Philips TDA1562Q Application Note page 5

Philips Semiconductors
Vp
I supply
I audio
T1
T2
a. Charge cycle
Fig 2. Equivalent circuits during charging and lifting
Figure 2 shows the equivalent circuits for when the lifter capacitors are being charged
(charge cycle) and for when the supply is lifted maximally.
During the charge cycle, the total supply current consists of the sum of the charge
current for the lifter capacitor (Clift) and the audio current. The charge current is
controlled by the lift/recharge control circuitry in such a manner that the power dissipation
in the charging circuitry will never exceed the maximum safe level. The maximum value
of the charge current is approximately 5A.
When the power supply is lifted, the lifter capacitors will provide the audio current, so the
power that can be delivered by the amplifier fully depends on the energy stored in the
lifter capacitors.
Since the supply voltage of the output stage can be lifted to almost twice the standard
supply voltage, the output power of this amplifier can become almost 4 times as high as
that of a standard class AB BTL amplifier which would be between 80 and 100W at a
THD of 10% with a supply voltage of 14.4V. In practice there are some additional voltage
losses in the supply line, so the actual output power at 14.4V and a THD of 10% will be
70W.
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Application note
D1
I charge
>
+
Clift
Vout
Rev. 01.02 — 05 May 2006
TDA1562Q application note
Vp
D1
I audio
I audio
T1
Vout
T2
b. Maximum supply lift
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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Clift
Vlift
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