A failure detection circuit, a heat generating driving circuit and a hot air gun for silicon controlled rectifier

Abstract

The application discloses a failure detection circuit for silicon-controlled rectifier, a heating driving circuit and a hot air gun. The failure detection circuit comprises a heating circuit, a voltage reduction and voltage division circuit, a detection switch circuit and a pulse width generation circuit. The heating circuit is used for outputting electric energy input by an external alternating power supply to a heating load through the silicon-controlled rectifier. The voltage reduction and voltage division circuit is used for sampling and reducing the electric energy signal of the heating load to obtain a load voltage waveform signal. The detection switch circuit is used for converting the load voltage waveform signal into a first direct current signal. The pulse width generation circuit is used for obtaining a first pulse signal according to the first direct current signal. Since the pulse width and frequency of the first pulse signal are related to the amplitude and frequency of the load voltage waveform signal, the failure detection circuit can detect the failure of the silicon-controlled rectifier according to the pulse width and frequency of the first pulse signal, and thus the working state of the silicon-controlled rectifier can be detected on line, so that the working reliability and safety of the heating driving circuit are improved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a failure detection circuit, a heating drive circuit, and a hot air gun for thyristors. Background Technology

[0002] Hot air guns are a common basic tool in industry and home appliances. As users' requirements for the operating environment become more demanding, the power of hot air guns is increasing, and the power supply voltage of the heating wire is also increasing. Consequently, it is necessary to add online detection functions to the heating drive circuit to improve the reliability of the safety protection measures of heating tools. Summary of the Invention

[0003] The technical problem this application aims to solve is how to improve the reliability of safety protection measures for heating tools.

[0004] According to the first aspect, one embodiment provides a failure detection circuit for a silicon controlled rectifier (SCR), including a heating circuit, a step-down voltage divider circuit, a detection switch circuit, and a pulse width generation circuit. The heating circuit includes a thyristor Q1 and a heating load RL. The thyristor Q1 is used to output electrical energy input from an external AC power source to the heating load RL. The heating load RL is used to convert electrical energy into heat energy. The step-down voltage divider circuit is connected to the power output terminal of the thyristor Q1 and is used to step down and sample the power signal of the heat load RL to obtain the load voltage waveform signal. The detection switch circuit is connected to the step-down voltage divider circuit and is used to convert the load voltage waveform signal output by the step-down voltage divider circuit into a first DC signal. The pulse width generation circuit is connected to the step-down voltage divider circuit and is used to obtain a first pulse signal based on the first DC signal; the pulse width and frequency of the first pulse signal are related to the amplitude and frequency of the load voltage waveform signal. The failure detection circuit is used to detect failures in the thyristor Q1 based on the pulse width and frequency of the first pulse signal.

[0005] In one embodiment, the power input terminal of the thyristor Q1 is used for the input of the external AC power supply, and the power output terminal of the thyristor Q1 is connected to the heat load RL and the step-down voltage divider circuit. One end of the heating load RL is connected to the output terminal of the thyristor Q1, and the other end is grounded.

[0006] In one embodiment, the step-down voltage divider circuit includes a first resistor R21, a second resistor R22, a third resistor R23, and a fourth resistor R24 ​​connected in series. One end of the first resistor R21 is connected to the second resistor R22 and the detection switch circuit, and the other end is grounded. One end of the fourth resistor R24 ​​is connected to the third resistor R23, and the other end is connected to the heating circuit.

[0007] In one embodiment, the detection switch circuit includes a first semiconductor switch Q2 and a second semiconductor switch Q3; The first semiconductor switch Q2 and the second semiconductor switch Q3 are turned on alternately to convert the load voltage waveform signal into a first DC signal.

[0008] In one embodiment, the first semiconductor switch Q2 and the second semiconductor switch Q3 are transistors; The base of the first semiconductor switch Q2 is connected to the step-down voltage divider circuit, the emitter of the first semiconductor switch Q2 is grounded, and the collector of the first semiconductor switch Q2 is connected to the pulse width generation circuit. The emitter of the second semiconductor switch Q3 is connected to the step-down voltage divider circuit, the collector of the second semiconductor switch Q3 is connected to the pulse width generation circuit, and the base of the second semiconductor switch Q3 is connected to the emitter of the first semiconductor switch Q2.

