Open circuit protection method and circuit for a current source

Abstract

The application discloses an open-circuit protection method and circuit of a current source. The open-circuit protection output circuit comprises a DAC output control module, a voltage-current conversion module, a current detection module, an AD acquisition module, a load switching module and an MCU control module. The DAC output control module is used for controlling the output voltage value of a digital-analog conversion module. The voltage-current conversion module is used for converting the voltage value of the DAC output control module into a specified current value. The current detection module is used for detecting the current state on a load. The AD acquisition module is used for acquiring the voltage value output by the current detection module and performing analog-digital conversion, and outputting the current value on the current load. The load switching module is used for switching the working load. The MCU control module is used for controlling the voltage value of the DAC output control module, controlling the load conversion of the load switching module, and receiving the current value acquired by the AD acquisition module. The application can effectively judge the current circuit state, avoid damaging the circuit due to open circuit, and ensure that the current source normally outputs under the condition of requiring zero current.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current source, in particular to a kind of open circuit protection method and circuit of current source. BACKGROUND

[0002] In DC current comparator bridge, the current source capable of stable output constant current is one of very important components, and when the current source works, due to the need of load switching, open circuit phenomenon inevitably appears in circuit, if the open circuit condition of circuit is not protected, irreversible damage will be caused to the device in current source, but in specific situation, zero current output is also needed by current source;Therefore, an open circuit protection method of current source is needed to realize the open circuit condition of current source, and distinguish zero current output condition at the same time.

[0003] At present, the open circuit protection method used by most current sources is the circuit composed of diode and stabilizing tube, which protects by controlling the load current through the cut-off and conduction of diode when open circuit occurs. This protection method can protect the circuit when open circuit occurs, but this protection method cannot distinguish the special case of zero current output required by load, and will perform protection operation for any open circuit condition, therefore, the application range of this open circuit protection circuit is small. SUMMARY

[0004] To solve the above problems in the prior art, the purpose of the present application is to provide an open circuit protection method and circuit of current source, which can effectively judge the current circuit state, avoid the damage of circuit due to open circuit, and ensure the normal output of current source in the case of zero current requirement.

[0005] One aspect of the present application provides an open circuit protection output circuit of current source, comprising:

[0006] DAC output control module, for controlling the output voltage value of digital-to-analog conversion module;

[0007] Voltage-current conversion module, for converting the voltage value of the DAC output control module into a specified current value to form the current source;

[0008] Current detection module, for detecting the current state on the load and converting the current into a voltage signal;

[0009] AD acquisition module, for acquiring the voltage value output by the current detection module and performing analog-to-digital conversion to output the current value on the current load;

[0010] Load switching module, for switching working load to protect the circuit when the current source is open circuit;

[0011] MCU control module, for controlling the DAC output control module, load switching module load conversion, receiving the current value collected by the AD acquisition module;

[0012] Wherein, the output end of the DAC output control module is connected to the input end of the voltage-current conversion module, the output end of the voltage-current conversion module is connected to the input end of the current detection module, the input end of the AD acquisition module is connected to the output end of the current detection module, and the input end of the load switching module is connected to the output end of the voltage-current conversion module.

[0013] The load switching module comprises:

[0014] Single-pole double-throw relay switch, the single-pole double-throw relay switch comprises a first fixed end S A , a second fixed end S B , a moving end D, a signal control end P1 and a signal control end P2.

[0015] Resistance, the resistance comprises: load resistance R L And temporary load resistance R L ’;

[0016] Wherein, the first fixed end S A of the single-pole double-throw relay switch is connected to the input end of the load resistance R L , the first fixed end S B of the single-pole double-throw relay switch is connected to the input end of the temporary load resistance R L ’, the moving end D of the single-pole double-throw relay switch is connected to the output end of the voltage-current conversion module, and the signal control ends P1 and P2 of the single-pole double-throw relay switch are connected to the MCU control module.

[0017] Further, the load switching module further comprises a relay drive circuit, and the single-pole double-throw relay switch is connected to the MCU control module through the drive circuit.

