JPS589551B2 - Yuudou Kanetsu Sochi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to induction heating devices, particularly static power converters that directly convert low frequency alternating current to high frequency power. After conversion, it is common to convert it into high frequency power using a high frequency inverter, but there are very few examples of static power converters that directly convert low dark wave AC into high frequency AC, and the control circuit is complicated. However, there were drawbacks such as oscillation becoming unstable.

Therefore, the present invention directly converts low-frequency alternating current into high-frequency power using a simple control circuit, and is stable against load fluctuations and capable of large power conversion. This product provides a power converter that is ideal for use as a high-frequency power source for heating cookers and other devices.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, an AC voltage is applied to a static power conversion circuit 2 from an AC input power source 1.

The static power converter circuit 2 has a half-bridge inverter block 2A and an inverter block 2B connected in reverse series, and automatically and alternately stops oscillation depending on the polarity of the AC input voltage 1.

The inverter seven-piece 2A is a basic form of a series inverter, and is connected to the AC power supply 1 via the power switch 21, and connects the connection point A and series connection of the resonance capacitors 23a and 23a' connected in series with the input capacitor 22a as the power source. between the connection point A' of the thyristors 24a and 24a', which are power switching semiconductors, that is, A-''
An induction heating coil 26a is connected between A'.

Diodes 25a and 25a' are connected in antiparallel to the thyristors 24a and 24a', respectively, and the thyristors 24a and 24a' are connected in antiparallel.
The anode of a and the resonance capacitor 23a are connected to the U terminal of the input capacitor 22a.

Similarly, the cathode side of thyristor 24a' is connected to the E terminal of input capacitor 22a.

Next, inverter block 2B
Same connection as A, serially connected Cyrisk 24b
, 24b' are connected in the opposite direction to the inverter 7A.

Further, the control circuit 3 controls the conduction of the thyristors 24a, 24a' and the thyristors 24b, 24b'. 24b and thyristor 24a'
, 24b' are made conductive alternately.

When the polarity of the AC input power supply 1 is positive, the input capacitor 22a
The U terminal of the inverter block 2B becomes positive and the E terminal becomes negative, and a positive half-wave voltage is applied to the inverter block 2A due to the rectifying action of the regeneration diodes 25b and 25b' of the inverter block 2B, which alternately turns on the thyristors 24a and 24a'. If you let
A sinusoidal current flows through the induction heating coil 26a.

Furthermore, when the AC input power supply 1 has negative polarity, the regeneration diodes 25a and 25a' of the two inverter blocks act as rectifiers, voltage is applied to the inverter block 2B, and the control circuit 3 activates the thyristors 24b and 24b'. When the coils are made conductive alternately, a sinusoidal current flows through the induction heating coil 26b.

The control circuit 3 must trigger the Cyrisk at a frequency lower than the series resonance frequency of the resonance capacitors 23a, 23a' or the resonance capacitors 23b, 23b' and the induction heating coils 26a, 26, otherwise the Cyrisk turn-off time will be It becomes impossible to secure

It is also possible to simultaneously apply a trigger pulse to one thyristor of the inverter block 2A and one thyristor of the inverter block 2B, and the pulse transformers 31a, 3
One of the output windings of the pulse transformer 31a is wound between the gate and cathode of the two thyristors 24a of the inverter block, and the other output winding is wound between the gate and cathode of the thyristor 24b of the inverter block 2B. Connected between gate and cathode.

Similarly, the output winding of the pulse transformer 3lb is connected between the gates and cathodes of the thyristors 24a' and 24b'.

When the induction heating coils 26a and 26b shown in Fig. 1 are applied to a household induction heating adjuster, they have two heating parts (two burners), but they have one heating part (one burner). In this case, the two wires are wound in parallel as shown in FIG. 2, and the output is shared between the inverter blocks 2A and 2B.

FIG. 3 shows another embodiment of the present invention, which is applied to an induction heating cooker having one heating section, in which an inverter block 2A. 2B is generally called a T-bridge.

The induction heating coil 26 has the same configuration as shown in FIG. 2, and one end of the parallel-connected spiral plate-shaped induction heating coils 26 is commonly connected to the ground line E.

That is, FIG. 3 shows an example of a configuration in which the current of the induction heating coil 26 is fed back. A current transformer 32 is connected to the common lead wire E' of the induction heating coil 26, and a signal proportional to the induction heating coil current is generated from the rectifier circuit 33. An example of a configuration is shown in which the gate trigger period is changed so that the set value is obtained.

Although a half-bridge and a T-bridge are shown as examples of the present invention, a full bridge is also possible, and application is possible by connecting in series an inverter tank having a regenerative diode connected anti-parallel to the silice. .

In addition, it is possible to use not only Cyrisk but also transistors.

As described above, according to the present invention, instead of using a conventional high-frequency power source using a rectifier circuit and an inverter, an inverter block is connected in inverse series to directly convert low-frequency AC to high-frequency AC. AC-HFAC conversion is easily possible without the need for a rectifier circuit.

In addition, since the inverter blocks connected in anti-series operate alternately depending on the polarity of the AC input voltage, the capacitance of power switching semiconductors such as Cyrisk can be small.
There is no problem of current sharing due to parallel connection of semiconductors, and a large-capacity conversion device can be realized.

As described above, according to the present invention, a large-capacity frequency conversion device can be obtained using an inexpensive and small-capacity power switching semiconductor in an induction heating device.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a two-burner induction heating device showing one embodiment of the present invention, Fig. 2 is a circuit diagram of the main part of an embodiment in which a similar induction heating coil is applied to one burner, and Fig. 3 Figure 4 is a circuit diagram showing an example of a single burner in which T-bridge inverter blocks are connected in reverse series, and Figure 4 is a circuit diagram of the part that detects the induction heating coil current. 1... AC input power supply, 2... Static power conversion circuit, 3... Control circuit, 2A, 2B...
...Inverter block.

Claims (1)

[Scope of Claims] 1. A series circuit of power switching semiconductors in which diodes are connected in antiparallel, an input capacitor connected in parallel to this series circuit, and an inductor connected to an interconnection point of the series circuit of power switching semiconductors. An induction heating device comprising an inverter block consisting of a series circuit of a heating coil and a resonant capacitor, two sets of the inverter blocks are provided and connected in anti-series between commercial power supply terminals. 2. The induction heating device according to claim 1, wherein the front induction heating coil is coaxially wound in parallel to form a single induction heating coil.