CN101667728A - Protection circuit for three-wire system current output transmitter - Google Patents
Protection circuit for three-wire system current output transmitter Download PDFInfo
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- CN101667728A CN101667728A CN200810120814A CN200810120814A CN101667728A CN 101667728 A CN101667728 A CN 101667728A CN 200810120814 A CN200810120814 A CN 200810120814A CN 200810120814 A CN200810120814 A CN 200810120814A CN 101667728 A CN101667728 A CN 101667728A
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Abstract
The invention provides a protection circuit for a three-wire system current output transmitter. The protection circuit comprises clamping diodes D1 and D2 and a diode D4, wherein the clamping diodes D1 and D2 are connected between a power end of a transmitter and a current output end and between the current output end and the ground GND in turn; and the diode D4 is connected between the power endand a transmitter terminal of a VCC end and used for preventing reverse connection of a power supply. The protection circuit is characterized by additionally comprising a P channel reinforced type small signal MOS pipe Q1, wherein a source electrode S of the pipe Q1 is connected to a current output end of a transmitter output stage, a grid electrode G of the pipe Q1 is connected to the ground GND,a drain electrode D serving as the transmitter terminal for the current output is connected with a diode D3 with an isolation function in series. The structure of the circuit is more reasonable and practical and can full protect the power supply and output lines.
Description
Technical field
The present invention relates to a kind of three-wire system current transmitter port protection circuit.
Background technology
The transmitter of electric current output type is widely used in the Industry Control scene, and its effect is the current signal that the signal of some transducer (generally being voltage signal) is amplified and converts to standard 4-20MA.The operation principle of the transmitter of this kind generally is to carry out voltage signal earlier to amplify, and carries out voltage to current conversion in output stage.Output stage generally is made of transistor or field effect transistor, and the practical application electrical schematic diagram is seen Fig. 1.
The protection mechanism of this circuit is as follows:
Diode D1 and D2 are clamp diodes, guarantee that the level of current output terminal is between GND-0.7V～VCC+0.7V, and the effect of diode D4 is to prevent the power supply reversal connection, and R1 is a current-limiting resistance.This circuit has following shortcoming:
1. introduce resistance R 1 in the circuit and do current limliting, resistance too conference influences load capacity, and too little current limitation effect is poor, because power ratio is bigger, corresponding volume is also bigger, is unfavorable for the miniaturization of product, so resistance R 1 usually need not.
2. work as power positive end and be connected on GND position among Fig. 1, power supply negative terminal is connected on VCC position among Fig. 1, signal end is connected on when IOUT holds among Fig. 1 (power supply reversal connection phenomenon), the current ratio of diode D2 and the resistance R 1 of flowing through this moment is bigger, if the detection resistance of load end is smaller simultaneously, then might cause diode D2 or load resistance to damage.
3. work as power positive end and be connected on GND position among Fig. 1, power supply negative terminal is connected on IOUT position among Fig. 1, and signal end is connected on when VCC holds among Fig. 1, is equivalent to power supply direct short-circuit (supposing the very little or not installation of resistance R 1 resistance) this moment, causes the damage of diode D2 overcurrent.
So there is unreasonable part in traditional protective circuit, requires further improvement.
Summary of the invention
Technical problem to be solved by this invention is exactly to provide the protection circuit for three-wire system current output transmitter that a kind of structure is more reasonable and practical, can carry out omnibearing protection to the power supply and the output line of transmitter at the present situation of above-mentioned prior art
The present invention solves the problems of the technologies described above the technical scheme that is adopted to be: a kind of protection circuit for three-wire system current output transmitter; it includes and is connected on transmitter power end and current output terminal; be connected with clamp diode D1 and D2 in turn between current output terminal and the ground GND; be connected with the diode D4 that prevents the power supply reversal connection between the transmitter terminals of power end and VCC end; it is characterized in that having in addition the small-signal metal-oxide-semiconductor Q1 of P-channel enhancement type; the source S of pipe Q1 is received the current output terminal of transmitter output stage; grid G ground connection GND, drain D and the transmitter terminals as electric current output are in series with the diode D3 of buffer action.
