KR100239360B1 - Circuit for switching of indnction heating cooker - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching circuit of an electronic cooker capable of heating a nonmagnetic container. In the related art, an IGBT element can not be driven at 80 KHz for heating a nonmagnetic container. Since there is a problem that a field effect transistor (MOS FET) must be used, there is a problem in that the cost of the product is relatively increased when applied to the actual product. Therefore, the present invention, in the electronic cooker to obtain a constant power by alternately operating the switching device by making the dead time using the pulse output from the timer, which is an external oscillator, switching using the dead time of the dead time adjustment unit to make a dead time A switching oscillation unit 103 for generating and outputting pulses for switching devices, and a container material detection unit 104 for detecting a current supplied to the container 113 and detecting a material of the container; A controller 105 for outputting a mode control signal according to the container material; An analog switch unit 107 for transmitting the output pulse of the switching oscillator 103; A heating mode determination unit 106 for controlling a switch operation of the analog switch unit 107; It is configured to include a double cycle switching unit 108 for outputting the output pulse of the switching oscillator 103 as it is or double cycle to heat not only a magnetic container but also a nonmagnetic container, and heats the nonmagnetic container with a general-purpose IGBT element. When applied to the product to lower the price.

Description

Switching circuit of electronic cooker {CIRCUIT FOR SWITCHING OF INDNCTION HEATING COOKER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching circuit of an electronic cooker for heating a nonmagnetic container, and more particularly to an electron cooker capable of heating a nonmagnetic container by realizing an LC load resonance that is twice the switching frequency while using a general-purpose IGBT element. The switching circuit of the cooker.

The switching circuit of the conventional electronic cooker includes a timer 10, which is an external oscillator for generating a pulse having a constant width, as shown in FIG. A dead time adjusting unit 20 for preventing simultaneous switching on / off during the switching operation of the switching elements by using the pulses generated by the timer 10; A switching oscillator 30 for performing Zero Voltage Switching (ZVC) to oscillate the switching element by using the pulse provided from the dead time controller 20; A rectifier 50 for rectifying the input commercial power AC into a DC voltage using a diode; An LC filter 60 that receives the DC voltage rectified through the rectifier 50 and filters and smoothes the power factor to improve the power factor; A switching unit (70) comprising two switches having an anti-parallel diode in series with the DC voltage provided through the LC filter (60) and switching according to a switching control signal to provide a resonance voltage to the working coil; A switching driver 40 for supplying a switching control signal to the switching element of the switching unit 70; It consists of a working coil (L1) to heat the container 80 by inducing an eddy current to the heating plate to be heated by the electromagnetic induction effect of the magnetic field generated by the resonance voltage of the switching unit 70. Reference numeral C1 denotes a resonant capacitor.

The prior art configured as described above will be described in detail with reference to FIGS. 1 and 2.

When the timer 10 used as the external oscillator generates a pulse (a point waveform) having a predetermined width as shown in FIG. 2A, the capacitor C5 and the resistance ( Differentiated by R1), the signal is converted into a pulse (b dot waveform) as shown in FIG. 2B, and input to the non-inverting terminal (+) of the operational amplifier OP1.

At this time, the reference voltage adjusted by the resistor R2 and the variable resistor VR1 is input to the inverting terminal (−) of the operational amplifier OP1.

The operation amplifier OP1 inputted as the non-inverting terminal (+) and the inverting terminal (-) compares the two values to find an error, and the obtained error is again converted to the non-inverting terminal of the operational amplifier OP2 of the next stage (+). )

The operational amplifier OP2 receives the reference voltage adjusted by the resistors R3-R5 through its inverting terminal (−) and outputs a value obtained by comparing the two values to the switching oscillator 30.

The reason for differentiating and performing arithmetic operation as described above is to set the dead time so that the switching elements S1 and S2 of the switching unit 70 can be switched in the zero state without being simultaneously turned on or off. To give.

The pulse output from the dead time adjusting unit 20 generates and outputs a pulse (c dot waveform) as shown in (c) of FIG. 2 through the noar gates NR1 and NR2 of the switching oscillator 30.

의 출력으로 입력한다.The c point waveform is connected to the clock pulse input Cp of the flip-flop D / FF and to one input of another NOR gate NR3 and NR4 so that when the input pulse Cp is rising, When the pulse inputted to the data input terminal D of the flop D / FF is output to the output terminal Q, the data input terminal D is an inverted output terminal.

