ILA4605-2
1
Control IC for Switched Mode Power Supplies using MOS
Transistors
The IC ILA 4605-2 controls the MOS - power transistor and performs all necessary
regulation and monitoring function in free running flyback converters. Because of the fact
that a wide load range is achieved, this IC is applicable for consumer as well as industrial
power supplies.
The serial circuit and primary winding of the flyback transformer are connected in series to
the input voltage. During the switch - on period of the transistor, energy is stored in the
transformer. During the switch - off period the energy 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 of 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. A new cycle will start if the transformer has transferred the stored energy
completely into the load.
FEATURES:
Fold - back characteristics provides overload protection for external components
Burst operation under secondary short - circuit condition implemented
Protection against open or short of the control loop
Switch - off if line voltage is too low (undervoltage switch - off)
Line voltage depending compensation of fold - back point
Soft start for quiet start - up without noise generated by the transformer
Chip - over temperature protection (thermal shutdown)
On - chip ringing suppression circuit against parasitic oscillations of the transformer
P-DIP-8-1
In the different voltage ranges the switched - mode Power supply (SMPS) behaves as
follow:
No load operation. The Power supply is operating in the burst mode at typical 20 to 40
kHz. The output voltage can be a little bit higher or lower than the nominal value
depending on the design of the transformer and the resistors of the control voltage divider.
Nominal operation. The switching frequency is reduced with increasing load and
decreasing AC voltage. The duty factor primarily depends on the AC voltage. The output
voltage is only depends on the load.
Overload point. Maximum output Power is available at this point of the output
characteristic.
Overload. The energy transferred per operation cycle is limited at the top. Therefore the
output voltages declines by secondary overloading.
PIN DEFINITION
Pin #
Function
1.
Information Input Concerning Secondary Voltage
2.
Information Input Regarding the Primary Current
3.
Input for Primary Voltage Monitoring
4.
Ground
5.
Output
6.
Supply Voltage Input
7.
Input for Soft Start and Integrator Circuit
8.
Input for the Feedback of the Oscillator
ILA4605-2
3
CHARACTERISTICS
Ta=25
o
C; V
S
=10V
Limit Values
Parameter Symbol
min. max.
Units Test
Condition
Start - Up Hysteresis
Start-up current drain
I
6EO
1.6
mA
V
6
=V
6E
Switch-on voltage
V
6E
11
13
V
Switch-on current
I
6E1
16
mA
V
6
=V
6E
Voltage Clamp (V
6
=10V; IC is off)
At pins 2,3 (V
6
V
6E
)
V
max
5.6
9.0
V
I
2,3
=1mA
Control Range
Control input voltage
V
1R
370
430
mV
Voltage gain of the control
circuit in the control value
-V
R
150
Push-Pull Output Stage
Saturation
voltages
Pin 5 sourcing
V
sat0
2.2
V
I
5
=-0.1A
Pin5 sinking
V
satV
1.4
V
I
5
=+0.1A
Protection Circuit
Undervoltage protection for
V
6
: voltage at pin 5 = V
5min
if
V
6
< V
6min
V
6min
6
8
V
Undervoltage protection for
V
6
: voltage at pin 5 = V
5min
if
V
6
> V
6max
V
6max
16.7
V
APPLICATION DIAGRAM
R3
4.7
R1
75k
R4
330k
R11
820k
R2
27K
4W
C5
4.7
nF
C4
33nF/630V
C3
220pF
R13
47
1087EY1
(TDA4605-2)
R8
47
R9
10k
R6
1K
R7
2.5k
C7
4.7nF
R12
47k
R16
0.1
R15
0.1
D6
FU1.25
CR1
C1
150 F
385V
4x1N4007
D2
BA159
n2
T1 BUZ90
D1
C6
1
F
D3
4
2
3
5
8
1
7
6
+8.5
D4
BYW72
+17.5
D5
BYW72
n5
n4
n3
n1
+124
180...260 V
BYW76
1N4148
1N4148
R17
27
R10
5.1k
R5
220
C11
47
F
C10
470
F
C9
1000
F
C2
47
F
100V
C8
220nF-
47
F
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