Field-effect tube low-current output circuit with Hall current detection function

Abstract

The utility model provides a field effect transistor low-current output circuit with Hall current detection, which is used for solving the problems that a special current sensor is large in size, inconvenient to install, low in low-current detection precision, difficult to be applied to a small-size circuit board, low in cost and the like. And an existing low-current and high-end MOS tube driving circuit is complex, the cost is relatively high, and the reliability is limited to a certain extent. Comprising a field effect transistor circuit, a driving circuit, a detection circuit, an output feedback circuit and a protection circuit. According to the utility model, a photoelectric effect driving mode is adopted, no extra power supply is needed, and the driving cost is reduced. Meanwhile, the driving circuit has high sensitivity and stability, reliable work of the field effect transistor can be guaranteed, and the driving circuit is isolated from a main output circuit of the field effect transistor.

Description

Technical Field

[0001] The utility model relates to the field of output circuits of field effect tubes, in particular to a field effect tube small current output circuit with Hall current detection. Background Art

[0002] When the MOS tube driving circuit is working, the operating voltage and operating current of the components should be within the rated range. Exceeding the rated range will cause the components to fail and fail to work. Therefore, the MOS tube driving circuit often requires a current detection module to detect whether the operating current is within the rated range. In the prior art, dedicated current sensors are large in size and are usually suitable for situations with large currents. Due to the inconvenience of installation and low detection accuracy of small currents, it is difficult to use them on small circuit boards. The existing small current, high-end MOS tube driving circuit has a complex driving circuit, high cost, and certain reliability limitations. Therefore, it is necessary to provide a low-cost, high-reliability field effect tube driving circuit. Utility Model Content

[0003] The purpose of the utility model is to solve the technical problems that the existing dedicated current sensor is large in size, inconvenient to install, has low detection accuracy for small current, is difficult to use on a small circuit board, and the existing small current, high-end MOS tube drive circuit is complex, costly, and reliability is subject to certain restrictions. A field effect tube small current output circuit with Hall current detection is proposed.

[0004] In order to solve the above technical problems, the technical solutions provided by the utility model are as follows:

[0005] A field effect tube small current output circuit with Hall current detection, which is special in that it includes a field effect tube circuit, a driving circuit, a detection circuit, an output feedback circuit and a protection circuit;

[0006] The input end of the driving circuit is connected to the external control port, and the output end is connected to the input end of the field effect tube circuit; the power input end of the field effect tube circuit is used to connect to the main power supply, and the output end is respectively connected to the input high end of the detection circuit and the input end of the output feedback circuit; the detection circuit is used to perform Hall current detection on the output end of the field effect tube circuit and output a voltage signal, the input low end of the detection circuit is connected to the main output loop, and the signal output end is connected to the input end of the protection circuit; the output end of the protection circuit is connected to the input end of the driving circuit, and the protection circuit is used to compare the voltage signal output by the detection circuit with the set protection voltage, and block the driving circuit when the voltage signal is greater than the protection voltage, thereby cutting off the main output loop; the output end of the output feedback circuit is connected to an external display device, and is used to feed back the conduction signal of the main output loop;

[0007] The driving circuit includes a MOS tube Q2 and a photocoupler U1, wherein the G pole of the MOS tube Q2 is connected to the external control port and the output end of the protection circuit, the D pole is connected to the input low end of the photocoupler U1, and the S pole is grounded; the input high end of the photocoupler U1 is connected to the power supply VCC;

[0008] The field effect tube circuit includes a field effect tube Q1, the G pole of the field effect tube Q1 is connected to the output high end of the photocoupler U1, the D pole is connected to the main power supply, the S pole is connected to the output low end of the photocoupler U1, and the S pole of the field effect tube Q1 serves as the output end of the field effect tube circuit.

