JPS5880293A - Induction heating cooling device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a 1-carrying brewer.

Conventionally, as a drive circuit for this Yuzukori induction heating 11 heating device, a system using a parallel resonant circuit consisting of an induction heating coil and a resonant capacitor, and connecting a switching element in parallel to the resonant capacitor to accommodate a high frequency inverter 1fr is known. It is being In a cooker having such a configuration, the oscillation frequency of the inverter changes depending on the ON period of the switching element and the resonance period of the series resonance [Eukr]. The input to the load is adjusted by changing this frequency, particularly by controlling the on-period of the switching element. In such a frequency control system, when a multi-port configuration is used, noise generation occurs. That is, when adjacent heating ports are operated at the same time, the oscillation frequency of the inverter naturally changes due to the difference in the material of the pot being energized or the difference in the set input. The above miscellaneous f is caused by the magnetic fields from each sharpening port interfering with each other,
The crack that occurs depending on the frequency difference between the two tends to increase as the frequency difference increases. Such noise generation makes the user feel uncomfortable and is a cause of deterioration of the quality of the parts.

The present invention is this even more conflict t#1! The oscillation frequency of the inverter is kept constant, and the input can be adjusted under this condition.It is particularly useful when applied to multi-mouth M4 heating cookers; Heating 11iI
I don't have any problem even if it causes trouble to the outsiders.

In order to achieve the above object, the present invention uses a ttC single-ended pushbutton (5EPP) inverter, and the 5EPP inverter is connected to one end of the 'IIIL circuit consisting of a 1# heating coil and a resonant capacitor. is a power source with high potential @! ＃Continued. In this respect, the present invention is different from a conventional typical 5EPP inverter in which one end of its load circuit is connected to a low potential @1 (usually ground potential). A series circuit consisting of an induction heating coil and a resonant capacitor is connected in parallel to the switching block connected in antiparallel to the switching block consisting of nine diodes connected in antiparallel to the DC power supply, and the switching block placed on the potential side of the VL source. (R connect to 5KPP inverter Th
ft, and inductance elements are interposed in at least 10,000 current paths of the switching block to suppress the commutation and generated surge current from the diode to the switching block.

Figure 28g1 shows the square tfLk of the 5EPP inverter (υ) in the non-inventive embodiment, and (Ql) (Qa) are the first transistor and the second transistor, which are the first switching element and the second switching element, respectively. 1cnp
An n7 transistor is used and connected in series between the dc wrm. As the first and second switching devices, unidirectional switching devices that can conduct in only one direction are used, and in addition to transistors, they can also be used for GTO and other applications. 1. Second transistor (
Ql) (C12) is a freewheel diode connected in antiparallel to the transistor (Q, ↓) and the diode (
Di), and the switching block ttllFIJl with the transistor (Q, g) and diode (Dz) K
do. (2) is a negative '4# circuit connected in parallel to the first transformer, nv star (Ql), and the induction heating coil A/(Ll)
A resonant conductor t(Ox) made of ferrous metal is placed close to the induction heating coil A/(Ll).

FIG. 2 shows a diagram of its operation, and an on/off signal A%B is applied to each base of the first and second transistors (Qz) (Qg). First, when the second transistor (Q) is turned on by signal B, the drive current l becomes
The induction heating coil (Ll) flows through the resonant capacitor (C1) and the second transistor (Q, 2 > tl-, the second transistor (C2) turns off, the first) transistor (Q, L
) is turned on, m circulates through the induction heating coil A/(Ll), the resonant capacitor (C1) and the diode (DI).
t flow I2 flows. When this circulating current Iz becomes zero,
Load electricity lol! ! (The current flowing through 21 is reversed, and the drive current, flow 3, flows through the first transistor (Q, l), the resonant capacitor (C1) and the induction heating coil A/(Ll).

Then, the second tran s/7. (C2) is on and the first transistor (Qlo) is off, but for a while the diode (Dl), resonant capacitor (C1) and M
The circulating electric current 4 flows following conductive heating = A/(Ll). FIG. 6 shows that the on/off period ratios of the first transistor (Ql) are equal, and the second transistor (Q:
), the on-period of wJl) is controlled within the off-period of transistor (Q, l), and the load current waveforms are shown for nine cases.
The current value can be arbitrarily controlled with zero as the minimum. Since the emitter potential of the first transistor (Q, l) changes unstablely, it is difficult to control the zero duty, and a complicated circuit is required to perform this. (Qlu, emitter potential is low potential (earth potential)
Since the data is fixed to , data control is easy. Therefore, when starting oscillation, it is easy to start from a state where the on period of the second transistor (Q, i) is short.
It is possible to reduce the burden on the transistor due to surge voltages during large currents and currents am#, which are likely to occur during startup.

