Ovp Circuit; Load Detection For Subwoofers With Very Large Self Inductance - Philips TDA1562Q Application Note

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the just becoming active region of the FET. This reduces the total THD of the Hard
Limiter circuit by half.
As a clip starts to occur, and the FET GATE bias voltage starts to go above the Vfref
supply on it's SOURCE, the DRAIN to SOURCE resistance starts to fall and places the
same Vref bias on the negative pin of the audio op amp as that on it's positive input. This
effectively reduces the amplitude of the audio passing through the op amp limits the
clipping.
When the clipping event is over, R7 recharges C1, which determines it's recovery time.

8.3.2 OVP circuit

When the battery voltage (Vp) reaches a level of 15.1V then Q3 will conduct and
connects the status I/O pin (16) of the TDA1562 , via diode D2 to zener diode D5. This
results in a voltage of about 3.2V on the status I/O pin, which means that the TDA1562 is
forced into class AB mode , preventing the amplifier of going into class-H mode.
The OVP circuit should be connected via the ignition key switch in order to prevent the
car battery from draining during the time that zenerdiode D4 is conducting.
A second TDA1562 can be connected by using another diode (D3).

8.4 Load detection for subwoofers with very large self inductance

<12NC>
Application note
Vp (battery)
S1
Ignition key
Fig 45. OVP circuit
Rev. 01.02 — 05 May 2006
D4
11V / 0.5W
R13
Q3
2N4401
270
R15 R16 D5
100 / 1/4W 1k 2.5V / 0.5W
AN<nnnnn>
TDA1562Q application note
D2
to pin 16 of
TDA1562
(status I/O)
1N4148
D3 to pin 16 of
optional
second TDA1562
1N4148
(status I/O)
8V
R14
1k
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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