Enter the output of.

을 통해 도 2의 (e)에서와 같은 펄스(e점파형)를 출력하게 되면, 그의 비반전출력단(Q)을 통해서는 도 2의 (d)에서와 같은 펄스(d점파형)를 출력한다.Therefore, the inverted output terminal of the flip-flop (D / FF)

When outputting the pulse (e point waveform) as shown in (e) of Figure 2 through, through the non-inverting output stage (Q) outputs the pulse (d point waveform) as shown in Figure 2 (d). .

The waveform input to the switching driver 40 is a pulse (f-point waveform) as shown in FIG. 2 (f) in which the c and d points are input from the noble gate NR3, and the c and e points are the noahgate. Pulses (g dot waveforms) as shown in FIG.

Comparing the waveforms output from the f point and the g point, it can be seen that there is a ZVS (ZERO VOLTAGE SWITCHING) section to prevent the switching elements S1 and S2 from being turned on or off at the same time.

When the control signal output from the switching driver 40 is a f-point waveform of the switching oscillator 30, if a high "high" is output, the switching element S1 of the switching unit 70 operates, and the switching oscillator 30 When the waveform is a high point of " g ", the " high " outputs the switching element S2 of the switching unit 70 to operate.

As described above, when the switching elements S1 and S2 alternately operate, LC resonance is generated by the working coil L1 and the resonant capacitor C1 to apply an eddy current to the vessel 80 placed on the upper surface of the working coil L1. Induction heating

At this time, the rectifier 50 rectifies the commercial power (ac) and outputs a DC voltage, the DC voltage is filtered and smoothed through the coil (L2) and the capacitor (C4) of the LC filter 60 switching unit ( 70).

However, in the prior art as described above, a nonmagnetic container such as aluminum has to be switched at a high frequency for induction heating due to the low resistance value and permeability of the material itself. Since it cannot be driven at 80KHz for heating, there is a problem that an expensive MOS field effect transistor (MOS FET) having a high voltage and high current rating must be used. Therefore, when applied to an actual product, the cost of the product is relatively high. .

Accordingly, an object of the present invention for solving the above problems is to implement an LC load resonance, which is twice the period of the switching frequency while using a general-purpose IGBT device, an electronic cooker capable of heating not only a magnetic container but also a nonmagnetic container. To provide a switching circuit of.

Another object of the present invention is to provide a switching circuit of an electronic cooker to reduce the cost by heating the non-magnetic container using the IGBT device to reduce the price when applying the product.

1 is a switching circuit diagram of a conventional electronic cooker.

2 is a signal timing diagram of each part in FIG. 1;

3 is a switching circuit diagram of the present invention.

4 is a signal timing diagram of each part in FIG. 3;

FIG. 5 is a waveform diagram of a gate driving voltage and a switching current of a switching device in FIG. 3.

5A is a waveform diagram when using a double cycle,

Fig. 5B is a waveform diagram when used at a general period.

*** Explanation of symbols for main parts of drawing ***

101: timer 102: dead time control unit

103: switching oscillation unit 104: container material detection unit

105: control unit 106: heating mode determination unit

107: analog switch unit 108: double cycle switching unit

109: switching driver 110: rectifier

111: smoothing part 112: switching part

113: container RY: relay

The present invention for achieving the above object, the control unit for outputting a mode control signal according to the container material; An analog switch unit for transmitting an output pulse of the switching oscillation unit for controlling the switching element; A heating mode determination unit which outputs a signal for controlling a switch of the analog switch unit; The output pulse of the switching oscillation unit is provided as it is or double cycle to output to the switching drive to provide a double cycle switching unit for adjusting the frequency, it is possible to apply not only to the magnetic container but also the non-magnetic container with a general-purpose IGBT element to be applied to the product In this case, it is characterized in that the cost can be lowered.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 is an embodiment of a switching circuit of the electronic cooker of the present invention, and as shown therein, a timer 101 which is an external oscillator for generating a pulse having a constant width; A dead time adjusting unit (102) for preventing simultaneous switching on and off during the switching operation of the switching elements by using the pulses generated by the timer (101); A switching oscillator 103 for adjusting a pulse width to have a frequency for switching a switching element by using a pulse provided from the dead time controller 102; A container material detecting unit 104 for detecting a current supplied to the container 113 and detecting a material of the container; A controller 105 for outputting a mode control signal according to the material of the container detected above; An analog switch unit 107 for transmitting the output pulse of the switching oscillator 103; A heating mode determination unit 106 for controlling a switch operation of the analog switch unit 107; And a double period switching unit 108 for outputting the output pulse of the switching oscillator 103 to the switching driver 109 as it is or in a double cycle.