No. 4 shows an example circuit diagram of a dormitory according to the present invention. 31 (4) is a power supply terminal to which AC 240V is applied, A rectifier circuit that inputs AC 240v and rectifies it (Ox)
is a smoothing capacitor, and one with a small capacitance is used to improve the power factor. Therefore, its output depicts a pulsating waveform that is hardly smoothed. (DBg) inputs AC 120V,
A rectifier circuit for rectifying this T is a (C, s) smoothing capacitor with a large capacity. Therefore, its output is almost a pulsating flow close to [ffl. Capacitor (C
The terminal voltage of 8) is input to the 5EPP inverter (1), and the terminal voltage of the capacitor (C3) is input to the oscillation circuit (6).

The structure of the 5EPP inverter (1) is as described above, so a detailed explanation will be omitted. In addition, UFi heating carp fi/
The sea bream pot (R2) electromagnetically coupled to (Ll) is an inductance element, such as a toroidal core, for preventing surge current.

What is the oscillation circuit (6)? It is collected by a transformer type self-excited oscillator. (Tl) is a first transformer in which two transistors (Q, 3) (Q, 4) with the same characteristics are complementary connected to each other, and each collector winding M(ni) (ng) is connected to its primary winding. configured. Each transistor (Qs)
(Q, 4) o emitters are commonly connected and connected to a smoothing capacitor (C3).

(T1) is the second transformer, transistor (Qs) (Q
, 4), the pace winding (ns) (R4) [is used to configure the secondary winding. (R1) (Ha) constitutes the secondary winding. Transistor (Ql) is connected to (Rz) (Rg)
A resistor inserted between the base and emitter of (C4), (R
s) is the starting resistor, (Da) (Ca) (J is the diode and capacitor connected in parallel to the second transformer ('t's
) is inserted between the base winding #1A (R3) (R4) and the emitter of each transistor (Q, 1) (Q, 4)]
, a diode (Ds) is used for blocking reverse current, and a capacitor (C4) is used for increasing the switching speed. (ns) is a positive feedback winding of the first transformer (Tl), and its output is connected to the primary winding (R6) of the second transformer (T2) via a resistor (Rs). Here, the second transformer (Ti) is used up to its saturation region, which is what is called a saturation transformer. (n?)(
IIs,) is the secondary winding of lI41) lance (Tl),
The output is given to the control (BJwr (7)).The oscillation frequency of this oscillation circuit (6) is the audible frequency, that is, about 20K
Set to a value higher than HE.

In the control circuit (7), the secondary winding (R7) output of the first transformer (T1), the resistor (R4) and the capacitor (O
The first twangister (Ql
) is input between the base and emitter of the (D4) is a diode Y inserted to quickly turn on the first transistor (Ql), and (DBs) is a rectifier circuit that performs full-wave rectification of the output of two large turns all (nl!). So, it's a diode bridge. ((,5)(Oma)i
r is a smoothing capacitor, and its connection point is the secondary winding (R8
) is connected to the common terminal of each capacitor (C6) (0?
), a positive and negative pressure of 2 is obtained as the common terminal sound center. This common terminal is grounded together with the emitter of the second transistor (Q, g). (Q, 6) (C6) is
A pair of transistors forming a complementary circuit wrt, with a capacitor (
The positive terminal voltage of the transistor (C6) is applied, and the transistor (
The negative terminal voltage of the capacitor (C?) is applied to the collector of C6).

The emitters of both transformers Vstar (Q, i (Q, 6)
Connected to the base of transistor (Ql).

