Constant current protection circuit, method, power supply and electronic equipment

Abstract

The present invention discloses a constant current protection circuit, method, power supply and electronic equipment, belonging to the field of circuits. The constant current protection circuit of the present invention comprises a microprocessor, a driving module, a control switch, a filtering module, a voltage detection module, and a current sampling module. The driving module is connected to the microprocessor, the control switch is connected to the driving module, the filtering module is connected to the control switch, and the voltage detection module is respectively connected to the filtering module and the microprocessor; the voltage detection module is used to detect the output voltage of the power supply, the microprocessor is used to determine whether to output a control signal to turn off the control switch according to an abnormal output voltage, the driving module is used to change the output signal of the control switch according to the control signal, and the control switch controls the power supply state of the power supply to the load according to the output signal. This constant current protection circuit can detect load overload and take corresponding protection measures to improve the working safety of the circuit.

Description

Technical Field

[0001] The present invention relates to the field of circuits, and in particular to a constant current protection circuit, method, power supply and electronic equipment. Background Art

[0002] For DC load devices that require constant current operation, such as disinfectant water machines, electrolyzers, fruit and vegetable washing machines, etc., the output current is usually adjusted by changing the on-off duty cycle of the MOS tube to achieve the purpose of load constant current. However, when the load is overloaded or an accidental short circuit occurs, the current flowing through the sampling resistor and the MOS switch tube may be very large. The traditional load overcurrent detection method has the defects of long detection time and slow response to large load current (due to the normal fluctuation of the load current itself and the influence of the continuous and timely fine-tuning of the PWM duty cycle, the fluctuation and disorder of the load current are much more serious than the load voltage. The load current requires dozens of repeated sampling and comparison of size values, averaging, and other series of digital filtering and anti-misjudgment calculation processing), which can easily burn out the MOS switch tube and even the sampling resistor, microprocessor, etc., causing product quality problems. If the load is severely overloaded or short-circuited accidentally, causing the sampling resistor to burn out before the MOS tube and presenting an internal short circuit, the microprocessor will misjudge that the PWM duty cycle driven is not large enough because there is no voltage drop across the sampling resistor, and continue to increase the PWM duty cycle of the MOS tube, causing the MOS tube to burn out quickly; if the sampling resistor is damaged and presents an internal open circuit, the output voltage of the MOS tube will be added to the I / O port of the microprocessor due to the open circuit of the sampling resistor, which may cause the microprocessor to be damaged by overvoltage and cause product failure. Therefore, how to detect the load overload in the circuit and take corresponding protection measures has become an urgent problem to be solved. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a constant current protection circuit that can detect load overload and take corresponding protection measures to improve the working safety of the circuit.

[0004] The present invention also provides a constant current protection method having the above constant current protection circuit.

[0005] The present invention also provides a power supply having the above constant current protection circuit.

[0006] The invention also provides an electronic device having the power supply.

[0007] microprocessor;

[0008] A driving module, the driving module is connected to the microprocessor;

[0009] A control switch connected to the driving module;

[0010] A filter module, the filter module is connected to the control switch, and the filter module is used to filter the output signal of the control switch;

[0011] A voltage detection module, wherein the voltage detection module is connected to the output end of the filter module and the microprocessor respectively;

[0012] The voltage detection module is used to detect the output voltage of the power supply, the microprocessor is used to decide whether to output a control signal to shut down the control switch according to the abnormal output voltage, the driving module is used to change the output signal of the control switch according to the control signal, and the control switch controls the power supply state of the power supply to the load according to the output signal.

[0013] The constant current protection circuit according to the embodiment of the present invention has at least the following beneficial effects: the microprocessor of the constant current protection circuit can determine whether the load is overloaded by detecting the output voltage of the MOS tube when the set load current is reached, and the microprocessor determines the load overload according to the output voltage and outputs a control signal to turn off the output of the MOS tube, thereby improving the working safety of the circuit. The microprocessor also adjusts the duty cycle of the control signal in time according to the sampled value of the load current, and the driving module can change the output signal of the control switch output according to the control signal to keep the load current constant.

[0014] According to some embodiments of the present invention, the control switch is a MOS tube, a gate of the MOS tube is connected to the driving module, a source of the MOS tube is connected to the power supply, and a drain of the MOS tube is connected to the input end of the filtering module.

[0015] According to some embodiments of the present invention, the constant current protection circuit includes:

[0016] A current sampling module, the current sampling module is connected to the microprocessor, the current sampling module is used to collect the output current of the power supply, and output the output current to the microprocessor for detection, and the microprocessor is used to output a control signal according to the output current to keep the output current of the control switch constant.

