KR19990011649A - Switching circuit of electronic 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. In the related art, an IGBT element cannot drive at 80 KHz for heating a nonmagnetic container. Since there is a problem to be used, the switching element is configured by operating in a pair of upper and lower, there is a problem such as causing damage if any one element is concentrated due to unbalance (unblance). Therefore, the present invention provides 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 control unit 109 for outputting a control signal for selecting a switching element according to the material of the cooking vessel, a heating mode determination unit 110 for outputting a switch selection signal according to the control signal output from the control unit 109, The switch is turned on or off according to the switch selection signal output from the heating mode determining unit 110 to output a pulse generated by the switching oscillator 103 and the switch of the analog switch 111. A switching waveform control unit 113 for outputting a pulse for driving the switching element according to a state, a delay unit 112 for adjusting the timing of a pulse required by the switching waveform control unit 113, and the switching waveform control unit 113 The switching driver 114 for alternately operating the switching element of the switching unit 108 using the pulse input from the) and the switching movement of the switching element of the switching unit 108 The LC resonator 106 for induction heating of the cooking vessel 107 can be made by induction heating as well as a magnetic container as well as a magnetic container by using a general-purpose IGBT element. It would be.

Description

Switching circuit of electronic 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 bridge diode; An LC filter unit 60 which 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) consisting of two switches having anti-parallel diodes configured in series with the DC voltage provided through the LC filter unit (60) and switching in accordance with 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) for heating the container 80 by inducing an eddy current to the heating plate to be heated by the electromagnetic induction effect by the magnetic field generated by the resonance voltage by 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 operational amplifier OP1 received as the non-inverting terminal (+) and the inverting terminal (-) is compared with two values to find an error, and the error is again output to the non-inverting terminal (+) of the operational amplifier (OP2). do.

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 this differentiation and outputting by performing arithmetic operation is to set the dead time so that the switching elements S1 and S2 can be switched in the zero state without being simultaneously turned on or off.

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.

The c point waveform is connected to the clock pulse input Cp of the flip-flop DF1 and to one input of another NOR gate NR3 and NR4, so that when the input pulse Cp rises, The pulse input to the data input terminal D of the DF1 is output to the output terminal Q, and the data input terminal D is an inverted output terminal. Enter the output of.

Therefore, the inverted output terminal of the flip-flop (DF1) 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 d and e points are the noahgate. Pulses (g dot waveforms) as shown in Fig. 2G, which are inputted at NR4, are respectively input.

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 the output signal is high, the switching elements S1 and S3 of the switching unit 70 operate to operate the switching oscillator 30. When the high point is output at the g-dot waveform of), the switching elements S2 and S4 of the switching unit 70 operate.

As described above, when the switching elements S1, S3, and S2, S4 alternately operate, the container 80 placed on the upper surface of the working coil L1 generates LC resonance by the working coil L1 and the resonant capacitor C1. ) And induction heating by applying an eddy current.

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

However, in the prior art as described above, the general-purpose IGBT element cannot be driven at 80 KHz for heating the nonmagnetic container, and is commercialized due to the use of an expensive MOS field effect transistor (MOS FET) having a high voltage and high current rating. Since the other cost burden is large, and the switching elements are operated in a pair of upper and lower, there is a problem such as causing damage when either element is concentrated due to unbalance (unblance).

Therefore, an object of the present invention for solving the problems as described above is to drive the switching element by using a universal IGBT element in order to be able to heat the nonmagnetic container at high frequency to reduce the cost burden due to commercialization The present invention provides a switching circuit and a control method of an electronic cooker.

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

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

3 is a block diagram of a switching circuit of the present invention.

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

5 is an operation process diagram for a switching control method of the present invention.

* Explanation of symbols for main parts of the drawings

101: timer 102: dead time control unit

103: switching oscillator 104: rectifier

105: smooth part 106: LC resonance part

107: cooking vessel 108: switching unit

109 control unit 110 heating mode determination unit

111: analog switch 112: delay unit

113: switching waveform controller 114: switching driver

The present invention for achieving the above object, the switching to adjust the pulse width to have a frequency for switching the switching element by using a pulse provided in the dead time control unit for preventing the switching device at the same time during the switching operation An oscillation unit; A control unit for outputting a control signal for selecting a switching element according to the material of the cooking vessel, a heating mode determination unit for outputting a switch selection signal according to the control signal output from the control unit, and a switch output from the heating mode determination unit An analog switch for outputting pulses generated by the switching oscillation unit by turning on or off the switch according to a selection signal, a switching waveform controller for outputting pulses for driving a switching element according to a switch state of the analog switch, and the switching waveform A delay unit for adjusting the timing of the pulse required by the control unit and a switching driver for induction heating by alternately operating the switching element of the switching unit by using the pulse input from the switching waveform control unit.

