阅读说明：本技术 一种向空气释放物质的感应加热器 (Induction heater for releasing substance to air ) 是由 田镇源 叶静 于 2021-09-01 设计创作，主要内容包括：一种向空气释放物质的感应加热器,属于生活用品领域。其发热体有金属定位托盘、金属复合纸质吸附片、混合金属粉末纸质吸附片、粉末冶金铁基吸附片。发热体置于高频交变磁场中,感生涡流而发热。适用于驱蚊、薰香、蒸醋等。通过间断发送脉冲驱动讯号至逆变电路开关器件控制极来使感应加热器间歇工作,调整PWM信号的脉冲占空比来控制发热功率。优点有：节能,可以使用USB端口低压供电,便携,节省耗材,发热散热快,发热可控,容易得到间歇和阵发的向空气散发物质的效果。(An induction heater for releasing substances to air belongs to the field of articles for daily use. The heating body comprises a metal positioning tray, a metal composite paper adsorption sheet, a mixed metal powder paper adsorption sheet and a powder metallurgy iron-based adsorption sheet. The heating element is arranged in a high-frequency alternating magnetic field, and induces eddy current to generate heat. It is suitable for repelling mosquito, fumigating incense, steaming vinegar, etc. The induction heater is enabled to work intermittently by sending pulse driving signals to the control electrode of the inverter circuit switching device intermittently, and the pulse duty ratio of the PWM signals is adjusted to control the heating power. Has the advantages that: the energy-saving USB port low-voltage power supply device is energy-saving, portable, capable of saving consumables, fast in heating and heat dissipation, controllable in heating and capable of easily obtaining the effect of intermittent and burst emission of substances to air.)

1. The utility model provides an induction heater to air release material, includes casing, power supply circuit unit, inverter circuit unit, control drive protection circuit unit, gives and shows circuit unit, resonant capacitor, resonance coil, heat-generating body, its characterized in that: the resonance coil is parallel to the bottom plane of the heating body and is provided with a positioning device.

2. An induction heater for delivering a substance to the air as claimed in claim 1, wherein: the positioning device comprises a positioning structure and a positioning tray on the shell, and the positioning structure limits the movement of the positioning tray.

3. An induction heater for delivering a substance to the air as claimed in claim 2, wherein: the positioning tray is made of metal or high-temperature-resistant plastic, and the positioning tray made of metal is a heating body.

4. An induction heater for delivering a substance to the air as claimed in claim 3, wherein: the outer surface of the positioning tray made of metal is coated with a high-temperature-resistant non-metallic material.

5. An induction heater for delivering a substance to the air as claimed in claim 1, wherein: the resonance coil is twisted by a plurality of strands of enameled wires and then wound into a flat hollow disc shape.

6. An induction heater for delivering a substance to the air as claimed in claim 1, wherein: the resonance coil disc provided with the resonance coil is fixed on the shell through a buckle.

7. An induction heater for delivering a substance to the air as claimed in claim 1, wherein: the heating power is controlled by changing the pulse duty ratio of the PWM signal.

8. An induction heater for delivering a substance to the air as claimed in claim 1, wherein: the induction heater is operated intermittently by intermittently outputting a pulse signal to the inverter circuit.

9. A metal composite paper sorbent sheet for use in an induction heater for the delivery of a substance to air as recited in claim 1, wherein: a sheet of fibrous paper is laminated with a thin layer of metal.

10. A mixed metal powder paper sorbent sheet for use in an induction heater for the delivery of a substance to air in accordance with claim 1, wherein: the main component is plant fiber, and mixed with metal powder.

11. A powder metallurgy iron-based adsorption sheet for use in an induction heater for discharging a substance into the air according to claim 1, wherein: is prepared by a powder metallurgy process.

Technical Field

The invention belongs to the field of articles for daily use, and particularly relates to an induction heater capable of releasing substances to air.

Background

The substance "releasing substance to the air" in the invention refers to mosquito repellent, freshener, vinegar, perfume, etc., and can also be a combination or mixture of these substances, and these substances can be solid, liquid, gel, and when heated, will volatilize, sublimate and diffuse to the air, and obtain the desired effect. At present, electric heaters are widely used for heating such substances. Used for mosquito repellent, so called as electric mosquito repellent heater; for others, it is commonly referred to as an electrothermal aromatherapy device.

