JPH04196085A - Electromagnetic cooking device - Google Patents

Abstract

PURPOSE:To make cost reduction with circuit integration facilitated and the number of parts reduced, by driving a switching element when the voltage of the switching element side is changed from a falling gradient to a rising gradient. CONSTITUTION:A gradient detection circuit 14 makes detection as to whether the waveform of a collector voltage has a rising gradient or a falling gradient and consequently outputs a low signal (M) in the case of a rising gradient and a high signal (M) in the case of a falling gradient, and an up-down counter IC11, IC12 makes up-counting operation when the signal (M) is low. And when the signal (M) is high, the up-down counter IC11, IC12 makes down-counting operation to output the count value (P), and a digital comparator IC14, IC15 detects the timing of driving a switching element by continuing the counting operation up to a reference value set up in advance when the counting operation is changed from up-counting to down-counting. Accordingly, the delay of driving timing due to the delay of circuit operation such as operation delay time of the switching element is not produced. Thereby, the circuit integration is facilitated and the number of parts is reduced, so that the cost reduction may be made.

Description

[Detailed description of the invention] [Field of industrial use]

The present invention relates to an electromagnetic cooker.

[Conventional technology]

FIG. 6 is an external view of a general electromagnetic cooker. This electromagnetic cooker places a pot etc. (not shown) made of ferromagnetic material on the top plate H, and generates a fluctuating magnetic field in the internal coil to generate an induced current in the pot etc. The food to be cooked is heated by Joule heat generated by the induced current. The intensity of the heating can be adjusted by sliding the heating knob 2 left and right. FIG. 7 is a block diagram showing the circuit configuration of a conventional electromagnetic cooker. This electromagnetic cooker uses commercial power supply 3 and Hikozu F1 varistor V.
A rectifier diode DI is connected through R8, a noise prevention capacitor CI, and a current transformer C1 for input terminal detection, and a choke coil L1 and smoothing capacitor C2 are connected to this rectifier diode I) and its secondary side. ] It is designed to rectify and smooth the commercial power grid. Then, this rectified and smoothed voltage is applied to the power transistor Q1.
The power is supplied to a resonant circuit consisting of heating coils 1 and 2 and a resonant capacitor C3. A drive pulse of a predetermined time width generated by a drive pulse generation circuit 8 is supplied to the base of the power transistor Q1 via a drive circuit 7. The drive pulse generation circuit 8 receives the timing signal generated by the timing signal generation circuit 9 based on the voltage induced in the secondary coil L5 wound in connection with the heating coil L2.
Generate the above drive pulse. The time width of this drive pulse is determined by the control circuit I2 based on the resistance value of the resistor 42 of the slide VR4 interlocked with the heating knob 2 in FIG.
Control is performed based on the current value detected by CT+ via the CTI rectifier circuit 10 and the current value detected by CT2 via the CT2 rectifier circuit II. Turn the heating knob 2 above.
When the switch 41 in the slide resistor 4 connected to the power supply circuit 13 is set to the "off" position, the switch 41 in the slide resistor 4 connected to the power supply circuit 13 becomes "open", the generation of drive pulses from the drive pulse generation circuit 8 is stopped, and heating is stopped. Further, the exhaust fan motor 5 connected to the power supply circuit 13 is also stopped. Fig. 8 is a circuit diagram specifically showing the main parts of the circuit shown in Fig. 7. In this Fig. 8, the TI is a power transformer for the control circuit, D20 is a rectifier diode for the control circuit, C20
is a smoothing capacitor for control circuits. Also, R23, R
22 is a voltage dividing resistor, D9. D8 is a clamp diode,
ICI, IC2゜IC3 is analog comparator, C1
8, CI2 is a positive feedback capacitor, R2+, RI2 is a positive feedback resistor, R20, R16, R]9 is a load resistor, C1
7 is a coupling capacitor. Further, R1+ is a charging resistor, D4 is a discharging diode, CI5 is a charging capacitor, and R17, R13, R33, and R26 are voltage dividing resistors. In addition, R7゜R5 and R4 of the drive circuit 7 are resistances for stabilizing operation, Q5 and Q2 are transistors for amplification, and R8
is the base current limiting resistor, D3 is the diode, R6, r(
10 is a bias resistor, C4 is a speed-up capacitor, D2 is a reverse voltage protection diode, Q4. Q3 is a transistor for discharging accumulated charges. In the above configuration, by turning on the power now,
A first drive pulse is supplied to Ql by the action of an initial reset circuit (not shown), the collector and emitter of Ql are brought into conduction, and current flows through L2. This current becomes an oscillating current due to L2 and the resonant capacitor C3. FIG. 9A shows the collector voltage of Ql. This collector voltage varies based on a 140V line that is approximately equal to the peak value of the electrohydraulic voltage. That is, by turning on Ql, 14
It rapidly drops to below 0V, gradually rises as Ql is turned off, exceeds the 140v line, and then attempts to converge to 140V, but drops again when Ql is turned on, and the same fluctuations repeat thereafter. A fluctuating magnetic field is generated by the oscillating current flowing through the above-mentioned 2, and an induced current is generated in the ferromagnetic material 6 (Fig. 7) such as a pot placed on the top plate 1, and the Joule heat generated by the induced current causes the food to be cooked. Heating things. The voltage induced in R5 by the above-mentioned fluctuating magnetic field is applied to the IC through the voltage division between R23 and R22 of the timing signal generation circuit 9.
Applied to the non-inverting input of I. At this time, since the non-inverting input of the ICI is clamped to Gnd by D9, the waveform becomes as shown in FIG. 9(B). Further, since the inverting input of the ICI is fixed to Gnd, the output waveform of the ICI shown in (C) becomes Low at the point attached to Gndn of the waveform (B). The above output (C) passes through CI7 and becomes the waveform (D)
and is supplied to the oscillation circuit composed of IC2. The non-inverting input of this IC2 is fixed to the voltage divided by R17 and RI3, but positive feedback is applied by RI2. On the other hand, the inverting input of IC2 is connected to C15 via R11 from the output terminal.
Since the voltage is charged to , a sawtooth wave as shown in (E) is oscillated as a whole. The sawtooth wave (E) is supplied to an inverting input of a drive pulse generation circuit 8 composed of an IC3. Since the non-inverting input of lC3 is fixed at a predetermined value (F), it generates a pulse (G) with a time width corresponding to that value. Here, (F
) is shown as a divided voltage by R26 and R33, but in reality, the control circuit 12 shown in FIG.
Control is performed based on the resistance value of C'F+ and the current value detected via CT2. This pulse (G) is supplied to the base of Ql through the drive circuit 7 composed of Q2 to Q5, the collector and emitter of Ql are brought into conduction, and thereafter the next cycle begins and the same operation as above is repeated.

