EV020-5-S-00A – UNIVERSAL INPUT, 5W CELL PHONE CHARGER

EV020-5-S-00A Rev.1.02

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5

11/28/2013

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CIRCUIT DESCRIPTION

The EV020-5-S-00A is configured in a single-

stage Flyback topology, it uses primary-side-

control which can mostly simplify the schematic

and get a cost effective BOM. It can also achieve

accurate constant voltage and constant current.

FR1 and CR1 compose the input stage. FR1 is

used to protect for the component failure or some

excessive short events, also it can restrain the

inrush current.

C1, L1 and C2 compose π filter to guarantee the

conducted EMI meet standard EN55022. R2, R3,

D1 and C3 compose the snubber circuit to

reduce drain-source voltage spike.

R4, C5, C6 and D2 are used as Vcc power

supply.

R5 and R6 are resistor divider for detecting

output voltage by sampling voltage on primary

auxiliary winding.

CY1 is Y capacitor lowering common mode noise

to make sure there is enough EMI margin. T1 is

power transformer, the structure of which is also

very important to pass EMI test.

D3, C8, C9, C10, L2 and R8 compose output

circuit. D3 is schottky diode for better efficiency.

C10 is ceramic capacitor for lower output voltage

ripple and R8 is dummy load, which is used for

good regulation. C8, L2 and C9 compose π filter

to restrain the output ripple.

R7 and C7 are used to depress the spike of

schottky.