KR19980058220A - Switching circuit of electromagnetic induction cooker - Google Patents

Abstract

The present invention relates to a switching circuit of an electromagnetic induction cooker, and more particularly, to reduce the manufacturing cost by eliminating the relay for selecting the heating mode and configuring the resonant tank by the switching control signal. In the present invention, the inverter unit 270 generates a resonance voltage by switching the DC voltage of the rectifying smoothing means according to the switching control signals Y1 to Y3, and an eddy current is applied to the heating plate by the resonance voltage of the inverter unit 270. A heating unit 28 for inducing and heating, a dead time adjusting unit 220 for calculating a dead time of the switching elements S1 to S3 by calculating an output pulse of the timer 210, a heating mode determination signal, A switching oscillator 230 for outputting pulses X1 and X2 for alternating operation of the switching elements S1 to S3 of the inverter unit 270 by inputting the output pulses of the dead time controller 220; A switching driver 240 for outputting switching control signals Y1 to Y3 to the inverter unit 270 by inputting the output signals X1 and X2 of the switching oscillator 230 and a magnetic load or a nonmagnetic load. The control unit 290 for outputting a control signal in accordance with the discrimination; Constitute the heating mode determination unit 300 and outputting a heating signal to the switching mode determining oscillation 230 by the force signal.

Description

Switching circuit of electromagnetic induction cooker

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction cooker, and more particularly, to a switching circuit of a magnetic / nonmagnetic combined electromagnetic induction cooker which performs a heating operation in a combination of magnetic and nonmagnetic.

1 is a configuration diagram of the prior art, as shown therein, a rectifier 150 for rectifying and outputting an input commercial power AC to a pulsating DC voltage and a pulsating DC voltage rectified through the rectifying unit 150. Two switching elements (S1) (S2) having a smoothing unit (160) for smoothing a constant DC voltage and an anti-parallel diode configured in series with the switching control signal for the DC voltage smoothed through the smoothing unit (160). Switching coil to generate a resonant voltage and a working coil Lr1 for inducing eddy currents to heat the heating plate to be heated by an electromagnetic induction effect caused by the magnetic field generated by the resonant voltage of the inverter unit 170. And a load selection relay RY for selecting whether to connect the working coils Lr1 and Lr2 for the configuration of the resonant tank according to the material of the heating container, the heating unit 180 formed of Lr2, and a predetermined width. Having pulses The dead time control unit 120 for preventing the on / off at the same time during the switching element switching operation by using the timer 110, which is an external oscillator, and the pulses generated by the timer 110, and the dead time adjustment Switching oscillator 130 to perform ZVC (Zero Voltage Switching) to oscillate the switching element by using the pulse provided from the unit 120, and the output of the switching oscillator 130 as an input to the inverter unit ( And a switching driver 140 for supplying switching control signals Y1 and Y2 to the switching elements S1 and S2 of 170.

The heating unit 180 constitutes a resonant tank using the working coils Lr1 and Lr2 and the condensers C1, C2 and C3 when the load selection relay RY is turned off for the magnetic load operation. When the load selection relay RY is turned on, the resonant tank is constituted by the working coil Lr1 and the capacitors C2 and C3.

Referring to the operation of the conventional circuit as follows.

When the cooking operation is started to generate a pulse having a predetermined width in the timer 110, the dead time controller 120 simultaneously turns on or off the switching operation of the switching elements S1 and S2 of the inverter 160. To prevent this, the dead time is set so that the switching waveforms can be switched in the zero point without overlapping each other during the alternating operation.

When the dead time adjuster 120 adjusts the dead time, the switching oscillator 130 performs a logic operation to switch the pulses X1 and X2 to alternately operate the switching elements S1 and S2 of the inverter 160. Output to 240.

At this time, when the rectifier 150 rectifies the commercial power (AC) and outputs a DC voltage, the smoothing unit 160 supplies the DC voltage Vd to the switching unit 170 by LC filtering and smoothing.

