1/15

L6567

January 2000

This is preliminary information on a new product now in development. Details are subject to change without notice.

BCD-OFF LINE TECHNOLOGY

FLOATING SUPPLY VOLTAGE UP TO 570V

GND REFERRED SUPPLY VOLTAGE UP TO
18V

UNDER VOLTAGE LOCK OUT

CLAMPING ON Vs

DRIVER CURRENT CAPABILITY:
30mA SOURCE
70mA SINK

PREHEAT AND FREQUENCY SHIFT TIMING

DESCRIPTION

The device is a monolithic high voltage integrated cir-
cuit designed to drive CFL and small TL lamps with a
minimum part count.

It provides all the necessary functions for proper pre-
heat, ignition and steady state operation of the lamp:

variable frequency oscillator;

settable preheating and ignition time;

capacitive mode protection;

lamp power independent from mains voltage variation.

Besides the control functions, the IC provides the lev-
el shift and drive function for two external power MOS
FETs in a half-bridge topology.

SO14

DIP14

ORDERING NUMBERS:

L6567D

L6567

HIGH VOLTAGE DRIVER FOR CFL

BLOCK DIAGRAM

FEED FORWARD

VCO +

FREQ. SHIFTING

VOLTAGE

REFERENCE

BIAS

CURRENT

GENERATOR

comp.

PREHEATING

TIMING

LOGIC

RHV

Rhv

Vhv

Cp/Cav

LEVEL

SHIFTING

HIGH

SIDE

DRIVER

Cboot

LOW
SIDE

DRIVER

Vhv

Chv

MAINS

Rshunt

PGND

REF

Ref

D96IN441B

Lamp

SGND

MULTIPOWER BCD TECHNOLOGY

L6567

2/15

PIN FUNCTION

PIN CONNECTION (Top view)

Pin

Description

Floating Supply of high side driver

Gate of high side switch

Source of high side switch

High Voltage Spacer. (Should be not connected)

Supply Voltage for GND level control and drive

Gate of low side switch

PGND

Power Ground

First timing (TPRE TIGN), then averaging the ripple in the representation of the HVB (derived
through RHV).

SHUNT

: current monitoring input

REF

Reference resistor for current setting

SGND

Signal Ground. Internally Connected to PGND

Frequency setting capacitor

RHV

Start-up supply resistor, then supply voltage sensing.

Timing capacitor for frequency shift

N.C.

PGND

RREF

SGND

RHV

D96IN440

3/15

L6567

ABSOLUTE MAXIMUM RATINGS

NOTES: (1) Do not exceed package thermal dissipation limi ts

(2) For VS

VS high 1

(3) For VS > VS high 1
(4) Internally Limited

Note: ESD immunity for pins 1, 2 and 3 is guaranteed up to 900 V (Human Body Model)

Symbol

Parameter

Value

Unit

Low Voltage Supply

18 (1)

RHV

Mains Voltage Sensing

VS +2VBE (2)

Preheat/Averaging

Oscillator Capacitor Voltage

Frequency Shift Capacitor Voltage

RREF

Reference Resistor Voltage

Current Sense Input Voltage

-5 to 5

transient 50ns

-15

Low Side Switch Gate Output

High Side Switch Source Output: normal operation

-1 to 373

0.5sec mains transient

-1 to 550

VG1

High Side Switch Gate Output: normal operation

-1 to 391

0.5sec mains transient

-1 to 568

with respect to pin S1

to V

Floating Supply Voltage: normal operation

391

0.5sec mains transient

568

FS/S1

Floating Supply vs S1 Voltage

VFS Slew Rate (Repetitive)

-4 to 4

V/ns

VS1 Slew Rate (Repetitive)

-4 to 4

V/ns

RHV

Current Into R

3 (3)

Clamped Current into V

200 (4)

stg

Storage Temperature

-40 to 150

Junction Temperature

-40 to 150

L6567

4/15

ELECTRICAL CHARACTERISTCS
(V

= 12V; R

REF

= 30K

; C

= 100pF; T

= 25

C; unless otherwise specified.)

