JPH11122939A - Inverter controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce inrush current to a load and enable stable operation with a small-capacity inverter by dividing an alternating-current output voltage of an inverter for converting direct currents into alternating currents, into a plurality of voltages through the units of cycle of output waveform, and turning them on/off. SOLUTION: A direct current DC-input goes into a switching section and is converted into an alternating-current there. Field effect transistors Q1-Q4 are divided through a fundamental wave control circuit 4 by the cycle of the waveform of the alternating-current output voltage of an inverter. At the same time as turning on/off which is repeated in the fundamental wave control circuit 4, the output current divided by the cycle of fundamental waveform, for example, 50 or 60 Hz is smoothed at a PWM control circuit 5. As a result, inrush current flowing to a load can be reduced, and stable operation can be performed, even through a small-capacity inverter without damages to circuit parts or actuation of a protective circuit. The number of divisions is increased with the increase in the load current of the inverter and is set only in the initial stage of energization if the filament is warm, similar to the case where the lamp is on and the next inrush current is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a commercially available general inverter and an inverter control device suitable for controlling a vehicle-mounted inverter.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a schematic configuration of a DC-AC inverter for converting a DC voltage (power) into an AC voltage (power). This inverter includes a switching unit 1 having a booster circuit configuration using a switching element and a DC-
And an inverter unit 2 for performing AC conversion.

FIG. 5 is a circuit diagram showing details of the inverter section 2. As shown in FIG. In the figure, Q1 to Q4 are N-type FETs.
Thus, the series circuit of the FETs Q1 and Q2 and the series circuit of the FETs Q3 and Q4 are connected in parallel. And these F
The ON (ON) and OFF (OFF) of the ETQ1 to Q4 are controlled by the control circuit 3, and rectangular wave power is supplied to the load from the connection point of each FET in the series circuit.

In the inverter configured as described above, for example, a DC voltage of 12 V DC input to the switching unit 1 is boosted to approximately 114 V here, and
Is input to And, 50 Hz by the inverter unit 2
Alternatively, it is converted into a 60 Hz AC 100 V AC and output. At that time, in the inverter section 2, the FETs Q1 and Q4 are simultaneously turned on and the FETs Q2 and Q3 are simultaneously turned off. Then, the FETs Q2 and Q3 are simultaneously turned on and the FETs Q1 and Q4 are simultaneously turned off.
The turning off is alternately repeated, and a pseudo sine wave AC voltage having a zero level as shown in FIG. 6 is output. FIG. 7 is a waveform diagram showing an output current flowing to the load.

[0005]

However, in the above-described conventional inverter, since the output AC voltage is a rectangular wave voltage, the power supply starts when a load such as a capacitor, a transformer, or a lamp is used. Sometimes a large inrush current flows, circuit components are damaged, protection circuits are activated,
There was a problem that normal operation could not be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an inverter control device capable of reducing an inrush current flowing to a load and capable of performing stable operation with an inverter having a small capacity. It is intended to be.

[0007]

An inverter control device according to the present invention is configured as follows.

(1) In an inverter control device for converting DC power to AC power, an AC output voltage of the inverter is divided into a plurality of units in a cycle unit of an output waveform, and is turned on.
A division control means for turning off is provided.

(2) In the device of (1), the division control means increases the division number as the load current of the inverter increases.

(3) In the device of (1) or (2), the division control means divides the load for a certain period only at the initial stage of energizing the load.

[0011]

FIG. 1 is a circuit diagram of an inverter control device according to the present invention, showing the internal structure of an inverter section 2 of the DC-AC inverter shown in FIG.

In FIG. 1, reference numeral 4 denotes each F having the same configuration as that of FIG.
This is a basic waveform control circuit for controlling ON and OFF of the ETQ1 to Q4, and corresponds to the control circuit 3 in FIG. Reference numeral 5 denotes a P for turning on and off the AC output voltage of the inverter by dividing the AC output voltage of the inverter into a plurality in units of cycles of the output waveform as shown in FIG.
It is a WM control circuit (division control means).

In this embodiment, as in the prior art, the input direct current is first boosted by the switching unit 1, enters the inverter unit 2 having the configuration shown in FIG. 1, is converted into alternating current, and is output. At this time, the FETs Q1 to Q4 are periodically turned on and off by the basic waveform control circuit 4 as described above.
The output current is leveled as shown in FIG. 3 by dividing into a plurality of units of the cycle of the basic waveform of z or 60 Hz.

As a result, the inrush current flowing to the load is reduced, and stable operation can be achieved even with an inverter having a small capacity without damaging circuit components or activating the protection circuit. For example, a load in which a rush current of 15 to 20 times the steady state has flowed decreases the current to about 1.5 to 2.0 times, and normal operation is always possible.

Here, the load condition, for example, if the capacitor is initially empty, the charge is initially empty but remains charged once energized, or if the lamp is turned on once, the filament becomes warm and the next In consideration of the situation that the inrush current is small at the time of energization, the division control may be set for a certain period only in the initial stage of energization to the load, for example, about the first five cycles.

The number of divisions may be increased as the load current of the inverter increases, and a more leveled output current can be obtained. In the example shown in FIG.
The output of a half cycle of 10 msec at a peak value V0 of V is divided into 10 to 20 equally, and the interval is set to 0.5 msec.
The case where it is set to c is shown.

In the above embodiment, the FETs Q1 and Q4
And the FETs Q2 and Q3 are controlled to be on and off respectively. However, the division control by the PWM control circuit 5 may be performed only for the FETs Q1 and Q3 or only for the FETs Q2 and Q4.

Although the case where the output waveform of the inverter is a rectangular wave has been described, the present invention can be applied to the case where the output waveform is a sine wave, and the same operation and effect can be obtained.

[0019]

As described above, according to the present invention, the inrush current flowing to the load can be reduced, and the stable operation can be performed by the inverter having a small capacity.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform chart showing an output voltage of the inverter according to the embodiment.

FIG. 3 is a waveform chart showing an output current of the inverter according to the embodiment.

FIG. 4 is a block diagram schematically showing a DC-AC inverter.

FIG. 5 is a diagram showing a circuit configuration of a conventional example.

FIG. 6 is a waveform diagram showing an output voltage of a conventional inverter.

FIG. 7 is a waveform diagram showing an output current of a conventional inverter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switching part 2 Inverter part 4 Basic waveform control circuit 5 PWM control circuit (division control means) Q1 FET Q2 FET Q3 FET Q4 FET

Claims (3)

[Claims] 1. An inverter control device for converting DC power into AC power, wherein division control means is provided for turning on and off the AC output voltage of the inverter by dividing the AC output voltage into a plurality of units of a cycle of the output waveform. Inverter control device. 2. The division control means increases the number of divisions as the load current of the inverter increases.
Inverter control device as described. 3. The inverter control device according to claim 1, wherein the division control means divides the load for a certain period only at the initial stage of energizing the load.