參數(shù)資料
型號: TPA0252PWP
廠商: TEXAS INSTRUMENTS INC
元件分類: 音頻控制
英文描述: 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, PDSO24
封裝: GREEN, PLASTIC, HTSSOP-24
文件頁數(shù): 15/34頁
文件大?。?/td> 851K
代理商: TPA0252PWP
www.ti.com
Efficiency of a BTL amplifier +
P
L
P
SUP
Where:
P
L +
V
Lrms
2
R
L
, and V
LRMS +
V
P
2
, therefore, P
L +
V
P
2
2 R
L
and PSUP + VDD IDDavg
and
I
DDavg +
1
p
0
V
P
R
L
sin(t) dt
+ *
1
p
V
P
R
L
[cos(t)]
p
0 +
2V
P
p
R
L
Therefore,
P
SUP +
2 V
DD VP
p
R
L
substituting PL and PSUP into equation 7,
Efficiency of a BTL amplifier +
V
P
2
2 R
L
2 V
DD VP
p
R
L
+
p
V
P
4 V
DD
V
P +
2 P
L RL
Where:
(8)
PL = Power delivered to load
PSUP = Power drawn from power supply
VLRMS = RMS voltage on BTL load
RL = Load resistance
hBTL +
p
2 P
L RL
4 V
DD
Therefore,
VP = Peak voltage on BTL load
IDDavg = Average current drawn from the power supply
VDD = Power supply voltage
ηBTL = Efficiency of a BTL amplifier
(9)
TPA0252
SLOS288B – JUNE 2000 – REVISED SEPTEMBER 2004
Although the voltages and currents for SE and BTL are sinusoidal in the load, currents from the supply are very
different between SE and BTL configurations. In an SE application, the current waveform is a half-wave rectified
shape, whereas in BTL it is a full-wave rectified waveform. Therefore, RMS conversion factors are different. Keep
in mind that for most of the waveform both the push and pull transistors are not on at the same time, which
supports the fact that each amplifier in the BTL device only draws current from the supply for half the waveform.
Equation 8 and Equation 9 are the basis for calculating amplifier efficiency.
Table 2 employs Equation 9 to calculate efficiencies for four different output-power levels. Note that the efficiency
of the amplifier is quite low for lower power levels and rises sharply as power to the load is increased resulting in
a nearly flat internal power dissipation over the normal operating range. Note that the internal dissipation at full
output power is less than in the half-power range. Calculating the efficiency for a specific system is the key to
proper power supply design. For a stereo 1-W audio system with 8-
loads and a 5-V supply, the maximum draw
on the power supply is almost 3.25 W.
22
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