参数资料
型号: LM2795EVAL
厂商: National Semiconductor
文件页数: 16/23页
文件大小: 0K
描述: BOARD EVALUATION LM2795
标准包装: 1
电流 - 输出 / 通道: 80mA
输出及类型: 4,非隔离
输出电压: 4V
特点: 充电泵
输入电压: 2.7 ~ 5.5 V
已供物品:
已用 IC / 零件: LM2795
相关产品: LM2795TLX-ND - IC LED DRVR WHT BCKLT 14USMD
LM27953TLX-ND - IC LED DRVR WHT BCKLT 18USMD
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LM27951SDX-ND - IC LED DRIVR WHITE BCKLGT 14-LLP
LM2795BLDKR-ND - IC LED DRVR WHT BCKLT 14USMD
LM27953TLDKR-ND - IC LED DRVR WHT BCKLT 18USMD
LM27952SDDKR-ND - IC LED DRIVR WHITE BCKLGT 14-LLP
LM27951SDDKR-ND - IC LED DRIVR WHITE BCKLGT 14-LLP
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LM27951SDCT-ND - IC LED DRIVR WHITE BCKLGT 14-LLP
更多...
SNVS168L – JANUARY 2002 – REVISED MAY 2013
POWER EFFICIENCY
Figure 27 shows the efficiency of the LM2794/5. The change in efficiency shown by the graph comes from the
transition from Pass Mode to a gain of 1.5.
Efficiency (E) of the LM2794/5 is defined here as the ratio of the power consumed by LEDs (P LED ) to the power
drawn from the input source (P IN ). In the equations below, I Q is the quiescent current of the LM2794/5, I LED is the
current flowing through one LED, V LED is the forward voltage at that LED current, and N is the number of LEDs
connected to the regulated current outputs. In the input power calculation, the 1.5 represents the switched
capacitor gain configuration of the LM2794/5.
P LED = N × V LED × I LED
P IN = V IN × I IN
P IN = V IN × (1.5 × N × I LED + I Q )
E = (P LED ÷ P IN )
(9)
(10)
(11)
(12)
Efficiency, as defined here, is in part dependent on LED voltage. Variation in LED voltage does not affect power
consumed by the circuit and typically does not relate to the brightness of the LED. For an advanced analysis, it is
recommended that power consumed by the circuit (V IN x I IN ) be evaluated rather than power efficiency. Figure 28
shows the power consumption of the LM2794/5 Typical Application Circuit.
Figure 27. Efficiency vs V IN
4 LEDs, V LED = 3.6V, I LED = 15mA
450
430
410
390
370
350
330
310
290
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
V IN (V)
Figure 28. P IN vs V IN
4 LEDs, 2.5 ≤ V DX ≤ 3.9V, I DX = 15mA
16
Product Folder Links: LM2794 LM2795
Copyright ? 2002–2013, Texas Instruments Incorporated
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