[0009] In one embodiment, the first semiconductor switch Q2 and the second semiconductor switch Q3 are MOS transistors; The gate of the first semiconductor switch Q2 is connected to the step-down voltage divider circuit, the source of the first semiconductor switch Q2 is grounded, and the drain of the first semiconductor switch Q2 is connected to the pulse width generation circuit. The drain of the second semiconductor switch Q3 is connected to the step-down voltage divider circuit, the source of the second semiconductor switch Q3 is connected to the pulse width generation circuit, and the gate of the second semiconductor switch Q3 is connected to the drain of the first semiconductor switch Q2.

[0010] In one embodiment, the pulse width generation circuit includes a transistor Q4, a fifth resistor R41, a sixth resistor R42, and a seventh resistor R43; The emitter of the transistor Q4 is used as the input of a preset first operating power supply Vo, and the collector of the transistor Q4 is used to output the first pulse signal. One end of the fifth resistor R41 is connected to the collector of the transistor Q4, and the other end is grounded; One end of the sixth resistor R42 is connected to the detection switch circuit, and the other end is connected to the base of the transistor Q4; One end of the seventh resistor R43 is connected to the base of the transistor Q4, and the other end is connected to the emitter of the transistor Q4.

[0011] In one embodiment, the pulse width generation circuit includes an optocoupler U1, an eighth resistor R44, a ninth resistor R45, and a tenth resistor R46; The optocoupler U1 includes an input first connection terminal, an input second connection terminal, an output first connection terminal, and an output second connection terminal. The output first connection terminal of the optocoupler U1 is used to output the first pulse signal, and the output second connection terminal of the optocoupler U1 is grounded. One end of the eighth resistor R44 is connected to the detection switch circuit, and the other end is connected to the second input terminal of the optocoupler U1. One end of the ninth resistor R45 is connected to the first input terminal of the optocoupler U1, and the other end is used for the input of a preset first working power supply Vo. One end of the tenth resistor R46 is connected to the first output connection terminal of the optocoupler U1, and the other end is used for the input of a preset second working power supply Vp.

[0012] According to a second aspect, one embodiment provides a heat-generating driving circuit, including the failure detection circuit as described in the first aspect.

[0013] According to a third aspect, one embodiment provides a hot air gun including a failure detection circuit as described in the first aspect.

[0014] According to the heating drive circuit of the above embodiment, the power signal output by the thyristor is sequentially sampled by step-down, converted to DC and pulse signal to obtain the first pulse signal. Since the pulse width and frequency of the first pulse signal are related to the amplitude and frequency of the load voltage waveform signal, the failure detection circuit can perform failure detection on the thyristor Q1 based on the pulse width and frequency of the first pulse signal, thereby realizing online detection of the working state of the thyristor to improve the working reliability and safety of the heating drive circuit. Attached Figure Description

[0015] Figure 1 This is a functional structure diagram of a failure detection circuit in one embodiment; Figure 2 This is a schematic diagram of the circuit connection of the failure detection circuit in one embodiment; Figure 3 This is a schematic diagram of the circuit connection for the detection switch circuit in another embodiment; Figure 4 This is a schematic diagram of the circuit connection of the pulse width generation circuit in another embodiment; Figure 5This is a waveform comparison diagram of the load voltage waveform signal and the first pulse signal in one embodiment. Detailed Implementation

[0016] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0017] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0018] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. Unless otherwise specified, the terms "connection" and "linkage" used in this application include both direct and indirect connections (linkages).

[0019] Currently, heating control methods for most equipment primarily utilize thyristors to control high-voltage AC power. Due to the high AC voltage and increasing equipment power, the heat generated by the thyristors also increases significantly. Especially under harsh operating conditions, internal breakdown and short circuits can easily occur, leading to abnormal temperature control. If the equipment remains in full-power heating mode, various safety hazards can easily arise. In one embodiment of this application, a thyristor failure detection circuit is introduced to form a control closed loop, thereby enhancing the safety and reliability of the heating drive circuit.

[0020] Example 1: Please refer to Figure 1This is a functional structure diagram of a failure detection circuit in one embodiment. The failure detection circuit includes a heating circuit 1, a step-down voltage divider circuit 2, a detection switch circuit 3, and a pulse width generation circuit 4. The heating circuit 1 includes a silicon controlled rectifier (SCR) Q1 and a heating load RL. The SCR Q1 outputs electrical energy from an external AC power supply to the heating load RL, which converts the electrical energy into heat energy. The step-down voltage divider circuit 2 is connected to the output terminal of the SCR Q1 and is used to sample the electrical energy signal from the heating load RL by stepping down the voltage to obtain a load voltage waveform signal. The detection switch circuit 3 is connected to the step-down voltage divider circuit 2 and is used to convert the load voltage waveform signal output by the step-down voltage divider circuit 2 into a first DC signal. The pulse width generation circuit 4 is connected to the step-down voltage divider circuit 3 and is used to obtain a first pulse signal based on the first DC signal. The pulse width and frequency of the first pulse signal are related to the amplitude and frequency of the load voltage waveform signal. The failure detection circuit is used to perform failure detection on the SCR Q1 based on the pulse width and frequency of the first pulse signal.

