A resistance wire temperature regulating circuit

Abstract

The utility model provides a resistance wire temperature regulation circuit, including: mains power supply, temperature regulation circuit and resistance wire, temperature regulation circuit includes rectifier circuit with mains power supply connection, rectifier circuit's output is connected with full -bridge inverter circuit, full -bridge inverter circuit is connected with voltage transformer barrier T1, voltage transformer barrier T1 is connected with the both ends of resistance wire, the signal output of main power control circuit is connected with full -bridge inverter circuit and voltage transformer barrier T1's signal input, main power control circuit includes triangle wave generator circuit, triangle wave generator circuit is connected with the reverse end of comparator, and the comparator passes through R25 and power tube Q5 and is connected with photocoupler circuit U3, and the output of photocoupler circuit U3 carries out signal output, and photocoupler circuit U3 can be parallelly connected multiple way synchronous control circuit, is used for the power regulation of circuit, the utility model discloses the setting of main power control circuit can realize one controller controls multiple main power supply simultaneously, and the power of regulation circuit is regulated to the load temperature.

Description

Technical Field

[0001] This utility model relates to the field of high-power resistive electrical appliance technology, specifically to a resistance wire temperature control circuit. Background Technology

[0002] In the thermoforming industry, resistance wire is a core component of heating equipment. Currently, most resistance wire heating systems on the market use 220V or 380V for power supply. This means the resistance value of the wire is determined based on the power required for the 220V or 380V power supply, and the current and power are calculated using Ohm's law.

[0003] In applications requiring very high temperatures, such as 900 or 1200 degrees Celsius, to increase the temperature while maintaining the same power, the only way is to continuously thin the resistance wire and reduce its diameter to achieve the required power, thereby increasing the temperature.

[0004] However, with thinner resistance wires and higher required temperatures, the wires are prone to burnout after several cycles of heating and cooling, and are not shock-resistant. This shortens the lifespan of the heating element, necessitates frequent replacements, and increases costs. Utility Model Content

[0005] To address the aforementioned technical problems, this technical solution provides a resistance wire temperature control circuit. Through the cooperation of a rectifier circuit, a full-bridge inverter circuit, and a transformer isolator T1, the mains power can be converted into a high-current, low-voltage state for the resistance wire. This allows the resistance wire to maintain its original or larger diameter while achieving the required temperature under the same power. By configuring the main power supply control circuit, its signal is connected to the full-bridge inverter circuit and the transformer isolator T1, enabling 0-100% duty cycle adjustment within a load frequency range of 20kHz to 150kHz to achieve power regulation and thus control the resistance wire temperature. This effectively solves the aforementioned problems.

[0006] This utility model is achieved through the following technical solution: A resistance wire temperature control circuit includes: a mains power supply, a resistance wire, and a temperature control circuit disposed between the two; the temperature control circuit includes a rectifier circuit connected to the mains power supply, the output terminal of the rectifier circuit being connected to a full-bridge inverter circuit, the full-bridge inverter circuit being connected to a transformer isolator T1, and the transformer isolator T1 being connected to both ends of the resistance wire; the signal input terminals of the full-bridge inverter circuit and the transformer isolator T1 are connected to the signal output terminal of a main power control circuit; the main power control circuit includes a triangular wave generator circuit, the triangular wave generator circuit being connected to the inverting terminal of a comparator, the comparator being connected to an optocoupler circuit U3 after passing through R25 and a power transistor Q5, and the output terminal of the optocoupler circuit U3 outputs a signal; the optocoupler circuit U3 can be connected in parallel with multiple synchronous control circuits for power regulation of the control circuit.

[0007] Furthermore, a second rectifier circuit is provided between the transformer isolator T1 and the resistance wire. The mains power supply uses 380V AC voltage, which is converted into 540V DC voltage by the first rectifier circuit. After passing through the full-bridge inverter circuit and transformer T1, it is converted into a low-voltage, high-frequency AC voltage output, and finally rectified into low-voltage DC by the second rectifier circuit and applied to the load resistance wire. The DC voltage applied to the load resistance wire is calculated according to Ohm's law. Given the resistance value of the resistance wire, the current flowing through the load is changed by adjusting the power of the mains power supply, reducing the impact caused by the conventional on / off switching mode.

