TWI639361B - Induction cooker and control circuit and control method therefor - Google Patents

Abstract

An induction cooker and a control circuit and a control method therefor, wherein the control circuit includes a ramp signal generator for sampling a resonance peak voltage of the main circuit switch of the induction cooker through a resonance peak control circuit included in the ramp signal generator, and using the sampling The obtained resonance peak voltage generates a first compensation current, and generates a ramp signal by adding a first compensation current generated by the resonance peak control circuit to the constant current; the differential integration circuit, and the first reference voltage and the first voltage signal The voltage difference between the voltages is integrated to obtain a second voltage signal; the comparator compares the voltage of the third voltage signal as the ramp signal with the voltage of the second voltage signal to output the first control signal for control The main circuit switch of the induction cooker. The resonance voltage can be effectively controlled by the control circuit.

Description

Induction cooker and control circuit and control method therefor

The present invention relates to the field of household appliances, and more particularly to an induction cooker and a control circuit and control method for the same.

The induction cooker adopts the principle of magnetic field induced eddy current, which uses high-frequency current to pass through the toroidal coil, thereby generating numerous closed magnetic field forces, so that the body itself rapidly heats up, and then heats the food in the pot. When the high-frequency current is passed through the coil 1, a high-frequency alternating magnetic field is generated around the coil 1, and when the magnetic field line 3 passes through the bottom of the magnetic conductive material (such as the iron pot 2) under the action of the high-frequency alternating magnetic field, the iron The bottom of the pot 2 will produce numerous small eddies 4, and the bottom of the pot will quickly release a large amount of heat for heating purposes. The working diagram is shown in Figure 1.

Fig. 2 is a schematic view showing the main circuit of the prior art induction cooker operation, comprising a full-wave rectifier bridge, an LC filter, an electromagnetic coil MC, a capacitor C0 and a first switch W. Here, the first switch W is an insulated gate bipolar transistor (IGBT).

The input AC power is full-wave rectified after passing through the full-wave rectifier bridge, and then passes through the LC filter to form a sinusoidal half-wave voltage. The first switch W is continuously turned on and off. When the first switch W is turned on, the rectified input voltage Vin is applied across the electromagnetic coil MC, the electromagnetic coil MC flows through the forward current, and the first switch W is turned off. The coil MC forms a high-frequency resonance with the capacitor C0 connected in parallel, the voltage on the electromagnetic coil MC is reversed, the current flowing through the electromagnetic coil MC is reduced, and the change in the current flowing through the electromagnetic coil MC forms a high-frequency magnetic field. The alternating magnetic field lines generated by the high-frequency magnetic field pass through the pot and form a vortex in the iron pot to heat the pot. Therefore, the alternating magnetic lines of force have a decisive effect on the eddy current.

The following is an analysis of the working state of Figure 2 to see how the architecture of Figure 2 produces an alternating magnetic field.

Working state one: Fig. 3 shows the current flow of the operating circuit of the induction cooker when the first switch W is closed.

At this time, the first switch W is closed, and the on-time period of the first switch W is set to be the on-time Ton, and the rectified half-wave voltage forms a loop through the electromagnetic coil MC and the closed switch, and the electromagnetic coil MC is a linear inductor flowing through the electromagnetic coil. The current of the MC continues to increase.

In general, since the on-time Ton of the first switch W is small, the current flowing through the electromagnetic coil MC is approximately linearly increased, L. △ i _L = V _input sin θ . T _on (1) Equation (1), the current through the electromagnetic coil MC is △ i _L, θ is the phase angle of the input voltage, the peak Vinput input voltage Vin. Since the input voltage is a sinusoidal waveform voltage, Vinput‧sinθ is the input voltage value at different phase angles.

Available from formula (1),

Operation state 2: Fig. 4 shows the current flow of the resonance circuit constituted by the electromagnetic coil MC and the capacitor C0 in the induction cooker when the first switch W is turned off.

At this time, the first switch W is turned off, and the off period of the first switch W is set to the off time Toff. After the first switch W is turned off, the energy stored in the electromagnetic coil MC is transferred to the parallel resonant capacitor C0. An LC resonant circuit is formed.

The resonant frequency is: Where L is the inductance value of the electromagnetic coil MC, and C is the capacitance value of the resonance capacitor C0 in parallel with the electromagnetic coil MC.

When all the energy stored in the electromagnetic coil MC is transferred to the capacitor C0, the voltage of the capacitor C0 is the highest, and the voltage applied to the first switch W reaches the resonance peak.

Substituting formula (2) into formula (3), you can get:

Therefore, the peak V _PEAK of the resonant voltage on the first switch W also exhibits a sinusoidal variation as the input voltage. When the power of the induction cooker is set to the maximum, the on-time Ton of the first switch W also reaches the maximum. Since the AC input voltage is unstable, the fluctuation range is 176V~264V. If the input voltage is 264V, the peak of the resonance will be close. 1200V, even reaching the withstand voltage of the switch W, so that the first switch W may be damaged by overvoltage.

When the resonance is at the peak, the first switch W may be damaged; likewise, when the resonance is in the valley, the first switch W may be adversely affected.

When the energy on the capacitor C0 is all transferred to the inductor to form a negative current, the energy of the inductor is all transferred to the capacitor C0 to form a reverse voltage. As shown in FIG. 5, the voltage on the first switch W will reach resonance. Valley, at this time: V _VALLEY = 2 . V _input sin θ - V _PEAK (5)

Substituting the formula (4) into the formula (5), you can get:

Among them, V _VALLEY is the valley voltage of resonance. It can be seen from the above formula (6) that the valley voltage of the resonance on the switch also exhibits a sinusoidal variation as the AC input voltage. When the power of the induction cooker is set to a minimum, the on-time Ton of the switch is also the shortest; since the AC input voltage is unstable, there is a certain fluctuation range of 176V~264V. If the input voltage is 264V, the valley voltage of the resonance will exceed 100V or higher. At this time, if the first switch W is turned on, the first switch W is damaged due to excessive loss.