[0021] Please refer to Figure 2 This is a circuit connection diagram of the failure detection circuit in one embodiment. The power input terminal of the thyristor Q1 is used for the input of an external AC power supply, and the power output terminal of the thyristor Q1 is connected to the heating load RL and the step-down voltage divider circuit 2. One end of the heating load RL (heating wire) is connected to the output terminal of the thyristor Q1, and the other end is grounded. The live wire terminal AC-L of the external AC power supply is connected to the power input terminal, and the neutral wire terminal AC-N of the external AC power supply is connected to the ground terminal of the heating load RL. The control terminal H of the thyristor Q1 is used for the input of the switch control signal.

[0022] The step-down voltage divider circuit 2 includes a first resistor R21, a second resistor R22, a third resistor R23, and a fourth resistor R24 ​​connected in series. One end of the first resistor R21 is connected to the second resistor R22 and the detection switch circuit 3, and the other end is grounded. One end of the fourth resistor R24 ​​is connected to the third resistor R23, and the other end is connected to the heating circuit 1.

[0023] The detection switch circuit 3 includes a first semiconductor switch Q2 and a second semiconductor switch Q3. The first semiconductor switch Q2 and the second semiconductor switch Q3 are alternately turned on to convert the load voltage waveform signal into a first DC signal. In one embodiment, the first semiconductor switch Q2 and the second semiconductor switch Q3 are transistors. The base of the first semiconductor switch Q2 is connected to the step-down voltage divider circuit 2, the emitter of the first semiconductor switch Q2 is grounded, and the collector of the first semiconductor switch Q2 is connected to the pulse width generation circuit 4. The emitter of the second semiconductor switch Q3 is connected to the step-down voltage divider circuit 2, the collector of the second semiconductor switch Q3 is connected to the pulse width generation circuit 4, and the base of the second semiconductor switch Q3 is connected to the emitter of the first semiconductor switch Q2.

[0024] Please refer to Figure 3 The diagram below shows the circuit connection of the detection switch circuit in another embodiment. In one embodiment, the first semiconductor switch Q2 and the second semiconductor switch Q3 are MOS transistors. The gate of the first semiconductor switch Q2 is connected to the step-down voltage divider circuit 2, the source of the first semiconductor switch Q2 is grounded, and the drain of the first semiconductor switch Q2 is connected to the pulse width generation circuit 4. The drain of the second semiconductor switch Q3 is connected to the step-down voltage divider circuit 2, the source of the second semiconductor switch Q3 is connected to the pulse width generation circuit 4, and the gate of the second semiconductor switch Q3 is connected to the drain of the first semiconductor switch Q2.

[0025] In one embodiment, the pulse width generation circuit 4 includes a transistor Q4, a fifth resistor R41, a sixth resistor R42, and a seventh resistor R43. The emitter of transistor Q4 is used as the input of a preset first operating power supply Vo, and the collector of transistor Q4 is used to output a first pulse signal. One end of the fifth resistor R41 is connected to the collector of transistor Q4, and the other end is grounded. One end of the sixth resistor R42 is connected to the detection switch circuit 3, and the other end is connected to the base of transistor Q4. One end of the seventh resistor R43 is connected to the base of transistor Q4, and the other end is connected to the emitter of transistor Q4.

[0026] Please refer to Figure 4 The diagram below illustrates the circuit connection of a pulse width generation circuit in another embodiment. The pulse width generation circuit includes an optocoupler U1, an eighth resistor R44, a ninth resistor R45, and a tenth resistor R46. The optocoupler U1 includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first output terminal of the optocoupler U1 is used to output a first pulse signal (ZPS), and the second output terminal of the optocoupler U1 is grounded. One end of the eighth resistor R44 is connected to the detection switch circuit 3, and the other end is connected to the second input terminal of the optocoupler U1. One end of the ninth resistor R45 is connected to the first input terminal of the optocoupler U1, and the other end is used as the input of a preset first operating power supply Vo. In one embodiment, the voltage value of the first operating power supply Vo is 3.3V. One end of the tenth resistor R46 is connected to the first output terminal of the optocoupler U1, and the other end is used as the input of a preset second operating power supply Vp. In one embodiment, the voltage value of the second operating power supply Vp is 5V.