The switching driver 140 receives the switching control signals Y1 and Y2 as inputs of the pulses X1 and X2 generated from the switching oscillator 130, and thus, the switching elements S1 and S2 of the switching unit 170. Each of them is applied to the gates to switch to an alternate operation.

If the container for heating is a magnetic load, the relay RY is kept off so that the heating unit 180 constitutes a resonant tank with working coils Lr = Lr1 + Lr2 and condensers C1, C2, and C3. do. At this time, when the switching element S2 is turned off in the inverter unit 170 and the switching element S1 is turned on by the switching control signals Y1 and Y2 of the switching driver 140, the resonant tanks Lr, C1 to C3. ), The input voltage Vd is applied, the resonance starts, the current of the wicking coil Lr rises, and the resonance capacitor C1 is charged by the resonance current.

Then, if the switching device (S1) is turned off before the resonant half cycle passes, the capacitors C4 and C5 perform secondary resonance with the resonant tank so that the voltage of the capacitor C5 drops from 'Vd' to '0' and the capacitor C4 therebetween. ) Rises from '0' to 'Vd'.

Thereafter, since the anti-parallel diode D2 of the switching element S2 is conducted and zero voltage is applied to the resonant tank, resonance continues by the voltage charged in the resonant capacitor C1 and the resonance current increases due to the resonance in the opposite direction. do.

Then, if the switching element S2 is turned off before the resonant half cycle passes, the capacitors C4 and C5 resonate with the resonant tank so that the voltage of the capacitor C4 falls from 'Vd' to '0' and the capacitor C5 therebetween. The voltage at rises from '0' to 'Vd'.

Thereafter, since the anti-parallel diode D1 of the switching element S1 is turned on, a voltage Vd is applied to the resonant tank so that resonance occurs continuously. At this time, the switching element S1 is turned on under the condition of zero voltage.

Accordingly, when the resonance current drops to '0' due to the continuous resonance, one cycle of operation is terminated, and then the same operation is repeatedly performed.

Accordingly, the magnetic field is generated in the working coil Lr of the heating unit 180 by the current induced by the above operation, thereby generating the eddy current in the load, which is a magnetic material container, to perform the heating operation of the load.

In this case, the resonant current alternately flows to the switching elements S1 and S2. The pulse Y1 applied to the gate of the switching element S1 is the same as that of FIG. 3 (a) and is applied to the gate of the switching element S2. When the applied pulse Y2 is the same as that of FIG. 3B, the switching current waveform flowing through the switching element S1 is the same as that of FIG. 3C.

Here, referring to the waveform diagrams of FIGS. 3A and 3B, it can be seen that a ZVS section exists to prevent the switching devices S11 and S13 from being turned on or off at the same time.

On the other hand, due to the low resistance value and permeability by the material of the container itself to heat the nonmagnetic container such as aluminum, switching must be performed at a high frequency in order to perform induction heating.

Therefore, by turning on the load selection relay RY to form a resonant tank with the coil L1 and the condensers C2 and C3, the vessel is heated in the same process as the above magnetic load operation.

The vessel heating mode for heating the magnetic or nonmagnetic vessel in the above operation is as shown in the table of FIG. 2, and it can be seen that the inductance, capacitance, and frequency are different according to each mode.

However, this conventional technology has a problem in that the manufacturing cost increases because the excessive voltage of the thousands of V is applied to the relay during the nonmagnetic load operation and the withstand voltage of the resonant capacitor C1 must also satisfy the thousands of V.

The present invention has been made in an effort to provide a switching circuit of an electromagnetic induction cooker designed to reduce manufacturing costs by eliminating a relay for selecting a heating mode and configuring a resonant tank by a switching control signal in order to improve the disadvantage of the prior art. have.

1 is a circuit diagram of a prior art.

Figure 2 is a table showing the characteristics of the heating mode in Figure 1;

3 is a waveform diagram of a switching element driving voltage and current in FIG. 1;

4 is a circuit diagram according to the present invention.

