TPA0152_16 Datasheet, PDF (23/36 Pages) Texas Instruments – 2.8-W STEREO AUDIO POWER AMPLIFIER WITH DIGITAL VOLUME CONTROL

TPA0152
www.ti.com
SLOS246F – JUNE 1999 – REVISED SEPTEMBER 2004
Efficiency of a BTL amplifier +
P_L
P_SUP
Where:
P_L
+
V
L^rms2
R_L
,
and V_LRMS
+
V_P
Ǹ₂
,
therefore,
P_L
+
V_P2
2 R_L
and ^P_SUP ^{+ V}_DD ^I_DD^avg
and
ŕ I_DDavg
+
1
p
p
0
V_P
R_L
sin(t) dt
+
*
1
p
Therefore,
P_SUP
+
2 V_DD V_P
p R_L
substituting P_L and P_SUP into equation 7,
V_P²
Efficiency of a BTL amplifier
+ ^{2 RL}
2 V_DD V_P
+
p V_P
4 V_DD
Where:
p R_L
V_P
R_L
p
[cos(t)] ₀ +
2V_P
p R_L
V_P + Ǹ2 P_L R_L
(8)
Therefore,
h_BTL
+
p
Ǹ2 P_L R_L
4 V_DD
P_L = Power delivered 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_DDavg = Average current drawn from the power supply
V_DD = Power supply voltage
η_BTL = Efficiency of a BTL amplifier
(9)
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-Ω loads and a 5-V supply, the maximum draw
on the power supply is almost 3.25 W.
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