WO2017020564A1 - Dc heating circuit and electric soldering iron formed by same - Google Patents

Abstract

A DC heating circuit comprises a triode, a diode, an inductor, a first capacitor, a second capacitor, and a heating wire. A source of the triode is grounded. A drain of the triode is connected to a positive electrode of the diode and one end of the inductor separately. A negative electrode of the diode is connected to a DC voltage. The negative electrode of the diode is further connected to the first capacitor, the second capacitor, and the heating wire that are connected in parallel. The other end of the first capacitor, the other end of the second capacitor, and the other end of the heating wire are connected to the other end of the inductor. A soldering iron head (1) of an electric soldering iron having the DC heating circuit is provided with a cavity, a ceramic tube (4) is disposed in the cavity, a heating element (2) is disposed on an outer wall of the ceramic tube, and a thermocouple (3) is disposed inside the ceramic tube. The DC heating circuit achieves DC heating of a heating component of the electric soldering iron. A thermocouple sensor has a high data acquisition speed, and temperature deviation caused by interference is avoided. During soldering of the soldering iron, the temperature fluctuation of the soldering iron head is low, thereby improving the soldering speed and the soldering quality.

Description

 DC heating circuit and electric iron thereof  DC heating circuit and electric iron thereof

 Technical field

 The invention relates to the field of welding tools, in particular to a direct current heating circuit and an electric soldering iron thereof.

 Background technique

 The technology of constant temperature soldering iron heating has undergone several changes: The earliest constant temperature soldering irons are made of ceramic heating cores, the soldering iron head becomes a replaceable part, the coil and the thermocouple are separated, and the comparator is used to adjust and thermostat; Started by a Japanese brand to use a heating wire and thermocouple directly into the tip of the soldering iron through the thermal conductive material, and then use the MCU To control the stability of the temperature, and to use the principle that the thermocouple can be connected in series with the third metal, the tip is simplified to a two-wire connection.

 Above 2 The technical method adopts the on-off heating method when heating. In this way, the temperature fluctuation is relatively large when heated, especially when welding, but in the era of manual welding, due to the welding speed The reason is that the fluctuation of the temperature is acceptable within a certain range, because during the process of manual welding, when the welding personnel observe that the welding condition is not good, measures such as prolonging the heating time are taken to ensure the welding quality, so this In the past, heating methods have always been able to meet the needs of use.

With the advancement of technology and the need for automated production of products, many people's welded products have begun to be converted into automatic welding robots. As the welding speed increases, the temperature stability requirements of the soldering irons begin to increase, and the robots are welded. The soldering time of the solder joints is fixed. Therefore, when the temperature of the soldering iron fluctuates, some solder joints will be soldered at the time of soldering due to insufficient soldering iron temperature. Therefore, the temperature stability requirements of the soldering iron are beginning to increase. However, the improvement of the original soldering iron control technology has been very small, and the market has urgently needed a heating technology that can greatly improve the performance of the soldering iron.

 Summary of the invention

 The invention provides a DC heating circuit and an electric soldering iron thereof, which solves the problem of insufficient temperature stability of the soldering iron in the prior art.

The technical solution of the present invention is implemented as follows: a DC heating circuit comprising a triode, a diode, an inductor, a first capacitor, a second capacitor, and a heating wire; a source of the triode is grounded, and a drain of the triode is respectively connected to the anode of the diode and One end of the inductor, the negative pole of the diode is connected to the DC voltage, the cathode of the diode is also connected with the first capacitor, the second capacitor and the heating wire connected in parallel, and the other end of the first capacitor, the second capacitor and the heating wire are connected to the other end of the inductor.

 Further, the gate of the triode is connected to a pulse width modulated signal. Further, the triode is an N-channel FET.

The invention also provides a DC heating electric soldering iron, which is composed according to the above-mentioned DC heating circuit, comprising a soldering iron head and a heating element, further comprising a ceramic tube and a thermocouple; the soldering iron head is provided with a cavity, and the ceramic tube is arranged in the air In the cavity, the heating element is disposed on the outer wall of the ceramic tube, and the thermocouple is disposed inside the ceramic tube.

 Further, the heating element is a heating wire. Further, the heating wire is wound around the outer wall of the ceramic tube.

 Further, the ceramic tube has a hollow cylindrical shape.

 Further, the soldering iron tip is filled with a highly thermally conductive insulating material.

 Further, the thermocouple is connected to a thermocouple sensor for collecting temperature data.