FIG. 5 is a circuit diagram of the switching oscillator in FIG. 4; FIG.

6 is a timing diagram in FIG. 4;

7 is a waveform diagram of switching driving voltage and current according to a heating mode.

Explanation of symbols for the main parts of the drawings

210: timer 220: dead time control unit

230: switching oscillation unit 240: switching driving unit

250: rectifying part 260: smoothing part

270: inverter unit 280: heating unit

290: control unit 300: heating mode determination unit

The present invention provides a rectifying smoothing means for rectifying and smoothing a commercial power supply with a pulsating DC voltage to output a constant DC voltage, and the DC voltage of the rectifying smoothing means according to the switching control signals Y1 to Y3. An inverter means for switching to generate a resonant voltage, a heating means for inducing an eddy current to heat the heating plate to be heated by the electromagnetic induction effect of the magnetic field generated by the resonance voltage of the inverter means, and generating a pulse having a constant width A timer as an external oscillator, dead time adjusting means for calculating an output pulse of the timer and adjusting dead time of the switching operation of the inverter means, a heating mode determination signal and an output pulse of the dead time adjusting means as inputs; Switching oscillating means for outputting pulses X1 and X2 for alternating switching operations of the inverter means; Switching drive means for outputting the switching control signals Y1 to Y3 to the inverter means by inputting the output signals X1 (X2) of the switching oscillation means, and control for discriminating the magnetic load or the nonmagnetic load and outputting a control signal. Means and a heating mode determination means for outputting a heating mode determination signal to the switching oscillation means by the output signal of the control means.

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

According to an embodiment of the present invention, as shown in the circuit diagram of FIG. 4, the rectifying unit 250 rectifies and outputs the input commercial power AC with a pulsating DC voltage, and the pulsating rectified through the rectifying unit 250. A smoothing unit 260 which smoothes the DC voltage to make a constant DC voltage and three anti-parallel diodes having the DC voltage smoothed through the smoothing unit 260 in series according to the switching control signals Y1 to Y3. An eddy current is induced to the inverter unit 270 for switching the switching elements S1 to S3 to generate a resonance voltage, and a heating plate to be heated by an electromagnetic induction effect caused by the magnetic field generated by the resonance voltage of the inverter unit 270. A switching element using a heating unit 280 consisting of working coils Lr1 and Lr2 for heating, a timer 210 which is an external oscillator for generating a pulse having a constant width, and a pulse generated by the timer 210. Dynamic during alternating movement Oscillating the switching elements S1 to S3 by inputting a dead time adjustment unit 220 to prevent on / off at the time, a heating mode determination signal, and an output pulse from the dead time adjustment unit 220. Switching oscillator 230 for outputting pulses (X1) (X2) to perform zero voltage switching (ZVC) for the input, and the inverter unit 270 as an input of the output signal (X1) (X2) of the switching oscillator 230 A switching driver 240 for supplying the switching control signals Y1 to Y3 to the switching elements S1 to S3 of the control element and outputting a heating mode determination signal to the switching oscillator 230 under the control of the controller 290. The heating mode determination unit 300 is configured.

The dead time controller 220 receives the output signal of the timer 210 through the condenser C1 to the non-inverting input terminal and applies the divided voltage of the voltage Vcc by the resistors R2 and R3 to the inverting terminal. An operational amplifier OP1 for receiving and amplifying operation, and an operational amplifier OP2 for performing operational amplification on the divided signal of the output signal of the operational amplifier OP1 and the voltage Vcc by the resistors R5 and R6.

