Constant current source for overcurrent protection

Abstract

The invention discloses a constant current source for overcurrent protection, and belongs to the technical field of precision measurement. Comprising a mirror image constant current source and a controllable precision voltage reference which are connected in series; the mirror image constant current source is connected with a current detection unit and is used for carrying out current detection and outputting a detection signal; an overcurrent protection threshold current is preset in the current detection unit; the current detection unit is connected with an on-off control unit; the on-off control unit is in signal connection with an external enable end and is used for receiving an external enable end signal; an external enabling threshold value is preset in the on-off control unit; the on-off control unit is connected with the controllable precision voltage reference; the mirror image constant current source is connected with an external power supply; after the detection signal and the external enable end signal pass through the on-off control unit, the on-off control unit sends out a control signal to control enabling of the controllable precise voltage reference, on-off control over the mirror image constant current source is achieved, and the high-precision current reference can be output.

Description

Technical Field

[0001] The invention belongs to the technical field of precision measurement and relates to a constant current source for overcurrent protection. Background Art

[0002] Pyrotechnics are one-time detonating components or devices containing sensitive agents. When subjected to a small external stimulus, they can stimulate the internal explosive agent through external energy to complete functions such as ignition, fire transmission, and detonation. Pyrotechnics are widely used in both military and civilian fields. In the civilian field, pyrotechnics can help engineers carry out directional blasting of buildings, mountain mining, oil exploration, and blasting molding; in the military field, pyrotechnics can be seen in conventional ammunition, missiles, strategic nuclear weapons, and spacecraft. Pyrotechnics can complete the launch ignition of weapons and equipment and the detonation of ammunition. In spacecraft, pyrotechnics are used to complete the separation, boosting, and recovery landing of rocket boosters. Acupuncture pyrotechnics and electric pyrotechnics are the two most common pyrotechnics. Electric pyrotechnics have the characteristics of small ignition energy, high instantaneousness, and good synchronization. They are most widely used in civilian blasting and weapon devices. Among them, bridge wire electric pyrotechnics have the characteristics of small ignition energy, rapid action, and easy performance control, and are the most widely used. The resistance of the bridge wire is generally a few ohms to more than ten ohms. For the measurement of general small resistance, two methods can be used: pulse instantaneous large current measurement or small current measurement. Due to the particularity of pyrotechnics, the maximum current value of the DC resistance test does not exceed 10mA or 10% of the maximum non-ignition current of the pyrotechnics, whichever is smaller. However, the constant current source of the existing bridge wire pyrotechnics test circuit is easily affected by external abnormal interference or outputs abnormally large current when the constant current source function is abnormal. Summary of the invention

[0003] The purpose of the present invention is to solve the technical problem that the constant current source in the prior art is susceptible to abnormal external interference or outputs abnormally large current when the constant current source malfunctions, and to provide a constant current source with overcurrent protection.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention discloses a constant current source for overcurrent protection, comprising a mirror image constant current source and a controllable precision voltage reference connected in series; the mirror image constant current source is connected to a current detection unit for current detection and outputting a detection signal; the current detection unit is pre-set with an overcurrent protection threshold current; the current detection unit is connected to a disconnection control unit; the disconnection control unit signal is connected to an external enable terminal for receiving an external enable terminal signal; the disconnection control unit is pre-set with an external enable threshold; the disconnection control unit is connected to the controllable precision voltage reference; the mirror image constant current source is connected to an external power supply; after the detection signal and the external enable terminal signal pass through the disconnection control unit, the disconnection control unit sends a control signal to control the controllable precision voltage reference to enable, thereby realizing the on-off control of the mirror image constant current source.

[0005] Further improvements are: The controllable precision voltage reference comprises a voltage regulator tube D 1 and N-type field effect transistor T 1 The parallel circuit is connected with an operational amplifier U 1 ; When the enable terminal EN is at a low level, the N-type field effect transistor T 1 Shutdown, Zener D 1 Normal operation, the operational amplifier U 1 The voltage at the non-inverting input terminal is the voltage regulator tube D 1 Voltage regulation value V 1 ; When the enable terminal EN is high, the N-type field effect transistor T 1 Conducting, Zener diode D 1 is short-circuited, U 1 The voltage at the non-inverting input is approximately zero.

[0006] The controllable precision voltage reference includes a plurality of resistors arranged in the circuit, and the voltage regulator tube D is adjusted. 1 The output current of the mirror constant current source is adjusted by adjusting the resistance value of the resistor.

