TDA8357J Datasheet, PDF (10/16 Pages) NXP Semiconductors – Full bridge vertical deflection output circuit in LVDMOS

Philips Semiconductors
Full bridge vertical deflection output circuit
in LVDMOS
Preliminary specification
TDA8357J
Supply voltage calculation
For calculating the minimum required supply voltage,
several specific application parameter values have to be
known. These parameters are the required
maximum (peak) deflection coil current I_coil(peak), the coil
parameters R_coil and L_coil, and the measuring resistance
of R_M. The required maximum (peak) deflection coil
current should also include the overscan.
The deflection coil resistance has to be multiplied with 1.2
in order to take account of hot conditions.
Chapter “Characteristics” supplies values for the voltage
losses of the vertical output stage. For the first part of the
scan the voltage loss is given by V_loss(1). For the second
part of the scan the voltage loss is given by V_loss(2).
The voltage drop across the deflection coil during scan is
determined by the coil impedance. For the first part of the
scan the inductive contribution and the ohmic contribution
to the total coil voltage drop are of opposite sign, while for
the second part of the scan the inductive part and the
ohmic part have the same sign.
For the vertical frequency the maximum frequency
occurring must be applied to the calculations.
The required power supply voltage V_P for the first part of
the scan is given by:
V_P(1) = I_coil(peak) × (R_coil + R_M)
– L_coil × 2I_coil(peak) × f_vert(max) + V_loss(1)
The required power supply voltage V_P for the second part
of the scan is given by:
V_P(2) = I_coil(peak) × (R_coil + R_M)
+ L_coil × 2I_coil(peak) × f_vert(max) + V_loss(2)
The minimum required supply voltage V_P shall be the
highest of the two values V_P(1) and V_P(2). Spread in supply
voltage and component values also has to be taken into
account.
Flyback supply voltage calculation
If the flyback time is known, the required flyback supply
voltage can be calculated by the simplified formula:
V_FB = I_{coil(p–p)} × ^R-1----c-_–--^o--e-ⁱ-^l--_–⁺--_t--_F-R-_B---_⁄-^M-_x-
where:
x = -R----_c---_o^L---_i-_lc--₊-^o--ⁱ--^l_R-----M--
The flyback supply voltage calculated this way is about
5% to 10% higher than required.
Calculation of the power dissipation of the vertical
output stage
The IC total power dissipation is given by the formula:
P_tot = P_sup − P_L
The power to be supplied is given by the formula:
P_sup = V_P × ^I--c---^o---ⁱ-^l--⁽_2-^p---^e---^a---^k--⁾ + V_P × 0.015 [A] + 0.3 [W]
In this formula 0.3 [W] represents the average value of the
losses in the flyback supply.
The average external load power dissipation in the
deflection coil and the measuring resistor is given by the
formula:
P_L = -⁽--I--^c--^o---ⁱ--^l-⁽--^p_3---^e---^a--^k---⁾--⁾--²- × (R_coil + R_M)
Example
Table 1 Application values
SYMBOL
I_coil(peak)
I_coil(p-p)
L_coil
R_coil
R_M
f_vert
t_FB
VALUE
0.725
1.45
8.82
7.9
1.5
50
640
Table 2 Calculated values
SYMBOL
V_P
R_M + R_coil (hot)
t_vert
x
V_FB
P_sup
P_L
P_tot
VALUE
11
11
0.02
0.000802
29
4.45
1.93
2.52
UNIT
A
A
mH
Ω
Ω
Hz
µs
UNIT
V
Ω
s
V
W
W
W
1999 Nov 10
10