It can be seen from the above that if the resonance voltage on the first switch W is controlled, including the peak voltage and the valley voltage, the service life of the first switch W is increased, and the safety of the induction cooker is enhanced.

The above analysis is performed under the condition that the loop impedance is approximately 0. When the load of the induction cooker is connected, the loop impedance will increase, but the analysis method will not change.

In order to solve one or more of the above problems, the present invention proposes a new method of controlling the peaks and troughs of the resonant voltage of the main circuit switch of the induction cooker.

According to an aspect of the present invention, a control circuit for an induction cooker is provided, comprising: a first control unit that integrates a current corresponding to a voltage difference between a voltage of a first reference voltage and a first voltage signal to obtain a second a voltage signal, and comparing a voltage of the third voltage signal as the ramp signal with a voltage of the second voltage signal to output a first control signal; and a second control unit, a fifth voltage signal reflecting a voltage change of the fourth voltage signal The voltage is compared with the first threshold voltage to output a second control signal; the first logic control unit outputs the third control signal based on the first control signal and the second control signal respectively output from the first control unit and the second control unit Controlling the main circuit switch of the induction cooker, wherein the first control unit comprises: a resonance peak control circuit, sampling a resonance peak voltage of the main circuit switch of the induction cooker, and generating a first compensation current by using the sampled resonance peak voltage, the first A control unit passes the first compensation current generated by the resonance peak control circuit with a constant Generating a stream by adding a third ramp voltage signal as a signal using a capacitor.

According to another aspect of the present invention, the first control unit further includes: a resonant valley control circuit that samples a resonant valley voltage of the main circuit switch of the induction cooker, and generates a second compensation current by using the sampled resonant valley voltage, wherein The first control unit generates a third voltage signal as a ramp signal by subtracting the second compensation current generated by the resonant valley control circuit from the constant current using a capacitor.

According to another aspect of the present invention, in the resonance peak control circuit, the sampled resonance peak voltage is input to the non-inverting input terminal of the first voltage control current source through the first RC integration circuit, and the second reference voltage is input. The first voltage controls the inverting input of the current source to generate a first compensation current.

According to another aspect of the present invention, in the resonant valley control circuit, the sampled resonant valley voltage is input to the non-inverting input of the second voltage controlled current source through the second RC integrating circuit, and the third reference voltage is input The second voltage controls the inverting input of the current source to generate a second compensation current.

According to another aspect of the present invention, in the resonance peak control circuit and the resonance valley control circuit, the sampled voltage is input to the first by a voltage follower circuit, respectively RC integration circuit and second RC integration circuit.

According to another aspect of the present invention, in the resonance peak control circuit, the sampled resonance peak voltage is compared with a fourth reference voltage to generate a first pulse signal, and the rectified input voltage is performed by using the first pulse signal. Sampling, and inputting the rectified input voltage and the sampled input voltage to the non-inverting input and the inverting input of the third voltage-controlled current source, respectively, to generate a first compensation current.

According to another aspect of the present invention, in the resonant valley control circuit, the sampled resonant valley voltage is compared with a fifth reference voltage to generate a second pulse signal, and the second pulse signal is used to perform the rectified input voltage. Sampling, and inputting the rectified input voltage and the sampled input voltage to the non-inverting input and the inverting input of the fourth voltage-controlled current source respectively to generate a second compensation current.

According to another aspect of the present invention, the first logic control unit is an RS flip-flop, the first control signal is input to the reset terminal of the RS flip-flop, and the second control signal is input to the set terminal of the RS flip-flop. When the first control signal is at a high level, the third control signal outputted from the first logic control unit is at a low level, the induction cooker main circuit switch is turned off; and when the second control signal is at a high level, is output from the first logic control unit The third control signal is at a high level, and the main circuit switch of the induction cooker is turned on.

According to another aspect of the present invention, there is provided a control circuit comprising: a ramp signal generator for sampling a resonance peak voltage of an induction cooker main circuit switch by a resonance peak control circuit included in a ramp signal generator, and using sampling a resonance peak voltage generates a first compensation current, and generates a ramp signal by adding a first compensation current generated by the resonance peak control circuit to the constant current; a differential integration circuit that is to be associated with the first reference voltage and the first voltage signal The voltage corresponding to the voltage difference between the voltages is integrated to obtain a second voltage signal; the comparator compares the voltage of the third voltage signal as the ramp signal with the voltage of the second voltage signal to output the first control signal to facilitate controlling the induction cooker Main circuit switch.

According to another aspect of the present invention, the ramp signal generator further includes: a resonant valley control circuit that samples a resonant valley voltage of the main circuit switch of the induction cooker, and generates a second compensation current by using the sampled resonant valley voltage, wherein The ramp signal generator utilizes a capacitor by subtracting a second compensation current generated by the resonant valley control circuit from a constant current Generate a ramp signal.

According to another aspect of the present invention, in the resonance peak control circuit, the sampled resonance peak voltage is input to the non-inverting input terminal of the first voltage control current source through the first RC integration circuit, and the second reference voltage is input. The first voltage controls the inverting input of the current source to generate a first compensation current.

According to another aspect of the present invention, in the resonant valley control circuit, the sampled resonant valley voltage is input to the non-inverting input of the second voltage controlled current source through the second RC integrating circuit, and the third reference voltage is input The second voltage controls the inverting input of the current source to generate a second compensation current.

According to another aspect of the invention, in the resonance peak control circuit and the resonance valley control circuit, the sampled voltage is input to the first RC integration circuit and the second RC integration circuit, respectively, using a voltage follower circuit.

According to another aspect of the present invention, in the resonance peak control circuit, the sampled resonance peak voltage is compared with a fourth reference voltage to generate a first pulse signal, and the rectified input voltage is performed by using the first pulse signal. Sampling, and inputting the rectified input voltage and the sampled input voltage to the non-inverting input and the inverting input of the third voltage-controlled current source respectively to generate a first compensation current.