Symbol

Parameter

Test Conditio n

Min.

Typ.

Max.

Unit

- SUPPLY VOLTAGE SECTION

S high 1

Turn On Threshold

10.7

11.7

12.7

S high2

Clamping Voltage

VS = 20mA

S low 2

Turn Off Threshold

S HYST

Supply Voltage Hysteresis

1.5

1.65

1.8

S low 1

Voltage to Guarantee

="0"and V

= "1

SSP

Supply Current at Start Up

= 10.6V Before turn on

250

SOP

Supply Operative Current

= VShigh 1

1.2

OSCILLATOR SECTION

osc min

Minimum Oscillator frequency

RHV

= 0mA; CI = 5V

41.7

44.29

kHz

osc 600

Feed Forward Frequency

RHV

= 600mA

47.88

50.4

52.92

kHz

osc 1mA

Feed Forward Frequency

RHV

= 1mA

79.8

88.2

kHz

fosc max

Maximum Oscillator Frequency

CI = 0V

96.75

107.5

118.25

KHz

Oscillator Transconductance

17.5

A/V

PREHEAT/IGNITION SECTION

P.H.T.

Preheat Time

Cp = 150nF

0.88

1.12

sec

P.H.clocks

Number of Preheat Clocks

IGN.clocks

Number of Ignition Clocks

RATE OF FREQUENCY CHANGE SECTION

ICIP charge

CI Charging Current During
Preheat

106

118

130

ICII charge

CI Charging Current During
Ignition

1.2

1.4

ICI disch

CI Discharge Current

-52

-47

-42

TH CI

CI Low Voltage Threshold

100

RS - THRESHOLD SECTION

CMTH

Capacitive Mode Voltage
Threshold

Preheat Voltage Threshold

-0.64

-0.6

-0.56

G1 - G2 DELAY TIMES SECTION

DON

On Delay of G1 Output

1.05

1.4

1.75

5/15

L6567

(*) Before starting the first commutation; when switching 6V is guaranteed.

General operation

The L6567 uses a small amount of current from a supply resistor(s) to start the operation of the IC. Once start
up condition is achieved, the IC turns on the lower MOS transistor of the half bridge which allows the bootstrap
capacitor to charge. Once this is achieved, the oscillator begins to turn on the upper and lower MOS transistors
at high frequency, and immediately ramps down to a preheat frequency. During this stage, the IC preheats the
lamp and after a predetermined time ramps down again until it reaches the final operating frequency. The IC
monitors the current to determine if the circuit is operating in capacitive mode. If capacitive switching is detected,
the IC increases the output frequency until zero-voltage switching is resumed.

Startup and supply in normal operation

At start up the L6567 is powered via a resistor connected to the R

pin (pin 13) from the rectified mains. The

current charges the C

capacitor connected to the V

pin (pin 5). When the V

voltage reaches the threshold

S LOW1

(max 6V), the low side MOS transistor is turned on while the high side one is kept off. This condition

assures that the bootstrap capacitor is charged. When V

S HIGH1

threshold is reached the oscillator starts, and

the R

pin does not provide anymore the supply current for the IC (see fig.1).

DON

On Delay of G2 Output

1.05

1.4

1.75

Ratio between Delay Time +
Conduction Time of G1 and G2

RHV

= 1mA; Cl = 5V

Cl = 0V

0.87
0.77

1.15
1.30

LOW SIDE DRIVER SECTION

Ron G2 so

G2 Source Output Resistance

= 12V, V = 3V

190

Ron G2 si

G2 Sink Output Resistance

= 12V, V = 3V

125

Ron G1 so

G1 Source Output Resistance

= 10V, V = 3V

190

Ron G1 si

G1 Sink Output Resistance

= 10V, V = 3V

125

HIGH SIDE DRIVER SECTION

FSLK

Leakage Current of FS PIN to
GND

= 568V; G1 = L

= 568V; G1 = H

5
5

S1 LK

Leakage Current of S1 PIN to
GND

= 568V; G1 = L

= 568V; G1 = H

5
5

BOOTSTRAP SECTION

Boot Th

BOOTSTRAP Threshold

= 10.6V before turn on

5 (*)

AVERAGE RESISTOR

AVERAGE

Average Resistor

38.5

Symbol

Parameter

Test Conditio n

Min.

