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BD93942F Datasheet, PDF (17/30 Pages) Rohm – White LED Driver for large LCD Panels (DCDC Converter type) | |||
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BD93942F
Datasheet
ãSetting Exampleã
Output voltage=VOUT[V]=56V
LED total current=IOUT[A]=100mAÃ4ch=0.40A
DCDC input voltage=VIN[V]=14V
DCDC efficiency=η[%]=90%
Total required average input current IIN:
I
IN
[
A]
ï½
VOUT [V ]ï´ IOUT [ A]
VIN [V ]ï´ï¨[%]
ãï½
56[V ]ï´ 0.40[A]
14[V ]ï´90[%]
ï½
1.78
[ A]
When, DCDC switching frequency =fsw[Hz]=200kHz
Inductor L[H]=33uH,
Inductor ripple current ÎIL[A]:
ÎIL
ï½
(VOUT [V ] ï VIN [V ]) ï´ VIN [V ]
L[H ] ï´ VOUT [V ] ï´ f SW [Hz ]
ãï½
(56[V ] ï 14[V ]) ï´14[V ]
33 ï´10 ï6 [H ] ï´ 56[V ] ï´ 200 ï´10 3[Hz ]
ï½
1.59
[ A]
Thus, IL peak current Ipeak becomes
Ipeak
ï½
I IN [ A] ï«
ïIL[ A] [ãA] ï½ 1.78[ A] ï« 1.59[ A]
2
2
ï½
2.58
RCS resistor value when set at 0.1ohm
â¦Peak current calculation result
[ A]
VCS peak ï½ Rcs ï´ Ipeak ï½ 0.10[ï ] ï´ 2.58[ A] ï½ 0.258
and satisfy the condition.
In additionãOCP detection current IOCP at this time is
[V ] ï¼ 0.45V â¦RCS resistor consideration
I OCP
ï½
0.45[V ]
0.1[ï]
ï½
4.5
[ A]
If parts used (FET,INDUCTORãDIODE etc)âs current capacity<5A,
I peak ï¼ I OCP ï¼ Rated current of components
ï½ 2.58[ A] ï¼ 4.5[ A] ï¼ 5[ A]
Thus, there is no problem of parts selection as the above condition is satisfied.
In additionãIL ripple current minimum limit Imin is
â¦DCDC current capacity consideration
Im in
ï½
I IN
[ A]
ï
ïIL[ A] [ A]
2
ï½
1.78[ A]
ï
0.795[ A]
ï½
0.985[ A]
ï¾
0ã
Thusãwill not become discontinuous modeã
To select DC/DC components, give consideration to IC variations as well as individual component variations, and
then conduct thorough verification on practical systems.
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TSZ22111ã»15ã»001
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TSZ02201-0F5F0C100050-1-2
12.Aug.2015 Rev.002
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