According to another aspect of the present invention, in the resonant valley control circuit, the sampled resonant valley voltage is compared with a fifth reference voltage to generate a second pulse signal, and the second pulse signal is used to perform the rectified input voltage. Sampling, and inputting the rectified input voltage and the sampled input voltage to the non-inverting input and the inverting input of the fourth voltage-controlled current source respectively to generate a second compensation current.

According to another aspect of the present invention, there is provided a control method comprising: integrating a current corresponding to a voltage difference between a first reference voltage and a voltage of a first voltage signal to obtain a second voltage signal, and as a ramp signal The voltage of the third voltage signal is compared with the voltage of the second voltage signal to output a first control signal; the voltage of the fifth voltage signal reflecting the voltage change of the fourth voltage signal is compared with the first threshold voltage to output a second a control signal; outputting a third control signal based on the first control signal and the second control signal respectively to control the main circuit switch of the induction cooker; wherein, the resonance peak voltage of the main circuit switch of the induction cooker is sampled, A first compensation current is generated by using the sampled resonant peak voltage; and a third voltage signal is generated as a ramp signal by adding the generated first compensation current to the constant current.

According to another aspect of the present invention, the control method further includes: sampling a resonant valley voltage of the main circuit switch of the induction cooker, generating a second compensation current by using the sampled resonant valley voltage, and generating a second compensation current and a constant The current is subtracted to generate a third voltage signal that is a ramp signal.

According to another aspect of the present invention, a control method is provided, comprising: sampling a resonance peak voltage of an induction cooker main circuit switch, and generating a first compensation current by using the sampled resonance peak voltage, and passing the generated first compensation And adding a current to the constant current to generate a ramp signal; integrating a current corresponding to a voltage difference between the first reference voltage and the voltage of the first voltage signal to obtain a second voltage signal; and using the third voltage signal as the ramp signal The voltage is compared to the voltage of the second voltage signal to output a first control signal to facilitate control of the main circuit switch of the induction cooker.

According to another aspect of the present invention, the control method further includes: sampling a resonant valley voltage of the main circuit switch of the induction cooker, generating a second compensation current by using the sampled resonant valley voltage, and generating a second compensation current and a constant The current is subtracted to generate a ramp signal.

According to another aspect of the present invention, there is also provided an induction cooker comprising the control circuit as described above.

By adopting the technical scheme of the invention, the resonant voltage of the induction cooker, including the peak and the valley voltage, can be controlled in time and effectively, thereby increasing the safety of the induction cooker.

610‧‧‧First Control Unit

620‧‧‧Second control unit

630‧‧‧Logical Control Unit

710‧‧‧Differential integration circuit

720‧‧‧First comparator

730‧‧‧Ramp signal generation module

C0, C1, C2, C3‧‧‧ capacitors

C4‧‧‧fourth capacitor

C5‧‧‧ fifth capacitor

C6‧‧‧ sixth capacitor

C7‧‧‧ seventh capacitor

C8‧‧‧ eighth capacitor

C9‧‧‧ ninth capacitor

C10‧‧‧10th Capacitor

C11‧‧‧11th capacitor

Gate‧‧‧ control signal

Gm‧‧‧operating transconductance amplifier

I _in ‧‧‧Input current

i‧‧‧Constant current

I1‧‧‧First compensation current

I2‧‧‧second compensation current

K1‧‧‧ third switch

K2‧‧‧fourth switch

K3‧‧‧ fifth switch

K4‧‧‧ sixth switch

K5‧‧‧ seventh switch

K6‧‧‧ eighth switch

MC‧‧‧Electromagnetic coil

Off‧‧‧First control signal

On‧‧‧second control signal

Q‧‧‧output

R1‧‧‧ first resistor

R2‧‧‧second resistance

R3‧‧‧ third resistor

R4‧‧‧fourth resistor

R5‧‧‧ fifth resistor

Rs‧‧‧ current sense resistor

Ramp‧‧‧ ramp signal

Ref1‧‧‧first reference voltage

Ref2‧‧‧second reference voltage

Ts1, Ts2‧‧‧ pulse signal

Vin‧‧‧Input voltage

Vw, comp‧‧‧ voltage signal

Vcs, Vc1, Vc2, V1, V2‧‧‧ voltage

Vref‧‧‧reference voltage

Vth‧‧‧ threshold voltage

Vs1‧‧•crest voltage

Vs2‧‧‧ Valley voltage

Vccs1‧‧‧First voltage controlled current source

Vccs2‧‧‧second voltage controlled current source

Vccs3‧‧‧ third voltage controlled current source

Vccs4‧‧‧fourth voltage controlled current source

W‧‧‧first switch

W1‧‧‧second switch

Fig. 1 is a schematic view showing the operation of the induction cooker.

Figure 2 shows a schematic diagram of the main circuit in which the induction cooker is operating.

Figure 3 shows the current flow of the main circuit when the switch of the main circuit of the induction cooker is turned on.

Fig. 4 shows the current flow of the resonant circuit formed by the electromagnetic coil and the capacitor in the induction cooker when the switch of the main circuit of the induction cooker is turned off.

Figure 5 shows that when the switch of the main circuit of the induction cooker is turned off, it forms an inverse on the capacitor because of resonance. The current flows toward the voltage.

Fig. 6 is a block diagram showing the construction of a control circuit of the induction cooker system according to the present invention.

Fig. 7 is a view showing a schematic configuration of the first control unit in Fig. 6.

Fig. 8 is a view showing a schematic configuration of a second control unit in Fig. 6.

Fig. 9 is a view showing waveform comparison before and after control of a resonance voltage peak on an induction cooker main circuit switch according to an exemplary embodiment of the present invention.

Fig. 10 is a view showing waveform comparison before and after control of a resonance voltage trough on an induction cooker main circuit switch according to an exemplary embodiment of the present invention.