[0007] The mirror image constant current source includes an operational amplifier U connected to the controllable precision voltage reference 2 , operational amplifier U 2 N-type field effect transistors T are connected in series 2 、Operational amplifier U 3 and P-type field effect transistor T 3 ; When the enable terminal EN is at a low level, the mirror constant current source outputs current: when the enable terminal EN is at a high level, the mirror constant current source outputs current 0.

[0008] The current detection unit includes an operational amplifier U connected in series 4 and operational amplifier U 5 ; The operational amplifier U4 and operational amplifier U 5 Several resistors are connected.

[0009] The breaking control unit includes a voltage regulator tube D 2 , the voltage regulator tube D 2 Connected with operational amplifier U 6 , the operational amplifier U 6 Connected with parallel operational amplifier U 7 、Operational amplifier U 8 and operational amplifier U 9 ; The operational amplifier U 7 Connected with comparator U 12 ; The operational amplifier U 8 Connected with comparator U 10 ; The operational amplifier U 9 Connected with comparator U 11 The comparator U 10 Connected with diode D 3 The comparator U 11 Connected with N-type field effect transistor T 4 The comparator U 12 , Comparator U 10 and comparator U 11 Both are connected with comparator U 13 .

[0010] The disconnection control unit includes a plurality of resistors arranged in the circuit, and by adjusting the voltage regulator tube D 2 The resistance value of the resistor adjusts the overcurrent protection threshold current and the external enable threshold.

[0011] The disconnection control unit is connected to a fault indication unit for providing a visible or audible fault indication when an overcurrent fault or an abnormal external enable signal is detected.

[0012] The fault indication unit includes a light emitting diode or a buzzer. When the disconnection control unit sends a control signal to cut off the mirror constant current source, the fault indication unit is activated to indicate the fault state in a light emitting or sounding manner.

[0013] It includes an interface for adjusting parameters, which is a physical button, a knob or a digital communication interface, through which the output current of the mirror constant current source, the overcurrent protection threshold current and the external enable threshold are adjusted.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a constant current source with overcurrent protection, which is composed of a controllable precision voltage reference, a mirror image constant current source, a current detection unit and an on-off control unit. The controllable precision voltage reference and the mirror image constant current source constitute the basic structure of the precision constant current source; the current detection unit completes the detection of the output current of the constant current source, and after the detection signal and the external enable terminal signal pass through the on-off control unit, a control signal is generated to control the precision voltage reference to enable, thereby realizing the on-off control of the constant current source. In the precision constant current source with overcurrent protection of the invention, the constant current source output adopts a high-precision voltage reference and a mirror image constant current source structure, can output a high-precision current reference, and can adjust the output current of the constant current source by adjusting the resistance value of the precision resistor. Compared with the three-terminal regulator type constant current source, the output current accuracy and temperature coefficient of the invention are higher, and can be used in the field of precision measurement. The output voltage of the internal current detection unit of the invention is proportional to the size of the constant current source, and the real-time monitoring of the output of the constant current source can be realized through the current detection unit. At the same time, the overcurrent protection current threshold of the constant current source can be set by adjusting the amplification factor of the current detection unit or the flip threshold voltage of the on-off control unit comparator. The output signal of the current detection unit and the external enable signal are passed through the disconnect control unit to generate a control signal to control the precision voltage reference enable terminal, and the voltage reference enable terminal is valid at a low level. When the output signal of the current detection unit exceeds the overcurrent protection current threshold, the disconnect control unit outputs a high level and maintains the high level at the same time. At this time, the voltage reference is turned off, the constant current source is turned off, and the output maintains high impedance; only when the external enable terminal signal inputs a positive pulse signal, the disconnect control unit output becomes a low level and maintains a low level at the same time. At this time, the voltage reference is turned on and the constant current source output returns to normal. The constant current source with overcurrent protection of the present invention has the advantages of high precision, high sensitivity, high reliability, etc., and can be used in applications such as bridge wire type electric ignition product resistance testing that have extremely high requirements for output current accuracy and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 It is a principle block diagram of a constant current source for overcurrent protection in the present invention; Figure 2 A schematic diagram of a controllable voltage reference, a mirror image constant current source and a current detection unit of a constant current source for overcurrent protection in the present invention; Figure 3 The present invention is a schematic diagram of a disconnection control unit of a constant current source for overcurrent protection.