(MY) A monostable multivibrator that inputs the output tube of the secondary winding (R8) and outputs a low-level signal for a certain period of time at the same time as the input m rises. The output period is set and arbitrarily set. (Q?) This is a transistor that is turned off when the above low level signal is applied to the base, and the collector is a resistor (R6) connected to the base of the transistor (Q-) (Qa).
)' to the positive terminal of the capacitor t(Os), and its emitter is connected to the negative terminal of the capacitor (09). (Rg) (C9) is the capacitor (C11) (
C? ) is connected to one end of this capacitor (09) (D terminal voltage is connected to the transistor (Q-
) is added to the base of

A variable resistor ('VR) is connected in parallel between the emitter φ and V of the transistor (Ql), and the transistor (C
8) is in the on state, the variable resistor (VR) is shorted. When starting mchi inverter oscillation, capacitor (C9)
For a short period of time until it reaches a certain potential, the transistor (C
8) Turn on, so the variable resistor (VR) is shorted, and the output pulse width of the monostable multivibrator (MY) is shortened.

Next, the operation of the above configuration will be explained. First, the oscillation Fil
&Let's talk about (6). When the transistor (QS) becomes conductive due to the DC voltage obtained at the terminal of the smoothing capacitor (C3), a current starts to flow between its collector and emitter, and a positive feedback winding m(
An induced voltage is generated in the second transformer (Ta) through the primary winding (R6) of the second transformer (Ta).
The winding (R3) K further generates an induced voltage at xJt(Q,s)C)/<-/. This voltage causes a transistor (C
3) produces a positive feedback °1, and with sufficient base current, the conduction
The state of koji becomes complete. The current flowing through the resistor (R3) increases linearly due to the primary inductance of the second transformer (Tg') and reaches saturation. This is j82
The current in the primary IIl increases suddenly, the voltage drop across the resistor (Rs) increases, and the voltage drop across the primary winding (R6) of the second transformer (Ta) increases rapidly. The feedback voltage decreases.

Then, the voltage of the capacitor (C4) is applied to the base of the transistor (Q, I) with mW characteristics as shown in the figure, the transistor (Q, 8> is cuffed off, and the transistor (C4) starts to conduct electricity. The direction opposite to the previous time [1j
When the ll- event occurs, the transistor (Qs) is turned off and the transistor (C4) is turned on. 2nd transformer (Tg
The primary current of the transistor (Ql
) turns on in the same way as when transistor (C4) turns on. Self-oscillation continues in this manner. 1
Two collector windings (nl) (n
B) secondary winding (nv) (na)[1
Since they are m-coupled, transistors (Q, S) ~ (C4
), square wave pulses are alternately obtained in the secondary winding (n?) (R8) according to the on/off state of the secondary winding (n?) (R8). FIG. 5 AK shows this waveform, and when the transistor (Q, 3) is on, it is at a high potential level, and when it is off, it is at a low potential level.

An inverted signal of waveform A is obtained at the two-large turn k(nB) output. This output signal consists of rectifier circuits (DBs) and smoothing capacitors (Ca) (Oy)? It is rectified and smoothed through r and is supplied with the drive voltage of complementary transistors (Q, 5) (Q, 6).

In addition, in the case of 100% duty, where the monostable multivibrator (MY) operates in synchronization with the rise of the above output and outputs a low potential signal for a period set by the variable resistor (vR), and - Waveforms c and d show the monostable multivibrator (MV) output when the T is lowered to this extent,
During this time, the transistor (Q, ?) is off, but then the transistor (C5) is on and the transistor (Q, 6) is off, so the second transistor (C2) is on.

In the figure, waveform B represents the base current of the first transistor (Ql), and waveform D%D' represents the base current of the corresponding second transistor (Q, J).

In the induction heating cooker of the present invention, the first transistor (Ql)
The on/off period of the second transistor (Cta) is fixed at a 1:1 ratio, and the on/off period of the second transistor (Cta) varies from 0% to 10% within the off period of the first transistor (Ql).
It can be arbitrarily varied up to 0%, and thereby the input to the tuning chain can be freely set from several watts to about 1500 watts. Note that the maximum value of the input O is determined by the withstand voltage of the switching element or the current capacity cape that supplies power to a general household. The control signal of the monostable multivibrator (MY) is the oscillation time wr<
), the second transistor (1
) can be made to match the operation timing of the first transistor (Ql).

In addition, two complementary-connected transistors (Q, 6) (C6) drive the second transistor (Q, a).
) is obtained from the output 41k of the first transformer (T1), so there is no need for a power transformer, which is normally used to obtain power for the control circuit.

