Overload delay alarm circuit and overload delay alarm device

Abstract

The utility model relates to the technical field of electronic circuits, in particular to an overload delay alarm circuit and an overload delay alarm device. The alarm circuit comprises a power supply circuit and a control circuit; the power supply circuit is used for rectifying commercial power and outputting the commercial power to the control circuit. Wherein the control circuit comprises a thyristor, a light emitting diode, a second triode, an eighth capacitor, a control chip and at least one microswitch; the microswitch is used for closing when the circuit to be detected is overloaded; and the control chip is used for outputting a high-level signal through the output pin to control the light emitting diode to be lightened when detecting that the voltage value on the trigger pin is smaller than a preset value. It can be seen that according to the alarm circuit provided by the invention, tripping and outage cannot be immediately carried out after overload, the light-emitting diode is lightened to send out the alarm information, and the alarm circuit can be applied to some scenes in which the circuit cannot be powered off, but the alarm information must be sent out to indicate that the circuit is overloaded.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to an overload delay alarm circuit and an overload delay alarm device. Background Technology

[0002] To ensure the safe operation of circuits, overload protection is usually required. Overload protection refers to protective devices installed to prevent the main power line from overheating and being damaged due to excessive load. It is commonly used in electrical equipment to prevent equipment damage or safety accidents caused by excessive load.

[0003] Overload protection protects electrical equipment by cutting off power or issuing an alarm when the current exceeds its rated current. For example, in a motor, when the current exceeds a certain value of the rated current, the overload protection element will activate, stopping the motor and protecting it from damage. However, overload protection circuits in related technologies often trip immediately upon detecting an overload, which can easily lead to false triggering. Furthermore, the immediate tripping after a false trigger can affect the equipment's operating efficiency. Utility Model Content

[0004] This application provides an overload delay alarm circuit and an overload delay alarm device to solve the technical problem in related technologies where the circuit breaker trips immediately upon detecting an overload, which can easily lead to false triggering.

[0005] In a first aspect, this utility model provides an overload delay alarm circuit, comprising: a power supply circuit and a control circuit; the input terminal of the power supply circuit is used to receive mains power, and the power supply circuit is used to rectify and regulate the mains power before outputting it to the control circuit;

[0006] The power supply circuit includes an adjustable resistor, a first resistor, a first capacitor, a rectifier bridge, a Zener diode, and a first transistor. The first terminal of the adjustable resistor is connected to the first terminal of the first resistor; the second terminal of the first resistor is connected to the first terminal of the first capacitor; the second terminal of the first capacitor is connected to the first terminal of the primary side of the rectifier bridge; and the second terminal of the primary side of the rectifier bridge is connected to the second terminal of the adjustable resistor. The positive terminal of the secondary side of the rectifier bridge is connected to the negative terminal of the Zener diode, and the positive terminal of the Zener diode is connected to the negative terminal of the secondary side of the rectifier bridge. The control terminal of the first transistor is connected to the positive terminal of the Zener diode, the input terminal of the first transistor is connected to the negative terminal of the Zener diode, and the output terminal of the first transistor is used to output the supply voltage.

[0007] The control circuit includes a thyristor, a light-emitting diode (LED), a second transistor, an eighth capacitor, a control chip, and at least one microswitch. The anode of the LED is connected to the output terminal of the first transistor, the cathode of the LED is connected to the anode of the thyristor, and the cathode of the thyristor is grounded. The output terminal of the first transistor is also connected to the power supply pin of the control chip, and the output terminal of the first transistor is also connected to the base of the second transistor through the at least one microswitch. The emitter of the second transistor is grounded, and the collector of the second transistor is connected to the trigger pin of the control chip. The first terminal of the eighth capacitor is connected to the trigger pin of the control chip, and the second terminal of the eighth capacitor is grounded. The output pin of the control chip is connected to the control electrode of the thyristor.

[0008] The micro switch is used to close when the circuit under test is overloaded; the control chip is used to output an alarm signal through the output pin when the voltage value on the trigger pin is less than a preset value, so as to control the thyristor to conduct and thus make the light-emitting diode light up.

