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PDF VK05 Data sheet ( Hoja de datos )
| Número de pieza | VK05 | |
| Descripción | ELECTRONIC DRIVER FOR CFL APPLICATION | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de VK05 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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® VK05CFL
ELECTRONIC DRIVER FOR CFL APPLICATION
TYPE
VK05CFL
BV
520 V
ICrms
0.25A
IPeak
1.5A
s EMITTER SWITCH POWER OUTPUT STAGE
s INTEGRATED ANTIPARALLEL COLLECTOR
SOURCE DIODE
s INTEGRATED DIAC FUNCTION
s NOMINAL WORKING FREQUENCY
SETTABLE BY EXTERNAL CAPACITOR
s IGNITION FREQUENCY SET BY LOAD
DESCRIPTION
The VK05CFL is a monolithic device housed in a
standard SO-8 package, made by using
STMicroelectronics proprietary VIPower M3
Technology. This device is intended both for the
low side and the high side driver in half bridge CFL
applications. This means that it is possible to
realize a complete H-bridge by using two
VK05CFL devices: one connected in HSD
configuration and the other connected in LSD
configuration. In the VK05CFL used in HSD
BLOCK DIAGRAM
SO-8
configuration, the diac pin must be connected to
source pin. Both diac functionality and discharge
circuit for external diac capacitor are integrated.
By an external capacitor it is possible to choose
the nominal working frequency without influence
on the ignition one.
Collector
diac
Diac
sec
-osc
+
R 2Vref
+
-
5Vref
September 2002
Source
1/14
1 page  
VK05CFL
Functional description
When the circuit is supplied, the capacitor C8 is charged by the resistor R2 till the voltage across it
reaches the internal diac threshold value (~ 30V). The low side switch is turned ON and consequently
current will flow from the HV rail to ground through the path formed by C3//C2, C4 and Lp (in case that the
pre-heating network is not present: PTC and C13 are not connected). The voltage drop on Lp is
“transferred” to the two secondary windings (wound in opposition) in order to confirm the ON state for the
low side device and the OFF state for the high side device. As soon as the low side device switches ON,
the capacitor C8 is discharged to ground by an internal HV diode to avoid diac restart.
In this preliminary phase the tube is OFF and the circuit will oscillate at the Lp-C4 series with (C3//C2)
resonance frequency
fst – up
=
--------------1---------------
2π Lc ⋅ C4
we can neglect C3//C2
As this frequency is higher than the steady-state one, the two devices will switch ON-OFF at this
frequency, as the voltage on the two secondary windings falls below the voltage needed to keep the
device on.
As soon as the tube is ignited the resonance frequency is reduced ≈(Lp-C3//C2) and the circuit will work
at the steady-state frequency fixed by the two capacitors C5 and C6.
It is possible to calculate the steady-state frequency by these formulae:
Ton
=
R
⋅
C
⋅
ln
5--
2
(R = internal impedance)
1-- T
2
=
Ton + tstorage + t(dv) ⁄ (dt)
f = -1--
T
Considering the VK05CFL board: R=12KΩ; C5=C6=1.2nF; tstorage≈400nsec; C7=680pF⇒t(dv)/(dt)≈800nsec;
the working frequency will be: f≈35KHz.
In figure 2 and figure 3, the start-up phase without preheating is reported, while in figure 4 the main
waveforms in steady-state are shown.
Figure 2: Start-up phase
Idevice
midpoint
5/14
5 Page 
VK05CFL
Collector current Vs. collector-source saturation
voltage at Tamb=25ºC
Collector current Vs. collector-source saturation
voltage at Tamb=125ºC
Vsec =15V
Vsec =10V
Vsec= 6V
Vsec =15V
Vsec =10V
Vsec =6V
Freewheeling diode If=f(Vf) characteristic at
Tamb=25ºC
T = 25°C
Freewheeling diode If=f(Vf) characteristic at
Tamb=125ºC
T = 125°C
Bipolar storage time Vs. collector current
Test circuit
11/14
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet VK05.PDF ] | |
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