ZXBM200X Просмотр технического описания (PDF) - Diodes Incorporated.

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ZXBM200X

ZXBM200x SERIES OF VARIABLE SPEED 2-PHASE FAN MOTOR CONTROLLER

Diodes Incorporated. 

Applications Note AN36

Issue1 - JULY 2002

Figure 19

Failsafe dual fan system.

In Figure 19 the SPD pin on both fans is

arranged such that they run at half speed, or

perhaps a little faster with R6 and R3.

Consider Fan A, R1 and C1 integrate out the

FG frequency pulses such that Q1 is always

kept off. If a lock condition is then

encountered with the fan the Lock/FG pin will

go permanently high and switch on Q1. This

in turn will send a signal to Fan B such that it

will switch R2 to ground. With the value of R2

chosen such that the SPD voltage of Fan B is

<1V it will ensure Fan B is set to full speed to

compensate to the now stopped Fan A.

Conversely R4, C4, Q2 and R5 will ensure that

if Fan B stops Fan A will be set to full speed.

By careful selection of the values of R1/C1 and

R4/C4 it is possible to only partially take out

the FG speed pulses. This will make one fan

speed up should the other slow down

sufficiently but not actually stop. To remove

the need for C1 and C4 the ZXBM2002 variant

with the Lock only output can be used so the

FG pulses do not need to be removed.

SPD Voltage Conversion

There may be situations where the SDP input

control voltage range will be incompatible

with the application requirements perhaps

because the motor is to be controlled from an

already defined and different voltage source.

Figure 20 provides a simple voltage range

conversion for a control signal where a higher

voltage represents a higher speed.

Figure 20

SPD control voltage level conversion.

AN 36 - 12

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