JP2003116299A - Current detecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit, a method and an apparatus for detecting a motor current with high accuracy constantly regardless of the stoppage/rotation of a motor while suppressing a time lag. SOLUTION: The motor current detecting circuit comprises A/D conversion means (10A, 10B and 10C) of phase currents (Iu, Iv and Iw) of a three-phase motor, means (11A, 11B and 11C) for amplifying the phase current values converted digitally, and a D/A conversion means (13) of digital/analogue- converting the sum of outputs from the amplifying means (11A, 11B and 11C) wherein the output signal from the D/A conversion means (13) is detected as the current signal (IM) of an equivalent DC machine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detection circuit device for detecting a motor current of an equivalent DC machine, and more particularly to a novel method for digitally processing a detection signal to enable high speed and highly accurate detection. Regarding improvement.

[0002]

2. Description of the Related Art As a conventional device of this type, for example, the configuration of a motor current detection circuit shown in FIG. 2 can be mentioned. That is, in FIG. 2, what is indicated by reference numeral 1 is a full-wave rectifier, and this full-wave rectifier 1 is a three-phase current U detected by a motor (not shown).
Three phase currents (Iu), V-phase currents (Iv) and W-phase currents (Iw) are provided for full-wave rectification.

Three full-wave rectified by the full-wave rectifier 1
The phase signals are input to the smoothing circuit 2 after the sum is taken. In this way, the sum 2a of the three-phase signals filtered by the smoothing circuit 2 is detected as the current signal (I _M ) of the equivalent DC machine.

[0004]

Since the conventional device is constructed as described above, the following problems exist. FIG. 3 is a three-phase current waveform (FIG. 3A) in the conventional motor current detection circuit shown in FIG. 2, a waveform after full-wave rectification (FIG. 3B), and a combined waveform after smoothing (FIG. c)) respectively. As shown in this FIG.
While the motor (not shown) is rotating, as shown in FIG.
As shown in (b), there are problems that ripples occur and that waveforms have a time delay.

The present invention has been made in order to solve the above problems and, in particular, has a small time delay and is capable of detecting a constant and highly accurate motor current regardless of whether the motor is stopped or rotating. An object of the present invention is to provide a motor detection circuit and a method device capable of performing the same.

[0006]

SUMMARY OF THE INVENTION A motor current detection circuit according to the present invention includes an A / D conversion means for analog / digital converting the current of each phase of a three-phase motor, and the digitally converted current value of each phase. The configuration is such that it includes amplification means for amplification and D / A conversion means for converting the sum of the outputs of the amplification means into digital / analog, and the output signal of the D / A conversion means is detected as a current signal of an equivalent DC machine. Further, the amplification means is configured to square the current value of the digitally converted current of each phase and output the squared value.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a motor detection circuit and method according to the present invention will be described in detail below with reference to the drawings. The same or equivalent parts as those of the conventional device are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 1, the motor detection circuit and method of the present invention A / D-converts a three-phase current consisting of a U-phase current (Iu), a V-phase current (Iv) and a W-phase current (Iw). Bowl 10A, 10
A / D conversion with B and 10C, and further amplifiers 11A and 11
Amplify at B and 11C respectively. Amplifiers 11A to 11
In C, each current value is squared. The squared outputs are added by the adder 12, and the sum 12a is D / A.
Those analog form by converter 13 is detected as a current signal equivalent DC motor (I _M). Current signal of this equivalent DC machine
(IM) is represented by I _M = (Iu ² + Iv ² + Iw ² ) × 2/3.

As described above, according to the motor current detection circuit of the present invention, by the digital signal processing, the motor current I _{M is} calculated only by a simple calculation regardless of whether the motor is stopped or rotating. Therefore, it is possible to provide a motor current detection circuit that can detect the motor current I _M at high speed and with high accuracy.

[0010]

The motor current detection circuit of the present invention is an A / D for analog / digital converting the current of each phase of a three-phase motor.
The conversion means, amplification means for amplifying the digitally converted current value of each phase, and D / A conversion means for digital / analog conversion of the sum of the outputs of the amplification means are provided.
And it detects an output signal of the A converter as a current signal equivalent dc machine can detect the motor current I _M at high speed and high precision. Further, since the amplifying means squares the current value of the digitally converted current of each phase and outputs the squared value, it is possible to provide a motor current detection circuit in which the detection accuracy of the motor current is significantly improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a motor current detection circuit according to the present invention.

FIG. 2 is a configuration diagram schematically showing a conventional motor current detection circuit.

FIG. 3 is a characteristic diagram schematically showing each current waveform in a conventional motor current detection circuit.

[Explanation of symbols]

10A, 10B, 10C A / D converter 11A, 11B, 11C amplifier 12 adder 13 D / A converter

Claims (2)

[Claims] 1. A / D conversion means (10A, 10B, 10) for analog / digital conversion of currents (Iu, Iv, Iw) of respective phases of a three-phase motor.
C), amplification means (11A, 11B, 11C) for amplifying the digitally converted current value of each phase, and the amplification means (11A, 11B, 11C)
D / A for digital / analog conversion of sum (12a) of output of
And a converting means (13), the D / A motor current detection circuit and detecting an output signal as an equivalent DC motor current signal (I _M) of the conversion means (13). 2. The amplifying means (11A, 11B, 11C) squares and outputs the current value of the digitally converted current (Iu, Iv, Iw) of each phase. The described motor current detection circuit.