[0018] Another aspect of the present application provides an open circuit protection method for a current source, which adopts the above-mentioned circuit and comprises the following steps:

[0019] Step one, current source initialization starts to output a set current;

[0020] Step two, the Hall current sensor in the current detection module starts to detect the current value on the load;

[0021] Step three, it is judged whether the current value on the load at this time is less than or equal to the set open circuit current threshold value, if the current value on the load at this time is less than or equal to the set open circuit current threshold value, step four is entered; otherwise, step ten is entered.

[0022] Step four, judge whether the output current set at this time is zero, if the output current set at this time is zero, then enter step five, otherwise enter step six;

[0023] Step five, the current source normally outputs;

[0024] Step six, enter the open circuit protection mode, operate the relay to switch the load to the temporary load;

[0025] Step seven, the Hall current sensor starts to detect the current value on the temporary load;

[0026] Step eight, judge whether the current value on the temporary load at this time is less than or equal to the set open circuit current threshold, if the current value on the load at this time is less than or equal to the set open circuit current threshold, indicating that the temporary load is also in the open circuit state, then enter step nine, otherwise the current source outputs on the temporary load with the set current to achieve open circuit protection, enter step five;

[0027] Step nine, reset the current source to output with zero current, return to step one;

[0028] Step ten, judge whether the current output on the load at this time is equal to the set current value, if the current on the load is equal to the set current value, then enter step five, otherwise enter step eleven;

[0029] Step eleven, compare the detected current value on the load with the set current value, calculate the difference to correct the current, so as to improve the output accuracy of the current source, reset the output of the current source, and return to step one.

[0030] Compared with the prior art, the beneficial effects of the present application are that:

[0031] The current circuit state can be effectively judged by the Hall current sensor, so as to avoid the circuit from being damaged due to open circuit, and the current source can normally output in the case of zero current;

[0032] The relay is used to switch the load and the temporary load, so as to protect the circuit;

[0033] The current value detected by the Hall current sensor can be compared with the set current value after being collected by the AD collection module, so as to further correct the accuracy of the current source output. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is the circuit block diagram of the open circuit protection circuit of the embodiment of the present application.

[0035] Figure 2 is the relay driving circuit diagram of the embodiment of the present application.

[0036] Figure 3 is a flow chart of the open circuit protection method of the embodiment of the present application. DETAILED DESCRIPTION

[0037] In order for the reader to better understand the design purpose of the present application, the following specific embodiments are provided to enable the reader to visually understand the structure, structure composition, principle of action and technical effects involved in the present application. However, it should be noted that the following embodiments are not a limitation of the technical solutions of the present application, and those skilled in the art can make a series of deformations and equivalent replacements to the technical solutions provided by the present application based on the analysis and understanding of the embodiments, and the new technical solutions obtained by the deformations and equivalent replacements are also included in the present application.

[0038] As shown in Figure 1 , an open circuit protection circuit of a current source, the embodiment includes a DAC output control module for controlling the output voltage value of a digital-to-analog conversion module; a voltage-to-current conversion module (current source) for converting the voltage value of the DAC output control module into a specified current value; a current detection module for detecting the current state on the load; an AD acquisition module for acquiring the voltage value output by the current detection module and performing analog-to-digital conversion, outputting the current value on the current load; a load switching module for switching the working load to protect the circuit when the current source is open; an MCU control module for controlling the voltage value of the DAC output control module, controlling the load transformation of the load switching module, and receiving the current value acquired by the AD acquisition module; wherein the output end of the DAC output control module is connected to the input end of the voltage-to-current conversion module, the output end of the voltage-to-current conversion module is connected to the input end of the current detection module, the input end of the AD acquisition module is connected to the output end of the current detection module, and the input end of the load switching module is connected to the output end of the voltage-to-current conversion module.

