KR19990048885A - Induction heating cooker combined with magnetic and non-magnetic - Google Patents

Abstract

The present invention relates to an induction heating cooker for both a magnetic and a non-magnetic type. In the prior art, switching is performed at a high frequency by using a switching device at a high speed so that the price of the driving device is expensive. In heating the magnetic mode, There is a problem that when the container position deviates from the coil area by more than half of the coil area, the error increases and the reliability of the product tends to deteriorate. Therefore, the present invention is characterized in that the switching elements S1 and S2 of the inverter unit 3 for driving the resonance tank of the heating unit 4 are provided with the two-period drive unit 12 between the switching oscillation unit 6 and the switching drive unit 11, The on-signal having 75% duty and 25% duty is applied during operation so that the load resonance is doubled, the container is judged by using all of the working coil usage area, and heating is carried out. And switching is performed at a high frequency by using a general-purpose switching device so as to lower the cost of the driving device.

Description

Induction heating cooker combined with magnetic and non-magnetic

The present invention relates to an induction heating cooker for performing both a magnetic and a non-magnetic heating operation, and more particularly to a magnetic and non-magnetic induction heating cooker capable of performing switching at a switching cycle twice as high as using a general- To an induction heating cooker for both magnetic and non-magnetic induction which can be heated in an optimal heating mode by automatically detecting a container placed thereon.

As shown in FIG. 1, the conventional induction heating cooker has a rectifying section 1 for rectifying and rectifying input commercial power to a pulsating DC voltage, a smoothing circuit 1 for smoothing a pulsating DC voltage applied through the rectifying section 1, A smoothing unit 2 for making a constant direct current voltage and switching two switching elements S1 and S2 having an anti-parallel diode formed in series in accordance with a switching control signal of a DC voltage smoothed through the smoothing unit 2, (L1, L2) for inducing an eddy current to be heated in a container to be heated by an electromagnetic induction effect by a magnetic field generated by a resonance voltage of the inverter section (3) And a load selection relay for selecting whether or not the working coils L1 and L2 are connected for the resonance tank configuration according to the material of the heating vessel RY1, An input current detection unit 16 for detecting an input current flowing through the working coil 1 by using an input transformer 9, a high frequency current detection unit 7 for detecting a current flowing through the working coil by using a high frequency transformer 10, A control unit 8 for outputting control signals according to the currents inputted through the input current detection unit 16 and the high frequency current detection unit 7, (ZVC) for oscillating the switching element by using the pulse provided by the dead time adjusting unit (5). The dead time adjusting unit (5) And a switching driver 11 for controlling on / off operations of the switching elements S1 and S2 of the inverter unit 3 according to output signals of the switching oscillating unit 6. [

A detailed description will be made of the conventional art constructed as above.

When the commercial power is input through the power input terminal, the rectified current is rectified by the rectifier 1 and outputted using the bridge diode.

The pulsating DC voltage is smoothed again by the smoothing unit 2 composed of the inductance L2 and the capacitor C4 and the smoothed DC voltage is output to the inverter unit 3.

At this time, when the user puts the heating container on and turns on the start key, the control unit 8 recognizes it and selects the container detection frequency and outputs it to the dead time control unit 5 (S1).

The dead time adjusting unit 5 sets a dead time for preventing the switching elements S1 and S2 of the inverter unit 3 from being turned on at the same time and outputs a pulse corresponding to the set dead time to the switching oscillating unit 6 .

The switching oscillation unit 6 outputs a corresponding switching control signal to the gates of the switching devices S1 and S2 of the inverter unit 3 through the switching driving unit 11. [

At this time, the load selection relay RY1 is turned on (S2)

Then, the resonance tank is constituted by the working coils L1 and L2 of the heating unit 4 and the resonance capacitors C1, C2 and C3.

At this time, when the input transformer 9 detects the input current and transmits it to the controller 8 through the input current detector 16, the controller 8 reads the input current value (S3) The container material corresponding to the current value is determined.

The high frequency current flowing from the high frequency transformer 10 to the heating unit 4 is detected and outputted to the control unit 8 through the high frequency current detecting unit 7 (S5).

