JPH0219200A - induction heating iron - Google Patents

Abstract

PURPOSE:To effectively heat an iron main body and, simultaneously, to simplify a driving circuit by simultaneously turning on and off plural high potential side switching elements or plural low potential side switching elements. CONSTITUTION:A coil selecting circuit 42 detects the position of an iron 21 main body, and when it is located in the vicinity of a heating coil 31, an output terminal C and an output terminal D are made into High and Low, respectively. In such a case, for the side of an inverter 26, a high potential side switching element 29 and a low potential side switching element 30 are alternately turned on, and for the side of an inverter 27, since a high potential side switching element 33 is simply turned on and off repeatedly and a low potential side switching element 34 remains off, a high frequency current is made to flow to the heating coil 31, and however, the current is not made to flow to a heating coil 35. Consequently, the iron 21 main body can be effectively heated, and an unnecessary radiation from the heating coil 35 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an induction heating iron for general household use.

BACKGROUND OF THE INVENTION Conventional induction heating irons generally have difficulty covering the entire surface of an ironing board with one heating coil, and cannot heat the iron if it comes off the heating coil. Therefore, an induction heating iron having a plurality of heating coils has been proposed.

Problems to be Solved by the Invention However, in induction heating irons that use a half-bridge inverter, the number of switching elements is twice as many as the number of heating coils, making their drive circuits complex and increasing the number of parts. .

The problem was that it was expensive and heavy.

The present invention solves the above-mentioned conventional problems.The first purpose of the present invention is to efficiently heat the iron body and simplify the drive circuit, and the second purpose is to provide no current at all to the heating coil that is not used for the purpose. The purpose of the present invention is to provide an induction heating iron that prevents water from flowing.

Means for Solving the Problems In order to achieve the first object, the present invention includes an iron main body, a DC power source, a plurality of inverters connected to the DC power source, and a control circuit for the inverters. The inverter has a series circuit of two switching elements and a load circuit connected to a midpoint of the series circuit, and the control circuit includes at least one capacitor and a heating coil for inductively heating the iron body. The control circuit simultaneously turns on and off a plurality of high-potential side switching elements or a plurality of low-potential side switching elements.

In order to achieve the second objective, the load circuit is composed of a series connection of an energizing coil and a capacitor, and when the control circuit turns on and off multiple high-potential side switching elements at the same time, the load circuit Connected between the positive terminal of the power supply and the middle point of the series circuit of switching elements, and when the control circuit turns on and off multiple low-potential side switching elements at the same time, between the negative terminal of the DC power supply and the middle point of the series circuit. The one connected to the monkey.

Operation With the above configuration, the control circuit simultaneously turns on and off the high-potential side and low-potential side switching elements, so that only the necessary heating coils can be driven. Also, by considering the connection of the load circuit, no current is allowed to flow through unnecessary heating coils.

Embodiment FIG. 1 shows a diagram of an induction heating iron according to a first embodiment of the present invention. In FIG. 1, 21 is the iron body, 22 is a DC power supply built into the iron body 21, AC power supply 23. It is composed of a rectifier 24. 25
is a smoothing capacitor, 26 is a half-bridge type inverter, and 29 is the same as the high-potential side switching element using IGET (low-potential side switching element 30 is using IGBT), heating coil/I/31 and resonance capacitor. 32
It is composed of a load circuit 58' consisting of: 27 is an inverter having the same configuration as the inverter 26, and includes high potential side switching elements 33. Low potential side nutwitching element 34. It consists of a load circuit consisting of a heating coil 35 and a capacitor 36. 28 is a control circuit, and a drive circuit 37. dry 1
Circuit 38. Drive circuit 39. DC power supply 402 oscillation circuit 41. Coil selection circuit 42. AND circuit 43. It is composed of an AND circuit 44.

The drive circuit 3γ includes transistors 45. Palsutoone 48. Diode 47. Resistance 48. transistor 49
．． Diode 50. Resistance 61. It is made up of a transistor 52.