The two electric heaters use electric heating wires or PTC to generate heat, and the generated heat is firstly transmitted to the metal heat conducting plate and then transmitted to the mosquito repellent, the freshener and the like. Therefore, the system has the problems of low efficiency, large power consumption and generally only being capable of supplying power by 220V mains supply. Therefore, chinese patent CN208692153U proposes "a heater using high frequency electromagnetic heating mosquito-repellent incense liquid" to solve these disadvantages.

Another disadvantage of both types of electric heaters is that the output power is fixed and thus the concentration of the released substance cannot be controlled. When the output power is lower, the gas concentration can not meet the requirement; when the output power is higher, the gas concentration can be uncomfortable, the consumption of consumables such as incense, fresheners, mosquito repellent liquid and the like is increased, and the use time is shortened. Chinese patent CN102595663A discloses an electric heater with adjustable power for heating volatile substances, in order to adjust the volatile concentration appropriately.

The third disadvantage is that the heating device is continuously heated, and once the heating device is started, the heating device cannot be stopped, and the medicament is continuously volatilized until the medicament is exhausted or the power supply is turned off. As a result, the amount of the chemical discharged is excessive, and the power consumption is increased. Therefore, as early as 2014, 8 and 10, a character of 'power saving practice for using electric mosquito repellent incense' is published in 'electronic newspaper' at the 32 nd stage, and a circuit of a gap switch mosquito repellent incense heater is provided. And the starting time and the intermittent stopping time are determined according to the mosquito habit and the experimental result, so that the aim of saving is fulfilled.

It is further noted that continuous heating releases the agent and the effect is rather unsatisfactory. People have the experience that people can obviously smell the released fragrance when entering a closed space with the aromatherapy device, but the fragrance still exists but can not feel the strong smell for a long time, which is the 'olfactory fatigue'. People hope to smell the fragrance like the natural state, the fragrance is paroxysmal and discontinuous, and the fragrance habit is unsophisticated. The mosquitoes have similar characteristics, and after 1-3 minutes, the mosquitoes feel dull or adapt to the mosquito repellent. This is one reason why the effect of repelling mosquitoes is often not good. On the other hand, the continuous release of the mosquito repellent is also not good for health. Therefore, Chinese patent CN104115817A discloses a portable mosquito/incense device, which uses a pulse power supply to solve the problem.

The above disadvantages can be solved by using electromagnetic induction heating technology.

The induction heating is a novel heating mode relative to the current heat effect heating and flame heating of the traditional resistor, and is an advanced heating technology with high efficiency, energy saving, material saving, environmental protection and safety.

Induction heating is to place a heated material in a high-frequency alternating magnetic field (e.g., a toroidal coil through which an alternating current is passed), magnetic lines of force constituting the magnetic field cut the heated material in the magnetic field, eddy currents are generated in a cross section perpendicular to the magnetic lines of force according to the faraday's law of electromagnetic induction, and the induced eddy currents generate heat energy on the alternating current impedance presented by a conductive material according to the joule's law of thermal effect to heat a workpiece. The heating method by using the electromagnetic induction principle to generate the high-frequency induction eddy current heat effect is referred to as induction heating for short.

The heated materials such as the mosquito repellent, the freshener and the like have extremely poor conductivity and can not generate heat when being placed in a high-frequency alternating magnetic field. It is necessary to use a conductor as a heating element for indirectly heating the non-conductive body by utilizing the heat generated in the high-frequency alternating magnetic field.

Disclosure of Invention

The invention aims to solve the defects of low efficiency, high power consumption, multiple medicament consumption, and no heavy use effect of the existing electric heating incense device and electric heating mosquito incense heater. The main reason for these disadvantages is that the heating is continued by using the heating wire or PTC and the power cannot be adjusted.

The present invention addresses the above problems, and employs a technique of electromagnetic induction heating. The power supply mainly comprises a power supply circuit (a high-voltage power supply and an auxiliary power supply), an inverter circuit, a resonance circuit, a control drive protection circuit, a setting and display circuit and a heating body.

The power supply is usually supplied by 220V AC power grid, and can also be supplied by inputting DC low voltage by using a USB interface.

When 220V alternating current is used, the circuit is divided into two paths. One path of direct current high voltage after rectification and filtration is sent to an inverter circuit; and the other path of the voltage is subjected to voltage reduction, rectification and filtering and then is used as an auxiliary power supply to control, drive and protect circuits and the like.

