Power supply with overload protection

Abstract

The utility model relates to the technical field of instrument power supplies, in particular to a power supply with overload protection, which is provided with a sampling resistor, when the power supply is accessed as a standby power supply, because the voltage is basically equal to the voltage of a power supply to be maintained, and the output current is smaller, when the power supply is controlled to boost by a voltage-regulating excitation source, the sampling resistor is switched on. As the dynamic impedance at the moment is approximately equal to the impedance of the sampling resistor, the change rate of the output current of the power supply is large, and when the output current of the power supply reaches the current required by the load, the change rate of the output current of the power supply is small. The differential operational amplifier circuit, the differentiating circuit, the Schmitt trigger and the voltage-regulating excitation source generate voltage which enables the output voltage of the power supply to be gradually increased when the current change rate is relatively high, and the increasing process is stopped when the output current reaches the current required by a load; load current is smoothly transferred to the standby power supply from the power supply to be maintained, and overload of the sensor is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of instrument power supplies, in particular to a power supply with overload protection. Background Art

[0002] The power supply for metering instruments must have high reliability and good maintainability, especially for the power supply of instruments in the power industry. In addition to meeting the reliability and maintainability requirements of general instrument power supplies, the power supply of instruments in the power industry must also have hot switching capabilities.

[0003] However, hot-switching the power supply of existing instruments can cause overloads in connected sensors. For example, for instruments connected to voltage transformers or current transformers, before performing power maintenance on an instrument in use, the backup power supply should be connected to the instrument before the power supply to be maintained is removed. This hot-switching process, without a smooth transition from the output of the power supply to be maintained to the backup power supply, can cause transient anomalies (impedance surges) in the instrument's sensor connections, further causing transient overcurrent in the voltage transformer or current transformer (voltage transformers must not be short-circuited, and current transformers must not be open-circuited, as otherwise, accuracy issues will result), ultimately impacting the meter's accuracy.

[0004] Based on this, it is necessary to develop a power supply with overload protection function for the instrument. Utility Model Content

[0005] The embodiment of the present utility model provides a power supply with overload protection, which is used to solve the problem in the prior art that the output current is uncontrollable during hot switching of the power supply, which may cause sensor overload.

[0006] In a first aspect, an embodiment of the present invention provides a power supply with overload protection, comprising:

[0007] Power supply, sampling resistor, differential operational amplifier circuit, differential circuit, Schmitt trigger and voltage regulation excitation source;

[0008] The output end of the power supply is electrically connected to the first end of the sampling resistor, the two input ends of the differential operational amplifier circuit are electrically connected to the two ends of the sampling resistor respectively, the input end and the output end of the differential circuit are electrically connected to the output end of the differential operational amplifier circuit and the input end of the Schmitt trigger respectively, and the input end and the output end of the voltage regulation excitation source are electrically connected to the output end of the Schmitt trigger and the voltage regulation end of the power supply respectively;

[0009] When the output voltage of the power supply changes, the voltage across the sampling resistor is amplified by the differential operational amplifier circuit and then fed into the differential circuit to obtain a change rate indication signal of the power supply output current; when the change rate indication signal is higher than a first threshold, the Schmitt trigger outputs a first indication; and when the change rate indication signal is lower than a second threshold, the Schmitt trigger outputs a second indication; and the voltage regulation excitation source generates an indication for increasing the output voltage of the power supply and an indication for maintaining the current output voltage unchanged based on the first indication and the second indication, respectively.

[0010] In some possible implementations, the differential operational amplifier circuit includes:

[0011] a first operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor;

[0012] The second end of the first resistor and the second end of the third resistor are electrically connected to the positive input terminal of the first operational amplifier and the negative input terminal of the first operational amplifier respectively;

[0013] Two ends of the second resistor are respectively connected to the ground and the positive input terminal of the first operational amplifier;

[0014] Two ends of the fourth resistor are electrically connected to the inverting input terminal of the first operational amplifier and the output terminal of the first operational amplifier respectively;

[0015] The first end of the first resistor and the first end of the third resistor are electrically connected to an end of the sampling resistor close to the power output end and an end of the sampling resistor far from the power output end, respectively.

