JPS62166785A - Inverter protection system - Google Patents

Abstract

PURPOSE:To detect excess kick current at the time of inductance load and excess discharge current at the time of capacitor load correctly by connecting a current detection resistance in series to a switching element placed in the unopposed position in a bridge connection. CONSTITUTION:Current detection resistances 5-1, 5-4 for detection of excess current are respectively provided in series to transistors 1-2 and 1-4 and current detection resistances 5-2, 5-3 in series to freewheeling diodes 2-2 and 2-4. The sum of respective absolute values of the detection voltage appearing on the resistance 5-1 and that appearing on the resistance 5-4 is abstrated while the sum of respective absolute values of the detection voltage appearing on the resistance 5-2 and that appearing on the resistance 5-3 is found so that various excess current states produced in the inverter circuit will be detected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an inverter protection system, in particular, an inverter protection system, which is provided with a switching element having an externally attached or built-in freewheeling diode, and in which the switching element is connected in a bridge. The present invention relates to an inverter protection method in which current detection resistors are connected in series to the switching elements located at non-opposed positions, and overcurrent in the inverter circuit is detected using the respective detection voltages.

[Conventional technology]

Conventionally, inverter circuits having a configuration as shown in FIG. 4 or FIG. 5 have been known. In addition, it may be considered that a normal low power factor load is connected instead of the inductance load shown in FIG. 4 or the capacitor load shown in FIG. 5.

In FIG. 4 and FIG. 5, reference numerals 1-1 to 1-4
are transistors, 2-1 to 2-4 are freewheeling diodes, 3 is a load, 3-L is an inductance load, 3-C is a capacitor load, 4 is a DC power supply, and 5 is a conventional current detection represents resistance.

Conventionally, an inverter circuit having the above-mentioned configuration is known, but when an inductance load 3-L or a capacitor load 3-C is connected as a load.

The following problems are inherent.

[Problem that the invention seeks to solve]

In the case where the inductance load 3-L is connected as shown in FIG. 4, now the transistors 1-1 and 1-4
is turned off from the on state, and transistors 1-2 and 1-3 are accordingly turned on,
A kick current such as iK shown in FIG. 4 may occur. That is, when transistors 1-1 and 1-4 are turned off, current tends to continue flowing through inductance load 3-L, resulting in the large kick current! , may occur.

For this purpose, on the current detection resistor 5, which is originally provided to detect the magnitude of the operating current I shown in FIG.
Large conducting voltages appear in an undesirable manner. For this reason, there is a risk that transistors and the like in the overcurrent detection circuit located in the subsequent stage may be destroyed.

In addition, when the capacitor load 3-C is connected as shown in FIG. 5, now the transistors 1-2 and 1-3
When the transistors 1-1 and 1-4 are turned off from the on state and accordingly the transistors 1-1 and 1-4 are turned on, a large discharge current as shown in FIG. 5 (i) may occur. In such a case, the current detection resistor 5, which was originally provided to detect overcurrent, will not be able to detect the overcurrent state due to the discharge current.

[Means for solving problems]

The present invention solves the above-mentioned problems, selects the position where the current detection resistor is disposed, allows correct detection of overcurrent in normal cases, and solves the problems in the above-mentioned cases.

FIG. 1 is a diagram illustrating the principle of the present invention and constitutes a first embodiment of the present invention. In the figure, 1-1 to 1-4 are transistors, 2=1 to 2-4 are freewheeling diodes, 3 is a load, 5-1 to 5-4 are current detection resistors, V+, V2, respectively. , V-+
, Va represents the detection voltage.

The circuit configuration shown in FIG. 1 is substantially the same as the conventional configuration, but the current detection resistors 5-1 and 5 for overcurrent detection are
-4 are connected in series with transistors 1-2 and 1-4, respectively, and current detection resistors 5-2 and 5-3 are connected in series with freewheeling diodes 2-2 and 2-4, respectively. It's profitable.

Therefore, the voltages generated across resistors 5-1 and 5-4 are (i) due to normal operating current.

(ii) Due to discharge current in case of capacitor load. Furthermore, the voltages generated across the resistors 5-2 and 5-3 are (1) due to kick current in the case of an inductance load, and (ii) due to discharge current in the case of a capacitor load.

