Embedded Systems Conference
Breaking News
Comments
Newest First | Oldest First | Threaded View
Page 1 / 2   >   >>
PCB_Tom
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
PCB_Tom   6/30/2011 12:07:04 PM
NO RATINGS
Kumar, the bulb shown here is for US market, so it's designed for 120VAC, 60HZ. The circuits shown here may not serve the 220V users as well. Tom D.

Amcfarl
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
Amcfarl   6/30/2011 11:34:46 AM
NO RATINGS
Hi Kumar, LED's rarely if ever fail open, unless handling at manufacture breaks a bond wire; in this case it would be found at test. A more usual failure (still tiny) would be S/C and would result in less than a percent drop in light,insignificant in comparison to the 10% or more caused by failure of a HB LED. This failure is more likely due to the much higher current, die temperature and thermal cycling of these in comparison to the smaller LED's running at just 10's of mW's. With enough paranoia at a pinch you could add a cheap 0.5c diode which would act as an antifuse across each LED and this will fail s/c under the HV supply to short out the open LED!

bl2010
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
bl2010   6/28/2011 6:34:02 AM
NO RATINGS
I could only partly agree with the statement of Robert; Boosting at rectified 230VAC mains means that the output voltage needs to be much higher than 325VDC. A number of LED's with a forward voltage of 350V or 400Vdc is not common. Next to this you also have the risk of the Christmas light effect. The chance of having one LED out of 100 LED's failing as an open circuit is higher that with 4-8 LED's. Single stage converter with high PFC and without large storage capacitor will result in light flicker. Based on the insights from Robert, I would prefer to use a non-isolated fly-back with medium volage LED's. Please share your thoughts. Kumar

GREATTerry
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
GREATTerry   6/27/2011 10:30:33 AM
NO RATINGS
How can the circuit (boost or buck) keep high PF? I'm not sure if this is correct to use non-isolated power supply for offline stuff. Can it really pass the 1000Vac hi-pot test?

Amcfarl
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
Amcfarl   6/24/2011 2:53:42 PM
NO RATINGS
This idea of using a boost converter and low power LED's is the subject of two Patents/applications both UK and US. Including a semi(not quasi)-resonant technique, the design achieves as high as 98% driver efficiency, 0.993 PF and due to the low cooling requirements a life of 100K hours at 45C or 400K hours at 25C including long life (12k at 105C)electrolytic caps. There is 'no'(2%PP) flicker, even when dimming. I hope to license this to interested parties. e1aam@surfree.co.uk

jmpearson
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
jmpearson   6/23/2011 2:45:39 PM
NO RATINGS
I had a friend in the 80's that tried to make money selling those incandescent stick-on diodes. I recall his sales pitch was that the diode increases the life of the light bulb - maybe he pitched power reduction as well. Both of these claims might be true - I have no idea - but in the end you have a dimmer bulb output. That fact was probably not included in my friend's sales pitch!

katgod
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
katgod   6/22/2011 9:51:42 PM
NO RATINGS
kinnar, I don't know where you got your 25 Hz number but normally the number is around 70-80 Hz. It is somewhat dependent on the decay time of the phosphor though. I am assuming we are using blue leds with yellow phosphors. Easy check to know if a Christmas string is LEDs or incandescent, If you move you head back and forth rapidly here in the USA you can see single color leds strobe, I think this is caused by LEDs being driven for half of the 60 Hz cycle, still 60 Hz though. This should be even easier to see in countries that use 50 Hz although if one were to add the expense of full wave rectification this strobing would probably not be visible.

Kinnar
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
Kinnar   6/19/2011 12:47:46 PM
NO RATINGS
25Hz switching frequency is the figure our eyes can not find the switching being done, why don't we use AC supplies for powering LEDs? this my reduce the requirements on the power supplies.

BicycleBill
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
BicycleBill   6/19/2011 11:21:54 AM
NO RATINGS
The diode in series was a bad idea then for incandescents, and it's a bad idea now for LEDs, although for very different reasons. Now, instead of starting with a 50/60 Hz sine wave with (hopefully) low distortion, the power supply is forced to begin with a half-cycle AC wave with lots of distortion--and for what possible effciency or other benefit?

stixoffire
User Rank
Author
re: Power Tip 36: Higher-voltage LEDs improve light bulb efficiency
stixoffire   6/19/2011 6:58:23 AM
NO RATINGS
Remember the days they put a rectifier in the base of the incandescent - to preserve bulb life and reduce consumption. I wonder if the approach would help with the LED arrangment as well.

Page 1 / 2   >   >>


Most Recent Comments
David Ashton
 
sw guy
 
bec0
 
sixscrews
 
betajet
 
Brian Fuller2
 
zeeglen
 
tb100
 
Stargzer
Radio
NEXT UPCOMING BROADCAST
Why Connect a Car?
May 11, 1pm EDT Monday
Overview: Battle-hardened veterans of the electronics industry have heard of the “connected car” so often that they assume it’s a done deal. But do we really know what it takes to get a car connected and what its future entails? Join EE Times editor Junko Yoshida as she moderates a panel of movers and shakers in the connected car business. Executives from Cisco, Siemens and NXP will share ideas, plans and hopes for connected cars and their future. After the first 30 minutes of the radio show, our listeners will have the opportunity to ask questions via live online chat.
Top Comments of the Week
Flash Poll
Like Us on Facebook

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
Special Video Section
LED lighting is an important feature in today’s and future ...
Active balancing of series connected battery stacks exists ...
After a four-year absence, Infineon returns to Mobile World ...
A laptop’s 65-watt adapter can be made 6 times smaller and ...
An industry network should have device and data security at ...
The LTC2975 is a four-channel PMBus Power System Manager ...
In this video, a new high speed CMOS output comparator ...
The LT8640 is a 42V, 5A synchronous step-down regulator ...
The LTC2000 high-speed DAC has low noise and excellent ...
How do you protect the load and ensure output continues to ...
General-purpose DACs have applications in instrumentation, ...
Linear Technology demonstrates its latest measurement ...
10:29
Demos from Maxim Integrated at Electronica 2014 show ...
Bosch CEO Stefan Finkbeiner shows off latest combo and ...
STMicroelectronics demoed this simple gesture control ...
Keysight shows you what signals lurk in real-time at 510MHz ...
TE Connectivity's clear-plastic, full-size model car shows ...
Why culture makes Linear Tech a winner.
Recently formed Architects of Modern Power consortium ...
Specially modified Corvette C7 Stingray responds to ex Indy ...