[0016] In some possible implementations, the differential circuit includes: a second operational amplifier, a fifth resistor, a sixth resistor, and a first capacitor;

[0017] Two ends of the fifth resistor are electrically connected to the ground and the positive input terminal of the second operational amplifier respectively;

[0018] Two ends of the sixth resistor are electrically connected to the inverting input terminal of the second operational amplifier and the output terminal of the second operational amplifier respectively;

[0019] Two ends of the first capacitor are electrically connected to the output end of the differential operational amplifier circuit and the inverting input end of the second operational amplifier, respectively.

[0020] In some possible implementations, the Schmitt trigger includes: a seventh resistor, an eighth resistor, a ninth resistor, a voltage stabilizing diode, and a third operational amplifier;

[0021] Two ends of the seventh resistor are electrically connected to the ground and the positive input terminal of the third operational amplifier respectively;

[0022] Two ends of the eighth resistor are electrically connected to the positive input terminal of the third operational amplifier and the cathode of the voltage stabilizing diode respectively;

[0023] The anode of the voltage stabilizing diode is electrically connected to the output terminal of the third operational amplifier;

[0024] Two ends of the eighth resistor are electrically connected to the cathode of the voltage stabilizing diode and the positive electrode of the power supply respectively;

[0025] An inverting input terminal of the third operational amplifier is electrically connected to an output terminal of the differential circuit.

[0026] In some possible implementations, the voltage regulation excitation source includes: a tenth resistor, an eleventh resistor, a second capacitor, a third capacitor, and a transistor;

[0027] Two ends of the tenth resistor are electrically connected to the output end of the Schmitt trigger and the base of the transistor respectively;

[0028] The two ends of the eleventh resistor are electrically connected to the positive electrode of the power supply and the collector of the transistor respectively;

[0029] The first end of the second capacitor and the second end of the third capacitor are electrically connected to the emitter of the transistor and the ground respectively, and the second end of the second capacitor is electrically connected to the first end of the third capacitor.

[0030] In some possible implementations, the voltage regulation excitation source further includes: a key switch;

[0031] The two ends of the key switch are electrically connected to the collector of the transistor and the emitter of the transistor respectively.

[0032] In some possible implementations, the power supply includes: an adjustable three-terminal regulator, a twelfth resistor, a thirteenth resistor, and a fourth capacitor;

[0033] Two ends of the twelfth resistor are electrically connected to the output end of the adjustable three-terminal regulator and the adjustment end of the adjustable three-terminal regulator, respectively; two ends of the thirteenth resistor are electrically connected to the adjustment end of the adjustable three-terminal regulator and the first end of the fourth capacitor, respectively;

[0034] The second end of the fourth capacitor is electrically connected to the output end of the voltage-regulated excitation source.

[0035] In some possible implementations, the power supply with overload protection further includes an indication circuit, and the indication circuit is electrically connected to the output end of the Schmitt trigger.

[0036] In some possible implementations, the power supply with overload protection further includes an output diode, and an anode of the output diode is electrically connected to an end of the sampling resistor away from the output end of the power supply.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention discloses a power supply with overload protection, which has a sampling resistor. When the power supply is connected as a backup power supply, the output current is small because the voltage is basically the same as the voltage of the power supply to be maintained. When the power supply is boosted by controlling the voltage of the power supply, the dynamic impedance at this time is approximately equal to the impedance of the sampling resistor, so the rate of change of the power supply output current is large. When the power supply output current reaches the current required by the load, the rate of change of the power supply output current is small. The differential operational amplifier circuit, differential circuit, Schmitt trigger and voltage regulation excitation source of the present invention generate a voltage that gradually increases the output voltage of the power supply when the current change rate is high, and stop the raising process when the output current reaches the current required by the load, thereby realizing the smooth transfer of the load current from the power supply to be maintained to the backup power supply, avoiding the influence of the current mutation on the instrument and sensor, and reducing the possibility of sensor overload. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0040] Figure 1 This is a functional block diagram of a power supply with overload protection provided by an embodiment of the present utility model;

[0041] Figure 2 This is a schematic diagram of a differential operational amplifier circuit provided by an embodiment of the present utility model;

[0042] Figure 3 It is a differential circuit principle diagram provided by the embodiment of the present utility model;

[0043] Figure 4 This is a schematic diagram of a Schmitt trigger provided by an embodiment of the present utility model;

[0044] Figure 5 This is a schematic diagram of a voltage-regulated excitation source provided by an embodiment of the present utility model;

[0045] Figure 6This is a power supply principle diagram provided by an embodiment of the present utility model. DETAILED DESCRIPTION

[0046] In the following description, specific details such as particular system structures and techniques are provided for purposes of illustration, not limitation, to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, and methods are omitted to avoid obscuring the description of the present invention with unnecessary detail.