The direct current low voltage power supply is also divided into two paths. One path of direct current high voltage obtained after boosting, rectifying and filtering is sent to an inverter circuit; the other path is used as an auxiliary power supply.

The inverter circuit converts a direct current voltage into a high frequency alternating current voltage (or current) to complete DC/AC conversion. The DC/AC conversion circuit adopts a single tube, half-bridge or full-bridge structure. The switch device adopts MOSFET and IGBT, and when the heating power of the heater is small, the power triode can be used. The control electrode of the switch device is input with a driving signal to realize conduction control, and the inverter circuit can output high-frequency square waves.

The resonant circuit is an important constituent functional unit of the induction heating power supply and is also a load of the inverter. There are various types, mainly a series resonance type, a parallel resonance type, and a series-parallel resonance type. The output of the voltage-type inverter or the current-type inverter is a resonant circuit formed by an inductor and a capacitor. In the present invention, the inductor is a flat hollow disk-shaped coil, and the heating element is a metal conductor having a flat shape as a whole, and both are arranged in parallel. And a positioning device is arranged to fix the relative position of the two. High frequency alternating current from an inverter is applied to the inductor, thereby generating a high frequency alternating magnetic field. The magnetic force lines act on the metal heating body, eddy current is generated in the metal heating body due to electromagnetic induction, when the eddy current overcomes the internal resistance of the metal heating body and flows, the conversion of electric energy to heat energy is completed, and the generated Joule heat is the heat source of the heater.

The control drive protection circuit comprises a drive inverter switching device circuit and a control system.

The driving method can be generally divided into: direct drive, optical coupling isolation drive, pulse transformer isolation drive and application specific integrated circuit drive.

On one hand, the control system should ensure the normal operation of the main circuit and also should perform various protection and monitoring functions. Can be controlled by a single chip microcomputer.

The power control and regulation adopts a control circuit for regulating power at the inverter side. Commonly used are frequency modulation power modulation (PFM), phase shift power modulation (PSM), pulse width modulation constant frequency power modulation (PWM), width modulation plus frequency modulation power modulation (PWM + PFM), etc.

The present invention uses a Pulse Width Modulation (PWM) technique to control the output power by modulating the pulse width. An important concept in pulse width modulation is the duty cycle of the pulses, which is used to represent the ratio of the on-time to the total period. Within a certain range, the larger the duty ratio is, the larger the output power is, and conversely, the smaller the output power is.

The pulse duty ratio can be controlled by a single chip microcomputer.

In order to stably and reliably output power, a feedback method is also used. The voltage and current signals are sampled from the voltage and current detection circuit, and are converted into digital signals of the single chip microcomputer through A/D conversion and multiplied to obtain the power, so that the single chip microcomputer can make judgment in time, the PWM value is increased or decreased, and the purpose of accurately controlling the consumed power is achieved.

After the technical measures are adopted:

the efficiency is improved, the power consumption is reduced, and the low-voltage power supply of the USB interface can be used;

the consumption of the medicament is reduced;

the power may be output discontinuously. In other words, intermittent output pulse signals are adopted to the control electrode of the switching device of the inverter circuit, and the purpose of gap heating is achieved. Moreover, the magnetic force lines directly act on the metal load to generate heat, the heat capacity is small, the heat rising is rapid, the heat dissipation is also rapid, and the effect of releasing substances into the air by gaps and bursts is easier to obtain;

the output power is adjusted by easily changing the size of the duty ratio by using a pulse width modulation technology;

the magnetic lines of force can penetrate through a non-metal object (such as a plastic shell of an induction heater) to act on a metal load for heating, and the magnetic induction heater can be suitable for releasing substances to air after being heated in various physical states, as long as the substances contain a certain amount of metal or are placed in a metal tray.