[0009] In one possible design, the control circuit further includes a relay, the positive terminal of which is connected to the positive terminal of the thyristor, and the negative terminal of which is connected to the output terminal of the first transistor; an alarm device is connected to the auxiliary contact of the relay.

[0010] When the thyristor is turned on, the relay is energized to switch the auxiliary contact from a normally open state to a normally closed state, thereby enabling the alarm device to operate.

[0011] In one possible design, the power supply circuit further includes a second capacitor and a third capacitor; the second capacitor is connected in parallel across the Zener diode; the third capacitor is an electrolytic capacitor, with its positive terminal connected to the negative terminal of the Zener diode and its negative terminal connected to the positive terminal of the Zener diode.

[0012] In one possible design, the power supply circuit further includes a fourth capacitor and a fifth capacitor; the fourth capacitor is an electrolytic capacitor, the positive terminal of the fourth capacitor is connected to the output terminal of the first transistor, and the negative terminal of the fourth capacitor is grounded; the first terminal of the fifth capacitor is also connected to the output terminal of the first transistor, and the second terminal of the fifth capacitor is grounded.

[0013] In one possible design, the control circuit further includes a second resistor, a third resistor, and a sixth capacitor; the output terminal of the first transistor is connected to the positive terminal of the light-emitting diode through the second resistor; the output pin of the control chip is connected to the control electrode of the thyristor through the third resistor; the first terminal of the sixth capacitor is connected to the control electrode of the thyristor, and the second terminal of the sixth capacitor is grounded.

[0014] In one possible design, the control circuit further includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and a ninth capacitor;

[0015] The output terminal of the first transistor is connected to the trigger pin of the control chip through the fourth resistor; the output terminal of the first transistor is also connected to at least one micro switch through the fifth resistor;

[0016] The collector of the second transistor is connected to the trigger pin of the control chip through the sixth resistor;

[0017] The output terminal of the first transistor is also connected to the threshold pin and the discharge pin of the control chip through the seventh resistor, the first terminal of the ninth capacitor is connected to the discharge pin of the control chip, and the second terminal of the ninth capacitor is grounded.

[0018] In one possible design, the control chip further includes a reset pin, a power supply pin, and a control power supply pin; the control circuit also includes a seventh capacitor.

[0019] The output terminal of the first transistor is also connected to the reset pin and the power supply pin of the control chip, respectively. The control power supply pin of the control chip is connected to the first terminal of the seventh capacitor, and the second terminal of the seventh capacitor is grounded.

[0020] In one possible design, the control circuit includes three microswitches connected in series, each corresponding to a three-phase detection circuit.

[0021] In one possible design, the control circuit further includes a shunt trip unit, the control terminal of which is connected to the auxiliary contact of the relay.

[0022] Secondly, this application provides an overload delay alarm device, the device including a housing and an overload delay alarm circuit disposed within the housing, the alarm circuit being an overload delay alarm circuit as described in any of the above claims.

[0023] The overload delay alarm circuit provided in the first aspect above includes a power supply circuit and a control circuit. The power supply circuit rectifies the mains power and outputs it to the control circuit. The control circuit includes a thyristor, a light-emitting diode (LED), a second transistor, an eighth capacitor, a control chip, and at least one microswitch. The positive terminal of the LED is connected to the output terminal of the first transistor, the negative terminal of the LED is connected to the positive terminal of the thyristor, and the negative terminal of the thyristor is grounded. The output terminal of the first transistor is also connected to the power supply pin of the control chip, and the output terminal of the first transistor is also connected to the base of the second transistor through at least one microswitch. The emitter of the second transistor is grounded, and the collector of the second transistor is connected to the trigger pin of the control chip. The first terminal of the eighth capacitor is connected to the trigger pin of the control chip, and the second terminal of the eighth capacitor is grounded. The output pin of the control chip is connected to the control electrode of the thyristor. The microswitch is used to close when the circuit under test is overloaded. The control chip, when detecting a voltage value less than a preset value on the trigger pin, outputs a high-level signal through its output pin to control the thyristor to conduct, thereby illuminating the LED. As can be seen, according to the alarm circuit provided in this application, after detecting a circuit overload, the eighth capacitor gradually discharges, then triggers the control chip to output an alarm signal, illuminating the LED. This prevents immediate power tripping after an overload, and the LED's illumination provides an alarm message. This can be applied to scenarios where power to the circuit cannot be cut off, but an alarm message must be issued to indicate an overload.

