December 2003 1/14
®
VK05CFL
ELECTRONIC DRIVER FOR CFL APPLICATION
■ EMITTER SWITCH POWER OUT PUT STAGE
■ INTE GRATED ANTIPARALLEL COLLECTOR
SOURCE DIODE
■ INTEGRATED DIAC FUNCTION
■ NOMINAL WORKING FREQUENCY
SETTABLE BY EXTERN AL CAPACITO R
■ IGNITION FREQUENCY SET BY LOAD
DESCRIPTION
The V K05CFL is a monol ithic devi ce 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
configuration, the diac pin must be connected to
source pin. Both dia c 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.
TYPE BVICrms IPeak
VK05CFL 520 V 0.25A 1.5A
SO-8
BLOCK DIAGRAM
-
+
osc
2Vref -
+
Diac
sec
diac
Source
Collector
5Vref
R
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VK05CFL
ABSOLUTE MAXIMUM RATING
THERMAL DATA
(*) Wh en m ounted on a stan dar d single-sid ed FR-4 bo ar d with 100m m2 of Cu (at least 35µm t hick).
CONNECTION DIAGRAM
PIN FUNCTIONS
Symbol Parameter Min Typ Max Unit
VCS Collector-Source Voltage 520 V
Isec Input Current (secondary) -100 140 mA
Vsec I nput Voltage (secondary) Internall y limit ed V
ICM Collector Peak Current -1.8 1.8 A
IOSC Osc Pin Current 100 mA
VOSC Osc Pin Voltage Internally limited V
TjMax Operating Junction Temperature -40 150 °C
Tstg Storage Temperature Range -55 150 °C
Symbol Parameter Value Unit
R thj-lead Thermal Resistance Junction - lead Max 15 °C/W
R
thj-amb Thermal Resistance Junction - ambient Max 52 (*) °C/W
Pin Name Pin Function
Collector Collector of the NPN high voltage transistor in the cascode configuration.
Sour ce Low vol ta ge Power MO S F ET sourc e in th e casc od e co nfigu ratio n and GRO U N D re ference.
diac Input of t he diac block to start the system up at the beginning.
sec Connection with secondary winding of the voltage transformer, in order to trigger and to supply the
device.
osc Output via to charge external capacitor necessary to set the steady state working f requency.
SO-8
Collector
Collector
Collector
Collector
sec
Source
osc
diac
1
4
5
8
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VK05CFL
ELECTRICAL CHARACTERISTICS (Tcase=25°C unless otherwise specified)
FORWARD
REVERSE
OSC
DIAC
SEC
Symbol Parameter Test Conditions Min Typ Max Unit
VCS(sat) Collector-Source Saturation Voltage Vsec=1 0V ; IC=300mA 1.4 2.8 V
Symbol Parameter Test Conditions Min Typ Max Unit
VCSr Collector-Source Reverse Voltage IC= -300m A -1 -1.5 V
Symbol Parameter Test Conditions Min Typ Max Unit
IOSC Osc Output Current Vsec=1 0V ; V OSC=0V 240 300 360 µA
VOSC(th) Osc Turn -off Volta ge Vsec=10V 1.6 2 V
Symbol Parameter Test Conditions Min Typ Max Unit
Vdiac(thH) Diac On Threshold 28 31 35 V
Vdiac(thL) Diac Off Threshold 18 V
Symbol Parameter Test Conditions Min Typ Max Unit
Vsec(clH) Sec Clam p High Isec=20m A; VOSC=0V 22 V
Vsec(clL) Sec Clamp Low Isec= -10m A 25 V
Vsec(on) Sec Turn-on Voltage IC=10mA; VOSC=0V 3.5 4.5 5.5 V
Isec(on) Sec On Current Vsec=10V ; VOSC=0V ;
IC=300mA 4mA
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VK05CFL
APPLICATION DESCRIPTION
Technology Overview
The VK05CFL is made by using STMicroelectronics proprietary VIPower M3-3 technology. This
technology allows the integration in the same chip both of the control part and the power stage. The power
stage is the “Emitter Switching”. It is made by putting in cascode configuration a bipolar high voltage
darlington with a low voltage MOSFET. This configuration provides a good trade-off between the bipolars
low ON drop wit h high breakdo wn vo ltage in OFF stat e, and the M OSFETS hi gh swi tchin g speed. The
maximum theoretical working frequency is in the range of 300KHz.
Circuit description
The electrical scheme of the VK05CFL used as a self-oscillating converter to drive fluorescent tubes is
shown in Fig. 1.
Figure 1: Application schematic
This topology does not require the sat urable transformer to set t he working fre quency. Two secondary
windings are wound on the main ballast choke Lp. These windings have two functions:1) to trigger the ON
state and 2) to provide the power supply to the device. A good trade-off for the ratio between the primary
winding Lp and the two secondary windings is 10:1; in order to minimize the power dissipated on the
resistors R4 - R5 and to guarantee sufficient voltage to supply the device.