Drawings

FIG. 1 a schematic cross-sectional view of an induction heater of the present invention

FIG. 2 is a schematic top view of the induction heater of the present invention (with the housing removed)

FIG. 3 is a schematic top view of an induction heater of another positioning device of the present invention (with the housing removed)

FIG. 4 is a schematic sectional view A-A of FIG. 3

FIG. 5 is a schematic top view of a resonant coil panel

FIG. 6 cross-sectional view of the positioning tray

FIG. 7 is a schematic top view of the positioning tray

FIG. 8 schematic cross-sectional view of a metal composite paper adsorption sheet

FIG. 9 is a schematic top view of a metal composite paper absorbent sheet

FIG. 10 is a partial enlarged view of FIG. 8

FIG. 11 is a schematic cross-sectional view of another metal composite paper adsorption sheet

FIG. 12 is a schematic sectional view of a powder metallurgy iron-based adsorption sheet

FIG. 13 is a block diagram of an induction heating circuit of the present invention

FIG. 14 schematic diagram of the main circuit of the induction heating of the present invention

Detailed Description

The invention will be further explained with reference to the drawings.

As shown in fig. 1, 2 and 13:

the housing 1 comprises a lower housing 11, an upper housing 12 and a cover 13, and is made of plastic. The upper housing 12 is provided with a plurality of heat dissipation holes 121, and the lower housing 11 is also provided with a plurality of heat dissipation holes. A power circuit unit 2, a control drive protection circuit unit 3, an inverter circuit unit 4, a resonant capacitor 5, a resonant coil panel 6 and a given and display circuit unit 8 are arranged between the upper and lower shells. The positioning tray 7 is located on the upper case 12.

The cover 13 is arranged to prevent the human body from contacting the heating part and being injured, and is provided with air-diffusing holes.

The power supply circuit unit 2 includes a high-voltage power supply circuit and an auxiliary power supply circuit.

The power supply is a low-voltage direct-current power supply connected with a USB interface. The power supply is basically similar if 220V AC network input is adopted. The foregoing summary has been provided.

The lower case 11 is provided with a USB interface 21. Through which the low-voltage direct current is input to the power supply circuit unit 2. The DC high voltage is obtained after one path is subjected to boosting, rectifying and filtering, and then the DC high voltage is sent to an inverter circuit unit 4; the other path is an auxiliary power supply which supplies power for a sampling and control drive protection circuit and the like.

The inverter circuit unit 4 is controlled and driven by the control drive protection circuit unit 3. The control drive protection unit 3 sends a pulse signal to the control electrode of the switching device of the inverter circuit unit 4 according to the setting of the setting and display circuit unit 8, controls the conduction of the pulse signal, and the inverter circuit unit 4 changes the direct current high voltage into high frequency alternating current high voltage and outputs the high frequency alternating current high voltage to the resonance circuit.

The resonant circuit is mainly composed of a resonant capacitor 5 and a resonant coil on a resonant coil panel 6. The circuit is a circuit with complex working state and influencing factors in the induction heating power supply.

As shown in fig. 1 and 5, the resonant coil disk 6 is composed of a resonant coil 61 and a support 62. The resonant coil 61 is formed by twisting a plurality of strands of enameled wires into a beam and then winding the beam, so that the skin effect is reduced, and the self-loss of the coil is reduced. The heating element can be wound into a flat hollow disc shape, a round shape, or a square or rectangular shape according to the shape of the heating element. The size of the heater corresponds to the heating area of the heating body. The winding method is as shown in fig. 5, after a plurality of circles of tightly winding, a position with two circles is left, then the tightly winding is carried out, and a position with two circles is left, then the tightly winding is carried out. To leave a void for the updraft to pass through for heat dissipation. Or can be continuously close-wound.

The resonant coil 61 is fixed to the support 62 by an epoxy heat-resistant adhesive.

The bracket 62 is made of an epoxy glass cloth laminate. A round hole is arranged in the middle, and a plurality of heat dissipation holes are arranged around the round hole. In operation, the airflow cools the resonance coil 61 and the like from bottom to top through the heat radiation holes of the bracket 62 and the heat radiation holes 121 of the upper case 12.

The holder 62 may also be made of a polyester resin by pressing, and may contain ferrite powder therein.

As shown in fig. 1, the resonant coil disk 6 is fixed to the upper case 12 not by metal screws but by a snap mechanism.

The upper housing 12 is provided with 3 to 4 snaps 122. The end of the buckle 122 is designed into a slope, and a groove is arranged above the slope and used as a clamping groove. The bracket 62 shown in fig. 5 also has 3 to 4 positioning notches 621 formed on the periphery thereof, and the width and depth thereof are matched with the snap 122. During assembly, as long as the notch 621 is aligned with the clip 122, the resonant coil disk 6 is pushed in, the clip 122 retreats due to the force of the end slope until the resonant coil disk 6 falls into the upper slot of the clip 122 and then resets, the notch 621 on the resonant coil disk 6 is embedded into the upper slot of the clip 122, and the resonant coil disk 6 is fixed on the upper housing 12.