Typ.

Max.

Unit

DON

O N

DON

O N

-------------------------------------------

ELECTRICAL CHARACTERISTCS (Continued)

L6567

6/15

Figure 1. Start up

Oscillator

The circuit starts oscillating when the voltage supply V

has reached the V

S HIGH1

threshold. In steady state

condition the oscillator capacitor C

(at pin 12) is charged and discharged symmetrically with a current set main-

ly by the external resistor R

REF

connected to pin 10. The value of the frequency is determined by capacitor C

and resistor R

REF

. This fixed value is called F

MIN

. A dead time T

between the ON phases of the transistors

is provided for avoiding cross conduction, so the duty cycle for each is less than 50%. The dead time depends
on R

REF

value (fig. 7).

The IC oscillating frequency is between F

MIN

and F

MAX

= 2.5 · F

MIN

in all conditions.

Preheating mode

The oscillator starts switching at the maximum frequency F

MAX

. Then the frequency decreases at once to reach

the programmed preheating frequency (fig.2). The rate of decreasing (df/dt) is determined by the external ca-
pacitor C

(pin 14). The preheat time T

PRE

is adjustable with external components (R

REF

and C

). The preheat

current is adjusted by sense resistance R

SHUNT

. During the preheating time the load current is sensed with the

sense resistor R

SHUNT

(connected between pin 9-R

- and pin 7-PGND-). At pin 9 the voltage drop on R

SHUNT

is sensed at the moment the low side MOS FET is turned off. There is an internal comparator with a fixed thresh-
old V

: if V

> V

the frequency is decreased and if V

< V

the frequency is increased. If the V

thresh-

old is reached, the frequency is held constant for the programmed preheating time T

PRE

is determined by the external capacitor C

(pin8) and by the resistor R

REF

: C

is charged 16 times with a

current that depends on R

REF

, and these 16 cycles determine the T

PRE

So the preheat mode is programmable with external components as far as T

PRE

is concerned (R

REF

) and

as far as the preheating current is concerned (choosing properly R

SHUNT

and the resonant load components:

L and C

The circuit is held in the preheating mode when pin 8 (C

) is grounded.

In case F

MIN

is reached during preheat, the IC assumes an open load. Consequently the oscillation stops with

the low side MOS transistor gate on and the high side gate off. This condition is kept until V

undershoots V

S LOW1

SLOW1

SHIGH1

low side mosfet

-V

high side mosfet

TIME

7/15

L6567

Figure 2. Preheating and ignition state.

Ignition mode

At the end of the preheat phase the frequency decreses to the minimum frequency (F

MIN

), causing an increased

coil current and a high voltage appearing across the lamp. That is because the circuit works near resonance.
This high voltage normally ignites the lamp. There is no protection to avoid high ignition currents through the
MOS transistors when the lamp doesn't ignite. This only occurs in an end of lamp life situation in which the circuit
may break. Now the lowest frequency is the resonance frequency of L and C

(the capacitor across the lamp).

The ignition phase finishes when the frequency reaches F

MIN

or (at maximum) when the ignition time has

elapsed. The ignition time is related to T

PRE

: T

IGN

= (15/16) · T

PRE

. The C

capacitor is charged 15 times with

the same current used to charge it during T

PRE

The frequency shifting slope is determined by C

During the ignition time the V

monitoring function changes in the capacitive mode protection.