Fig. 11 is a view showing a control circuit for controlling the peaks and troughs of the resonance voltage on the main circuit switch of the induction cooker according to the first embodiment of the present invention.

Fig. 12A is a view showing waveforms of a peak sampling pulse signal, a resonance voltage, a control signal for controlling ON/OFF of the main circuit switch of the induction cooker, and a ramp signal according to the first embodiment of the present invention.

12B is a waveform diagram showing a control circuit lower valley sampling pulse signal, a resonance voltage, a control signal for controlling the on/off of the induction cooker main circuit switch, and a ramp signal according to the first embodiment of the present invention.

Figure 13 is a diagram showing a control circuit for controlling the peaks and troughs of the resonance voltage on the main circuit switch of the induction cooker in accordance with the second embodiment of the present invention.

FIG. 14A is a diagram showing a resonance voltage peak envelope when uncontrolled, a resonance voltage peak envelope when the control circuit according to the second embodiment of the present invention performs control, and a pulse signal generated when the resonance peak voltage is greater than the first reference voltage. Waveform.

FIG. 14B is a diagram showing a resonance voltage valley envelope when uncontrolled, a resonance voltage valley envelope when the control circuit according to the second embodiment of the present invention performs control, and a pulse signal generated when the resonance valley voltage is greater than the second reference voltage. Waveform.

The invention will now be described in detail in connection with the specific embodiments. Those skilled in the art should understand that the embodiments of the present invention are only exemplary and not intended to limit the invention. Those skilled in the art will appreciate that the above described circuitry can be applied to any application where applicable and is not limited to controlling the power of the induction cooker. Below, for the sake of simplicity The power control circuit is applied to the power control of the induction cooker.

A schematic diagram of the control circuit of the induction cooker system is shown in Fig. 6. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will be able to adapt, adapt, and modify in accordance with the drawings.

The input current I _in is the current flowing from the grid end into the induction cooker system. When the first switch W on the main circuit of the induction cooker is turned on, the input current I _in flows into the induction cooker system; when the first switch W is turned off, the input current I _in will be Stop flowing into the induction cooker system. As shown in FIG. 6, the current detection resistor Rs connected with the first switch in series W to be connected to the main circuit of the magnitude of the input current I _in is detected. Since the voltage is the product of the resistance value and the current, the voltage Vcs on the current detecting resistor R _s also reflects the magnitude of the input current I _in .

As shown in FIG. 6, the induction cooker system control circuit includes a first control unit 610, a second control unit 620, and a logic control unit 630. The logic control unit 630 outputs a control signal gate for controlling the on and off of the switch W on the main circuit of the induction cooker according to the control signals respectively output by the first control unit 610 and the second control unit 620.

The first control unit 610 receives the reference voltage Vref corresponding to the set power of the induction cooker and a voltage signal corresponding to the magnitude of the current on the main circuit of the induction cooker (for example, the voltage Vcs on the current detecting resistor Rs), corresponding to the voltage difference of the signals The current is integrated, and then the obtained voltage is compared with the voltage of the ramp signal ramp to output a first control signal off for controlling the first switch W to be turned off to the logic control unit 630, wherein the first control signal off is electric The flat signal, when the first control signal off is at a high level, can control the first switch W on the main circuit of the induction cooker to be turned off.

The second control unit 620 receives the voltage signal Vw applied to the first switch W via the parallel electromagnetic coil MC and the capacitor C0 (the electromagnetic coil MC and the capacitor C0 constitute a resonant circuit) in the main circuit of the induction cooker, and will correspond to the signal The voltage is compared with the threshold voltage Vth to output a second control signal on for controlling the first switch W to be turned on to the logic control unit 630. The second control signal on is a level signal. When the second control signal on is high, the first switch W can be controlled to be turned on by the logic control unit 630.

The logic control unit 630 outputs the first control signal off and the second control signal on output from the first control unit 610 and the second control unit 620 for controlling the first switch. The control signal of the turn-on and turn-off of W.

As an example, the logic control unit 630 is an RS flip-flop, the output of the first control unit 610 is connected to the reset terminal of the RS flip-flop, and the output of the second control unit 620 is connected to the set terminal of the RS flip-flop. That is, the first control signal off is input to the reset terminal of the RS flip-flop and the second control signal on is input to the set terminal of the RS flip-flop. The output terminal Q of the RS flip-flop is connected to the control terminal of the first switch W to control the on and off of the first switch W. Here, by way of example only and not limitation, the first switch W may be an insulated gate bipolar transistor switch.

A schematic structural diagram of the first control unit 610 is shown in FIG.

As an example, as shown in FIG. 7, the first control unit 610 includes a differential integration circuit 710, a first comparator 720, and a ramp signal generation module 730. The differential integration circuit 710 includes an operational transconductance amplifier gm and a capacitor C1. According to an exemplary embodiment of the present invention, a reference voltage Vref corresponding to the set power of the induction cooker and a voltage signal reflecting the magnitude of the current of the main circuit of the induction cooker (for example, the voltage Vcs on the current detecting resistor Rs, hereinafter for convenience of description, the voltage Vcs is used. As an example, it is input to the differential integration circuit 710 to integrate currents corresponding to the voltage differences of the two voltage signals. Wherein, the reference voltage Vref corresponding to the set power is input to the non-inverting input terminal of the operational transconductance amplifier gm, and the voltage Vcs is input to the inverting input terminal of the operational transconductance amplifier gm to be based on the voltage difference between the two input signals To adjust the size of the output current. The output terminal of the operational transconductance amplifier gm is connected to the capacitor C1, so that the current corresponding to the voltage difference between the two voltage signals input to the operational transconductance amplifier gm output by the operational transconductance amplifier gm is integrated by the capacitor C1 to obtain a capacitor. The voltage signal comp on C1. Further, one end of the capacitor C1 (which is also the end at which the capacitor C1 is connected to the output terminal of the operational transconductance amplifier gm) is connected to the inverting input terminal of the first comparator 720, thereby inputting the voltage signal comp to the first comparator 720.