As improvement, described small-signal metal-oxide-semiconductor Q1 selects the pipe of SOT-23 encapsulation for use, so that the replacement current-limiting resistance to be arranged, has reduced the wiring board area.
As improvement, described diode D3 selects the Schottky diode of withstand voltage greater than the circuit voltage value for use, and it is very little to the load capacity influence of electric current output.
At last, described diode D3 is under the enough conditions of load capacity surplus, and diode D3 also can select common rectification type diode for use, to reduce cost.
The invention has the advantages that:
1 adopts small-signal metal-oxide-semiconductor such as SOT-23 encapsulation to replace current-limiting resistance, has reduced the wiring board area;
2 when the power supply reversal connection, V
GS=0, pipe Q1 is in cut-off state, and the safety of transmitter and power supply has been protected in no current loop in the circuit;
3 work as power positive end is connected on the GND position, and power supply negative terminal is connected on the IOUT position, when signal end is connected on the VCC end, and V
GS＞=0, pipe Q1 is in cut-off state equally, and no current loop in the circuit is so protected the safety of transmitter and power supply;
Therefore circuit is more reasonable and practical, can carry out omnibearing protection to the power supply and the output line of transmitter.
Description of drawings
Fig. 1 is traditional circuit diagram;
Fig. 2 is the circuit diagram of the present invention after improving.
Embodiment
Embodiment describes in further detail the present invention below in conjunction with accompanying drawing.
At above-mentioned deficiency, the present invention can carry out omnibearing protection to the power supply and the output line of transmitter, and the principle sketch is seen Fig. 2.
In the technical scheme of the present invention; a kind of protection circuit for three-wire system current output transmitter; it includes and is connected on transmitter power end and current output terminal; be connected with clamp diode D1 and D2 in turn between current output terminal and the ground GND; be connected with the diode D4 that prevents the power supply reversal connection between the transmitter terminals of power end and VCC end; the crucial part of its invention is current-limiting resistance is removed; change the small-signal metal-oxide-semiconductor Q1 of P-channel enhancement type into; the source S of pipe Q1 is received the output of transmitter output stage; grid G ground connection, drain D and transmitter terminals are in series with isolating diode D3.During operate as normal, V
GS＜=-2V, pipe Q1 is in conducting state, 4-20mA electric current flowing pipe Q1 and diode D3, because the conducting resistance very little (can be lower than 1 Ω) of pipe Q1, diode D3 selects Schottky diode for use, and is very little to the load capacity influence of electric current output.
Element is selected for use: in this circuit, selection of components leeway is very big, when selecting metal-oxide-semiconductor, selects cut-in voltage (V for use as far as possible
GS) low, the device that conducting resistance is low, I
DSElectric current gets final product greater than 200mA, and is enough as the load capacity surplus, and diode D3 can also select common rectification type diode for use, as 1N4000 series.When noting selecting Schottky diode for use, its withstand voltage can not be lower than the operational voltage value of circuit, as the 24V system, guarantee more than the withstand voltage 30V.
The advantage of this circuit is as follows:
1 adopts small-signal metal-oxide-semiconductor (SOT-23 encapsulation) to replace current-limiting resistance, has reduced the wiring board area.
2 when the power supply reversal connection, V
GS＜0, metal-oxide-semiconductor Q1 is in cut-off state, and the safety of transmitter and power supply has been protected in no current loop in the circuit.
3 work as power positive end is connected on GND position among Fig. 2, and power supply negative terminal is connected on IOUT position among Fig. 2, and signal end is connected on when VCC holds among Fig. 2, V
GS＜0, metal-oxide-semiconductor Q1 is in cut-off state equally, and no current loop in the circuit is so protected the safety of transmitter and power supply.
Claims (4)
1, a kind of protection circuit for three-wire system current output transmitter; it includes to be connected between transmitter power end and current output terminal, current output terminal and the ground GND and is connected with clamp diode D1 and D2 in turn; be connected with the diode D4 that prevents the power supply reversal connection between the transmitter terminals of power end and VCC end; it is characterized in that having in addition the small-signal metal-oxide-semiconductor Q1 of P-channel enhancement type; the source S of pipe Q1 is received the current output terminal of transmitter output stage; grid G ground connection GND, drain D and the transmitter terminals as electric current output are in series with the diode D3 of buffer action.