Drive circuit 38 includes transistors 63 . Transinuta 64. The drive circuit 39 is composed of a resistor 66 and a transistor 56. 67 and a resistor 58, and is similar to the drive circuit 38.

The operation in the above configuration will be explained. Figure 2 (1) and (
2) is the voltage v of the outputs A and B of the oscillation circuit 41 in FIG.
It is a waveform diagram of A and VB. As shown in FIG. 2, both vA and VB are alternately high for a time T1, during which time there is a 12-hour dead time in which both A and B are low.

In addition, the operation of the coil selection circuit 42 is to detect the position of the iron main body 21, and when it is near the heating coil 31, output terminal C is set to High, output terminal C is set to Low, and the position of the iron main body 21 is set near the heating coil /l/35. If present, Dtl-High
h, set C to Low.

Next, the operation of this circuit when C is High and D is Low will be described. In this case, the output of the AND circuit 44 is always L.
ow, and the switching element 34 is turned off. AN
The output of D circuit 43 matches VB. In other words, B is Hi
During the period gh, the switching element 30 is turned on by the action of the transistor 63, and when B is LowO, the switching element 30 is turned off by the transistor 64.

When vA is HighO, the transistor 45 is turned on and a voltage is applied to the primary side of the pulse transformer 46. Therefore, the voltage generated on the secondary side passes through the diode 4γ and the diode 5o to the switching element 29. A voltage is applied to the gate of the switching element 33 to turn it on. vA is Lo
When the voltage becomes W, the transistor 46 is turned off, and a reverse voltage is generated in each coil of the pulse transformer 46 due to the excitation energy stored during the on period. Therefore, the transistor 49. The pace of transistor 52 is reduced;
Switching element 30. The switching element 34 becomes zero bias and turns off. In other words, output terminal C is High.
, When the output terminal is Low, the switching element 29 and the switching element 30 of the inverter 26 are turned on alternately, but the switching element 33 of the inverter 27 is only turned on and off repeatedly, and the switching element 29 and the switching element 30 are turned on alternately. 34 remains off, heating coil 3
A high frequency current flows through the heating coil 35, but not through the heating coil 35.

Therefore, the iron main body 21 can be heated efficiently, and unnecessary radiation from the heating coil 35 can be prevented.

In this circuit, the load circuits 58' and 59 are connected to the DC power supply 22.
The heating coil is not used because it is connected between the positive pole of the switch and the midpoint of the series circuit of switching elements 29, 30.33°34 (capacitor 36 when output terminal C is High and output terminal R is Low). Since the series capacitor is not charged at all, there is an effect that no current flows through the heating coil 36.

In particular, in this embodiment, since both the switching element 29 and the switching element 33 are simultaneously driven by the drive circuit 3, only one transistor 46 is required, and one pulse transformer 46 is also required, resulting in a considerable number of parts, cost, and It has the effect of reducing weight.

FIG. 3 is a circuit diagram of an induction heating iron according to a second embodiment of the present invention. In Fig. 3, the iron body 21
．． DC power supply 22. The capacitor 25 has the same configuration as in the first embodiment. The inverter 26 is the same as the first embodiment except that the capacitor 32 and the capacitor 36 are connected to the low potential side of the DC power supply 22.

The control circuit 28 includes a drive circuit 60. Drive circuit 61
．． )'Live circuit 62. DC power supply 40. Coil selection circuit 424 oscillation circuit 41. AND circuit 63°AND circuit 64
It is made up of.

The drive circuit 60 includes transistors 65 . Pulse transformer 66, diode 67, resistor θ8. transistor 69
The drive circuit 61 also has a drive circuit 6o.
It has the same configuration as transistor 70. Pulse transformer 71. Diode 72° Resistor 73. Consists of 4 transistors. The drive circuit 62 is made up of a transistor 76, a transistor 76°, and a resistor 7. The coil selection means 42 and oscillation circuit 41 are still the same as in the first embodiment.

