Self-adjusting over-current protection circuit
By using a self-adjusting protection threshold circuit and a temperature sampling circuit, the stability problem of the overcurrent protection circuit at different temperatures is solved, achieving reliable overcurrent protection at different temperatures and improving the reliability and shock resistance of the equipment.
Patent Information
- Application Number
- CN202422586515.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-25
- Publication Date
- 2025-11-14
- Estimated Expiration
- 2034-10-25
AI Technical Summary
Existing overcurrent protection circuits cannot achieve stable overcurrent protection at different temperatures, resulting in weak resistance to impact loads at room temperature or damage to switching transistors at high temperatures.
A self-adjusting protection threshold circuit is adopted, combined with a resistor voltage divider circuit and a temperature sampling circuit. The reference voltage is automatically adjusted by a thermistor to adapt to different temperatures, thereby realizing the adaptive adjustment of the overcurrent protection point.
Achieving stable overcurrent protection at different temperatures fully utilizes the current-carrying capacity of the switching transistor, improves equipment reliability and resistance to load shocks, and reduces costs.
Smart Images
Figure CN223553032U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electronic circuits, and in particular to a self-adjusting overcurrent protection circuit. Background Technology
[0002] Existing overcurrent protection circuits based on power switches mainly convert the acquired current into a voltage detection signal, then compare the voltage detection signal with a fixed reference voltage through a comparator, and finally control the switching on and off of the power switch based on the comparison result of the comparator to achieve overcurrent protection.
[0003] The current-carrying capacity of power switching transistors (such as switching transistors) varies at different temperatures, decreasing as the operating temperature rises. If the protection threshold (i.e., reference voltage) of the overcurrent protection circuit is based on the current-carrying capacity of the power switching transistor at room temperature (25°C), then at high temperatures, the current-carrying capacity of the power switching transistor decreases, and the overcurrent protection circuit cannot reliably protect the switching transistor. If the protection threshold of the overcurrent protection circuit is based on the current-carrying capacity of the power switching transistor at high temperatures (such as 100°C), then the current-carrying capacity of the power switching transistor in the low-temperature range will be greatly wasted, resulting in weak resistance to impact loads at room temperature and easy triggering of overcurrent protection.
[0004] In view of the above problems, it is necessary to study a self-adjusting overcurrent protection circuit that can achieve stable overcurrent protection at different temperatures and has reliable overcurrent protection function. Utility Model Content
[0005] The purpose of this invention is to provide a self-adjusting overcurrent protection circuit that can achieve stable overcurrent protection at different temperatures and has reliable overcurrent protection function.
[0006] To achieve the above objectives, the solution of this utility model is:
[0007] A self-adjusting overcurrent protection circuit includes a self-adjusting protection threshold circuit, a current sampling circuit, a comparator circuit, and a switching circuit. The control terminal of the switching circuit is connected to the output terminal of the comparator circuit, the first input terminal of the comparator circuit is connected to the output terminal of the current sampling circuit, and the second input terminal of the comparator circuit is connected to the output terminal of the self-adjusting protection threshold circuit. The self-adjusting protection threshold circuit includes a resistor voltage divider circuit and a temperature sampling circuit, and the output terminals of the resistor voltage divider circuit and the temperature sampling circuit are connected to the output terminal of the self-adjusting protection threshold circuit.
[0008] The resistor voltage divider circuit includes resistors R11 and R12. The first end of resistor R11 is connected to the power supply VDD. The second end of resistor R11 and the first end of resistor R12 are connected to the output terminal of the resistor voltage divider circuit. The second end of resistor R12 is grounded.
[0009] The temperature sampling circuit includes a thermistor RT, which is a negative temperature coefficient thermistor. The first end of the thermistor RT is connected to the output terminal of the temperature sampling circuit, and the second end of the thermistor RT is grounded.
[0010] The current sampling circuit includes a resistor R21 and a capacitor C21. The first end of the resistor R21 is connected to the input terminal of the current sampling circuit, the second end of the resistor R21 and the first end of the capacitor C21 are connected to the output terminal of the current sampling circuit, and the second end of the capacitor C21 is grounded.
[0011] The comparison circuit includes a resistor R31 and a comparator U31. The first end of the resistor R31 and the non-inverting input of the comparator U31 are connected to the second input of the comparison circuit. The second end of the resistor R31 and the output of the comparator U31 are connected to the output of the comparison circuit. The inverting input of the comparator U31 is connected to the first input of the comparison circuit.