[0024] The beneficial effects provided in the second aspect and its various possible designs can be found in the first aspect and its various possible implementations, and will not be repeated here. Attached Figure Description

[0025] Figure 1 This is one of the structural schematic diagrams of the overload delay alarm circuit provided in the embodiments of this application;

[0026] Figure 2 This is a second schematic diagram of the overload delay alarm circuit provided in the embodiments of this application. Detailed Implementation

[0027] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c alone can mean: a alone, b alone, c alone, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] The terms “center,” “longitudinal,” “lateral,” “up,” “down,” “left,” “right,” “front,” and “rear,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0029] The terms "connected" and "connected" should be interpreted broadly. For example, in circuit structures, "connected" or "connected" can refer not only to physical connections but also to electrical or signal connections. This could be a direct connection (physical connection) or an indirect connection via at least one intermediate component, as long as the circuit is connected. It could also refer to the internal connection between two components. Similarly, a signal connection can refer to a connection via a circuit or a medium, such as radio waves. Those skilled in the art will understand the specific meaning of these terms in this application based on the specific circumstances.

[0030] The overload protection circuits provided in related technologies usually trip immediately when an overload is detected, causing the circuit or equipment to shut down. This can easily lead to false triggering of the circuit; and the immediate tripping and shutdown after a false trigger will affect the working efficiency of the equipment.

[0031] To overcome the shortcomings of the aforementioned related technologies, this utility model provides an overload delay alarm circuit, which includes a power supply circuit and a control circuit. The power supply circuit rectifies the mains power and outputs it to the control circuit to power it. Upon detecting an overload, the control circuit controls the eighth capacitor to gradually discharge, then triggers the control chip to output an alarm signal. This provides a certain delay, preventing the circuit from immediately tripping and cutting off power. Furthermore, the illumination of the LED can issue an alarm message. This circuit can be applied to scenarios where power to the line cannot be cut off, but an alarm message must be issued to indicate an overload.

[0032] Figure 1 This is one of the structural schematic diagrams of the overload delay alarm circuit provided in the embodiments of this application. Figure 2 For the second schematic diagram of the overload delay alarm circuit provided in the embodiments of this application, please refer to [link / reference]. Figure 1 and Figure 2 As shown, this application provides an overload delay alarm circuit, which includes a power supply circuit 10 and a control circuit 20. The input terminal of the power supply circuit 10 is used to receive mains power, and the power supply circuit 10 is used to rectify and regulate the mains power before outputting it to the control circuit 20. In other words, the power supply circuit 10 converts the received mains power into DC power adapted to the control circuit 20 to power the control circuit 20.

[0033] The power supply circuit 10 includes an adjustable resistor RV1, a first resistor R1, a first capacitor C1, a rectifier bridge DB1, a Zener diode Z1, and a first transistor Z2. The first terminal of the adjustable resistor RV1 is connected to the first terminal of the first resistor R1, the second terminal of the first resistor R1 is connected to the first terminal of the first capacitor C1, the second terminal of the first capacitor C1 is connected to the first terminal of the primary winding of the rectifier bridge DB1, and the second terminal of the primary winding of the rectifier bridge DB1 is connected to the second terminal of the adjustable resistor RV1. The positive terminal V+ of the secondary winding of the rectifier bridge DB1 is connected to the negative terminal of the Zener diode Z1, and the positive terminal of the Zener diode Z1 is connected to the negative terminal V- of the secondary winding of the rectifier bridge DB1. The control terminal of the first transistor Z2 is connected to the positive terminal of the Zener diode Z1, the input terminal of the first transistor Z2 is connected to the negative terminal of the Zener diode Z1, and the output terminal of the first transistor Z2 is used to output the supply voltage VCC.

