CN101860001B - Switch power supply current detection circuit - Google Patents
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- CN101860001B CN101860001B CN2010101644120A CN201010164412A CN101860001B CN 101860001 B CN101860001 B CN 101860001B CN 2010101644120 A CN2010101644120 A CN 2010101644120A CN 201010164412 A CN201010164412 A CN 201010164412A CN 101860001 B CN101860001 B CN 101860001B
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Abstract
The invention discloses a switch power supply current detection circuit, comprising a switch device used for switching a current signal to a voltage signal, which is connected with a current loop to be detected; a current isolation detection circuit which is connected with two ends of the switch device, and the output end is used for outputting a current detection signal; and a fast overcurrent isolation detection circuit is used for outputting and comparing circuit overcurrent detection signals in time and providing the circuit with fast overcurrent protection, which is connected with two ends of the switch device. The invention has the advantages of simple structure and low cost, and can effectively solve electric isolation problem of analog signals and sampling control systems.
Description
Technical field
The present invention relates to a kind of current detection circuit; Be used for high frequency switch power field current detecting, can import, export and the pwm converter electric current by the sense switch power supply, precision is high; And realized electrical isolation; Have good linearty and bandwidth, and when the detection electric current was used for current-limiting protection, response speed can be guaranteed.
Background technology
The overall development trend of Switching Power Supply is that the switch operating frequency is increasingly high, thereby the real-time of current detecting is also required increasingly high, and cost receives much concern very much.Traditional current detection technology mainly is divided into based on the detection scheme in magnetic field with based on the detection scheme of shunt; With current transformer (Fig. 1) and Hall element (Fig. 2) be representative based on the detection scheme in magnetic field owing to have good isolation and lower advantages such as power loss adopt widely; Especially exchanging and big electric current application; But it is bigger that its shortcoming is a volume, and compensation characteristic, the linearity and temperature characterisitic are undesirable, and cost is higher.
Current transformer adopts transformer electromagnetic isolation principle, and general former limit has less number of turn N1, and secondary has more number of turn N2.The former edge joint measured current I of instrument transformer, secondary for the output current I_OUT after detecting, are voltage signal through resistance R with current conversion then then, have realized the electrical isolation on former and deputy limit through magnetic induction way.
The conversion proportionate relationship is:
I_OUT/I＝N1/N2
Owing to adopt current transformer to isolate, there is the problem of LF-response bandwidth, because all there is magnetizing inductance in real transformer, when the low transformer responsive bandwidth that arrives of frequency of sensed current, instrument transformer will lose the current detecting ability.And many times all need detect direct current in the high frequency switch power, current transformer can't satisfy this requirement.
Hall element utilizes Hall effect, detects output Hall voltage signal behind the magnetic flux with the proportional relation of primary current through assembling magnetic circuit, after amplifying circuit amplifies, is transformed to proportional curtage signal, intuitively reflects the size of electric current.
At present generally with Hall element, gather magnetic circuit and amplifying circuit integrates, use as Hall element, can realize the isolation detection of direct current, alternating current, do not have the LF-response bandwidth problem.But there are the temperature drift in Hall element and amplifying circuit, have the frequency response upper limit, are generally tens of or hundreds of kHz, and cost has limited the application in Switching Power Supply also than higher simultaneously.
The linearity of the current detecting buffer circuit (Fig. 3) that the application linear optical coupling is formed is good, and circuit is simple, can detect direct current, has solved the electrical isolation problem of analog signal and sampling control system effectively, and precision is high, cost is low.
But a time-delay that remarkable shortcoming is exactly a current detecting of linear optical coupling, because the bandwidth of linear optical coupling is generally below tens of kHz, time-delay is more than the number microseconds.And in high frequency switch power, current detection circuit also needs and can fast detecting arrive the overcurrent fault except the amplitude that detects electric current; The drive signal of timely powered-down; The restriction electric current further rises, if over-current detection is untimely, will cause electric current to surpass the upper limit of permission.Along with the development of Switching Power Supply, switching frequency is increasingly high, and this problem is also more and more outstanding.