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 control unit 109 for outputting a control signal for selecting a switching element according to the material of the cooking vessel, a heating mode determination unit 110 for outputting a switch selection signal according to the control signal output from the control unit 109, The switch is turned on or off according to the switch selection signal output from the heating mode determining unit 110 to output a pulse generated by the switching oscillator 103 and the switch of the analog switch 111. A switching waveform control unit 113 for outputting a pulse for driving the switching element according to a state, a delay unit 112 for adjusting the timing of a pulse required by the switching waveform control unit 113, and the switching waveform control unit 113 The switching driver 114 for alternately operating the switching element of the switching unit 108 using the pulse input from the) and the switching movement of the switching element of the switching unit 108 It consists of the LC resonator 106 for induction heating the cooking vessel 107.

The switching waveform controller 113 outputs a pulse having a predetermined width to the non-inverting and inverting terminals when the switching element driving pulse input to the clock pulse input terminal Cp is a rising edge. And first to second switching pulses for driving the switching element by using the output pulse of the flip-flop DF2, the pulse input through the delay unit 112, and the pulse output from the switching oscillator 103. It consists of 4 end gates (AND1 ~ AND4).

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 is output. And are differentiated by the resistor R1 to form a pulse (b point waveform) as shown in 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.

As described above, the reason for performing the differential operation and the operation operation on the pulses input by the dead time adjusting unit 102 is that the switching elements S1 and S2 are not simultaneously turned on or off, and zero. The dead time is set so that each can be switched in the in state.

The pulse output from the dead time adjusting unit 102 generates and outputs a pulse (c dot waveform) as shown in FIG. 4C through the noar gates 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 DF1 and the noble gate NR3 and NR4, respectively.

When the pulse inputted to the clock pulse input terminal Cp of the flip-flop DF1 rises, the pulse inputted to the data input terminal D is outputted to the output terminal Q, where the data input terminal D is inverted. Output Is connected to and its output is input.

That is, when the pulse input to the clock pulse input terminal Cp of the flip-flop DF1 rises, the signal output through the output terminal Q has the same pulse (d dot waveform) as shown in FIG. Inverting output terminal is used as data input terminal (D). Pulse is inputted to the inverting output stage. The output pulse of is the same as the pulse (e point waveform) as shown in Fig. 4E having a phase opposite to that of the output terminal Q.

The noble gate NR3 receives the output pulse of the noble gate NR2 and the output pulse of the flip-flop DF1 (d dot waveform). A pulse is generated and output, and the noble gate NR4 receives the output pulse of the noble gate NR2 (c dot wave form) and the output pulse of the flip-flop DF1 (e dot wave form). To generate and output a pulse as shown in FIG.

Accordingly, the output pulses (f-dot waveforms) of the nodal gate NR3 of the switching oscillator 103 are input to the first and third switches SW1 and SW3 of the analog switch 111, respectively. The output pulse (g point waveform) is input to the second and fourth switches SW2 and SW4 of the analog switch 111, respectively.

The pulse input to the third switch SW3 is input to the clock pulse input terminal Cp of the flip-flop DF2 of the switching waveform controller 113.

Then, the deflip-flop DF2 has a pulse i point as shown in FIG. Waveform) and its inverting output terminal As shown in FIG. 4 (j) having an opposite phase to the output pulse of the non-inverting output terminal Q, a pulse (j point waveform) is output.

At the same time, the pulse (f-point waveform) passing through the third switch SW3 passes through the resistor R6, the reverse diode D8, and the condenser C9 of the delay unit 112, as shown in FIG. Output the same pulse (h point waveform).

