CN101807857B - Current sampling circuit - Google Patents
Current sampling circuit Download PDFInfo
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- CN101807857B CN101807857B CN2010101339236A CN201010133923A CN101807857B CN 101807857 B CN101807857 B CN 101807857B CN 2010101339236 A CN2010101339236 A CN 2010101339236A CN 201010133923 A CN201010133923 A CN 201010133923A CN 101807857 B CN101807857 B CN 101807857B
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Abstract
The invention discloses a current sampling circuit and relates to the technical field of switching power supply by using a resonant zero current technology. The current sampling circuit comprises a sampling branch circuit, a sampling resistor and a potential translational circuit, wherein the sampling branch circuit is connected in parallel with an oscillating capacitor of a switching power supply circuit and the potential translational circuit is connected in parallel with the sampling resistor; the sampling branch circuit comprises a shut capacitor and a current transformer which are connected in series; the sampling resistor and the current transformer are connected in parallel; the potential translational circuit comprises a level isolating capacitor and a clamping diode, the cathode of the clamping diode and the level isolating capacitor are connected in series, and the anode of the clamping diode is grounded. Because the current sampling circuit is connected in parallel with a resonant capacitor, a current distribution relation is determined by a capacitance ratio of shunt capacitance to main circuit capacitance, and only very low current is available in the current sampling circuit, thereby the power loss of the current sampling circuit is greatly reduced. Furthermore, in the circuit, current detection of a heavy current circuit can be realized by using a small mutual inductor, thereby reducing the cost and the volume.
Description
Technical field
The present invention relates to adopt the switch power technology field of resonant zero technology, particularly a kind of current sampling circuit.
Background technology
Referring to Fig. 1, a kind of typical normal shock resonant zero (ZCS) circuit form in the switching power circuit in the prior art also can be reduced to the BUCK circuit form by normal shock.Wherein, inductance L e and capacitor C res are inductance and the electric capacity that produces vibration; The value of Le is smaller, so generally be that leakage inductance with transformer is as Le in the middle of the practice; For guaranteeing that oscillating characteristic is stable, Cres will use the high electric capacity of stability.In the prior art, current sampling circuit is connected in the main circuit usually, and promptly the frame of broken lines position is traditional common position of current sampling circuit among Fig. 1; Traditional current sampling circuit also can be connected on the Le in theory, but the sensibility reciprocal of instrument transformer itself can influence LC and vibrates in this moment current sampling circuit, does not adopt usually.
In the embodiment of the present invention process; The inventor finds that existing current sampling circuit is owing to be connected on the main circuit; The electric current of flowing through during work on the current sampling circuit is bigger; Make that not only the power loss of current sampling circuit is bigger, and selecting for use of instrument transformer in the current sampling circuit had relatively high expectations, cause the cost of the current sampling circuit in the existing Switching Power Supply higher.
Summary of the invention
The embodiment of the invention provides a kind of current sampling circuit, and the current sampling circuit power loss reaches the high problem of cost greatly in the existing resonant zero switching circuit to solve.
A kind of current sampling circuit comprises sampling slip, sample resistance (Ris) that the oscillating capacitance (Cres) with switching power circuit is in parallel and the current potential translation circuit that is in parallel with said sample resistance (Ris);
Said sampling slip comprises shunting capacitance (Cis) summation current transformer (Tis) that is in series; Said sample resistance (Ris) is connected in parallel with said current transformer (Tis) output limit;
Said current potential translation circuit comprises level isolation capacitance (Cg) and catching diode (Dg), and the negative electrode of said catching diode (Dg) and level isolation capacitance (Cg) are connected in series, the plus earth of catching diode (Dg);
Wherein, being connected in series of said level isolation capacitance (Cg) and catching diode (Dg) a little is the current output terminal of said current sampling circuit.
The input sideline circle number of turn of said current transformer (Tis) is less than the output sideline circle number of turn.
The input sideline circle of said current transformer (Tis) is connected with shunting capacitance (Cis);
The output limit one end ground connection of said current transformer (Tis), when Cis charged, an end and the primary current outflow end of output ground connection were end of the same name.