[Problem to be solved by the invention]

By the way, the conventional electromagnetic cooker consists of a circuit that detects the timing for driving the power transistor Q1 and a circuit that generates a timing signal based on the detection result (L5 and timing signal generation circuit 9 in FIG. 7). ) is composed of analog circuits, so IC
The problem was that it was difficult to visualize and design. In addition, since the device becomes operational only after the feedback voltage is manually applied, the operation tends to be delayed, so all circuits are required to operate at high speed. On the other hand, it has been difficult to meet demands for cost reduction, such as requiring a large number of capacitors and resistors, and requiring a secondary coil for the heating coil due to timing accuracy requirements. In addition, Fig. 10 shows the Vce waveform when the power transistor Q+ is driven only in the - period, but since the amplitude decreases from the time the drive is stopped, L2 and C
It can be seen that the resonance waveform No. 3 performs damped vibration. The degree of this attenuation varies depending on the degree of energy absorption of the pot or the like placed on the load. So constant thread:
There is a problem in that a simple comparator with a level cannot determine the drive timing of Ql. Therefore, an object of the present invention is to digitize a circuit that detects the timing for driving the power transistor Ql low and a circuit that generates a timing signal based on the detection result. An object of the present invention is to provide an electromagnetic cooker which eliminates the problem of spots.

