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| 型号： | TC665EUN |
| 元件分类： | 运动控制电子 |
| 英文描述： | BRUSHLESS DC MOTOR CONTROLLER, PDSO10 |
| 封装： | PLASTIC, MSOP-10 |
| 文件页数： | 2/36页 |
| 文件大小： | 695K |
| 代理商： | TC665EUN |
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TC664/TC665
DS21737A-page 10
2002 Microchip Technology Inc.
4.1
Fan Speed Control Methods
The speed of a DC brushless fan is proportional to the
voltage across it. For example, if a fan’s rating is
5000 RPM at 12 V, it’s speed would be 2500 RPM at
6 V. This, of course, will not be exact, but should be
close.
There are two main methods for fan speed control. The
first is pulse width modulation (PWM) and the second
is linear. Using either method the total system power
requirement to run the fan is equal. The difference
between the two methods is where the power is con-
sumed.
The following example compares the two methods for
a 12 V, 120 mA fan running at 50% speed. With 6 V
applied across the fan, the fan draws an average cur-
rent of 68 mA. Using a linear control method, there is
6V across the fan and 6V across the drive element.
With 6 V and 68 mA, the drive element is dissipating
410 mW of power. Using the PWM approach, the fan is
modulated at a 50% duty cycle, with most of the 12 V
being dropped across the fan. With 50% duty cycle, the
fan draws an RMS current of 110 mA and an average
current of 72 mA. Using a MOSFET with a 1
RDS(on)
(a fairly typical value for this low current) the power dis-
sipation in the drive element would be: 12 mW (Irms2 *
RDS(on)). Using a standard 2N2222A NPN transistor
(assuming a Vce-sat of 0.8 V), the power dissipation
would be 58 mW (Iavg* Vce-sat).
The PWM approach to fan speed control causes much
less power dissipation in the drive element. This allows
smaller devices to be used and will not require any spe-
cial heatsinking to get rid of the power being dissipated
in the package.
The other advantage to the PWM approach is that the
voltage being applied to the fan is always near 12 V.
This eliminates any concern about not supplying a high
enough voltage to run the internal fan components
which is very relevant in linear fan speed control.
4.2
PWM Fan Speed Control
The TC664/TC665 devices implement PWM fan speed
control by varying the duty cycle of a fixed frequency
pulse train. The duty cycle of a waveform is the on time
divided by the total period of the pulse. For example,
given a 100 Hz waveform (10 msec.) with an on time of
5.0 msec., the duty cycle of this waveform is 50%
(5.0 msec./10.0 msec.). An example of this is shown in
FIGURE 4-2:
Duty Cycle Of A PWM
Waveform.
The TC664/TC665 devices generate a pulse train with
a typical frequency of 30 Hz (CF = 1 F). The duty cycle
can be varied from 30% to 100%. The pulse train gen-
erated by the TC664/TC665 devices drives the gate of
an external N-channel MOSFET or the base of an NPN
transistor (Figure 4-3). See Section 7.5 for more infor-
mation on output drive device selection.
FIGURE 4-3:
PWM Fan Drive.
By modulating the voltage applied to the gate of the
MOSFET Qdrive, the voltage applied to the fan is also
modulated. When the VOUT pulse is high, the gate of
the MOSFET is turned on, pulling the voltage at the
drain of Qdrive to zero volts. This places the full 12 V
across the fan for the Ton period of the pulse. When the
duty cycle of the drive pulse is 100% (full on, Ton = T),
the fan will run at full speed. As the duty cycle is
decreased (pulse on time “Ton” is lowered), the fan will
slow down proportionally. With the TC664/TC665
devices, the duty cycle can be controlled through the
analog input pin (VIN), or through the SMBus interface,
by using the Duty-Cycle Register. See Section 4.5 for
more details on duty cycle control.
T
Ton
Toff
T = Period
T = 1/F
F = Frequency
D = Duty Cycle
D = Ton / T
FAN
12 V
Qdrive
TC664
TC665
VDD
GND
VOUT
G
D
S
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TC665EUNTR | 功能描述:马达/运动/点火控制器和驱动器 Single RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube |
| TC67 | 功能描述:铝质电解电容器 - 带引线 40uF 350V RoHS:否 制造商:Kemet 引线类型: 电容:220 uF 容差:20 % 电压额定值:25 V 工作温度范围: 端接类型:Radial 外壳直径:8 mm 外壳长度:11 mm 引线间隔:5 mm 产品:General Purpose Electrolytic Capacitors 封装:Bulk |
| TC670 | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:Tiny Predictive Fan Failure Detector |
| TC670_03 | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:Tiny Predictive Fan Failure Detector |
| TC670_13 | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:Tiny Predictive Fan Failure Detector |
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