JP2002359921A - Overvoltage-protecting circuit and motor controller mounted thereon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overvoltage-protecting circuit and a motor controller which have high reliability and has no risk of performing unsafe operations, even if an overvoltage is applied owing to incorrect connection of an input power source, etc. SOLUTION: Safety problems related to a smoothing capacitor 4 can be prevented, since a discharging surge absorber 8 turns into a discharging state, and the terminal voltage of the smoothing capacitor 4 is suppressed to a low voltage, when an unusual voltage is applied owing to unusual connection of the input power source and so on, by connecting the surge absorber 8 between an inrush current which suppresses a resistor 9a and the smoothing capacitor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overvoltage protection circuit, and more particularly to a motor control device having an overvoltage protection circuit.

[0002]

2. Description of the Related Art A conventional motor control apparatus converts an AC input into a DC output, converts the AC input into a DC output, uses the DC voltage as a power source to perform a switching operation of an inverter unit, controls a voltage applied to the motor, and controls a motor current. ing.

As shown in FIG. 4, an input power supply 1 is rectified by rectifying means 2 and connected to a smoothing capacitor 4 through an inrush current suppressing resistor 3 so that the peak value of the input power supply 1 is applied to both ends of the smoothing capacitor 4. Is obtained. In the driving means 5, the motor control is realized by controlling the current flowing through the motor 6 by performing a switching operation of the DC voltage across the smoothing capacitor 4.

[0004]

However, in the above-mentioned conventional configuration, for example, an AC 1
200V AC to motor control device designed to 00V
Is connected, the voltage at both ends of the smoothing capacitor exceeds the withstand voltage, the inrush current suppressing resistor and the smoothing capacitor abnormally generate heat, and the vaporized flammable electrolyte is ejected from the smoothing capacitor. Problems could occur.

The present invention solves such a conventional problem. Even if an overvoltage is applied due to an erroneous connection of an input power supply or the like, there is no possibility of occurrence of unsafe and a highly reliable overvoltage protection circuit and motor. It is an object to provide a control device.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a rectifying means for an input power supply, an inrush current suppressing / cutting means connected to one output of the rectifying means, and an inrush current suppressing means. A discharge type surge absorber connected to the output of the interrupting unit and the other output of the rectifying unit, a diode connected to the output of the inrush current suppressing and interrupting unit, and an output of the diode and the other output of the rectifying unit. Connected to a smoothing capacitor, wherein the operating voltage of the discharge type surge absorber is set within a range of not less than the rated voltage of the smoothing capacitor and not more than the active voltage, and the voltage at both ends of the smoothing capacitor exceeds the withstand voltage. Since the voltage can be suppressed to a low voltage within a non-existent range, occurrence of unsafety can be prevented.

[0007]

In order to solve the above-mentioned problems, an overvoltage protection circuit according to a first aspect of the present invention comprises:
An inrush current suppressing and interrupting means connected to one output of the rectifying means; an output of the inrush current suppressing and interrupting means and a discharge surge absorber connected to the other output of the rectifying means; and the inrush current suppressing and interrupting means And a smoothing capacitor connected to the output of the diode and the other output of the rectifier. The operating voltage of the discharge type surge absorber is equal to or higher than the rated voltage of the smoothing capacitor and equal to or lower than the active voltage. When the voltage at both ends of the smoothing capacitor attempts to exceed the set voltage of the discharge surge absorber even if an overvoltage is applied by mistake, the discharge surge absorber starts discharging. Therefore, the voltage across the smoothing capacitor can be suppressed to a low voltage such as 15V.

The overvoltage protection circuit according to claim 2 is
The inrush current suppressing and interrupting means is constituted by at least a resistor or a current interrupting fuse connected in series with the resistor. In addition to claim 1, the input overcurrent can be interrupted by the current interrupting fuse.

The overvoltage protection circuit according to claim 3 is
The inrush current suppressing and interrupting means is constituted by at least a resistor and a temperature cutoff type fuse which is connected in series to the resistor and is thermally coupled thereto. Can be shut off.

Further, in the motor control device using the overvoltage protection circuit according to any one of claims 1 to 3, even if an overvoltage is improperly applied, unsafety does not occur and high reliability is obtained. Can be.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) In FIG. 1, an input power supply 1 is connected to a rectifying means 2, and a positive voltage output is output to an output terminal 201 and a negative voltage output is output to an output terminal 202. The positive voltage output 201 is connected to the input terminal 901 of the inrush current suppression and interruption means 9 constituted by the inrush current suppression resistor 9a and the current interruption type fuse 9b.

The output terminal 902 of the inrush current suppressing and interrupting means 9
Is connected to one terminal 801 of the discharge type surge absorber 8 and the anode of the diode 10, and the cathode of the diode 10 is connected to the positive electrode terminal 401 of the smoothing capacitor 4. The negative voltage output 202 of the rectifier 2 is connected to the other terminal 802 of the surge absorber 8 and the negative electrode terminal 402 of the smoothing capacitor 4.

By the way, the input power supply 1 is 100 V AC.
If the smoothing capacitor 4 is designed with a rated voltage of 1
60V (200V surge voltage, 220V active voltage)
Type is usually used. Although a voltage with a higher rated voltage, for example, 350 V, can be used, the one with the minimum required voltage is generally selected because the shape becomes large and the price increases.

When an AC power of 100 V is connected as an input power source, the inrush current suppression and cutoff means 9 and the diode 1
0, both ends of the smoothing capacitor 4 are charged to about 140 VDC, which is a peak value of 100 VAC, and the driving means 5 performs a switching operation by using the dc voltage as a power supply to change the current flowing through the motor 6 to control the motor. Realize.