[Means to solve the problem]

In order to achieve the above object, a first invention applies a DC voltage to a resonant circuit consisting of a coil and a capacitor via a switching element, and generates a fluctuating magnetic field in the coil by driving the switching element, While heating the ferromagnetic object placed on the top plate, a periodic signal is generated that alternately indicates rising and falling periods of the voltage on the two-part switching element side of the resonant circuit. ,
The drive timing of the switching element is detected based on the periodic signal, and the switching element is driven at the detected drive timing, and the conduction time of the two-part switching element is determined based on the heating intensity set by the heating intensity setting means. In the electromagnetic cooker configured to control the voltage on the switching element side of the resonant circuit, it is detected whether the voltage is on a monthly slope or a downward slope, and when the voltage is on the upward slope, either high or low is set. It is equipped with a slope detection circuit that outputs one signal and outputs the other signal of either low or high when the slope is downward, and when the voltage on the two-part switching element side changes from a downward slope to an upward slope. The present invention is characterized in that the switching element described above is driven. Further, in a second invention, a DC voltage is applied to a resonant circuit consisting of a coil and a capacitor via a switching element, and the switching element is driven to generate a varying magnetic field in the coil, and the coil is mounted on the top plate. While heating a placed ferromagnetic object to be heated, a periodic signal is generated that alternately indicates rising and falling periods of the voltage on the switching element side of the resonant circuit, and based on the periodic signal.
Detecting the driving timing of the switching element described above, and using the detected driving timing to drive the two-part switching element, the conduction time of the switching element - and h is controlled based on the heating intensity set by the heating intensity setting means. In an electromagnetic cooker that is set to The count value of the counter and the two-legged up/down counter is compared with the reference value, and when the up/down counter counts up and reaches the reference value, either high or low. and a digital comparator that outputs either a low or high signal when the up-down counter counts down to a reference value, and the up-down counter counts down and outputs the other signal, either low or high. The third invention is characterized in that the switching element is driven when the count reaches the reference value.Furthermore, the third invention is characterized in that a DC voltage is applied to a resonant circuit consisting of a coil and a capacitor via the switching element. By driving the switching element, a varying magnetic field is generated in the coil to heat the ferromagnetic object placed on the top plate, while the voltage on the switching element side of the resonant circuit is generates a periodic signal that alternately indicates a rising period and a falling period of In an electromagnetic cooker in which time is controlled based on a heating intensity set by a heating intensity setting means, it is detected whether the voltage on the switching element side of the resonant circuit is on an upward slope or a downward slope, and a slope detection circuit that outputs either a high or low signal when the slope is on, and outputs the other high or low signal when the slope is downward; and a slope detection circuit that receives the output signal of the slope detection circuit. an up-down counter that counts up when the voltage on the switching element side of the resonant circuit is on a double slope and counts down when it has a down slope, and sets the count value counted by the up-down counter as a reference value. When the up/down counter counts up and reaches the reference value, it outputs either a high or low signal, and the up/down counter counts down until the reference value is reached. and a digital comparator that outputs the other signal of either low or high when the up/down counter counts down to the reference value, and drives the switching element when the up/down counter counts down to the reference value. There is.

[Effect]

In the first invention, the slope detection circuit detects whether the voltage on the switching element side of the resonant circuit consisting of a coil and a capacitor is on an upward slope or a downward slope, and when it is on an upward slope, the voltage is high or high. Outputs either a low signal, and outputs the other signal, either high or low, when the slope is downward, and when the voltage on the switching element side changes from a downward slope to an upward slope, the switching element to drive. The above-mentioned slope detection circuit can be easily integrated into an IC, and unlike conventional timing signal generation circuits, it requires almost no capacitors or resistors, and also does not require a secondary coil, making it possible to significantly reduce costs. . Further, in the second invention, the up/down counter receives a periodic signal that alternately indicates rising periods and falling periods of the voltage on the switching element side of the resonant circuit, and while the periodic signal represents the rising period, The digital comparator compares the count value counted by the up/down counter with a reference value (predetermined depending on the model, circuit configuration, parts used, etc.). When the up/down counter counts up to the reference value, it outputs either a high or low signal, and when the up/down counter counts down to the reference value, it outputs a low or high signal. Either one of the other signals is output, and when the up/down counter counts down to the reference value, the switching element is driven. In this way, since the up/down counter counts down to the reference value and detects the drive timing of the switching element, it is possible to prevent the drive timing from being affected by circuit operation delays such as the operation delay time of the switching element. There will be no delays. Further, the up/down counter, digital comparator, etc. can be easily integrated into ICs, and require almost no capacitors or resistors as in the conventional example, making it possible to significantly reduce costs. Further, in the third invention, the slope detection circuit detects whether the voltage on the switching element side of the resonant circuit including the coil and the capacitor is on an upward slope or a downward slope,
The up-down counter outputs either a high or low signal when the slope is up, and outputs the other signal, high or low when the slope is down. In response to this, if the voltage on the switching element side of the resonant circuit is on an upward slope, it counts up, and when it is on a downward slope, it counts up).
Go down. Then, the dental comparator compares the count value counted by the two-leg up-down counter with the reference value, and when the above-mentioned up-down counter counts up and counts the two-leg reference value, it becomes high or low. Either one of the signals is output, and when the up/down counter counts down to the base value, the other signal of low or high is output. Then, when the up-down counter counts down to the reference value, the switching element is driven. Therefore, the effect of the second invention can be provided in addition to the effect of the first invention, and a significant cost reduction can be achieved without causing a delay in drive timing.