[0039] As an implementation manner, the voltage-to-current conversion module includes: a first operational amplifier A1, a second operational amplifier A2, and four precision resistors with the same resistance; wherein the output end of the DAC output control module is connected to the inverting input end of the first operational amplifier through a resistor R1, the non-inverting input end of the first operational amplifier is connected to a negative power supply through a resistor R3, the output end of the resistor R1 is connected to the output end of the first operational amplifier through a resistor R2, the output end of the first operational amplifier is connected to the non-inverting input end of the second operational amplifier through a resistor Rsa, the inverting input end of the second operational amplifier is connected to the output end of the second operational amplifier, and the output end of the second operational amplifier is connected to the non-inverting input end of the first operational amplifier through a resistor R4.

[0040] The current source output Iout is calculated by the formula Iout = Ui / Rsa.

[0041] As an implementation manner, the current detection module comprises: a Hall current sensor H, an operational amplifier A3, and amplification resistors R5, R6 and R7; wherein the positive terminal of a Hall element in the Hall current sensor is connected to the non-inverting input terminal of the operational amplifier A3 through the resistor R5, the negative terminal of the Hall element is connected to the inverting input terminal of the operational amplifier A3 through the resistor R7, the non-inverting input terminal of the operational amplifier A3 is connected to the output terminal of the operational amplifier A3 through the resistor R6, and the output terminal of the operational amplifier A3 is connected to the input terminal of the AD acquisition module.

[0042] The current I detected by the current detection module is converted by the formula , wherein A is the amplification factor of the operational amplifier, μ0 is the vacuum permeability, N is the number of turns of the coil, and l is the air gap length.

[0043] As an implementation manner, the load switching module comprises: a single-pole double-throw relay switch, the single-pole double-throw relay switch comprising a first stationary end S A , a second stationary end S B , a moving end D, a signal control end P1 and a signal control end P2; and resistors comprising: a load resistor R L and a temporary load resistor R L '; wherein the first stationary end S A of the single-pole double-throw relay switch is connected to the input end of the load resistor R L , the first stationary end S B of the single-pole double-throw relay switch is connected to the input end of the temporary load resistor R L ', the moving end D of the single-pole double-throw relay switch is connected to the output end of the voltage-current conversion module, and the signal control ends P1 and P2 of the single-pole double-throw relay switch are connected to the MCU control module.

[0044] As shown in Figure 2 , the embodiment provides a driving circuit of a relay in current source open circuit protection, comprising:

[0045] an input end S IN , configured to provide an input current required by a load;

[0046] a relay coil control end C, configured to control a relay switch;

[0047] a program control end GPIOA, configured to control the relay coil control end C by a program;

[0048] a diode, comprising: a diode D1;

[0049] a triode, comprising: an NPN triode D2;

[0050] a resistor, the resistor comprising: a first resistor R1 and a second resistor R2;

[0051] a power supply, the power supply comprising a positive power supply VCC and a negative power supply VEE;

[0052] wherein, the cathode of the first diode D1 is connected to the positive power supply VCC, the anode of the first diode D1 is connected to the relay coil control end C, the collector of the triode D2 is connected to the anode of the diode D1, the base of the triode D2 is connected to the program control end GPIOA through the first resistor R1; the base of the triode D2 is connected to the emitter of the triode D2 through the second resistor R2; and the emitter of the triode D2 is connected to the negative power supply VEE.

[0053] As shown in Figure 3 the embodiment provides an open circuit protection method of a current source, comprising the following steps:

[0054] Step one, the current source is initialized to start outputting a set current;

[0055] Step two, the Hall current sensor starts detecting the current value on the load;

[0056] Step three, it is judged whether the current value on the load at this time is less than or equal to the set open circuit current threshold value, if the current value on the load at this time is less than or equal to the set open circuit current threshold value, step four is entered;

[0057] Step four, it is judged whether the set output current at this time is zero, if the set output current at this time is zero, step five is entered;

[0058] Step five, the current source normally outputs;

[0059] In step four, if the set output current at this time is not zero, step six is entered at this time;

[0060] Step six, the circuit enters an open circuit protection mode, and the circuit operates the relay to switch the load to a temporary load;

[0061] Step seven, the Hall current sensor starts detecting the current value on the temporary load;

[0062] Step eight, it is judged whether the current value on the temporary load at this time is less than or equal to the set open circuit current threshold value, if the current value on the load at this time is less than or equal to the set open circuit current threshold value, it indicates that the temporary load is also in an open circuit state, and then step nine is entered;