The resonant coil 61 is where the induction heating unit outputs only power, and the relative position of the heating element is important. In this regard, the inductor branch of the induction heating apparatus may be equivalent to a resistor and an inductor connected in series or in parallel, the equivalent inductor and resistance are the result of the coupling effect between the inductor and the load, and the inductance and resistance are affected by the coupling degree between the induction coil and the load. Which in turn affects frequency, output power, etc. Therefore, the present invention arranges the resonance coil 61 in the shape of a flat plate in parallel with the lower plane of the metal heating element, and also provides a positioning means for fixing the relative position thereof. The working state is stabilized, and the working pressure of the protection circuit is reduced.

The positioning device is composed of a positioning structure on the shell 1 and a positioning tray 7, which are matched with each other to fix the relative position.

The positioning structure on the housing 1 has various forms, but functions to position and restrict the movement of the heating element.

Two are presented here.

As shown in fig. 1 and 2, the upper case 12 is provided with 6 limit projections 123. The projection 123 protrudes from the four walls of the sink 124 of the upper case 12 to limit the movement of the positioning tray 7 and the heating element. The protrusion 123 may be higher than the depth of the sinking groove 124. When the depth of the sink 124 is zero, the projection 123 protrudes substantially entirely above the upper plane of the upper housing 12.

The other is that no limiting bump is provided, as shown in fig. 3 and 4. The upper housing 12 is provided with a guide groove 125, the groove walls on both sides of the guide groove are directly used as a limit, and the groove bottoms in the other two directions are respectively provided with a flange 126, the width of the flange is about 1 mm, and the protrusion is a circular arc and slightly higher than the groove bottom. When the positioning tray 7 or the heating element is inserted along the groove, the entering and exiting of the positioning tray can be prevented, but the entering or exiting cannot be prevented, so that the positioning function is realized.

The positioning tray 7 is shown in fig. 6 and 7. The length and width are generally matched with the electric heating mosquito-repellent incense tablet sold in the market, and the depth is slightly larger than the thickness of the mosquito-repellent incense tablet and is about 2.5 millimeters or more. Of course other shapes and sizes are possible.

The heated object is placed in the positioning tray 7.

Herein, the heated material means "a substance released into the air" after heating, such as a mosquito repellent, a freshener, vinegar, a perfume, and the like. The physical form may be solid, liquid, gel, etc. May be included in an adsorbent sheet < such as a mosquito mat >, etc.

The positioning tray 7 can be divided into two types according to the used materials: metal positioning trays and plastic positioning trays.

The metal positioning tray is formed by punching a 0.25-0.50 mm iron, aluminum or iron alloy plate. The outer peripheral surface is coated with a thick layer of heat resistant non-metallic material which is generally more temperature resistant than the plastic used for the housing 1, such as teflon or the like. Or directly made of heat-resistant plastic composite steel plates.

The metal positioning tray is also actually a heating body. When in use, the mosquito-repellent incense tablet is put into the corresponding position of the upper shell 12. When the device runs, alternating magnetic lines of force penetrate through the metal positioning disc to form a loop, and induced current is generated on the cross section of the loop, so that heat energy is generated. The mosquito-repellent incense piece releases mosquito-repellent gas when being heated.

The metal positioning tray can also be heated to fumigate other substances, such as spices, vinegar and the like. Putting the used mosquito-repellent incense tablet into a metal positioning tray, and dripping vinegar or other liquid medicine to be fumigated on the tablet to implement the method. The substance to be released by heating can also be directly placed in a metal positioning tray for heating.

The plastic used for the shell 1 generally has low temperature resistance, so the periphery of the metal positioning tray is coated with a thick layer of heat-resistant substance for isolation protection. So that the heating temperature can be increased accordingly.

The plastic positioning tray is made of a plastic that is more heat resistant than the housing 1. In addition to the positioning, the upper case 12 is also isolated from the object to be heated. This allows, on the one hand, the lower heat resistant upper housing 12 to be protected and, on the other hand, also for easy cleaning and maintenance. However, it cannot be a heating element and cannot heat an object to be heated. Therefore, the object to be heated must be provided with a heating element, that is, a metal.