The steady-state working frequency is set by the two capacitor C5 and C6. They are charged by a current
Icap≈300µA. When the voltage on the capacitor reaches an internal fixed value the power stage is turned
OFF. By choosing the same value for C5 and C6 the circuit will work with a duty-cycle of 50%. During the
start-up, as the resonance frequency is higher than the steady-state frequency, the seco ndary volta ge
falls lower than the device sustain voltage before the capacitor C5-6 is charged, switching OFF the device.
For th is r eason the c ircui t can wo rk at diffe rent freque ncies dur ing the st a rt-u p and ste ady -st ate pha s es.
The re s istor R 2 an d the cap ac itor C8 are nee ded to bias the int erna l d iac in the low side devic e in orde r
to start -up the system. In the high side d evice the diac pin must be connected to the midp oint. R1 is the
pull-up resistor and C7 is the snubber capacitor.
Input filt ering i s r eali zed by R4-C10 and R5-C 1 1. I t is necess ar y to ha v e a pr oper supp l y vol ta ge o n t he
input pin.
L1s
L2s VK05CFL
Tube
Lp
C8
C7 C3
C2
C5
C6
R2
R1
C10
C11
R4
R5
VK05CFL
Bridge
+
In pu t F ilter
C4 C13
PTC
diac
sec
osc
Source
Collector
diac
sec
osc Source
Collector
1
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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 thresho ld value (~ 30V). The low side switch is turned ON and consequ ently
current will flow fr om 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
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 ign it ed the r esonan c e freq uency i s red uced ≈(Lp-C3//C2) an d 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:
(R = internal impedance)
Con si dering th e V K05C FL bo ard: R =1 2KΩ; C5=C6=1.2nF ; tstorage≈400nsec; C7= 680p F⇒t(dv)/(dt)≈800nsec;
the working frequency w ill 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
fst up–1
2πLcC4
⋅
-----------------------------
=
Ton RC 5
2
---
ln⋅⋅=
1
2
--- TT
on tstorage tdv()dt()⁄
++=
f
1
T
---
=
midpoint
Idevice
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VK05CFL
Figure 3: Start-up phase
From figure 4 it can be o bserve d that the va lue of se conda ry voltag e decreases when th e lamp c urrent
incr eases. Thi s happens bec ause inc reasing the v alue of the curren t flowin g through the tu be, increas e
the drop on it, consequently decreas ing the v oltage on the ballast inductor Lp and thereby decreasing also
the secondary voltage.
By inserting the filters (R4-C10; R5-C11) between the two secondary windings and the devices, it is
possible to guarantee a higher voltage on the input pin of t he devices for longer time compared to the
secondary signal. In this way it is possible to extend the use of the VK05CFL to all the power range eg.5W
– 23W.
Figure 4: Steady state waveforms
midpoint
diac
V
midpoint
VL2s
Vsec I
lam
p
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VK05CFL
Secondary Filter Design
The desi g n of RC ne twork app l ied on the sec pin of both de vic es has to be do ne taki ng into acc oun t the
foll owing considerations:
1) The sec filtered voltage must reach the device ON threshold at the end of the negative dV/dt and before
the end of the freewheeling diode conduction in order to avoid hard switching or switching ON delay.
2) The filtered voltage must be high enough (greater than 5V) at the end of Ton in order to guarantee the
device supply voltage.
A good choice for time constant (τ=RC) is in the range:1.5 µs ÷ 3.3 µs.
The resistor value has chosen in relation to the power dissipated on it during the start-up phase, the worst
condition is verified when the preheating is used.
Tube pr e-heating
By using the VK05CFL, the tube pre-heating can be done with the classical solution with PTC (see
application schematic in figure 1) or with a more reliable low voltage network (see figure 5b). The pre-
heating low voltage network allows to obtain an optimum pre-heating avoiding the overstress on the PTC
thus improving the ballast reliability and the lamp life-time.
Figure 5a: Pre-heating phase with PTC
APPLICATION BOARD
Please note that this demo can be used for Europe (230Vrms) market as well as for USA (110Vrms)
market.
In or der to use the demoboard for Europe market the following modification must be done: electrolytic
capacitors C1 and C12 must be replaced with only one electrolytic capacitor Cx = 3,3µF/400V connected
with the posi tive pi n on the D1 cato de and the negati ve pin on the D 3 anode . Also diffe rent po w er ran ge
CFL can be driven by using this demoboard; on the left side of the component list reported below you find
component values able to drive CFL in the power range 5W to 15W, the component values written in
brackets in the table on the right are referred to the power range 15W to 23W.