[0017] According to some embodiments of the present invention, the driving module includes a first triode, a first resistor, a second triode, a third triode, a second resistor, a third resistor, an eighth resistor and a fourth capacitor;

[0018] Wherein, a first end of the fourth capacitor is connected to the power supply, and a second end of the fourth capacitor is grounded;

[0019] A first end of the eighth resistor is connected to the microprocessor, and a second end of the eighth resistor is connected to the base of the first transistor.

[0020] The base of the first transistor is connected to the second end of the eighth resistor, the collector of the first transistor is respectively connected to the second end of the first resistor, the base of the second transistor and the base of the third transistor, and the emitter of the first transistor is grounded;

[0021] The first end of the first resistor is connected to the power supply and the source of the MOS tube respectively, and the second end of the first resistor is connected to the collector of the first transistor;

[0022] The base of the second transistor is respectively connected to the second end of the first resistor and the collector of the first transistor, the collector of the second transistor is respectively connected to the source of the MOS transistor, the power supply and the first end of the third resistor, and the emitter of the second transistor is respectively connected to the gate of the MOS transistor, the second end of the third resistor and the first end of the second resistor;

[0023] The base of the third triode is respectively connected to the collector of the first triode, the base of the second triode and the second end of the first resistor, the emitter of the third triode is connected to the second end of the second resistor, and the collector of the third triode is grounded;

[0024] The first end of the second resistor is connected to the gate of the MOS transistor and the emitter of the second transistor respectively, and the second end of the second resistor is connected to the emitter of the third transistor;

[0025] A first end of the third resistor is connected to the source of the MOS transistor, and a second end of the third resistor is connected to the gate of the MOS transistor.

[0026] According to some embodiments of the present invention, the voltage detection module includes a first voltage stabilizing diode, a fourth resistor, a fifth resistor, and a first capacitor;

[0027] Wherein, the cathode of the first voltage stabilizing diode is connected to the microprocessor, and the anode of the first voltage stabilizing diode is grounded;

[0028] A first end of the fourth resistor is connected to the cathode of the first voltage zener diode, and a second end of the fourth resistor is connected to the anode of the first voltage zener diode and the ground respectively;

[0029] A first end of the fifth resistor is connected to the output end of the filter module, and a second end of the fifth resistor is connected to the first end of the fourth resistor;

[0030] The first end of the first capacitor is respectively connected to the cathode of the first voltage regulator diode, the first end of the fourth resistor and the second end of the fifth resistor, and the second end of the first capacitor is respectively connected to the anode of the first voltage regulator diode, the second end of the fourth resistor and ground.

[0031] According to some embodiments of the present invention, the filtering module includes a second diode, a second capacitor and an inductor;

[0032] Wherein, the cathode of the second diode is connected to the drain of the MOS tube, and the anode of the second diode is grounded;

[0033] The first end of the second capacitor is respectively connected to the second end of the inductor and the voltage detection module, and the second end of the second capacitor is respectively connected to the anode of the second diode and the ground;

[0034] The first end of the inductor is respectively connected to the drain of the MOS tube and the cathode of the second diode, and the second end of the inductor is respectively connected to the voltage detection module and the first end of the second capacitor.

[0035] According to some embodiments of the present invention, the current sampling module includes a third capacitor, a sixth resistor, a seventh resistor and a third diode;

[0036] Wherein, a first end of the third capacitor is connected to the microprocessor, and a second end of the third capacitor is grounded;

[0037] The first end of the sixth resistor is respectively connected to the second end of the seventh resistor and the anode of the third diode, and the second end of the sixth resistor is respectively connected to the second end of the third capacitor, the cathode of the third diode and ground;

[0038] The first end of the seventh resistor is respectively connected to the first end of the third capacitor and the microprocessor, and the second end of the seventh resistor is respectively connected to the first end of the sixth resistor and the anode of the third diode;

[0039] The anode of the third diode is connected to the first end of the sixth resistor and the second end of the seventh resistor respectively, and the cathode of the third diode is connected to the second end of the sixth resistor and the ground respectively.

[0040] According to a second aspect of the present invention, a constant current protection method includes:

[0041] Get the output current of the power supply;

[0042] According to the output current, the microprocessor outputs a first control signal;

[0043] acquiring an output voltage of a power supply according to the first control signal;

[0044] According to the output voltage, the microprocessor outputs a second control signal;

[0045] The driving module changes the output signal output by the control switch according to the second control signal.

[0046] The constant current protection method according to the embodiment of the present invention has at least the following beneficial effects: during the constant current protection process, the output current of the power supply is obtained, the microprocessor outputs a first control signal, and the output voltage of the power supply is obtained according to the first control signal. The microprocessor outputs a second control signal to change the output of the control switch, thereby shutting off the power supply of the power supply to the load. Specifically, the microprocessor outputs a continuous low-level control signal to shut off the control switch, thereby causing the power supply to stop supplying power to the load, protecting the electronic components, and improving the working safety of the circuit.

