CN212159919U

CN212159919U - Dual-mode direct current sensor circuit

Info

Publication number: CN212159919U
Application number: CN202020658663.3U
Authority: CN
Inventors: 泮展; 陈庭勋
Original assignee: Zhejiang Ocean University ZJOU
Current assignee: Zhejiang Ocean University ZJOU
Priority date: 2020-04-14
Filing date: 2020-04-14
Publication date: 2020-12-15
Anticipated expiration: 2030-04-14

Abstract

The utility model provides a bimodulus direct current sensor circuit, this circuit is by current sampling resistance and amplifier, the parallelly connected array of power field effect transistor, field effect transistor array drive circuit, hall sensor differential amplification circuit four bibliographic categories divide and constitute, wherein current sampling resistance, the current monitor chip, the power amplification chip of input/output rail to rail, six P channel power field effect transistor reposition of redundant personnel array etc. constitute undercurrent detection circuit, two hall sensors and differential amplification circuit constitute heavy current detection circuit, circuit sharing one is for the direct current negative 5.0V power of high potential side, detect same high potential side collateral branch electric current, there are two independent current detection outputs. The utility model discloses an useful part adopts a current sensor just can realize 10mA ~ 50A's wide range current detection under the condition that does not reduce measurement accuracy, has both satisfied the accurate measurement of undercurrent, the little consumption requirement when satisfying the heavy current measurement simultaneously.

Description

Dual-mode direct current sensor circuit

Technical Field

The utility model discloses the content that bimodulus direct current sensor circuit relates belongs to electron measurement technical field for direct current wide range's measurement.

Background

Measuring current is a basic measurement task in the field of electronic technology, wherein the most extensive measurement task is realized by sampling with a low-resistance resistor, and a series of 'sampling resistors' is listed separately, the sampling resistors have many specifications, and the sampling resistor with high current is also called a shunt. The resistance sampling mode is almost uniformly adopted in the field of small current measurement, so that higher precision and lower power consumption can be achieved, and most of ammeter modules are realized by the resistance sampling mode. In a large-current environment, a shunt is adopted for sampling, alternating current and direct current are commonly used, the volume of the shunt is large, and the consumed power is not small; some current transformers are adopted for sampling, the current transformers are only suitable for alternating current measurement, power loss is small, measurement accuracy is usually low, some current transformers are adopted for sampling, alternating current and direct current are common, and the measurement accuracy is also low, for example, a clamp-on ammeter is a current transformer or hall current sensor sampling mode.

At present, no matter a sampling resistor, a mutual inductor and a sensor are used for sampling current, the current is limited by measurement accuracy and resolution, and the measurement range of the current is narrow. For example, a 5A ammeter realized by using a resistance sampling mode can display and calculate according to 1% precision and 4-bit digital display, can be accurate to 50mA grade, and can distinguish current of 1mA grade; if the ammeter is made into a 20A ammeter, the ammeter can only be accurate to 200mA, and the current of 10mA can be distinguished. For a large-current ammeter sampled by using a mutual inductor and a sensor, 1% precision is difficult to realize, the 100A ammeter can only be accurate to 2A level according to 2% precision and 4-bit digital display calculation, the current of 100mA level is distinguished, and the real current value below 2A cannot be basically and accurately indicated.

For a standby power supply for supplying power to a high-power lithium battery pack, only milliampere current is needed sometimes, but hundreds of amperes of current is needed in some occasions, and the current span is large. In order to display the current as small as milliampere level or as large as hundred ampere level in real time in a wide range, the current can not be comprehensively taken care of by singly adopting resistance sampling or sensor sampling, so that the current can only adopt two modes of resistance sampling and sensor sampling simultaneously, namely the double modes. The dual-mode sampling needs to solve the problems of too high voltage drop and too large power consumption when large current flows through a sampling resistor. For example, if a small current detection is required, a 0.02 Ω sampling resistor is used, a voltage drop is 60mV when a current of 3A flows, power consumption is 0.18W, and a 1W sampling resistor is enough to bear, but if a current of 30A flows, 18W power consumption is generated, and a non-bulky shunt cannot be used. The utility model discloses a focus is the consumption of restriction sampling resistance.

Disclosure of Invention

The utility model discloses bimodulus direct current sensor circuit sees from the technical aspect, has following characteristic:

the dual-mode direct current sensor circuit comprises a current sampling resistor and an amplifier thereof, a power field effect tube parallel array, a field effect tube array driving circuit and a Hall sensor differential amplifying circuit, as shown in figure 1, the circuit has two independent current sampling outputs, small current sampling is formed by connecting two sampling resistors R1 and R1b in parallel and is connected to an input port of a current monitor chip INA139, two ends of the sampling resistors are connected with a shunt array formed by connecting six P-channel power field effect tubes in parallel, and a grid electrode of the shunt array of the six P-channel power field effect tubes is driven by an input/output rail-to-rail power amplifying chip OPA 567; the large electric sampling is realized by a differential amplifying circuit consisting of two Hall sensors, as shown in figure 2; two independent current sampling circuits detect the same high potential side branch current and share a direct current negative 5.0V power supply relative to the high potential side.

