CN101592517B - Protection circuit of excitation power supply of weighing sensor - Google Patents
Protection circuit of excitation power supply of weighing sensor Download PDFInfo
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- CN101592517B CN101592517B CN200810038266XA CN200810038266A CN101592517B CN 101592517 B CN101592517 B CN 101592517B CN 200810038266X A CN200810038266X A CN 200810038266XA CN 200810038266 A CN200810038266 A CN 200810038266A CN 101592517 B CN101592517 B CN 101592517B
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Abstract
The invention discloses a protection circuit of an excitation power supply of a weighing sensor. The protection circuit is characterized in that an input terminal of an alternating current exciting circuit is connected with an output terminal of an alternating current excitation driving circuit, a first input terminal of the alternating current excitation driving circuit is connected with the protection circuit, a second input terminal of the alternating current excitation driving circuit is connected with an output terminal of an overcurrent protection circuit, a first input terminal of the overcurrent protection circuit is connected with an output terminal of a restart circuit, an input terminal of the restart circuit is connected with an input terminal of a monolithic processor circuit interface, and a second input terminal of the overcurrent protection circuit is connected with the second output terminal of the alternating current exciting circuit. The invention realizes the reliable protection of the alternating current excitation power supply of the sensor and avoids the instrument damage due to the external fault; and the restart circuit provides the possibility that the system automatically restores to work under the condition of instantaneous failure of the external circuit so that the system is more stable.
Description
Technical field
The present invention relates to circuit field, be specifically related to a kind of holding circuit of excitation power supply of weighing sensor.
Background technology
The analog to digital conversion of Weighing indicator partly adopts the AD7730 integrated circuit of ADI company, and it can adopt ac-excited power drives LOAD CELLS.ADI company has provided ac-excited reference circuit, and as shown in Figure 1, the weak point of this circuit is that several field effect transistor Q3～Q6 will burn in moment when causing the excitation power supply short circuit when sensor connection error or because of other accident.
Summary of the invention
The object of the present invention is to provide a kind of holding circuit of reliable and stable excitation power supply of weighing sensor.
To achieve these goals; technical scheme of the present invention is as follows: a kind of holding circuit of excitation power supply of weighing sensor; comprise analog to digital conversion circuit; the output terminal of LOAD CELLS is connected with the analog input end of this analog to digital conversion circuit; the digital output end of this analog to digital conversion circuit is connected with the interface microcontroller circuit; the input end of LOAD CELLS is connected with first output terminal of ac driven circuit; the input end that it is characterized in that ac driven circuit is connected with the output terminal of ac-excited driving circuit; the first input end of this ac-excited driving circuit is connected with analog to digital conversion circuit; second input end of this ac-excited driving circuit is connected with the output terminal of current foldback circuit; the first input end of this current foldback circuit is connected with the output terminal that restarts circuit; the input end that restarts circuit is connected with the input end of single chip circuit interface; second input end of current foldback circuit is connected with second output terminal of ac driven circuit; wherein ac driven circuit comprises first field effect transistor and second field effect transistor that is connected in series; the 3rd field effect transistor that is connected in series and the 4th field effect transistor; ac-excited driving circuit comprises first Sheffer stroke gate and the 3rd Sheffer stroke gate that is connected in parallel; an input end of first Sheffer stroke gate is connected with the output terminal of analog to digital conversion circuit; another input end of first Sheffer stroke gate is connected with the output terminal of current foldback circuit; the output terminal of first Sheffer stroke gate is connected with the control end of first field effect transistor; an input end of the 3rd Sheffer stroke gate is connected with the output terminal of analog to digital conversion circuit; another input end of the 3rd Sheffer stroke gate is connected with the output terminal of current foldback circuit, and the output terminal of the 3rd Sheffer stroke gate is connected with the control end of the 4th field effect transistor.
The present invention adopts current foldback circuit that the output of ac driven circuit is carried out feeding back to ac-excited driving circuit after the sampling processing, thereby realizes the reliably protecting to the ac-excited power supply of sensor, and the instrument of having avoided causing because of external fault is damaged.Restarting circuit provides externally under the situation of circuit transient fault, and the possibility that system resumes work automatically makes system more stable.
Description of drawings
Fig. 1 is the circuit diagram of prior art
Fig. 2 is a block diagram of the present invention
Fig. 3 is the circuit diagram of one embodiment of the invention
Embodiment
Below in conjunction with drawings and Examples the present invention is elaborated.
