KR19990048637A - Induction heating cooker with both magnetic and non-magnetic soft switching - Google Patents

Abstract

The present invention relates to a large-output soft-switching magnetic induction heating cooker for both magnetic and non-magnetic induction heating. In the prior art, a resonant capacitor is expensive and an excessive voltage of several thousand volts is applied to a resonant capacitor, There is a problem that many difficulties are followed. Therefore, the present invention is characterized in that first and second filter capacitors Cf1 and Cf2 connected in series for improving the power factor of a voltage input through the bridge diode BD, antiparallel diodes D1, D2, D3 and D4, (Lr1, Lr2, Cr1) connected in parallel to the center point of each of the two switching elements (S1, S2, S3, S4) connected in series with the first and second switching elements (C1, C2, C3, C4) And a load selection relay Ry connected between the center point of the two filter capacitors Cf1 and Cf2 and the resonance tank for selecting an operating frequency so that a large output can be generated according to magnetic and nonmagnetic parts.

Description

Induction heating cooker with both magnetic and non-magnetic soft switching

[0001] The present invention relates to an induction heating cooker having both soft magnetic and non-magnetic induction heating for reducing cost by using a general filter capacitor instead of a high-pressure resonance capacitor used in accordance with magnetic and non-magnetic loads, Output soft switching magnetic and non-magnetic induction heating cookers.

As shown in Fig. 1, the circuit configuration of a conventional magnetic and non-magnetic induction heating cooker includes a rectifying unit 10 for rectifying an input commercial power source AC to a DC voltage using a bridge diode; LC filters (L _f and C _f ) that receive DC voltage rectified through the rectifying part (10) and filter and smoothen to improve the power factor; First and second switching devices S1 and S2 connected in series between a positive power source terminal and a negative power source terminal for switching according to a control signal to provide a resonance voltage; And is connected to a common connection point of the first and second switching elements S1 and S2 to induce an eddy current in the cooking vessel by the resonance voltage supplied from the rectifying part 10 to heat the food in the cooking vessel A working coil L _r1 (L _r2 ); A resonance capacitor C _r1 connected to the working coil L _r2 to change the frequency depending on the vessel; The positive power supply terminal and the negative power supply and the working coil (L1) (L2) and a resonance capacitor (C _r21) (C _r22) being contiguous with the resonant state by a direct current voltage that is connected in series between the input to the terminal; And is connected between the connection point of the working coil L _r1 (L _r2 ) and the connection point of the resonance capacitor (C _r21 ) (C _r22 ) so as to operate only one working coil or both of the working coils And a load selection relay Ry.

A detailed description will be made of the conventional technology thus configured.

In the past, only ferrous iron bodies, which are mainly ferromagnetic, have been heated, but in recent years, researches on induction heating cookers capable of heating non-magnetic aluminum containers have been actively conducted.

Generally, it is well known to increase the number of turns of the working coil and to increase the operating frequency as compared to the iron-based vessel to heat the non-magnetic vessel. Therefore, to heat both magnetic and non-magnetic containers, the circuit constant must be changed according to each container.

Therefore, by turning on the city magnetic load load selection relay (Ry) L _r1, C _r21, C _r22 is to form a resonant tank, and to operate in a half bridge, turning off the non-magnetic load-load selection relay (Ry) L _r , C _r1 , C _r21 , and C _r22 form resonance tanks to operate as another half bridge.

First, the non-magnetic load operation will be described as follows.

The resonance tanks L _r and C _r1 , C _r21 , and C _r22 are turned off because the non-magnetic load load selection relay Ry is turned off, the second switching device S 2 is turned off and the first switching device S 1 is turned on, The rectified and filtered DC voltage V _d is applied through the rectifying part 10 and the LC filters L _f and C _f and the resonance starts so that the current rises in the working coil L _r .

When the first switching device S1 is turned off before the resonance half period passes, the auxiliary capacitors C _{a1 and} C _a2 of the first switching device S1 perform the auxiliary resonance with the resonance tank so that the voltage of the auxiliary capacitor C _a2 becomes The voltage at V _d drops to zero while the voltage at the auxiliary capacitor (C _a1 ) rises from zero to V _d .

