JPS5914993B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter 5 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 10, 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. Due to the characteristics of semiconductor controlled switching elements (thyristors), conventional inverter devices could only be operated up to an operating frequency of approximately 3KH2 or 15. For this reason, it has been difficult to operate the induction heating device at high frequencies. A time-sharing inverter device was developed as a means to solve this problem, but
This device has the disadvantage of requiring a very large number of control switching elements. SUMMARY OF THE INVENTION An object of the present invention is to provide an inverter device that can eliminate the above-mentioned drawbacks, operate a load at a high frequency, and simplify the device.

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, where 1 is a forward conversion device, and between the positive and negative outputs of this forward conversion device 1, first and second electrolytic capacitors 2a and 2b connected in series are connected in parallel. be done. At the midpoint 3 of these capacitors 302a and 2b, a first
The anode side of the thyristor 4 is connected, and the cathode side of the first thyristor 4 is connected to one electrode of the third electrolytic capacitor 6 via the commutation reactor 5. The other electrode of this third electrolytic capacitor 6 is a second electrolytic capacitor 35
It is connected to the negative side of the resistor 2b. 7 is the third electrolytic capacitor 6
The anode side of this diode 1 is connected to the common connection point 8 of the commutation reactor 5 and the third electrolytic capacitor 6, and the cathode side is connected to the positive side of the first electrolytic capacitor 2a. .

9 is a bridge circuit consisting of four second to fifth thyristors 9a to 9d; the positive side of this bridge circuit 9 is connected to the common connection point 8 via an inductance 10, and the negative side is connected to the second thyristor 9;
Connected to the negative side of electrolytic capacitor 2b.

11 is a load such as an induction heating device, and this load 11 is a second load,
It is connected between the midpoint of the fourth thyristors 9a and 9c and the midpoint of the third and fifth thyristors 9b and 9d.

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

Assume that the first and second electrolytic capacitors 2a and 2b are each charged to E volts as shown in the illustrated polarity. Here, when the first thyristor 4 is fired by a firing signal from a firing circuit (not shown), the charge in the second electrolytic capacitor 2b is discharged as shown by the arrow 12 in the diagram, and the third electrolytic capacitor 6 is commutated. Due to the action of the reactor 5, it is charged to 2E volts as shown in the polarity shown. (Period of mode 1 in FIG. 2) A detector (not shown) detects that the third electrolytic capacitor 6 has reached 2E volts, and ignites the second and fifth thyristors 9a and 9d of the bridge circuit 9, The charge of the third electrolytic capacitor 6 is supplied to the load 11. This charge causes load 1
1, a voltage e1 and a current 1 shown in mode 2 in FIG. 2 are generated. On the other hand, the electric charge is discharged through the second thyristor 9a1 load 11 and the fifth thyristor 9d, and charges the third electrolytic capacitor 6 with a polarity opposite to that shown in the figure. The charging voltage at this time becomes (E-ΔE) volts due to circuit loss and the like. After the third electrolytic capacitor 6 is charged to the opposite polarity as described above,
The first thyristor 4 is fired. Then, due to the action of the reactor 6, the third electrolytic capacitor 6 is higher by (E-ΔE) volts than in mode 1, so there is a possibility that the charging voltage will become 2E volts or more. However, when the voltage of the third electrolytic capacitor 6 becomes 2E or more, a discharge current (I in FIG. 2) is supplied to the first electrolytic capacitor 2a via the diode 7. Therefore, the third electrolytic capacitor 6 is always
It is held by the E bolt. This process is mode 3 shown in FIG. Note that during this mode 3 period, the load 11 is vibrating due to the above-mentioned supplied charge. At the end of this mode 3, a zero cross of the cage pressure or current of the load 11 (not shown) is detected and the third and fourth thyristors 9b and 9c of the bridge circuit 9 are activated.
ignite. (Mode 4 in FIG. 2), by this ignition, the charge in the third electrolytic capacitor 6 is supplied to the load 11 and returned to the capacitor 6 again. The third electrolytic capacitor 6 is charged to (E-△E) volts with the polarity opposite to that shown in the figure in the same manner as described above. Thereafter, the first thyristor 4 is ignited in the same manner as in mode 2 in FIG. In other words, the voltage is always maintained at 2E volts. 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 if an element capable of operating at a low frequency is used, the load can be operated at a frequency of approximately 10 KHz. Can operate at high frequencies. Further, according to the present invention, since the number of elements is extremely small, malfunctions are less likely to occur, and the reliability of the circuit can be improved and the circuit can be simplified.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the embodiment of FIG. 1... Forward conversion device, 2a, 2b, 6...
・First to third electrolytic capacitors, 4... First thyristor, 5... Commutation reactor, 7...
・Diode, 9...Bridge circuit, 11...
····load.

Claims (1)

[Claims] 1 A first series circuit of first and second capacitors connected in series between the positive and negative outputs of a forward converter, and a diode whose cathode side is connected to one end of this first series circuit, and an anode side of this diode. a second series circuit connected to the other end of the first series circuit via a third capacitor; and a first control switching element and a reactor connected between the midpoints of the first and second series circuits. and a bridge circuit consisting of second to fifth control switching elements connected in parallel to the third capacitor and controlled to supply the energy of the third capacitor to the load. , after firing the first control switching element to supply charge to the third capacitor, firing the second and fifth control switching elements to supply the charge of the third capacitor to the load; 3 capacitor is charged to the opposite polarity, then the first control switching element is ignited to reverse the charging polarity of the third capacitor, and after the charging is completed, the third capacitor is charged.
and firing the fourth control switching element to supply the charge of the third capacitor to the load, charging the third capacitor again to the opposite polarity, and then firing the first control switching element to reverse the charging polarity. An inverter device characterized by being configured to perform charging.