DC/DC Converter

URB_LD-30WR3 Series

2015.08.12-A/2

Page 4 of 8

MORNSUN Guangzhou Science & Technology Co., Ltd. reserves the copyright and right of final interpretation

Design Reference

1. Typical application

All the DC/DC converters of this series are tested according to the recommended circuit (see Fig. 2) before delivery.

If it is required to further reduce input and output ripple, properly increase the input & output of additional capacitors Cin and Cout or

select capacitors of low equivalent impedance provided that the capacitance is no larger than the max. capacitive load of the product.

Vin

GND

+Vo

0V

DC

Cin

DC

Cout

Fig. 2

Vout(VDC)

Cout(µF)

Cin(µF)

3.3/5/9

220

100

12/15/24

100

2. EMC solution-recommended circuit

Vin

GND

+Vo

0V

DC/DC

LOAD

C2

LCM

②

C0

MOV

FUSE

①

C1

Vin

GND

CY1

CY2

C3

Fig. 3

Notes: Part ① in the Fig. 3 is used for EMS test and part ② for EMI filtering;

selected based on needs.

Parameter description

Model

Vin:24V

Vin:48V

FUSE

Choose according to actual input current

MOV

S14K35

S14K60

C0

330µF/50V

330µF/100V

C, C2

4.7µF/50V

2.2µF/100V

C3

Refer to the Cout in Fig.2

LCM

1mH

CY1, CY2

1nF/2KV

EMC solution-recommended circuit PCB layout

Fig. 4

Note: the min. distance of the bonding pads between input & output isolation capacitors (CY1/CY2) shall be ≥ 2mm.

3. Application of Trim and calculation of Trim resistance

0V

Trim

+Vot

0V

Trim

+Vot

Trim up

Trim down

Applied circuits of Trim (Part in broken line is the interior of models)

Calculation formula of Trim resistance:

up:

a=

Vref

Vo’-Vref

R =

T

R -a

2

down:

a=

Vref

Vo’-Vref

R =

T

R -a

1

a is a self-defined parameter, with

no real meaning.

Vout(V)

R1(KΩ)

R2(KΩ)

R3(KΩ)

Vref(V)

3.3

4.801

2.87

12.4

1.25

5

2.883

2.87

10

2.5

9

7.500

2.87

15

2.5

12

11.000

2.87

15

2.5

15

14.494

2.87

15

2.5

24

24.872

2.87

17.8

2.5

4. It is not allowed to connect modules output in parallel to enlarge the power