The non-inverting input terminal of the first comparator 720 inputs the ramp signal ramp generated by the ramp signal generating module 730, thereby comparing the voltage of the ramp signal ramp with the voltage of the voltage signal comp to output the first control signal to the logic control unit 630. Off. When the voltage of the ramp signal ramp is higher than the voltage of the voltage signal comp, the first control signal off output from the first comparator 720 (ie, output from the first control unit 610) becomes a high level, thereby causing slave logic control The control signal gate outputted by the unit 630 becomes a low level, so the first switch W on the main circuit of the induction cooker is turned off.

The ramp signal generation module 730 can include a capacitor C2, a current source, and a second switch. W1 and resonant voltage control module. The resonant voltage control module is configured to provide a compensation current for charging capacitor C2 based on the resonant voltage value. The ramp signal ramp is synchronized with the control signal gate. When the first switch W is turned on, that is, when the control signal gate outputs a high level, the second switch W1 is turned off, and the constant current i outputted by the current source and the compensation current output by the resonant voltage control module charge the capacitor C2, the slope The voltage of the signal ramp is gradually increased; when the first switch W is turned off, that is, when the control signal gate outputs a low level, the second switch W1 is turned on, the capacitor C2 is quickly discharged through the second switch W1, and the voltage of the ramp signal ramp is sharply decreased. Is 0.

A schematic structural view of the second control unit 620 is shown in FIG.

As an example, the second control unit 620 includes a second comparator, a capacitor C3, a first resistor R1, a second resistor R2, and a third resistor R3. The second resistor R2 has a voltage signal Vw applied to the first switch W at one end and a parallel circuit composed of a series circuit formed by the capacitor C3 and the first resistor R1 at the other end. A node to which the first resistor R1 is connected to the capacitor C3 is connected to the inverting input terminal of the second comparator, and a non-inverting input terminal of the second comparator inputs the threshold voltage Vth. The output of the second comparator is connected to the logic control unit 630 to input a second control signal on which it is output, to the logic control unit 630. Here, the voltage of the voltage signal Vw divided by the second resistor R2 is differentiated by the capacitor C3 to generate a current representing the slope of the resonance voltage (the voltage signal Vw after the first switch W is turned off), and the current flows through the first resistor. R1 generates a voltage, and thus the voltage generated by the first resistor R1 also represents the slope of the resonant voltage. The voltage is supplied to the second comparator together with the threshold voltage Vth. When the voltage is less than the threshold voltage Vth, it represents resonance to or near the valley, and the second control signal on of the second comparator is turned to a high level, so that the logic control The control signal gate outputted on unit 630 goes high, thereby turning on the first switch W on the main circuit of the induction cooker.

According to an exemplary embodiment of the present invention, after the first switch W is turned off, the resonance circuit composed of the electromagnetic coil MC and the capacitor C0 generates resonance, and the second control unit 620 reflects the change of the voltage signal applied to the first switch W. The voltage of the rate (for example, the voltage on the first resistor R1) is compared with the threshold voltage Vth. When the voltage is less than the threshold voltage Vth, it indicates that the resonance is at or near the valley, and the second control signal output by the second control unit 620 On becomes a high level, so that the control signal gate output from the logic control unit 630 becomes a high level, and thus the first switch W is turned on.

It can be seen from the above formulas (4) and (6) that the peaks and troughs of the resonant voltage of the first switch W are a function of the on-time Ton. Specifically, the peaks and troughs of the resonant voltage increase with the increase of the on-time Ton. Big and small. When the resonance voltage peak of the first switch W exceeds the first reference voltage, the slope of the ramp signal ramp is increased, and the on-time Ton required for the voltage of the ramp signal ramp to exceed the voltage of the voltage signal comp is shortened, thereby reducing the first switch The resonant voltage peak on W; when the valley of the resonant voltage of the first switch W exceeds the second reference voltage, the slope of the ramp signal ramp is decreased, and the voltage required for the voltage of the ramp signal ramp exceeds the voltage of the voltage signal comp Extending, thereby reducing the valley of the resonant voltage on the first switch W.

Fig. 9 is a view showing waveform comparison before and after control of the resonance voltage peak of the first switch W on the main circuit of the induction cooker according to an exemplary embodiment of the present invention. If the peak control of the resonant voltage is not added, the peak envelope of the resonant voltage on the first switch W appears as a sine wave with the change of the rectified input voltage Vin; when the input voltage Vin is at the peak, the resonant voltage will also be at the resonant voltage. The peak position of the peak envelope, at which point the resonant voltage will exceed the preset first reference voltage. When the peak voltage control is added, if the peak of the resonant voltage exceeds the first reference voltage, the on-time Ton is decreased by increasing the slope of the ramp signal ramp, so that the peak of the resonant voltage is maintained at the first reference voltage.

Fig. 10 is a view showing waveform comparison before and after control of the resonance voltage trough of the first switch W on the main circuit of the induction cooker according to an exemplary embodiment of the present invention. If the valley of the resonant voltage is not controlled, the valley of the resonant voltage on the first switch W appears as a sine wave with the change of the input voltage Vin; when the input voltage Vin is at the peak, the resonant voltage will also be at the peak position of the envelope of the resonant voltage valley. At this time, the resonant voltage will exceed the second reference voltage. When the valley voltage control is added, if the valley of the resonance voltage exceeds the second reference voltage, the on-time Ton is extended by decreasing the slope of the ramp signal ramp so that the valley of the resonance voltage is controlled to the second reference voltage.

Since the induction cooker system needs to maintain a preset power when the resonance voltage is controlled, the circuit system in the induction cooker is automatically adjusted so that the resonance peak voltage and the valley voltage are maintained near the first reference voltage and the second reference voltage, respectively. The time is longer than the peaks and troughs of the resonant voltage exceeding the first reference voltage and the second reference voltage, respectively, under the condition that the resonance voltage control is not performed. Reflected on the waveform, you can visually see that you are joining After the resonant voltage is controlled, the resonant peak voltage and the valley voltage will rise to the first reference voltage and the second reference voltage, respectively, and the speed of falling from the first reference voltage and the second reference voltage, respectively, will also be faster.