Then, the first AND gate AND1 of the switching waveform controller 113 receives an output pulse (i-dot waveform) of the de-flip flop DF2 and an output pulse (h-dot waveform) of the delay unit 112, respectively. And outputs a ringed pulse, i.e., a pulse (k-dot waveform) as shown in FIG. 4 (k), and the second and gate AND2 outputs an output pulse (i-dot waveform) of the flip-flop DF2 and an analog switch ( The pulses (g-dot waveform) output through the fourth switch SW4 of 111 are respectively input and output, ie, pulses (l-dot waveform) as shown in (l) of FIG. 4.

Similarly, the third and gate AND3 of the switching waveform controller 113 receives an output pulse (j dot waveform) of the de-flip flop DF2 and an output pulse (h dot waveform) of the delay unit 112, respectively. A ring pulse, that is, a pulse (m dot waveform) as shown in (m) of FIG. 4, is output, and the fourth and gate AND4 output pulses (j dot waveform) of the flip-flop DF2 and an analog switch ( Pulses (g-dot waveforms) output through the fourth switch SW4 of 111 are input and output, that is, pulses (n-dot waveforms) as shown in FIG. 4 (n) are output.

The output pulse (k-dot waveform) of the first and gate AND1 is combined with the pulse (f-dot waveform) passing through the first switch SW1 of the analog switch 111 and passes through the resistor R16 to the switching driver 114. Is inputted to the H1 input terminal of the first pulse output unit 114a of the second pulse), and the output pulse of the second and gate AND2 passes through the second switch SW2 of the analog switch 111. (g point waveform) is input to the L1 input terminal of the first pulse output section 114a via a resistor R17.

The output pulse (m-dot waveform) of the third and gate AND3 is input to the H2 input terminal of the second pulse output unit 114b of the switching driver 114 through the resistor R18, and the fourth end. The output pulse (n point waveform) of the gate AND4 is input to the L2 input terminal of the second pulse output unit 114b through the resistor R19.

At this time, the input power (ac) is rectified in the rectifying unit 104, the DC voltage smoothed in the smoothing unit 105 is supplied to the switching unit 108 and the LC resonator unit 106 to the cooking vessel 107 When placed on the working coils L1 and L2 that are the heating plates, the material of the container is detected through the current detector and the container material detecting unit, which are not shown, and then output to the controller 109.

For example, if the cooking vessel 107 placed on the working coils L1 and L2 is a magnetic container, the controller 109 outputs a low level control signal to its A output terminal and a high level control signal to the B output terminal. do.

If the cooking vessel 107 placed on the working coils L1 and L2 is a nonmagnetic container, the controller 109 outputs a high level control signal to the A output terminal and a low level control signal to the B output terminal. do.

For example, when the container placed on the heating plate is a nonmagnetic container, the relay switch RY1 is turned off so that the working coils L1 and L2 and the resonant capacitors C1, C2 and C3 resonate with LC.

At this time, when the control unit 109 outputs a high level control signal to the A output terminal and a low level control signal to the B output terminal, the transistor Q1 of the heating mode determination unit 110 is turned on and the transistor ( Q2) is turned off.

When the transistor Q1 is turned on, the power supply voltage VDD is bypassed to the ground side through the resistor R11 and the transistor Q1, so the point A 'becomes low level.

Since the low level at the point A 'is inverted through the inverters I1 and I2 to become a high level, the first and second transfer gates T1 and T2 are respectively cut off, so that the switching oscillator 103 f, g point pulses are not transmitted.

At this time, since the transistor Q2 is turned off, the high level power supply voltage VDD passing through the resistor R14 is applied to the point B ', and the high level at the point B' causes the inverters I3 and I4 to turn off. The third and fourth transfer gates T3 and T4 are in a conductive state because they are inverted to become a low level.

Then, the pulses output through the de-flop DF2 and the AND gates AND1 to AND4 of the delay unit 112 and the switching waveform control unit 113 are first and second pulse output units 114a of the switching driver 114. 4) and outputs the pulse as shown in (k ~ n) of FIG. 4 to drive the switching element of the switching unit 108 in the order of S1 → S3 → S2 → S4 to resonate with the working coils L1 and L2. LC resonance by the capacitors C1, C2, and C3 induces eddy currents in the nonmagnetic container to induction heating

When the container on the heating plate is a magnetic container, the relay switch RY1 is turned on so that the working coil L1 and the resonant capacitors C2 and C3 resonate with LC.

