CN201203476Y - Protective circuit of weighing sensor energized power supply - Google Patents

Abstract

The utility model discloses a protective circuit of weighing sensor excitation power supply, which is characterized in that, an input end of an AC excitation circuit is connected with an output end of an AC excitation drive circuit, a first input end of the AC excitation drive circuit is connected with an A/D converting circuit, a second input end of the AC excitation drive circuit is connected with an output end of an overcurrent protection circuit, a first input end of the overcurrent protection circuit is connected with an output end of a reset circuit, an input end of the reset circuit is connected with an input end of a SCM circuit interface, a second input end of the overcurrent protection circuit is connected with a second output end of the AC excitation circuit. The utility model implements reliable protection for sensor AC excitation power supply, avoids instrument damage caused by exterior fault. The reset circuit provides possibility for automatically recovering work of system under condition of exterior circuit instant fault to enable the system to be more steady.

Description

The holding circuit of excitation power supply of weighing sensor

Technical field

The utility model relates to circuit field, is 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 purpose of this utility model is to provide a kind of holding circuit of reliable and stable excitation power supply of weighing sensor.

To achieve these goals; the technical solution of the utility model is as follows: the 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, and second input end of current foldback circuit is connected with second output terminal of ac driven circuit.

The utility model 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.Advantage of the present utility model is can play a protective role excitation power supply of weighing sensor being carried out the analog-to-digital while, and the instrument of having avoided causing because of external fault is damaged.

Description of drawings

Fig. 1 is the circuit diagram of prior art

Fig. 2 is a block diagram of the present utility model

Fig. 3 is the circuit diagram of the utility model one embodiment

Embodiment

Below in conjunction with drawings and Examples the utility model is elaborated.

It among Fig. 2 a kind of holding circuit of excitation power supply of weighing sensor; 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 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 second 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 and the input end of current foldback circuit 5 are that the end of sampling resistor R35 is connected; 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 and the input end of current foldback circuit 5 are that the end of sampling resistor R35 is connected; 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 control end 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 is connected with the ACX end of analog to digital conversion circuit 2; 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, and the grid of the second field effect transistor Q6 is connected with the ACX end of analog to digital conversion circuit 2.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 of 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 utility model 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 (5)

1; the 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, and second input end of current foldback circuit is connected with second output terminal of ac driven circuit.

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 the 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 the input end of current foldback circuit; the junction of first field effect transistor and second field effect transistor is connected with an input end of LOAD CELLS; the junction of the 3rd field effect transistor and the 4th field effect transistor is connected with another input end of LOAD CELLS, and the grid of these four field effect transistor is connected with ac-excited driving circuit.

3; the holding circuit of excitation power supply of weighing sensor as claimed in claim 2; the circuit that it is characterized in that 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; an input end of the 3rd Sheffer stroke gate is connected with the ACX end 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; 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, and the grid of second field effect transistor is connected with the ACX of analog to digital conversion circuit end.

4; the holding circuit of excitation power supply of weighing sensor as claimed in claim 3; the circuit that it is characterized in that current foldback circuit is: the input end of this current foldback circuit is connected with an end of sampling resistor; the other end ground connection of sampling resistor; the 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.

5, the holding circuit of excitation power supply of weighing sensor as claimed in claim 4; it is characterized in that the circuit that restarts circuit is: the Restart Signal end in the single chip circuit interface 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 R 46.

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