[Effect]

In the case shown in Figure 1, the detection voltage appearing on the resistor 5-1 is
, and the detection voltage 2 appearing on the resistor 5-4. The sum of the respective absolute values of IVz l”
lV41 is extracted and various overcurrent conditions occurring in the inverter circuit are detected.

Although not shown, it goes without saying that such a detection circuit exists.

〔Example〕

FIG. 2 shows the configuration of another embodiment of the present invention. The symbols in the figure correspond to those in FIG.

As can be seen from the explanation given in relation to FIGS. 4 and 5 above, in the case where an excessive current flows through the resistors 5-2 and 5-3 shown in FIG. 1, (i) the inductance shown in FIG. (ii) the kick current iK in the case of a load; and (ii) the discharge current tc in the case of the capacitor load shown in FIG. Also, in the case where excessive current flows through resistors 5-1 and 5-4, (
i) Excessive operating current ■ in the case of the inductance load shown in FIG. 4, and (ii) Discharge current tc and excessive operating current IL in the case of the capacitor load shown in FIG.

From this, when the load 3 is operated in a state where the inductance component is relatively small.

By omitting the resistors 5-2 and 5-3 shown in FIG.
In other words, a simplified version can be provided. The configuration shown in FIG. 2 corresponds to the simplified type.

FIG. 3 shows a configuration of still another embodiment of the present invention. Reference numerals 3.5-1.5-4 in the figure correspond to those in FIG. 1, 6 is a detection circuit, and swi to SW4 are switching elements, each of which is a transistor with a built-in freewheeling diode. For example, it represents an FET.

In the case of an FET, it equivalently has a built-in freewheeling diode as shown in FIG.

For this purpose, the current flowing through the two transistors 1-2 and 1-4 and the current flowing through the freewheeling diodes 2-2 and 2-4 are separated as shown in FIG. cannot be detected. For this reason, in the case shown in FIG. 3, a resistor 5-1 is inserted in series with the switching element SW2, and a resistor 5-4 is inserted in series with the switching element SW4.

As can be seen from the explanation given in connection with FIGS. 4 and 5 above, (i) When the operating current IL becomes excessive,
(ii) When the kick current iK becomes excessive and (
iii) When the discharge current tc becomes excessive,
The following pattern detection mode appears. That is.

(A) When the operating current IL is excessive.

[Case 1]: Voltage ■, is ■, voltage ■2 is zero [Case 2]: Voltage ■1 is zero, voltage ■2 is θ(B) When kick current iK is excessive.

[Case 3]: Voltage V, is e, voltage ■2 is zero [Case 4]: Voltage V, is zero, voltage ■2 is e (C), discharge current 1
When c is excessive.

[Case 5]: Voltage ■1 is e, voltage ■2 is e(/y-
45); A pattern of detection appears in which the voltage v+ is e and the voltage vz is e. The detection circuit 6 shown in FIG.
Although the circuit is configured to discriminate the following cases, the detailed circuit is omitted because it can be constructed relatively easily.

In the case of the embodiment shown in FIG. 3, FETs are used as the switching elements SWI to SW4, but the switching elements shown in FIG. You may also use a paired circuit with.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to correctly detect an excessive kick current when an inductance load is applied or an excessive discharge current when a capacitor load is applied.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle configuration of the present invention and constitutes the first embodiment of the present invention, Fig. 2 shows the structure of the second embodiment of the invention, and Fig. 3 shows the structure of the third embodiment. . FIGS. 4 and 5 show conventional configuration diagrams. In the figure, 1 is a transistor, 2 is a freewheeling diode, 3 is a load, 4 is a DC power supply, 5 is a current detection resistor,
6 represents a detection circuit, and SW represents a switching element. Patent applicant: Sawafuji Electric Co., Ltd. Representative Patent Attorney Mori 1) Hiroshi (2 others)'? J1
Flash ￥52121

Claims (1)

[Claims] In an inverter circuit comprising a switching element with an externally attached or built-in freewheeling diode, the switching element is connected in a bridge, and a load is connected between the neutral points of the bridge connection, the non-opposing position in the bridge connection is Connecting current detection resistors in series with at least the switching elements present in the respective current detection resistors, extracting the detection voltage generated on each of the current detection resistors,
An inverter protection system comprising an overcurrent detection circuit for detecting an overcurrent state in the inverter circuit.