[0008] Furthermore, the resistance wire used is a resistance wire with a diameter of 3mm or greater.

[0009] Furthermore, the primary and secondary isolation of the transformer isolator T1 is above 4000 volts, forming a safe isolation between the load terminal voltage and the mains power.

[0010] Furthermore, the full-bridge inverter circuit consists of four power transistors Q1, Q2, Q3, and Q4. These four power transistors are connected in series with drive transformers L2, L3, L4, and L5, respectively. The drive transformers L2, L3, L4, and L5 are controlled by the same transformer L6. Transformer L6 is the primary signal input terminal of the transformer, and the drive transformers L2, L3, L4, and L5 are the output terminals of the transformers.

[0011] Furthermore, the main power control circuit includes a transformer L6 connected to the full-bridge inverter circuit. L6 is the primary signal side for controlling and driving four groups of IGBTs. The primary input signal of the transformer is isolated by L6 to drive the IGBTs. The primary input signal of the transformer and the four groups of secondary IGBTs of the transformer L6 form a full-bridge circuit. The signal generation circuit is connected to the transformer L6 after passing through an overcurrent protection circuit and an adapter. The signal generation circuit generates a control signal to L6, which regulates the full-bridge inverter circuit to achieve power regulation of the full-bridge inverter circuit from 20-150KHZ.

[0012] Furthermore, the main power control circuit includes a transformer L6 connected to the full-bridge inverter circuit. L6 is the primary winding of the drive transformer, and the four secondary windings of the drive transformer control four IGBTs respectively. By regulating the full-bridge inverter circuit through the drive transformer L6, the duty cycle of the full-bridge inverter circuit can be adjusted from 0 to 100% at a frequency of 20-150kHz, thereby achieving continuous adjustment of the load power.

[0013] Furthermore, the triangular wave generator outputs a triangular wave with a base frequency of 1kHz to the comparator, with an amplitude of 5 to 10V. The inverting terminal of the comparator receives the triangular wave and compares it with the 4-11V voltage adjustment range of the forward potentiometer, outputting a square wave with an adjustable duty cycle of 0-100. The square wave output drives the power transistor Q5 through R25, which in turn drives the LED inside the optocoupler circuit U3. When the LED lights up, the output transistor is turned on, and the duration of the light emission corresponds to the duration of the conduction.

[0014] Furthermore, the output terminal of the optocoupler circuit U3 is connected to a voltage divider smoothing filter circuit, which outputs a 0-5V DC voltage to adjust the power of the main power supply; the main power supply is a 10KW power supply.

[0015] Furthermore, the voltage divider smoothing filter circuit includes a resistor R28 connected to the collector of the output transistor, and a resistor R19 and a capacitor C12 connected to the emitter of the output transistor.

[0016] Furthermore, the synchronization control circuit includes an optocoupler circuit U25 and a resistor R29 connected in parallel across the optocoupler circuit U3 and the resistor R18; if N main power supplies need to be controlled, N-1 synchronization control circuits are connected in parallel; the multi-channel synchronization control circuit is connected in parallel with the optocoupler circuit U3 and then connected in series with the voltage divider smoothing filter circuit. Beneficial effects

[0017] The resistance wire temperature control circuit proposed in this utility model has the following advantages compared with the prior art: This technical solution, through the cooperation of a rectifier circuit, a full-bridge inverter circuit, and a transformer isolator T1, can convert mains power into a state of high current and low voltage to be connected to the resistance wire. This allows the resistance wire to maintain its original or larger wire diameter under the same power and to reach the required temperature. By setting the main power supply control circuit, its signal is connected to the full-bridge inverter circuit and the transformer isolator T1, which can adjust the duty cycle from 0-100% under a load of 20kHz to 150kHz, thereby reducing the secondary output voltage of the transformer and thus achieving temperature control of the resistance wire.