[0017] Among them: 1- mirror image constant current source; 2- controllable precision voltage reference; 3- current detection unit; 4- disconnection control unit; 5- external load. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings: See also Figure 1The embodiment of the present invention discloses a constant current source for overcurrent protection, comprising a mirror image constant current source 1 and a controllable precision voltage reference 2 connected in series; the mirror image constant current source 1 is connected to a current detection unit 3 for current detection and outputting a detection signal; the current detection unit 3 is pre-set with an overcurrent protection threshold current; the current detection unit 3 is connected to a disconnection control unit 4; the disconnection control unit 4 is signal-connected with an external enable terminal for receiving an external enable terminal signal; the disconnection control unit 4 is pre-set with an external enable threshold; the disconnection control unit 4 is connected to the controllable precision voltage reference 2; the mirror image constant current source 1 is connected to an external power supply; after the detection signal and the external enable terminal signal pass through the disconnection control unit 4, the disconnection control unit 4 sends a control signal to control the controllable precision voltage reference 2 to enable, thereby realizing the on-off control of the mirror image constant current source 1. The disconnection control unit 4 is connected to a fault indication unit for providing a visible or audible fault indication when an overcurrent fault or an abnormal external enable signal is detected. The fault indication unit includes a light emitting diode or a buzzer. When the disconnection control unit 4 sends a control signal to cut off the mirror constant current source 1, the fault indication unit is activated to indicate the fault state by emitting light or sound. An interface for adjusting parameters is included, and the interface is a physical button, a knob or a digital communication interface, through which the output current, the overcurrent protection threshold current and the external enable threshold of the mirror constant current source 1 are adjusted.

[0022] The constant current source with overcurrent protection of the present invention is composed of a controllable precision voltage reference, a mirror image constant current source, a current detection unit and an on / off control unit. The controllable precision voltage reference and the mirror image constant current source constitute the basic structure of the precision constant current source; the current detection unit completes the output current detection of the constant current source, and after the detection signal and the external enable terminal signal pass through the on / off control unit, a control signal is generated to control the precision voltage reference to enable, thereby realizing the on / off control of the constant current source.

[0023] The working mode of the constant current source with overcurrent protection of the present invention is as follows: set the constant current source output current I according to the use requirements O , Overcurrent protection threshold current I TH and the external enable threshold V TH . The constant current source power supply is connected to V CC , external enable terminal V reset Connect low level, the current output end of the constant current source is connected to the external load, and the ground end of the external load is connected to the constant current source ground.

[0024] After the circuit is powered on, the controllable voltage reference enable terminal EN is low level, and the voltage reference output V ref , the constant current source works normally; when the constant current source causes the output current I O Increases and exceeds the overcurrent protection threshold current I THWhen the monitoring signal of the current detection unit is turned to high level through the disconnection control unit, EN is locked to high level, the voltage reference output is zero, and the constant current source is turned off; when the external enable terminal signal inputs a positive voltage pulse signal and the voltage is greater than the threshold V TH When the enable signal EN flips to a low level, EN locks the low level, the voltage reference is turned on again, and the constant current source resumes normal operation. The detailed description of each functional unit is as follows: See also Figure 2 , is the schematic diagram of the controllable precision voltage reference 2, including the voltage regulator tube D 1 and N-type field effect transistor T 1 The parallel circuit is connected with an operational amplifier U 1 ; When the enable terminal EN is at a low level, the N-type field effect transistor T 1 Shutdown, Zener D 1 Normal operation, the operational amplifier U 1 The voltage at the non-inverting input terminal is the voltage regulator tube D 1 Voltage regulation value V 1 ; When the enable terminal EN is high, the N-type field effect transistor T 1 Conducting, Zener diode D 1 is short-circuited, U 1 The voltage at the non-inverting input is approximately zero.

[0025] By Zener tube D 1 , N-type field effect transistor T 1 、Operational amplifier U 1 and resistor R 1 ~R 5 When the enable terminal EN is at a low level, T 1 Shutdown, Zener D 1 Normal operation, the voltage at the common-mode input of the operational amplifier U1 is the voltage value of the voltage regulator V 1 , operational amplifier output voltage:

[0026] When the enable terminal EN is high, T 1 Conducting, Zener diode D 1 is short-circuited, U 1 The voltage at the non-inverting input terminal is approximately zero, and the output voltage Vref≈0V.

[0027] See also Figure 2 , is a schematic diagram of a mirror image constant current source 1, including an operational amplifier U connected to the controllable precision voltage reference 2 2 , operational amplifier U 2 N-type field effect transistors T are connected in series 2 、Operational amplifier U3 and P-type field effect transistor T 3 ; When the enable terminal EN is at a low level, the mirror constant current source 1 outputs current: when the enable terminal EN is at a high level, the mirror constant current source 1 outputs current 0.

