TEA2019 Просмотр технического описания (PDF) - STMicroelectronics
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TEA2019 Datasheet PDF : 7 Pages
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TEA2019
TYPICAL CIRCUIT
V6
V5
V3
10nF
AS1
8.2kΩ
22nF
10nF
7
6
10kΩ
8
9
22nF
470Ω
10Ω
4.7µF
5
4
3
2
1
TEA2019
10
11
12
13
14
RAMP
GENERATOR
IC
0V
-1V
22nF
3.9kΩ
56kΩ
3.3nF
59kΩ
1%
1.5nF
100Ω
47nF
4.7µF
V10
V12
V14
GENERAL DESCRIPTION
(see application note AN406/0591)
Operating Principles (Figure 1)
On every period, the beginning of the conduction
time of the transistor is triggered by the fall of the
oscillator saw-tooth which acts as clock signal. The
period Tosc is given by :
Tosc ≈ 0.69 Ct (Rt + 2000)
(Tosc in seconds, Ct in Farad, Rt in Ω)
The end of the conduction time is determined by a
signal issued from comparing the following signals.
a) the sawtooth waveform representing the
collector current of the switching transistor,
sampled across the emitter shunt resistor.
b) the output of the error amplifier.
Base Drive
• Fast turn-on
On each period, a current pulse ensures fast
transistor switch-on.
This pulse performs also the ton(min) function at
the beginning of the conduction.
• Proportional base drive
In order to save power, the positive base current
after the starting pulse becomes an image of the
collector current.
The
ratio
IC
IB
is
programmed
as
follows
(Figure
2).
IC
IB
=
RB
RE
4/7
Figure 1 : Current Mode Control
Vi
VREF
OSCILLATOR
ERROR
AMPLIFIER
FLIP-FLOP
S
Q
ERROR
SIGNAL
R
COMPARATOR
Re
I C SENSE
OUTPUT
FILTER
IC
OSCILLATOR
SAWTOOTH
IC (sample)
FLIP-FLOP
OUTPUT
t
Error
Signal
t
t
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