JPH061714B2 - Multi Induction Cooker - Google Patents

Description

The present invention relates to a multi-port induction heating cooker.

An induction heating cooker supplies a high-frequency current of about 20 KHz or more to an induction heating coil and induction-heats a load that is electromagnetically coupled to this coil, that is, a cooking pot. An inverter that generates a high-frequency current is a material of the load. It is customary for the oscillation frequency to change due to. Therefore, when a plurality of heating ports in a multi-cooking cooker are simultaneously operated, the magnetic fields generated by the coils interfere with each other, resulting in a noise corresponding to the frequency difference. To deal with this, S
A heating drive system in which the oscillation frequency is made constant by using an EPP inverter has already been proposed. Usually SEP
A multi-port induction heating cooker using a P inverter has a configuration in which power is supplied to a plurality of SEPP inverters from a common power circuit. If a plurality of SEPP inverters are operated in synchronism with such a configuration, the current flowing out from the filter capacitor, which is one component in the power supply circuit, is doubled by the operating heating port as compared with the case of single port heating. The allowable ripple current is required to be abnormally large.

The present invention has been made in view of the above circumstances, and is an improvement in which the operation timings of a plurality of SEPP inverters are shifted from each other and the outflow currents of the filter capacitors are leveled.

An embodiment will be described below with reference to the drawings. In the example, 2
This is the case with a mouth induction heating cooker. In Figure 1, (1)
Is an AC power supply, (2) is a rectifier circuit, (CH) is a yoke coil, and (C ₁ ) is a filter capacitor. The filter capacitor (C ₁ ) is a small-capacity capacitor that has almost no smoothing effect, and mainly prevents high-frequency current from leaking to the AC power supply side.
Reference numerals (3 ₁ ) and (3 ₂ ) denote first and second heating ports connected in parallel between the terminals of the capacitor (C ₁ ), and SEPPs having the same configuration.
It consists of an inverter. Explaining the configuration of the first heating port (3 ₁ ), (Q ₁ ) and (Q ₂ ) are _first and _second that function as a pair of switching elements connected in series between power sources.
Transistors, (D ₁ ) (D ₂ ) are diodes connected in antiparallel between the emitter and collector of the first and second transistors (Q ₁ ) (Q ₂ ), respectively, and (4) is the first transistor (Q ₁ ) Is a series resonance circuit including an induction heating coil (L) and a resonance capacitor (C ₂ ) connected in parallel. The first and second transistors (Q ₁ ) (Q ₂ ) are alternately turned on by drive signals a, b, c, d generated from a drive circuit (5) described later. In addition, S constituting the second heating port (3 ₂ )
First and second transistors (Q _{1 '} ) of EPP inverter
Drive signals a ', b', c ', d'are applied to (Q _2' ).