Said shunting capacitance (Cis) is selected the electric capacity with the identical material of oscillating capacitance (Cres) for use.
The electric capacity of said shunting capacitance (Cis) is less than the electric capacity of oscillating capacitance (Cres).
Current sampling circuit provided by the invention; Be connected in parallel on the resonant capacitance; Lean on the appearance value ratio decision electric current relations of distribution of shunting capacitance and main circuit electric capacity, thus have only very little electric current in the current sampling circuit, thus reduce the power loss of current sampling circuit greatly.And this circuit can select for use small-sized instrument transformer to realize the inspection stream of high-current circuit, thereby reduces cost and volume.
Description of drawings
In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art; To do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below; Obviously, the accompanying drawing in describing below only is some embodiments of the present invention, for those of ordinary skills; Under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.
Fig. 1 is a kind of typical normal shock resonant zero (ZCS) circuit theory diagrams in the prior art;
The current sampling circuit schematic diagram that Fig. 2 provides for the embodiment of the invention;
Fig. 3 is the ZCS circuit theory diagrams;
Fig. 4 is the corresponding relation figure that switching waveform and Le go up current waveform;
Fig. 5 is the oscillogram of voltage Vc and the electric current I c of oscillating capacitance Cres.
Embodiment
To combine the accompanying drawing in the embodiment of the invention below, the technical scheme in the embodiment of the invention is carried out clear, intactly description, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills are not making the every other embodiment that is obtained under the creative work prerequisite, all belong to the scope of the present invention's protection.
Referring to Fig. 2, the embodiment of the invention provides a kind of current sampling circuit, comprises sampling slip, sample resistance Ris that the oscillating capacitance Cres with switching power circuit is in parallel and the current potential translation circuit that is in parallel with said sample resistance Ris;
Said sampling slip comprises the shunting capacitance Cis summation current transformer Tis that is in series; Said sample resistance Ris and said current transformer Tis output limit are connected in parallel;
Said current potential translation circuit comprises level isolation capacitance Cg and catching diode Dg, and the negative electrode of said catching diode Dg and level isolation capacitance Cg are connected in series the plus earth of catching diode Dg;
Wherein, being connected in series of said level isolation capacitance Cg and catching diode Dg a little is the current output terminal of said current sampling circuit.
The current sampling circuit that provides for the clearer description embodiment of the invention, below introduce the current work principle on the vibration inductance L e of normal shock resonant zero ZCS circuit shown in Figure 3 down earlier in detail.
Wherein, vibration inductance L e and oscillating capacitance Cres are inductance and the electric capacity that produces vibration; The value of Le is smaller, so generally be that leakage inductance with transformer is as Le in the middle of the practice; For guaranteeing that oscillating characteristic is stable, Cres should select the high electric capacity of stability.
Suppose that transformer is an ideal transformer; Former limit inductance value is very big; This moment, exciting current was very little, can ignore exciting current, then the shape of the current waveform on primary current I1 and the inductance L e that vibrates be time phase identical; Just amplitude height has proportional difference, and this difference is the no-load voltage ratio of transformer.
Shown in Figure 4 is the corresponding relation that switching waveform and Le go up current waveform.For visualize goes out the effect of output current Io in circuit, what Fig. 4 used is the current waveform among the Le, and as previously mentioned, the electric current on primary current I1 and the Le is that amplitude height is variant, and shape and time phase concern just the same.Begin to be conducting in the time of t2 from switching tube K, because continued flow tube D2 is working, Cres is connected in parallel on the diode of a conducting, and voltage can't be participated in vibration, so at this time the time is that the transformer output voltage is to leakage inductance Le charging process by clamped; Be charged to output current Io constantly up to t2, this moment, continued flow tube D2 no longer provided electric current, and continued flow tube D2 turn-offs, Le and Cres starting oscillation; Electric current on the Le is the electric current that output current Io adds a LC vibration at this moment; T2 to t3 constantly; Vibration more than half cycle of passing through gets into negative half-cycle, and negative value reaches output current Io, the last overall current zero passage of Le; This moment, sample circuit detected nought state, and control circuit cuts off switching tube K.