Fig. 4 explains Switching Power Supply current-limiting protection principle with a kind of PWM power converting circuit with the wave limiting function.Pwm control signal is that one-period is T, the square wave that duty ratio (D) 0～1 changes, and trigger flows to switch S at the rising edge in each cycle with pwm control signal, makes the S conducting, makes input voltage Vi be transformed to output voltage V o, and both sides relation is:
Vo/Vi＝D
In circuit, also be provided with current detection circuit, be used for detecting the output overcurrent, when electric current surpasses capping; Comparator toggles makes trigger reset, and the S drive signal is blocked; Begin and over-current signal disappears and just can lift a blockade up to next cycle, so just realized by the ripple overcurrent protection.This shows that switching frequency is high more, the cycle is short more, then requires over-current detection rapid more, makes electric current excessive otherwise can cause overcurrent in time not detect, and over-current signal can not in time be removed and blockade can not in time be removed.These two problems all can influence the high frequency switch power operate as normal.The mains switch frequency has reached hundreds of kHz at present, even number MHz, and the operating lag of linear optical coupling is generally all being counted more than the us, obviously can not satisfy the demand of quick protection.
Fig. 5 has shown the influence of over-current detection time-delay to circuit working.When applying drive signal to switch S, switch conduction, the output current waveform with sawtooth waveforms under the effect of inductance L rises, and the current peak expression formula is:
I＝Vi*D/R+(Vi-Vo)*D*T/2L
It is thus clear that duty ratio is more little, then current peak is also more little.If set a upper current limit, when surpassing, electric current in time blocks pwm control signal on this in limited time, can guarantee that then electric current is no more than capping all the time.
But all there is time-delay (Δ t) in the actual current testing circuit; Detected electric current is consistent with the actual current waveform, but phase place has hysteresis, when this just causes actual current to reach capping; The electric current of testing circuit does not also reach the upper limit; Time-delay just can reach afterwards through Δ t again, thereby produces overcurrent, and the overcurrent amplitude is:
ΔI＝(Vi-Vo)*Δt/L
It is thus clear that it is big more to delay time, then overcurrent is also serious more.
On the other hand, detect time-delay and make over-current signal remove also appearance hysteresis, when next cycle began, the overcurrent locking signal might be able to not in time be removed, and causes drive signal to lose one-period.More than two phenomenons be the main harm of time-delay, therefore in design, require the overcurrent protection signal lag than more than the little one magnitude of switch periods.When the mains switch frequency reaches 100kHz when above, require for linear optical coupling, obviously can not meet the demands less than 1uS.
So the current signal that adopts linear optocoupler to detect is inappropriate for and is used as high frequency switch power overcurrent protection signal.
Do following the summary to above electric current isolation detection mode characteristics:
It is thus clear that; More than several kinds of traditional electric current isolation detection schemes all have defective; Especially in the high frequency switch power field, higher to the real-time requirement of overcurrent protection, the problem that the present invention mainly solves; Be exactly simultaneously in the linear isolation detection of the high accuracy that realizes ac and dc current, can the fast detecting overcurrent fault.
Summary of the invention
The object of the invention can be realized the current signal isolation detection for providing a kind of, simultaneously quick current-limiting protection signal can be provided in time, and the low switch power supply current detection circuit of cost.
The technical scheme that realizes above-mentioned purpose is following:
Switch power supply current detection circuit comprises:
Current signal converts the voltage signal device to, is connected to the sensed current loop;
The electric current isolation detection circuit, the two ends that convert the voltage signal device with current signal to are connected, its output output current detection signal;
Quick overcurrent isolation detection circuit, the two ends that convert the voltage signal device with current signal to are connected, and in time the output overcurrent detection signal is used for quick overcurrent protection to circuit being provided.
It is shunt that said current signal converts the voltage signal device to.
Said quick overcurrent isolation detection circuit comprises and is connected in the comparison process circuit that current signal converts voltage signal device two ends to; Its electric current that directly utilizes current signal to convert voltage signal device two ends to changes voltage signal and benchmark is relatively exported, and also comprises the over-current detection and the rapid light coupling buffer circuit that are connected with the comparison process circuit.
Said electric current isolation detection circuit comprises two ends linear optical coupling translation circuit that is connected and the amplifier translation circuit that is connected with the linear optical coupling translation circuit that converts the voltage signal device with current signal to.
The present invention mainly adopts a current signal to convert voltage signal device string in the corresponding current circuit that will detect; Send into pwm control circuit the corresponding interface through electric current isolation detection circuit realization current detecting isolation output and carry out FEEDBACK CONTROL; The linearity of the analog signal buffer circuit of its composition is good; Solved the electrical isolation problem of analog signal and sampling control system effectively, and precision is high, cost is low.
Detect the excessive shortcoming of time-delay in order to overcome linear optical coupling; The present invention does not adopt the current detection signal of linear optical coupling to be used for current-limiting protection; But being provided with the overcurrent isolation detection circuit specially, the electric current that directly adopts current signal to convert on the voltage signal device changes voltage signal, in time exports comparison circuit over-current detection signal; Send the blockade drive pulse signal, the protection switch power device.It is thus clear that in above-mentioned overcurrent isolation detection circuit, time-delay even below tens of nS, is enough to satisfy the demand of high frequency switch power generally all below hundreds of nS.