[0012] The switching circuit includes a resistor R41 and a switching transistor M41. The first end of the resistor R41 and the gate of the switching transistor M41 are connected to the control terminal of the switching circuit. The drain of the switching transistor M41 is connected to the input terminal of the switching circuit. The source of the switching transistor M41 and the second end of the resistor R41 are connected to the output terminal of the switching circuit.
[0013] The switching circuit also includes a resistor R42, and the first end of the resistor R41 and the gate of the switching transistor M41 are connected to the control terminal of the switching circuit through the resistor R42.
[0014] The self-adjusting overcurrent protection circuit also includes an MCU control circuit and an AND gate circuit. The control terminal of the switching circuit is connected to the output terminal of the comparator circuit through the AND gate circuit. The first input terminal of the AND gate circuit is connected to the output terminal of the comparator circuit. The second input terminal of the AND gate circuit is connected to the MCU control circuit. The output terminal of the AND gate circuit is connected to the control terminal of the switching circuit.
[0015] The AND gate circuit includes resistor R51, resistor R52, diode D51, and AND gate U51; the cathode of diode D51 is connected to the first input terminal of the AND gate circuit, the anode of diode D51 is connected to the first terminal of resistor R52, the second terminal of resistor R52 and the first terminal of resistor R51 are connected to the first input terminal of AND gate U51, the second terminal of resistor R51 is connected to power supply VCC, the second input terminal of AND gate U51 is connected to the second input terminal of the AND gate circuit, and the output terminal of AND gate U51 is connected to the output terminal of the AND gate circuit.
[0016] The self-adjusting overcurrent protection circuit also includes a filter circuit connected to the output of the comparator circuit. The filter circuit includes a resistor R61 and a capacitor C61. The first end of the resistor R61 is connected to the power supply VDD, the second end of the capacitor R61 and the first end of the capacitor C61 are connected to the output of the comparator circuit, and the second end of the capacitor C61 is grounded.
[0017] After adopting the above scheme, the current sampling circuit of this utility model is used to collect the output current of the equipment to be protected. When the sampling voltage output by the current sampling circuit is greater than the reference voltage output by the self-adjusting protection threshold circuit, the signal output by the comparison circuit can control the switch to open, thereby realizing the overcurrent protection function. The self-adjusting protection threshold circuit of this utility model has a temperature sampling circuit. The temperature sampling circuit can collect the ambient temperature or the temperature of the switching transistor and automatically adjust the reference voltage output by the self-adjusting protection threshold circuit according to the temperature change. When the temperature rises, the reference voltage decreases, so that the overcurrent protection point decreases; when the temperature decreases, the reference voltage rises, and the overcurrent protection point rises. This can make full use of the high current carrying capacity of the switching transistor at low temperature, while reliably protecting the switching transistor from damage at high temperature, thereby improving the reliability and resistance to load impact at a lower cost. Attached Figure Description
[0018] Figure 1 This is the circuit schematic diagram of this utility model. Detailed Implementation
[0019] To further explain the technical solution of this utility model, the following detailed description is provided through specific embodiments.
[0020] like Figure 1 As shown, this utility model discloses a self-adjusting overcurrent protection circuit, which includes a self-adjusting protection threshold circuit, a current sampling circuit, a comparator circuit, and a switching circuit; the control terminal of the switching circuit is connected to the output terminal of the comparator circuit, the first input terminal of the comparator circuit is connected to the output terminal of the current sampling circuit, and the second input terminal of the comparator circuit is connected to the output terminal of the self-adjusting protection threshold circuit; the self-adjusting protection threshold circuit includes a resistor voltage divider circuit and a temperature sampling circuit, and the output terminals of the resistor voltage divider circuit and the temperature sampling circuit are connected to the output terminal of the self-adjusting protection threshold circuit.
[0021] In this embodiment of the invention, the current sampling circuit is used to collect the output current of the device to be protected. When the sampling voltage output by the current sampling circuit is greater than the reference voltage output by the self-adjusting protection threshold circuit, the signal output by the comparison circuit can control the switch to open, thereby realizing the overcurrent protection function. The self-adjusting protection threshold circuit of this invention has a temperature sampling circuit. The temperature sampling circuit can collect the ambient temperature or the temperature of the switching transistor and automatically adjust the reference voltage output by the self-adjusting protection threshold circuit according to temperature changes. When the temperature rises, the reference voltage decreases, causing the overcurrent protection point to decrease; when the temperature decreases, the reference voltage rises, causing the overcurrent protection point to rise. This fully utilizes the high current-carrying capacity of the switching transistor at low temperatures, while reliably protecting the switching transistor from damage at high temperatures, thereby improving equipment reliability and resistance to load shocks at a lower cost.