[0027] One embodiment of this application also discloses a heat-generating driving circuit, including the failure detection circuit described above.

[0028] One embodiment of this application also discloses a hot air gun, including the failure detection circuit described above.

[0029] To facilitate understanding of the working principle of the failure detection circuit disclosed in the embodiments of this application, the following will use... Figure 1 The following describes the workflow of a failure detection circuit using an example: Please refer to Figure 5 This is a waveform comparison diagram of the load voltage waveform signal and the first pulse signal in one embodiment. When the thyristor Q1 is turned on, it outputs AC power to the load resistor RL. The AC power of the load resistor RL is stepped down and divided by the first resistor R21, the second resistor R22, the third resistor R23, and the fourth resistor R24 ​​before being output to the step-down voltage divider circuit 2. The first semiconductor switch Q2 and the second semiconductor switch Q3 of the step-down voltage divider circuit 2 are turned on alternately. When the load voltage waveform signal is in the positive half-cycle of AC, the second semiconductor switch Q3 is turned off. When the base current input to the first semiconductor switch Q2 is less than the conduction current of the first semiconductor switch Q2, the first semiconductor switch Q2 is turned off. At this time, the current cannot flow to the ground terminal through the sixth resistor R42 and the seventh resistor R43, causing the transistor Q4 to be turned off, and the output first pulse signal (ZPS) is low. As the AC voltage increases, when the base current input to the first semiconductor switch Q2 is greater than its on-state current, Q2 turns on. At this time, current flows through the sixth resistor R42 and the seventh resistor R43, and through Q2, to the ground terminal, causing transistor Q4 to turn on. The output first pulse signal (ZPS) is then high. When the load voltage waveform is in the negative half-cycle of AC, Q2 turns off. When the base current input to the second semiconductor switch Q3 is less than its on-state current, Q3 turns off. Current cannot flow through the sixth resistor R42 and the seventh resistor R43 to the ground terminal, causing transistor Q4 to turn off. The output first pulse signal (ZPS) is then low. As the AC voltage decreases, when the base current input to the second semiconductor switch Q3 exceeds its on-state current, Q3 turns on. At this point, current flows through the sixth resistor R42, the seventh resistor R43, and the first semiconductor switch Q2 to ground, causing transistor Q4 to turn on. The output first pulse signal (ZPS) then becomes high. By detecting this first output pulse signal (square wave signal) using an MCU, it can be determined whether the thyristor Q1 is malfunctioning.

[0030] In the above embodiment, the bases and emitters of two N-type transistors (first semiconductor switch Q2 and second semiconductor switch Q3) are connected together to form an electronic switch that can detect the AC output voltage of the thyristor. This electronic switch controls the conduction and cutoff of the P-type transistor, thereby outputting a pulse width signal (first pulse signal). The MCU detects this first pulse signal to determine whether the output of the thyristor Q1 is normal. Then, by comparing it with the thyristor control signal H, a closed-loop control is formed to realize the online detection function of the thyristor Q1.

[0031] This application discloses a failure detection circuit for a thyristor, including a heating circuit, a step-down voltage divider circuit, a detection switch circuit, and a pulse width generation circuit. The heating circuit outputs electrical energy from an external AC power supply to a heating load via the thyristor. The step-down voltage divider circuit samples the electrical energy signal from the heating load at a reduced voltage to obtain a load voltage waveform signal. The detection switch circuit converts the load voltage waveform signal into a first DC signal. The pulse width generation circuit obtains a first pulse signal based on the first DC signal. Since the pulse width and frequency of the first pulse signal are related to the amplitude and frequency of the load voltage waveform signal, the failure detection circuit can perform failure detection on the thyristor Q1 based on the pulse width and frequency of the first pulse signal. This enables online detection of the thyristor's operating status, improving the reliability and safety of the heating drive circuit.

[0032] The above examples illustrate this application only to aid understanding and are not intended to limit its scope. Those skilled in the art to which this application pertains can make various simple deductions, modifications, or substitutions based on the ideas presented.

Claims

1. A failure detection circuit for a silicon controlled rectifier (SCR), characterized in that, It includes a heating circuit, a voltage divider circuit, a detection switch circuit, and a pulse width generation circuit; The heating circuit includes a thyristor Q1 and a heating load RL. The thyristor Q1 is used to output electrical energy input from an external AC power source to the heating load RL. The heating load RL is used to convert electrical energy into heat energy. The step-down voltage divider circuit is connected to the power output terminal of the thyristor Q1 and is used to step down and sample the power signal of the heat load RL to obtain the load voltage waveform signal. The detection switch circuit is connected to the step-down voltage divider circuit and is used to convert the load voltage waveform signal output by the step-down voltage divider circuit into a first DC signal. The pulse width generation circuit is connected to the step-down voltage divider circuit and is used to obtain a first pulse signal based on the first DC signal; the pulse width and frequency of the first pulse signal are related to the amplitude and frequency of the load voltage waveform signal. The failure detection circuit is used to detect failures in the thyristor Q1 based on the pulse width and frequency of the first pulse signal.

