sampling signal；
Voltage sampling signal described in the input connection of low-pass filter circuit, for filtering out high-frequency electrical present in voltage sampling signal
Pointing peak, then export current sample pin of the filtered voltage sampling signal to control IC；The first end of DC bias circuit
Son connection control IC current sample pin CS, the Second terminal of DC bias circuit are connected to control IC power supply pin VCC, are used for
Reduce the power consumption of the sampling resistor R1.
The first terminal that low-pass filter circuit includes second resistance R2 and the second electric capacity C2, described second resistance R2 connects
The first terminal of the second described electric capacity C2, the source electrode of the N-MOS pipes described in described second resistance R2 Second terminal connection,
The Second terminal connection power input negative pole of the second described electric capacity C2, while the first terminal connection institute of the second described electric capacity
The control IC stated current sample pin；DC bias circuit includes the 4th resistance R4, the first terminal of the 4th described resistance R4
The confession of control IC described in the described control IC of connection current sample pin CS, the 4th described resistance R4 Second terminal connection
Electric pin VCC.
Operation principle is：The described power supply pin voltage for controlling IC is metastable DC voltage VCC, usually 10V
Left and right, VCC carries out partial pressure by the 4th resistance R4, second resistance R2, first resistor R1, in described control IC current sample
DC offset voltage VDC sizes caused by pin CS are VCC* (R1+R2)/(R1+R2+R4), because R1 is much smaller than R2 and R4, therefore
VDC sizes are approximately VCC*R2/ (R2+R4), the protection voltage that IC corresponding to described control IC current sample pin CS is set
Usually 0.5V~1V, as TI UC2843 controls IC, to make IC mistakes flow point be set as usual 1.5 times of proper Io left sides
The right side, the voltage VCS of maximum current sampling signal during general anti exciting converter normal work should be greater than 0.6V, if increased straight
Bias voltage 0.4V is flowed, then the crest voltage at first resistor R1 both ends can be reduced to 0.3V or so (because the resistance of first resistor subtracts
Small, VCS crest voltages need to suitably increase, to ensure that it is suitable that product crosses flow point), because primary current size is constant, determined by ohm
Restrain R=V/I to understand, in the case of the voltage reduction half at first resistor R1 both ends, the resistance of described first resistor can be corresponding
Reduce half, and by P=I2R understand, flow through first resistor current effective value it is constant in the case of, described first resistor
Resistance reduces half, and the loss of described first resistor can reduce half；Due to the 4th described resistance and the described second electricity
The resistance of resistance is larger, and the power consumption of the 4th described resistance and described second resistance is can be controlled within 10mW, and loss substantially may be used
To ignore；The practical application in a wide input 6W products, described first resistor power consumption can reduce 0.165W, consider resistor power
Drop volume, 3~4 1206 1/2W resistor coupled in parallel need to be used to use using the first resistor described in during traditional scheme, and use this hair
It is bright, it is only necessary to which that 2 1206 1/2W resistor coupled in parallel uses can meet that volume requirement drops in resistor power.
Second embodiment
Fig. 5 shows the schematic diagram of second embodiment, and its power stage topology is flyback topologies, different from first embodiment
It is：DC bias circuit by constant-current source IC2, realize by the caused voltage in the second resistance and the first resistor, described
Constant-current source IC2 anodes connect described power input positive pole, described constant-current source IC2 negative electrodes connect the of the second described electric capacity C2
One terminal, i.e. constant-current source IC2 negative electrodes connect control IC current sample pin.
Operation principle is：Described constant current source output current flows through R2, R1, because described constant current source output current is relative
Stable, caused pressure drop is also relatively stable on R2, R1, so as to beneficial effect as available and case study on implementation one kind.It is other
Circuit connecting relation and principle are identical with first embodiment, will not be repeated here.
3rd embodiment
On the basis of first embodiment and second embodiment, electric voltage feed forward circuit is added, is being connected to power input just
Between pole and the current sample pin CS for controlling IC.
The electric voltage feed forward circuit of the present invention includes 3rd resistor R3, R3 the first terminal connection power input positive pole, R3's
Second terminal connects R2 the first terminal.