Then, the control unit 8 reads a value corresponding to the high-frequency current from the preset table to determine whether or not the object is loaded. (S6)

The heating mode is determined (S7) in the magnetic mode or the non-magnetic mode by the operation as described above, and then the heating is performed for a predetermined time (S8)

The relay RY1 maintains the off state so that the heating unit 4 forms the resonance tank with the working coils L1 and L2 and the resonance capacitors C1 and C2 and C3.

At this time, when the switching element S2 is turned off and the switching element S1 is turned on in the inverter section 3 by the switching control signal as shown in Fig. 2, the resonance tanks L1, L2, C1, C2, C3, the input voltage Vd is applied, the resonance starts, the current of the working coil rises, and the resonance capacitor C1 is charged by the resonance current.

When the switching element S1 is turned off before the resonance half period passes, the resonance tank and the capacitors C4 and C5 perform the auxiliary resonance so that the voltage of the capacitor C1 drops to 0 from the input voltage Vd, C4 rise from 0 to Vd.

Since the anti-parallel diode D2 of the switching element S2 is turned on and the zero voltage is applied to the resonance tank, the resonance occurs continuously by the charging voltage in the resonance capacitor C1 and the resonance current due to the resonance increases in the opposite direction.

Thereafter, when the switching element S2 is turned off before the resonance half period passes, the resonance tank and the capacitors C4 and C5 perform the auxiliary resonance so that the voltage of the capacitor C4 drops from Vd to 0, and the voltage of the capacitor C5 Rises from 0 to Vd.

Then, the anti-parallel diode D1 of the switching element S1 is turned on, and the resonance tank is supplied with the voltage Vd, so that the resonance continues to occur. At this time, the switching element S1 is turned on under the zero voltage condition.

Accordingly, when the resonance current drops to zero due to the continued resonance, a magnetic field is generated in the working coil L of the heating unit 4 by the current induced by the above-mentioned operation after the operation of one period is completed, The heating operation of the load is performed by generating an eddy current in the load of the container.

On the other hand, in order to heat the magnetic container, the load selection relay RY1 is turned on, and the operation is the same as the above operation. The only difference is that the resonance tanks are made of L1, C2, and C3.

However, in the conventional art as described above, switching is performed at a high frequency by using a high-speed switching element, so that the cost of the driving element is high. In the magnetic mode heating, the use area of the working coil is used only half, There is a problem that when the container position deviates from the coil area by more than half of the coil area, the error increases and the reliability of the product tends to be lowered.

Accordingly, it is an object of the present invention to overcome the above-mentioned problems of the prior art, and it is an object of the present invention to provide a magnetic induction heating apparatus and a magnetic induction heating apparatus which can perform switching at a switching cycle twice using a general- It is in providing the cooker.

It is another object of the present invention to provide an induction heating cooker for both magnetic and non-magnetic induction which can be safely used without limitations depending on the position of the container placed by heating using the entire working area of the working coil.

It is still another object of the present invention to provide an induction heating cooker for both a magnetic and a non-magnetic type which can automatically detect a container placed thereon and heat it in an optimal heating mode.

1 is a circuit diagram of a conventional induction heating cooker for both magnetic and non-magnetic cooking.

Fig. 2 is a switching waveform diagram of the switching element in Fig. 1; Fig.

FIG. 3 is a flowchart of a conventional method for determining a load of a magnetic induction cooker with both magnetic and non-magnetic characteristics.

Fig. 4 is a circuit diagram of a combination of the magnetic and non-magnetic induction heating cookers of the present invention. Fig.

Fig. 5 is a switching waveform diagram of the switching element in Fig.

FIG. 6 is a heating mode classification table according to a heating mode in FIG.

FIG. 7 is a distribution chart of the current voltage according to the container in FIG.

FIG. 8 is a flow chart of the operation of the induction heating cooker for both magnetic and non-magnetic cooking.