The Hall sensor differential amplifying circuit in the dual-mode direct current sensor circuit is provided with a high-precision reference voltage source chip TL431 or TLV431, and the output voltage of the reference voltage source is divided by resistors R15 and R16 and then is connected to the non-inverting input end of the operational amplifier through a resistor R14; the resistors R11 and R13 in the amplifying circuit are equal in resistance, and the resistors R12 and R14 are equal in resistance.

The initial voltage limiting value of two ends of a sampling resistor in the dual-mode direct current sensor circuit is set from a 5.0V power supply through resistor voltage division, and a resistor voltage division point is connected to the inverted input end of a power amplification chip OPA 567.

The dual-mode direct current sensor circuit has the following beneficial effects:

the wide-range current detection of 10 mA-50A can be realized by adopting one current sensor under the condition of not reducing the measurement precision, thereby not only meeting the accurate measurement of small current, but also meeting the micro-power consumption requirement during the measurement of large current.

The parallel array of six P-channel power field effect transistors is an important characteristic of the utility model. If the six power field effect transistors adopt the AOD403, each conduction internal resistance is about 9m omega, the conduction internal resistance is about 1.5m omega after parallel connection, the voltage drop is 75mV when 50A current flows, the generated power loss is 3.75W, the power loss is distributed to the six field effect transistors, the six field effect transistors are added with conductive copper sheets of two poles, the six field effect transistors can continuously work for a short time, and the surge current can be increased to 100A.

The field effect transistor is connected in parallel to form a large grid capacitor, so that a driving circuit of the field effect transistor needs to have a large enough driving current, a wide enough output potential swing range and a high enough response speed, and meanwhile, the current detection is a small voltage formed relative to the positive electrode of a power supply, and an amplifier needs to have a wide enough common-mode input voltage range, namely, a rail-to-rail power amplifier is required. The selectable space of the device is small, a power amplifier chip OPA567 is selected, the voltage range of a working power supply is 2.7-5.5V, the bandwidth is 1.2MHz, the open-loop gain is 80dB, the maximum output current capacity is 2A, the use requirement is completely met, and the circuit structure is simple. The output rail-to-rail function of the OPA567 can ensure the reliable closing and the reliable opening of the power field effect transistor; the input positive supply rail function of OPA567 can directly input a minute voltage on the high side sampling resistor.

The initial voltage limiting values at the two ends of the current sampling resistor refer to voltage values which start to enter a voltage limiting state, and the voltages at the two ends of the sampling resistor are increased along with the further increase of the working current. The resistors R5 and R6 are connected in series and then are divided into voltage with R4, so that the initial voltage division value is accurately set by finely adjusting the resistance value of R5 or R6, and the linear measurement range of the sampling resistor is ensured.

In a large-current detection circuit, an A3503 chip is adopted and selected for the linear Hall sensor, and the influence of an environmental magnetic field on measurement can be eliminated by adopting two differential outputs. The voltage division value obtained by the R15 and R16 voltage division circuits on R16 determines the static output potential V of the operational amplifier IC4_oStatic potential V_oThe stability of (c) corresponds to the degree of drift of the current indication. The high-precision reference voltage source TL431 is arranged in the circuit to improve the measurement precision which is related to the temperature drift characteristic of each deviceMost important is the effect of supply voltage fluctuations. The reference voltage can also be stabilized by using TLV431 chip, and when TLV431 is used, the resistance R18 is 1.8k omega, and R15 is 680 omega. According to the conversion rate of 2.5V corresponding to 100A, a current error of 4A can be caused by a voltage error of 0.1V, if the voltage error is not more than 25mV when the measurement accuracy of 1% is reached, the error of a common 5V voltage-stabilizing chip is 50mV, and the accuracy requirement of 1% cannot be met; after a high-precision reference voltage source is adopted, the voltage error can be limited within 10mV, and the precision of the term can reach more than 0.4%. The ratio of the resistors R12 and R11 determines the voltage gain of the Hall sensor differential amplifier circuit. The thickness of the hall sensor chip affects the current-to-voltage conversion ratio, and therefore the ratio of the resistances R12 to R11 is determined by the actual voltage gain requirement of the circuit. For example, the measured 50A current can make each hall sensor output 0.21V, the voltage difference is 0.42V, the circuit amplification is 3 times, and the ratio of the resistors R12 and R11 is 3.

Drawings

Fig. 1 is a block diagram of a dual mode dc current sensor circuit.

Fig. 2 is a high current detection circuit configuration of a dual mode dc current sensor circuit.

In the figure, H1 and H2 are linear hall sensors, and IC4 is an operational amplifier.