[0018] This technical solution thickens the resistance wire to 3mm or 4mm in diameter. For the same wire length, this reduces the resistance wire's impedance, resulting in a lower voltage and higher current requirement for the same power output. The wire heats up quickly, heat is easily dissipated, and it is less prone to burnout. Using this wire diameter, the resistance wire cannot be directly supplied with 220V or 380V; it requires a rectifier circuit, a full-bridge inverter circuit, a transformer isolator T1, and a voltage divider smoothing filter circuit to reduce the input voltage. The main power supply control circuit and group control circuit are used to control the output current, maintaining a current density of 8-12A per square millimeter, thus achieving the required high temperature of 800-1200 degrees Celsius. Simultaneously, thickening the wire diameter also increases its durability, achieving high temperatures while extending its lifespan; it also allows for power adjustment to reach the desired surface temperature.

[0019] The main power supply control circuit of this technical solution outputs a 0-5V voltage. The control circuit of each power supply is controlled by the 0-5V. The 0-5V will change the duty cycle of the drive transformer L6. The duty cycles of L2, L3, L4, and L5 change synchronously, which will control the duty cycle of the four IGBTs. It will change the output voltage of the T1 transformer to adjust the load power, regulate the temperature, and provide overcurrent protection. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall circuit of this utility model.

[0021] Figure 2 This is a schematic diagram of the main power supply control circuit in this utility model. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. The described embodiments are only some embodiments of the present utility model, and not all embodiments. Various modifications and improvements to the technical solutions of the present utility model made by those skilled in the art without departing from the design concept of the present utility model should fall within the protection scope of the present utility model. Example

[0023] like Figure 1 As shown, a resistance wire temperature control circuit includes: a 380V AC power supply, a resistance wire, and a temperature control circuit disposed between the two. The resistance wire is a resistance wire with a diameter of 3 to 4 mm or more.

[0024] The temperature control circuit includes a rectifier circuit U1 connected to the mains power supply. The output of the rectifier circuit U1 is connected to a full-bridge inverter circuit. The full-bridge inverter circuit consists of four power transistors Q1, Q2, Q3, and Q4. The four power transistors Q1, Q2, Q3, and Q4 are connected in series with drive transformers L2, L3, L4, and L5, respectively. The drive transformers L2, L3, L4, and L5 are controlled by the same transformer L6 signal. The transformer L6 is the primary signal input terminal of the transformer, and the drive transformers L2, L3, L4, and L5 are the output terminals of the transformers.

[0025] The output of the full-bridge inverter circuit is connected to the input of the transformer isolator T1. The output of the transformer isolator T1 is connected to both ends of the resistance wire after passing through the rectifier circuits D1 and D2.

[0026] A 380V AC power supply is input into the rectifier circuit U1. After rectification by the rectifier bridge, a 540V DC output is generated. Then, it is inverted by a full-bridge circuit made of 4 IGBTs and transformer T1 to output a low-voltage, high-frequency AC voltage. Finally, it is rectified by D1 and D2 into a low-voltage DC voltage for the load.

[0027] In this circuit, transformer T1 acts as both a transformer to regulate the voltage and an isolator. The primary and secondary sides of T1 are isolated by more than 4000 volts, forming a safe isolation between the load voltage and the mains power.

[0028] The signal input terminals of the full-bridge inverter circuit and transformer isolator T1 are connected to the signal output terminal of the main power control circuit, and the signal input terminal of the main power control circuit is connected to the group control circuit.

[0029] The main power supply control circuit includes L6 connected to the full-bridge inverter circuit, and a protection circuit for circuit overcurrent sampling.

[0030] The signal generation circuit includes a triangular wave generator circuit, which is connected to the inverting terminal of a comparator. The comparator, after passing through resistor R25 and power transistor Q5, connects to optocoupler circuit U3. Optocoupler circuit U3 includes a light-emitting diode (LED), an output transistor, and resistor R18 connected to the LED. The output terminal of optocoupler circuit U3 is connected to a voltage divider smoothing filter circuit, which includes resistor R28 connected to the collector of the output transistor, resistor R19 connected to the emitter of the output transistor, and capacitor C12. The output terminal of the voltage divider smoothing filter circuit is connected to an adapter (outputting 0-5V).