[0009] Furthermore, the driving circuit also includes a resistor R4, a resistor R2, and a resistor R3. The G pole of the MOS tube Q2 is connected to one end of the resistor R4, and the other end of the resistor R4 is connected to an external control port; the input high end of the photocoupler U1 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to a power supply VCC; the output high end of the photocoupler U1 is connected to one end of the resistor R3, and the other end of the resistor R3 is connected to the G pole of the field effect tube Q1.

[0010] Furthermore, the field effect transistor circuit also includes a resistor R1 and a capacitor C1 connected in series; the other end of the resistor R1 is connected to the D pole of the field effect transistor Q1, and the other end of the capacitor C1 is connected to the S pole of the field effect transistor Q1.

[0011] Furthermore, the detection circuit includes a current sensor U2, a diode D2 and a capacitor C2; the two positive input terminals IP+ of the current sensor U2 are both connected to the S pole of the field effect transistor Q1; the two negative input terminals IP- of the current sensor U2 are both connected to the positive pole of the diode D2, and the negative pole of the diode D2 is connected to the main output;

[0012] The power supply end of the current sensor U2 is used to connect to the power supply VCC; the power supply end of the current sensor U2 is also connected to one end of the capacitor C2, and the other end of the capacitor C2 is grounded, which is used to stabilize the voltage of the power supply end; the ground end of the current sensor U2 is grounded, and the zero current reference signal output end VZCR is suspended;

[0013] The signal output terminal of the current sensor U2 is connected to the input terminal of the protection circuit.

[0014] Further, the protection circuit includes a comparator U4, a resistor R10, a resistor R12, a resistor R13, a resistor R11 and a capacitor C3, a capacitor C4; the positive input terminal IN+ of the comparator U4 is connected to the reference voltage VREF through the resistor R10; the negative input terminal IN- of the comparator U4 is connected to one end of the resistor R12 and one end of the resistor R13, and the other end of the resistor R12 is connected to the signal output end of the current sensor U2; the other end of the resistor R13 is grounded; the power supply end of the comparator U4 is connected to the power supply VCC; the power supply end of the comparator U4 is also connected to one end of the capacitor C3, and the other end of the capacitor C3 is grounded for stabilizing the voltage at the power supply end; the ground end of the comparator U4 is grounded;

[0015] The output end of the comparator U4 is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the G pole of the MOS tube Q2; the other end of the resistor R11 is also connected to one end of the capacitor C4, and the other end of the capacitor C4 is grounded.

[0016] Furthermore, the output feedback circuit includes a voltage zener diode D1, a resistor R5, a resistor R6, a resistor R7, a resistor R9 and a photocoupler U3; the cathode of the voltage zener diode D1 is connected to the S pole of the field effect transistor Q1; the anode of the voltage zener diode D1 is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the input high end of the photocoupler U3; the input low end of the photocoupler U3 is grounded; the resistors R5, R9 and R6 are connected in parallel;

[0017] The output low end of the photocoupler U3 is grounded, and the output high end is connected to the resistor R7, and the other end of the resistor R7 is connected to the isolated power supply; the output high end of the photocoupler U3 is used to connect to an external display device.

[0018] Furthermore, the driving circuit further includes a resistor R8; one end of the resistor R8 is connected to the S pole of the MOS tube Q2, and the other end is connected to the G pole.

[0019] Beneficial effects of the utility model:

[0020] 1. The utility model adopts the driving mode of photoelectric effect, which does not require additional power supply and reduces the driving cost. At the same time, the driving circuit has high sensitivity and stability, which can ensure the reliable operation of the field effect tube and isolate the driving circuit from the main output circuit of the field effect tube.

[0021] 2. The utility model has a wide detection range. The Hall effect current sensor in the detection circuit can achieve a current detection range of 0 to 5A. The Hall effect current sensor can detect the magnetic field strength around the wire without touching the wire, thereby obtaining current information and monitoring the output current in real time. The amplifier and filter inside the current sensor can amplify the detected weak signal and filter out noise, thereby improving the detection accuracy and accurately obtaining current information.