Steady state operation: feed forward frequency

The lamp starts operating at F

MIN

, determined by R

REF

and C

directly after the ignition phase. To prevent too

high lamp power at high mains voltages, a feed forward correction is implemented. At the end of the preheat
phase the R

pin is connected to an internal resistor to sense the High Voltage Bus. If the current in this resistor

increases and overcomes a value set by R

REF

, the current that charges the oscillator capacitor C

increases

too. The effect is an increase in frequency limiting the power in the lamp. In order to prevent feed forward of the
ripple of the V

voltage, the ripple is filtered with capacitor C

on pin 8 and an integrated resistor R

AVERAGE

Figure 3. Burn state

TIME

FREQUENCY

MAX

MIN

preheating
state

ignition
state

burning state

MIN

feed forward mode

FREQUENCY

Irhv

L6567

8/15

Capacitive mode protection

During ignition and steady state the operating frequency is higher than the resonance frequency of the load
(L,C

LAMP

and R

FILAMENT

), so the transistors are turned on during the conduction time of the body diode in

order to maintain Zero Voltage Switching.

If the operating frequency undershoots the resonance frequency ZVS doesn't occur and causes hard switching
of the MOS transistors. The L6567 detects this situation by measuring V

when the low side

MOS FET is turned

on. At pin 9 there is an internal comparator with threshold V

CM TH

(typ~20mV ): if V

< V

CM TH

capacitive mode is

assumed and the frequency is increased as long as this situation is present. The shift is determined by CI.

Steady state frequency

At any time during steady state the frequency is determined by the maximum on the following three frequencies:

STEADY STATE

= MAX {F

MIN

, f

FEED FORWARD

, f

CAPACITIVE MODE PROTECTION

IC supply

At start up the IC is supplied with a current that flows through R

and an internal diode to the V

pin which-

charges the external capacitor C

. In steady state condition R

is used as a mains voltage sensor, so it doesn't

provide anymore the supply current. The easiest way to charge the C

capacitor (and to supply the IC) is to use

a charge pump from the middle point of the half bridge.

To guarantee a minimum gate power MOS drive, the IC stops oscillating when V

is lower than V

S HIGH2

. It will

restart once the V

will become higher than V

S HIGH1

. A minimum voltage hysteresis is guaranteed. The IC re-

starts operating at f = F

MAX

,then the frequency shifts towards F

MIN

. The timing of this frequency shifting is T

IGN

(that is: C

capacitor is charged and discharged 15 times).Now the oscillator frequency is controlled as in stan-

dard burning condition (feed forward and capacitive mode control). Excess charge on C

is drained by an inter-

nal clamp that turns on at voltage V

S CL

Ground pins

Pin 7(PGND) is the ground reference of the IC with respect to the application. Pin 11( SGND) provides a local
signal ground reference for the components connected to the pins C

, C

, R

REF

and C

Relationship between external components and sistem working condition

L6567 is designed to drive CFL and TL lamps with a minimum part count topology. This feature implies that each
external component is related to one or more circuit operating state.

This table is a short summary of these relationships:

MIN

---> R

REF

& C

FEED FORWARD

---> C

& I

RHV

PRE

& T

IGN

---> C

& R

REF

PRE

---> R

SHUNT

, L, C

, LAMP

---> R

REF

df/dt ---> C

Some useful formulas can well approximate the values:

If I

RHV

is greater than:

the feed forward frequency is settled and the frequency value is fitted by the

followi ng express ion:

MI N

8 R

R E F

---------------------------------

R HV

R EF

--------------

F E ED FO R W AR D

R H V

121 C

---------------------

9/15

L6567

Other easy formulas fit rather well:

46.75 · 10

^-12

· R

REF

PRE

224 · C

· R

REF

As far as df/dt is concerned, there are no easy formulas that fit the relation between C

, R

, and C

. C

is charged

and discharged by three different currents that are derived from different mirroring ratios by the current flowing
on R

REF

. The voltage variations on C

are proportional to the current that charges C

, that is to say they are

proportional to df/dt.