The switching oscillator 230 generates a inverted output signal at the rising edges of the NOR gates NR1 and NR2 that sequentially output the output signal of the dead time controller 220 and the NOR gate NR2. A deflip-flop DF to latch, a noah gate NR3 for noarizing the non-inverted output signal of the de-flip-flop DF, and an output signal of the noah gate NR2, and the output of the noah gate NR3. Inverter IN3 (IN4) for sequentially inverting the signal and outputting the switching control signal Y2, and a noah gate for noringing the inverted output signal of the flip-flop DF and the output signal of the noah gate NR2. (NR4), the inverter IN1 (IN2) for sequentially inverting the output signal of the NOR gate NR4 and outputting the switching control signal Y3, the output signal of the heating mode determining unit 300, and the Noah. Noah gate NR5 for noring the output signal of gate NR3, and this noah gate N Inverter IN5 outputs the switching control signal Y1 by inverting the output signal of R5).

The heating mode determination unit 300 is turned on to the high output signal of the control unit 290 in the magnetic mode to output a heating mode determination signal which is low, and in the non-magnetic mode to turn off the low output signal of the control unit 290. And a transistor Q1 for outputting a heating mode decision signal that is high.

The inverter unit 270 connects three switching elements S1 (S2) and S3 in which a reverse diode and capacitors D1 and Ca1, D2 and Ca2 and D3 and Ca3 are connected in parallel. The output signals Y1 to Y3 of the switching driver 240 are applied to the switching elements S1 to S3, respectively, and the working coil Lr of the heating unit 280 and the two are applied to the switching elements S1 and S2. The resonant capacitors Cr1 and Cr2 are connected in parallel.

Referring to the operation and effect of the embodiment of the present invention configured as described above are as follows.

When the timer 210 used as the external oscillator generates a pulse (a point waveform) having a predetermined width as shown in FIG. 6 (a), the capacitor C4 and the resistor R1 of the dead time controller 220 are generated. By differentiating and converting it into a pulse (b dot waveform) as shown in Fig. 6 (b), and the operational amplifier OP1 inputted to the non-inverting terminal (+) is a resistor R2 (R3) applied to the inverting terminal. The difference is obtained by comparing the reference voltage with the reference voltage) and the operational amplifier OP2 applies the reference voltage adjusted by the resistors R5 and R6 to the non-inverting terminal + at the inverting terminal (-). The difference is output to the switching oscillator 230 as a dead time adjustment signal in comparison with the output signal of OP1.

At this time, when the dead time adjuster 220 adjusts the dead time, the switching oscillator 230 sequentially outputs the NOR gates NR1 and NR2 to output a pulse (c dot waveform) as shown in FIG. The pulse at this point (c) is input to the clock pulse input terminal Cp of the flip-flop DF and the one input terminal of the noble gate NR3 and NR4, respectively.

Accordingly, the flip-flop DF latches the signal of its inverted output terminal Q fed back to its data input terminal D when the pulse inputted through its clock pulse input terminal Cp is rising edge, thereby outputting its output Q. )

At this time, the flip-flop DF latches a pulse (e-dot waveform) as shown in FIG. 6 (e) output through the inverted output terminal Q and transmits the pulse as shown in FIG. 6 (d) to the non-inverted output terminal Q. When the d point waveform is outputted, the noble gate NR3 outputs the pulse (f point waveform) as shown in Fig. 6 (f) by inputting the (c) point waveform and the (d) point waveform, respectively, and the noah gate NR4. ) Outputs a pulse (g point waveform) as shown in Fig. 6 (g) by inputting (c) point waveform and (e) point waveform, respectively.

If the heating mode determination unit 300 is a magnetic load, the transistor Q1 is turned off by the low output signal of the control unit 290, and the heating mode determination signal 300 is output to the switching oscillator 230. In the case of the active load operation, the transistor Q1 is turned on by the high output signal of the controller 290 to output the heating mode determination signal, which is low, to the switching oscillator 230.

Accordingly, in the case of the operation of the magnetic load, the switching oscillator 230 maintains the output state of the low signal as shown in FIG. 6 (k) by the NOR gate NR5 by the high output signal of the heating mode determination unit 300. The low signal is inverted through the inverter IN5 so that the switching control signal Y1 is kept high as shown in FIG. 6 (m), and the inverters IN3 and IN4 sequentially invert the output signal of the NOR gate NR3. By outputting the switching control signal Y2 as shown in FIG. 6 (i) and the inverter IN1 and IN2 sequentially inverting the output signal of the NOR gate NR4, thereby switching switching signal as shown in FIG. Will output (Y3).