Description of the Related Art [0002]

1: rectification part 2: smooth part

3: Inverter section 4: Heating section

5: Dead time control unit 6: Switching oscillation unit

7: High-frequency current sensing unit 8:

9: Input transformer 10: High frequency transformer

12: 2 period drive units RY1 to RY3: Load selection relay

According to an aspect of the present invention, there is provided an induction heating apparatus including: a rectifying unit for rectifying an input AC power; a working coil for heating the cooking vessel; a heating unit including a resonance capacitor for flowing a resonance current to the working coil; A control unit for detecting a current flowing through the AC input power source and a current flowing through the working coil to determine a heating container; a control unit for receiving an output signal of the control unit through a dead time control unit and a switching oscillation unit, And a switching driving unit for controlling the resonance tank of the heating unit by the alternating operation of the switching elements of the inverter unit in accordance with the pulses output from the two-period driving unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 4 is a circuit diagram of a combined induction heating cooker according to the present invention. As shown in FIG. 4, the rectifying unit 1 rectifies an input commercial power to a pulsating DC voltage, A smoothing unit 2 for smoothing a pulsating DC voltage through the smoothing unit 2 to make a constant DC voltage through the smoothing unit 2 and a switching unit An inverter unit 3 for switching the elements S1 and S2 to generate a resonance voltage and an induction coil for inducing an eddy current in a container to be heated by an electromagnetic induction effect by a magnetic field generated by a resonance voltage of the inverter unit 3 A heating unit 4 composed of first to third load selection relays that form resonance tanks and resonance capacitors C1, C2 and C3 for adjusting the resonance tanks, Flows into the rectifying section (1) An input current detection unit 16 for detecting an input current by using an input transformer 9, a high-frequency current detection unit 7 for detecting a current flowing through the working coil by using a high-frequency transformer 10, A control unit 8 for outputting a control signal according to the current inputted through the high frequency current detecting unit 16 and the high frequency current detecting unit 7, A switching oscillation unit 6 for performing zero voltage switching (ZVC) to oscillate the switching device using pulses provided by the dead time adjusting unit 5; A two-period drive unit 12 for doubling the load resonance when two switching elements are driven according to an output signal of the switching oscillation unit 6, and a two-period drive unit 12 for driving the inverter unit 12 according to pulses output from the two- 3 And a switching driver 11 for controlling on / off operations of the switching elements S1 and S2 of the switching elements S1 and S2.

The operation and effect of the present invention will be described in detail as follows.

When the commercial power is input through the power input terminal, the rectified current is rectified by the rectifier 1 and outputted using the bridge diode.

The pulsating DC voltage is smoothed again by the smoothing unit 2 composed of the inductance L2 and the capacitor C4 and the smoothed DC voltage is output to the inverter unit 3.

At this time, when the user puts the heating container on and turns on the start key, the control unit 8 recognizes it, selects the container detection frequency, and outputs it to the dead time control unit 5 (S21).

The dead time adjusting unit 5 sets a dead time for preventing the switching elements S1 and S2 of the inverter unit 3 from being turned on at the same time and outputs a pulse corresponding to the set dead time to the switching oscillating unit 6 .

At this time, the first and second load selection relays RY1 and RY2 of the heating unit 4 are turned on (S22) and the third load selection relay RY3 is turned off (S23)

Then, the working coils L1 and L2 and the resonance capacitors C2 and C3 form a resonance tank.

At this time, the control unit 8 reads the input current flowing from the input current detection unit 16 through the input transformer 9 (S24), and also reads the current flowing from the high frequency current detection unit 7 Is read through the high-frequency transformer 10 (S25)

The two input currents and the high-frequency currents thus read are compared with reference values, respectively, and the comparison differences A and B are obtained (S26)

If the comparison difference A obtained by comparing the input current with the reference value is 1.2 V or more and the comparison difference B obtained by comparing the high frequency current value with the reference value is between 1.7 and 2.2 V, If the comparison difference is between A = 0.7 to 1.0 V and B = 1.5 V or less, it is determined to be a magnetic container (S28).

When it is judged that the container is a 304 pure vessel or a magnetic vessel, it operates in the magnetic heating mode (S29).

In the magnetic heating mode, the first and second load selection relays RY1 and RY2 are turned on and the third load selection relay RY3 is turned off as shown in the heating mode classification table of FIG. 6 .

Then, the inductance La is divided by the working coil L1.L2 formed by the parallel connection into La = L1 , The capacitor Ca is Ca = C2 + C3, and the frequency ( f _a ) .