The values obtained in the testing conditions (C

= 100nF) are:

during preheating and working conditions the typical frequency increase is ~ 20KHz/ms, the typical decrease is
~-10Khz/ms;

During ignition the frequency variation is ~ -200Hz/ms.

If slower variations are needed, CI has to be increased.

Due to these tight relationships, it is recommended to follow a precise procedure: first R

has to be chosen

looking at startup current needs and dissipation problems. Then the feed forward frequency range has to be
determined, and so C

is set.

Given a certain C

, R

REF

is set in order to fix F

MIN

. Now C

can be chosed to set the desired T

PRE

and T

IGN

The other external parameters (R

SHUNT

and C

) can be chosen at the end because they are just related to a

single circuit parameters.

L6567

10/15

Figure 4. IC Operation

START

SLOW1

RESTART WITH
F=F

MAX

FREQUENCY SHIFTS IN T=T

IGN

TOWARDS BURNING STATE CONDITION
(F=MAX{F

MAX

FEEDFORWARD

CAPACITIVEMODE

})

NO OSCILLATION
LOW SIDE MOS ON
HIGH SIDE MOS OFF

SHIGH1

START OSCILLATION
F=F

MAX

T=T

PRE

F>F

MIN

DECR EASE
FR EQUENCY

OPEN LOAD DETECT ION: STOP
LOW SIDE MOS ON
AND HIGH SIDE MOS OFF

INCREA SE
FR EQUENCY

SHIGH2

T>T

PRE

IGN

F>F

MIN

DECREA SE
FREQUE NCY

INCREASE
FREQUE NCY

FEED FORWARD MODE
ACTIVATED

SHIGH2

CMTH

F>F

FEEDFORWARD

F>F

MIN

DECREA SE
FREQUE NCY

INCR EASE
FR EQUENCY

STOP OSCILLATION
LOW SIDE MOS ON
HIGH SIDE MOS OFF

SHIGH1

PREHEATING MODE

IGNITION MODE

BURNING MODE

11/15

L6567

Figure 5. Working frequency vs I

RHV

@ R

REF

= 30Kohm

Figure 6. Frequency vs C

@ R

REF

=30Kohm

Figure 7. T

vs R

REF

@ C

= 100pF

Figure 8. Frequency vs I

RHV

@ C

= 82pF

Figure 9. Frequency vs I

RHV

@ C

=100pF

Figure 10. Frequency vs I

RHV

@ C

=120pF

0.2 0

0.4 0

0 .6 0

0 .8 0

1 .00

1 .20

I rh v [ m A ]

1 0 .0 0

2 0 .0 0

3 0 .0 0

5 0 .0 0

6 0 .0 0

7 0 .0 0

9 0 .0 0

10 0 .0 0

11 0 .0 0

13 0 .0 0

14 0 .0 0

15 0 .0 0

0 .0 0

4 0 .0 0

8 0 .0 0

1 2 0 .0 0

1 6 0 .0 0

[kH

]

C f= 47pF

R re f= 30Ko hm

Cf= 56p F

Cf= 6 8p F

C f= 82pF

Cf= 100 pF

Cf= 120 pF

Cf=15 0pF

Cf=1 80 pF

Cf=22 0pF

60 .0 0

1 00 .0 0

14 0 .0 0

1 80 .0 0

2 20 .0 0

40 .0 0

80 .0 0

1 2 0.00

16 0.0 0

20 0.0 0

2 4 0.00

C f [ p F ]

1 0 . 0 0

2 0 . 0 0

3 0 . 0 0

5 0 . 0 0

6 0 . 0 0

7 0 . 0 0

9 0 . 0 0

1 0 0 . 0 0

1 1 0 . 0 0

1 3 0 . 0 0

1 4 0 . 0 0

1 5 0 . 0 0

0 .0 0

40 .0 0

80 .0 0

1 20 .0 0

1 60 .0 0

f
r
e

quenc

[
k

]