[0047] A power supply according to an embodiment of the third aspect of the present invention includes the constant current protection circuit as described in the first aspect.

[0048] The power supply according to the embodiment of the present invention has at least the following beneficial effects: the power supply adopts the above-mentioned constant current protection circuit, and the microprocessor of the constant current protection circuit detects the output voltage of the MOS tube when the set load current is reached, so that it can judge whether the load is overloaded, and the microprocessor judges the load overload according to the output voltage and outputs a control signal to turn off the output of the MOS tube, thereby improving the working safety of the circuit. The microprocessor also adjusts the duty cycle of the control signal in time according to the sampled value of the load current, and the driving module can change the output signal of the control switch output according to the control signal, so that the load current remains constant.

[0049] An electronic device according to an embodiment of a fourth aspect of the present invention comprises the power supply as described in the third aspect.

[0050] The electronic device according to the embodiment of the present invention has at least the following beneficial effects: the electronic device adopts the above power supply, and the microprocessor of the constant current protection circuit included in the power supply detects the output voltage of the MOS tube when the set load current is reached, so that it can judge whether the load is overloaded, and the microprocessor judges the load overload according to the output voltage and outputs a control signal to turn off the output of the MOS tube, thereby improving the working safety of the circuit. The microprocessor also adjusts the duty cycle of the control signal in time according to the sampled value of the load current, and the driving module can change the output signal of the control switch output according to the control signal to keep the load current constant.

[0051] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0053] Figure 1 A module schematic diagram of a constant current protection circuit according to an embodiment of the present invention;

[0054] Figure 2 is a circuit structure diagram of a constant current protection circuit according to another embodiment of the present invention;

[0055] Figure 3 FIG. 4 is a flow chart of a constant current protection method according to another embodiment of the present invention.

[0056] Reference numerals: 110, microprocessor; 120, driving module; 130, control switch; 140, voltage detection module; 150, filtering module; 160, current sampling module; 170, load. DETAILED DESCRIPTION

[0057] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0058] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0059] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0060] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0061] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0062] First, refer to Figure 1 The constant current protection circuit of the embodiment of the present invention includes a microprocessor 110, a driving module 120, a control switch 130, a filtering module 150, a voltage detection module 140 and a current sampling module 160. The driving module 120 is connected to the microprocessor 110, the control switch 130 is connected to the driving module 120, the filtering module 150 is connected to the control switch 130, and the filtering module 150 is used to filter the output signal output by the control switch 130; the voltage detection module 140 is respectively connected to the output end of the filtering module 150 and the microprocessor 110; the voltage detection module 140 is used to detect the output voltage of the control switch 130, the voltage detection module 140 is used to detect the output voltage of the power supply, the microprocessor 110 is used to determine whether to output a control signal to turn off the control switch 130 according to the abnormal output voltage, the driving module 120 is used to change the output signal of the control switch 130 according to the control signal, and the control switch 130 controls the power supply state of the power supply to the load 170 according to the output signal. It should be noted that this output signal includes the on-off state of the control switch, and the control switch 130 controls the power supply state of the power supply to the load according to the output signal. During the operation of the circuit, in order to enable the power supply to supply constant current to the load, the microprocessor 110 will output a preset PWM signal to the driving module 120, so that the driving module 120 can control the control switch 130 to be turned on, and the on state of the control switch 130 remains stable, and then the power supply can output constant current to supply power to the load. At this time, the voltage detection module 140 will detect the output voltage of the control switch 130 in real time, and the microprocessor 110 will decide whether to output a control signal to turn off the control switch 130 according to the abnormal output voltage. The driving module 120 can change the output signal of the control switch 130 according to the control signal. For example, when the voltage detection module 140 detects that the output voltage of the power supply is less than the preset voltage threshold, it indicates that the load is overloaded in the circuit. Therefore, the microprocessor 110 will output a control signal to the driving module 120, and the control switch 130 is turned off by the driving module 120, so that the power supply stops supplying power to the outside, and the electronic components in the circuit are protected. In this way, the power supply state of the power supply to the outside can be conveniently controlled, and the working safety of the circuit is improved.