Figure 11 is a specific implementation circuit of the resonant voltage control module of Figure 6 in accordance with an exemplary embodiment of the present invention. It should be understood by those skilled in the art that the circuit configuration shown in FIG. 11 is merely an example, and should not unduly limit the scope of the patent application. Those skilled in the art will be able to adapt, adapt, and modify the invention on the basis of the embodiments.

The resonant voltage control module includes a resonant peak control portion and a resonant valley control portion; the waveform of each signal in the resonant peak control portion is as shown in FIG. 12A, and the waveform of each signal in the resonant valley control portion is as shown in FIG. 12B.

In the resonance peak control section, one end of the third switch K1 is input to the switching voltage signal Vw on the main circuit of the induction cooker, the other end of the third switch K1 is connected to the fourth capacitor C4, and the other end of the fourth capacitor C4 is grounded. As an example, the capacitance value of the fourth capacitor C4 may be 10 pF. One end of the third switch K1 connected to the fourth capacitor C4 is connected to the non-inverting input terminal of the first follower circuit. The third switch K1 is turned on or off under the control of the peak sampling signal, and the peak sampling signal is a pulse signal. As shown in FIG. 12A, when the voltage signal Vw is at the peak position of the voltage signal Vw in each period, the peak The sampling signal is at a high level, and the third switch K1 is turned on. When the third switch K1 is turned on, one end of the fourth capacitor C4 connected to the third switch K1 is an instantaneous value of the peak voltage Vs1 of the resonant voltage signal Vw; when the third switch K1 is turned off, the peak is still maintained on the fourth capacitor C4. The voltage Vs1 is input to the non-inverting input of the first follower circuit. The output end of the first follower circuit is connected to its inverting input terminal, and is connected to an RC integrating circuit composed of a fourth resistor R4 and a fifth capacitor C5, wherein the node connecting the fourth resistor R4 and the fifth capacitor C5 is The non-inverting input of the first voltage controlled current source vccs1 is connected. The voltage Vc1 on the fifth capacitor C5 is input to the non-inverting input terminal of the first voltage control current source vccs1. The first reference voltage ref1 is input to the inverting input terminal of the first voltage control current source vccs1, and the first voltage control current source vccs1 generates a first compensation current i1 that is proportional to the voltage difference between the voltage Vc1 and the first reference voltage ref1. After the first compensation current i1 is added to the constant current i output from the current source, the capacitor C2 is charged to generate a ramp signal ramp.

As another example, in the above-described resonance peak control portion, the first follower circuit may not be required, and the remaining portions of the circuit are unchanged. That is, the third switch K1 and the fourth capacitor One end connected to C4 is directly connected to the RC integration circuit composed of the fourth resistor R4 and the fifth capacitor C5, and the voltage Vc1 on the fifth capacitor C5 is input to the non-inverting input terminal of the first voltage control current source vccs1.

In the resonance valley control portion, one end of the fourth switch K2 is input to the switching voltage signal Vw on the main circuit of the induction cooker, the other end is connected to the sixth capacitor C6, and the other end of the sixth capacitor C6 is grounded. As an example, the capacitance value of the sixth capacitor C6 may be 10 pF. One end of the fourth switch K2 connected to the sixth capacitor C6 is connected to the non-inverting input terminal of the second follower circuit. The fourth switch K2 is controlled to be turned on or off by the valley sampling signal, and the valley sampling signal is a pulse signal. As shown in FIG. 12B, when the control signal gate of the first switch W of the main circuit of the induction cooker is controlled, the low level is When the period is close to the end, the valley sampling signal is at a high level, and the fourth switch K2 is turned on. When the fourth switch K2 is turned on, one end of the sixth capacitor C6 connected to the fourth switch K2 is the valley voltage Vs2 of the resonant voltage signal Vw; when the fourth switch K2 is turned off, the valley voltage Vs2 is still maintained on the sixth capacitor C6, And input to the non-inverting input of the second follower circuit. The output of the second follower circuit is connected to its inverting input terminal, and is connected to an RC integrating circuit composed of a fifth resistor R5 and a seventh capacitor C7, wherein the node and the fifth resistor R5 are connected to the seventh capacitor C7. The positive phase input of the two voltage controlled current source vccs2 is connected. The voltage Vc2 on the seventh capacitor C7 is input to the non-inverting input of the second voltage controlled current source vccs2. The second reference voltage ref2 is input to the inverting input terminal of the second voltage control current source vccs2, and the second voltage control current source vccs2 generates a second compensation current i2 proportional to the voltage difference between the voltage Vc2 and the second reference voltage ref2 After the second compensation current i2 is subtracted from the constant current i output by the current source, the capacitor C2 is charged to generate a ramp signal ramp.

In the above-described resonance peak control section, the second follower circuit may not be required, and the rest of the circuits are unchanged. That is, one end of the fifth switch K3 connected to the sixth capacitor C6 is directly connected to the RC integration circuit composed of the fifth resistor R5 and the seventh capacitor C7, and the voltage Vc2 on the seventh capacitor C7 is input to the second voltage control current source vccs2. Positive phase input.

In the first embodiment, the slope of the ramp signal ramp is adjusted by a closed loop method to control the peaks and valleys of the resonance voltage in the vicinity of the first reference voltage ref1 and the second reference voltage ref2, respectively. The selection of the parameters of the RC integration circuit in the resonance peak and valley control sections, and the ratio of the first and second compensation currents i1 and i2 generated by the first and second voltage control current sources vccs1 and vccs2 will affect the final peak. Control of voltage and valley voltage.

Figure 13 is a specific implementation circuit of the resonant voltage control module of Figure 6 in accordance with the second embodiment of the present invention. It should be understood by those skilled in the art that the circuit structure shown in FIG. 13 is only an example, and should not unduly limit the scope of the patent application. Adaptable variations, substitutions, and modifications can be made by those skilled in the art based on this embodiment.