[0034] The control circuit 20 includes a thyristor Q1, a light-emitting diode (LED), a second transistor Q2, an eighth capacitor C8, a control chip U1, and at least one microswitch. The positive terminal of the LED is connected to the output terminal of the first transistor Z2, and the negative terminal of the LED is connected to the positive terminal of the thyristor Q1. The negative terminal of the thyristor Q1 is grounded to GND. The output terminal of the first transistor Z2 is also connected to the power supply pin VCC of the control chip U1. The output terminal of the first transistor Z2 is also connected to the base of the second transistor Q2 through at least one microswitch. The emitter of the second transistor Q2 is grounded to GND, and the collector of the second transistor Q2 is connected to the trigger pin TRIG of the control chip U1. The first terminal of the eighth capacitor C8 is connected to the trigger pin TRIG of the control chip U1, and the second terminal of the eighth capacitor C8 is grounded to GND. The output pin of the control chip U1 is connected to the control electrode of the thyristor Q1.

[0035] Among them, the micro switch is used to close when the circuit under test is overloaded; the control chip U1 is used to output an alarm signal through the output pin OUTP when the voltage value on the trigger pin TRIG is less than the preset value, so as to control the thyristor Q1 to conduct, thereby making the light-emitting diode LED light up.

[0036] The overload delay alarm circuit provided in this embodiment includes a power supply circuit 10 and a control circuit 20. The power supply circuit 10 rectifies the mains power and outputs it to the control circuit 20 to power the control circuit 20. After detecting an overload, the control circuit 20 controls the eighth capacitor C8 to gradually discharge, and then triggers the control chip U1 to output an alarm signal. This provides a certain delay, preventing the circuit from immediately tripping and cutting off power. Furthermore, the LED illuminates to issue an alarm message. This circuit can be applied to scenarios where power to the line cannot be cut off, but an alarm message must be issued to indicate an overload.

[0037] Among them, the first resistor R1 is a current-limiting resistor, which plays a role in limiting the current in the circuit; the first capacitor C1 is a voltage-reducing capacitor, which plays a role in reducing the voltage.

[0038] In this embodiment, the rectifier bridge DB1 is used to rectify the input two-phase mains power, that is, to rectify the two-phase AC power into DC power so that it can directly power the control circuit 20.

[0039] In this embodiment, the first transistor Z2 is a voltage-regulating transistor. Its input terminal Vin is used to receive the input voltage signal, and its output terminal Vout is used to output the regulated voltage signal. This voltage-regulating transistor can adjust the magnitude of the input voltage signal to obtain the power supply voltage VCC adapted to the control circuit.

[0040] In some embodiments, the power supply circuit 10 further includes a second capacitor C2 and a third capacitor C3; the second capacitor C2 is connected in parallel across the Zener diode Z1; wherein, the third capacitor C3 is an electrolytic capacitor, the positive terminal of the third capacitor C3 is connected to the negative terminal of the Zener diode Z1, and the negative terminal of the third capacitor C3 is connected to the positive terminal of the Zener diode Z1.

[0041] In this embodiment, the second capacitor C2 and the third capacitor C3 are filter capacitors, which play a filtering role and are mainly used to filter the DC signal output by the rectifier bridge DB1.

[0042] In some embodiments, the power supply circuit 10 further includes a fourth capacitor C4 and a fifth capacitor C5; wherein, the fourth capacitor C4 is an electrolytic capacitor, the positive terminal of the fourth capacitor C4 is connected to the output terminal of the first transistor Z2, and the negative terminal of the fourth capacitor C4 is grounded to GND; the first terminal of the fifth capacitor C5 is also connected to the output terminal of the first transistor Z2, and the second terminal of the fifth capacitor C5 is grounded to GND.

[0043] In this embodiment, the fourth capacitor C4 and the fifth capacitor C5 are filter capacitors. The fourth capacitor C4 and the fifth capacitor C5 are mainly used to filter the regulated voltage signal output by the first transistor Z2.

[0044] In some embodiments, the control circuit 20 further includes a relay K1, the positive terminal of which is connected to the positive terminal of the thyristor Q1, and the negative terminal of which is connected to the output terminal of the first transistor Z2; an alarm device is connected to the auxiliary contact of the relay K1. This alarm device can be an audible alarm or a combined audible and visual alarm, such as a buzzer. When the thyristor Q1 is turned on, the relay K1 is energized, causing the auxiliary contact to switch from a normally open state to a normally closed state, thereby activating the alarm device.