A kind of holding circuit of excitation power supply of weighing sensor among Fig. 2; comprise analog to digital conversion circuit 2; the output terminal of LOAD CELLS 1 is connected with the analog input end of this analog to digital conversion circuit 2; the digital output end of this analog to digital conversion circuit 2 and other port that is connected with single-chip microcomputer all are connected with interface microcontroller circuit 7; the input end of LOAD CELLS 1 is connected with first output terminal of ac driven circuit 3; the output terminal of analog to digital conversion circuit 2 is connected with the first input end of ac-excited driving circuit 4; the input end that it is characterized in that ac driven circuit 3 is connected with the output terminal of ac-excited driving circuit 4; second input end of this ac-excited driving circuit 4 is connected with the output terminal of current foldback circuit 5; the first input end of this current foldback circuit 5 is connected with the output terminal that restarts circuit 6; the input end that restarts circuit 6 is connected with the input end of single chip circuit interface 7, and the input end of current foldback circuit 5 is connected with second output terminal of ac driven circuit 3.
As shown in Figure 3; ac driven circuit 3 is: the source electrode of the first field effect transistor Q5 is connected with power supply; the drain electrode of the first field effect transistor Q5 is connected with the drain electrode of the second field effect transistor Q6; the source electrode of the second field effect transistor Q6 is connected with the input end of current foldback circuit 5; the source electrode of the 3rd field effect transistor Q4 is connected with power supply; the drain electrode of the 3rd field effect transistor Q4 is connected with the drain electrode of the 4th field effect transistor Q3; the source electrode of the 4th field effect transistor is connected with the input end of current foldback circuit 5; the junction of the first field effect transistor Q5 and the second field effect transistor Q6 is an output terminal of excitation power supply; be connected with an input end of LOAD CELLS 1; the junction of the 3rd field effect transistor Q4 and the 4th field effect transistor Q3 is another output terminal of excitation power supply; be connected with another input end of LOAD CELLS 1, the grid of these four field effect transistor is connected with ac-excited driving circuit 4.
The circuit of ac-excited driving circuit 4 is: the input end of the first Sheffer stroke gate U7A is connected with the ACX end of analog to digital conversion circuit 2; another input end of the first Sheffer stroke gate U7A is connected with the output terminal of current foldback circuit 5; the output terminal of the first Sheffer stroke gate U7A is connected with the grid of the first field effect transistor Q5; the second Sheffer stroke gate U7B and the first Sheffer stroke gate U7A are connected in parallel, the input end of the 3rd Sheffer stroke gate U7C and analog to digital conversion circuit 2
End connects; another input end of the 3rd Sheffer stroke gate U7C is connected with the output terminal of current foldback circuit 5; the output terminal of the 3rd Sheffer stroke gate U7C is connected with the grid of the 3rd field effect transistor Q4; the 4th Sheffer stroke gate U7D and the 3rd Sheffer stroke gate U7C are connected in parallel; the grid of the 4th field effect transistor Q3 is connected with the ACX end of analog to digital conversion circuit 2, the grid of the second field effect transistor Q6 and analog to digital conversion circuit 2
End connects.In this embodiment, the first Sheffer stroke gate U7A is in parallel with the second Sheffer stroke gate U7B to improve driving force, and the first Sheffer stroke gate U7C is in parallel with the second Sheffer stroke gate U7D to improve driving force.
The circuit of current foldback circuit 5 is: the input end of this current foldback circuit 5 is the end with sampling resistor R35; the other end ground connection of sampling resistor R35; the input end of this current foldback circuit 5 also is connected with an end of second resistance R 36; the other end of second resistance R 36 is connected with the positive input terminal of the first comparer U5B; the positive input terminal of the first comparer U5B is also by capacitor C 36 ground connection; the negative input end of the first comparer U5B connects power supply by the 3rd resistance R 44; the negative input end of the first comparer U5B is simultaneously by the 4th resistance R 45 ground connection; the negative input end of the first comparer U5B also connects power supply by capacitor C 34 and the resistance R 43 that is connected in series; be connected with feedback resistance R41 between the positive input terminal of the output terminal of the first comparer U5B and the first comparer U5B; the output terminal of the first comparer U5B also is connected with the negative input end of the second comparer U5A; the positive input terminal of the second comparer U5A connects power supply by the 6th resistance R 33; the positive input terminal of the second comparer U5A is also by the 7th resistance R 40 ground connection; the output terminal of the second comparer U5A connects power supply by the 8th resistance R 34; the output terminal of the first comparer U5B also connects power supply by the 9th resistance R 37, and the output terminal of the second comparer U5A is the output terminal of this current foldback circuit 5.
The circuit that restarts circuit 6 is: the Restart Signal end CAL-E in the single chip circuit interface 7 is connected with an end of capacitor C 37, the other end of capacitor C 37 is connected with the positive pole of diode D13, the minus earth of diode D13, the other end of capacitor C 37 also are connected with the positive input terminal of the first comparer U5B by first resistance R 46.