The control circuit in the second embodiment includes a resonance peak control portion and a resonance valley control portion; the waveform of each signal in the resonance peak control portion is as shown in FIG. 14A, and the waveform of each signal in the resonance valley control portion is as shown in FIG. 14B. Show.

In the resonance peak control section, one end of the fifth switch K3 is input to the switching voltage signal Vw on the main circuit of the induction cooker, the other end is connected to the eighth capacitor C8, and the other end of the eighth capacitor C8 is grounded. As an example, the capacitance value of the eighth capacitor C8 may be 10 pF. One end of the fifth switch K3 connected to the eighth capacitor C8 is connected to the non-inverting input terminal of the third comparator. The fifth switch K3 is turned on or off under the control of the peak sampling signal. As in the first embodiment, the peak sampling signal is a pulse signal. When the voltage signal Vw is at a peak position in each period, the peak sampling signal is High level, the fifth switch K3 is turned on. When the fifth switch K3 is turned on, one end of the eighth capacitor C8 connected to the fifth switch K3 is an instantaneous value of the peak voltage Vs1 of the resonant voltage signal Vw; when the fifth switch K3 is turned off, the eighth capacitor C8 remains The peak voltage Vs1 is input to the non-inverting input of the third comparator. The first reference voltage ref1 is input to the inverting input of the third comparator. When the peak voltage Vs1 is greater than the first reference voltage ref1, the third comparator outputs a high-level pulse signal Ts1, the input voltage Vin is input to the ninth capacitor C9 through the sixth switch K4, and the other end of the ninth capacitor C9 is grounded. As an example, the capacitance value of the ninth capacitor C9 may be 10 pF. The pulse signal Ts1 controls the on and off of the sixth switch K4. When the pulse signal Ts1 is at a high level, the sixth switch K4 is turned on, and the voltage on the ninth capacitor C9 (that is, the voltage at the end of the ninth capacitor C9 and the sixth switch K4) is the instantaneous value of the voltage V1 of the input voltage Vin. When the sixth switch K4 is turned off, the voltage V1 is still held on the ninth capacitor C9, and is input to the inverting input terminal of the third voltage control current source vccs3. The input voltage Vin is input to the non-inverting input of the third voltage controlled current source vccs3. The third voltage control current source vccs3 generates a first compensation current i1 that is proportional to the difference between the input voltage Vin and the voltage V1. After the first compensation current i1 is added to the constant current i output by the current source, the capacitor C2 is charged. A ramp signal ramp is generated.

In the resonant valley control section, one end of the seventh switch K5 is input to the induction cooker The voltage signal Vw of the first switch W on the loop is connected to the tenth capacitor C10 at the other end, and the other end of the tenth capacitor C10 is grounded. As an example, the capacitance value of the tenth capacitor C10 may be 10 pF. One end of the seventh switch K5 connected to the tenth capacitor C10 is connected to the non-inverting input terminal of the fourth comparator. The seventh switch K5 is turned on or off under the control of the valley sampling signal. As in the first embodiment, the valley sampling signal is a pulse signal, and when the control signal gate of the first switch W of the main circuit of the induction cooker is controlled, the low level is When the cycle is near the end, the valley sampling signal is at a high level, and the seventh switch K5 is turned on. When the seventh switch K5 is turned on, one end of the tenth capacitor C10 connected to the seventh switch K5 is the valley voltage Vs2 of the resonant voltage signal Vw; when the seventh switch K5 is turned off, the valley voltage Vs2 is maintained on the tenth capacitor C10. And input the positive phase input of the fourth comparator. The second reference voltage ref2 is input to the inverting input of the fourth comparator. When the valley voltage Vs2 is greater than the second reference voltage ref2, the fourth comparator outputs a high-level pulse signal Ts2. The input voltage Vin is connected to the eleventh capacitor C11 through the eighth switch K6, and the other end of the eleventh capacitor C11 is grounded. As an example, the capacitance value of the eleventh capacitor C11 may be 10 pF. The pulse signal Ts2 controls the on and off of the eighth switch K6. When the pulse signal Ts2 is at a high level, the eighth switch K6 is turned on, and the end of the eleventh capacitor C11 connected to the eighth switch K6 is an instantaneous value of the input voltage V2; when the eighth switch K6 is turned off, the eleventh capacitor C11 The voltage V2 is still maintained and is input to the inverting input of the fourth voltage control current source vccs4. The input voltage Vin is input to the non-inverting input of the fourth voltage controlled current source vccs4. The fourth voltage control current source vccs4 generates a second compensation current i2 proportional to the difference between the input voltage Vin and the voltage V2, and after the second compensation current i2 is subtracted from the constant current i output from the current source, the capacitor C2 is charged. A ramp signal ramp is generated.

If the peak of the resonance voltage is not controlled, the more the peak of the resonance voltage is "flattened" when the peak control is added, the waveform of the resonance voltage after "flattening" is reflected in order to ensure that the power of the induction cooker does not change. In the figure, the time when the peak voltage Vs1 rises to the first reference voltage ref1 will be shorter. For the above reasons, if the peak of the resonance voltage is not controlled, the time when the peak voltage Vs1 exceeds the first reference voltage ref1 when the peak control is added, that is, the timing at which the pulse signal Ts1 is at the high level corresponds to the input. The phase angle of the voltage Vin is smaller. Since the voltage change is faster as the phase angle is smaller, the smaller the phase angle is, the larger the first compensation current i1 superimposed on the constant current i is, and the more the on-time Ton is decreased; for the same reason, if not The higher the valley of the resonant voltage at the time of control, the time when the valley of the resonant voltage exceeds the second reference voltage ref2 The smaller the phase angle, the larger the second compensation current i2 which is subtracted from the constant current i, and the more the on-time Ton increases.