[0028] By operational amplifier U 2 、Operational amplifier U 3 , N-type field effect transistor T 2 , P-type field effect transistor T 3 , resistor R 6 ~R 8 Composition. Constant current source output current:

[0029] Therefore, when the enable terminal EN is at a low level, the constant current source output current is:

[0030] When the enable terminal EN is at a high level, the constant current source output current is 0.

[0031] The schematic diagram of the current detection unit is as follows: Figure 2 As shown, the operational amplifier U 4 、Operational amplifier U 5 , resistor R 9 ~R 15 Composition, where R 10 =R 11 , R 12 =R 13 . Current detection unit output voltage:

[0032] See also Figure 3 , is the schematic diagram of the disconnection control unit 4, including the voltage regulator tube D 2 , the voltage regulator tube D 2 Connected with operational amplifier U 6 , the operational amplifier U 6 Connected with parallel operational amplifier U 7 、Operational amplifier U 8 and operational amplifier U 9 ; The operational amplifier U 7 Connected with comparator U 12 ; The operational amplifier U 8 Connected with comparator U 10 ; The operational amplifier U 9 Connected with comparator U 11 The comparator U 10 Connected with diode D 3 The comparator U 11Connected with N-type field effect transistor T 4 The comparator U 12 , Comparator U 10 and comparator U 11 Both are connected with comparator U 13 .

[0033] By Zener tube D 2 、Operational amplifier U 6 ~U 9 , Comparator U 10 ~U 13 、Diode D 3 , N-type field effect transistor T 4 and resistor R 16 ~R 35 Operational amplifier U 6 The voltage at the non-inverting input terminal is the voltage regulator tube D 2 Voltage regulation value V 2 , operational amplifier output voltage:

[0034] therefore,

[0035]

[0036]

[0037] After the circuit is powered on, the external reset signal V rese t voltage is less than V ref3 , comparator U 10 Output low level, transistor T 4 In the off state. The current detection unit output voltage V cur Less than V ref2 , comparator U 10 Output low level, comparator U 12 The voltage at the in-phase terminal is less than V ref1 , comparator U 12 Output low level, U 12 Through the resistor R 32 In the positive feedback state, the output is locked at a low level, so U 13 The output and EN terminal output maintain a low level, the controllable voltage reference works normally, and the constant current source output is normal.

[0038] Cut off the overcurrent protection signal V in the control unit cur and external reset signal V reset The working modes are described as follows: When the current detection unit output voltage V cur Greater than V ref2When the comparator U 10 The output flips to high level, and the comparator U 12 The voltage at the in-phase terminal is greater than V ref1 , U 12 The output flips to high level, due to U 12 In the positive feedback state, the output is locked at a high level; afterwards, if V cur Voltage is less than V ref2 , comparator U 10 The output flips to low level, but due to the diode D 3 The reverse bias effect, U 12 The output still maintains a high level. Therefore, U 13 The output and EN terminal output maintain high level, the controllable voltage reference is turned off, and the constant current source output is turned off. reset Input pulse signal, and the pulse amplitude is greater than V ref3 When the comparator U 11 Output positive pulse, which will 4 The transistor is turned on for a certain period of time and then turned off. 4 When turned on, the comparator U 12 The in-phase terminal flips from high level to low level, U 12 The output switches from high level to low level, and U 12 Output maintains low level, U 13 The output and EN terminal output flip from high level to low level, and U 13 The output maintains a low level, the controllable voltage reference resumes normal operation, and the constant current source output resumes normal.

[0039] For the constant current source output current I O , Overcurrent protection threshold current I TH and the external enable threshold V TH The setup instructions are as follows: Constant current source output current I O :By adjusting the voltage regulator tube D 1 Voltage stabilization value, resistor R 4 ~R 8 The resistance value can adjust the output current of the constant current source.

[0040] Overcurrent protection threshold current I TH :When V cur Greater than V ref2 When the overcurrent protection is enabled, at this time: >

[0041]

[0042] By adjusting the voltage regulator D 2Voltage stabilization value, resistor R 9 , R 10 , R 12 , R 14 , R 15 , R 17 , R 18 , R 21 , R 22 The resistance value can adjust the overcurrent protection current threshold.