[0047] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following will be described through specific implementation methods in conjunction with the accompanying drawings.

[0048] The following is a detailed description of an embodiment of the present invention. This example is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0049] Figure 1 This is a diagram of the overall structure of a power supply with overload protection provided by an embodiment of the present utility model.

[0050] like Figure 1 As shown, it shows the overall structure of the power supply with overload protection provided by the embodiment of the utility model, which is detailed as follows:

[0051] A power supply with overload protection, comprising:

[0052] Power supply, sampling resistor, differential operational amplifier circuit, differential circuit, Schmitt trigger and voltage regulation excitation source;

[0053] The output end of the power supply is electrically connected to the first end of the sampling resistor, the two input ends of the differential operational amplifier circuit are electrically connected to the two ends of the sampling resistor respectively, the input end and the output end of the differential circuit are electrically connected to the output end of the differential operational amplifier circuit and the input end of the Schmitt trigger respectively, and the input end and the output end of the voltage regulation excitation source are electrically connected to the output end of the Schmitt trigger and the voltage regulation end of the power supply respectively;

[0054] When the output voltage of the power supply changes, the voltage across the sampling resistor is amplified by the differential operational amplifier circuit and then fed into the differential circuit to obtain a change rate indication signal of the power supply output current; when the change rate indication signal is higher than a first threshold, the Schmitt trigger outputs a first indication; and when the change rate indication signal is lower than a second threshold, the Schmitt trigger outputs a second indication; and the voltage regulation excitation source generates an indication for increasing the output voltage of the power supply and an indication for maintaining the current output voltage unchanged based on the first indication and the second indication, respectively.

[0055] For example, Figure 1 As shown, the power supply of the embodiment of the present invention includes six parts: a power supply, a sampling resistor, a differential operational amplifier circuit, a differential circuit, a Schmitt trigger and a voltage regulating excitation source. The sampling resistor is a low-resistance resistor, such as a 0.1 ohm precision resistor. When current flows through this resistor, a small voltage drop will be generated across the resistor. When the power supply in the figure is connected in parallel with other power supplies as a backup power supply to supply power to the load (instrument circuit), the initial voltage of the backup power supply is basically the same as or lower than the voltage of the power supply to be maintained, so that the output current of the backup power supply is very small.

[0056] When the voltage regulating excitation source is affected by the outside world, Figure 1 When the power supply generates a small forward voltage fluctuation, the load terminal voltage is approximately equal to the voltage of the power supply to be maintained. Figure 1 The change of the current of the power supply in the circuit conforms to the following formula:

[0057]

[0058] In the above formula, ΔI is the change value of power supply current, ΔU DC is the change value of the power supply voltage, and SamR is the resistance value of the sampling resistor.

[0059] Since the resistance of the sampling resistor is very small, the change of the power supply output current is large. Figure 1 After the voltage of the power supply gradually increases to approach the current required by the load, when the voltage of the power supply increases again, the rate of change of the power supply output current drops much lower than the current in the above formula. The rate of change of the voltage across the sampling resistor corresponding to the above process is proportional to the rate of change of the current. The embodiment of the present invention obtains the voltage from both ends of the sampling resistor, amplifies it through the differential operational amplifier circuit, and then sends it to the differential circuit to obtain the rate value of the current change. When this rate value is higher than the first threshold and lower than the second threshold, the Schmitt trigger generates two indications respectively. Obviously, when it is higher than the first threshold, it should indicate Figure 1 The power supply voltage continues to increase, otherwise it maintains the current voltage.

[0060] The power supply with overload protection in the embodiment of the present invention has a sampling resistor. When the power supply is connected as a backup power supply, the voltage is basically the same as the voltage of the power supply to be maintained, so the output current is small. When the power supply is boosted by the voltage regulating excitation source, the dynamic impedance at this time is approximately equal to the impedance of the sampling resistor, so the power supply output current change rate is large. When the power supply output current reaches the current required by the load, the power supply output current change rate is small. The differential operational amplifier circuit, differential circuit, Schmitt trigger and voltage regulating excitation source in the embodiment of the present invention generate a voltage that gradually increases the power supply output voltage when the current change rate is high, and stop the raising process when the output current reaches the current required by the load, thereby realizing the smooth transfer of the load current from the power supply to be maintained to the backup power supply, avoiding the impact of the current mutation on the instrument and sensor, and reducing the possibility of sensor overload.

