Test Procedure for the

(1)

Test Procedure for the

NCP1250 40-W Demonstrator

(2)

Board Electrical Schematic

Ac input voltage

Dc output voltage

NCP1250 Vbulk

. .

.

C12 82uF

C11 470n 2 x 10mH Wurth 744822120

+ -

IN

IC4 KBU4K

L1

X2

85-265 V rms

R7 330k

R2 220k

C8 1nF

R5 1.8k

R22 470k

C2 10n

R21 22

R11 47k

R13 47k

D4 1N4937

D5

NTST30100SG

C5a 680uF

C5b 680uF

R19 1k C5 10nF

D7 1N4937

C4 100pF

R8 1k

R12 18k

R9 10k C6

10nF

12 V / 3.3 A

L2 2.2uH

C7 220uF

C13 2.2nF Type = Y1 D3

1N4937 C17 100uF

D6

C3 4.7uF C15

220p

R23 1k

R6c 1.3 R6b 1.3 R6a 1.3 R16

22 1N4148

T1

Np Ns

Naux

IC2 TL431 D10

1N4148

Q1 2N2907

R18 22k D1

1N964 R14 NTC

C10 22pF

1 kV R24

220 C9

330pF R3

330k

R10 20k 1

2 3

6

4 5

F1 2AT

R25 47 R26 47

C18 22pF

400 V

250 V

11

2 8-7

5-6

1 12

3 10 Bridge R15

510k

R27 510k

R17 510k R20 510k

option

(3)

Board Picture

Input voltage from 85 V rms to 265 V rms. Nominal range 100-240 V rms

Output voltage is 12 V,

nominal current is 3.3 A

Live parts, lethal voltages Isolated output

(4)

Needed Equipment

The needed equipments are the following:

 an ac source, delivering 80 V ac to 265 V ac, needed power is below 100 W. An electronic source or a simple variac can do.

 an input ac watt-meter, up to 100 W

 a dc load absorbing up to 100 W, V

_in,max

< 20 V, I

_out,max

< 5 A

 either the above load can display dc V and dc A or separated V and A-meters are necessary

 If the load does not use local Kelvin sensors, then the output

voltage must be measured at the board level, not at the cable

ends.

(5)

Board Test Fixture

Electronic load

Ac-source

85 V to 265 V

Test n°1:

-Apply 90 V rms -No output current -Read output voltage:

 11.5 < V_out < 12.5 -Apply 230 V rms -Repeat the above

-Let the board warm up for 10 mn -Read input power

 70 mW < P < 100 mW

W-meter

P

_in

(6)

Board Test Fixture

Electronic load

Ac-source

85 V to 265 V

Test n°2:

-Apply 90 V rms -Load with 3.3 A

-Read output voltage and Pin:

 11.5 < V_out < 12.5

 38 W < P_in < 47 W -Apply 265 V rms -Load with 3.3A -Repeat the above

W-meter P

_in

Nominal Power

(7)

Board Test Fixture

Electronic load

Ac-source

85 V to 265 V

Test n°3:

-Apply 90 V rms

-Increase I_out while reading output voltage -At a certain point, I_out,max, V_out collapses, the converter hiccups (typical is 4.2 A)

 3.6 A < I_out,max < 5 A -Apply 265 V rms

-Repeat the above steps

-The I_out,max points slightly increases

W-meter

P

_in

(8)

Board Test Fixture

Electronic load

Ac-source

85 V to 265 V

Test n°4:

-Apply 90 V rms

-Apply a short-circuit at the output, usually via the dc load

-V_out must collapse, the converter tries to re-start (hiccup mode). Read the input power (watt-meter in average mode)

 5 W < P_in < 15 W -Apply 265 V rms

-Repeat the above steps

W-meter P

_in

Short-Circuit