[0063] Reference Figure 2 In some embodiments, the control switch 130 is a MOS tube Q4, the gate of the MOS tube Q4 is connected to the driving module 120, the source of the MOS tube Q4 is connected to the power supply, the drain of the MOS tube Q4 is connected to the input end of the filter module 150, and the filter module 150 is respectively connected to the load 170 and the voltage detection module 140. In order to enable the power supply to supply constant current to the load, when the output current of the power supply reaches a preset current threshold, the microprocessor 110 will output a preset PWM signal to the driving module 120, so that the driving module 120 can control the MOS tube Q4 to be turned on, and the PWM duty cycle of the MOS tube Q4 will no longer increase. At this time, the output current is also stabilized at a constant value, the circuit works normally, the power supply can supply power to the load through the constant current output of the MOS tube Q4, and the voltage detection module 140 will detect the output voltage Vout of the MOS tube Q4 in real time, and the microprocessor 110 will detect the output voltage Vout of the MOS tube Q4 according to the output current. Whether the voltage Vout is abnormal determines whether to output a control signal for shutting down the MOS tube Q4. The driving module 120 can change the output of the MOS tube Q4 according to the control signal. For example, when the voltage detection module 140 detects that the output voltage Vout of the power supply is less than a preset voltage threshold, it indicates that the load 170 in the circuit is overloaded. Therefore, the microprocessor 110 outputs a control signal to the driving module 120, and the MOS tube Q4 is shut off by the driving module 120, so that the power supply stops supplying power to the load 170, so as to avoid overcurrent damage to circuit components when the load 170 is overloaded. Since the output voltage Vout of the MOS tube Q4 has been filtered by the filter module 150, the ripple component is very small, and the result can be quickly determined by a single sampling detection method. However, the load current is affected by the fluctuation of the PWM duty cycle that is constantly and timely fine-tuned and the third capacitor C3 in the current sampling module 160 is too small (due to the need for fast response). The fluctuation disorder of the load current is much more serious than that of the output voltage. It requires dozens of repeated samplings and comparisons of magnitudes, averaging, and a series of digital filtering and calculation processing to prevent misjudgment. Therefore, the load current detection speed is obviously much slower than the output voltage Vout detection. The voltage detection module 140 can quickly detect the output voltage Vout, thereby determining whether a short circuit occurs in the circuit or the load 170 is overloaded. Then, the microprocessor 110 can quickly drive the MOS tube Q4 to shut down, so that the MOS tube Q4 stops supplying power to the load 170. The protection response speed is obviously much faster than the response speed of the current detection module 160. In this way, the power supply state of the power supply to the load 170 can be quickly controlled, thereby improving the working safety of the circuit.

[0064] It should be noted that the MOS tube Q4 can be a MOS tube Q4 of model NCE60P20K. This type of MOS tube Q4 has a higher voltage resistance and can improve the working safety of the circuit. In some other embodiments, other types of MOS tubes Q4 can also be selected, but are not limited to this.

[0065] Reference Figure 2In some embodiments, the driving module 120 includes a first transistor Q1, a first resistor R1, a second transistor Q2, a third transistor Q3, a second resistor R2, a third resistor R3, an eighth resistor R8 and a fourth capacitor C4, wherein a first end of the fourth capacitor C4 is connected to a power supply, and a second end of the fourth capacitor C4 is grounded; a second end of the eighth resistor R8 is connected to the base of the first transistor Q1, a first end of the eighth resistor R8 is connected to the microprocessor 110, a base of the first transistor Q1 is connected to the second end of the eighth resistor R8, a collector of the first transistor Q1 is respectively connected to the second end of the first resistor R1, a base of the second transistor Q2 and a base of the third transistor Q3, and an emitter of the first transistor Q1 is grounded; a first end of the first resistor R1 is respectively connected to a power supply and a source of the MOS tube Q4, a second end of the first resistor R1 is connected to the collector of the first transistor Q1; a base of the second transistor Q1 is respectively connected to The second end of the first resistor R1 and the collector of the first triode Q1 are connected, the collector of the second triode Q2 is respectively connected to the source of the MOS tube Q4, the power supply and the first end of the third resistor R3, and the emitter of the second triode Q2 is respectively connected to the gate of the MOS tube Q4, the second end of the third resistor R3 and the first end of the second resistor R2; the base of the third triode Q3 is respectively connected to the collector of the first triode Q1, the base of the second triode Q2 and the second end of the first resistor R1, the emitter of the third triode Q3 is connected to the second end of the second resistor R2, and the collector of the third triode Q3 is grounded; the first end of the second resistor R2 is respectively connected to the gate of the MOS tube Q4 and the emitter of the second triode Q2, and the second end of the second resistor R2 is connected to the emitter of the third triode Q3; the first end of the third resistor R3 is connected to the source of the MOS tube Q4, and the second end of the third resistor R3 is connected to the gate of the MOS tube Q4. During the operation of the circuit, the microprocessor 110 outputs a high-level PWM signal, and this PWM signal drives the first transistor Q1 to turn on through the eighth resistor R8. After the first transistor Q1 is turned on, the third transistor Q3 is turned on accordingly, and the second transistor Q2 is turned off because the base is in a low-level state. At this time, the gate of the MOS transistor Q4 is grounded after passing through the second resistor R2 and the third transistor Q3, and the MOS transistor Q4 is turned on; when the microprocessor 110 outputs a low-level PWM signal, this PWM signal turns off the first transistor Q1 after passing through the eighth resistor R8, and the third transistor Q3 is turned off because the base is in a high-level state, the second transistor Q2 is forward biased and turned on because the base is connected to the first resistor R1, and the MOS transistor Q4 is turned off because the gate is in a high level. In this way, the MOS transistor Q4 can switch between the on and off states according to the PWM signal output by the microprocessor 110, thereby controlling the power supply state of the power supply to the load.