【Example】

The present invention will be described in detail below with reference to illustrated embodiments. FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention. The electromagnetic cooker of this embodiment is different from the conventional electromagnetic cooker shown in FIG. 75 is canceled and the voltage of the resonant circuit is detected directly without going through the secondary coil T, 5 J:
The other configurations are the same as the conventional example. Identical components are given the same reference numerals and their explanations will be omitted. FIG. 2 is a detailed circuit diagram of the inclination detection circuit 14. In Fig. 2, IC4, rC5, IC6 are buffer amplifiers, IC7 is an analog comparator, IC
8 is the D7 lip '7 U knob, IC9 and ICl0 are analog switches, Cl00. Cl0I is a holding capacitor. The above ICl0. Cl0I and IC6 and IC
9, C100 and IC5 each constitute a sample and hold circuit. This slope detection circuit includes (A), (H), (r
). The voltages and signals shown in (, J) are input. (A) is the power transistor Q input to the non-inverting input of IC4
The collector voltage is 1, (11) is the sample clock that drives IC9, (I) is the sample clock that drives ICl0, and (, ■) is the latch pulse input to C8. The collector voltage waveform (A) undergoes impedance conversion by the IC 4, and supplies voltage to the two sets of sample bold circuits. On the other hand, when the level of the sample clock (g) becomes high (I (high)), IC9 becomes conductive and charges the (A) waveform to C100. After the sampling time has elapsed, (r[) becomes low (Low). Next to IC9
is cut off, and the voltage charged in C100 is output from IC5. ICI O, CI 01. The sample hold circuit configured by IC6 performs the same operation as above using the sample clock (D) with a time difference from the sample clock (T-1).As a result, two types of sambling waveforms (K ), (L) are generated, their waveforms are compared at +07, and a latch pulse is generated at IC8.
- Distinguish whether the slope is uphill or downhill by latching. Then, the output of IC8 (M
) is set low when the slope is up, and set high when the slope is down. FIG. 4 is a specific circuit diagram of the drive timing detection circuit I5, and FIG. 5 is a diagram showing waveforms of each part of this drive timing detection circuit. In FIG. 4, ICI+, IC+2 are up/down counters, IC+3 is ant game), IC+4. IC
l3 is a digital comparator. Further, the signal (N) is a signal from an initial reset circuit (not shown) and a signal synchronized with the power transistor drive waveform of the immediately previous cycle, and is used to reset the counter. Signal (0) is a clock signal for count up or count down. Further, the output (M) of the slope detection circuit controls the counts of ICI1 and IC12, and low is an up count and high is a down count. In addition, (P) is the count value of the counter and is 8-bit data expressed in hexadecimal, (Q) is the reference value given to the comparator (30 in hexadecimal in this case), and (R) is the drive output of the comparator. It is a timing signal. The above reference value is a value determined in advance depending on the model, circuit configuration, used parts, etc. Further, the output setting value is set by the control circuit 12 shown in FIG. It is designed to give. Now, if the counter ICIIjCI2 is reset with a signal synchronized with the power transistor drive waveform of the immediately previous cycle, since the subsequently manually inputted signal (M) is low, first a count value corresponding to the time of the upward slope is obtained. Here we get 81 in hexadecimal. After that, the collector voltage waveform becomes downwardly sloped and (M) becomes high, so a down count is performed from the two-digit value. Digital comparator IC] 4. , IC15
” Output from two-legged counter TCII, ICI2 (P)
is compared with the comparison data (Q), and when the count value exceeds the above reference value, the output (R
) is set high, and when the count value after the countdown is equal to the reference value, the output (r() is set low.The drive pulse generating circuit 8 shown in FIG. In response to the output (R) of the output (R), the drive pulse counter starts counting when the output (R) falls.This drive pulse counter counts the output setting value given by the control circuit 12. The drive pulse generation circuit 8 is configured so that the output is low for only a period of time.The drive pulse generation circuit 8 sends a drive signal to the Q+ via the drive circuit 7 to make the power transistor Q1 conductive only while the output of the drive pulse counter is low. In this way, the slope slope circuit 14 detects whether the waveform of the collector voltage is on an upward slope or a downward slope, and outputs a low signal when the waveform is on an upward slope, and a high signal when the waveform is on a downward slope. The up/down counter IcII,
IC12 counts up when the signal (M) is low, counts down when it is high, outputs the count value (P), and outputs the count value (P) to digital comparators IC14 and IC12.
Since the driving timing of the switching element is detected by counting up to a preset reference value when l3 starts counting up and then moves to the countdown, there is no delay in circuit operation such as the operation delay time of the switching element. Therefore, there is no delay in drive timing due to In addition, the above-mentioned slope detection circuit 14, up/down counter T
CII, ICI2, digital comparator IC14, I
Cl3 can be integrated into an IC and requires almost no capacitors or resistors, and also does not require a secondary coil.
Compared to the conventional example, the design is easier and costs can be significantly reduced.

