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参数资料
| 型号： | TPS61500PWP |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | 5 A SWITCHING REGULATOR, 2640 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封装： | GREEN, PLASTIC, HTSSOP-14 |
| 文件页数： | 4/21页 |
| 文件大小： | 725K |
| 代理商： | TPS61500PWP |
COMPUTING THE MAXIMUM OUTPUT CURRENT
p
1
I =
1
L
Fs
+
Vout + V
Vin
é
ù
ê
ú
÷
-
è
(4)
(
)
-
h
lim
p
LED_max
Vin × I
I /2
I
=
Vout
(5)
SELECTING THE INDUCTOR
SLVS893 – DECEMBER 2008 ........................................................................................................................................................................................... www.ti.com
For optimum performance, the value of C5 is recommended as large as possible to provide adequate filtering for
the PWM frequency. For example, when the PWM frequency is 5-kHz, C5 equal to 1-
F is sufficient.
The over-current limit in a boost converter limits the maximum input current and thus maximum input power for a
given input voltage. Maximum output power is less than maximum input power due to power conversion losses.
Therefore, the current limit setting, input voltage, output voltage and efficiency can all change maximum current
output. The current limit clamps the peak inductor current, therefore the ripple has to be subtracted to derive
maximum DC current. The ripple current is a function of switching frequency, inductor value and duty cycle. The
following equations take into account of all the above factors for maximum output current calculation.
Where
Ip = inductor peak to peak ripple
L = inductor value
V = Schottky diode forward voltage
Fs= switching frequency
Vout= output voltage =
Σ VLEDs + VREF
Where
ILED_max = maxium LED current from the boost converter
Ilim = over current limit
VLED = LED forward voltage at ILED
η = efficiency estimate based on similar applications
For instance, when VIN is 12-V, 8 LEDs output is equivalent to Vout of 24V, the inductor is 10-
H, the Schottky
forward voltage is 0.4-V and the switching frequency is 1.2-MHz; then the maximum output current is around 1-A
in typical condition.
The selection of the inductor affects steady state operation as well as transient behavior and loop stability. These
factors make it the most important component in power regulator design. There are three important inductor
specifications, inductor value, DC resistance and saturation current. Considering inductor value alone is not
enough.
Inductor values can have ±20% tolerance with no current bias. When the inductor current approaches saturation
level, its inductance can falls to some percentage of its 0-A value depending on how the inductor vendor defines
saturation current.
Using an inductor with a smaller inductance value forces discontinuous PWM where the inductor current ramps
down to zero before the end of each switching cycle. This reduces the boost converter’s maximum output
current, causes large input voltage ripple and reduces efficiency. In general, large inductance value provides
much more output and higher conversion efficiency. Small inductance value can give better the load transient
response. For these reasons, a 4.7
H to 22H inductor value range is recommended. Table 2 lists the
recommended inductor for the TPS61500.
Meanwhile, the TPS61500 can program the switching frequency. Normally, small inductance value is suitable for
high frequency and vice versa. The device has built-in slope compensation to avoid sub-harmonic oscillation
associated with current mode control. If the inductor value is lower than 4.7
H, the slope compensation may not
be adequate, and the loop can be unstable. Therefore, customers need to verify the inductor in their application if
it is different from the recommended values.
12
Copyright 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS61500
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TPS61500PWP | 制造商:Texas Instruments 功能描述:LED Driver IC 制造商:Texas Instruments 功能描述:IC, LED DRIVER, BOOST, HTSSOP-14 |
| TPS61500PWPR | 功能描述:LED照明驱动器 High Brightness LED Driver RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| TPS615B(F) | 制造商:Toshiba America Electronic Components 功能描述: |
| TPS615C(F) | 制造商:Toshiba America Electronic Components 功能描述: |
| TPS615F | 制造商:TOSHIBA 制造商全称:Toshiba Semiconductor 功能描述:Silicon NPN Epitaxial Planar |
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