[0022] In an embodiment of this invention, the resistor voltage divider circuit includes resistors R11 and R12. The first terminal of resistor R11 is connected to the power supply VDD, and the second terminals of resistors R11 and R12 are connected to the output terminal of the resistor voltage divider circuit. The second terminal of resistor R12 is grounded. The resistor voltage divider circuit may also include a capacitor C11. The first terminal of capacitor C11 is connected to the output terminal of the resistor voltage divider circuit, and the second terminal of capacitor C11 is grounded. Capacitor C11 can stabilize the output voltage of the resistor voltage divider circuit.
[0023] In an embodiment of this invention, the temperature sampling circuit includes a thermistor RT, which is a negative temperature coefficient thermistor. The first terminal of the thermistor RT is connected to the output terminal of the temperature sampling circuit, and the second terminal of the thermistor RT is grounded. The thermistor RT and capacitor R12 are connected in parallel. When the temperature rises, the resistance of the thermistor RT decreases, causing the reference voltage to decrease and thus lowering the overcurrent protection point. When the temperature decreases, the resistance of the thermistor RT increases, causing the reference voltage to increase and thus raising the overcurrent protection point.
[0024] In an embodiment of this utility model, the current sampling circuit includes a resistor R21 and a capacitor C21. The first end of the resistor R21 is connected to the input end of the current sampling circuit, the second end of the resistor R21 and the first end of the capacitor C21 are connected to the output end of the current sampling circuit, and the second end of the capacitor C21 is grounded.
[0025] In an embodiment of this utility model, the comparison circuit includes a resistor R31 and a comparator U31. The first end of the resistor R31 and the non-inverting input of the comparator U31 are connected to the second input of the comparison circuit. The second end of the resistor R31 and the output of the comparator U31 are connected to the output of the comparison circuit. The inverting input of the comparator U31 is connected to the first input of the comparison circuit.
[0026] In an embodiment of this invention, the switching circuit includes a resistor R41 and a switching transistor M41. The first end of resistor R41 and the gate of switching transistor M41 are connected to the control terminal of the switching circuit. The drain of switching transistor M41 is connected to the input terminal of the switching circuit. The source of switching transistor M41 and the second end of resistor R41 are connected to the output terminal of the switching circuit. When the control terminal level of the switching circuit is high, switching transistor M41 is turned on; when the control terminal level of the switching circuit is low, switching transistor M41 is turned off. The switching circuit may also include a resistor R42. The first end of resistor R41 and the gate of switching transistor M41 are connected to the control terminal of the switching circuit through resistor R42. Resistor R42 can provide current limiting protection to protect switching transistor M41.
[0027] In embodiments of this invention, the self-adjusting overcurrent protection circuit may further include an MCU control circuit and an AND gate circuit. The control terminal of the switching circuit is connected to the output terminal of the comparator circuit via the AND gate circuit. The first input terminal of the AND gate circuit is connected to the output terminal of the comparator circuit, the second input terminal of the AND gate circuit is connected to the MCU control circuit, and the output terminal of the AND gate circuit is connected to the control terminal of the switching circuit. When the MCU control circuit outputs a low level to the AND gate circuit, the AND gate circuit outputs a low level to the switching circuit, causing the switching circuit to turn off. When the MCU control circuit outputs a low level to the AND gate circuit, if the comparator circuit outputs a low level to the AND gate circuit, the AND gate circuit outputs a low level to the switching circuit, causing the switching circuit to turn off; if the comparator circuit outputs a high level to the AND gate circuit, the AND gate circuit outputs a high level to the switching circuit, causing the switching circuit to turn on. The MCU control circuit can act as a master controller.
[0028] In an embodiment of this utility model, the AND gate circuit includes resistor R51, resistor R52, diode D51, and AND gate U51; the cathode of diode D51 is connected to the first input terminal of the AND gate circuit, the anode of diode D51 is connected to the first terminal of resistor R52, the second terminal of resistor R52 and the first terminal of resistor R51 are connected to the first input terminal of AND gate U51, the second terminal of resistor R51 is connected to power supply VCC, the second input terminal of AND gate U51 is connected to the second input terminal of the AND gate circuit, and the output terminal of AND gate U51 is connected to the output terminal of the AND gate circuit.
[0029] In embodiments of this utility model, the self-adjusting overcurrent protection circuit may further include a filter circuit connected to the output terminal of the comparator circuit. The filter circuit includes a resistor R61 and a capacitor C61. The first terminal of the resistor R61 is connected to the power supply VDD, and the second terminal of the capacitor R61 and the first terminal of the capacitor C61 are connected to the output terminal of the comparator circuit. The second terminal of the capacitor C61 is grounded. The filter circuit can stabilize the output level of the comparator circuit.
