Datasheet

LV5026MC
No.A2042-8/16
(for Isolation circuit)
Using the circuit diagram below, the wave form of the current that flows to Np and Ns is as follows.
Current waveform flows to primary side and secondary.
[Inductance Lp of primary side and sense resistor Rs]
If a peak current flow to transformer is represented as Ipk_p, the power (Pin) charged to the transformer on primary side
can be represented as:
Pin =
1
2
× Lp × (Ipk_p)
2
× ƒ osc (11)
Ipk_p =
Vac
Lp
× Ton_p (12)
Lp =
Vac
2
× Ton
_
p
2
× ƒ osc
2 × Pin
=
Vac
2
× Don
_
p
2
2 × Pin× ƒ osc
(13)
(Don_p =
Ton
_
p
T
= Ton_p × ƒ osc),
To substitute the following to the formula below,
.
.
.
η =
Pout
Pin
(14)
∴Lp =
Vac
2
× Ton
_
p
2
× ƒ osc × η
2 × Pout
=
Vac
2
× Don
2
× η
2 × Pout × ƒ osc
(15)
RESET
REF_IN
CLK
Q
CS
VREF
(0.605V typ)
+
-
-
OUT
Vac
LP
(Np)
Ls
(Ns)
Rcs
R1
a blockdiagram in outline
R2
Vzd
Ip
Vac
T
T
Ipk_p = Vac/Lp × Ton_p
Ipk_s = Vf/Ls × Ton_s
Iout
(Ton_s)
ON
OFF
FET
REF_IN
VREF (0.605V)typ
(Primary side current)
Primary
side
Secondary
side
Is
Ipk_p
Ipk_s
(Secondary side current)
Ip (primary side)
Is (Secondary side current)
Ip slope is proportion to
Vac voltage (REF pin voltage)
T(1cycle)
FET_OFF FET_ON
(Ton_p)
Is = Vf/Ls × Ton_s
Ip = Vac/Lp × Ton_p