MR4530 datasheet(23/43 Pages) SHINDENGEN

23 / 43 page

Shindengen Electric MFG.CO.,LTD

- 53 -

Design of DCR snubber circuit

Use the following formulas to estimate the constants for a DCR snubber circuit:

If all the energy of the leakage inductance LI is assumed to be consumed in the snubber circuit, the following

formula holds true:



2

1.2V

)









…(1)

Energy of leakage inductance LI = Energy of snubber capacitor CS

1.2







…(2)

Voltage of snubber resistor RS = Charging voltage of snubber capacitor CS

)







…(3)

Power consumption of snubber resistor RS = Power of leakage inductance LI

If we assume that LI is 2.5% of the primary inductance LP and that the charging voltage of snubber capacitor CS

is 1.2 times VNP, CS is given as follows:

From formula (1),

)

0.625





[F]

From formulas (1) and (3), we obtain formula (4).



 f

1.2V











…(4)

Formula (2) is equivalent to formula (5).

1.2





…(5)

When we substitute formula (5) into formula (4), we obtain formula (6).





…(6)

We substitute CS into formula (6) to obtain RS.

)

115.2





[

Ω]

PRS, power consumption in RS is:





[W]

These values assume that LI is 2.5% of the primary inductance LP and that the charging voltage of snubber

capacitor CS is 1.2 times the value of VNP. Adjustments must be made on an actual board.

* Calculation example

When oscillation frequency f = 25 kHz, LP = 0.5 mH,

IDP = 5 A and VNP = 200V;

CS = 0.2 uF, RS = 14.7 kΩ and PRS = 3.9 W.

Fig. 6.6 Design of DCR snubber circuit

Leakage inductance

IDP(ICP)

Peak current of main switching device

Snubber capacitor

Primary inductance of transformer

VNP

Flyback voltage generated with primary

inductance LP

Snubber resistor

Current flowing to snubber resistor

Oscillation frequency of power supply

6. Supplementary design information

MR4530 Datasheet(PDF) 23 Page - Shindengen Electric Mfg.Co.Ltd

MR4530 Datasheet(HTML) 23 Page - Shindengen Electric Mfg.Co.Ltd

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

Datasheet Download

Link URL