[0022] 3. The protection circuit of the utility model can achieve fast protection response. When the output current exceeds the set protection point, the output circuit can be quickly cut off to avoid damage to circuit components due to overcurrent. The protection circuit also has good flexibility and the protection point can be set arbitrarily according to needs.

[0023] 4. The utility model is well suited for low current output detection within 5A. Through reasonable design and optimization of the circuit, it can maintain stability and reliability under low current output conditions. It is of great significance for some applications that require stable low current output. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural block diagram of an embodiment of a field effect tube small current output circuit with Hall current detection of the utility model;

[0025] Figure 2 This is a circuit connection diagram of an embodiment of a field effect tube small current output circuit with Hall current detection of the utility model (the output feedback circuit is not shown);

[0026] Figure 3 This is a field effect tube circuit connection diagram of an embodiment of a field effect tube small current output circuit with Hall current detection of the utility model;

[0027] Figure 4 This is a detection circuit connection diagram of an embodiment of a field effect tube small current output circuit with Hall current detection of the utility model;

[0028] Figure 5 This is a connection diagram of a protection circuit and a driving circuit of an embodiment of a field effect tube small current output circuit with Hall current detection of the utility model;

[0029] Figure 6 The utility model is an output feedback circuit connection diagram of an embodiment of a field effect tube small current output circuit with Hall current detection. DETAILED DESCRIPTION

[0030] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0031] A field effect tube small current output circuit with Hall current detection, such as Figure 1 As shown, it includes a field effect tube circuit, a driving circuit, a detection circuit, an output feedback circuit and a protection circuit; the input end of the driving circuit is connected to the external control port, and the output end is connected to the input end of the field effect tube circuit; the power input end of the field effect tube circuit is used to connect the main power supply, and the output end is respectively connected to the input high end of the detection circuit and the input end of the output feedback circuit; the detection circuit is used to perform Hall current detection on the output end of the field effect tube circuit and output a voltage signal, the input low end of the detection circuit is connected to the main output loop, and the signal output end is connected to the input end of the protection circuit; the output end of the protection circuit is connected to the input end of the driving circuit, and the protection circuit is used to compare the voltage signal output by the detection circuit with the set protection voltage, and when the voltage signal is greater than the protection voltage, the driving circuit is blocked, thereby cutting off the main output loop; the output end of the output feedback circuit is connected to an external display device, and is used to feed back the conduction signal of the main output loop;

[0032] like Figure 2 As shown, the driving circuit includes a MOS tube Q2, an optocoupler U1, a resistor R4, a resistor R8, a resistor R2 and a resistor R3, the external control port is connected to one end of the resistor R4, and the other end of the resistor R4 is connected to the G pole of the MOS tube Q2. The S pole of the MOS tube Q2 is grounded, and the D pole is connected to the input low end (pin 3) of the optocoupler U1. The resistor R8 is connected in parallel between the S pole and the G pole of the MOS tube Q2, which can effectively ensure the normal operation of the MOS tube Q1. The input high end (pin 1) of the optocoupler U1 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the 5V power supply VCC for power supply. The output high end (pin 6) of the optocoupler U1 is connected to one end of the resistor R3, and the other end of the resistor R3 is connected to the G pole of the field effect tube Q1. The output low end (pin 4) of the optocoupler U1 is connected to the S pole of the field effect tube Q1. In this embodiment, the photocoupler U1 uses TLP3906, which is a photocoupler device specially used to drive MOS. It adopts the high-end driving mode of photoelectric effect, can convert optical signals into electrical signals, reduce driving costs, and improve reliability. At the same time, it has high sensitivity and stability, can ensure the reliable operation of the field effect tube, and isolates the driving circuit from the main output circuit of the field effect tube.