Shown in Figure 5 is the voltage Vc of oscillating capacitance Cres in the said process and the waveform of electric current I c.At t0 constantly to t2, continued flow tube D2 conducting, Cres is starting oscillation not, has not both had voltage also not have electric current above.T2 is the starting oscillation process constantly, and Cres charge earlier and afterwards discharges in this process, and the Le electric current charges greater than Io the time, discharges in the time of less than Io, and the total current that assurance Le and Cres finally offer load is Io; Change a kind of saying, the electric current that Le flows through offers output Io exactly except offering Cres, so always differ an Io at LC duration of oscillation Ic and ILe.To t3 constantly, Le and primary current be zero passage simultaneously, and K switch is turn-offed; Also have voltage but Cres this moment goes up, offer output current Io so continue discharge, this moment, the Cres discharging current was constant Io; Put electricity up to t4 moment Cres, voltage is zero, and get into the continued flow tube D2 conducting period this moment.Can find out that if can fill an Io to Ic, then in the period of t2 to t4, the waveform of its waveform and Le is duplicate.
In the embodiment of the invention; Shunting capacitance that electric capacity is very little of parallel connection on Cres; Like this, discharge and recharge waveform and the Cres of little electric current goes up current waveform with shape on the shunting capacitance, and; Cres is the electric capacity that stability is high, and this electric current that has guaranteed that shunting capacitance is got does not receive the influence of factors such as time-temperature.As long as the electric current on the oscillating capacitance Cres is filled the corresponding part of Io, then can replace t2 and make current sampling to ILe and the I1 waveform of t4 period, thus the power loss and the cost of minimizing current sampling circuit, this is the basic ideas of invention.Need to prove, for Current Control, period of the firm conducting of switch and to turn-off the later period all be useless usually, the real acting time period be t2 to the t3 section, needed key parameter is peak value, zero crossing and (coming in handy) slope; T4 is after t3, so t2 has been comprised useful part fully to the sampling of period of t4.
In the current sampling circuit that the embodiment of the invention provides, comprise shunting capacitance Cis, current transformer Tis, sample resistance Ris, level isolation capacitance Cg, five devices of catching diode Dg.Tis is a current transformer, is equivalent to a pocket normal shock transformer, and the figure left part is divided into instrument transformer input limit, and the few operating current of the number of turn is big, and the figure right side is instrument transformer output limit, and it is little that number of turn multiplex (MUX) makes electric current.Cis is a shunting capacitance, is cascaded with the input limit of Tis, goes into sampling slip; In this series connection, Cis and Tis who last who down to circuit working less than influence.The sampling slip that this connects out, integral body is connected in parallel on the Cres.And resistance R is is connected in parallel on Tis output two ends, limit, is that sample resistance also plays the effect that demagnetization resets to Tis.In the time of the Cres oscillatory work, there is a signal Is ' on the output limit of Tis like this, and this signal can react the charging and discharging currents that flows through on the Cres.Note end of the same name, during the Cres charging, an end of the input limit inflow current of Tis, corresponding output limit end of the same name is signal Is '; And another termination of output limit is with reference to ground; This is exactly the ground of control circuit with reference to ground; Because current transformer itself plays buffer action, so no matter control circuit is in Switching Power Supply primary side or primary side, instrument transformer can be delivered to current signal on the corresponding ground reference.This Is ' also need be superimposed with the corresponding part of output current Io just can react primary current I1 and Le electric current I Le, adds that for this reason capacitor C g and diode Dg realize the level translation, become ultimate current signal Is to Is '.Cg one a termination Is ' termination Is, Dg anode connect with reference to ground, and negative electrode meets Is.