[0031] After passing through the overcurrent protection circuit, the signal generation circuit is connected to the host drive transformer via an adapter. A 0-5V input is sent to the power control circuit, where the main power supply control signal performs a voltage-controlled duty cycle circuit to drive the primary winding of the drive transformer with an adjustable duty cycle. The primary winding (L6) and secondary windings (L2, L3, L4, L5) of the drive transformer are driven independently by four IGBTs (the power supply's base high frequency is 20-150kHz).

[0032] The triangular wave generator outputs a triangular wave with a base frequency of 1kHz to the comparator, with an amplitude of 5 to 10V. The inverting terminal of the comparator receives the triangular wave and compares it with the 4-11V voltage adjustment range of the forward potentiometer, outputting a square wave with an adjustable duty cycle of 0-100%. This square wave output drives the power transistor Q5 via R25, which in turn drives the LED inside the optocoupler circuit U3. When the LED illuminates, the output transistor conducts; the duration of illumination corresponds to the duration of conduction. The output of the optocoupler circuit U3 includes a voltage divider smoothing filter circuit, which outputs a 0-5V DC voltage to regulate the power of the main power supply.

[0033] The main power supply can be obtained by connecting multiple 10KW power supplies in parallel. The optocoupler circuit U3 can be connected in parallel with multiple synchronous control circuits to control the power regulation of multiple main power supplies.

[0034] The synchronization control circuit includes an optocoupler circuit U25 and a resistor R29 connected in parallel across optocoupler circuit U3 and resistor R18; to control N main power supplies, N-1 synchronization control circuits are connected in parallel, each synchronization control circuit having an interface connected to a main power supply, resulting in the following... Figure 2 The main power supply control circuit shown.

[0035] The main power supply is connected to the synchronous control circuit via an interface. The synchronous control circuit is connected in parallel to the optocoupler circuit U3 and resistor R18. The multi-channel synchronous control circuit is connected in parallel with the optocoupler circuit U3 and then in series with the voltage divider smoothing filter circuit for output. This is used to regulate the power of the circuit, thereby adjusting the voltage and current entering the load.

[0036] The main power supply operates as follows: 380V AC voltage is rectified by the rectifier module to obtain 540VDC. This 540VDC is then inverted at a high frequency of 20kHz-150kHz by four IGBTs, outputting a 540V high-frequency AC square wave. After being isolated and stepped down by transformer T1, it is rectified and connected to the load. The 20-150kHz circuit is adjusted by changing the conduction time and 0-100% duty cycle of the four IGBTs, thereby altering the effective voltage output by transformer T1. According to Ohm's law, changing the voltage while keeping the resistance constant allows for adjustments to the main power supply's power, which in turn changes the load current, thus achieving the desired temperature.

[0037] The purpose of the main power supply control circuit is: 1. To regulate the control circuit of each power supply from 0-5V, change the duty cycle of the main circuit, and achieve power regulation. 2. To achieve independent isolation of more than 4000V between multiple power supplies by means of optocoupler isolation, ensuring they do not share a common ground or positive voltage. 3. To achieve synchronous control of N power supplies using a single adjustment potentiometer.

[0038] Since each power supply control port only accepts 0-5V regulation, the 1kHz duty cycle adjustable signal output from the optocoupler needs to be divided by resistors after the optocoupler to limit the voltage to a maximum of 5V. The square wave voltage is smoothed into a continuously varying 0-5V voltage by adding an electrolytic capacitor, making the regulation process smooth and continuous.