[0061] In order to realize the functions of the above-mentioned functional modules, the embodiments of the present invention discuss and illustrate the functional modules in detail from the following aspects.

[0062] In some embodiments, the differential operational amplifier circuit includes:

[0063] a first operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor;

[0064] The second end of the first resistor and the second end of the third resistor are electrically connected to the positive input terminal of the first operational amplifier and the negative input terminal of the first operational amplifier respectively;

[0065] Two ends of the second resistor are respectively connected to the ground and the positive input terminal of the first operational amplifier;

[0066] Two ends of the fourth resistor are electrically connected to the inverting input terminal of the first operational amplifier and the output terminal of the first operational amplifier respectively;

[0067] The first end of the first resistor and the first end of the third resistor are electrically connected to an end of the sampling resistor close to the power output end and an end of the sampling resistor far from the power output end, respectively.

[0068] For example, Figure 2 As shown in the figure, a differential operational amplifier circuit is shown, in which the first operational amplifier Amp1, the first resistor R11, the second resistor R12, the third resistor R13 and the fourth resistor R14 constitute a differential operational amplifier circuit for amplifying the voltage difference between the two ends of the sampling resistor. Figure 1 As for the sampling resistor SamR in FIG, the left end of the sampling resistor is connected to the left end of the first resistor R11 , and the right end of the sampling resistor is connected to the left end of the third resistor R13 .

[0069] In some embodiments, the differential circuit includes: a second operational amplifier, a fifth resistor, a sixth resistor, and a first capacitor;

[0070] Two ends of the fifth resistor are electrically connected to the ground and the positive input terminal of the second operational amplifier respectively;

[0071] Two ends of the sixth resistor are electrically connected to the inverting input terminal of the second operational amplifier and the output terminal of the second operational amplifier respectively;

[0072] Two ends of the first capacitor are electrically connected to the output end of the differential operational amplifier circuit and the inverting input end of the second operational amplifier, respectively.

[0073] For example, Figure 3 As shown in the figure, a differential circuit is shown. In the figure, the second operational amplifier Amp2, the fifth resistor R21, the sixth resistor R22 and the first capacitor C1 constitute a differential circuit. This differential circuit is used to extract the rate of change of the voltage across the sampling resistor. The output of the second operational amplifier Amp2 is proportional to the rate of change of the power supply output current. Figure 3 As for the first capacitor C1 in the circuit, its left end is connected to the output end of the first operational amplifier Amp1 to receive the differential voltage amplified signal output by the first operational amplifier Amp1.

[0074] In some embodiments, the Schmitt trigger includes: a seventh resistor, an eighth resistor, a ninth resistor, a voltage stabilizing diode, and a third operational amplifier;

[0075] Two ends of the seventh resistor are electrically connected to the ground and the positive input terminal of the third operational amplifier respectively;

[0076] Two ends of the eighth resistor are electrically connected to the positive input terminal of the third operational amplifier and the cathode of the voltage stabilizing diode respectively;

[0077] The anode of the voltage stabilizing diode is electrically connected to the output terminal of the third operational amplifier;

[0078] Two ends of the eighth resistor are electrically connected to the cathode of the voltage stabilizing diode and the positive electrode of the power supply respectively;

[0079] An inverting input terminal of the third operational amplifier is electrically connected to an output terminal of the differential circuit.

[0080] For example, Figure 4As shown in the figure, a Schmitt trigger is shown, in which the third operational amplifier Amp3, the seventh resistor R31, the eighth resistor R32, the ninth resistor R33 and the voltage stabilizing diode Z1 constitute a Schmitt trigger for outputting a high level or a low level according to the output of the second operational amplifier Amp2. Figure 3 As for the third operational amplifier Amp3, its inverting input is connected to Figure 2 The output terminal of the second operational amplifier Amp2 is connected.

[0081] In some embodiments, the voltage regulation excitation source includes: a tenth resistor, an eleventh resistor, a second capacitor, a third capacitor, and a transistor;

[0082] Two ends of the tenth resistor are electrically connected to the output end of the Schmitt trigger and the base of the transistor respectively;

[0083] The two ends of the eleventh resistor are electrically connected to the positive electrode of the power supply and the collector of the transistor respectively;

[0084] The first end of the second capacitor and the second end of the third capacitor are electrically connected to the emitter of the transistor and the ground respectively, and the second end of the second capacitor is electrically connected to the first end of the third capacitor.