Soon after, a second anti-parallel diode (D _a2) of the switching element (S2) is conductive in the applied voltage is zero resonant tank (L _r and _{C r1, C r21, C r22} ).

Then, resonance occurs continuously by the voltage charged in the resonance capacitor, and the second switching device S1 is turned on under the zero voltage condition.

The resonance current is reduced to zero by the subsequent resonance, and the resonance current is increased by the resonance in the opposite direction at this time.

The auxiliary capacitors C _{a1 and} C _{a2 perform} auxiliary resonance with the resonance tanks L _r and C _r1 and C _r21 and C _r22 to turn off the auxiliary capacitor C _a1 ) Drops from V _d to zero while the voltage on the auxiliary capacitor (C _a2 ) rises from zero to V _{d .}

Since the first switching element (S1) antiparallel diode (D _a1) is in conduction the voltage V _d is applied to the resonant tank (L _r and _{C r1, C r21, C r22} ).

Then, the resonance continues, and at this time, the first switching device S1 is turned on under the zero voltage condition.

If the resonance current falls to zero due to the continued resonance, the operation is terminated and the same operation is repeated.

The load is heated by the eddy current generated in the load by the induced current.

In the case of the magnetic load, the load selection relay Ry is turned on and the operation is the same as the above operation. The only difference is that the resonance tanks are made of L _r1 , C _r21 , and C _{r22 .}

As described above, the load selection relay Ry is turned on or off so that the number of turns of the working coil can be varied to heat both the magnetic and non-magnetic employees.

However, in the conventional technology as described above, the cost of the resonant capacitor is high, and an excess voltage of several thousand volts is applied to the resonant capacitor, so that noise is easily generated in the peripheral circuit operation.

Accordingly, it is an object of the present invention to provide an induction heating cooker for both soft magnetic and non-magnetic induction heating.

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

FIG. 2 is a circuit diagram of the induction heating cooker for both soft magnetic and non-magnetic soft switching.

FIG. 3 is a magnetic and non-magnetic mode classification table showing the states of relays and switching elements in FIG. 2; FIG.

Fig. 4 is a switching state and current waveform diagram according to the driving of the working coil Lr1 in the magnetic mode in Fig. 2. Fig.

FIG. 5 is a switching state and a current waveform diagram according to the driving of the working coil Lr1 in the non-magnetic mode in FIG.

DESCRIPTION OF THE REFERENCE SYMBOLS

BD: bridge diode Cf1, Cf2: filter capacitor

Lr1, Lr2: Working coil

Ry: Load selection relay S1 to S4: Switching element

C1 to C4: Resonant capacitors

According to an aspect of the present invention, there is provided a method for driving a switching regulator including a first and a second filter capacitors connected in series for dividing a voltage input through a bridge diode into two, And a load selection relay connected between the resonance tank and a center point of the first and second filter capacitors to select an operation frequency.

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

FIG. 2 is a circuit diagram of the induction heating cooker for both soft magnetic and non-magnetic soft switching of the present invention. As shown in FIG. 2, the first, Two switching elements S1, S2 and S3 connected in series with second filter capacitors Cf1 and Cf2 and antiparallel diodes D1, D2, D3 and D4 and capacitors C1, C2, C3 and C4, And resonance tanks Lr1, Lr2 and Cr1 connected in parallel to the center points of the first and second filter capacitors Cf1 and Cf2 and a resonance tank connected between the center points of the first and second filter capacitors Cf1 and Cf2 and the resonance tank, And a selection relay Ry.

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

3, the relay Ry is turned on in the magnetic mode and the switching elements S3 and S4 are made in the alternate operation of the switching elements S1 and S2 in the off state, The relay Ry is turned off so that the switching elements S1 and S4 are connected in pairs or S2 and S3 are alternately operated in pairs so that the working coils Lr1 and Lr2 and the resonant capacitor Cr1 form a resonant tank .