The heating mode determining unit 106 receives two output signals output from the control unit 105 through the resistors R9 and R10 (R12 and R13), respectively, and conducts or blocks the transistors to control the switch operation. It consists of Q1) (Q2).

The double-period switching unit 108 divides the flip-flop D / FF1 for dividing the input pulse into two, the output pulse of the flip-flop D / FF1 and the output pulse of the switching oscillator 103. It is composed of a duty ratio adjustment unit 81 that receives each input to determine the duty ratio.

Referring to the operation and effect of the present invention configured as described in detail as follows.

When the timer 101 outputs a pulse (a dot waveform) having a predetermined width to the dead time adjusting unit 102 as shown in FIG. 4A, the condenser C4 of the dead time adjusting unit 102 Differentiated by the resistor R1, a pulse (b dot waveform) as shown in b) of FIG.

The b-dot waveform pulse is again input to the non-inverting terminal (+) of the first operational amplifier OP1 and adjusted by the resistors R2 to R4 with the inverting terminal (-) of the first operational amplifier OP1. Input the reference voltage.

In this way, the first operational amplifier OP1 that receives a predetermined value through the non-inverting terminal (+) and the inverting terminal (-) compares the two values and obtains an error, and the obtained error is again converted into the second operational amplifier (OP2). Output to non-inverting terminal (+).

Then, the second operational amplifier OP2 receives the reference voltage adjusted by the resistors R5-R7 through the inverting terminal (-), and then compares two values respectively input to the two terminals (+) (-). The pulse is output to the switching oscillator 103.

The reason for performing the derivative operation and the operation operation on the pulse input from the dead time adjusting unit 102 as described above is that the switching elements S1 and S2 are not simultaneously turned on or off and are zero. This is to set the dead time so that each can be switched in the state.

The pulse output from the dead time controller 102 generates and outputs a pulse (c dot waveform) as shown in c of FIG. 4 through the NOR gate NR1 and NR2 of the switching oscillator 103.

The c point waveform is input to one side of the clock pulse input terminal Cp of the flip-flop D / FF and the NOR gates NR3 and NR4, respectively.

과 연결되어 그의 출력을 입력으로 한다.When the pulse input to the clock pulse input terminal Cp of the flip-flop D / FF rises, the pulse input to the data input terminal D is outputted to the output terminal Q, where the data input terminal D Silver inverted output

Is connected to and its output is input.

의 펄스가 입력되는데, 상기 반전출력단

의 출력펄스는 출력단(Q)의 펄스와 반대위상을 갖는 도 4의 e)에서와 같은 펄스(e점파형)와 같다.That is, when the pulse inputted to the clock pulse input terminal Cp of the flip-flop D / FF rises, the signal output through the output terminal Q is the same pulse as the d) of FIG. 4 (d dot waveform). To the data input terminal (D)

Pulse is inputted to the inverting output stage.

The output pulse of is equal to the pulse (e-dot waveform) as in FIG.

The noble gate NR3 receives the output pulse of the noble gate NR2 (dotted c waveform) and the output pulse of the flip-flop D / FF (d dot waveform), respectively, and performs the nealing. A pulse is generated and output as in Equation 2, and the noble gate NR4 inputs an output pulse of the noble gate NR2 (c dot waveform) and an output pulse of the flip-flop D / FF (e dot waveform), respectively. It receives the pulse and outputs the pulse as shown in g) of FIG. 4.

In this case, when the container 113 is placed on the working coils L1 and L2 which are heating plates, the current flowing through the AC input is detected by the current detector C / T and provided to the container material detecting unit 104. A pulse (A point) detected through the rectifier 41 of the 104 and the condensers C5 and C6 and the integrator 42 is output, and the A point voltage is an experimentally calculated value according to the type of the container. Look-up table is used to output the tabled values.