[0085] In some embodiments, the voltage regulation excitation source further comprises: a key switch;

[0086] The two ends of the key switch are electrically connected to the collector of the transistor and the emitter of the transistor respectively.

[0087] For example, Figure 5 As shown in the figure, a voltage regulation excitation source is shown, in which the tenth resistor R41, the eleventh resistor R42, the second capacitor C2, the third capacitor C3 and the transistor Q1 are used to generate an excitation signal that increases the output voltage of the power supply according to the output of the Schmitt trigger. Figure 5 As for the tenth resistor R41, its left end is connected to the cathode of the voltage-stabilizing diode Z1. When the Schmitt trigger outputs a high level, the transistor Q1 is saturated and turned on. The positive electrode of the power supply charges the second capacitor C2 and the third capacitor C3 through the eleventh resistor R42, so that the upper end voltage of the third capacitor C3 gradually increases. During the boosting process, the upper end voltage of the third capacitor C3 is a voltage allocated according to the capacity of the second capacitor C2 and the capacity of the third capacitor C3.

[0088] In addition, in some application scenarios, a key switch S1 is also provided. This switch is connected in parallel to the emitter and collector of the transistor Q1. When the key is pressed, the following is achieved: Figure 3 The effect of the diode Q1 being saturated and turned on.

[0089] In some embodiments, the power supply includes: an adjustable three-terminal regulator, a twelfth resistor, a thirteenth resistor, and a fourth capacitor;

[0090] Two ends of the twelfth resistor are electrically connected to the output end of the adjustable three-terminal regulator and the adjustment end of the adjustable three-terminal regulator, respectively; two ends of the thirteenth resistor are electrically connected to the adjustment end of the adjustable three-terminal regulator and the first end of the fourth capacitor, respectively;

[0091] The second end of the fourth capacitor is electrically connected to the output end of the voltage-regulated excitation source.

[0092] For example, Figure 6 As shown in the figure, a voltage adjustable power supply is shown. In the figure, an adjustable three-terminal voltage regulator LM317, a twelfth resistor R51, a thirteenth resistor R52 and a fourth capacitor C4 constitute an adjustable power supply, wherein the lower end of the fourth capacitor C4 is connected to Figure 5 The upper end of the third capacitor C3 is connected.

[0093] When the voltage of the fourth capacitor C4 increases, the output voltage of the power supply increases synchronously.

[0094] In some embodiments, the power supply with overload protection further includes an indication circuit, and the indication circuit is electrically connected to the output end of the Schmitt trigger.

[0095] In some possible implementations, the power supply with overload protection further includes an output diode, and an anode of the output diode is electrically connected to an end of the sampling resistor away from the output end of the power supply.

[0096] For example, in some application scenarios, an indicator circuit is provided, such as a light-emitting diode (LED) with a resistor in series connected to the cathode of a voltage-stabilizing diode Z1. When the cathode of the voltage-stabilizing diode Z1 is at a high level, the LED illuminates, indicating that a hot switch is in progress. When the LED goes out, it indicates that the load has been transferred to the backup power supply. The power supply to be maintained can be disconnected.

[0097] In some other application scenarios, an output diode is provided at the output end of the sampling resistor to prevent the power supply to be maintained from outputting backflow current to the backup power supply after the backup power supply is connected to the load.

[0098] In addition, in some application scenarios, the power supply has two outputs, one of which does not pass through the sampling resistor, while the other does. The purpose is that when two or more instruments are used together, the power supply of one instrument can be used as a backup power supply for another instrument. The load connected to the power supply to be maintained can be connected to the output terminal connected to the sampling resistor.

[0099] It should be understood that the size of the serial numbers of each step in the above embodiment does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present utility model.

[0100] The following is an embodiment of the device of the present invention. For details not described in detail, please refer to the corresponding method embodiment described above.

