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參數(shù)資料
| 型號： | GFW |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | Push-Pull Four Channel Drivers(推挽式四通道驅(qū)動器) |
| 中文描述： | 推挽式四通道驅(qū)動器（推挽式四通道驅(qū)動器） |
| 文件頁數(shù)： | 3/8頁 |
| 文件大?。?/td> | 101K |
| 代理商： | GFW |
MULTIPLE SUPPLIES BOOST PERFOR-
MANCE
A dual-levelsupplyalsoimproves the performance
of a basic L/R circuit. A high supply voltage yields
goodtorque characteristics when the motor is run-
ning.Alower-than-ratedvoltageprovidessomehol-
dingtorquewhenthemotorisatrest,therebysaving
power when the motor is idle.
Fig. 2 shows a suitable voltage-switch circuit. R
x
setsthe holdingcurrent, whichcan be low because
a permanentmagnet or hybridsteppermotorprovi-
des some holding torque at zero current. However,
make certain the L293’s motor-supply input never
goes below the logic-supply voltage. While there’s
no dangerof damagingthedevice, it’s imposssible
to drive the output transistorscorrectly under such
conditions.
Thedual bridge’senableinputsofferameansofex-
tendingthe chip’s flexibility. For example, you can
connect them directly to the logic supply - no resi-
storsare needed- to enable thechip permanently.
As an alternative, use the enableinputs to disable
themotor duringthe power-on resetsequence.
In wave-drive and half-stepmodes, use theenable
inputs to increase torque at high speeds. When a
windingde-energizes,flux collapse is a functionof
the current-decay rate. During this decay, the de-
energized winding opposes the efforts of the next
windinginsequence,partiallycancellingthetorque.
You can minimize this effect by disabling a bridge
onlywhen the windingit drivesis turnedoff;becau-
se the
i/
t of an inductor equals E/L, disablingthe
bridgeacceleratesthecurrentdecay.Thisactiondi-
scharges the winding’s stored energy through its
supply and maintains the terminal voltage E at V
s
plustwo diodedrops.Ifyouweretoleavethebridge
enabled, the current would flow to groundthrough
onediodeand onetransistor, anditwouldlower the
terminalvoltage.Thisschemedoesn’tapplywith dri-
veswithtwophasesonbecausenowindingeverde-
energizes.
Figure 2 :
Switching the Supply to a Lower Volt-
age when theMotor is IdleSaves Cur-
rent without Compromising Driving
Power.
Figure 3 :
Maintaining a Constant-averagePhase Current this Fixed-ripple Chopper Provides Improved
Performanceand Efficiency V
REF
ControlsthePhaseCurrent.
APPLICATION NOTE
3/8
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