I = 0 . 5 m A

I= 0 .7 5 m A )

I = 1 m A

R ref= 30K ohm

20 .00

30 .00

4 0.0 0

50.00

6 0.0 0

R re f [ K o h m ]

0.80

1.20

1.60

2.00

2.40

[
u

]

Td t [m e as u re d d a ta]

T d t [ca lc u late d da ta]

0.20

0.40

0 .60

0.80

1.00

1.20

I rh v [m A ]

40.00

60.00

80.00

100.00

120.00

f
r
eq

[
k

]

R r ef= 20 K

R r ef= 22 K

R re f= 24K

R re f=2 7K

R re f= 30 K

R re f= 33K

Rr ef= 36 K

R re f= 39 K , 4 3 K, 4 7K , 5 1K

0 .2 0

0 .4 0

0 .6 0

0 .8 0

1 .0 0

1 .2 0

Ir h v [m A ]

2 0.0 0

4 0.0 0

6 0.0 0

8 0.0 0

10 0.0 0

f
r
equ

enc

[
k

]

R re f= 2 0 K

R r ef = 2 2 K

Rr ef = 2 4 K

R re f = 2 7 K

R re f = 3 0 K

R re f = 3 3 K

R re f = 3 6 K

R re f = 3 9K ,4 3 K

0 .20

0 .40

0.60

0.80

1.00

1.20

Ir h v [ m A ]

20 .0 0

40 .0 0

60 .0 0

80 .0 0

f
r
e

quenc

[
k

]

R r ef = 20 K

R re f = 2 2 K

R r e f = 24 K

R re f = 2 7 K

R re f= 3 0 K

R r e f = 33 K

R re f = 3 6 K

R re f = 3 9 K

R r e f= 43 K , 4 7 K , 5 1 K

L6567

12/15

Figure 11. Frequency vs I

RHV

@ C

= 150pF

Figure 12.

MIN

: measurements and calculations

Figure 13. F

FEED FORWARD

: measurements and

calculations

0.20

0.40

0.60

0.80

1.00

1.20

I r h v [m A ]

20.00

40.00

60.00

80.00

f
r
equ

[
k

]

R ref= 20 K

R ref= 22 K

Rr ef= 24 K

R re f= 27K

R re f= 30K

R r ef= 33K

Rr ef= 36 K
R r ef= 39K

Rr ef=4 3 K, 47K , 51 K

20 .0 0

30 .0 0

4 0 .0 0

50 .0 0

R re f [ K o hm ]

0 .0 0

20 .0 0

40 .0 0

60 .0 0

80 .0 0

1 00 .0 0

i
n

[
K

]

C f= 82pF

C f=100p F

C f=120pF

C f=15 0pF

m eas ura m ents

F m in= 1/(8 *C f*R ref)

0. 4 0

0 .6 0

0 .8 0

1 . 00

1 .2 0

Irh v [ m A ]

0 . 0 0

1 0 0 0 0 . 0 0

2 0 0 0 0 . 0 0

3 0 0 0 0 . 0 0

4 0 0 0 0 . 0 0

5 0 0 0 0 . 0 0

6 0 0 0 0 . 0 0

7 0 0 0 0 . 0 0

8 0 0 0 0 . 0 0

9 0 0 0 0 . 0 0

1 0 0 0 0 0 . 0 0

1 1 0 0 0 0 . 0 0

1 2 0 0 0 0 . 0 0

r
eq

f
e

f
or

r
d

[
H

]

m eas u re m en ts

c a lc u latio ns ( 1/12 1 )*Ir hv /C f

Cf= 8 2pF

Cf= 1 00p F

C f= 12 0 pF

Cf= 1 50p F

Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences
of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. N o license is granted
by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject
to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.

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15/15

L6567

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