 The beneficial effects of the invention are:

 1 Innovation of heating principle: For the first time, pure DC heating is applied to the field of electric soldering iron. For the first time, DC heating is used in the field of electric soldering iron heating;

 2, heating circuit innovation: DC-DC for the first time The voltage conversion technology is applied to the control of the electric iron heating wire, making the application of DC heating a complete and feasible technology.

 3, the scalability of the soldering iron power: as the heating power of the soldering iron is further increased from the current mainstream 90 watts of power to 200 Tile or greater power, if using existing soldering irons, the temperature fluctuations during soldering will become more difficult to control, if using heating and thermocouple separate and using PWM When AC power is used to control the power of the heating wire, the interference signal of the thermocouple is further enhanced, making the processing of the interference signal more and more difficult. If DC heating is used, there is no need to worry about the signal interference of the thermocouple, and the heating power can be easily increased. To be bigger, only need to Simple adaptation of components such as MOS transistors and rectifier diodes can solve the problem of high power buck, and can have better temperature stability and very small temperature fluctuation range (if the power is increased, if PWM is used) By means of the heating method, the temperature rises rapidly when the heating wire is energized, and rapidly decreases when the power is turned off, so that the temperature fluctuation range is increased and the temperature fluctuation becomes more difficult to control).

 4. The invention can be easily extended to other fields requiring low voltage, high precision constant temperature and low interference signals.

 5 Further research on this technology can further reduce costs, enabling the technology to upgrade the soldering iron industry with higher temperature control accuracy, and greatly improve the performance of the soldering iron.

 6. MCU without interference signal The thermocouple can be measured at a high speed, so the temperature change curve can be generated, and the soldering iron can be more intelligent. Through the analysis of the temperature change curve, the temperature control strategy of the soldering iron can be automatically learned, and is more suitable for the user's usage habits. The tuning of the software makes the temperature control more intelligent, and can realize intelligent sleep power saving and other functions without using any external sensors.

 DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any inventive labor.

 1 is a circuit diagram of a DC heating circuit of the present invention;

 2 is a schematic structural view of a direct current heating electric iron according to the present invention;

 Figure 3 shows the MCU control flow chart.

 In the figure: 1- soldering iron tip; 2- heat generating unit; 3- electric thermocouple; 4-ceramic tube.

 detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

 Figure 1 As shown, the present invention provides a DC heating circuit comprising a triode, a diode, an inductor, a first capacitor, a second capacitor, and a heating wire; the source of the triode is grounded, and the drain of the triode is connected to the anode of the diode and one end of the inductor, respectively. The negative pole of the diode is connected to the DC voltage, and the cathode of the diode is further connected to the first capacitor, the second capacitor and the heating wire connected in parallel, and the other end of the first capacitor, the second capacitor and the heating wire are connected to the other end of the inductor. The gate of the transistor is connected to a pulse width modulated signal. Transistor N-channel FET. This circuit uses a topology of DC-DC buck (N-channel MOS transistor low-side buck). After applying this circuit, the N-channel MOS transistor is The MCU shares GND as a reference, so the MCU can easily drive the MOS transistor in the range of 5-20V, and the switching speed of the MOS can easily reach hundreds after using the push-pull structure. KHZ, the overall efficiency of the circuit has been greatly improved, and the circuit design is simplified, and the heating voltage at both ends of the RS1 heating wire is pure DC, by changing the PWM The duty ratio of the frequency can adjust the heating power of the heating wire very linearly. During the adjustment process, the heating wire only produces the change of the total power, and does not generate the voltage transformation in the current direction. The heating wire does not generate electromagnetic interference at all, and Linear adjustment characteristics of direct current The power of the heating wire can be very constant, so that the accuracy of the constant temperature can be very high, and the variation is very linear without large fluctuations.

The invention also provides a DC heating electric soldering iron, which is composed according to a DC heating circuit, comprising a soldering iron head and a heating element, further comprising a ceramic tube and a thermocouple; the soldering iron head is provided with a cavity, and the ceramic tube is arranged in the cavity The heating element is disposed on the outer wall of the ceramic tube, and the thermocouple is disposed inside the ceramic tube. The heating element is a heating wire. The heating wire is wound around the outer wall of the ceramic tube. The ceramic tube has a hollow cylindrical shape. The tip of the tip is filled with a highly thermally conductive insulating material. The thermocouple is connected to a thermocouple sensor for collecting temperature data. The DC heating of the heating element of the soldering iron is realized by the improvement of the DC heating circuit. At this time, the data acquisition speed of the thermocouple sensor can easily reach the sampling rate of thousands of times per second, and there is no interference to cause temperature deviation. After the soldering iron is soldered MCU It can quickly read the temperature change of the soldering iron tip and linearly increase the power of the heating wire. The adjustment speed is thousands of times per second, so the soldering iron tip always maintains very low temperature fluctuation regardless of the welding speed, which makes the automatic welding. The welding quality of the robot has been greatly improved while the welding speed has been greatly improved.

