JPS6328278A - Inverter controlling circuit - Google Patents

Abstract

PURPOSE:To eliminate the flow of a large rush current to a rectifier circuit at the time of supplying a power voltage by charging a capacitor through a resistor until a predetermined voltage is obtained across the capacitor at the time of power source ON and then shortcircuiting the resistor. CONSTITUTION:When a power source voltage is supplied to an input terminal A, a smoothing condenser CD is charged through a rectifier circuit SR. A voltage is supplied from a DC/DC converter 4 to an inverter controlling circuit 2 during a period that a voltage across the condenser CD arrives at a normal value. A transistor 6 is turned OFF until the output voltage of an attenuator 7 arrives at a reference voltage V3, and a relay 5 is not energized. Accordingly, a charging current to the capacitor CD flows to a resistor RD. When the output voltage of the attenuator 7 exceeds a reference voltage V3, the transistor 6 is turned ON, and the relay 5 is energized. Thus, the resistor RD is shortcircuited by a contact (r).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an inverter control circuit used in an induction motor control system, and particularly relates to an inverter control circuit designed to reduce inrush current. .

[Conventional technology]

As conventional inverters, the circuits shown in Figures 3 (a) to (9) are known. In Figure 3 (a), symbol A is an AC power supply voltage input terminal, R relay coil, and SR is a full-wave rectifier. Circuit, contact point of relay R, RI) is resistance, CI) is smoothing capacitor, DC is separation voltage obtained on both sides of smoothing capacitor CD, It is a conversion circuit.

In the above configuration, when a mix voltage is input to input terminal A, at the instant of input, while relay R is turned on with a delay, the voltage rectified by rectifier circuit SR is first passed through resistor RD. When the relay contact r is turned on, the output voltage of the rectifier circuit SR is transferred to the DC/AC converter circuit IN via the relay contact.
It can be supplied to V. In this way, the inverter shown in Figure 3 (a) utilizes the operation delay time of relay R in order to reduce the rush current caused by capacitor CD when power supply voltage is supplied. In addition, in the same figure (b), in addition to the circuit configuration of the same figure 0), a timer T is provided, and this timer T further delays the time when the relay R is turned on. 1. In the same figure (c), the relay R is operated by the output voltage of the I)C/T)C converter CV for the control circuit power supply.

In this case, it is possible to roughly delay the turning on of relay R compared to the circuit shown in FIG. , W, the rectifier S from the rush current generated when supplying the original voltage.
If you keep R and use only relay R (Figure 3 (a)), when the power supply voltage is momentarily turned off, contact r will cause chattering and contact There were other problems such as deterioration and a relatively large contact current flowing when the power was turned on. Additionally, if a timer T is used to turn on the relay R (FIG. 3 (b)), there is a problem that the price will be high.

Further, when the relay R is driven by the DC/DC converter CV (@Figure 3 (c)), the following problem occurs.

In other words, since this DC/DC converter cv supplies the power supply voltage of the inverter control circuit, it is designed so that a constant output voltage can always be obtained even if the input voltage, the DC voltage vDc, fluctuates considerably. ing. Therefore, if the power supply voltage is turned off and the DC voltage vDc drops to the point where relay R is about to open, and then the power supply voltage is turned back on at that point, a large inrush current will flow into the rectifier circuit SR. .

This invention was made against this background, and its purpose is to provide an inexpensive inverter control circuit that prevents a large inrush current from flowing through the rectifier circuit SR when power supply voltage is supplied. It's about doing.

[Means for solving problems]

This invention rectifies AC voltage, supplies the rectified voltage to a capacitor via a parallel connection circuit of a resistor and switching means, smoothes it with this capacitor, and converts this fig voltage into DC/AC f! In the inverter, which converts the IH current voltage into an AC voltage again by a conversion circuit, voltage conversion means converts the IH current voltage into a low-voltage DC voltage, and the IA DC voltage obtained across the capacitor is a predetermined voltage. The present invention is provided with a detecting means for detecting whether the opening/closing means is large or not, and a control means for controlling the opening/closing means on/off in accordance with the output of the detecting means.

[Effect]

According to the above configuration, when the power is turned off, until the DC voltage obtained across the capacitor becomes larger than the constant voltage,
When the switching means is off, the rectified voltage charges the capacitor via the resistor. Then, when the DC voltage becomes higher than a certain voltage, the switching means is turned on, and a regulating voltage is applied to the capacitor via the switching means. Further, when the power is turned off instantaneously, the switching means is turned off at the point in time when the DC voltage becomes smaller than the constant voltage. After this, when the power is turned on again, the switching means remains off until the DC voltage exceeds a certain voltage, so the rectified voltage charges the capacitor via the resistor.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.
FIG. m1 is a circuit diagram showing the configuration of an embodiment of the present invention. In FIG. 2 is an inverter control circuit. In this inverter control circuit 2, 4 is a T')C/nc converter that generates a DC voltage for operating the inverter control circuit 2, and converts the ambiguous voltage vDo of the capacitor CD into a voltage v1 (
For example, the voltage is converted to 24 (V)) and output. 5 is a relay, which is driven by the above voltage V. 6 is a switching transistor, 7 is an attenuator, and VDC (approximately 3 no.
rV)) to voltage V2 (approximately 20 (V)). 8 is a comparator, 9 is a variable resistor, and the reference voltage V3 (
210 which generates about 19 (V)) is a knot gate, 11
This is an inverter protection circuit that stops the operation of the free current/AC conversion circuit 11NV when the power supply voltage drops.