[0066] It should be noted that when the microprocessor 110 starts working, the duty cycle of the PWM signal output by the microprocessor 110 will gradually decrease, so that the duty cycle of the MOS tube Q4 turning on will gradually increase, so that the output voltage Vout and the output current of the power supply to the load will increase accordingly. When the constant current power supply condition is met, the duty cycle of the PWM signal output by the microprocessor 110 will no longer change, so that the output voltage Vout can be stabilized at a certain value. Only when the load changes, the duty cycle of the PWM signal output by the microprocessor 110 will change to achieve constant current control, so that the power supply can control the constant current output through the MOS tube Q4 to supply power to the load, ensuring the normal operation of the power supply. As the load increases (the resistance value becomes smaller), for the constant current, the output voltage will decrease accordingly. By detecting the output voltage of the MOS tube and comparing it with the preset output voltage threshold, it can be determined whether the load is overloaded. The microprocessor determines that the load is abnormal according to the output voltage and outputs a control signal to turn off the output of the MOS tube, thereby improving the working safety of the circuit.

[0067] In some specific embodiments, the first transistor Q1 and the second transistor Q2 can select NPN transistors of model 9014 or 2N5551, which have good withstand voltage performance, and the third transistor Q3 can select PNP transistors of model 9015 or 2N5401, which have good withstand voltage performance, which can improve the working stability of the circuit. In some other embodiments, the first transistor Q1, the second transistor Q2 and the third transistor Q3 can also select other models, not limited to this. The first resistor R1, the second resistor R2, the third resistor R3, and the eighth resistor R8 can select 1 / 4W resistors of 2.2K~4.7K, and the fourth capacitor C4 can select a 470uF electrolytic capacitor that is more than 10V greater than the supply voltage Vin.

[0068] Reference Figure 2In some embodiments, the voltage detection module 140 includes a first voltage zener diode D1, a fourth resistor R4, a fifth resistor R5, and a first capacitor C1. The cathode of the first voltage zener diode D1 is connected to the microprocessor 110, and the anode of the first voltage zener diode D1 is grounded; the first end of the fourth resistor R4 is connected to the cathode of the first voltage zener diode D1, and the second end of the fourth resistor R4 is respectively connected to the anode of the first voltage zener diode D1 and the ground; the first end of the fifth resistor R5 is connected to the output end of the filter module 150, and the second end of the fifth resistor R5 is connected to the first end of the fourth resistor R4; the first end of the first capacitor C1 is respectively connected to the cathode of the first voltage zener diode D1, the first end of the fourth resistor R4, and the second end of the fifth resistor R5, and the second end of the first capacitor C1 is respectively connected to the anode of the first voltage zener diode D1, the second end of the fourth resistor R4, and the ground. It should be noted that the first voltage zener diode D1 can provide overvoltage protection for the I / O port of the microprocessor 110, thereby improving the working safety of the circuit. During the operation of the circuit, the output voltage Vout of the MOS tube Q4 is divided by the fourth resistor R4 and the fifth resistor R5 and filtered by the first capacitor C1 before being output to port 2 of the microprocessor 110 for detection. When the output voltage Vout detected by port 2 of the microprocessor 110 when the preset PWM maximum duty cycle is reached is less than the preset voltage threshold, it indicates that the circuit is overloaded. At this time, the PWM port of the microprocessor 110 outputs a continuous low-level signal to turn off the MOS tube Q4, so that the power supply stops supplying power to the load, the electronic components are protected, and the working safety of the circuit is improved.

[0069] It should be noted that the first voltage stabilizing diode D1 can be a 0.5W 4.3V voltage stabilizing diode or a TVS of a type such as SMFJ5.0A, so that the I / O port of the microprocessor 110 can be protected from overvoltage. It can also be a diode of other types, but is not limited thereto. The first capacitor C1 can be 1uF / 50V, the resistance ratio of the fifth resistor R5 and the fourth resistor R4 can be 10:1, the fifth resistor R5 can be 5.1K~51K, and the fourth resistor R4 can be 510Ω~5.1K.