The drive circuit (5) consists of a 2-transformer self-excited oscillator,
The terminal voltage Vcc of the filter capacitor (C ₁ ) is supplied as driving power through the diode (D ₃ ). (T
₁ ) is a first transformer in which two transistors (Q ₃ ) (Q ₄ ) having the same characteristics are complementarily connected to each other, and each collector winding (n ₁ ) (n ₂ ) constitutes its primary winding. It The emitters of the transistors (Q ₃ ) (Q ₄ ) are commonly connected and connected to the intermediate point of the primary winding through the smoothing capacitor (C ₃ ), and at the same time, the power supply voltage is supplied through the diode (D ₃ ). It is connected to the Vcc terminal. (T ₂ ) is a second transformer, the secondary winding of which is formed by the base windings (n ₃ ) (n ₄ ) of the transistors (Q ₃ ) (Q ₄ ). (R
₁ ) (R ₂ ) is a resistance inserted between the base and emitter of the transistors (Q ₃ ) (Q ₄ ), (R _S ) is a starting resistance,
(D ₄ ) and (C ₄ ) are diodes and capacitors connected in parallel, and are the base winding (n ₃ ) of the second transformer (T ₂ ).
(N ₄ ) is inserted between the emitters of the transistors (Q ₃ ) and (Q ₄ ), the diode (D ₄ ) is for blocking backflow, and the capacitor (C ₄ ) is for increasing the switching speed. used. (N ₅ ) is a positive feedback winding of the first transformer (T ₁ ), and its output is connected to the primary winding (n ₆ ) of the second transformer (T ₂ ) via a resistor (R ₃ ). . Here, the second transformer (T ₂ ) is a so-called saturation transformer used up to its saturation region.
(N ₇ ) (n ₈ ) (n ₉ ) (n ₁₀ ) are secondary windings of the first transformer (T ₁ ), and the windings (n ₇ ) (n ₈ ) to
The driving signals a, b, c, d of the heating port (3 ₁ ) are also transferred from the windings (n ₉ ) (n ₁₀ ) to the driving signals a ′, b ′, c ′ of the second heating port (3 ₂ ). d'is output respectively. These outputs are output after being subjected to overlap prevention processing through a delay circuit composed of a resistor (R ₄ ) and a capacitor (C ₅ ). Here, the winding directions of the windings (n ₉ ) (n ₁₀ ) are related to each other with respect to the winding directions of the windings (n ₇ ) (n ₈ ).

Next, the operation will be described. The voltage Vcc is a diode (D ₃ ).
When it is applied to the driving circuit (5) through the smoothing capacitor (C ₃ ), the voltage is about 100V to about 1V.
The pulsating current voltage V _B pulsates up to 40V. Assuming that the voltage V _B first causes the transistor (Q ₃ ) to conduct, a current begins to flow between its collector and emitter,
An induced voltage is generated in the positive feedback winding (n ₅ ) coupled to the collector winding (n ₁ ), and the induced voltage is generated via the primary winding (n ₆ ) of the second transformer (T ₂ ) into the transistor (n ₆ ). Q
₃ ) further induces an induced voltage in the base winding (n ₃ ).
This voltage causes the transistor (Q ₃ ) to perform positive feedback, and the conduction state is perfected with a sufficient base current. The current flowing through the resistance (R ₃ ) is applied to the second transformer (T
It increases linearly due to the primary inductance of ₂ ) and becomes saturated. This causes the current on the primary side of the second transformer (T ₂ ) to suddenly increase and the voltage drop across the resistor (R ₃ ) to increase, which causes the primary winding of the second transformer (T ₂ ) ( The voltage across n ₆ ) is reduced and the feedback voltage is reduced. Then, at the base of the transistor (Q ₃ ),
The voltage of the capacitor (C ₄ ) is applied with the polarity as shown, the transistor (Q ₃ ) is cut off, and the transistor (Q ₄ ) starts energization. Then, a feedback action occurs in the opposite direction to the previous one, turning off the transistor (Q ₃ ) and turning on the transistor (Q ₄ ). Second transformer (T ₂ )
The reverse primary current is reversed, and the transistor (Q ₄ ) is turned on in the same manner as when the transistor (Q ₃ ) is turned on. In this way, self-sustained pulsation continues. Two collector windings (n ₁ ) (n ₂ ) of the primary transformer (T ₁ ).
Are secondary windings (n ₇ ) (n ₈ ) (n ₉ ), respectively.
Since it is electromagnetically coupled to (n ₁₀ ), the transistor (Q
₃ ) An output is obtained according to ON / OFF of (Q ₄ ), and when the transistor (Q ₃ ) is ON, the signals a, b and c ′,
When an ON signal is obtained at d ′ and an OFF signal is obtained at signals a ′, b ′ and c, d, while the transistor (Q ₄ ) is ON,
The signals a, b and c ', d'are off signals a', b '.
An on-signal is obtained at c and d. These signal waveforms are shown in FIG.