[0045] In some embodiments, the control circuit 20 further includes a second resistor R2, a third resistor R3, and a sixth capacitor C6; the output terminal of the first transistor Z2 is connected to the positive terminal of the light-emitting diode LED through the second resistor R2; the output pin of the control chip 20 is connected to the control electrode of the thyristor Q1 through the third resistor R3; the first terminal of the sixth capacitor C6 is connected to the control electrode of the thyristor Q1, and the second terminal of the sixth capacitor C6 is grounded to GND.

[0046] In this embodiment, the second resistor R2 and the third resistor R3 are both current-limiting resistors, which play a role in limiting the current in the circuit.

[0047] In this embodiment, the sixth capacitor C6 is an anti-interference capacitor. The sixth capacitor C6 can ensure the potential of the control electrode of the first transistor Z2, so as to ensure the stability when the thyristor Q1 is turned on.

[0048] In this embodiment, the thyristor Q1 is a current-mode thyristor, specifically a silicon controlled rectifier (SCR). The control chip U1 outputs an alarm signal through its output pin OUTP. For example, the control chip U1 outputs a high-level signal through its output pin OUTP. This high-level signal triggers the SCR Q1 to conduct. After the SCR Q1 conducts, the LED turns on, and simultaneously, the relay K1 is energized. The auxiliary contact of the relay K1 closes, thus activating the alarm device.

[0049] In some embodiments, the control circuit 20 further includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and a ninth capacitor C9.

[0050] The output of the first transistor Z2 is connected to the TRIG trigger pin of the control chip U1 via the fourth resistor R4; the output of the first transistor Z2 is also connected to at least one microswitch via the fifth resistor R5. The fourth resistor R4 and the fifth resistor R5 also serve to limit current in their respective branches.

[0051] In this circuit, the collector of the second transistor Q2 is connected to the trigger pin TRIG of the control chip U1 via the sixth resistor R6; the output of the first transistor Z2 is also connected to the threshold pin THR-S and the discharge pin DISC of the control chip U1 via the seventh resistor R7; the first terminal of the ninth capacitor C9 is connected to the discharge pin DISC of the control chip U1, and the second terminal of the ninth capacitor C9 is grounded to GND. The sixth resistor R6 and the seventh resistor R7 also serve as current limiters in their respective branches.

[0052] In one embodiment, the control chip U1 further includes a reset pin REST, a power supply pin VCC, and a control power supply pin CON-V; the control circuit 20 further includes a seventh capacitor C7. The output terminal of the first transistor Z2 is connected to the reset pin REST and the power supply pin VCC of the control chip U1, respectively. The control power supply pin CON-V of the control chip U1 is connected to the first terminal of the seventh capacitor C7, and the second terminal of the seventh capacitor C7 is grounded to GND.

[0053] Understandably, the extension time after the control circuit 20 is triggered can be adjusted by adjusting the parameters of the eighth capacitor C8, the sixth resistor R6, and the seventh resistor R7.

[0054] In some embodiments, only one microswitch S1 is connected in series in the control circuit 20, and one microswitch corresponds to one circuit to be detected. For example, when it is only necessary to monitor whether one circuit is overloaded, only one microswitch can be set. When the monitored circuit is overloaded, the bimetallic strip in the overload mechanism will bend and deform, causing the microswitch to close, thereby turning on the second transistor Q2.

[0055] In some embodiments, two microswitches are connected in series in the control circuit 20, corresponding to two circuits to be detected. For example, when it is necessary to monitor whether two circuits are overloaded, two microswitches can be set. When the monitored circuit is overloaded, the bimetallic strip in the overload mechanism will bend and deform, causing the two microswitches to close, thereby turning on the second transistor Q2.