In the case where input voltage is not fixed or input voltage range is wider, product crosses flow point can be by described first
Resistance, described 3rd resistor are adjusted with reference to the 4th described resistance and second resistance, or by described first resistor,
Described 3rd resistor combination constant-current source IC2 and second resistance are adjusted so that product crosses flow point in input voltage range
It is relatively stable, while the available beneficial effect similar with first embodiment and second embodiment.
Fourth embodiment
Fig. 6 shows the schematic diagram of fourth embodiment, on the basis of first embodiment, the 4th electricity of DC bias circuit
The Second terminal connected mode for hindering R4 is changed to described linear voltage-stabilizing circuit output end by described control IC power supply pin VCC,
Linear voltage-stabilizing circuit provides a stable DC offset voltage for control IC CS pin.Remaining connected mode is constant.It is linear steady
Volt circuit includes the first NPN triode Q2, the second voltage-stabiliser tube D2 and the 5th resistance R5, its connected mode are：R5 the first terminal
Power input positive pole, R5 Second terminal connection D2 negative electrode and Q2 base stage are connected, D2 anode connects power input negative pole,
Q2 colelctor electrode connection power input positive pole, Q2 emitter stage connect the 4th resistance R4 Second terminal.
The mode not limited to this of DC bias circuit, every circuit that can provide stable DC offset voltage, is all suitable for
In the present invention.DC bias circuit can also use with electric voltage feed forward electrical combination.
Above is a kind of current sampling circuit of the present invention applies the embodiment in flyback topologies circuit, the present invention is together
Sample can apply in forward topology circuit, the annexation and principle all same of circuit.
It the above is only the preferred embodiment of the present invention, it is noted that above-mentioned preferred embodiment is not construed as pair
The limitation of the present invention, for those skilled in the art, adds different voltage stabilizings, control in circuit of the present invention
Strategy, similar beneficial effect can be obtained, for those skilled in the art, not depart from the present invention's
In spirit and scope, some improvements and modifications can also be made, these improvements and modifications also should be regarded as protection scope of the present invention,
Here no longer repeated with embodiment, protection scope of the present invention should be defined by claim limited range.
Claims (8)
1. a kind of current sampling circuit, including sampling resistor R1, low-pass filter circuit and control IC, described sampling resistor R1 are adopted
The primary current of sample external circuit, is converted to voltage sampling signal；The voltage that the input connection of low-pass filter circuit is described is adopted
Sample signal, for filtering out high frequency voltage spike present in voltage sampling signal, the voltage sample after then exporting after filtering
Current sample pin of the signal to control IC；It is characterized in that：Also include DC bias circuit, the first terminal of DC bias circuit
Connection control IC current sample pin, the Second terminal of DC bias circuit are connected to power input positive pole or control IC power supply
Pin VCC, for reducing the power consumption of the sampling resistor R1.
2. current sampling circuit according to claim 1, it is characterised in that：Described DC bias circuit includes resistance
The current sample pin of control IC described in R4, described resistance R4 the first terminal connection, described resistance R4 Second terminal
The described control IC of connection power supply pin VCC.
3. current sampling circuit according to claim 1, it is characterised in that：Described DC bias circuit includes constant-current source
IC2, described constant-current source IC2 anodes connect described power input positive pole, and described constant-current source IC2 negative electrodes meet described control IC
Current sample pin.
4. current sampling circuit according to claim 2, it is characterised in that：Described DC bias circuit also includes linear
Mu balanced circuit, the input connection input voltage positive pole of linear voltage-stabilizing circuit, the current sample pin for the control IC provide one
The DC offset voltage of individual stabilization；The Second terminal of the resistance R4 is changed to connect by the power supply pin VCC for connecting described control IC
Connect described linear voltage-stabilizing circuit output end.
5. current sampling circuit according to claim 4, it is characterised in that：Described linear voltage-stabilizing circuit includes NPN tri-
Pole pipe Q2, voltage-stabiliser tube D2 and resistance R5, the resistance R5 the first terminal connection power input positive pole, the second of the resistance R5
Terminal connects the negative electrode of the voltage-stabiliser tube D2 and the base stage of the NPN triode Q2, the anode connection power supply of the voltage-stabiliser tube D2
Input negative pole, the colelctor electrode connection power input positive pole of the NPN triode Q2, the emitter stage connection of the NPN triode Q2
Resistance R4 Second terminal.
6. the current sampling circuit according to any one of claim 2 to 5, it is characterised in that：Also include electric voltage feed forward electricity
Road is connected between power input positive pole and the current sample pin for controlling IC.
