Datasheet
LV5026MC
No.A2042-9/16
Sense resistor is obtained as follows.
Rs =
VREF
_
IN
Ipk_p
=
VREF
_
IN × Lp
Vac × Ton_p
=
VREF
_
IN × Lp
Vac × Don_p × T
(16)
[Inductance Ls of secondary side]
Since output current Iout is the average value of current flows to transformer of secondary side
Iout = Ipk_s ×
Ton
_
s
T
×
1
2
=
Ipk
_
s × Don
_
s
2
(Don_s =
Ton
_
s
T
= Ton_s ×
ƒ
osc) (17)
Ipk_s =
Vout
Ls
× Ton_s =
Vout
Ls
=
Don
_
s
ƒ
osc
(18)
Ls =
Vout × T × Don
_
s
2
2 × Iout
=
Vout × Don
_
s
2
2 × Iout ×
ƒ
osc
=
Vout
2
× Don
_
s
2
2 × Pout ×
ƒ
osc
(19)
Calculation of the ratio of transformer coil on primary side and secondary side
Since ratio and inductance of transformer coil is
Ns
Np
=
√Ls
√Lp
(20)
substituted equations (15), (19) for (20)
∴
Np
Ns
=
Vac
Vout
× √
η
×
Don
_
p
Don_s
(21)
Calculation of transformer coil on primary side and secondary side
N =
Vac × 10
8
2 × ΔB × Ae ×
ƒ
osc
(22)
ΔB: variation range of core flux density [Gauss]
Ae: core section area [cm
2
]
To use Al (L value at 100T),
N =
√
L
Al
× 10
2
(23)
L: inductance [μH]
Al: L value at 100T [uH/N
2
]
lg (Air gap) is obtained as follows:
lg =
μ
r
μ
0
N
2
A
e
10
2
L
(24)
μr: relative magnetic permeability, μr = 1
μ0: vacuum magnetic permeability μ0 = 4π*10
-7
N: turn count [T]
Ae: core section area [m
2
]
L: inductance [H]