【Effect of the invention】

As is clear from the above, the electromagnetic cooker of the first invention is
It detects whether the voltage on the switching element side of the resonant circuit consisting of a coil and a capacitor is on an upward slope or a downward slope, and outputs either a high or low signal when the voltage is on an upward slope. The device is equipped with a slope detection circuit that outputs either a high or low signal when the slope is on the slope, and drives the switching element when the voltage on the bipedal switching element side changes from a downward slope to an upward slope. This makes it easy to integrate the circuit into an IC, reducing the number of parts, and eliminating the need for a secondary coil, resulting in significant cost reductions. Further, the electromagnetic cooker of the second invention receives a periodic signal that alternately indicates a rising period and a falling period of the voltage on the switching element side of the resonant circuit consisting of a coil and a capacitor, and the periodic signal represents the rising period. The up-down counter counts up while the period is in progress, and counts down while it represents the falling period, and the count value counted by the up-down counter is compared with the reference value, and the two-leg up-down counter counts up. A digital device that outputs either a high or low signal when counting the reference value, and outputs the other signal, low or high, when the up-down counter counts down to the reference value. Equipped with a comparator,
- Since the switching element is driven when the analog counter counts down to the reference value, there is a delay in drive timing due to delay in circuit operation such as operation delay time of the switching element. Never. Further, the up/down counter, digital comparator, etc. can be easily integrated into ICs, and the number of parts can be reduced, making it possible to significantly reduce costs. Further, the electromagnetic cooker of the third invention detects whether the voltage on the switching element side of the resonant circuit consisting of a coil and a capacitor is on an upward slope or a downward slope, and when the voltage is on an upward slope, it is high or low. A slope detection circuit that outputs either one of the signals, and outputs the other signal of either high or low when the slope is downward, and the output signal of the slope detection circuit is 1. An up/down counter that counts up when the voltage on the switching element side of the resonant circuit is on an upward slope and counts down when it is on a downward slope, and the count value counted by the up/down counter in 5. Compare with the above value,
When the up-down counter counts up to the above reference value, it outputs either a high or low signal, and when the up-down counter counts down to the above reference value, it outputs a low signal. or a digital comparator that outputs the other signal of either high or high, and when the up/down counter counts down to the reference value, the switching element is driven. In addition to the effect of the above, the effect of the second invention can be provided, and it is possible to perform a -layer width = 1 strikedown without causing a delay in drive timing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention, FIG. 2 is a specific circuit diagram of the tilt detection circuit of the embodiment described above, and FIG. 3 shows the various parts of FIG. 2. 4 is a specific circuit diagram of the drive timing detection circuit according to the above embodiment, FIG. 5 is a diagram illustrating the operation of the bipedal drive timing detection circuit, and FIG. External view of the cooker, No. 7
The figure is a block diagram showing the circuit configuration of the conventional example, Figure 8 is a specific circuit diagram of the main parts of the above conventional example, Figure 9 is a waveform diagram of each part of Figure 8, and Figure 10 is the waveform diagram of the above example. FIG. 6 is a diagram showing a Vce waveform when the power transistor is driven for only one period. 4...Slide VR16...Ferromagnetic pot, 7...
・Drive circuit, 8...Drive pulse generation circuit, I2
・・Control circuit, 14・Inclination detection circuit, +5・・Drive timing detection circuit, L2 ・Heating coil, C3 resonance capacitor, Ql Power transistor, ICI IjCI
2- Up/down counter, IC+4. , ICI5・
・Digital comparator.