[0033] like Figure 3 As shown, the field effect tube circuit includes a field effect tube Q1, a resistor R1 and a capacitor C1 connected in series, the D pole of the field effect tube Q1 is connected to the main power port DO_IN, the other end of the resistor R1 is connected to the D pole of the field effect tube Q1, the capacitor C1 is connected to the S pole of the field effect tube Q1, and the S pole of the field effect tube Q1 is connected to the input end of the detection circuit. In this embodiment, the field effect tube Q1 uses NCEP02525K, which is an N-channel MOS tube.

[0034] like Figure 4 As shown, the detection circuit includes a current sensor U2, a diode D2 and a capacitor C2. In the present embodiment, the current sensor U2 is a CC6920SO-5A Hall effect current sensor, which can effectively measure direct current or alternating current, has high performance, high precision, and good linearity and temperature stability. The two positive input terminals IP+ of the current sensor U2 are both connected to the S pole of the field effect tube Q1. The two negative input terminals IP- of the current sensor U2 are connected to the positive pole of the diode D2, and the negative pole of the diode D2 is connected to the main output DO_OUT3 / DO1_IN. The power supply terminal of the current sensor U2 is connected to the 5V power supply VCC. The power supply terminal of the current sensor U2 is also connected to one end of the capacitor C2, and the other end of the capacitor C2 is grounded for stabilizing the voltage at the power supply terminal. The ground terminal of the current sensor U2 is grounded, and the zero current reference signal output terminal VZCR is suspended. The signal output terminal of the current sensor U2 is connected to the input terminal of the protection circuit. The current sensor U2 can realize real-time monitoring of the output circuit and improve the safety of the circuit. The Hall effect current sensor can detect the magnetic field strength around the wire without contacting the wire, thereby obtaining current information; the current sensor U2 has an amplifier and a filter inside, which can amplify the detected weak signal and filter out noise to improve the detection accuracy. In this embodiment, the normal working current of the output end of the current sensor U2 is 2A, and the protection point is set to 2.5A. When the output current of the current sensor U2 exceeds the protection point, the voltage VOUT_03 at the signal output end of the current sensor U2 is input to the comparator U4 of the protection circuit, and the comparator U4 controls the MOS tube Q2 to disconnect through the output signal, thereby cutting off the main output circuit.

[0035] like Figure 5As shown, the protection circuit can achieve fast protection response and ensure stable operation of the circuit. The protection circuit includes a comparator U4, a resistor R10, a resistor R12, a resistor R13, a resistor R11, a capacitor C3, and a capacitor C4. The positive input terminal IN+ of the comparator U4 is connected to one end of the resistor R10, and the other end of the resistor R10 is connected to the reference voltage VREF of 1.25V. The negative input terminal IN- of the comparator U4 is connected to one end of the resistor R12 and one end of the resistor R13, and the other end of the resistor R12 is connected to the signal output end of the current sensor U2. The other end of the resistor R13 is grounded. The power supply terminal of the comparator U4 is connected to a 5V power supply VCC. The power supply terminal of the comparator U4 is also connected to one end of the capacitor C3, and the other end of the capacitor C3 is grounded to stabilize the voltage at the power supply terminal. The ground terminal of the comparator U4 is grounded. The output terminal of the comparator U4 is connected to the resistor R11, and the other end of the resistor R11 is connected to the G pole of the MOS tube Q2. The other end of the resistor R11 is also connected to the capacitor C4, and the other end of the capacitor C4 is grounded. In this embodiment, the model used by the comparator U4 is TL331IDBVR. The comparator U4 compares the voltage signal VOUT_03 output by the current sensor U2 with the reference voltage VREF of 1.25V. When the voltage signal VOUT_03 output by the current sensor U2 is lower than the reference voltage VREF, the comparator U4 outputs a high level signal, the MOS tube Q2 remains turned on, and the main output circuit remains in normal operation. When the voltage signal VOUT_03 output by the current sensor U2 exceeds the reference voltage VREF, the comparator U4 outputs a low level signal, the G pole voltage of the MOS tube Q2 is less than the driving voltage of the MOS tube Q2, the MOS tube Q2 is turned off, and then the main output circuit is cut off to avoid damage to the circuit components due to overcurrent. When the main output circuit is disconnected, the current sensor U2 returns to the zero current output state, and the control port charges the capacitor C4 through the resistor R4. When the voltage rises to the driving voltage, the MOS tube Q2 is turned on again, and the main output circuit outputs normally. This process is repeated, and the output circuit enters the hiccup working state.