[0063] Step nine, the current source is reset to output zero current, and returns to step one;

[0064] In step eight, if the current value on the temporary load is greater than the open circuit current threshold value, the current source outputs the set current on the temporary load to achieve the open circuit protection purpose, and enters step five;

[0065] In step three, if the current value on the load is greater than the open circuit current threshold value, enter step ten;

[0066] Step ten, judge whether the current output on the load is equal to the set current value, if the current on the load is equal to the set current value, enter step five;

[0067] In step ten, if the current on the load is not equal to the set current value, enter step eleven;

[0068] Step eleven, the program compares the detected current value on the load with the set current value, calculates the difference value to correct the current, so as to improve the output accuracy of the current source, reset the output of the current source, and return to step one.

Claims

1. An open-circuit protection output circuit for a current source, characterized in that, include: The DAC output control module is used to control the output voltage value of the digital-to-analog converter module. A voltage-to-current conversion module is used to convert the voltage value of the DAC output control module into a specified current value to form the current source; The current detection module is used to detect the current state on the load and convert the current into a voltage signal; The AD acquisition module is used to acquire the voltage value output by the current detection module, perform analog-to-digital conversion, and output the current value on the current load. The load switching module is used to switch the working load and protect the circuit when the current source is open. The MCU control module is used to control the DAC output control module, the load switching module, and to receive the current value acquired by the AD acquisition module. Wherein, the output terminal of the DAC output control module is connected to the input terminal of the voltage-to-current conversion module, the output terminal of the voltage-to-current conversion module is connected to the input terminal of the current detection module, the input terminal of the AD acquisition module is connected to the output terminal of the current detection module, and the input terminal of the load switching module is connected to the output terminal of the voltage-to-current conversion module; The load switching module includes: A single-pole double-throw relay switch, the single-pole double-throw relay switch including a first fixed terminal S A Second fixed end S B The active terminal D, the signal control terminal P1, and the signal control terminal P2; The resistor includes: a load resistor R L and temporary load resistor R L ’ ; Wherein, the first stationary terminal S of the single-pole double-throw relay switch A Connect the load resistor R L The input terminal, the first stationary terminal S of the single-pole double-throw relay switch B Connect the temporary load resistor R L ’ The input terminal of the single-pole double-throw relay switch is connected to the output terminal of the voltage-to-current conversion module, and the signal control terminals P1 and P2 of the single-pole double-throw relay switch are connected to the MCU control module.

2. The open-circuit protection output circuit for a current source according to claim 1, characterized in that: The load switching module also includes a relay drive circuit, and the single-pole double-throw relay switch is connected to the MCU control module through the drive circuit.

3. An open-circuit protection method for a current source, employing the circuit described in claim 1, characterized in that, The steps include the following: Step 1: The current source is initialized and begins to output the set current. Step two: The Hall current sensor in the current detection module begins to detect the current value on the load; Step 3: Determine whether the current value on the load is less than or equal to the set open circuit current threshold. If the current value on the load is less than or equal to the set open circuit current threshold, proceed to Step 4; otherwise, proceed to Step 10. Step 4: Determine if the set output current is zero. If the set output current is zero, proceed to Step 5. Otherwise, proceed to step six; Step 5: The current source outputs normally; Step 6: Enter open circuit protection mode and operate the relay to switch the load to a temporary load; Step 7: The Hall current sensor begins to detect the current value on the temporary load; Step 8: Determine whether the current value on the temporary load is less than or equal to the set open circuit current threshold. If the current value on the load is less than or equal to the set open circuit current threshold, proceed to step 9; otherwise, the current source outputs the set current on the temporary load to achieve open circuit protection, and proceed to step 5. Step 9: Reset the current source to zero current output and return to Step 1; Step 10: Determine whether the current output on the load is equal to the set current value. If the current on the load is equal to the set current value, proceed to step 5. Otherwise, proceed to step eleven; Step 11: Compare the current value detected on the load with the set current value, calculate the difference to correct the current, reset the output of the current source, and return to Step 1.

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