The operation in the above configuration will be explained.

When the iron body 21 is near the heating coil 31,
The output of the coil selection circuit 42 is such that the output terminal C is High.
h, the output terminal becomes Low, and the AND circuit 63
The output of the AND circuit 64 matches vA, and the output of the AND circuit 64 is always L.
It becomes OW. Therefore, when vA is High, the transistor 66 is turned on and a voltage is applied to the primary side of the pulse transformer 66, and the voltage generated on the secondary side turns on the switching element 29 through the diode 67.

When VB becomes Low, transistor 65 is turned off, and a reverse voltage is generated in each winding of pulse transformer 66, which slows down transistor 69 and turns off switching element 29.

On the other hand, the transistor 74 remains off, so the secondary side of the pulse transformer 74 is always at zero volts.
Switching element 3 whose pace is being lowered
3 is always off.

When VB becomes Hiqh, the switching element 3o and the switching element 34 are both turned on by the action of the transistor 75, and when VB becomes Low, the switching element 30 and the switching element 34 are both turned off by the action of the transistor 6.

That is, when the output terminal C is High and the output terminal R is Low, the switching element 29 and the switching element 30 of the inverter 26 are turned on alternately, but the switching element 34 of the inverter 2A is turned on and off. By simply repeating the above, since the switching element 33 remains off, the high frequency current flows through the heating coil 31 but does not flow through the heating coil 36.

In this circuit, since the capacitor 32 and the capacitor 36 are connected to the low potential side of the DC power supply 22, there is an effect that no current flows through the heating coils that are not used, similar to the first embodiment.

In the second embodiment, since only one drive circuit 62 is required, there is an effect that only one NPN transistor, one PNP transistor, and one resistor are required.

Although the first and second embodiments both show cases in which there are two inverters, even in the case where there are more inverters, a large number of high-potential side switching elements 2 turn on and off low-potential side switching elements at the same time. By doing so, the same effects as in this embodiment can be obtained.

Effects of the Invention As is clear from the above embodiments, the induction heating iron of the present invention can efficiently heat the iron body by turning on and off a plurality of high-potential side switching elements or a plurality of low-potential side switching elements at the same time. In addition, it is possible to provide an induction heating iron with a simple drive circuit, a small number of parts, a low cost, and a light weight. Furthermore, by considering the connection of the load circuit, it is expected that no current will flow through unnecessary heating coils.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an induction heating type iron according to a first embodiment of the present invention, FIG. 2 is an operating waveform diagram of the oscillation circuit of FIG. 1, and FIG. 3 is an induction heating iron according to a second embodiment of the present invention. It is a circuit diagram of a heating type iron. 21...Iron body, 22...DC power supply, 26°2...Inverter, 28...
...Control circuit, 58゜59...Load circuit, 3
2.36... Condenser t, 3j, 35... Heating coil, 29.33... High voltage side switching element, 30.34... Low potential side switching element. Name of agent: Patent attorney Shigetaka Awano and 1 other person 2nd
figure

Claims (2)

[Claims] (1) It has an iron main body, a DC power supply, a plurality of inverters connected to the DC power supply, and a control circuit for the inverter, and the inverter includes a series circuit of two switching elements and a control circuit for the series circuit. The control circuit includes at least one capacitor and a heating coil that inductively heats the iron body, and the control circuit includes a plurality of high-potential switching elements or a plurality of low-potential switching elements. An induction heating iron that turns on and off the potential side switching elements at the same time. (2) The load circuit is composed of a heating coil and a capacitor connected in series, and when the control circuit turns on and off multiple high-potential side switching elements at the same time, the load circuit is configured by connecting the positive terminal of the DC power supply and the switching elements in series. 2. The control circuit according to claim 1, wherein the control circuit is connected between a midpoint of the circuit, and when the control circuit turns on and off a plurality of low-potential side switching elements at the same time, the control circuit is connected between the negative electrode of the DC power supply and the midpoint of the series circuit. Induction heating iron.