[0070] Reference Figure 1 In some embodiments, in order to enable the power supply to provide stable power supply to the load, the constant current protection circuit also includes a filter module 150, and the filter module 150 is connected to the control switch 130. The filter module 150 can perform smoothing and filtering on the output signal of the control switch 130, thereby obtaining a stable output voltage, realizing power supply to the load, and ensuring the working stability of the circuit.

[0071] Reference Figure 2In some specific embodiments, in order to enable the power supply to stably supply power to the load, the filter module 150 includes a second diode D2, a second capacitor C2, and an inductor L. The cathode of the second diode D2 is connected to the drain of the MOS tube Q4, the anode of the second diode D2 is grounded, the first end of the second capacitor C2 is respectively connected to the second end of the inductor L and the voltage detection module 140, and the second end of the second capacitor C2 is respectively connected to the anode of the second diode D2 and the ground; the first end of the inductor L is respectively connected to the drain of the MOS tube Q4 and the cathode of the second diode D2, and the second end of the inductor L is respectively connected to the voltage detection module 140 and the first end of the second capacitor C2. In this way, the voltage output by the MOS tube Q4 can be filtered and converted into a smooth DC output voltage, thereby stably supplying power to the load and ensuring the working stability of the circuit.

[0072] It should be noted that the second diode D2 can be a Schottky diode of the type SS56, etc. This type of diode has good withstand voltage performance and can ensure the working stability of the circuit. In some other embodiments, other types of diodes can also be selected as the second diode D2, but it is not limited thereto. The inductor L can be a circular inductor with an inductance of 100uH and a withstand current of more than 2A greater than the maximum load current. The second capacitor C2 can be a 470uF electrolytic capacitor with a withstand voltage of more than 10V greater than the power supply voltage.

[0073] Reference Figure 1 In some embodiments, the constant current protection circuit includes a current sampling module 160, which is connected to the microprocessor 110. The current sampling module 160 is used to collect the output current of the power supply and output the output current to the microprocessor 110 for detection. In order to ensure the constant current output of the power supply, the constant current protection circuit also includes a current sampling module 160, which is connected to the microprocessor 110. The output current of the power supply can be conveniently sampled through the current sampling module 160. According to the relationship between the output current and the preset current threshold, it is determined whether the constant current output requirement is met, so that the microprocessor 110 can output a PWM control signal with an adjustable duty cycle to control the driving module 120 to change the on-off time duty cycle and on-off state of the control switch 130, so that the power supply can continuously output a constant current to power the load, thereby ensuring the working stability of the circuit.

[0074] Reference Figure 2In some specific embodiments, in order to ensure the constant current output of the power supply, the current sampling module 160 includes a third capacitor C3, a sixth resistor R6, a seventh resistor R7, and a third diode D3. The first end of the third capacitor C3 is connected to the microprocessor 110, and the second end of the third capacitor C3 is grounded; the first end of the sixth resistor R6 is respectively connected to the second end of the seventh resistor R7 and the anode of the third diode D3, and the second end of the sixth resistor R6 is respectively connected to the second end of the third capacitor C3, the cathode of the third diode D3 and ground; the first end of the seventh resistor R7 is respectively connected to the first end of the third capacitor C3 and the microprocessor 110, and the second end of the seventh resistor R7 is respectively connected to the first end of the sixth resistor R6 and the anode of the third diode D3; the anode of the third diode D3 is respectively connected to the first end of the sixth resistor R6 and the second end of the seventh resistor R7, and the cathode of the third diode D3 is respectively connected to the second end of the sixth resistor R6, the cathode of the third diode D3 The second end of the capacitor C3 is grounded, the sixth resistor R6 is a sampling resistor, and the third diode D3 is a clamping diode. The output current of the power supply generates a voltage waveform signal when passing through the two ends of the sampling resistor. This voltage signal is filtered by the seventh resistor R7 and the third capacitor C3 and then output to the No. 3 port of the microprocessor 110 for current detection. When it is detected that the output current value reaches the preset current threshold, the duty cycle of the PWM signal output by the microprocessor 110 no longer changes, and the output voltage Vout is also stabilized at a certain value. At this time, the power supply can output a constant current and supply power to the load normally. When the No. 3 port of the microprocessor 110 detects that the voltage across the two ends of the sampling resistor reaches the clamping voltage value of the clamping diode, it indicates that the load is short-circuited, and the microprocessor 110 will output a continuous low-level signal to turn off the MOS tube Q4, so that the power supply stops supplying power to the load, protects the electronic components, and improves the working safety of the circuit.

