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G8MNY > TECH 27.06.05 21:03l 103 Lines 4691 Bytes #999 (0) @ WW
BID : 51814_GB7CIP
Read: GUEST OE7FMI
Subj: Fluorescent Lamp Circuits 2/2
Path: DB0FHN<DB0FOR<DB0SIF<DB0EA<DB0RES<ON0BEL<LA2MV<GB7CIP
Sent: 050627/1629Z @:GB7CIP.#32.GBR.EU #:51814 [Caterham] $:51814_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY
INSTANT START TYPES (Corrections Jan 05)
Advantages..
1) 3-5 times more efficient than normal tungsten lamps once warmed up.
2) No flashing starter, gentler on tubes.
3) May be able to run tubes when the heaters are burned out to give really long
useful tube lifetime & lower maintenance.
Disadvantages..
4) The light is difficult to focus with reflectors than tungsten.
5) 100Hz flicker is more pronounced than tungsten Lamps.
6) They are often more expensive than starter types.
7) They are often heavier than starter types.
Lossy (Leaky)
Fuse Transformer______________
Live _o-o_____________ ÉÍÍËÍÍ»(____________ ³
³ )º º º( -³-³-
³ )º º º( ³ ÀÄÙ ³|
Optional ³ )º º º( 500v AC ³tube ³|
PF Cap === )º º º( 80v ³ ³ÃÄ¿
³ )º º º( struck ³ ÚÄ¿ ³| ³
Neutral _____³__________)º º º(___________-³-³- ³
ÈÍÍÊÍͼ(______________³ ³
6v ³
Earth_______________________________________________³
These use either a non resonant lossy transformer with a magnetic shut that
allows the flux to bypass the secondary. (An isolating one is shown here but
auto-transformer types are common). A resonant transformer with a series
tuning capacitor, this can cut down the size of the transformer while also
correcting the PF.
When powered a high voltage (>500VAC) appears across the tube & the heaters are
energised (approx 6VAC @1A). When the tube strikes the 500V falls to about 80V
@ the current rated for that tube's power. The heater voltage also falls
dramatically.
COMMON FAULTS
a) Burnt out Transformers, due mainly to uneven tube striking (50Hz flicker)
on old tubes can causes DC through transformer & shorten transformer life
due to over heating. A sensible slow blow fuse rating or thermal cut out
would stop this!
b) The Heaters are not needed if in warm environment, so tubes can often be run
until they "drop", but fail in the cold.
ELECTRONIC BALLAST TYPE (including most Saver lamps)
Advantages..
1) Slightly brighter & more efficient lamp than normal ballasted types, as HF
excitation gives more light!
2) 4-6 times more efficient than normal tungsten lamps once warmed up
3) No Mains 100Hz flicker, the fast pulsing is merged by the tube persistence.
4) AC/DC operation.
5) Lightweight.
Disadvantages..
6) The light is difficult to focus with reflectors than tungsten lamps.
7) Radio QRM radiated down mains.
8) Direct QRM from tube acting as an aerial.
9) Cross modulation (Mixing) of nearby RF fields in the tube.
10)Interference to IR remote controls sensors from pulsing IR arcs at the
heater ends.
_______________
Fuse Surge 300V DC Ferrite³ÚÄÄÄÄÄÄÄÄÄÄÄÄÄ¿³
Live ÄÄo-oÄÄRÄÄÂÄLÄÂÄÄÄÂÄÄÄ¿ ÚÄÄÂÄÄÄÄÄÄÄÄÄÄ¿ ())))))))) _³³_
³ ³ _³_ _³_ ³ ³ - - -³- - - - -³³ ³ \/ ³
Mains ³ ³ \_/ /_\ ³ ³ _())))ÄÅÄ())))_ ³³ ³ ³
Filter === === ÃÄÄÄ)ÄÄÙ +³ ³ ()) R ()) ³ ³³ ³tube³
³ ³ ³ ÃÄÄ¿ === \³ ³ ÃÄÁÄ´ ³ ³/ ³³ ³ ³
³ ³ _³_ _³_ ³ ³ ÃÄÙ ³ _³_ÀÄ´ ³³ ³_/\_³
³ ³ /_\ \_/ ³ ³ e/³ === /_\ ³\e ³³_____³³
Neutral ÄÄÄÄÄÄÄÁÄLÄÁÄÄÄÁÄÄÄÙ ÀÄÄÁÄÄÁÄÄÄÄÄÁÄÄÄÁÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÙ
Power Inverter
The mains is protected from the large HF inverter QRM by the mains filter. The
Surge R has to handle turn on surges (>340V peak). The always live 300V DC is
roughly filtered by the electrolytic cap & the supplies the high frequency
current path needed by the inverter. Here I have shown a simple push-pull high
power inverter, some use driver control ICs & MOSFETS etc.
Push-pull positive feedback drive the 2 output hard, initially biased by a pull
up R from +300V (sometimes from the mains side to reduce R wattage), then they
self bias from the diode once oscillation starts. Frequency of oscillation is
usually 15-30KHz & changes on depending on the tube status, mains voltage etc.
The tube drive may have heater taps as shown or not, of the ferrite output
transformer secondary produces over 1000V AC before the tube strikes.
It may not be safe to run the unit without a tube!
COMMON FAULTS
i/ Not working, mains spike killed bridge/inverter, surge R blown up.
ii/ Loud singing, cause .. ferrite core chattering glue dried out.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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