Claims (3)

[Claims] (1) A DC voltage is applied to a resonant circuit consisting of a coil and a capacitor via a switching element, and by driving the switching element, a fluctuating magnetic field is generated in the coil, and the ferromagnetic material placed on the top plate is While heating the object to be heated in the body, a periodic signal is generated that alternately indicates rising and falling periods of the voltage on the switching element side of the resonant circuit, and the drive timing of the switching element is detected based on the periodic signal. and an electromagnetic cooker configured to drive the switching element at the detected drive timing and control the conduction time of the switching element based on a heating intensity set by a heating intensity setting means, wherein the switching element of the resonant circuit It detects whether the side voltage is on an upward slope or a downward slope, and outputs either a high or low signal when it is on an upward slope, and either low or high when it is on a downward slope. An electromagnetic cooker comprising: a slope detection circuit that outputs the other signal; and the switching element is driven when the voltage on the switching element side changes from a downward slope to an upward slope. (2) A DC voltage is applied to a resonant circuit consisting of a coil and a capacitor via a switching element, and by driving the switching element, a fluctuating magnetic field is generated in the coil, and the ferromagnetic material placed on the top plate is While heating the object to be heated in the body, a periodic signal is generated that alternately indicates rising and falling periods of the voltage on the switching element side of the resonant circuit, and the drive timing of the switching element is detected based on the periodic signal. In an electromagnetic cooker, the switching element is driven at the detected drive timing, and the conduction time of the switching element is controlled based on the heating intensity setting of the heating intensity setting means, in response to the periodic signal, An up/down counter that counts up while the periodic signal represents a rising period and counts down while the periodic signal represents a falling period, and compares the count value counted by the up/down counter with a reference value. When the up/down counter counts up to the reference value, it outputs either a high or low signal, and when the up/down counter counts down to the reference value, it outputs a low or low signal. An electromagnetic cooker comprising: a digital comparator that outputs either a high signal; and the switching element is driven when the up/down counter counts down to the reference value. (3) A DC voltage is applied to a resonant circuit consisting of a coil and a capacitor via a switching element, and by driving the switching element, a fluctuating magnetic field is generated in the coil, and the ferromagnetic material placed on the top plate is While heating the object to be heated in the body, a periodic signal is generated that alternately indicates rising and falling periods of the voltage on the switching element side of the resonant circuit, and the drive timing of the switching element is detected based on the periodic signal. and an electromagnetic cooker configured to drive the switching element at the detected drive timing and control the conduction time of the switching element based on a heating intensity set by a heating intensity setting means, wherein the switching element of the resonant circuit It detects whether the voltage on the side is on an upward slope or a downward slope, and outputs either a high or low signal when it is on an upward slope, and either high or low when it is on a downward slope. a slope detection circuit that outputs the other signal; and upon receiving the output signal of the slope detection circuit, counts up when the voltage on the switching element side of the resonant circuit has an upward slope, and counts down when it has a downward slope. The count value counted by the up-down counter is compared with a reference value, and when the up-down counter counts up and reaches the reference value, either a high or low signal is generated. and a digital comparator that outputs either a low or high signal when the up-down counter counts down to the reference value, and the up-down counter counts down to the reference value. An electromagnetic cooker, characterized in that the switching element is driven when the count is counted.