Next, the function of the toroidal core (R2) will be explained. In the heating steady state line, Figs. 1 and 2 show the SEPP inverter (υ) shown in 1.
The impedance (hereinafter referred to as equivalent impedance) of heated carp A/(LL) and cooking-0) and the resonance capacitor (
The resonance frequency f with C1) is f< with respect to the button vibration frequency @fo.
The relationship is fo, and the freewheel diode (
No abnormality occurs when current is commutated from the second transistor (Da) to the second transistor (Q). However, the 6th is 4 as shown in 1.
When heating a cooking pot, such as an aluminum steel wire, which has a small value impedance, its resonant frequency f becomes larger than the oscillation frequency fo (f>f).

), the load current has a leading phase. When such a current phase occurs, the freewheel diode (Da)
When commutating 1/ to the transistor (Qg), a surge current as shown in FIG. 7 is generated.

In the figure, waveform A is the collector current waveform of the second transistor (Q, jI), and waveform B is the collector current waveform of the second transistor (Q, jI), and waveform B is the collector current waveform of the second transistor (Q, jI).
These surges 111 showing the current waveform of Da) are also several times larger than the beef value of negative toughness current, and cause noise generation and switching transistor deterioration. The cause of the surge current generation is based on the pipe line 8-. The same figure shows the waveforms of the base voltage A and base current B of the transistor (Q). In order to increase the switching speed Mk of the transistor (Q), it is normal to apply a positive or negative voltage to the base. Therefore, it is in the on state. When the base voltage of a certain transistor (Q) is reversed from positive to negative to shut it off, l flows due to a surge current with a steep peak.

This current (112U) is a current generated due to the instantaneous discharge of nine charges accumulated in the base and emitter of the fungistor (Q). Note that the current line 11 in the figure is the base current that flows when the transistor (Q) is in the on-state line.Such a surge current is generated in the same way even if there is a freewheel diode (Da).

In this embodiment, a second transistor (C2) and a diode are used to absorb such surge current.

A small toroidal core (La) is inserted into the current path (Da). This toroidal core (La CLII) provides inductance to the current path, which acts to suppress sudden changes in current.
) By inserting V, the surge current can be suppressed by approximately 1/104C. In addition to the above, the insertion position of the toroidal core (La) may be narrowed in the current path of the first transistor (Ql) and freewheel diode (Dl).
Furthermore, other inductance elements can be used instead of the toroidal core.

As described above, the induction heating piece heater of the present invention has a load circuit provided in parallel to the first switching element located on the high potential side of the 5EPP inverter, and a second switching element connected to the low potential side fixed at a constant value. Since the switching element data is controlled and the input to the load is adjusted, the control circuit is much simpler than the control of the first switching element, where the voltage between the terminals is unstable. be done.

According to the invention, since the oscillation mantissa of the inverter is always constant, even if the heating rotors are installed adjacent to each other,
There is no risk of noise occurring due to frequency differences, and the user can comfortably perform cooking operations. Furthermore, inverter oscillation 1111#I! , it can be configured to automatically start heating from a low input position.
The excessive current and excessive voltage that occur during startup can be prevented, and the load on the switching elements can be reduced.

According to the present invention, the switching elements and diodes can be protected by providing an inductance element that prevents generation of a surge current that momentarily flows through the switching block constituting the 5EPP inverter.

[Brief explanation of the drawing]

FIG. 1 is a main circuit diagram for explaining an embodiment of the present invention,
Figures 2 and 3 are waveform diagrams on the same side, and Figure 4 is the entire circuit.
, No. 5- is a descending waveform diagram, and FIGS. 6-8 are waveform diagrams explaining the action of the inductance element. (1)--SEPP inverter, (6)...
・-Oscillation circuit, (71-...control circuit. ml ['4. Figure 3 Shoulder diagram Figure 8

Claims (1)

[Claims] 1. A switching block consisting of a 41-way switching screen and a diode connected in parallel with it in the opposite direction,
A pair of DC power supplies are connected in series, and a negative circulation circuit consisting of an induction heating coil and a resonant capacitor is connected in parallel to the switching block of the high potential power supply, and the pair of switching blocks are alternately made conductive. m2J1! is an induction heating cooker in which alternating TFK is passed through a heating coil, characterized in that an inductance element for absorbing surge current is interposed in at least one current path of the pair of switching blocks. Heating cooker.