Principle of work of the present invention is: analog to digital conversion circuit 2 makes the first field effect transistor Q5, the 4th field effect transistor Q3 of ac driven circuit 3 or the 3rd field effect transistor Q4, the second field effect transistor Q6 timesharing conducting by ac-excited driving circuit 4, forms the transducer excitation voltage of ac square wave form; The sensor excitation electric current flows through the sampling resistor R35 of current foldback circuit 5.Circuit powers on when starting working, because capacitor C 34 and C36 make the output terminal of the comparer U5B that wins remain on low level, the output terminal of the second comparer U5A remains on high level, and the output of Sheffer stroke gate U7A～U7D is at this moment worked by normal condition by the control of analog to digital conversion circuit 2.When sensor excitation circuit overcurrent or when short trouble occurring; the voltage drop at the sampling resistor R35 two ends of current foldback circuit 5 surpasses the partial pressure value of the 3rd resistance R 44 and the 4th resistance R 45; first comparer U5B upset, high level appears in the output terminal of U5B, makes the second comparer U5A overturn.The output terminal of U5A is a low level, make the output terminal of four Sheffer stroke gate U7A～U7D of ac-excited driving circuit 4 be locked in high level, make the 3rd field effect transistor Q4 and Q5 in the ac driven circuit 3 end immediately, cut off the excitation power supply of LOAD CELLS 1, prevented each device failure in the circuit.The high level that the first comparer U5B output terminal occurs makes comparer maintain rollover states by the positive input terminal that feedback resistance R41 is added in the first comparer U5B always.
Under the control of single-chip microcomputer; Restart Signal end CAL-E adds a negative pulse voltage; the positive input terminal that the capacitor C 37 by restarting circuit 6 and first resistance R 46 are coupled to the first comparer U5B of current foldback circuit 5; can make the first comparer U5B recover normal condition, diode D13 provides discharge channel for capacitor C 37.Can set single-chip microcomputer in single-chip microcomputer and restart number of times, the system that makes maintains guard mode stablizing under the state of fault.
Claims (4)
1. the holding circuit of an excitation power supply of weighing sensor; comprise analog to digital conversion circuit; the model of analog-digital conversion circuit as described is: AD7730BR; the output terminal of LOAD CELLS is connected with the analog input end of this analog to digital conversion circuit; the digital output end of this analog to digital conversion circuit is connected with the interface microcontroller circuit; the input end of LOAD CELLS is connected with first output terminal of ac driven circuit; the input end that it is characterized in that ac driven circuit is connected with the output terminal of ac-excited driving circuit; the first input end of this ac-excited driving circuit is connected with analog to digital conversion circuit; second input end of this ac-excited driving circuit is connected with the output terminal of current foldback circuit; the first input end of this current foldback circuit is connected with the output terminal that restarts circuit; the input end that restarts circuit is connected with the output terminal of interface microcontroller circuit; second input end of current foldback circuit is connected with second output terminal of ac driven circuit; wherein ac driven circuit comprises first field effect transistor and second field effect transistor that is connected in series; the 3rd field effect transistor that is connected in series and the 4th field effect transistor; ac-excited driving circuit comprises first Sheffer stroke gate and the 3rd Sheffer stroke gate; an input end of first Sheffer stroke gate is connected with the ACX end of analog to digital conversion circuit; another input end of first Sheffer stroke gate is connected with the output terminal of current foldback circuit; the output terminal of first Sheffer stroke gate is connected with the grid of first field effect transistor, input end of the 3rd Sheffer stroke gate and analog to digital conversion circuit
End connects, and another input end of the 3rd Sheffer stroke gate is connected with the output terminal of current foldback circuit, and the output terminal of the 3rd Sheffer stroke gate is connected with the grid of the 3rd field effect transistor.