7. current sampling circuit according to claim 6, it is characterised in that：Described electric voltage feed forward circuit includes resistance
R3, the resistance R3 one end connection power input positive pole, the other end connection control IC of resistance R3 electric current are adopted
Sample pin.
8. current sampling circuit according to claim 1, it is characterised in that：Described low-pass filter circuit includes resistance R2
With electric capacity C2, electric capacity C2 the first terminal and described control IC electric current described in described resistance R2 the first terminal connection
Sample pin, described resistance R2 Second terminal connection external circuit in sampling resistor voltage sampling signal, described second
Electric capacity C2 Second terminal connection power input negative pole.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710862715.1A CN107707124A (en) | 2017-09-22 | 2017-09-22 | A kind of current sampling circuit |
| PCT/CN2018/094818 WO2019056830A1 (en) | 2017-09-22 | 2018-07-06 | Current sampling circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710862715.1A CN107707124A (en) | 2017-09-22 | 2017-09-22 | A kind of current sampling circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN107707124A true CN107707124A (en) | 2018-02-16 |
Family
ID=61171925
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710862715.1A Withdrawn CN107707124A (en) | 2017-09-22 | 2017-09-22 | A kind of current sampling circuit |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN107707124A (en) |
| WO (1) | WO2019056830A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2019056830A1 (en) * | 2017-09-22 | 2019-03-28 | 广州金升阳科技有限公司 | Current sampling circuit |
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| US20080316783A1 (en) * | 2007-06-04 | 2008-12-25 | Texas Instruments Incorporated | Interleaved power factor correction pre-regulator phase management circuitry |
| CN102255511A (en) * | 2011-06-24 | 2011-11-23 | 航天长峰朝阳电源有限公司 | Resistive network signal compensation technique |
| CN203481799U (en) * | 2013-09-02 | 2014-03-12 | 广州德励电子科技有限公司 | Flyback bias protection circuit |
| CN104540292A (en) * | 2014-12-31 | 2015-04-22 | 生迪光电科技股份有限公司 | Dimming circuit applicable to silicon-controlled light regulator circuit and dimming system |
| CN106155163A (en) * | 2016-09-19 | 2016-11-23 | 中国电子科技集团公司第十八研究所 | Static compensation-based current sampling circuit at power positive terminal of space power supply controller |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0866021A (en) * | 1994-08-24 | 1996-03-08 | Star Micronics Co Ltd | Switching power supply |
| CN202043032U (en) * | 2011-05-19 | 2011-11-16 | 深圳市振华微电子有限公司 | Micropower starting circuit of switching power supply |
| JP2013192329A (en) * | 2012-03-13 | 2013-09-26 | Yokogawa Electric Corp | Switching power supply device |
| CN107707124A (en) * | 2017-09-22 | 2018-02-16 | 广州金升阳科技有限公司 | A kind of current sampling circuit |
-
2017
- 2017-09-22 CN CN201710862715.1A patent/CN107707124A/en not_active Withdrawn
-
2018
- 2018-07-06 WO PCT/CN2018/094818 patent/WO2019056830A1/en active Application Filing
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080316783A1 (en) * | 2007-06-04 | 2008-12-25 | Texas Instruments Incorporated | Interleaved power factor correction pre-regulator phase management circuitry |
| CN102255511A (en) * | 2011-06-24 | 2011-11-23 | 航天长峰朝阳电源有限公司 | Resistive network signal compensation technique |
| CN203481799U (en) * | 2013-09-02 | 2014-03-12 | 广州德励电子科技有限公司 | Flyback bias protection circuit |
| CN104540292A (en) * | 2014-12-31 | 2015-04-22 | 生迪光电科技股份有限公司 | Dimming circuit applicable to silicon-controlled light regulator circuit and dimming system |
| CN106155163A (en) * | 2016-09-19 | 2016-11-23 | 中国电子科技集团公司第十八研究所 | Static compensation-based current sampling circuit at power positive terminal of space power supply controller |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2019056830A1 (en) * | 2017-09-22 | 2019-03-28 | 广州金升阳科技有限公司 | Current sampling circuit |
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| Publication number | Publication date |
|---|---|
| WO2019056830A1 (en) | 2019-03-28 |
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Application publication date: 20180216 |