1N4004 Просмотр технического описания (PDF) - STMicroelectronics
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1N4004 Datasheet PDF : 42 Pages
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AN1262 APPLICATION NOTE
All of the above mentioned calculation steps are summarized in table 6.
Table 6. Preliminary Calculations (step 2)
Symbol
Parameter
PinT
Transformer Input Power
VDS(on)x Max. average drop on RDS(on) in ON-state
Dx
Maximum Duty Cycle
VDSmax
Ippkx
Maximum drain Voltage in OFF-state
Max. Peak Primary Current
Definition
PinT = (---V----o---u---t---+---η--V--T--F---)----⋅---I--o---u--t
VDS(on) ≈ 1-----+--V---P--i----nV---i---mn--i---n---i⋅--n-m---R-----+-i--n--D----V--⋅S------V--R(----o----R--n------)
DX = -(--V----i-n---m-----i-n----–-----V---V-D----RS---(--o---n---)--x---)---+-----V----R--
VDSmax = VPKmax + VR + Vspike
Ippkx = V-----i-n---m----i--n---P-–---i--Vn---T-D---S----(--o---n---)--x- ⋅ -D--2--X--
8 OPERATING CONDITIONS @ VIN = VDCMIN
From the thermal point of view the heaviest operating conditions for the IC, and for most of the other parts of
the converter as well, are usually encountered at minimum input voltage.
That is why the operating conditions @ Vin = VDCmin need being evaluated. This will be done with the aid of the
relationships in table 7.
Table 7. Relationship useful for calculating converter's operating conditions @ Vin = VDCmin
Symbol
Description
Definition
D
Duty Cycle (switch ON-time to switching period ratio)
D= V--V---D-i--nC---m-m---i-n-i-n--–--–---V--V--D--D--S--S-(--(o--o-n--n-)--)x--x- ⋅ DX
Ippk
IpDC
Peak Primary Current
DC Primary Current
Ippk = Ippkx
IpDC
=
D------⋅---I--p----p---k-
2
IpRMS
Total RMS Primary Current
IpRMS = Ippk ⋅ D-3--
IpAC
RMS Primary Current (AC component only)
IpAC =
I
p
2
R
M
S
–
IpD2 C
D‘
Secondary diode conduction time to switching period ratio
D' = V----D----C----m----i--n---V-–----RV-----D---S----(--o---n---)--x- ⋅ D
Ispk
Peak Secondary Current
Ispk
=
2-----⋅---I--o---u---t
D'
IsDC
DC Secondary Current
IsDC = Iout
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