[0056] See Figure 1 and Figure 2 As shown, the control circuit 20 includes three microswitches, S1, S2, and S3, connected in series. Each microswitch corresponds to one of the three phases of the circuit to be detected, for example, phases A, B, and C. When the product current is overloaded, microswitches S1, S2, and S3 close, causing the second transistor Q2 to conduct, which in turn causes the eighth capacitor C8 to discharge. After a period of time, when the trigger pin TRIG of the control chip U1 detects that the voltage on it is lower than a preset value, a high-level signal is output through the output pin OUTP. Specifically, for example, when the trigger pin TRIG of the control chip U1 detects that the voltage on it is lower than Vcc / 3, a high-level signal is output through the output pin OUTP.

[0057] In one embodiment, the control circuit 20 further includes a shunt trip unit, the control terminal of which is connected to the auxiliary contact of relay K1. When the auxiliary contact of relay K1 is closed, the shunt trip unit is activated.

[0058] According to the overload delay alarm circuit provided in this embodiment, under normal circumstances, microswitches S1, S2, and S3 are open. At this time, the eighth capacitor C8 at the trigger pin TRIG terminal of the control chip U1 is fully charged, and the voltage on the trigger pin TRIG is greater than Vcc / 3. At this time, the output pin OUTP of the control chip U1 outputs a low-level signal, the thyristor Q1 is open, the overload LED is off, and the relay K1 does not work. When the product experiences an overload, the overload mechanism closes switches S1, S2, and S3. At this time, the second transistor Q2 turns on, causing the eighth capacitor C8 to discharge. After a certain time delay, when the voltage of the trigger pin TRIG of the control chip U1 is lower than Vcc / 3, the output pin OUTP of the trigger pin TRIG flips, outputting a high-level signal to trigger the thyristor Q1 to conduct. After the thyristor Q1 conducts, the overload LED lights up, the relay K1 is energized, and a pair of normally open and normally closed passive auxiliary contacts change from normally open to normally closed and from normally closed to normally open. At this time, the user sees the alarm signal and takes measures to eliminate the fault.

[0059] In one embodiment, the user can adjust the extension time after the control circuit 20 is triggered by adjusting the parameters of the eighth capacitor C8, the sixth resistor R6, and the seventh resistor R7.

[0060] According to the overload delay alarm circuit provided in this embodiment, when an overload of the line current is detected, it will not immediately trip to shut down the line. Instead, after a certain delay, it will output a high-level trigger signal to control the LED or alarm device to conduct, thereby issuing an alarm message. This firstly avoids the situation of circuit false triggering, and secondly avoids the device from immediately losing power. It can also issue an alarm message, which can be applied to scenarios where the line cannot be powered off, but an alarm message must be issued to indicate that the line is overloaded.

[0061] This application provides an overload delay alarm device, which includes a housing and an overload delay alarm circuit disposed within the housing. The alarm circuit is an overload delay alarm circuit as described in any of the above claims.

[0062] It is understood that the overload delay alarm device provided in this embodiment is equivalent to encapsulating the overload delay alarm circuits provided in the above embodiments. Therefore, the overload delay alarm device has the same technical effect as the overload delay alarm circuits described above, and will not be repeated here.

[0063] Finally, it should be noted that the above embodiments are merely specific implementations of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An overload delay alarm circuit, characterized in that, include: A power supply circuit and a control circuit; the input terminal of the power supply circuit is used to receive mains power, and the power supply circuit is used to rectify and regulate the mains power before outputting it to the control circuit; The power supply circuit includes an adjustable resistor, a first resistor, a first capacitor, a rectifier bridge, a Zener diode, and a first transistor. The first terminal of the adjustable resistor is connected to the first terminal of the first resistor; the second terminal of the first resistor is connected to the first terminal of the first capacitor; the second terminal of the first capacitor is connected to the first terminal of the primary side of the rectifier bridge; and the second terminal of the primary side of the rectifier bridge is connected to the second terminal of the adjustable resistor. The positive terminal of the secondary side of the rectifier bridge is connected to the negative terminal of the Zener diode, and the positive terminal of the Zener diode is connected to the negative terminal of the secondary side of the rectifier bridge. The control terminal of the first transistor is connected to the positive terminal of the Zener diode, the input terminal of the first transistor is connected to the negative terminal of the Zener diode, and the output terminal of the first transistor is used to output the supply voltage. The control circuit includes a thyristor, a light-emitting diode (LED), a second transistor, an eighth capacitor, a control chip, and at least one microswitch. The anode of the LED is connected to the output terminal of the first transistor, the cathode of the LED is connected to the anode of the thyristor, and the cathode of the thyristor is grounded. The output terminal of the first transistor is also connected to the power supply pin of the control chip, and the output terminal of the first transistor is also connected to the base of the second transistor through the at least one microswitch. The emitter of the second transistor is grounded, and the collector of the second transistor is connected to the trigger pin of the control chip. The first terminal of the eighth capacitor is connected to the trigger pin of the control chip, and the second terminal of the eighth capacitor is grounded. The output pin of the control chip is connected to the control electrode of the thyristor. The micro switch is used to close when the circuit under test is overloaded; the control chip is used to output an alarm signal through the output pin when the voltage value on the trigger pin is less than a preset value, so as to control the thyristor to conduct and thus make the light-emitting diode light up.