Three kinds of heated objects with metal heating elements, which are called as adsorption sheets, will be described below. The reason is that the shapes of the mosquito repellent tablets are similar to those of the commercial electric heating mosquito repellent tablets, the mosquito repellent tablets are in a tablet shape, and the inside has uniformly distributed tiny holes, so that the mosquito repellent, the freshener and the like can be absorbed. When the heater works, the magnetic lines of force act on the metal in the heater to generate heat energy, and the gas required by people can be released.

The adsorption sheet can be in various shapes, is suitably flat, has large heating area, is uniform and rapid in heat transfer, and is favorable for releasing the medicament into the air. The size and thickness of the mosquito repellent mat can be equal to those of the electric heating mosquito repellent mat sold in the market.

Fig. 8, 9 and 10 show the metal composite paper adsorption sheet 9.

A piece of aluminum foil 92 is compounded between two paper sheets 91 made of fiber. As shown in phantom in fig. 9, the aluminum foil 92 is perforated with small holes to facilitate gas release upon heating, which is one form. Alternatively, as shown in fig. 11, a sheet of fibrous paper 91 is coated on one side with a layer of metal 93, which may be iron, aluminum or an iron alloy. A piece of aluminum foil can also be pasted on the aluminum foil, and holes do not need to be formed on the aluminum foil. When in use, the metal surface faces downwards.

The composite metal is used as a heating element. It is closely combined with the cellulose paper sheet, the heat transfer is uniform and efficient, and the effective components absorbed in the cellulose paper sheet are fully and uniformly released.

The second is a mixed metal powder paper adsorbent sheet.

The raw paper is prepared by adding metal powder into raw materials mainly comprising plant fibers in the process of manufacturing the raw paper of the electric heating mosquito incense. The powder is typically iron powder or iron alloy powder, but may also be aluminum powder, or a mixture of these powders. The particle size of the powder is slightly larger. The paper adsorption tablet can be used as mosquito-repellent incense tablet, and can also be used by dripping or soaking freshener, vinegar and the like.

Since the metal powder is uniformly distributed in the plant fiber, the temperature inside and outside the adsorption sheet is uniform during heating, which is more favorable for the volatilization of the liquid medicine and reduces the residual of the liquid medicine.

The third is a powder metallurgy iron-based adsorbent sheet, as shown in fig. 12.

The powder metallurgy iron-based adsorption piece is manufactured by a powder metallurgy process.

Powder metallurgy uses metal powder (or a mixture of metal powder and nonmetal powder) as raw material, and various metal parts or finished products are manufactured through molding and sintering. Since there is no melting process, the pores between the powder particles do not disappear and are uniformly distributed. By controlling the powder granularity, the molding pressure and the sintering process, the size of pores and the porosity of the material can be controlled, and various porous materials can be obtained. Thus, under the action of capillary action, a certain amount of liquid can be stored in the pores. The powder metallurgy metal adsorption sheet can be produced. The size can be referred to a commercial electric heating mosquito-repellent incense tablet. According to the requirements of induction heating technology, iron or iron alloy powder is preferably used as the raw material, so that the iron-based adsorption sheet is called powder metallurgy iron-based adsorption sheet. After the mosquito repellent and other medicinal materials are dropped or soaked on the induction heater, the induction heater can be used.

Its advantages are high temp and quick heating. Especially can be used repeatedly, the medicament is released, and the medicament can be reused only by dripping or dipping.

So far, several kinds of heating elements of the present invention have been introduced, namely: the adsorption device comprises a metal positioning tray, a metal composite paper adsorption sheet, a mixed metal powder paper adsorption sheet and a powder metallurgy iron-based adsorption sheet. All have a common feature that the heating body is generally in a sheet shape (the height of the metal positioning tray is negligible compared with the length and width dimensions), the bottom is substantially planar, and even if the metal powder is mixed into the metal powder paper adsorption sheet, the metal powder is uniformly distributed and can be regarded as the planar sheet.

Therefore, when the plastic positioning tray or the metal positioning tray containing the metal adsorption sheet is placed at the positioning position on the upper case 12, the relative positions of the resonance coil 61 and the heating element can be ensured to be fixed, and the stable operation of the induction heating system can be ensured.

Plastic retainer trays may also be eliminated if the size of the absorbent sheet is matched to the location of the retainer on the housing 12.

