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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： | 3/21页 |
| 文件大小： | 725K |
| 代理商： | TPS61500PWP |
APPLICATION INFORMATION
PROGRAMMING THE OVERVOLTAGLE PROTECTION
OVP
R1
V
= 1.229 V
+ 1
R2
÷
è
(1)
PROGRAMMING THE LED CURRENT
FB
LED
V
I
=
R3
(2)
IMPLEMENTING DIMMING
PWM Dimming Method
Analog Dimming Method
FB
LED
V
I
=
Duty
R3
(3)
www.ti.com ........................................................................................................................................................................................... SLVS893 – DECEMBER 2008
Select the values of R1 and R2 according to Equation 1.
For example, the total forward voltage of four 3-W LED is 14V, then use R1 of 120k and R2 of 10k to program
the threshold of 16V. In the OVP mode, IC regulates the output voltage at the OVP threshold.
When the fault is clear and the OVP pin voltage falls 40-mV below 1.229V, IC resumes the output regulation for
LED current.
LED current can be determined by the value of the feedback resistor R3 and the FB pin regulation voltage of
200-mV as shown in Equation 2:
The output current tolerance depends on the FB accuracy and the current sensor resistor accuracy.
Two LED current dimming methods are provided.
1. Floating the DIMC pin, an external PWM signal via the EN pin, providing pure PWM dimming method.
2. Connecting a capacitor larger than 100-nF to the DIMC pin, an external PWM signal via the EN pin, providing
analog dimming.
LED brightness is controlled by peak LED current and duty cycle of external PWM signal. See Figure 2, Figure 8
and Figure 9 for the PWM dimming operating and linearity. Additional external switch FETs connect/disconnect
LED string during PWM on/off period, shown in the typical application. Simultaneously, the TPS61500 samples
and holds the COMP voltage to speed up LED current regulation during the on period. As the IC and the external
switch FETs need several hundred microseconds to regulate the LED current, the frequency and minimum duty
cycle of the PWM signal are application dependent. For example, 2% is the minimum duty cycle for a 200Hz
PWM signal.
The PWM dimming method offers better control of color because current through LED is kept constant each
cycle.
When capacitor C5 is connected to the DIMC pin, the FB regulation voltage is scaled proportional to the external
PWM signal's duty cycle; therefore, it achieves LED brightness change, shown in Figure 1. The relationship
between the duty cycle and LED current is given by Equation 3:
where, duty is the duty cycle of the PWM signal.
The IC chops up the internal 200mV reference voltage at the duty cycle of the PWM signal. The pulsed reference
voltage is then filtered by a low pass filter that is composed of an internal 25-k
resistor and the external
capacitor C5. The output of the filter is connected to the error amplifier as the reference voltage for the FB pin.
Therefore, although a PWM signal is used for brightness dimming, only the LED DC current is modulated. This
eliminates the audible noise which often occurs when the LED current is pulsed during PWM dimming. Unlike
other methods for filtering the PWM signal, the TPS61500's analog dimming method is independent of the PWM
logic voltage level which often has large variations.
Copyright 2008, Texas Instruments Incorporated
11
Product Folder Link(s): TPS61500
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相关代理商/技术参数 |
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| 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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