JPS62221877A - Inverter protection system - Google Patents

Abstract

PURPOSE:To simplify the organization of a circuit and prevent over current from flowing, by checking the detected polarities of load voltage and oscillating circuit section output, and by controlling a rest period. CONSTITUTION:An inverter circuit is composed of transistors 1-1-1-4 and free wheeling diodes 2-1-2-4, and current is fed to a load 3. In parallel with the transistors 1-2, 1-4, voltage detecting resistor 5-1-5-4 are respectively arranged, and a polarity detecting section 6 for detecting the polarity of load voltage, a rectangular wave oscillating circuit section 7, and a polarity comparing circuit section 8 are set. Then, the polarity of voltage generated on the load 3 is detected and is compared with the output polarity of the oscillating circuit section 7, and just during a period when both the polarities are different, a rest period when all switching elements are turned OFF. As a result, the discharge period of a condenser is separated from a period when the transistors are ON for charge, and over current can be prevented from flowing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter protection system, particularly an inverter circuit having bridge-connected switching elements.
The present invention relates to an inverter protection system that compares the polarity of the output of an oscillation circuit that controls the switching element with the polarity of the voltage generated in the load, and provides a rest period for the on/off converter of the switching element.

[Conventional technology]

Conventionally, an inverter circuit having a configuration as shown in FIG. 3 has been known.

In FIG. 3, numerals 1-1 to 1-4 are transistors, respectively, and 2-1 to 2-4 are free-boiling transistors, respectively.
Diode, 3 is the load, 3-R is the resistive load, 3-
C represents a capacitor load, and 4 represents a DC power supply.

Conventionally, inverter circuits having the above configuration are known, but when a capacitor load 3-c is connected as a load, a first-order problem is inherent.

[Problem that the invention seeks to solve]

In the case where the capacitor load 3-C is connected as shown in FIG. 4 is turned on, a large discharge current as shown in FIG. 3 occurs. This is because transistors 1-1 and 1-4 are turned on when the capacitor load 3-C is charged as shown in FIG. 3 (+) and (-), so the voltage is doubled. This is because the capacitor load 3-C tends to be charged in the opposite direction. Figure 4 shows the situation during this time in a time chart.

[Means for solving problems]

The present invention solves the above problems by arranging the voltage detection resistor and detecting the polarity of the voltage generated in the load.

FIG. 1 is a diagram illustrating the principle of the present invention and constitutes an embodiment of the present invention. Codes 1-1 to 1-4 in the diagram
are transistors, and 2-1 to 2-4 are freewheeling diodes.

3 represents a load, and 5-1 to 5-4 each represent a voltage detection resistor. Further, 6 represents a polarity detection section for detecting the polarity of the load voltage, 7 represents a rectangular wave oscillation circuit section, and 8 represents a polarity comparison circuit section.

The operation of the circuit shown in Figure 1, especially the transistor 1-
There is no substantial difference from the conventional configuration in that the first group of switching elements 1 and 1-4 and the second group of switching elements of transistors 1-2 and 1-3 are alternately turned on. just.

Resistors 5-1 to 5-4 are provided to detect the polarity of the voltage present on the load 3.

That is, the voltage (RV) on the right side in the figure and the voltage (LV) on the left side in the figure of the load 3 are extracted.

The period in which RV-LV≧10△■ is regarded as the first polarity, and the period in which LV-RV≧+
The period of Δ■ is regarded as the second polarity, and the polarity detection section 6 notifies the polarity comparison circuit section 8 of this fact.

The rectangular wave oscillation circuit section 7 emits a rectangular wave output.

The polarity comparison circuit section 8 compares the polarity of the output of the rectangular wave oscillation circuit section 7 and the polarity from the polarity detection section 6. A rest period in which the entire switching element is turned off is provided only during the period in which the polarities of the two are different.

[Effect]

The above operating situation is made clear by the time chart shown in FIG. In fig.

The period marked as "suspension" corresponds to the above-mentioned suspension period. The rest period corresponds to a period in which the voltage of the capacitor present in the load 3 is attenuated due to discharge, as shown by hatching in the figure.

For this purpose, after waiting for a period during which the capacitor present in the load 3 is discharged, for example, the set of transistors 1-2 and 1-3 is changed to the set of transistors 1-1 and 1-4. That is, the period in which the capacitor is discharged and the period in which the switching element is turned on and charged are separated, and excessive current is prevented from flowing.

〔Effect of the invention〕

As explained above, according to the present invention, the above-mentioned rest period can be caused by simply checking the polarity of the output of the oscillation circuit section and the polarity of the load when performing control to cause the above-mentioned rest period. can. For this purpose, for example, in providing the above-mentioned rest period, a predetermined zero voltage period is provided in the oscillation circuit output waveform itself.

The two-circuit configuration is extremely simple compared to conventionally known configurations. In other words, it is now possible to achieve the intended purpose even through digital processing.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle configuration of the present invention, which constitutes an embodiment of the present invention, Fig. 2 is a time chart explaining its operation, Fig. 3 is a conventional configuration, and Fig. 4 is its operation. A time chart for explanation is shown. In the figure, 1 is a switching element (transistor). 2 is a freewheeling diode, 3 is a load. 3-C is a capacitor load, 4 is a DC power supply, 5 is a voltage detection resistor, 6 is a polarity detection section, 7 is a rectangular wave oscillation circuit section, and 8 is a polarity comparison circuit section.

Claims (1)

[Claims] In an inverter circuit that includes a switching element with an external or built-in freewheeling diode, the switching element is connected in a bridge, and a load including a capacitor is connected between the neutral point of the bridge connection. Connecting voltage detection resistors in parallel to at least the switching elements located at non-opposing positions, extracting the detection voltages generated on the respective voltage detection resistors and detecting the polarity of the voltage occurring in the load; and is configured to compare the polarity with the polarity of the output of the oscillation circuit that controls the switching element, and based on the comparison result, the first
An inverter protection system characterized in that after the switching elements of the group are turned off, there is a rest period in which the switching elements of the second group are not turned on.