2. The overload delay alarm circuit according to claim 1, characterized in that, The control circuit also includes a relay, the positive terminal of which is connected to the positive terminal of the thyristor, and the negative terminal of which is connected to the output terminal of the first transistor; an alarm device is connected to the auxiliary contact of the relay. When the thyristor is turned on, the relay is energized to switch the auxiliary contact from a normally open state to a normally closed state, thereby enabling the alarm device to operate.

3. The overload delay alarm circuit according to claim 1 or 2, characterized in that, The power supply circuit also includes a second capacitor and a third capacitor; the second capacitor is connected in parallel across the Zener diode; the third capacitor is an electrolytic capacitor, the positive terminal of the third capacitor is connected to the negative terminal of the Zener diode, and the negative terminal of the third capacitor is connected to the positive terminal of the Zener diode.

4. The overload delay alarm circuit according to claim 1 or 2, characterized in that, The power supply circuit also includes a fourth capacitor and a fifth capacitor; the fourth capacitor is an electrolytic capacitor, the positive terminal of the fourth capacitor is connected to the output terminal of the first transistor, and the negative terminal of the fourth capacitor is grounded; the first terminal of the fifth capacitor is also connected to the output terminal of the first transistor, and the second terminal of the fifth capacitor is grounded.

5. The overload delay alarm circuit according to claim 1 or 2, characterized in that, The control circuit further includes a second resistor, a third resistor, and a sixth capacitor; the output terminal of the first transistor is connected to the positive terminal of the light-emitting diode through the second resistor; the output pin of the control chip is connected to the control electrode of the thyristor through the third resistor; the first terminal of the sixth capacitor is connected to the control electrode of the thyristor, and the second terminal of the sixth capacitor is grounded.

6. The overload delay alarm circuit according to claim 1 or 2, characterized in that, The control circuit also includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and a ninth capacitor; The output terminal of the first transistor is connected to the trigger pin of the control chip through the fourth resistor; the output terminal of the first transistor is also connected to at least one micro switch through the fifth resistor; The collector of the second transistor is connected to the trigger pin of the control chip through the sixth resistor; The output terminal of the first transistor is also connected to the threshold pin and the discharge pin of the control chip through the seventh resistor, the first terminal of the ninth capacitor is connected to the discharge pin of the control chip, and the second terminal of the ninth capacitor is grounded.

7. The overload delay alarm circuit according to claim 1 or 2, characterized in that, The control chip also includes a reset pin, a power supply pin, and a control power supply pin; the control circuit also includes a seventh capacitor; The output terminal of the first transistor is also connected to the reset pin and the power supply pin of the control chip, respectively. The control power supply pin of the control chip is connected to the first terminal of the seventh capacitor, and the second terminal of the seventh capacitor is grounded.

8. The overload delay alarm circuit according to claim 1 or 2, characterized in that, The control circuit includes three microswitches connected in series, and each of the three microswitches corresponds to a three-phase detection circuit.

9. The overload delay alarm circuit according to claim 2, characterized in that, The control circuit also includes a shunt trip unit, the control terminal of which is connected to the auxiliary contact of the relay.

10. An overload delay alarm device, characterized in that, The device includes a housing and an overload delay alarm circuit disposed within the housing, wherein the alarm circuit is an overload delay alarm circuit as described in any one of claims 1-9.

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