As shown in FIG. 4A, in the magnetic mode, when the third and fourth switching elements S3 and S4 are off, the second switching element S2 is turned off, When the first switching element S1 is turned on, half of the input voltage Vd / 2 is applied to the working coil Lr1 and the current i _Lr1 ) Rises linearly as shown in Fig. 4 (b).

When the magnitude of the current reaches a predetermined value, the first switching device S1 is turned off under the zero voltage condition.

Then, the voltage of the auxiliary capacitor C2 drops from Vd to zero.

When the voltage of the auxiliary capacitor C2 becomes zero, the antiparallel diode D2 of the second switching device S2 is turned on, and the current of the working coil Lr1 linearly decreases.

At this time, the second switching element S2 is turned on under the condition of zero voltage.

The current of the working coil Lr1 falls to zero as shown in FIG. 4 (b), and then increases in the opposite direction.

When the current reaches the set value, the second switching device S2 is turned off under the zero voltage condition.

Then, the voltage of the auxiliary resonant capacitor C1 decreases from Vd to zero.

When the voltage of the auxiliary capacitor C1 of the first switching device S1 becomes 0, the antiparallel diode D1 of the first switching device S1 is turned on and the current of the working coil Lr1 linearly increases do.

When this current becomes zero, one cycle of operation ends and the same operation repeats.

In the non-magnetic mode, after the load selection relay Ry is turned off, the second switching device S2 and the third switching device S3 are turned off, and the remaining first switching device S1 and the fourth switching device (S4) are simultaneously turned on.

Then, the input voltage Vd is applied to the resonance tank L (= Lr1 + Lr2) and Cr1, and the resonance starts and the current of the working coil L rises as shown in FIG. 5 (b).

When the first switching device S1 and the fourth switching device S4 are turned off before the resonance half period passes, C1, C2, C3, C4, L, and Cr1 perform auxiliary resonance and the voltages of C2 and C3 drop from Vd to zero , While the voltages of C1 and C4 rise from zero to Vd.

The antiparallel diodes D2 and D3 of the second and third switching elements S2 and S3 are turned on and the input voltage Vd is applied to the resonance tanks L and Cr1 inversely.

Then, resonance occurs continuously by the input voltage Vd and the voltage charged in the resonant capacitor, and the second and third switching elements S2 and S3 are turned on under the zero voltage condition.

The resonance current is reduced to zero by the subsequent resonance, and the resonance current is increased by the resonance in the opposite direction at this time.

When the second and third switching elements S2 and S3 are turned off before the resonance half period passes, C1, C2, C3, C4, L, and Cr1 perform auxiliary resonance again so that the voltages of C1 and C4 drop from Vd to zero, The voltage between C2 and C3 rises from zero to Vd.

Then, the anti-parallel diodes D1 and D4 of the first and fourth switching elements S1 and S4 are turned on, and the input voltage Vd is applied to the resonance tanks L and Cr1.

Then, the resonance continues, and the first and fourth switching elements S1 and S4 are turned on under the zero voltage condition.

When the resonance current drops to zero due to the continued resonance, the operation of one cycle is ended and the same operation is repeated.

An AC magnetic flux is generated in accordance with the magnitude and frequency of the induced current, and an eddy current is generated in the load by the magnetic flux.

Joule heat due to the eddy current is generated, and the heat directly heats the load container.

Therefore, the present invention has an effect of outputting large power according to the magnetic and non-magnetic loads

have.

Claims (1)

D2, D3 and D4 and capacitors C1 and C2 (Cf1 and Cf2) connected in series for improving the power factor of the voltage inputted through the bridge diode BD, Resonance tanks Lr1, Lr2, and Cr1 connected in parallel to a center point of each of two switching elements S1, S2, S3, and S4 connected in series with the first and second filter capacitors C3, C4, And a load selection relay (Ry) connected between a center point of the resonance tank (Cf1, Cf2) and the resonance tank for selecting an operating frequency.