[0036] like Figure 6As shown, the output feedback circuit includes a voltage stabilizing diode D1, a resistor R5, a resistor R6, a resistor R7, a resistor R9 and a photocoupler U3. The model of the voltage stabilizing diode D1 in this embodiment is MM1Z18W, and the cathode of the voltage stabilizing diode D1 is connected to the S pole of the field effect tube Q1. The anode of the voltage stabilizing diode D1 is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the input high end of the photocoupler U3. The resistor R6 is connected in parallel with the resistor R5 and the resistor R9. The input low end of the photocoupler U3 is grounded. The output low end of the photocoupler U3 is grounded, and the output high end is connected to an external display device. The output high end is also connected to one end of the resistor R7, and the other end of the resistor R7 is connected to a 3.3V isolated power supply. The model of the photocoupler U3 in this embodiment is LTV-817S-TA1-D. When the field effect tube Q1 is turned on, the photocoupler U3 is turned on, and the collector changes from a high level to a low level, and the main output circuit can be known to be turned on through the external display device.

[0037] Working process: First, connect the MOS tube to the microcontroller or other port with output control; the MOS tube Q2 in the driving circuit controls the opening or closing of the field effect tube Q1. When the MOS tube Q2 is turned on, the photocoupler U1 drives the field effect tube Q1 to the on state. When the MOS tube Q2 is turned off, the field effect tube Q1 is turned off synchronously. The field effect tube Q1 is externally connected to the main power port and the detection circuit. The detection circuit is connected to the protection circuit and the output feedback circuit respectively. The detection circuit monitors the output current in real time through the current sensor, and can accurately obtain the current information. When the output current exceeds the set protection point, the comparator in the protection circuit outputs a low-level signal, blocks the control end of the driving circuit, and realizes the protection of the output current. When the field effect tube Q1 is turned on, the output feedback circuit is connected to the external display device to feedback the conduction signal.

Claims

1. A field effect tube low current output circuit with Hall current detection, characterized in that: It includes a field effect tube circuit, a driving circuit, a detection circuit, an output feedback circuit and a protection circuit; The input end of the driving circuit is connected to the external control port, and the output end is connected to the input end of the field effect tube circuit; the power input end of the field effect tube circuit is used to connect to the main power supply, and the output end is respectively connected to the input high end of the detection circuit and the input end of the output feedback circuit; the detection circuit is used to perform Hall current detection on the output end of the field effect tube circuit and output a voltage signal, the input low end of the detection circuit is connected to the main output loop, and the signal output end is connected to the input end of the protection circuit; the output end of the protection circuit is connected to the input end of the driving circuit, and the protection circuit is used to compare the voltage signal output by the detection circuit with the set protection voltage, and block the driving circuit when the voltage signal is greater than the protection voltage, thereby cutting off the main output loop; the output end of the output feedback circuit is connected to an external display device, and is used to feed back the conduction signal of the main output loop; The driving circuit includes a MOS tube Q2 and a photocoupler U1, wherein the G pole of the MOS tube Q2 is connected to the external control port and the output end of the protection circuit, the D pole is connected to the input low end of the photocoupler U1, and the S pole is grounded; the input high end of the photocoupler U1 is connected to the power supply VCC; The field effect tube circuit includes a field effect tube Q1, the G pole of the field effect tube Q1 is connected to the output high end of the photocoupler U1, the D pole is connected to the main power supply, the S pole is connected to the output low end of the photocoupler U1, and the S pole of the field effect tube Q1 serves as the output end of the field effect tube circuit.