Next, the operation of the above-mentioned circuit will be explained with reference to the waveform factors shown in FIG. ! ! First, at time to l', when the power supply voltage (@Figure 2 (a)) is supplied to the input terminal A, the smoothing capacitor CD is charged and a DC voltage vDc occurs (Figure 2 ←)). do. Here, until the voltage vDc across the capacitor CD reaches a steady value (for example, 3 (10 (V)), the DC/nCr converter 4 operates at time t1, and the voltage V, (24 (V)) is output (FIG. 2 (c)), thereby supplying voltage to each circuit part of the inverter control circuit 2.

Next, as vDC rises, the output voltage v2 of the attenuator 7 rises until the time t2 when it reaches the 1M quasi-voltage vo.
(V3, so the output of comparator 8 is 101 (G=) in Figure 2). Therefore, until time t2, transistor 6 is off and relay 5 is not turned on. Voltage V2 is v with respect to reference voltage V3
2> When V3 is reached, the output of the comparator 8 becomes 811 at IIJJt2, and the switching transistor 6
is turned on and relay 5 is closed. Also, at the same time::
The protective operation in the inverter (j (, IN ■) protection circuit 11 is turned off. This causes the DC/AC fi conversion circuit I1.N Y to operate. When the power supply voltage is turned off, the DC At time t3, when the voltage vDc decreases and the voltage V2 becomes V<V3 with respect to the reference voltage V3, the output of the comparator 8 becomes IQI, so the switching transistor 6 is turned off and 5+L-5 is opened. Ru.

Here, the output voltage v1 of the DC/DC converter 4 is determined at time t4 when the DC voltage vDo decreases to approximately 24 (Vl).
This is a case where the power supply voltage is normally turned on/off by the operation of 8 or more, which is maintained almost constant until When v2<v3, the switching transistor 6 is turned off and the relay 5 is opened, as described above.

Furthermore, if v2)v8 is established at time t6, the switching transistor 6 is turned on and the relay 5 is turned on. In this way, the relay 5 can be opened even with a slight drop in the power supply voltage, and even if the power supply voltage recovers, the voltage v2 will be smaller than the reference voltage V2>v3.
Until the relay 5 is turned on, the capacitor CD is charged via the resistor RD without the relay 5 being turned on, so that the inrush current caused by the capacitor CI when the relay 5 is turned on can be reduced.

[Effects of the Invention] As explained above, according to the present invention, AC voltage is rectified, the rectified piezoelectric voltage is supplied to a capacitor through a parallel connection circuit of a resistor and a switching means, and the capacitor smoothes the rectified piezoelectric voltage. In an inverter that converts this DC voltage back into an AC voltage using a DC/AC conversion circuit, a voltage conversion means for converting the DC voltage into a low-voltage DC voltage, and a DC voltage obtained across the capacitor are predetermined. a detection means for detecting whether or not the constant voltage is higher than a constant voltage, and a detection means for turning on/off the opening/closing means according to the output of the detection means.
Since it is constituted by a control means that performs OFF control, the opening/closing means can be opened when the power supply voltage drops instantaneously, and when the power supply voltage is restored again, the opening/closing means is turned on with a delay. Capacitor I: Can reduce inrush current caused by capacitor I. As a result, damage to the rectifying element due to rush current can be prevented. Furthermore, the above operation can be performed using only a few components (in the embodiment, the transistor 6) in the conventional circuit configuration.
This can be done at a very low cost since it is only necessary to add First, chattering can be improved by applying a low-voltage direct current to the opening/closing means.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a one-piece weaving example of the present invention, FIG. 2 is a waveform diagram showing voltage waveforms of each part of the circuit in FIG. 1, and FIGS. 3 (A) to (C) are each FIG. 1 is a block diagram showing the configuration of a conventional inverter circuit. SR... Rectifier circuit RD... Resistor R... Relay coil r... Relay R contact CD... Capacitor 1 ■N'v. ...DC/AC conversion circuit 4...
...DC/DC converter 6...Switching transistor 7...Attenuator 80806. Comparator 9...Resistance.

Claims (1)

[Claims] The AC voltage is rectified, the rectified voltage is supplied to a capacitor via a parallel connection circuit of a resistor and a switching means, smoothed by this capacitor, and this DC voltage is converted to AC again by a DC/AC conversion circuit. In an inverter that converts the DC voltage into a voltage, a voltage conversion means converts the DC voltage into a low-voltage DC voltage, and a detection means detects whether the DC voltage obtained across the capacitor is higher than a predetermined constant voltage. and a control means for controlling on/off of the opening/closing means according to the output of the detection means.