That is, in the case of a magnetic load, the inverter unit 270 has the switching element S1 always on, and the two switching elements S2 and S3 and the working coils Lr1 and Lr2 of the heating unit 280 form a half bridge. do.

On the contrary, in the case of the operation of the nonmagnetic load, the switching oscillator 230 outputs the output signal of the heating mode determination unit 300 to low as shown in FIG. 6 (j), so that the NOR gate NR5 outputs the output signal of the NOR gate NR3. By outputting a pulse as shown in Fig. 6 (l) as an input, the inverter IN5 outputs the switching control signal Y1 as shown in Fig. 6 (n), and the inverter IN3 and IN4 output the output of the NOR gate NR3. By inverting the signal sequentially, the switching control signal Y2 as shown in FIG. 6 (i) is output, and the inverter IN1 (IN2) sequentially inverts the output signal of the NOR gate NR4. It outputs a switching control signal (Y3) as shown.

That is, if the non-magnetic load, the inverter unit 270 is configured to switch on and off the switching elements (S1, S2) at the same time and the switching element (S3) has the opposite switching state.

Accordingly, the switching driver 240 supplies the switching control signals Y1 to Y3 generated from the switching oscillator 230 to the switching elements S1 to S3 of the inverter unit 270 according to the determination of the magnetic load or the nonmagnetic load. To switch to alternate operation.

For example, the case of nonmagnetic load is described as follows.

First, when the switching elements S1 and S2 are turned off by the switching control signals Y1 to Y3 of the switching driver 240 and the switch S3 is turned on, the smoothing part 260 is provided in the resonant tanks Lr, Cr1 and Cr2. The input voltage Vd from is applied and resonance starts to increase the current of the coil Lr.

Subsequently, when the switching element S3 is turned off before the resonant half cycle passes, the capacitors Ca1 to Ca3 connected in parallel to the switching elements S1 to S3 are assisted with the resonant tanks Lr, Ca1, and Ca2 of the heating unit 280. By resonating, the voltages of the auxiliary resonant capacitors Ca1 and Ca2 drop from 'Vd' to '0' while the voltage of the auxiliary resonant capacitor Ca3 rises from '0' to 'Vd'.

Thereafter, the antiparallel diodes D1 and D2 of the switching elements S1 and S2 are turned on so that zero voltage is applied to the resonant tanks Lr, Ca1, and Ca2 of the heating unit 280, and thus the resonant capacitors Cr1 and Cr2. Resonance continuously occurs due to the charged voltage, and at this time, the switching elements S1 and S2 are turned on under the condition of zero voltage.

Accordingly, the resonance current drops to '0' due to the continuous resonance, and this time, the resonance current increases by resonance in the opposite direction.

Subsequently, when the switching elements S1 and S2 are turned off before the resonant half-cycle passes, the auxiliary resonant capacitors Ca1 to Ca3 auxiliary resonate with the resonant tanks Lr, Ca1 and Ca2, so that the voltage of the auxiliary resonant capacitor Ca3 is' The voltage of the auxiliary resonant capacitors Ca1 and Ca2 rises from '0' to 'Vd' while it drops from 'Vd' to '0'.

Thereafter, the anti-parallel diode D3 of the switching element S3 is turned on so that the voltage Vd from the smoothing portion 26 is applied to the resonant tanks Lr, Ca1, and Ca2.

Accordingly, resonance continues and at this time, the switching element S3 is turned on under the voltage condition of '0'.

Thereafter, when the resonance current drops to '0' due to the continuous resonance, one cycle of operation is terminated, and the above operation is repeatedly performed.