However, if AC 200 V is accidentally connected to a place where AC 100 V is connected, both ends of the smoothing capacitor 4 are passed through the rush current suppression and cut-off means 9 and the diode 10 to reach a peak value of about 280 V DC of AC 200 V. Trying to charge up to

Here, the characteristics of the discharge type surge absorber will be described. FIG. 2 shows the voltage-current characteristics of the discharge surge absorber. The straight line shown in FIG. 2 corresponds to the equivalent impedance on the input side of the discharge surge absorber.

However, the discharge start voltage is selected to be about 180 V so that the discharge type surge absorber 8 operates within the range of not less than the rated voltage of the smoothing capacitor 4 and not more than the active voltage. Immediately after reaching the vicinity, the operating point of the discharge type surge absorber shifts from point A to point B in FIG. 2 to be in a discharge state, and the terminal voltage instantaneously becomes a low voltage such as 15V.

For this reason, the voltage between both ends of the smoothing capacitor 4 is suppressed below the discharge starting voltage of the discharge type surge absorber 8, and a large current such as 30A flows through the inrush current suppressing and interrupting means 9, and the internal inrush current suppressing resistor 9a Or the current fuse 9b is blown to cut off the current flowing from the input power supply.

Further, when the discharge type surge absorber 8 discharges and shifts to a low voltage at both ends, the diode 10
It is provided to prevent the energy accumulated in the smoothing capacitor 4 from flowing back to the discharge type surge absorber 8 and destroying the discharge type surge absorber 8.

Thus, the smoothing capacitor can be protected from overvoltage, and the driving means can be similarly protected.

(Embodiment 2) In Embodiment 2, an inrush current suppressing resistor and a temperature cutoff type fuse are connected in series as inrush current suppressing and interrupting means.

Referring to FIG.
Are electrically connected in series with the rush current suppressing resistor 9a and the temperature cutoff fuse 9c disposed close to the resistor 9a.

As in the first embodiment, the voltage at both ends of the discharge type surge absorber 8 once exceeds the discharge starting voltage due to erroneous connection of the input power supply 1 or the like, and the discharge type surge absorber 8 enters a discharge state, and the voltage at both ends becomes low. When the voltage instantaneously shifts to a low voltage such as 15 V, the inrush current suppressing resistor 9a constituting the inrush current suppressing and interrupting means 9 becomes extremely high. In the second embodiment, this heat is transmitted to the temperature interrupting fuse 9c, When the operating temperature of the cut-off type fuse 9c is exceeded, the temperature cut-off type fuse 9c is cut off, and the inrush current suppressing resistor 9c is turned off.
Since the current flowing through a is cut off and the current flowing from the input power supply 1 is also cut off, the smoothing capacitor 4 and the driving means 5 can be protected from overvoltage.

In the second embodiment, the switch 7 is provided, which is effective particularly in the case of a large output device. When the power is turned on, the switch 7 is opened, the rush current is suppressed, and the driving means 5 operates. When the state is reached, by closing the switch 7, the heat generation of the inrush current suppression resistor 9 a of the inrush current suppression interrupting means 9 can be suppressed.

[0026]

As is apparent from the above embodiment, according to the first aspect of the present invention, since the discharge type surge absorber and the diode are provided, energy flows backward from the smoothing capacitor to destroy the discharge type surge absorber. Without
It is possible to reliably suppress the input voltage abnormality to be equal to or lower than the activation voltage of the smoothing capacitor and protect the smoothing capacitor from overvoltage.

According to the second aspect of the present invention, in addition to the effect of the first aspect, when the discharge type surge absorber operates, the input current is controlled by the resistor or the current interrupting fuse connected in series to the resistor. Can be shut off, so safety can be ensured.

According to the third aspect of the present invention, when the discharge type surge absorber operates, the input current can be cut off by detecting the heat generation of the resistor by the temperature cutoff fuse connected in series with the resistor. Therefore, safety can be ensured.

Further, by mounting the overvoltage protection circuit according to any one of claims 1 to 3, there is provided a highly reliable motor control device without the possibility of occurrence of unsafe against overvoltage. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a motor control device according to a first embodiment of the present invention.

FIG. 2 is a voltage-current characteristic diagram of a discharge type surge absorber according to the present invention.

FIG. 3 is a configuration diagram of a motor control device according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional motor control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input power supply 2 Rectifying means 4 Smoothing capacitor 7 Switch 8 Discharge type surge absorber 9 Inrush current suppression cutoff means 9a Inrush current suppression resistor 9b Current cutoff fuse 9c Temperature cutoff fuse 10 Diode

Continued on the front page F term (reference) 5G013 AA17 BA02 CB04 DA03 5G053 AA05 AA09 CA06 EB01 EC05 FA04 5G065 BA01 EA06 GA02 HA05 HA17 MA03 NA01 5H006 BB05 CA07 CC08 FA02 GA01 5H740 BA18 BB05 BB08 BB10 MM01 MM12

Claims (4)

[Claims] 1. A rectifier for an input power supply, an inrush current suppression and cutoff connected to one output of the rectifier, and an output of the inrush current suppression and cutoff connected to the other output of the rectifier. A discharge-type surge absorber, a diode connected to the output of the inrush current suppression and cut-off means, and a smoothing capacitor connected to the output of the diode and the other output of the rectifying means; An overvoltage protection circuit whose voltage is set within the range of the rated voltage of the smoothing capacitor and the active voltage. 2. The overvoltage protection circuit according to claim 1, wherein the inrush current suppressing and interrupting means comprises at least a resistor or a current interrupting fuse connected in series with the resistor. 3. The overvoltage protection circuit according to claim 1, wherein the inrush current suppressing / cutting means is constituted by at least a resistor and a temperature cutoff fuse thermally connected in series with the resistor. 4. A motor control device equipped with the overvoltage protection circuit according to claim 1.