[0030] The above embodiments and figures are not intended to limit the product form and style of this utility model. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of this utility model.
Claims
1. A self-adjusting overcurrent protection circuit, characterized in that: It includes a self-adjusting protection threshold circuit, a current sampling circuit, a comparison circuit, and a switching circuit; The control terminal of the switching circuit is connected to the output terminal of the comparator circuit, the first input terminal of the comparator circuit is connected to the output terminal of the current sampling circuit, and the second input terminal of the comparator circuit is connected to the output terminal of the self-adjusting protection threshold circuit. The self-adjusting protection threshold circuit includes a resistor voltage divider circuit and a temperature sampling circuit. The output terminals of the resistor voltage divider circuit and the temperature sampling circuit are connected to the output terminal of the self-adjusting protection threshold circuit.
2. The self-adjusting overcurrent protection circuit as described in claim 1, characterized in that: The resistor voltage divider circuit includes resistors R11 and R12. The first end of resistor R11 is connected to the power supply VDD. The second end of resistor R11 and the first end of resistor R12 are connected to the output terminal of the resistor voltage divider circuit. The second end of resistor R12 is grounded.
3. The self-adjusting overcurrent protection circuit as described in claim 1 or 2, characterized in that: The temperature sampling circuit includes a thermistor RT, which is a negative temperature coefficient thermistor. The first end of the thermistor RT is connected to the output terminal of the temperature sampling circuit, and the second end of the thermistor RT is grounded.
4. The self-adjusting overcurrent protection circuit as described in claim 1, characterized in that: The current sampling circuit includes a resistor R21 and a capacitor C21. The first end of the resistor R21 is connected to the input terminal of the current sampling circuit, the second end of the resistor R21 and the first end of the capacitor C21 are connected to the output terminal of the current sampling circuit, and the second end of the capacitor C21 is grounded.
5. The self-adjusting overcurrent protection circuit as described in claim 1, characterized in that: The comparison circuit includes a resistor R31 and a comparator U31. The first end of the resistor R31 and the non-inverting input of the comparator U31 are connected to the second input of the comparison circuit. The second end of the resistor R31 and the output of the comparator U31 are connected to the output of the comparison circuit. The inverting input of the comparator U31 is connected to the first input of the comparison circuit.
6. The self-adjusting overcurrent protection circuit as described in claim 1, characterized in that: The switching circuit includes a resistor R41 and a switching transistor M41. The first end of the resistor R41 and the gate of the switching transistor M41 are connected to the control terminal of the switching circuit. The drain of the switching transistor M41 is connected to the input terminal of the switching circuit. The source of the switching transistor M41 and the second end of the resistor R41 are connected to the output terminal of the switching circuit.
7. The self-adjusting overcurrent protection circuit as described in claim 6, characterized in that: The switching circuit also includes a resistor R42, and the first end of the resistor R41 and the gate of the switching transistor M41 are connected to the control terminal of the switching circuit through the resistor R42.
8. The self-adjusting overcurrent protection circuit as described in claim 1, characterized in that: It also includes an MCU control circuit and an AND gate circuit. The control terminal of the switch circuit is connected to the output terminal of the comparator circuit through the AND gate circuit. The first input terminal of the AND gate circuit is connected to the output terminal of the comparator circuit. The second input terminal of the AND gate circuit is connected to the MCU control circuit. The output terminal of the AND gate circuit is connected to the control terminal of the switch circuit.
9. The self-adjusting overcurrent protection circuit as described in claim 8, characterized in that: The AND gate circuit includes resistor R51, resistor R52, diode D51, and AND gate U51; the cathode of diode D51 is connected to the first input terminal of the AND gate circuit, the anode of diode D51 is connected to the first terminal of resistor R52, the second terminal of resistor R52 and the first terminal of resistor R51 are connected to the first input terminal of AND gate U51, the second terminal of resistor R51 is connected to power supply VCC, the second input terminal of AND gate U51 is connected to the second input terminal of the AND gate circuit, and the output terminal of AND gate U51 is connected to the output terminal of the AND gate circuit.
10. The self-adjusting overcurrent protection circuit as described in claim 8, characterized in that: It also includes a filter circuit connected to the output of the comparator circuit. The filter circuit includes a resistor R61 and a capacitor C61. The first end of the resistor R61 is connected to the power supply VDD. The second end of the capacitor R61 and the first end of the capacitor C61 are connected to the output of the comparator circuit. The second end of the capacitor C61 is grounded.