In the circuit working, in the time of the Cres oscillatory work, Cis can assign to the part electric current according to capacity, this minute the ratio of electric current be to come according to the capacity ratio, the current ratio that flows through Cres and Cis approximates their Capacity Ratio.Cis preferably select for use with Cres with material electric capacity, temperature influence such as is floated and can be cancelled each other like this; The capacity of Cis should be much smaller than Cres; Can be 1/tens or littler; This has a double purpose: the one, reduce the electric current that flows through current transformer Tis, and reduce power consumption and device cost, two because the effect of the input limit inductance value of Tis; The electric current that flows through Cis has a small amount of influence to circuit working, and electric current is little then little to the integrated circuit work influence.Ris has the effect of sampling, and the value lossy is big, and the conduction voltage drop of the too small then Dg of value is low to have more obviously influence to circuit, all can to hundreds of ohm with several ohm according to electric current is different.The last signal Is ' that obtains of Ris has reflected instrument transformer Tis input side electric current, and this is one has negative signal is just arranged, shunting capacitance Cis charging Is ' be on the occasion of, Cis discharge Is ' is a negative value.Cg and Dg are a kind of current potential translation circuit commonly used, and the current transformer output adopts electric capacity to isolate the rectifier system that adds diode clamping, can compensate out the DC component that circuit can't direct sample.Wherein, The capacity of Cg is bigger, utilizes the characteristic that voltage can not suddenly change on the electric capacity to transmit AC signal, is delivered to the Is end to the alternating current component among the Is '; And clamped electric capacity Dg guarantees that Is signal potential minimum is zero, can not go out negative value (factor of ignoring the diode current flow pressure drop).When Is ' is a negative value, because the effect of Dg is charged toward Cg right-hand member Is signal from reference ground; Making the Is signal is zero, and there is a voltage at the Cg two ends like this, and this voltage just in time is the corresponding signal value of output current Io; When Is ' be on the occasion of the time, Is be on the occasion of, Dg by; Is is that Is ' voltage adds the Cg voltage, because the Cg capacity is bigger, the characteristic that can not suddenly change according to voltage on the electric capacity is approximate thinks that the Cg voltage is constant; Can think whole sample time Is voltage be that Is ' voltage adds the Io counterpart, so Is can react the characteristic of I1 or ILe.
Through inventor's validation trial, can obtain following a series of preferred practical parameter: main circuit output current Io is 30A, and main capacitance Cres is the electric capacity of 0.88uF, and the resonance peak electric current can arrive 90A; Shunting capacitance Cis is with the electric capacity of the same material of 16.5nF, and current transformer Tis selects 1: 70 no-load voltage ratio for use, and Ris is 100ohm, and Cg is with 0.1uF conventional ceramic electric capacity, and Dg requires can be not really strict, and general-purpose diode gets final product.
It is thus clear that; The current sampling circuit that the embodiment of the invention provides; The current sampling circuit that provides is connected in parallel on the resonant capacitance, leans on the appearance value ratio decision electric current relations of distribution of shunting capacitance and main circuit electric capacity; So have only very little electric current in the current sampling circuit, thereby reduce the power loss of current sampling circuit greatly.And this circuit can select for use small-sized instrument transformer to realize the inspection stream of high-current circuit, thereby reduces cost and volume.
Need to prove; In this article; Term " comprises ", " comprising " or its any other variant are intended to contain comprising of nonexcludability; Thereby make to comprise that process, method, article or the equipment of a series of key elements not only comprise those key elements, but also comprise other key elements of clearly not listing, or also be included as this process, method, article or equipment intrinsic key element.Under the situation that do not having much more more restrictions, the key element that limits by statement " comprising ... ", and be not precluded within process, method, article or the equipment that comprises said key element and also have other identical element.
The present invention is not limited to above-mentioned execution mode, and the identical or akin product of other patents any and of the present invention that anyone draws under the enlightenment of patent of the present invention all drops within the protection range of patent of the present invention.
Claims (5)
1. a current sampling circuit is characterized in that, comprises sampling slip, sample resistance (Ris) that the oscillating capacitance (Cres) with the resonant zero switching power circuit is in parallel and the current potential translation circuit that is in parallel with said sample resistance (Ris);
Said sampling slip comprises shunting capacitance (Cis) summation current transformer (Tis) that is in series; Said sample resistance (Ris) is connected in parallel with said current transformer (Tis) output limit;
Said current potential translation circuit comprises level isolation capacitance (Cg) and catching diode (Dg), and the negative electrode of said catching diode (Dg) and level isolation capacitance (Cg) are connected in series, the plus earth of catching diode (Dg);
Wherein, being connected in series of said level isolation capacitance (Cg) and catching diode (Dg) a little is the current output terminal of said current sampling circuit.