Next, the operation of the first heating port (3 ₁ ) will be described. First, when the second transistor (Q ₂ ) is turned on, a current I _L1 flows through the induction heating coil (L), the resonance capacitor (C ₂ ) and the second transistor (Q ₂ ). When the second transistor (Q ₂ ) is turned off and the first transistor (Q ₁ ) is turned on, a circulating current in the same direction passes through the induction heating coil (L), the resonance capacitor (C ₂ ) and the diode (D ₁ ). Flowing. When this circulating current becomes zero, the current flowing through the series resonance circuit (4) is inverted and the first transistor (Q ₁ ), the resonance capacitor (C ₂ ) and the induction heating coil
Current flows through (L). Then, the second transistor (Q ₂ ) is turned on again and the first transistor (Q ₁ ) is turned off, but the diode (D ₂ ), the resonance capacitor (C ₂ ) and the induction heating coil (L) are turned on for a while. Therefore, circulating current flows. In this way, the SEPP inverter continues to oscillate and its frequency is set to about 20 KHz.

The driving of the first heating port (3 ₁ ) and the second heating port (3 ₂ ) is performed in a state where the phases are inverted by 180 °. That is, when the second transistor (Q ₂ ) of the first heating port (3 ₁ ) is in the on state, the second transistor (Q ₂ ) of the second heating port (3 ₂ ) is
_{2 '} ) is in the off state, and vice versa. This is achieved by adjusting the winding direction of the windings (n ₇ ) (n ₈ ) (n ₉ ) (n ₁₀ ). As a result, the current flowing out from the filter capacitor (C ₁ ) is the first heating port (3 ₁ )
And second heating port second transistor of _{(3 2) (Q 2)}
(Q _{2 '} ) flow alternately to the two second transistors (Q
₂ ) (Q _{2 '} ) do not flow simultaneously. FIG. 3A shows a conventional example in which the operation cycles of the first and second heating ports (3 ₁ ) (3 ₂ ) are the same, and FIG. 3B shows the load currents I _L1 and I _L2 in the embodiment of the present invention. And the outflow current I _CF of the capacitor (C ₁ ) are shown. In the figure (a), since the second transistors (Q ₂ ) and (Q _{2 ′} ) are turned on at the same time, the current I _CF flowing through the second transistor has a large value due to the superposition of two ports. ), The second transistor (Q ₂ ) (Q
_{2 '} ) are alternately turned on, the current _ICF is a current for only one port, and its peak current value is small. In this way, the outflow current of the filter capacitor (C ₁ ) is leveled. In the embodiment, the case of the two-neck cooker has been described. Therefore, the phase shift is 180 °, but if this is a three-neck cooker, the shift of the operation cycle of each heating port may be 120 °. .

As described above, the multi-port induction heating cooker of the present invention is SE
When driving multiple heating ports composed of PP inverters with the same power supply, the operation timing is made different for each heating port, so the outflow current of the filter capacitors composing the power supply circuit is leveled. You can
It is possible to use a capacitor with a small allowable ripple current.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram of a drive signal of the same example, FIG. 3A is a current waveform diagram of a conventional example, and FIG. 3B is a current waveform diagram of the embodiment of the present invention. . (3 ₁ ) ... first heating port, (3 ₂ ) ... second heating port, (5) ...
Drive circuit.

Claims (1)

[Claims] 1. An AC power supply, a rectifying circuit for rectifying the AC power supply, a power supply circuit including a choke coil and a filter capacitor, a pair of series-connected switching elements, an induction heating coil and a resonance connected in parallel to one of the switching elements. In a multi-port induction heating cooker having a SEPP inverter including a series resonance circuit made of a capacitor, the plurality of SEPP inverters being connected to the common power supply circuit, a drive circuit for driving the plurality of SEPP inverters. The drive circuit has an asynchronous function that makes the operation timings of a plurality of switching element pairs forming the plurality of SEPP inverters different for each SEPP inverter, and when the plurality of inverters are simultaneously operated, the ripple current flowing from the filter capacitor is reduced. Multiple mouths characterized by leveling Electrically heated cooker.