[0075] It should be noted that the third diode D3 is a power diode, which can provide overcurrent protection for the sixth resistor R6. When the load current is abnormally too large or short-circuited, causing the voltage drop across the sixth resistor to rise to a value greater than the clamping voltage of the third diode D3, the load current will flow through the third diode D3, and the third diode D3 clamps the voltage to ground sent by the current sampling module 160 to the microprocessor 110 to below 1V, thereby protecting the microprocessor. The third diode D3 can be a diode of model 1N4007, or other diodes, but is not limited thereto. The sixth resistor R6 responsible for sampling can be a precision resistor or constantan wire of 0.1Ω, power not less than 1W, and accuracy of ±1%, the seventh resistor R7 can be a 1 / 4W resistor of 1K~2.2K, the third capacitor C3 can be 100pF / 50V~470pF / 50V, and the capacitance value cannot be too large, so as not to be unable to sensitively respond to subtle changes in the load current and affect the regulation accuracy of PWM for the load constant current.

[0076] Second, refer to Figure 3, the constant current protection method of the embodiment of the present invention comprises:

[0077] S100, obtaining the output current of the power supply;

[0078] S200, the microprocessor outputs a first control signal according to the output current;

[0079] S300, obtaining an output voltage of a power supply according to a first control signal;

[0080] S400, the microprocessor outputs a second control signal according to the output voltage;

[0081] S500: The driving module changes the output signal output by the control switch according to the second control signal.

[0082] In the process of constant current protection, the output current of the power supply is obtained, and the magnitude relationship between the output current and the preset current threshold is compared. When the output current reaches the preset current threshold, it indicates that the output of the power supply has reached the requirement of constant current power supply for the load. At this time, the microprocessor outputs a first control signal to control the drive module to make the on-duty ratio of the control switch at a certain value, and the output voltage of the power supply is also stabilized at a certain value. For a constant current, the larger the load (the smaller the resistance), the lower the output voltage. The output voltage of the power supply is obtained, and the output voltage is detected in real time. The magnitude relationship between the output voltage and the preset voltage threshold can be compared to determine whether the load is overloaded. It should be noted that the preset voltage threshold is also the corresponding normal output voltage value. When the output voltage is detected to be less than the preset voltage threshold or the corresponding normal output voltage value, it indicates that the circuit has a load overload. At this time, the microprocessor outputs a second control signal to change the output of the control switch, thereby shutting off the power supply to the load. Specifically, the microprocessor outputs a continuous low-level control signal to shut off the control switch, so that the power supply stops supplying power to the load, protects the electronic components, and improves the working safety of the circuit.

[0083] In a third aspect, a power supply according to an embodiment of the present invention includes a constant current protection circuit according to the embodiment of the first aspect.

[0084] The power supply according to the embodiment of the present invention has at least the following beneficial effects: the power supply adopts the above-mentioned constant current protection circuit, and the microprocessor of the constant current protection circuit detects the output voltage of the MOS tube when the set load current is reached, so that it can judge whether the load is overloaded, and the microprocessor judges the load overload according to the output voltage and outputs a control signal to turn off the output of the MOS tube, thereby improving the working safety of the circuit. The microprocessor also adjusts the duty cycle of the control signal in time according to the sampled value of the load current, and the driving module can change the output signal of the control switch output according to the control signal, so that the load current remains constant.

[0085] In a fourth aspect, an electronic device according to an embodiment of the present invention includes a power supply according to the embodiment of the third aspect.

[0086] The electronic device according to the embodiment of the present invention has at least the following beneficial effects: the electronic device adopts the above power supply, and the microprocessor of the constant current protection circuit included in the power supply detects the output voltage of the MOS tube when the set load current is reached, so that it can judge whether the load is overloaded, and the microprocessor judges the load overload according to the output voltage and outputs a control signal to turn off the output of the MOS tube, thereby improving the working safety of the circuit. The microprocessor also adjusts the duty cycle of the control signal in time according to the sampled value of the load current, and the driving module can change the output signal of the control switch output according to the control signal to keep the load current constant.