2, protection circuit for three-wire system current output transmitter according to claim 1 is characterized in that described small-signal metal-oxide-semiconductor Q1 selects the pipe of SOT-23 encapsulation for use.
3, protection circuit for three-wire system current output transmitter according to claim 1 is characterized in that described diode D3 selects the Schottky diode of withstand voltage greater than the circuit voltage value for use.
4, protection circuit for three-wire system current output transmitter according to claim 1 is characterized in that described diode D3 under the enough conditions of load capacity surplus, and diode D3 selects common rectification type diode for use.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008101208143A CN101667728B (en) | 2008-09-05 | 2008-09-05 | Protection circuit for three-wire system current output transmitter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008101208143A CN101667728B (en) | 2008-09-05 | 2008-09-05 | Protection circuit for three-wire system current output transmitter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101667728A true CN101667728A (en) | 2010-03-10 |
| CN101667728B CN101667728B (en) | 2012-01-11 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2008101208143A Expired - Fee Related CN101667728B (en) | 2008-09-05 | 2008-09-05 | Protection circuit for three-wire system current output transmitter |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104714587A (en) * | 2015-01-05 | 2015-06-17 | 湖南工业大学 | Device for obtaining transmitter current average value |
| CN106532677A (en) * | 2017-01-05 | 2017-03-22 | 科蒂斯技术（苏州）有限公司 | DC input reverse connection preventing circuit based on N-MOSFET |
| CN107589293A (en) * | 2017-09-11 | 2018-01-16 | 珠海格力节能环保制冷技术研究中心有限公司 | A kind of current sampling circuit |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2242534Y (en) * | 1995-05-15 | 1996-12-11 | 加维股份有限公司 | Light chopper with protection function |
| US6611410B1 (en) * | 1999-12-17 | 2003-08-26 | Siemens Vdo Automotive Inc. | Positive supply lead reverse polarity protection circuit |
| TW490907B (en) * | 2000-11-14 | 2002-06-11 | Silicon Touch Tech Inc | Circuit with protection for inverted connection of power source polarity |
| CN2836301Y (en) * | 2005-08-28 | 2006-11-08 | 华为技术有限公司 | Reverse connection prevention circuit for power supply |
| CN201256291Y (en) * | 2008-09-05 | 2009-06-10 | 宁波柯力电气制造有限公司 | Three-wire type current output transmitter protection circuit |
-
2008
- 2008-09-05 CN CN2008101208143A patent/CN101667728B/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104714587A (en) * | 2015-01-05 | 2015-06-17 | 湖南工业大学 | Device for obtaining transmitter current average value |
| CN104714587B (en) * | 2015-01-05 | 2016-11-23 | 湖南工业大学 | A kind of device seeking transmitter current average |
| CN106532677A (en) * | 2017-01-05 | 2017-03-22 | 科蒂斯技术（苏州）有限公司 | DC input reverse connection preventing circuit based on N-MOSFET |
| CN107589293A (en) * | 2017-09-11 | 2018-01-16 | 珠海格力节能环保制冷技术研究中心有限公司 | A kind of current sampling circuit |
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| Publication number | Publication date |
|---|---|
| CN101667728B (en) | 2012-01-11 |
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| C56 | Change in the name or address of the patentee |
Owner name: NINGBO KELI SENSING TECHNOLOGY CO., LTD. Free format text: FORMER NAME: NINGBO KELI ELECTRIC MANUFACTURING CO., LTD. |
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| CP01 | Change in the name or title of a patent holder |
Address after: 315033 Changxin, Zhejiang Province Investment Venture Park, Jiangbei District, C Road, No., No. 199 Patentee after: KELI SENSING TECHNOLOGY (NINGBO) Co.,Ltd. Address before: 315033 Changxin, Zhejiang Province Investment Venture Park, Jiangbei District, C Road, No., No. 199 Patentee before: Ningbo Keli Electric Manufacturing Co.,Ltd. |
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| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20120111 |