 The flow of the MCU control method is shown in Figure 3. As shown, this control method reads the temperature data while heating, and keeps the heating part at the set temperature at the constant temperature setting. In this control mode, the external temperature changes. Faster speed by MCU Read out, and the power is compensated when the external temperature changes, so the external temperature will drop slightly after the temperature drops, and the temperature will gradually return as the temperature is further compensated during the continuous rapid welding. Set the temperature and maintain a constant temperature while maintaining the welding rate. This characteristic is very suitable when applied to the automatic welding robot because the automatic welding robot has a constant welding rate and can The temperature is stable at the time of welding, and the robot can continue to weld at a faster speed and ensure the quality of the solder joint.

 In summary, the present invention has the following advantages:

 1 Innovation of heating principle: For the first time, pure DC heating is applied to the field of electric soldering iron. For the first time, DC heating is used in the field of electric soldering iron heating;

 2, heating circuit innovation: DC-DC for the first time The voltage conversion technology is applied to the control of the electric iron heating wire, making the application of DC heating a complete and feasible technology.

 3, the scalability of the soldering iron power: as the heating power of the soldering iron is further increased from the current mainstream 90 watts of power to 200 Tile or greater power, if using existing soldering irons, the temperature fluctuations during soldering will become more difficult to control, if using heating and thermocouple separate and using PWM When AC power is used to control the power of the heating wire, the interference signal of the thermocouple is further enhanced, making the processing of the interference signal more and more difficult. If DC heating is used, there is no need to worry about the signal interference of the thermocouple, and the heating power can be easily increased. To be bigger, only need to Simple adaptation of components such as MOS transistors and rectifier diodes can solve the problem of high power buck, and can have better temperature stability and very small temperature fluctuation range (if the power is increased, if PWM is used) By means of the heating method, the temperature rises rapidly when the heating wire is energized, and rapidly decreases when the power is turned off, so that the temperature fluctuation range is increased and the temperature fluctuation becomes more difficult to control).

 4. The invention can be easily extended to other fields requiring low voltage, high precision constant temperature and low interference signals.

 5 Further research on this technology can further reduce costs, enabling the technology to upgrade the soldering iron industry with higher temperature control accuracy, and greatly improve the performance of the soldering iron.

 6. MCU without interference signal The thermocouple can be measured at a high speed, so the temperature change curve can be generated, and the soldering iron can be more intelligent. Through the analysis of the temperature change curve, the temperature control strategy of the soldering iron can be automatically learned, and is more suitable for the user's usage habits. The tuning of the software makes the temperature control more intelligent, and can realize intelligent sleep power saving and other functions without using any external sensors.

The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalents, improvements, etc., which are within the spirit and scope of the present invention, should be included in the scope of the present invention. within.

Claims (9)

A DC heating circuit, comprising: a triode, a diode, an inductor, a first capacitor, a second capacitor, and a heating wire; a source of the triode is grounded, and a drain of the triode is respectively connected to a positive pole of the diode and One end of the inductor, a cathode of the diode is connected to a DC voltage, and a cathode of the diode is further connected to a first capacitor, a second capacitor and a heating wire connected in parallel, and the other end of the first capacitor, the second capacitor and the heating wire Connect the other end of the inductor. A direct current heating circuit according to claim 1, wherein the gate of said transistor is connected to a pulse width modulation signal. A direct current heating circuit according to claim 2, wherein said triode is an N-channel field effect transistor. A DC heating electric soldering iron comprising a soldering iron tip and a heating element, and a direct current heating circuit according to any one of claims 1 to 3, further comprising: a ceramic tube and a thermocouple; There is a cavity, the ceramic tube is disposed in the cavity, the heat generating component is disposed on an outer wall of the ceramic tube, and the thermocouple is disposed inside the ceramic tube. A direct current heating electric iron according to claim 4, wherein said heat generating component is a heating wire. A direct current heating electric iron according to claim 5, wherein said heating wire is wound around an outer wall of said ceramic tube. A direct current heating electric iron according to claim 4, wherein the ceramic tube has a hollow cylindrical shape. A direct current heating soldering iron according to claim 4, wherein the soldering iron tip is filled with a highly thermally conductive insulating material. A direct current heating electric soldering iron according to claim 4, wherein said thermocouple is connected to a thermocouple sensor for collecting temperature data.