Claims

1. A resistance wire temperature control circuit, comprising: The system comprises a mains power supply, a resistance wire, and a temperature regulating circuit positioned between them. The temperature regulating circuit includes a rectifier circuit connected to the mains power supply. The output of the rectifier circuit is connected to a full-bridge inverter circuit, which is connected to a transformer isolator T1. The transformer isolator T1 is connected to both ends of the resistance wire. The signal input terminals of the full-bridge inverter circuit and the transformer isolator T1 are connected to the signal output terminal of the main power control circuit. The main power control circuit includes a triangular wave generator circuit, which is connected to the inverting terminal of a comparator. The comparator, after passing through resistor R25 and power transistor Q5, is connected to an optocoupler circuit U3. The output terminal of the optocoupler circuit U3 outputs a signal. The optocoupler circuit U3 can be connected in parallel with multiple synchronous control circuits for power regulation of the control circuit.

2. The resistance wire temperature control circuit according to claim 1, characterized in that: A second rectifier circuit is provided between the transformer isolator T1 and the resistance wire; the mains power supply adopts AC 380V voltage, which is converted into 540V DC voltage by the first rectifier circuit; after passing through the full-bridge inverter circuit and transformer T1, it is converted into low-voltage high-frequency AC voltage output, and finally rectified into low-voltage DC by the second rectifier circuit and applied to the load resistance wire.

3. The resistance wire temperature control circuit according to claim 1, characterized in that: The resistance wire used is a resistance wire with a diameter of 3mm or greater.

4. The resistance wire temperature control circuit according to claim 1, characterized in that: The primary and secondary isolation of the transformer T1 is above 4000 volts, forming a safe isolation between the load voltage and the mains power.

5. The resistance wire temperature control circuit according to claim 1, characterized in that: The full-bridge inverter circuit consists of four power transistors Q1, Q2, Q3, and Q4. These four power transistors are connected in series with drive transformers L2, L3, L4, and L5, respectively. The drive transformers L2, L3, L4, and L5 are controlled by the same transformer L6. Transformer L6 is the primary signal input terminal of the transformer, and the drive transformers L2, L3, L4, and L5 are the output terminals of the transformers.

6. The resistance wire temperature control circuit according to claim 1, characterized in that: The main power control circuit includes a transformer L6 connected to the full-bridge inverter circuit. L6 is the primary signal side for controlling and driving four groups of IGBTs. The primary input signal of the transformer is isolated by L6 to drive the IGBTs. The primary input signal of the transformer and the four groups of secondary IGBTs of the transformer L6 form a full-bridge circuit. The signal generation circuit is connected to the transformer L6 after passing through an overcurrent protection circuit and an adapter. The signal generation circuit generates a control signal to L6, which regulates the full-bridge inverter circuit to achieve power regulation of the full-bridge inverter circuit from 20-150KHZ.

7. The resistance wire temperature control circuit according to claim 1, characterized in that: The triangular wave generator outputs a triangular wave with a base frequency of 1kHz to the comparator, with an amplitude of 5 to 10V. The inverting terminal of the comparator receives the triangular wave and compares it with the 4-11V voltage adjustment range of the forward potentiometer, outputting a square wave with an adjustable duty cycle of 0-100. The square wave output drives the power transistor Q5 through R25, which in turn drives the LED inside the optocoupler circuit U3. When the LED lights up, the output transistor is turned on, and the duration of the light emission corresponds to the duration of the conduction.

8. The resistance wire temperature control circuit according to claim 1, characterized in that: The output of the optocoupler circuit U3 is connected to a voltage divider smoothing filter circuit, which outputs a 0-5V DC voltage to adjust the power of the main power supply; the main power supply is a 10KW power supply.

9. The resistance wire temperature control circuit according to claim 8, characterized in that: The voltage divider smoothing filter circuit includes a resistor R28 connected to the collector of the output transistor, and a resistor R19 and a capacitor C12 connected to the emitter of the output transistor.

10. The resistance wire temperature control circuit according to claim 8, characterized in that: The synchronization control circuit includes an optocoupler circuit U25 and a resistor R29 connected in parallel across the optocoupler circuit U3 and the resistor R18; if N main power supplies need to be controlled, N-1 synchronization control circuits are connected in parallel; the multi-channel synchronization control circuit is connected in parallel with the optocoupler circuit U3 and then connected in series with the voltage divider smoothing filter circuit.

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