JPS5854749B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter device that enables high frequency operation.

In recent years, induction heating devices using inverter devices have come to be used for industrial heating.

This induction heating device is often used to heat a relatively surface layer of a member to be heated.

It is known that in order to heat the surface layer of the member to be heated, if the operating frequency of the inverter device is set to a high frequency, it becomes possible to heat only the surface layer of the member.

In conventional inverter devices, the turn-off time of the semiconductor-controlled switching elements (thyristors) used is 20 μS.
Due to its characteristics, it was only possible to operate up to an operating frequency of about 3 KHz.

For this reason, it has been difficult to operate the induction heating device at a higher frequency (3 KHz or higher).

As a means to solve this problem, a time-minute type inverter device has been developed, but this device has the drawback of requiring an extremely large number of control switching elements.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inverter device that eliminates the above-mentioned drawbacks, allows a load to operate at high frequency, and reduces the number of control switching elements.

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

FIG. 1 is a circuit diagram of an embodiment of the present invention, in which 1 is a forward converter, and between the positive and negative outputs of this forward converter 1 are first and second
A series circuit 2 of electrolytic capacitors 2a and 2b is connected in parallel.

3a, 3b and 4a, 4b are the first, second, third, and fourth risks connected in series as shown in the polarity;
The series circuit 3 of the first and second thyristors 3a and 3b is connected in parallel to the series circuit 2 in a direction opposite to the output of the forward converter 1.

Also, a series circuit 4 of the third and fourth thyristors 4a and 4b
are connected in parallel to the series circuit 2 in a forward direction with respect to the output of the forward converter 1.

Reference numeral 5 denotes a commutating capacitor, and this capacitor 5 is connected between the midpoints 6°1 of the series circuits 3 and 4.

8 is a reactor, 9 is a load, the reactor 8 and the load 8 are connected in series, and the middle point 10 of the series circuit 2 is connected to the middle point 10 of the series circuit 3.
and the midpoint 6 of

Next, the operation of the above embodiment will be described with reference to FIG.

Initially, the commutating capacitor 5 has the polarity shown in FIG.
Assume that the battery is charged to 2E volts as shown in mode 1 in FIG.

Further, the first and second electrolytic capacitors 2a and 2b are each charged with voltage divided to E volts by the output of the forward converter 1, as shown in the polarity shown in FIG.

Here, when the third thyristor 4a is fired by a firing signal from a firing circuit (not shown), the load 9 has the first polarity as shown in the diagram.
Voltage E volts of electrolytic capacitor 2a and commutating capacitor 5
Since a voltage of 2E volts is applied, the voltage across the load 9 becomes 3E volts as shown in mode 1 of FIG.

At the same time, a discharge current flows through the load 9 as indicated by an arrow 11, and the voltage e and current i shown in mode 1 of FIG. 2 flow through the load 9.
occurs.

In other words, electric power is generated in the load 9.

When the discharge current flows as indicated by the arrow 11 in the figure, a voltage of a curve Lv shown in mode 1 in FIG. 2 is generated in the accelerator 8.

A detector (not shown) detects the point in time when this generated voltage reaches 2E volts, and the second thyristor 3b is ignited (time point 11 in mode 1 in FIG. 2).

On the other hand, since the voltage of the reactor 8 is consumed via the second thyristor 3b and the load 9, the voltage of the commutating capacitor 5 does not exceed -2E volts, which is the reverse polarity shown.

That is, capacitor 5 holds -2E volts.

When the voltage of the reactor 8 is consumed, the second thyristor 3b is turned off, but the load 9 is vibrated by the supplied power as described above and maintains its operating state.

A detector (not shown) installed in the load 9 detects that this vibration has reached the end of one and a half cycles, and the fourth
The thyristor 4b is fired.

Then, the electric charge in the commutating capacitor 5 is discharged through the load 9 as shown by the arrow 12 (Mode 2 in Fig. 2).
As shown in mode 2, power is generated in the load 9 by voltage e1 and current i.

On the other hand, along with the discharge, a voltage is generated in the reactor 8 in the same way as described above, but when this voltage reaches 2E volts, the first thyristor 3a is ignited (at time t2 in mode 2 in FIG. ) and consume this.

Therefore, the voltage of the commutating capacitor 5 is always maintained at 2E volts.

Thereafter, as described above, only the load 9 is in the operating state, and the mode 1 operation is started after a predetermined cycle.

In this operating state, sufficient power can be supplied to the load even if the operating frequency of Cyrisk is low.

As described above, according to the present invention, the operating frequency of the load is approximately three times the operating frequency of the control switching element, so for example, if the operating frequency of the element is 3 KHz, the load is approximately 10 KHz. It is possible to operate at high frequency and supply high frequency to the load.

Further, according to the present invention, the number of elements can be greatly reduced, which has the advantage of reducing the occurrence of circuit failures and improving the reliability of the device.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram illustrating an embodiment of the present invention, and FIG. 2 is a waveform diagram illustrating the operation of the embodiment of FIG. 1... Forward conversion device, 2, 3.4... Series circuit, 2a, 2b... 1st. Second electrolytic capacitor, 3a. 3b, 4a, 4b...first to fourth thyristors,
5... Commutation capacitor, 8... Reactor, 9... Load.

Claims (1)

[Claims] 1 A first series circuit consisting of first and second electrolytic capacitors connected in parallel between the positive and negative outputs of the forward conversion device and charged by the device; a second control switching element comprising first and second control switching elements connected in series in opposite directions to the output;
a third series circuit comprising a series circuit, third and fourth control switching elements connected in series in the forward direction with respect to the output of the forward converter, and a connection between the rain points of the first and second series circuits; a fourth series circuit consisting of an accelerator and a load, and a commutating capacitor connected between the rain points of the second and third series circuits; A charging voltage of the first electrolytic capacitor and a charging voltage of the commutating capacitor are applied, and when the reactor reaches a predetermined voltage, the second control switching element is ignited, and the current flowing through the load reaches a predetermined vibration point. , the fourth control switching element is ignited to apply the charging voltage of the second electrolytic capacitor and the charging voltage of the commutating capacitor to the load in the opposite direction to the above case, so that the reactor reaches a predetermined voltage. An inverter device characterized in that the first control switching element is turned on when the inverter is turned on.