Therefore, the magnetic field is generated in the working coil Lr of the heating unit 280 by the current induced by the above operation, thereby generating the eddy current in the load, which is a magnetic material container, to perform the heating operation of the load.

On the other hand, heating the magnetic container performs the same operation as in the case of the non-magnetic load, but only the components of the resonant tank is different.

The timing of the switching driving voltages according to the magnetic heating mode and the nonmagnetic heating mode and the waveform of the current flowing through the working coil at this time are as shown in FIG.

As described in detail above, the present invention does not use an expensive heating mode selection relay, thereby reducing manufacturing costs and removing relay contact sounds when an on / off occurs.

Claims (5)

Rectification smoothing means for rectifying and smoothing commercial power (AC) with a pulsating DC voltage and outputting a constant DC voltage, and switching the DC voltage of the rectifying smoothing means in accordance with switching control signals Y1 to Y3 to generate a resonance voltage. An inverter means, a heating means for inducing an eddy current to heat the heating plate to be heated by the electromagnetic induction effect caused by the magnetic field generated by the resonance voltage of the inverter means, a timer which is an external oscillator for generating a pulse having a constant width, Dead time adjusting means for calculating the dead time of the switching operation of the inverter means by calculating an output pulse of the timer, and alternating switching operation of the inverter means by inputting a heating mode determination signal and an output pulse of the dead time adjusting means. Switching oscillation means for outputting a pulse X1 (X2) for outputting; and an output signal X1 (X2) of the switching oscillation means. Switching drive means for outputting switching control signals Y1 to Y3 to the inverter means as input, control means for discriminating a magnetic load or a non-magnetic load and outputting a control signal, and a heating mode by the output signal of this control means And a heating mode determining means for outputting a determination signal to said switching oscillating means. 2. The switching oscillation means according to claim 1, wherein the switching oscillation means alternately switches the switching control signals Y2 and Y3 when the output signal of the heating mode determining means is high, thereby switching the heating control mode determining means. The switching circuit of the electromagnetic induction cooker, wherein the switching control signal (Y1) (Y2) is turned on and off at the same time and the switching control signal (Y3) is turned on and off in reverse when the output signal is low. 3. The switching oscillation means according to claim 1 or 2, wherein the switching oscillation means comprises a NOR gate (NR1) NR2 for sequentially nulling the output signal of the dead time adjusting means and at the rising edge of the output signal of the NOR gate NR2. A deflip-flop DF for latching an inverted output signal, a noah gate NR3 for noarizing the non-inverted output signal of the deflip-flop DF, and an output signal of the noah gate NR2, and the noah gate ( Inverter IN3 (IN4) for sequentially inverting the output signal of NR3 to output the switching control signal Y2, and the inverted output signal of the flip-flop DF and the output signal of the NOR gate NR2. Inverter IN1 (IN2) for ringing the NOR gate NR4, the output signal of the NOA gate NR4 and sequentially outputting the switching control signal Y3, and the output of the heating mode determination unit 300. Noah gate NR for noarizing a signal and an output signal of the noah gate NR3 5) and an inverter IN5 for inverting the output signal of the noah gate NR5 and outputting a switching control signal Y1. The method of claim 1, wherein the heating mode determining means is turned on to the high output signal of the control means in the magnetic mode to output a heating mode determination signal that is low, and to the low output signal of the control unit 290 in the nonmagnetic mode And a transistor (Q1) for outputting a heating mode determination signal which is high. 2. The inverter means according to claim 1, wherein the inverter means connects three switching elements S1 (S2) and S3 in which the reverse diode and the capacitors D1 and Ca1 (D2 and Ca2) (D3 and Ca3) are connected in parallel. The switching control signals Y1 to Y3 of the switching drive means are respectively applied to the switching elements S1 to S3, and the working coil and the resonant capacitors Lr1 and Cr1 (Lr2) of the heating means are applied to the switching elements S1 and S2. And Cr2) connected in parallel with each other, and the switching circuit of the electromagnetic induction cooker characterized by the above-mentioned.