Fig. 3 is a complete structure of the dual-mode dc current sensor circuit.

In the figure, IOL is the output voltage of the small current detection and IOH is the output voltage of the large current detection.

Detailed Description

The following will further explain the implementation of the present invention by combining the drawings of the present invention.

The voltage dividing structure of the resistors R15 and R16 is used to fine tune the quiescent potential at the output of the operational amplifier IC 4. In the case of battery power supply, the maximum discharge current is a positive current with a large value, and the charge current is a negative current with a small value, and the quiescent potential V at the output terminal of the operational amplifier IC4 is set to be a positive current with a display of both currents_oCan be set to 0.3-0.5V. Maximum charging current through the module does not exceed-5A, if necessaryTo detect a larger charging current, a charging lead can directly pass through an inner hole of a magnetic ring in the sensor, and the sensor can output a current detection signal from a large current port as usual.

Six field effect transistors are adopted in the circuit to be connected in parallel, which corresponds to the upper limit of the current of 50A, and if the upper limit of the measured current is further improved, the number of the power field effect transistors for shunting is increased.

Before the voltage of the sampling resistor is limited, the sampling resistor is in a linear measurement range, and is nonlinear after voltage limiting is started, so that the sampling value loses the measurement significance. The initial voltage limiting values of two ends of the sampling anode are set by resistors R4, R5 and R6, if the measured current is measured by a 25m omega sampling resistor below 2A, the linear voltage range is 0-50 mV, some margin is properly reserved, and the initial voltage limiting value is set to be 55mV, so that R4 can be taken as 10k omega, R5 can be taken as 82k omega, and R6 can be taken as 820k omega.

The dual-mode direct current sensor circuit has two current detection outputs, an IOL is an output voltage of small current detection, and an IOH is an output voltage of large current detection, and can be matched with two independent output indications, but generally, the two independent output indications are automatically converted and displayed by an indicator, for example, the two independent output indications are input into the same singlechip to be uniformly displayed, when the working current of a detected line is small, an IOL signal is taken, and when the working current is larger than 2A inches, the IOH signal is automatically used. The index conversion principle of the current indicator is to determine the magnitude relationship between the IOL and the IOH signal. IOL > 50 [ (. IOH-V)_o) Taking the IOL signal for display at one time and taking the IOH signal for display at the other, wherein V_oIs the static output potential of the operational amplifier IC 4.

The dual-mode current sensor circuit is suitable for detecting the current of the positive line of the power supply, and the 5.0V working voltage of the dual-mode current sensor circuit is negative 5.0V relative to the positive pole of the external power supply. A voltage stabilizing system is not arranged in the dual-mode current sensor, 5.0V working voltage is provided by an external negative power supply voltage stabilizing chip, and the 5.0V power supply is shared with an external microcomputer processing circuit. The signal voltage output by the dual-mode current sensor can form a common ground structure with an external microcomputer processing circuit relative to the cathode of a 5.0V power supply. And just because the dual-mode current sensor shares a 5.0V power supply with an external microcomputer processing circuit, a voltage stabilizing system cannot be independently arranged in the dual-mode current sensor. The applicable system voltage range of the tested circuit depends on the voltage withstanding capability between the external negative 5.0V voltage stabilizing circuit and the tested circuit.

Claims

1. A dual-mode direct current sensor circuit is characterized in that: the circuit comprises a current sampling resistor and an amplifier thereof, a power field effect tube parallel array, a field effect tube array driving circuit and a Hall sensor differential amplifying circuit, wherein the circuit is provided with two independent current detection outputs, the small current sampling is formed by connecting two sampling resistors R1 and R1b in parallel and is connected to an input port of a current monitor chip INA139, two ends of each sampling resistor are connected with a shunt array formed by six P-channel power field effect tubes in parallel, and the grid electrodes of the shunt array of the six P-channel power field effect tubes are driven by an input/output rail-to-rail power amplifying chip OPA 567; the large-power sampling is realized by a differential amplifying circuit consisting of two Hall sensors; two independent current sampling circuits detect the same high potential side branch current and share a direct current negative 5.0V power supply relative to the high potential side.

2. The dual-mode direct current sensor circuit of claim 1, wherein: the Hall sensor differential amplifying circuit in the circuit is provided with a high-precision reference voltage source chip TL431 or TLV431, and the output voltage of the reference voltage source is divided by resistors R15 and R16 and then is connected to the non-inverting input end of the operational amplifier through a resistor R14; the resistors R11 and R13 in the amplifying circuit are equal in resistance, and the resistors R12 and R14 are equal in resistance.

3. The dual-mode direct current sensor circuit of claim 1, wherein: the initial voltage limiting values at the two ends of the sampling resistor are set from a 5.0V power supply through resistor voltage division, and a resistor voltage division point is connected to the inverted input end of the power amplification chip OPA 567.