JPS5983592A - Current detecting circuit for brushless motor - Google Patents

Abstract

PURPOSE:To detect a current with a simple configuration by detecting any of the conduction rate of an inverter, the current or a DC voltage of a brushless motor, and calculating the current value not detected from a relation equation of the above three state amounts. CONSTITUTION:A current detecting shunt is arranged in a DC unit of an inverter, and an instantaneous current IDC1 and an average current IDC2 are respectively inputted to the distributors 45 of respective controllers 4 and an A/D converter 41 through an operational amplifier OP having a surge absorbing filter consisting of a resistor R1 and a capacitor C1 and a smoothing filter consisting of a resistor R2 and a capacitor C2 at the output terminal. A position detection signal is applied to the distributors 45 through the waveform shaper 43 of the controllers 4, and a PWM modulation wave generator 44, and supplied to a base drive circuit 5. The reduction rate Df of the inverter is determined by a calculator 42. Then, the motor current IM can be obtained by the detection of the DC current IDC from a relation equation IDC=K1ImDf of the motor current Im, the DC current IDC and the conduction rate Df.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor &L current or DC/DC detection device for a brushless motor control device having arithmetic means.

In a system that operates a brushless motor from a single DC source via an inverter, instantaneous overflow Il! Flow protection negative moe measurement,
In order to perform overcurrent protection of the motor windings, current detection means are required on the motor side and the DC section. Conventionally, the motor current was detected using CT, etc., and the DC current was detected using a shunt. A method of direct measurement was used. However, since this method requires two measuring elements, it has drawbacks such as a complicated apparatus.

The present invention relates to a brushless motor that supplies power to the motor from a DC power source via an inverter, and has four functions in the control section of the inverter. By detecting either, the remaining current ll! The purpose of the present invention is to calculate and obtain L and provide first-stream detection with a simple configuration.

This @Akira is motor 4#, I M, DC @, I Dc
) Accordingly, one of the motor current or the DC current is measured, and the remaining current is calculated using a certain relational expression.

Hereinafter, the present invention will be explained with reference to the drawings. FIG. 1 shows the main configuration of a general brushless motor. The main circuit is DC I! The configuration is such that power is supplied from a source 1 to a motor 3 via an inverter 2. Here, the motor 3 has a position detector P8 at the end of the shaft, and receives the detection signal from the +iJ control circuit 4.
supplies a switching control wholesale current to the transistor of the inverter 2 corresponding to the rotor position of the motor 3 via the base drive circuit 5.

Figure 2 shows the operation of the Uememi planless motor (a)
, (b), (C) are the signals of the position detector PS, (d) is 3
It is reset at No. 18 every 60 degrees of the position detection signal using the angular carrier wave. (e) is one word created by the slice level in (d), (f) to (k) are Li1tlif4j
It is a signal generated by the output 1 words (a) to (c) and (e)K, which is generated by the 1iIJ+ wholesale circuit 4 and supplied to each phase of the inverter transistor via the base drive circuit 5. (L) shows the motor current flowing due to the above 1ilJ flow, and (M) shows the current waveform of the DC section. Third
The figure shows the operation according to the present invention. Said,
The relationship between the motor current and the DC current using the conduction ratio of the brushless motor configured as shown in FIGS. 1 and 2 as a parameter is shown. From the above experimental results, motor turtle current IM and DC current ID
The following equation approximately holds true between the inverter current ratio 1) f, where l) f is II+ in FIG. 2, /
Il+.

FIG. 4 shows an embodiment of the present invention.

A first current detection shunt SH is placed in the DC section, and the operational amplifier OP
via the instantaneous tortoise flow I D (!I and the average tortoise flow I Dl
:l is supplied to the control circuit 4. Here 1 too.

In the C8C Usage absorption filter, 'a2I C, is a smoothing filter. The control circuit 4 is further provided with an A/i) converter 41 and a JE generator 42. Also, Ichide 1
The information from the δ is sent to the distribution circuit 4 via the waveform shaping circuit 43 in the +1tlJ groaning circuit 4 and the PWM modulated wave generation circuit 1344.
5, it is supplied to the base drive circuit 5. here,
Throughput Dft - Determining slice and bell (Fig. 2(d)
) is performance J1. Take the food from the vessel 42. Based on the above configuration and the principle shown in FIG. 3, the motor current can be solved from the following equation without obtaining any measuring element.

Here, Ot is T + / T t = Ht / H
! H1 Nice level I straight H! Two triangular waves wave height 11! (Known) FIG. 5 shows a comparison between K[I4 obtained by the present invention and an actually measured direct process. As a result, the two correspond in a limited area of the Yosuzuru style.

Based on the above results, it is possible to grasp the motor current by detecting the DC current, and it can be sufficiently used for protection measures such as overcurrent tripping.

According to the present invention, the torrent current in the flow section of the motor section 1f can be detected with a single first-stream detection element, and a brushless motor having a simple configuration can be provided.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a general brushless motor, Fig. 2 is a diagram explaining the operation of the brushless motor, Fig. 3 is a diagram of the principle of the present invention, Fig. 4 is a block diagram of an embodiment of the present invention, and Fig. 5 is a block diagram of a general brushless motor. Similarly to the figure, it is an operation confirmation diagram. 1...fil DW tJX source, 2...inverter, 3...motor. C (11 (C tank 7 ports (rL) ~ Shoes Figure 2

Claims (1)

[Claims] 1. A brushless motor that supplies power to the motor from a single DC source via an inverter, and has means for producing conductivity and means for detecting either DC α current or motor current; Detected product by means, 1) f (conduction rate), Inc (DC α current) or Im (motor tg)
Therefore, for an undetected current, I oc = K 1
I nn D f N hrui Jm=KtInc
A current detection circuit for a brushless motor, characterized in that the current detection circuit is calculated according to the formula /Df.