Description of drawings
Fig. 1 carries out the schematic diagram of current detecting for Current Transformer;
Fig. 2 is for carrying out the schematic diagram of current detecting with Hall element;
Fig. 3 uses the current detecting buffer circuit that linear optical coupling is formed;
Fig. 4 is with a kind of PWM power converting circuit schematic diagram with the wave limiting function;
Fig. 5 has shown the oscillogram of over-current detection time-delay to the circuit working influence;
Fig. 6 is a structured flowchart of the present invention;
Fig. 7 is applied to the schematic diagram of physical circuit for the present invention;
Fig. 8 is the electrical schematic diagram of a specific embodiment of the present invention.
Embodiment
Below in conjunction with accompanying drawing and specific embodiment the present invention is described further.
As shown in Figure 6, switch power supply current detection circuit comprises:
Current signal converts the voltage signal device to, is connected to the sensed current loop;
The electric current isolation detection circuit, the two ends that convert the voltage signal device with current signal to are connected, its output output current detection signal;
Quick overcurrent isolation detection circuit, the two ends that convert the voltage signal device with current signal to are connected, and in time export comparison circuit over-current detection signal, are used for quick overcurrent protection to circuit being provided.
As shown in Figure 8, switch power supply current detection circuit comprises:
Shunt is connected to the sensed current loop;
The linear light lotus root translation circuit and the amplifier translation circuit that is connected with linear light lotus root translation circuit, output current detection signal that link to each other with the shunt two ends;
The comparison process circuit is connected in the two ends of shunt, directly utilizes the electric current at shunt two ends to change voltage signal and benchmark is relatively exported; Over-current detection that is connected with the comparison process circuit and rapid light coupling buffer circuit are in time exported comparison circuit over-current detection signal, are used for quick overcurrent protection to circuit being provided.
Fig. 8 is the circuit of the present invention program's specific embodiment, and one the tunnel adopts linear optical coupling to detect electric current is used for detecting, controlling; Another road is used for overcurrent protection, when the current signal of shunt sampling during greater than reference voltage V ref, and the comparator output switching activity; Corresponding optocoupler output state flip; The output protection signal sends the blockade driving pulse fast, has overcome the long time-delay of time of linear optical coupling; Strong protection device for power switching ensures the releasing in time of overcurrent letter simultaneously and blockade can be removed fast.
This embodiment mainly adopts a shunt string in the corresponding current circuit that will detect, and sends into pwm control circuit the corresponding interface through linear optical coupling realization current detecting isolation output and carries out FEEDBACK CONTROL.The linearity of the analog signal buffer circuit that the application linear optocoupler is formed is good, has solved the electrical isolation problem of analog signal and sampling control system effectively, and precision is high, cost is low.
Detect the excessive shortcoming of time-delay in order to overcome linear optical coupling, the present invention does not adopt the current detection signal of linear optical coupling to be used for current-limiting protection, but is provided with overcurrent isolation detection passage specially; Directly adopt the electric current on the shunt to change voltage signal, through the output of overcurrent comparator treatment circuit, after reaching the current limitation set point; The comparator output switching activity, corresponding optocoupler output state flip, in time output protection signal; Send the blockade drive pulse signal, the protection switch power device.It is thus clear that in above-mentioned overcurrent isolation detection passage, time-delay mainly appears at the comparator treatment circuit and isolates optocoupler.Because the high speed photo coupling that adopts Digital Transmission to use though can not realize the linear isolation detection of electric current, can be realized the quick transmission of switches digital, time-delay even below tens of nS, is enough to satisfy the demand of high frequency switch power generally all below hundreds of nS.
The innovation part of this partial circuit; Mainly overcome the detection time-delay of linear optical coupling; Guaranteeing that overcurrent occurs to blocks the driving pulse time and should lack (too big delay can make current-limiting points go beyond the scope) as far as possible; Adopt optocoupler to realize power side and data side isolation output simultaneously, and cost is lower, the part that can replace Hall element is used.
Fig. 7 is the concrete application of the present invention program in side circuit; Passage one adopts linear optical coupling detection electric current to be used for the PWM FEEDBACK CONTROL; Passage two adopts the electric current on the shunt to change voltage signal, through the output of overcurrent comparator treatment circuit, in time output protection signal; Send the blockade drive pulse signal, protection switch power device (S).