2. the holding circuit of excitation power supply of weighing sensor as claimed in claim 1, it is characterized in that ac driven circuit is: the source electrode of first field effect transistor is connected with power supply, the drain electrode of first field effect transistor is connected with the drain electrode of second field effect transistor, the source electrode of second field effect transistor is connected with second input end of current foldback circuit, the source electrode of the 3rd field effect transistor is connected with power supply, the drain electrode of the 3rd field effect transistor is connected with the drain electrode of the 4th field effect transistor, the source electrode of the 4th field effect transistor is connected with second input end of current foldback circuit, the junction of first field effect transistor and second field effect transistor is an output terminal of excitation power supply, be connected with an input end of LOAD CELLS, the junction of the 3rd field effect transistor and the 4th field effect transistor is another output terminal of excitation power supply, is connected with another input end of LOAD CELLS; The circuit of ac-excited driving circuit is: an input end of first Sheffer stroke gate is connected with the ACX end of analog to digital conversion circuit; another input end of first Sheffer stroke gate is connected with the output terminal of current foldback circuit; the output terminal of first Sheffer stroke gate is connected with the grid of first field effect transistor; second Sheffer stroke gate and first Sheffer stroke gate are connected in parallel, input end of the 3rd Sheffer stroke gate and analog to digital conversion circuit
End connects,
Another input end of the 3rd Sheffer stroke gate is connected with the output terminal of current foldback circuit; the output terminal of the 3rd Sheffer stroke gate is connected with the grid of the 3rd field effect transistor; the 4th Sheffer stroke gate and the 3rd Sheffer stroke gate are connected in parallel; the grid of the 4th field effect transistor is connected with the ACX of analog to digital conversion circuit end, the grid of second field effect transistor and analog to digital conversion circuit
End connects.
3. the holding circuit of excitation power supply of weighing sensor as claimed in claim 2; the circuit that it is characterized in that current foldback circuit is: second input end of this current foldback circuit is an end of sampling resistor; the other end ground connection of sampling resistor; second input end of this current foldback circuit also is connected with an end of second resistance; the other end of second resistance is connected with the positive input terminal of first comparer; the positive input terminal of first comparer also passes through capacity earth; the negative input end of first comparer connects power supply by the 3rd resistance; the negative input end of first comparer is simultaneously by the 4th resistance eutral grounding; the negative input end of first comparer also connects power supply by electric capacity and the resistance that is connected in series; be connected with feedback resistance between the positive input terminal of the output terminal of first comparer and first comparer; the output terminal of first comparer also is connected with the negative input end of second comparer; the positive input terminal of second comparer connects power supply by the 6th resistance; the positive input terminal of second comparer is also by the 7th resistance eutral grounding; the output terminal of second comparer connects power supply by the 8th resistance; the output terminal of first comparer also connects power supply by the 9th resistance, and the output terminal of second comparer is the output terminal of this current foldback circuit.
4. the holding circuit of excitation power supply of weighing sensor as claimed in claim 3; it is characterized in that the circuit that restarts circuit is: the Restart Signal end in the interface microcontroller circuit is connected with an end of electric capacity; the other end of electric capacity is connected with the positive pole of diode; the minus earth of diode, the other end of electric capacity also are connected with the positive input terminal of first comparer by first resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN200810038266XA CN101592517B (en) | 2008-05-29 | 2008-05-29 | Protection circuit of excitation power supply of weighing sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN200810038266XA CN101592517B (en) | 2008-05-29 | 2008-05-29 | Protection circuit of excitation power supply of weighing sensor |
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| Publication Number | Publication Date |
|---|---|
| CN101592517A CN101592517A (en) | 2009-12-02 |
| CN101592517B true CN101592517B (en) | 2011-02-23 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN200810038266XA Active CN101592517B (en) | 2008-05-29 | 2008-05-29 | Protection circuit of excitation power supply of weighing sensor |
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| Country | Link |
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| CN (1) | CN101592517B (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4458284A (en) * | 1981-06-12 | 1984-07-03 | Shin-Shirasuna Electric Corp. | Method for electrical and thermal protection of output devices of electronic amplifiers |
| CN1054337A (en) * | 1990-09-13 | 1991-09-04 | 浙江大学 | Protection Circuit of High Power Darlington Transistor |
| CN2435730Y (en) * | 2000-08-04 | 2001-06-20 | 中山大学 | Multi-functional price-computing electronic balance controller |
-
2008
- 2008-05-29 CN CN200810038266XA patent/CN101592517B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4458284A (en) * | 1981-06-12 | 1984-07-03 | Shin-Shirasuna Electric Corp. | Method for electrical and thermal protection of output devices of electronic amplifiers |
| CN1054337A (en) * | 1990-09-13 | 1991-09-04 | 浙江大学 | Protection Circuit of High Power Darlington Transistor |
| CN2435730Y (en) * | 2000-08-04 | 2001-06-20 | 中山大学 | Multi-functional price-computing electronic balance controller |
Non-Patent Citations (3)
| Title |
|---|
| JP昭57-127819A 1982.08.09 |
| 张保青等.称重给煤机控制系统中AD7730芯片的应用.《发电设备》.2007,(第1期),52-55. * |
| 郭彪等.AD7730在高精度电子秤中的应用.《兵工自动化》.2005,第24卷(第2期),69-70. * |
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| CN101592517A (en) | 2009-12-02 |
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