That is, when the container 113 is a magnetic container such as 430 series and a storm, less than about 2.0 V to 2.5 V, and about 1.0 V less than a nonmagnetic container made of aluminum and 304, and 2.5 is a nonmagnetic container made of pure 304 series. Tableed above V

When the container material detecting unit 104 determines that it is a nonmagnetic container and outputs a 1.0 V voltage value corresponding thereto, the container material detecting unit 104 receives the voltage value from the control unit 105 to determine the nonmagnetic mode.

Then, the control section 105 outputs a high signal to its A terminal and a low signal to its B terminal.

Then, the transistor Q1 of the heating mode determination unit 106 is turned on, and the transistor Q2 is turned off.

Since the transistor Q1 is turned on, the collector side of the transistor Q1 is turned low, and the first and second analog switches Sa and Sb are turned off, and the transistor Q2 is turned off. The collector side of the transistor Q2 is in a high state, and the third and fourth analog switches Sc and Sd are in a conductive state.

Accordingly, the pulses (f-point waveform and g-dot waveform) output from the third and fourth NOR gates NR3 and NR4 of the switching oscillator 103 are input to the double period switching unit 108.

The output pulse of the third NOR gate NR3 is input to one side of the OR gate OR1 and is also input to the clock pulse input terminal Cp of the dip-flop D / FF1.

과 연결되어, 상기 반전출력단의 출력펄스를 입력펄스로 한다.When the pulse input to the clock pulse input terminal Cp of the flip-flop D / FF1 rises, the pulse input to the data input terminal D is outputted. Herein, the data input terminal D is an inverted output terminal.

Connected to the output pulse of the inverted output stage as an input pulse.

의 출력펄스는 도 4의 h), i)에서와 같다.Therefore, the output terminal Q and the inverted output terminal of the deflip-flop D / FF1

The output pulse of is as in h), i) of FIG.

의 i)점 펄스를 각각 입력받아 앤드링하여 도 4의 k)에서와 같은 펄스(k점 파형)를 만들어 스위칭 구동부(109)로 출력한다.Then, the OR gate OR1 is the f-point pulse of the third NOR gate NR3 of the switching oscillator 103 and the h-point of the output terminal Q of the flip-flop D / FF1 of the double period switching unit 108. The pulses are input to each other to generate a pulse (j point waveform) as in j of FIG. 4, and the AND gate AD1 doubles with the g point pulse of the fourth NOR gate NR4 of the switching oscillator 103. Inverted output terminal of the de-flip flop D / FF1 of the period switching unit 108

I) point pulses are inputted and ringed to generate a pulse (k point waveform) as shown in k) of FIG. 4 and output to the switching driver 109.

In other words, when the flip-flop D / FF1 is divided into two outputs, the orifice OR1 and the AND gate AD1 are logically combined to determine and output the duty ratios of the switching elements S1 and S2.

As a result, the double cycle switching unit 108 makes a double cycle of the pulse provided by the switching oscillation unit 103 when the nonmagnetic container is placed on the heating plate, and the switching elements S1 and S2 are 75% and 25%, respectively. The duty ratio adjusted to alternately operate at a ratio is output to the switching driver 109.

Accordingly, the switching driver 109 alternately switches the switching elements S1 and S2 of the switching unit 112 when the third and fourth switches Sc and Sd of the analog switch unit 107 are turned on.

At this time, if the container placed on the heating plate is a non-magnetic container, the relay switch RY is turned off, and both the working coils L1 and L2 are operable, and the switching driver 109 switches to generate a high frequency of 80 KHz or higher. The elements S1 and S2 are alternately operated at a rate of 75% and 25%.

When any one of the switching elements (S1, S2) is turned on to provide a direct current eye from the rectifying unit 100 and the smoothing unit 111, the working coil (L1, L2) and the resonant capacitor (C2, C3) is continuous It becomes a resonance state.

Therefore, a large resonance current flows through the working coils L1 and L2.

At this time, a high frequency is generated by the resonant capacitor C1.

Magnetic fields are generated in the working coils L1 and L2 by the resonance current, and eddy currents are induced in the cooking vessel 113 by the electromagnetic induction effect, thereby heating the food in the container as the cooking vessel is heated. The desired dish is processed.

At this time, the switching current waveform of the switching element S1 and the gate driving waveform of the switching element S2 are as shown in FIG.

