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PDF TDA4605 Data sheet ( Hoja de datos )
| Número de pieza | TDA4605 | |
| Descripción | Control IC for Switched-Mode Power Supplies using MOS-Transistors | |
| Fabricantes | Siemens Semiconductor | |
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Control IC for Switched-Mode Power Supplies
using MOS-Transistors
Features
q Fold-back characteristic provides overload protection for
external components
q Burst operation under short-circuit conditions
q Loop error protection
q Switch-off if line voltage is too low (undervoltage switch-off)
q Line voltage compensation of overload point
q Soft-start for quiet start-up
q Chip-over temperature protection (thermal shutdown)
q On-chip parasitic transformer oscillation suppression
circuitry
P-DIP-8-1
Type
TDA 4605
Ordering Code
Q67000-A8078
Package
P-DIP-8-1
TDA 4605
Bipolar IC
The IC TDA 4605-1 controls the MOS-power transistor and performs all necessary regulation and
monitoring functions in free running flyback converters. Since good load regulation over a wide load
range is attained, this IC is applicable tor consumer and industrial power supplies.
The serial circuit of power transistor and primary winding of the flyback transformer is connected to
the input voltage. During the switch - on period of the transistor, energy is stored in the transformer
and during the switch - off period it is fed to the load via the secondary winding. By varying switch-
on time of the power transistor, the IC controls each portion of energy transferred to the secondary
side such that the output voltage remains nearly independent ot load variations.
The required control information is taken from the input voltage during the switch-on period and from
a regulation winding during the switch-off period.
Semiconductor Group
33
06.94
1 page  
TDA 4605
Circuit Description
Application Circuit
Application circuit shows a flyback converter for video recorders with a power rating of 50 W. The
circuit is designed as a wide-range power supply tor AC-line voltages ot 90 to 270 V. The AC-input
voltage is rectified by bridge rectifier GR1 and smoothed by C1 . The NTC limits the rush in current.
In the period before the switch-on threshold is reached the IC is supplied via resistor R 1 ; during the
start-up phase it uses the energy stored in C2 , under steady-state conditions the IC receives its
supply voltage from transformer winding n1 via diode D1. The switching transistor T1 is a BUZ 90.
The parallel-connected capacitor C3 and the inductance ot primary winding 112 determine the
system resonance frequency. The R 2 - C4 - D2 circuitry limits overshoot peaks, and R 3 protects the
gate of T1 against static charges.
While T1 conducts, the current rise in the primary winding depends on the winding’s inductance
and the VC1 voltage. A voltage reproduction ot the current rise is tabbed using the R4 - C5 network
and forwarded into pin 2 ot the IC. The RC-time constant ot R 4 , R 5 must be dimensioned correctly
in order to prevent driving the transformer core into saturation.
The R 10/R 11 divider ratio provides the line voltage threshold controlling the undervoltage control
circuit in the IC. The voltage present at pin 3 also determines the overload. Detection of overload
together with the current characteristic at pin 2 controls the on period ot T1. This keeps the cut-off
point stable even with higher AC-line voltages.
Regulation of the switched-mode power supply is via pin 1. The control voltage of winding n1 during
the off-period of T1 is rectified by D3, smoothed by C6 and stepped down at an adjustable ratio by
R 5 , R 6 and R 7 . The R 6 - C7 network suppresses parasitic overshoots (transformer oscillation).
The peak voltage at pin 2, and thus the primary peak current, is adjusted by the IC so that the
voltage applied across the control winding, and hence the output voltages, are at the desired level.
When the transformer has supplied its energy to the load, the control voltage passes through zero.
The IC detects the zero crossing via series resistors R 9 connected to pin 8. But zero crossings are
also produced by transformer oscillation after T1 has turned off if output is short-circuited. Therefore
the IC ignores zero crossings occurring within a specitied period of time after T1 turn-off.
The capacitor C8 connected to pin 7 causes the power supply to be started with shorter pulses to
keep the operating ftrequency outside the audible range during start-up.
On the secondary side, tive output voltages are produced across winding n3 to n7 rectified by D4 to
D8 and smoothed by C9 to C13 . Resistors R 12 , R 14 and R 19 to R 21 are used as bleeder resistors.
Fusable resistors R 15 to R 18 protect the rectifiers against short circuits in the output circuits, which
are designed to supply only small loads.
Semiconductor Group
37
5 Page 
TDA 4605
Characteristics (cont’d)
TA = 25 ˚C
Parameter
Symbol
Limit Values
Unit
min. typ. max.
Test Condition
Test
Circuit
Overload Range and Short-Circuit Operation
Overload range lower V1U
limit
60 230
Voltage gain in VÜ 1 2
overload range
Input current in short – I1
circuit operation
90 120
Peak value in
overload range
V2Ü
3.0
Peak value in short V2K
circuit operation
2.2 2.6
290
3
180
3.0
mV
µA
V
V
2
VÜ = d
(V2S – V2B)/dV1
V1 = 0 V
2
2
V1 = V1R – 10 mV 2
V1 = 0 V
2
Generally Valid Data (V6 = 10 V)
Overload Point Correction
Overload point
correction current
– I2
400 660 850 µA
V3'= 4 V; V2'= 0 V 1
Zero Transition Detector Voltage
Positive clamp
Negative clamp
Threshold value
Input current
Delay time between
V8 and V5
Zero detector disable
time
V8P
V8N
V8S
– I8
td2
tUL
0.70 0.75 0.80 V
– 0.15 – 0.22 – 0.25 V
40 50
mV
2 4 µA
0.2 0.4 0.7 µs
2 2 6 µs
I8 = 1 mA
I8 = – 1 mA
V8 = 0
2
2
2
2
2
Semiconductor Group
43
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet TDA4605.PDF ] | |
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