TDA5142 Ver la hoja de datos (PDF) - Philips Electronics

Número de pieza

componentes Descripción

Fabricante

TDA5142

Brushless DC motor drive circuit

Philips Electronics 

Philips Semiconductors

Brushless DC motor drive circuit

If the movement of the motor generates enough EMF the

TDA5142T will run the motor. If the amount of EMF

generated is insufficient, then the motor will move one step

only and will oscillate in its new position. The amplitude of

the oscillation must decrease sufficiently before the arrival

of the next start pulse, to prevent the pulse arriving during

the wrong phase of the oscillation. The oscillation of the

motor is given by:

fosc

=

----------------1------------------

2π -K----t---×---J-I---×-----p--

where:

Kt = torque constant (N.m/A)

I = current (A)

p = number of magnetic pole-pairs

J = inertia J (kg.m2).

Example: J = 72 × 10−6 kg.m2, K = 25 × 10−3 N.m/A, p = 6

and I = 0.5 A; this gives fosc = 5 Hz. If the damping is high

then a start frequency of 2 Hz can be chosen or

t = 500 ms, thus C = 0.5/2 = 0.25 µF (choose 220 nF).

THE ADAPTIVE COMMUTATION DELAY (CAP-CD AND

CAP-DC)

In this circuit capacitor CAP-CD is charged during one

commutation period, with an interruption of the charging

current during the diode pulse. During the next

commutation period this capacitor (CAP-CD) is discharged

at twice the charging current. The charging current is

8.1 µA and the discharging current 16.2 µA; the voltage

range is from 0.9 to 2.2 V. The voltage must stay within

this range at the lowest commutation frequency of

interest, fC1:

C = -8---.--1f---×-×----1-1--.--03---–---6 = 6---f-2-C--3--1--1- (C in nF)

If the frequency is lower, then a constant commutation

delay after the zero-crossing is generated by the discharge

from 2.2 to 0.9 V at 20 µA;

maximum delay = (0.076 × C) ms (with C in nF)

Example: nominal commutation frequency = 900 Hz and

the lowest usable frequency = 400 Hz; so:

CAP-CD = 6--4--2--0-3--0--1- = 15.6 (choose 18 nF)

The other capacitor, CAP-DC, is used to repeat the same

delay by charging and discharging with 15.5 µA. The same

value can be chosen as for CAP-CD. Figure 7 illustrates

typical voltage waveforms.

June 1994

12

Product specification

TDA5142T

Share Link: