JP2004294169A - Voltage detection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage detection circuit having a small number of fault occurrence in maintenance/inspection. <P>SOLUTION: Wires 20, 22 are connected to terminals 10a, 10b in a smoothing capacitor 10, respectively, resistors 26, 24 are inserted into the wires 20, 22, respectively, and further voltage detection pins 30, 32 are connected to the tips of the wires 20, 22, respectively. When a maintenance worker inspects the voltage of the smoothing capacitor 10 for preventing electric shock, current flows to resistors 24, 26, flow of an overcurrent to a control circuit 1 is prevented and the number of fault occurrence is reduced even if metering rods 92, 94 contact each other for causing short-circuiting or the metering rod 92 in contact with the voltage detection pin 30 at a non-grounded side comes into contact with a grounded section for causing short-circuiting while the metering rods 92, 94 in a voltmeter 90 are in contact with the voltage detection pins 30, 32, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for reducing failures in maintenance and inspection of a cooling device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, when a control board of an electrical component in a cooling device such as an air conditioner has failed, it has been necessary to replace it. Such replacement is exemplified in, for example, Patent Document 1. In addition to such replacement work, in general, when disassembling the electrical component, a voltage check of a charged portion is usually performed before the work to prevent an electric shock accident.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. Hei 10-300177
[Problems to be solved by the invention]
In the voltage checking operation, a pair of measuring rods of the voltmeter are brought into contact with the terminals of the electrical unit. However, in this state, if a pair of measuring rods come into contact with each other, a short circuit occurs, and if one of the measuring rods contacts a grounded portion such as a chassis in the same state, a ground fault may occur. These could have caused the cooling device to fail.
[0005]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a power detection circuit with less failure during maintenance and inspection.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a pair of detection terminals connected to each of a pair of terminals in a charging unit provided in a circuit of a cooling device, and a pair of terminals. Each of the pair of corresponding power detection terminals, a pair of wires connecting the pair of terminals, and a resistor provided on at least one of the pair of wires.
[0007]
The invention according to claim 2 is the power detection circuit according to claim 1, wherein one of the pair of terminals is a grounded terminal that is grounded, and the other is an ungrounded terminal that is not grounded. The resistor is provided on the wiring connected to the non-ground side terminal.
[0008]
Further, the invention according to claim 3 is the power detection circuit according to claim 2, wherein a resistor different from the resistor is provided on the wiring connected to the ground terminal.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a circuit diagram mainly showing a control circuit 1 of an inverter air conditioner provided with a power detection circuit 50 according to an embodiment of the present invention.
[0010]
In the control circuit 1, a diode module 6 including diodes 6 a, 6 b, 6 c, 6 d, 6 e, and 6 f is connected to an AC power supply 2 via a switch 4. Further, in parallel with the diode module 6, a smoothing capacitor 10 as a charging unit and an inverter circuit 12 are connected. Further, among the wirings 16 and 18 connecting the diode module 6 and the inverter circuit 12, the wiring 18 is grounded, and the wiring 16 is not grounded. The wiring 16 is connected to the cathodes of the diodes 6a, 6b, 6c, and the wiring 18 is connected to the anodes of the diodes 6d, 6e, 6f. Therefore, hereinafter, the terminal connected to the wiring 16 of the smoothing capacitor 10 is referred to as a high-voltage terminal 10a, and the terminal connected to the wiring 18 is referred to as a ground terminal 10b. The high-voltage side terminal 10a can be understood as an ungrounded side terminal in the sense that it is not grounded.
[0011]
The inverter circuit 12 includes transistors 12a, 12b, 12c, 12d, 12e, and 12f. The compressor drive motor 14 is connected to the inverter circuit 12.
[0012]
During normal operation of the inverter air conditioner, the control circuit 1 performs drive control of a compressor (not shown) as follows. That is, the AC current supplied from the AC power supply 2 is rectified by the diode module 6 and then converted to DC by the smoothing capacitor 10. The DC current is converted into an AC of an arbitrary frequency in an inverter circuit 12 that has been subjected to switching timing control of each transistor by a switching control circuit (not shown), and then supplied to a compressor drive motor 14, whereby The compressor operates.
[0013]
Further, the control circuit 1 is provided with a power detection circuit 50 for measuring the voltage of the smoothing capacitor 10 during maintenance. The power detection circuit 50 includes wirings 20 and 22, resistors 24 and 26, and power detection pins 30 and 32. The wiring 20 is connected to the high-voltage terminal 10 a of the smoothing capacitor 10, and the wiring 22 is connected to the ground terminal 10 b of the smoothing capacitor 10.