[0087] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. Constant current protection circuit, characterized in that, include: microprocessor; A driving module, the driving module is connected to the microprocessor; A control switch connected to the driving module; A filter module, the filter module is connected to the control switch, and the filter module is used to filter the output signal of the control switch; A voltage detection module, wherein the voltage detection module is connected to the output end of the filter module and the microprocessor respectively; The voltage detection module is used to detect the output voltage of the power supply, the microprocessor is used to determine whether to output a control signal to shut down the control switch according to the abnormality of the output voltage, the driving module is used to change the output signal of the control switch according to the control signal, and the control switch controls the power supply state of the power supply to the load according to the output signal; The control switch is a MOS tube, the gate of the MOS tube is connected to the driving module, the source of the MOS tube is connected to the power supply, and the drain of the MOS tube is connected to the input end of the filter module; The model of the MOS tube is NCE60P20K; The constant current protection circuit comprises: A current sampling module, the current sampling module is connected to the microprocessor, the current sampling module is used to collect the output current of the power supply, and output the output current to the microprocessor for detection, and the microprocessor is used to output a control signal according to the output current to keep the output current of the control switch constant; The driving module includes a first triode, a first resistor, a second triode, a third triode, a second resistor, a third resistor, an eighth resistor and a fourth capacitor; Wherein, a first end of the fourth capacitor is connected to the power supply, and a second end of the fourth capacitor is grounded; A first end of the eighth resistor is connected to the microprocessor, and a second end of the eighth resistor is connected to the base of the first transistor; The base of the first transistor is connected to the second end of the eighth resistor, the collector of the first transistor is respectively connected to the second end of the first resistor, the base of the second transistor and the base of the third transistor, and the emitter of the first transistor is grounded; The first end of the first resistor is connected to the power supply and the source of the MOS tube respectively, and the second end of the first resistor is connected to the collector of the first transistor; The base of the second transistor is respectively connected to the second end of the first resistor and the collector of the first transistor, the collector of the second transistor is respectively connected to the source of the MOS transistor, the power supply and the first end of the third resistor, and the emitter of the second transistor is respectively connected to the gate of the MOS transistor, the second end of the third resistor and the first end of the second resistor; The base of the third triode is respectively connected to the collector of the first triode, the base of the second triode and the second end of the first resistor, the emitter of the third triode is connected to the second end of the second resistor, and the collector of the third triode is grounded; The first end of the second resistor is connected to the gate of the MOS transistor and the emitter of the second transistor respectively, and the second end of the second resistor is connected to the emitter of the third transistor; A first end of the third resistor is connected to the source of the MOS transistor, and a second end of the third resistor is connected to the gate of the MOS transistor; The filtering module includes a second diode, a second capacitor and an inductor; The current sampling module includes a third capacitor, a sixth resistor, a seventh resistor and a third diode.

2. The constant current protection circuit according to claim 1, characterized in that: The voltage detection module includes a first voltage stabilizing diode, a fourth resistor, a fifth resistor, and a first capacitor; Wherein, the cathode of the first voltage stabilizing diode is connected to the microprocessor, and the anode of the first voltage stabilizing diode is grounded; A first end of the fourth resistor is connected to the cathode of the first voltage zener diode, and a second end of the fourth resistor is connected to the anode of the first voltage zener diode and the ground respectively; A first end of the fifth resistor is connected to the output end of the filter module, and a second end of the fifth resistor is connected to the first end of the fourth resistor; The first end of the first capacitor is respectively connected to the cathode of the first voltage regulator diode, the first end of the fourth resistor and the second end of the fifth resistor, and the second end of the first capacitor is respectively connected to the anode of the first voltage regulator diode, the second end of the fourth resistor and ground.

3. The constant current protection circuit according to claim 2, characterized in that: The cathode of the second diode is connected to the drain of the MOS tube, and the anode of the second diode is grounded; The first end of the second capacitor is respectively connected to the second end of the inductor and the voltage detection module, and the second end of the second capacitor is respectively connected to the anode of the second diode and the ground; The first end of the inductor is respectively connected to the drain of the MOS tube and the cathode of the second diode, and the second end of the inductor is respectively connected to the voltage detection module and the first end of the second capacitor.

4. The constant current protection circuit according to claim 3, characterized in that: A first end of the third capacitor is connected to the microprocessor, and a second end of the third capacitor is grounded; The first end of the sixth resistor is respectively connected to the second end of the seventh resistor and the anode of the third diode, and the second end of the sixth resistor is respectively connected to the second end of the third capacitor, the cathode of the third diode and ground; The first end of the seventh resistor is respectively connected to the first end of the third capacitor and the microprocessor, and the second end of the seventh resistor is respectively connected to the first end of the sixth resistor and the anode of the third diode; The anode of the third diode is connected to the first end of the sixth resistor and the second end of the seventh resistor respectively, and the cathode of the third diode is connected to the second end of the sixth resistor and the ground respectively.

5. The constant current protection method of the constant current protection circuit according to any one of claims 1 to 4, characterized in that: include: Get the output current of the power supply; According to the output current, the microprocessor outputs a first control signal; acquiring an output voltage of a power supply according to the first control signal; According to the output voltage, the microprocessor outputs a second control signal; The driving module changes the output signal output by the control switch according to the second control signal.

6. A power supply, characterized in that Comprising a constant current protection circuit as described in any one of claims 1 to 4.

7. An electronic device, characterized in that Comprising a power supply as claimed in claim 6.

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