At this time, if the control unit 109 outputs a low level control signal to the A output terminal and a high level control signal to the B output terminal, the transistor Q1 of the heating mode determination unit 110 is turned off and the transistor is turned off. Q2 is turned on.

When the transistor Q1 is turned off, the high level power supply voltage VDD through the resistor R11 is applied to the A 'point, and the A' point becomes the high level.

Since the high level at the point A 'is inverted through the inverters I1 and I2 to become a low level, the first and second transfer gates T1 and T2 are in a conductive state, respectively. The f and g point pulses are respectively transmitted to the H1 and L1 input terminals of the first pulse output unit 114a of the switching driver 114 through the resistors R16 and R17.

At this time, since the transistor Q2 is turned on, the high level power supply voltage VDD is bypassed to the ground side through the resistor R14 and the transistor Q2, so that the low level is applied to the B 'point, and the B' point is applied. Since the low level of is inverted through the inverters I3 and I4 to become a high level, the third and fourth transfer gates T3 and T4 are respectively in a blocking state.

Therefore, the delay unit 112 and the switching waveform control unit 113 do not operate. Accordingly, the pulse is not output to the second pulse output unit 114b of the switching driver 114.

The f, g point pulses transmitted through the first and second switches SW1 and SW2 of the analog switch 111 alternately operate the switching elements S1 and S3 of the switching unit 108 to operate the working coil ( LC induction by L1) and resonant capacitors (C2, C3) induces eddy currents in nonmagnetic containers to induction heating.

Looking at the operation so far with reference to the operation process of Figure 5 again, it is determined whether the container placed on the heating plate is a magnetic container or a non-magnetic container (S11).

If it is determined in step S1 that the magnetic container is a magnetic switch to turn on the relay switch (RY1) to output a low-level control signal only to the A output terminal of the control unit 109 (S12).

Accordingly, only the first and second switches SW1 and SW2 of the analog switch 111 are turned on to operate the S1 and S3 switching elements of the switching unit 108 alternately to operate the working coil L1 and the resonant capacitors C2 and C3. Induction heating is induced by eddy current in the magnetic container by LC resonance by (S13).

If it is determined in step S1 that the nonmagnetic container is used, the relay switch RY1 is turned off, and a low level control signal is output only to the B output terminal of the controller 109 (S14).

Accordingly, only the third and fourth switches SW3 and SW4 of the analog switch 111 are turned on, and the switching elements of the switching unit 108 are alternately operated from S1 → S3 → S2 → S4 to the working coils L1 and L2. Induction heating is conducted by inducing eddy currents in the nonmagnetic container by LC resonance by resonant capacitors C1, C2 and C3 (S5).

As described above, the present invention can not only heat the magnetic container using a general-purpose IGBT element, but also drive the switching element in order to heat the non-magnetic container at high frequency, thereby reducing the cost burden due to commercialization. There is.

Claims (3)

In an electronic cooker which makes a dead time by using a pulse output from a timer and alternately operates the switching device to obtain a constant power, a frequency for switching the switching device with respect to an output pulse of the dead time adjusting unit that produces the dead time. A switching oscillator for adjusting a pulse width to have; A heating mode determination unit outputting a switch selection signal according to a control signal of a control unit according to a material of a container, an analog switch outputting an output pulse of the switching oscillation unit according to a switch selection signal output from the heating mode determination unit, and A switching waveform controller for outputting a pulse for driving a switching element according to a switch state of an analog switch, a delay unit for adjusting a timing of a pulse required by the switching waveform controller, and a pulse input from the switching waveform controller And a switching driving unit configured to alternately operate the switching elements of the switching unit to induce heating. The flip-flop of claim 1, wherein the switching waveform controller outputs a pulse having a predetermined width to its non-inverting and inverting terminals when the switching element driving pulse input to the clock pulse input terminal is a rising edge; A switching circuit of an electronic cooker comprising: first to fourth end gates for generating a switching pulse for driving a switching device using an output pulse of a flop, a pulse input through a delay unit, and a pulse output from a switching oscillation unit. The switching circuit of an electronic cooker according to claim 1, wherein the delay unit comprises a reverse diode and a capacitor connected in parallel with a resistor.