As shown in fig. 1 and 2, the housing 1 is also provided with a given and display circuit unit 8, which is actually a platform for a user to talk to the induction heater, and provided with keys 81 and a function display portion 82. The control drive protection circuit unit 3 can know what task the user wants to perform from the selection of the key 81, and the user can know information such as various operating states of the induction heater (e.g., fault display) from the function display portion 82. The display part is made of LED or nixie tube, liquid crystal display.

Fig. 13 is a block diagram showing the electrical relationship among the power circuit unit 2, the control drive protection unit 3, the inverter circuit unit 4, the resonant capacitor 5, the resonant coil 61 on the resonant coil disk 6, the display circuit unit 8, and the heating element in fig. 1.

The given and display circuit can set the operating condition of the induction heater. And the control drive protection circuit sends a control signal to the inverter circuit according to a given working condition. The inverter circuit converts a high direct current voltage from the high-voltage power supply circuit into a high-frequency alternating current voltage (or current), performs DC/AC conversion, and outputs the converted voltage to a resonant circuit including an inductor (resonant coil 61) and a capacitor (resonant capacitor 5), thereby generating a high-frequency alternating magnetic field. The magnetic force line acts on the heating body to generate heat energy.

The control drive protection circuit adjusts the sent control signal according to the data such as voltage and current fed back by the sampling circuit, so that the system can operate safely and stably.

A schematic diagram of the main circuit of the induction heater is shown in fig. 14.

This is a half-bridge resonant inverter circuit. One of the arms is composed of two capacitors C with the same characteristics and capacity₁、C₂Bearing, its electric capacity is very big; the other bridge arm is borne by power switching tubes VT1 and VT 2. The pulse output by the control drive protection circuit is changed into a pulseThe voltage transformer T1 is coupled to two coils W of opposite phases₂₁、W₂₂Through a resistance R₁、R₂Driving two MOSFETs VT1, VT2, respectively. The anti-series regulators VS1, VS2, VS3 and VS4 are used to limit the maximum positive and negative amplitudes of the driving pulses. VT1 and VT2 work in turn to convert DC power into AC power.

Diodes VD1 and VD2 connected in parallel with VT1 and VT2 are used for inductor current follow current, and are used for energy recovery access and eliminating partial transient overvoltage.

Capacitor C₄、C₅The circuit is used for buffering, suppressing overvoltage generated at turn-off moment of VT1 and VT2 and protecting the power switch tube from impact damage.

And a load is connected between the two bridge arms of the half-bridge inverter. In fig. 14, a heating winding L (i.e., the resonance coil 62 on the resonance coil disk 6 in fig. 1) and a resonance capacitor C of the resonance circuit are connected₃(i.e. the resonant capacitor 5 in fig. 1). The resonant frequency depends on the heating element, and is generally 30 to 100 kHz.

C₆、C₇、R₆～R₁₁RP, VD3, VD4 constitute sampling circuit, and wherein diodes VD3, VD4 are used as rectification to obtain DC sampling signals, and the signal voltage can be adjusted by potentiometer RP. After filtering and amplifying, the signal is sent to a control drive protection circuit.

R₅The sampling resistor is used for detecting current signals, and the current signals are sent to the control drive protection circuit after being processed.

And the control drive protection circuit adjusts the pulse signal output to the pulse transformer T1 according to the feedback signal so as to ensure the safe and stable operation of the system.

The pulse signals generated by the control drive protection circuit and sent to the pulse transformer T1 have various forms, one is a common square wave, and the other is a PWM signal which is commonly used at present. The PWM signal can be generated by a singlechip through programming, and can also be generated by a special integrated circuit.

In recent years, power electronics technology has been rapidly developed. The switching speed of a switching device in the inverter circuit is improved, and the switching loss is reduced, so that the on and off of the inverter circuit can be easily controlled.

Winding W to pulse transformer T1₁When pulse signals are input, the winding L is heated instantaneously to generate an alternating magnetic field, and the heating body emits heat. And the alternating magnetic field disappears immediately when the input pulse signal is turned off. So that the induction heater can be operated intermittently as desired by inputting an intermittent pulse driving signal. The pulse signal and the working frequency of the switching device are high, so the method of intermittently outputting power does not influence the normal work of the induction heater.

Similarly, the input to winding W of T1 is regulated₁The pulse duty ratio of the PWM signal can effectively control the output power.