2. The failure detection circuit as described in claim 1, characterized in that, The power input terminal of the thyristor Q1 is used for the input of the external AC power supply, and the power output terminal of the thyristor Q1 is connected to the heat load RL and the step-down voltage divider circuit. One end of the heating load RL is connected to the output terminal of the thyristor Q1, and the other end is grounded.

3. The failure detection circuit as described in claim 1, characterized in that, The step-down voltage divider circuit includes a first resistor R21, a second resistor R22, a third resistor R23, and a fourth resistor R24 ​​connected in series. One end of the first resistor R21 is connected to the second resistor R22 and the detection switch circuit, and the other end is grounded. One end of the fourth resistor R24 ​​is connected to the third resistor R23, and the other end is connected to the heating circuit.

4. The failure detection circuit as described in claim 1, characterized in that, The detection switch circuit includes a first semiconductor switch Q2 and a second semiconductor switch Q3; The first semiconductor switch Q2 and the second semiconductor switch Q3 are turned on alternately to convert the load voltage waveform signal into a first DC signal.

5. The failure detection circuit as described in claim 4, characterized in that, The first semiconductor switch Q2 and the second semiconductor switch Q3 are transistors; The base of the first semiconductor switch Q2 is connected to the step-down voltage divider circuit, the emitter of the first semiconductor switch Q2 is grounded, and the collector of the first semiconductor switch Q2 is connected to the pulse width generation circuit. The emitter of the second semiconductor switch Q3 is connected to the step-down voltage divider circuit, the collector of the second semiconductor switch Q3 is connected to the pulse width generation circuit, and the base of the second semiconductor switch Q3 is connected to the emitter of the first semiconductor switch Q2.

6. The failure detection circuit as described in claim 4, characterized in that, The first semiconductor switch Q2 and the second semiconductor switch Q3 are MOSFETs; The gate of the first semiconductor switch Q2 is connected to the step-down voltage divider circuit, the source of the first semiconductor switch Q2 is grounded, and the drain of the first semiconductor switch Q2 is connected to the pulse width generation circuit. The drain of the second semiconductor switch Q3 is connected to the step-down voltage divider circuit, the source of the second semiconductor switch Q3 is connected to the pulse width generation circuit, and the gate of the second semiconductor switch Q3 is connected to the drain of the first semiconductor switch Q2.

7. The failure detection circuit as described in claim 1, characterized in that, The pulse width generation circuit includes a transistor Q4, a fifth resistor R41, a sixth resistor R42, and a seventh resistor R43; The emitter of the transistor Q4 is used as the input of a preset first operating power supply Vo, and the collector of the transistor Q4 is used to output the first pulse signal. One end of the fifth resistor R41 is connected to the collector of the transistor Q4, and the other end is grounded; One end of the sixth resistor R42 is connected to the detection switch circuit, and the other end is connected to the base of the transistor Q4; One end of the seventh resistor R43 is connected to the base of the transistor Q4, and the other end is connected to the emitter of the transistor Q4.

8. The failure detection circuit as described in claim 1, characterized in that, The pulse width generation circuit includes an optocoupler U1, an eighth resistor R44, a ninth resistor R45, and a tenth resistor R46; The optocoupler U1 includes an input first connection terminal, an input second connection terminal, an output first connection terminal, and an output second connection terminal. The output first connection terminal of the optocoupler U1 is used to output the first pulse signal, and the output second connection terminal of the optocoupler U1 is grounded. One end of the eighth resistor R44 is connected to the detection switch circuit, and the other end is connected to the second input terminal of the optocoupler U1. One end of the ninth resistor R45 is connected to the first input terminal of the optocoupler U1, and the other end is used for the input of a preset first working power supply Vo. One end of the tenth resistor R46 is connected to the first output connection terminal of the optocoupler U1, and the other end is used for the input of a preset second working power supply Vp.

9. A heating drive circuit, characterized in that, Includes the failure detection circuit as described in any one of claims 1 to 8.

10. A heat gun, characterized in that, Includes the failure detection circuit as described in any one of claims 1 to 8.

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