2. The field effect tube low current output circuit with Hall current detection according to claim 1, characterized in that: The driving circuit also includes a resistor R4, a resistor R2, and a resistor R3. The G pole of the MOS tube Q2 is connected to one end of the resistor R4, and the other end of the resistor R4 is connected to an external control port; the input high end of the photocoupler U1 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to a power supply VCC; the output high end of the photocoupler U1 is connected to one end of the resistor R3, and the other end of the resistor R3 is connected to the G pole of the field effect tube Q1.

3. The field effect tube low current output circuit with Hall current detection according to claim 2, characterized in that: The field effect tube circuit further includes a resistor R1 and a capacitor C1 connected in series; the other end of the resistor R1 is connected to the D pole of the field effect tube Q1, and the other end of the capacitor C1 is connected to the S pole of the field effect tube Q1.

4. The field effect tube low current output circuit with Hall current detection according to claim 2, characterized in that: The detection circuit includes a current sensor U2, a diode D2 and a capacitor C2; the two positive input terminals IP+ of the current sensor U2 are connected to the S pole of the field effect transistor Q1; the two negative input terminals IP- of the current sensor U2 are connected to the positive pole of the diode D2, and the negative pole of the diode D2 is connected to the main output; The power supply end of the current sensor U2 is used to connect to the power supply VCC; the power supply end of the current sensor U2 is also connected to one end of the capacitor C2, and the other end of the capacitor C2 is grounded, which is used to stabilize the voltage of the power supply end; the ground end of the current sensor U2 is grounded, and the zero current reference signal output end VZCR is suspended; The signal output terminal of the current sensor U2 is connected to the input terminal of the protection circuit.

5. The field effect tube low current output circuit with Hall current detection according to claim 4, characterized in that: The protection circuit includes a comparator U4, a resistor R10, a resistor R12, a resistor R13, a resistor R11, a capacitor C3, and a capacitor C4; the positive input terminal IN+ of the comparator U4 is connected to a reference voltage VREF through the resistor R10; the negative input terminal IN- of the comparator U4 is connected to one end of the resistor R12 and one end of the resistor R13, and the other end of the resistor R12 is connected to the signal output end of the current sensor U2; the other end of the resistor R13 is grounded; the power supply terminal of the comparator U4 is connected to the power supply VCC; the power supply terminal of the comparator U4 is also connected to one end of the capacitor C3, and the other end of the capacitor C3 is grounded to stabilize the voltage at the power supply terminal; the ground terminal of the comparator U4 is grounded; The output end of the comparator U4 is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the G pole of the MOS tube Q2; the other end of the resistor R11 is also connected to one end of the capacitor C4, and the other end of the capacitor C4 is grounded.

6. The field effect tube low current output circuit with Hall current detection according to claim 5, characterized in that: The output feedback circuit includes a voltage zener diode D1, a resistor R5, a resistor R6, a resistor R7, a resistor R9 and a photocoupler U3; the cathode of the voltage zener diode D1 is connected to the S pole of the field effect tube Q1; the anode of the voltage zener diode D1 is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the input high end of the photocoupler U3; the input low end of the photocoupler U3 is grounded; the resistors R5, R9 and R6 are connected in parallel; The output low end of the photocoupler U3 is grounded, and the output high end is connected to the resistor R7, and the other end of the resistor R7 is connected to the isolated power supply; the output high end of the photocoupler U3 is used to connect to an external display device.

7. A field effect tube low current output circuit with Hall current detection according to any one of claims 2 to 6, characterized in that: The driving circuit also includes a resistor R8; One end of the resistor R8 is connected to the S pole of the MOS tube Q2, and the other end is connected to the G pole.

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