[0014]
Resistors 24 and 26 are inserted into the wirings 20 and 22, respectively. Further, the ends of the wirings 20 and 22 are connected to power detection pins 30 and 32 as power detection terminals, respectively.
[0015]
When the maintenance worker needs to disassemble the electric component inside the inverter air conditioner, the switch 4 is turned off. However, since there is a possibility that the smoothing capacitor 10 has been charged, the voltage of the smoothing capacitor 10 is checked in advance to prevent electric shock. Specifically, the measuring rods 92 and 94 of the voltmeter 90 are respectively applied to the detection pins 30 and 32 to measure the voltage.
[0016]
At this time, in a state where the measuring rods 92 and 94 are in contact with the power detection pins 30 and 32, respectively, the measuring rods 92 and 94 come into contact with each other to cause a short circuit, or the measuring rod 92 comes into contact with the grounding portion to ground. Even when a short circuit occurs, the charge charged in the smoothing capacitor 10 flows through the resistors 24 and 26. Therefore, it is possible to prevent an excessive current from flowing through the inverter air conditioner and the control circuit 1, and it is possible to reduce the occurrence of failure of the cooling device during maintenance and inspection.
[0017]
In particular, since the resistor 24 is provided on the wiring 20 connected to the high-voltage side terminal 10a, the current due to the ground fault can be effectively reduced.
[0018]
Because of such effects, it is desirable that the resistors 24 and 26 have a resistance value according to the capacity of the charging unit (the smoothing capacitor 10 in this embodiment). For example, when three 860 μF capacitors are provided as the smoothing capacitor 10, the resistors 24 and 26 have a power consumption of about 1/2 W and a resistance of about 200 KΩ.
[0019]
In this embodiment, the power detection circuit 50 provided in the control circuit 1 of the inverter air conditioner is shown as an example of the power detection circuit, but the present invention is not limited to this.
[0020]
For example, a similar power detection circuit may be provided in a charging unit of another cooling device such as a refrigerator or a freezer as a cooling device. Further, the present invention can be applied to a charging unit other than the cooling device.
[0021]
In addition, in the power detection circuit 50 of this embodiment, the resistors 24 and 26 are provided on both of the wirings 20 and 22, but may be provided only on one of them. In particular, even if only the resistor 24 on the non-ground side is provided and no resistor is provided on the ground side, the same effect as that of the voltage detection circuit 50 of this embodiment can be obtained.
[0022]
【The invention's effect】
As described above, according to the first to third aspects of the present invention, for example, when measuring the voltage of the charging unit using a voltmeter, a pair of measuring rods of the voltmeter are connected to a pair of power detection terminals. Even if the measuring rods are in contact with each other and a short circuit occurs, the current flows through the resistor, preventing the flow of excessive current. Can be reduced.
[0023]
According to the second aspect of the present invention, when measuring the voltage of the charging section using a voltmeter, the measuring rod in contact with the non-grounded detection terminal of the voltmeter comes into contact with the grounding portion. Even when a ground fault occurs, an excessive current can be prevented from flowing by flowing the current through the resistor, and the occurrence of a failure of the cooling device in maintenance and inspection can be further reduced.
[0024]
Furthermore, according to the third aspect of the present invention, it is possible to prevent any of the above-mentioned short-circuit and excessive current due to ground fault at the time of voltage measurement, so that the occurrence of failure of the cooling device in maintenance and inspection can be further reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram mainly showing a control circuit 1 of an inverter air conditioner provided with a power detection circuit according to an embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 10 Smoothing capacitor 10a High-side terminal 10b Ground-side terminal 20,22 Wiring 24,26 Resistor 30,32 Test pin 50 Test circuit

Claims (3)

A pair of power detection terminals (30, 32) connected to the pair of terminals (10a, 10b) in the charging section (10), respectively;
A pair of wirings (20, 22) connecting the pair of terminals and the pair of terminals, respectively, corresponding to the pair of terminals;
And a resistor (24, 26) provided on at least one of the pair of wirings. The power detection circuit according to claim 1,
One of the pair of terminals is a grounded terminal (10b) that is grounded, and the other is an ungrounded terminal (10a) that is not grounded,
An electric detection circuit, wherein the resistor (24) is provided on the wiring (20) connected to the non-ground side terminal. The voltage detection circuit according to claim 2, further comprising:
A power detection circuit, wherein a resistor (26) different from the resistor is provided on the wiring (22) connected to the ground terminal.

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