Therefore, under the control circuit of the second embodiment, the magnitude of the current compensation amount is related to the level of the peaks and troughs of the resonance voltage without the addition of the compensation condition. The ratio of the difference between the two voltages input to the third and fourth voltage control current sources vccs3, vccs4 and the ratio of the first and second compensation currents i1, i2 will affect the control effect of the resonance voltage.

It should be understood by those skilled in the art that the resonance control module shown in FIGS. 11 and 13 includes a resonance peak control portion and a resonance valley control portion as examples, and the resonance peak control portion and the resonance valley control portion are relatively independent circuits. The invention may include only the resonance peak control portion or the resonance valley control portion.

The control circuit in the above two embodiments can be applied to induction cookers of different power levels to realize the control of the peaks and/or troughs of the resonant voltage in the full voltage input range. In practice, the applicable environments of the first embodiment and the second embodiment described above are different; under the condition that the accuracy of the peak and valley maximum of the resonant voltage is relatively high, and a large filter RC time constant can be provided. The resonance voltage can be controlled in the manner of the first embodiment; in the case where the accuracy of the peak and valley maximum of the resonance voltage is not high, and the larger filter RC time constant cannot be provided, the second embodiment can be employed. The way to control the resonant voltage.

The technical scheme of the invention is applicable to the induction cooker system of different power levels, can effectively control the peak of the resonance voltage without affecting the output power of the induction cooker, and avoid the damage of the switch on the main circuit of the induction cooker due to overpressure, and can also be controlled The valley of the resonant voltage reduces the turn-on loss of the switch on the main circuit and avoids the switching fan of the induction cooker.

The preferred embodiments of the present invention are described above, but the scope of the present invention is defined by the scope of the appended claims. In addition, the present invention and its advantages are described in detail, and it is to be understood that various changes, substitutions and changes can be made without departing from the spirit and scope of the invention. The scope of the invention is not limited to the embodiments of the systems, methods and steps described in the specification. It will be understood by those of ordinary skill in the art that, by the present invention, existing or future developed methods and steps for performing substantially the same or substantially the same results as those employed in accordance with the present invention may be made in accordance with the present invention. use.

Claims (5)

A control circuit includes: a ramp signal generator, sampling a resonance peak voltage of an induction cooker main circuit switch by a resonance peak control circuit included in the slope signal generator, and generating a first compensation by using the sampled resonance peak voltage And generating a ramp signal by using the capacitor by adding the first compensation current generated by the resonance peak control circuit to the constant current; and a differential integration circuit to compare a voltage difference between the first reference voltage and the voltage of the first voltage signal Integrating a corresponding current to obtain a second voltage signal, wherein the first voltage signal corresponds to a magnitude of a current on a main circuit of the induction cooker; and a comparator, a voltage of the third voltage signal as a ramp signal and a voltage of the second voltage signal Comparing to output a first control signal to control the main circuit switch of the induction cooker; a resonant valley control circuit, sampling a resonant valley voltage of the main circuit switch of the induction cooker, and generating a second compensation current by using the sampled resonant valley voltage, wherein The ramp signal generator passes The second compensation current generated by the resonant valley control circuit is subtracted from the constant current to generate the ramp signal by using the capacitor; in the resonant peak control circuit, the sampled resonant peak voltage is compared with a fourth reference voltage to generate a first pulse signal, the rectified input voltage is sampled by the first pulse signal, and the rectified input voltage and the sampled input voltage are respectively input to a positive phase input terminal of the third voltage control current source and Inverting an input terminal to generate the first compensation current; in the resonant valley control circuit, comparing the sampled resonant valley voltage with a fifth reference voltage to generate a second pulse signal, using the second pulse signal The rectified input voltage is sampled, and the rectified input voltage and the sampled input voltage are input to a non-inverting input terminal and an inverting input terminal of a fourth voltage-controlled current source, respectively, to generate the second compensation current. The control circuit of claim 1, wherein in the resonant peak control circuit, the sampled resonant peak voltage is input to a positive phase input terminal of the first voltage controlled current source by a first RC integrating circuit, And inputting a second reference voltage to the inverting input of the first voltage control current source to generate the first compensation current. The control circuit of claim 2, wherein in the resonant valley control circuit, the sampled resonant valley voltage is input to a positive phase input terminal of the second voltage control current source by a second RC integration circuit, And inputting a third reference voltage to the inverting input of the second voltage control current source to generate the second compensation current. The control circuit of claim 3, wherein in the resonance peak control circuit and the resonant valley control circuit, the sampled voltage is input to the first RC integration circuit and the voltage follower circuit, respectively The second RC integration circuit. A control method includes: sampling a resonance peak voltage of an electromagnetic circuit main circuit switch, and generating a first compensation current by using the sampled resonance peak voltage, and generating the first compensation current and the constant current to generate a ramp signal; integrating a current corresponding to a voltage difference between the first reference voltage and a voltage of the first voltage signal to obtain a second voltage signal, wherein the first voltage signal corresponds to a current magnitude on a main circuit of the induction cooker; The voltage of the third voltage signal as the ramp signal is compared with the voltage of the second voltage signal to output a first control signal for controlling the main circuit switch of the induction cooker; sampling the resonant valley voltage of the main circuit switch of the induction cooker, using sampling The resonant valley voltage generates a second compensation current, and generates the ramp signal by subtracting the generated second compensation current from the constant current; and comparing the sampled resonant peak voltage with the fourth reference voltage to generate a first pulse signal using the first pulse signal to the rectified input Sampling, and inputting the rectified input voltage and the sampled input voltage to the non-inverting input terminal and the inverting input terminal of the third voltage-controlled current source respectively to generate the first compensation current; The resonant valley voltage is compared with a fifth reference voltage to generate a second pulse signal, the rectified input voltage is sampled by the second pulse signal, and the rectified input voltage and the sampled input voltage are respectively The positive phase input terminal and the inverting input terminal of the fourth voltage controlled current source are input to generate the second compensation current.