EVAL3DS01G28W Datasheet, PDF (6/15 Pages) Infineon Technologies AG – 28W-LCD – Monitor SMPS Evaluation Board with ICE3DS01G

LCD Monitor SMPS Evaluation Board with ICE3DS01G
Functional Description
Introduction
The EVAL3DS01G28W demoboard is designed as a low cost LCD - Monitor power supply using the
ICE3DS01G integrated circuit controller. The circuit shown in Figure 2 details a 5V, 12V 28W supply
that operates from an line input voltage range of 85 to 265V_AC, suitable for applications requiring low
power standby function.
Line Input
The AC line input side comprises of an input fuse F1 as line input over current protection as well as
choke L1 and the X2 capacitors C7 and C22 as radio interference suppressors. After the bridge
rectifier BR1 and input capacitor C3, a voltage from 120 to 380 V_DC is present. Only a 82µF input
capacitor is required due to the wide duty cycle DC_MAX of the ICE-F3-family.
Startup
The internal current source charges up the chip supply capacitor C4 with a current of approximately
1mA.
Operation Mode
During operation, the V_CC pin is supplied via a separate transformer winding with associated
rectification D2 and buffering C4. Resistor R6 is used for current limiting during the charging of C4. In
order not to exceed the maximum voltage at V_CC pin resistor R15 causes an voltage drop of about 1V.
Additional an external zener diode D5 can be used to limit this voltage if necessary. During light or no
load condition the controller switches over to active burst mode operation order to reduce the
switching losses without audible noise.
Softstart
In order to minimize the electrical stress, a Soft-Start function is realized by an internal resistor and the
adjustable external capacitor C10.
Snubber Network
Due to the high avalanche rugged CoolMOS inside, a simple RCD snubber protection can be used.
The network R7, C8 and D3 clamp the DRAIN voltage spike caused by transformer leakage
inductance to a safe value below the drain source break down voltage V_DSBR = 650V maximum.
Limitation of primary current
The CoolMOS drain source current is sensed via external shunt resistors R10 and R11. An accurate
value of the shunt improves the peak power limitation shown in the curve peak power limitation in the
rear of this report and minimize the electrical stess on MOSFET, Transformer and output rectifier.
Output Voltage
Power is coupled out on the secondary side via a fast-acting diodes D1 and D4 with low forward
voltage. Capacitors C5, C14 and C9, C15 performs energy buffering, following LC - filters L2, C16 and
L3, C17 considerably reduces the output voltage ripple. The used storage output capacitors C5, C14
and C9, C15 are selected to have a very low ESR in order to minimize the output voltage ripple
caused by the triangular current characteristic.
Regulation
The output voltage is controlled using a type TL431 reference diode. This device incorporates the
voltage reference as well as the error amplifier and a driver stage. The output voltage is set with
resistors R1 and R2. Compensation network C1, C2, R1, R5 constitutes the external circuitry of the
error amplifier of IC2. This circuitry allows the feedback to be precisely matched to dynamically varying
load conditions, thereby providing stable control. The maximum current through the optocoupler diode
and the voltage reference is set by using resistors R3, R4. Optocoupler IC1 is used for floating
transmission of the control signal to the “Feedback” input of the ICE3DS01G control device. The
optocoupler used meets DIN VDE 884 requirements for a wider creepage distance.
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EVAL3DS01G28W
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