sec
VK05CFL
Low side
osc
VK05CFL
Hi gh side
+10µ
39K
1.2n
Iosc
1M
+10µ
39K
1.2n Iosc
1M
sec
osc
Ilamp
Figure 5b: Pre-heating low voltage network
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VK05CFL
Waveforms below was obtained by using the application demoboard mounted for european market:
COMPONENT LIST
5W to 15W l amp
Reference Value
T1 Lp=3,1m H, N1/N2=N1/N3=10
L0820µH
D0,D1,D2,D3 1N4007
C1, C12 22µF/200 V electrol ytic
(for Europe to replace C1, C12 with
Cx=3,3µF/400V)
C2, C3 100nF/250V
C4 2,4nF/400V
C5, C6 1.2nF/63V
C7 470pF/400V
C8 22nF/100V
C10, C11 1.5 nF /10 0V
R0 10Ω 1/2W
R1, R2 1MΩ 1/4W
R4, R5 2.2KΩ 1/4W
U1, U2 VK05CFL
>15W to 23W lamp
Reference Value
T1 Lp=2,1mH, N1/N2 =N1/N3=10
L0820µH
D0,D1,D2,D3 1N4007
C1, C1 2 22µF/200V electrolytic
(for Europe C x=6.8µF/400V)
C2, C3 100nF/250V
C4 2,4nF/400V
C5, C6 1nF/63V
C7 470pF/400V
C8 22nF/100V
C10, C11 1.5nF/100V
R0 10Ω 1/2W
R1, R2 1M Ω 1/4W
R4, R5 1KΩ 1/2W
U1, U2 VK05CFL
Device power dissipat ion Vs. power lamp
Device ∆T (Tamb=25 °C) for different power lamps
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VK05CFL
Figure 6: Board electrical scheme
VK05CFL
D0 D1
D2 D3
R0
C1
C3
C2
C4 R5
C11
C10
R4
C5
R1C7
C8
R2
C6
1234
1342
8765
87 56
L0
220V ~
2
3
C12
1
110V ~
36
8
2
1
VK05CFL
T1
U1
U2
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VK05CFL
Figure 7: Printed Circuit Board legend (Component side)
Figure 8: Printed Circuit Boar d top foil
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VK05CFL
Freewheeling diode If=f(Vf) characteristic at
Freewheeling diode If=f(Vf) characteristic at
Collector current Vs. collector-source saturation
voltage at Tamb=125ºC
V sec = 6V
Vsec = 10V
Vsec = 15V
Vsec = 6V
Vsec = 10V
V sec = 15V
Collector current Vs. collector-source saturation
voltage at Tamb=25ºC
T = 25°C T = 125°C
Tamb=25ºC Tamb=125ºC
Test circuit
Bipolar storage time Vs. collector current
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VK05CFL
DIM. mm. inch
MIN. TYP MAX. MIN. TYP. MAX.
A 1.75 0.068
a1 0.1 0.25 0.003 0.009
a2 1.65 0.064
a3 0.65 0.85 0.025 0.033
b 0.35 0.48 0.013 0.018
b1 0.19 0.25 0.007 0.010
C 0.25 0.5 0.010 0.019
c1 45 (typ.)
D 4.8 5 0.188 0.196
E5.8 6.2 0.228 0.244
e 1.27 0.050
e3 3.81 0.150
F 3.8 4 0.14 0.157
L 0.4 1.27 0.015 0.050
M 0.6 0.023
S 8 (max.)
L1 0.8 1.2 0.031 0.047
SO-8 MECHANICAL DATA
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VK05CFL
SO-8 TUBE SHIPMENT (no suffix)
All dimensions are in mm.
Base Q.ty 100
Bulk Q.ty 2000
Tube length (± 0.5) 532
A3.2
B6
C (± 0.1) 0.6
TAPE AND REEL SHIPMENT (suf fix “13TR”)
All dimensions are in mm.
Base Q. ty 2500
Bulk Q.ty 2500
A (max) 330
B (min) 1.5
C (± 0.2) 13
F20.2
G (+ 2 / -0) 12.4
N (min) 60
T (max) 18.4
TAPE DIMENSIONS
According to Electr onic Industrie s Asso ciation
(EIA) Sta ndard 481 rev. A, Feb. 1986
All dimensions are in mm.
Tape width W 12
Tap e Hole Spacing P0 (± 0. 1) 4
Component Spacing P 8
Hole Di am eter D (± 0. 1/-0) 1.5
Hole Diameter D1 (min) 1.5
Hole Position F (± 0.05) 5.5
Compartment Depth K (max) 4.5
Hole Spacing P1 (± 0.1) 2
Top
cover
tape
End
Start
No componentsNo components Components
500mm min
500mm min
Empty components pockets
saled with cover tape.
User di rection of feed
REEL DIMENSIONS
C
B
A
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VK05CFL
Information furn is hed is believed to be ac c ur ate and r eliab le. However, STMicroelectr onics ass um es no res ponsibilit y for the co nsequenc es
of use of such information nor for any infringement of patents or ot her rights of third parties which may results from its use. No license is
gran ted by implication or oth er wise unde r a ny patent or p atent rights of STMicroelectr onics. Specific ations m entioned in this publication are
subj ec t to change w ithout n otice. This p ublication supersedes and r eplaces all information p r ev iously s uppl ied. STMicroelectr on ics pr oduct s
are not au thorized for use as critical components in life support devices o r systems without express written approval of STMicroelectronics.
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