Claims (2)
1. switch power supply current detection circuit is characterized in that, comprising:
Current signal converts the voltage signal device to, is connected to the sensed current loop;
The electric current isolation detection circuit, the two ends that convert the voltage signal device with current signal to are connected, its output output current detection signal;
Quick overcurrent isolation detection circuit, the two ends that convert the voltage signal device with current signal to are connected, and in time the output overcurrent detection signal is used for quick overcurrent protection to circuit being provided;
Wherein, to convert the voltage signal device to be shunt to said current signal;
Said quick overcurrent isolation detection circuit comprises and is connected in the comparison process circuit that current signal converts voltage signal device two ends to; Its electric current that directly utilizes current signal to convert voltage signal device two ends to changes voltage signal and reference voltage compares output, also comprises the over-current detection and the rapid light coupling buffer circuit that are connected with the comparison process circuit.
2. switch power supply current detection circuit according to claim 1; It is characterized in that said electric current isolation detection circuit comprises two ends linear optical coupling translation circuit that is connected and the amplifier translation circuit that is connected with the linear optical coupling translation circuit that converts the voltage signal device with current signal to.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2010101644120A CN101860001B (en) | 2010-05-06 | 2010-05-06 | Switch power supply current detection circuit |
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| CN2010101644120A CN101860001B (en) | 2010-05-06 | 2010-05-06 | Switch power supply current detection circuit |
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| CN101860001A CN101860001A (en) | 2010-10-13 |
| CN101860001B true CN101860001B (en) | 2012-11-28 |
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Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102664621B (en) * | 2012-05-25 | 2014-08-13 | 长园深瑞继保自动化有限公司 | Isolation method and circuit for signal acquisition of electronic mutual inductor |
| DE102012218773A1 (en) * | 2012-10-15 | 2014-04-17 | Continental Automotive Gmbh | Method and device for measuring a current through a switch |
| CN103219705B (en) | 2013-03-12 | 2016-02-24 | 中兴通讯股份有限公司 | The short-circuit protection method of half bridge resonant transformer and device |
| CN105929220A (en) * | 2016-04-19 | 2016-09-07 | 南京埃斯顿自动化股份有限公司 | Over-current detection circuit |
| CN106451700B (en) * | 2016-10-26 | 2018-12-25 | 中惠创智无线供电技术有限公司 | A kind of circuit protection device and wireless charging system |
| CN108303581B (en) * | 2018-02-01 | 2020-05-22 | 深圳市华星光电技术有限公司 | GOA circuit and GOA circuit overcurrent protection detection method |
| CN108444515B (en) * | 2018-03-14 | 2024-10-01 | 杭州思泰微电子有限公司 | Rapid threshold-crossing detection circuit applied to switch modulation signal |
| CN110007134A (en) * | 2019-04-29 | 2019-07-12 | 郑州铁路职业技术学院 | A DC high current metering device |
| CN110492441B (en) * | 2019-08-20 | 2021-12-31 | 大连海事大学 | DC/DC converter configured with fault detection circuit and fault detection method |
| CN110824231A (en) * | 2019-11-28 | 2020-02-21 | 南京汇凯顺电子科技有限公司 | Sampling circuit and sampling method for high-voltage direct current voltage and current |
| CN111638391A (en) * | 2020-07-03 | 2020-09-08 | 杭州普安科技有限公司 | Three-phase protection circuit for passive secondary circuit inspection source |
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| CN1848577A (en) * | 2005-06-17 | 2006-10-18 | 华为技术有限公司 | Overcurrent protection circuit |
| CN201252491Y (en) * | 2008-07-18 | 2009-06-03 | 王镇 | Overvoltage and overcurrent protecting circuit of a module power supply |
| CN101661057A (en) * | 2009-09-27 | 2010-03-03 | 哈尔滨理工大学 | Device for implementing power measurement based on resistance sampling by linear optocoupler |
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2010
- 2010-05-06 CN CN2010101644120A patent/CN101860001B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1848577A (en) * | 2005-06-17 | 2006-10-18 | 华为技术有限公司 | Overcurrent protection circuit |
| CN201252491Y (en) * | 2008-07-18 | 2009-06-03 | 王镇 | Overvoltage and overcurrent protecting circuit of a module power supply |
| CN101661057A (en) * | 2009-09-27 | 2010-03-03 | 哈尔滨理工大学 | Device for implementing power measurement based on resistance sampling by linear optocoupler |
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Address after: 100070 Building 2, zone 18, No. 188, West nansihuan Road, Fengtai District, Beijing (Park) Patentee after: Beijing Dinghan Technology Group Co., Ltd. Address before: 100070, No. 3, No. seven, No. 188, South Fourth Ring Road, Beijing, Fengtai District Patentee before: Beijing Dinghan Technology Co., Ltd. |