參數資料
型號: TPA0222PWP
廠商: Texas Instruments, Inc.
元件分類: 音頻放大器
英文描述: STEREO 2-W AUDIO POWER AMPLIFIER WITH FOUR SELECTABLE GAIN SETTINGS AND MUX CONTROL
中文描述: 立體聲2 - W音頻功率放大器,具有四種可選增益設置和MUX控制
文件頁數: 27/33頁
文件大?。?/td> 522K
代理商: TPA0222PWP
TPA0222
STEREO 2-W AUDIO POWER AMPLIFIER
WITH FOUR SELECTABLE GAIN SETTINGS AND MUX CONTROL
SLOS285 – NOVEMBER 1999
27
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
APPLICATION INFORMATION
Efficiency of a BTL amplifier
P
L
P
SUP
(7)
Where:
(8)
P
L
V
L
rms
2
R
L
, andV
LRMS
V
P
2
, therefore, P
L
V
P
2R
L
2
P
L
= Power devilered to load
P
SUP
= Power drawn from power supply
V
LRMS
= RMS voltage on BTL load
R
L
= Load resistance
V
P
= Peak voltage on BTL load
I
DD
avg = Average current drawn from
the power supply
V
DD
= Power supply voltage
η
BTL
= Efficiency of a BTL amplifier
and
P
SUP
V
DD
I
DD
avg
and
I
DD
avg
1
0
V
P
R
L
sin(t) dt
1
V
P
R
L
[
cos(t)
]
0
2V
P
R
L
Therefore,
P
SUP
2 V
DD
V
P
R
L
substituting P
L
and P
SUP
into equation 7,
Efficiency of a BTL amplifier
V
P
2 R
L
2
2 V
DD
V
P
R
L
V
P
4 V
DD
V
P
2 P
L
R
L
BTL
2 P
L
R
L
4 V
DD
Where:
Therefore,
Table 3 employs equation 8 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.
Table 3. Efficiency Vs Output Power in 5-V 8-
BTL Systems
Output Power
(W)
Efficiency
(%)
Peak Voltage
(V)
Internal Dissipation
(W)
0.25
31.4
2.00
0.55
0.50
44.4
2.83
0.62
1.00
62.8
4.00
4.47
0.59
1.25
70.2
0.53
High peak voltages cause the THD to increase.
A final point to remember about Class-AB amplifiers (either SE or BTL) is how to manipulate the terms in the
efficiency equation to utmost advantage when possible. Note that in equation 8, V
DD
is in the denominator. This
indicates that as V
DD
goes down, efficiency goes up.
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