Then, if the comparison difference is A = 0.6 V or less and B = 2.3 V or more, it is determined to be non-magnetic (S30), and the non-magnetic heating mode is performed.

In the non-magnetic heating mode, the first and second relays RY1 and RY2 are turned off and the third load selection relay RY3 is turned on, as shown in the heating mode classification table of Fig. 6 do.

Then, the inductance La becomes La = L1 + L2, and the capacitor Ca becomes , And the frequency ( f _b ) .

Hereinafter, the operation of the two-period drive unit 12 and the switching drive unit 11 for driving the switching elements of the inverter unit 3 will be described.

The distribution of the current voltage according to the container is shown in FIG. 7.

When the control unit 8 determines the heating mode and outputs the control signal in accordance with the determined mode, the switching elements S1 and S2 of the inverter unit 3 are simultaneously turned on or off in the dead time adjusting unit 5 A dead time for preventing operation is set, and a pulse corresponding to the set dead time is output to the switching oscillation section 6.

Then, the switching oscillation unit 6 outputs the switching control signal having the dead time set to the two-period drive unit 12 through the points a and b, respectively.

Thus, the clock input terminal Cp of the D flip-flop 12c of the two-period drive unit 12 receives a pulse having a predetermined width when the pulse input from the point a is a rising edge, .

Then, the inverted and non-inverted output terminals of the D flip-flop 12c Are input to the AND gate 12b and the NOR gate 12a.

The NOR gate 12a is connected to the a-point waveform output from the switching oscillator 6 and the non-inverting terminal of the D flip-flop 12c Q And outputs the signal to the switching driver 11. In this case, the non-inverting terminal (D) of the D flip-flop 12c Q ) Outputs a low signal only when the output is low.

The AND gate 12b receives the b-point waveform output from the switching oscillation section 6 and the inverted terminal of the D flip-flop 12c And outputs the signal to the switching driver 11. The high signal is outputted only when the two signals are high.

As described above, when the signals generated by the NOR gate 12a and the end gate 12b of the two-period drive unit 12 are output to the switching driver 11, the switching driver 11 switches the inverter unit 3 5A as the gate of the device S1 and outputs the waveforms as shown in FIG. 5B to the gate of the switching device S2.

When the switching elements S1 and S2 are turned on or off by such a waveform, the two-period resonance waveform of the switching element S1 is as shown in Fig. 5 (c).

As a result, it can be seen that the gate waveform applied to the switching elements S1 and S2 is applied with the ON signal having the duty of 75% and 25%, respectively, so that the load resonance is doubled.

By the above-described operation, both the magnetic and non-magnetic heaters are used for heating.

Accordingly, the present invention provides a two-period drive unit between the switching oscillation unit and the switching drive unit to apply ON signals having duty ratios of 75% and 25% to drive the two switching devices driving the resonance tank of the heating unit, The container is judged by using all of the use area of the working coil and heating is carried out so that it can be safely used without restriction according to the position of the container placed. By switching at a high frequency using a general-purpose switching device, .

Claims (2)

An induction heating cooker comprising a rectifying section for rectifying an input AC power source, a working coil for heating the cooking vessel, a resonance capacitor for flowing a resonance current to the working coil, and a heating section, A dead time adjusting unit for preventing the switching device from being turned on or off at the same time, and a switching oscillating unit for outputting a switching control signal with a controlled dead time, A two-period drive unit for realizing a load resonance of a double cycle in driving the switching unit in accordance with a switching control signal output from the switching oscillation unit; and a switching unit for switching the switching unit of the inverter unit to an alternating operation And a switching driver for controlling the resonance tank of the heating unit Induction heating cooker for both magnetic and non-magnetic cooking. The driving circuit according to claim 1, wherein the two-period driver comprises: a D flip-flop which receives a signal output from the switching oscillation unit and receives a clock pulse input terminal and outputs a pulse having a predetermined width as an inverted or non- A Noah gate for outputting a switching control signal which is output from the switching oscillation unit and is noise-ringed between a signal applied to the clock pulse input terminal of the D flip-flop and a signal output through the non-inverted output terminal of the D flip- And a NAND gate for outputting a switching control signal obtained by ANDing another output signal and a signal output through an inverting output terminal of the D flip-flop.