2. current sampling circuit according to claim 1 is characterized in that, the input sideline circle number of turn of said current transformer (Tis) is less than the output sideline circle number of turn.
3. current sampling circuit according to claim 1 is characterized in that, the input limit end of the same name of said current transformer (Tis) is connected with shunting capacitance (Cis);
The output limit different name end ground connection of said current transformer (Tis).
4. current sampling circuit according to claim 1 is characterized in that, said shunting capacitance (Cis) is selected the electric capacity with the identical material of oscillating capacitance (Cres) for use.
5. current sampling circuit according to claim 1 is characterized in that, the electric capacity of said shunting capacitance (Cis) is less than the electric capacity of oscillating capacitance (Cres).
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| Application Number | Priority Date | Filing Date | Title |
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| CN2010101339236A CN101807857B (en) | 2010-03-29 | 2010-03-29 | Current sampling circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN2010101339236A CN101807857B (en) | 2010-03-29 | 2010-03-29 | Current sampling circuit |
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| CN101807857A CN101807857A (en) | 2010-08-18 |
| CN101807857B true CN101807857B (en) | 2012-08-08 |
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Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102904457B (en) * | 2012-08-29 | 2015-05-27 | 华为技术有限公司 | High-frequency switch power supply and high-frequency current detecting method |
| TWI505612B (en) * | 2013-08-23 | 2015-10-21 | Delta Electronics Inc | Sampling circuit for current transformer |
| CN104425120B (en) * | 2013-08-23 | 2016-07-06 | 台达电子工业股份有限公司 | Sample circuit for current transformer |
| CN103546048B (en) * | 2013-10-30 | 2018-03-06 | 华为技术有限公司 | Current sample method |
| CN105510681B (en) * | 2016-01-28 | 2018-08-24 | 南京交通职业技术学院 | A kind of non-linear current sampling assemble |
| CN108988651B (en) * | 2018-08-28 | 2022-03-08 | 西安交通大学 | Isolated current detection circuit and method for high-frequency resonant converter |
| CN113804945B (en) * | 2021-09-17 | 2022-07-12 | 西安交通大学 | Current detection circuit, detection method and control method for synchronous rectification in high-frequency LLC (logical Link control) |
| CN114995567B (en) * | 2022-06-20 | 2023-07-07 | 西安微电子技术研究所 | Slope compensation circuit of current control type |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0704958A1 (en) * | 1994-09-30 | 1996-04-03 | Sony Corporation | Switching power circuit |
| CN1249120A (en) * | 1997-02-25 | 2000-03-29 | 松下电器产业株式会社 | High frequency heating equipment |
| EP1152518A4 (en) * | 1999-12-09 | 2004-06-23 | Sanken Electric Co Ltd | Dc-dc converter |
| CN1829407A (en) * | 2005-02-28 | 2006-09-06 | Nec液晶技术株式会社 | Cold cathode tube lighting device and driving method and integrated circuit to be used in same |
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2010
- 2010-03-29 CN CN2010101339236A patent/CN101807857B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0704958A1 (en) * | 1994-09-30 | 1996-04-03 | Sony Corporation | Switching power circuit |
| CN1249120A (en) * | 1997-02-25 | 2000-03-29 | 松下电器产业株式会社 | High frequency heating equipment |
| EP1152518A4 (en) * | 1999-12-09 | 2004-06-23 | Sanken Electric Co Ltd | Dc-dc converter |
| CN1829407A (en) * | 2005-02-28 | 2006-09-06 | Nec液晶技术株式会社 | Cold cathode tube lighting device and driving method and integrated circuit to be used in same |
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| CN101807857A (en) | 2010-08-18 |
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