[0043] External reset enable threshold V TH :When the external reset signal V reset The pulse amplitude is greater than V ref3 When the reset function works, at this time:

[0044] By adjusting the voltage regulator D 2 Voltage stabilization value, resistor R 17 , R 18 , R 23 , R 24 The resistor value can adjust the external reset enable threshold.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A constant current source for overcurrent protection, characterized in that: The invention comprises a mirror image constant current source (1) and a controllable precision voltage reference (2) connected in series; the mirror image constant current source (1) is connected to a current detection unit (3) for performing current detection and outputting a detection signal; the current detection unit (3) is pre-set with an overcurrent protection threshold current; the current detection unit (3) is connected to a disconnection control unit (4); the disconnection control unit (4) is signal-connected with an external enable terminal for receiving an external enable terminal signal; the disconnection control unit (4) is pre-set with an external enable threshold; the disconnection control unit (4) is connected to the controllable precision voltage reference (2); the mirror image constant current source (1) is connected to an external power supply; after the detection signal and the external enable terminal signal pass through the disconnection control unit (4), the disconnection control unit (4) sends a control signal to control the controllable precision voltage reference (2) to enable, thereby realizing on-off control of the mirror image constant current source (1).

2. The constant current source for overcurrent protection according to claim 1, characterized in that: The controllable precision voltage reference (2) comprises a parallel circuit consisting of a voltage regulator tube D1 and an N-type field effect transistor T1; the parallel circuit is connected to an operational amplifier U1; when the enable terminal EN is at a low level, the N-type field effect transistor T1 is turned off, the voltage regulator tube D1 works normally, and the voltage at the common-mode input terminal of the operational amplifier U1 is the voltage regulation value V1 of the voltage regulator tube D1; when the enable terminal EN is at a high level, the N-type field effect transistor T1 is turned on, the voltage regulator tube D1 is short-circuited, and the voltage at the common-mode input terminal of U1 is approximately zero.

3. The constant current source for overcurrent protection according to claim 2, characterized in that: The controllable precision voltage reference (2) comprises a plurality of resistors arranged in a circuit, and the output current of the mirror image constant current source (1) is adjusted by adjusting the resistance values ​​of the voltage regulator tube D1 and the resistors.

4. The constant current source for overcurrent protection according to claim 1, characterized in that: The mirror image constant current source (1) comprises an operational amplifier U2 connected to the controllable precision voltage reference (2), wherein the operational amplifier U2 is connected in series with an N-type field effect transistor T2, an operational amplifier U3 and a P-type field effect transistor T3 in sequence; when the enable terminal EN is at a low level, the mirror image constant current source (1) outputs a current; when the enable terminal EN is at a high level, the mirror image constant current source (1) outputs a current of 0.

5. The constant current source for overcurrent protection according to claim 1, characterized in that: The current detection unit (3) comprises an operational amplifier U4 and an operational amplifier U5 connected in series; the operational amplifier U4 and the operational amplifier U5 are both connected to a plurality of resistors.

6. The constant current source for overcurrent protection according to claim 1, characterized in that: The disconnection control unit (4) comprises a voltage regulator tube D2, the voltage regulator tube D2 is connected to an operational amplifier U6, the operational amplifier U6 is connected to an operational amplifier U7, an operational amplifier U8 and an operational amplifier U9 connected in parallel; the operational amplifier U7 is connected to a comparator U 12 The operational amplifier U8 is connected to a comparator U 10 The operational amplifier U9 is connected to a comparator U 11 The comparator U 10 A diode D3 is connected; the comparator U 11 Connected with an N-type field effect transistor T4; the comparator U 12 , Comparator U 10 and comparator U 11 Both are connected with comparator U 13 .

7. The constant current source for overcurrent protection according to claim 6, characterized in that: The disconnection control unit (4) comprises a plurality of resistors arranged in the circuit, and the magnitude of the overcurrent protection threshold current and the external enabling threshold is adjusted by adjusting the resistance values ​​of the voltage regulator tube D2 and the resistors.

8. The constant current source for overcurrent protection according to claim 1, characterized in that: The disconnection control unit (4) is connected to a fault indication unit for providing a visible or audible fault indication when an overcurrent fault or an abnormal external enable signal is detected.

9. The constant current source for overcurrent protection according to claim 8, characterized in that: The fault indication unit comprises a light emitting diode or a buzzer, and when the disconnection control unit (4) sends a control signal to cut off the mirror image constant current source (1), the fault indication unit is activated to indicate the fault state in a light emitting or sound emitting manner.

10. The constant current source for overcurrent protection according to claim 1, characterized in that: An interface for adjusting parameters is included, wherein the interface is a physical button, a knob or a digital communication interface, and the output current, the overcurrent protection threshold current and the external enable threshold of the mirror constant current source (1) are adjusted through the interface.

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