Claims

1. A power supply with overload protection, characterized in that: include: Power supply, sampling resistor, differential operational amplifier circuit, differential circuit, Schmitt trigger and voltage regulation excitation source; The output end of the power supply is electrically connected to the first end of the sampling resistor, the two input ends of the differential operational amplifier circuit are electrically connected to the two ends of the sampling resistor respectively, the input end and the output end of the differential circuit are electrically connected to the output end of the differential operational amplifier circuit and the input end of the Schmitt trigger respectively, and the input end and the output end of the voltage regulation excitation source are electrically connected to the output end of the Schmitt trigger and the voltage regulation end of the power supply respectively; When the output voltage of the power supply changes, the voltage across the sampling resistor is amplified by the differential operational amplifier circuit and then fed into the differential circuit to obtain a change rate indication signal of the power supply output current; when the change rate indication signal is higher than a first threshold, the Schmitt trigger outputs a first indication; and when the change rate indication signal is lower than a second threshold, the Schmitt trigger outputs a second indication; and the voltage regulation excitation source generates an indication for increasing the output voltage of the power supply and an indication for maintaining the current output voltage unchanged based on the first indication and the second indication, respectively.

2. The power supply with overload protection according to claim 1, characterized in that: The differential operational amplifier circuit comprises: a first operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor; The second end of the first resistor and the second end of the third resistor are electrically connected to the positive input terminal of the first operational amplifier and the negative input terminal of the first operational amplifier respectively; Two ends of the second resistor are respectively connected to the ground and the positive input terminal of the first operational amplifier; Two ends of the fourth resistor are electrically connected to the inverting input terminal of the first operational amplifier and the output terminal of the first operational amplifier respectively; The first end of the first resistor and the first end of the third resistor are electrically connected to an end of the sampling resistor close to the power output end and an end of the sampling resistor far from the power output end, respectively.

3. The power supply with overload protection according to claim 1, characterized in that: The differential circuit includes: a second operational amplifier, a fifth resistor, a sixth resistor and a first capacitor; Two ends of the fifth resistor are electrically connected to the ground and the positive input terminal of the second operational amplifier respectively; Two ends of the sixth resistor are electrically connected to the inverting input terminal of the second operational amplifier and the output terminal of the second operational amplifier respectively; Two ends of the first capacitor are electrically connected to the output end of the differential operational amplifier circuit and the inverting input end of the second operational amplifier, respectively.

4. The power supply with overload protection according to claim 1, characterized in that: The Schmitt trigger includes: a seventh resistor, an eighth resistor, a ninth resistor, a voltage stabilizing diode and a third operational amplifier; Two ends of the seventh resistor are electrically connected to the ground and the positive input terminal of the third operational amplifier respectively; Two ends of the eighth resistor are electrically connected to the positive input terminal of the third operational amplifier and the cathode of the voltage stabilizing diode respectively; The anode of the voltage stabilizing diode is electrically connected to the output terminal of the third operational amplifier; Two ends of the eighth resistor are electrically connected to the cathode of the voltage stabilizing diode and the positive electrode of the power supply respectively; An inverting input terminal of the third operational amplifier is electrically connected to an output terminal of the differential circuit.

5. The power supply with overload protection according to claim 1, characterized in that: The voltage regulation excitation source includes: a tenth resistor, an eleventh resistor, a second capacitor, a third capacitor and a transistor; Two ends of the tenth resistor are electrically connected to the output end of the Schmitt trigger and the base of the transistor respectively; The two ends of the eleventh resistor are electrically connected to the positive electrode of the power supply and the collector of the transistor respectively; The first end of the second capacitor and the second end of the third capacitor are electrically connected to the emitter of the transistor and the ground respectively, and the second end of the second capacitor is electrically connected to the first end of the third capacitor.

6. The power supply with overload protection according to claim 5, characterized in that: The voltage regulation excitation source further includes: a key switch; The two ends of the key switch are electrically connected to the collector of the transistor and the emitter of the transistor respectively.

7. The power supply with overload protection according to claim 1, characterized in that: The power supply comprises: an adjustable three-terminal voltage regulator, a twelfth resistor, a thirteenth resistor and a fourth capacitor; Two ends of the twelfth resistor are electrically connected to the output end of the adjustable three-terminal regulator and the adjustment end of the adjustable three-terminal regulator, respectively; two ends of the thirteenth resistor are electrically connected to the adjustment end of the adjustable three-terminal regulator and the first end of the fourth capacitor, respectively; The second end of the fourth capacitor is electrically connected to the output end of the voltage-regulated excitation source.

8. The power supply with overload protection according to any one of claims 1 to 7, characterized in that: The power supply with overload protection further includes an indication circuit, which is electrically connected to the output end of the Schmitt trigger.

9. The power supply with overload protection according to any one of claims 1 to 7, characterized in that: The power supply with overload protection further includes an output diode, wherein an anode of the output diode is electrically connected to an end of the sampling resistor away from the output end of the power supply.

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