When the container material detecting unit 104 detects the magnetic container or the nonmagnetic container made of pure 304 series and outputs it to the control unit 105, the control unit 105 is the same magnetic material when the magnetic container or the nonmagnetic container made of pure 304 series is manufactured. Mode is determined, and a low signal is output to the A terminal and a high signal is output to the B terminal.

In the case of the non-magnetic container made of pure 304 series, the reason for heating in the magnetic mode is that the material of the pure 304 series container is close to the magnetic container, and thus, higher efficiency can be expected when heated in the magnetic mode.

When the control unit 105 outputs a low signal to terminal A, the transistor Q1 of the heating mode determination unit 106 is turned off and the transistor Q2 is turned on.

Since the transistor Q1 is turned off, the collector side of the transistor Q1 is in a high state, and the first and second analog switches Sa and Sb of the analog switch unit 107 are brought into a conductive state, and the transistor ( Since Q2) is turned on, the collector side of the transistor Q2 is turned low, and the third and fourth analog switches Sc and Sd are turned off.

Accordingly, the pulse driver (f-point waveform, g-dot waveform) output from the third and fourth NOR gates NR3 and NR4 of the switching oscillator 103 does not go through the double cycle switching unit 108 but directly the switching driver 109. ) Is entered.

Accordingly, the switching driver 109 alternately operates the switching elements S1 and S2 of the switching unit 112 to generate a frequency of 25 KHz.

At this time, the relay switch RY is turned on so that only one working coil L1 can be operated.

For example, when the switching element S1 is turned on, the switching element S2 is cut off, and the rectified and smoothed DC voltage is supplied from the rectifying unit 110 and the smoothing unit 111 to the switching unit 112.

As a result, the working coil L1 and the resonant capacitors C2 and C3 are continuously in a resonance state.

Therefore, a resonance current flows through the working coil L1.

The magnetic field is generated in the working coil (L1) by the resonance current, the eddy current is induced in the cooking vessel 113 by the electromagnetic induction effect by the magnetic field, the food in the container is heated as the cooking vessel is heated to the desired Cooking proceeds.

At this time, the switching current waveform of the switching element S1 and the gate driving waveform of the switching element S2 are as shown in b) of FIG. 5.

As described above, the driving frequency duty of the switching element composed of the IGBT element is driven differently so as to be heated not only the magnetic container but also the nonmagnetic container.

As described above, the present invention realizes LC load resonance, which is twice the switching frequency while using a general-purpose IGBT switching device, so that not only magnetic containers but also non-magnetic containers can be heated to lower costs when applied to products. There is one effect.

Claims (7)

In an electronic cooker which uses a pulse output from an external oscillator to make a dead time to alternately operate a switching device to obtain a constant power, a frequency for switching the switching device with respect to an output pulse of the dead time controller for making the dead time. Switching oscillator for adjusting the pulse width to have a; A container material detecting unit detecting a current supplied to the container and detecting a material of the container; A control unit for outputting a mode control signal according to the container material detected above; An analog switch unit for transmitting or blocking an output pulse of the switching oscillator unit; A heating mode determination unit for controlling a switch operation of the analog switch unit; And a double cycle switching unit for outputting the output pulse to the switching driver after determining the duty ratio as it is or making the output pulse of the switching oscillation unit as it is or twice the cycle. The switching circuit of the electronic cooker according to claim 1, wherein the heating mode determining unit comprises two transistors for controlling the switch by conducting or blocking in response to the mode control signal of the controller. The switching circuit of an electronic cooker according to claim 1, wherein the analog switch unit comprises four switches. 2. The apparatus of claim 1, wherein the double period switching unit comprises: a flip-flop for dividing the pulse input from the switching oscillation unit into two divisions; And a duty ratio adjuster configured to receive the output pulses of the flip-flop and the switching oscillator to determine the duty ratio of the switching device. 5. The apparatus of claim 4, wherein the duty ratio adjusting unit comprises: an oar gate configured to receive and output one output pulse of the switching oscillator and one output pulse of the flip-flop; And an AND gate configured to receive and output the other output pulse of the switching oscillation unit and the inverted output pulse of the flip-flop, respectively. The switching circuit of the electronic cooker according to claim 4, wherein the duty ratio is determined at a ratio of 25% and 75%. The switching circuit of an electronic cooker according to claim 1, wherein the control unit determines that the container made of pure 304 series is in the magnetic mode.

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