Hello,
On page 12, 13 and 14 of AN1059 application note they do the feedback compensation for the L6561 flyback power factor corrector circuit.
****AN1059 Flyback PFC application note.
http://www.st.com/stonline/products/literature/an/5956.pdf
However, considering the equation at the bottom...
hi
Also, you wil obviously have LC type EMC filter, and maybe a CLC combo after the diode bridge....this can resonate at switch on without inrush limitation.......also the RCD snubber cap can resonate with the primary peakage inductance at switch on, and if its the wrong cap , it can be induced...
thanks zappedagain
i have built a version of this uncompensated smps led driver and it works fine.
it works so well that i think something must be wrong.
In a CCM Boost PFC stage, -they are also current controlled, but the current loop bandwidth has to be limited to 1/5th of the switching...
hi
that 100nF cap from cath-ref sounds big......that might be really taking your loop bandwidth down, giving poor transient response.....but then again it might need to be with a low CTR opto
you say it goes 3 Amps transient.....well that might be the problem., with slow loop response
also...
hello
maybe you can try powerint.com website, they have forum and will be very good with your problem.
Did your smps have output short circuit protection?
I am surprised you have 3A fuse....i suppose flyback peak currents can be high but that is a big fuse for a 15w switcher.
did you use...
VE1BLL
"I believe that many of the newer versions are running at several MHz"
I am fairly sure that none of the cheap mains CFL's run at several MHz. They may produce switching harmonics in the MHz range, but would switch at around 100KHz or so.
At several MHz, Switching losses would be too...
Cabraham I am very grateful for your reply which makes a lot of sense to me.
Its strange that some Boost converter LED driver chips have datasheets that recommend using frequency compensation, some recommend adding slope compensation, -but some make no such recommendations….
Please see (if...
VE1BLL,
I see your point, i thought they could manage any voltage ..
..maybe that app note that i posted is out of date from 2005?
But to be honest, i reckon a CFL will strike on almost any voltage above say 40V....but it will not strike cleanly, and will be slightly damaged meaning its life...
Figure 2 , page 2 of the following ...
http://pdfserv.maxim-ic.com/en/an/AN3528.pdf
gives you ccfl strike voltages versus temperature.
you can see that at 4 deg Centigrade the strike voltage is some 135V.
So in the United States at low line, (120V peak) you are not going to strike. (unless...
but triacs need there current to be above their holding current.
if you are after zero cross detector yuo can do it with especially ac coupled opto coupler (i think its HA11A1 or similar).......the transistor can then be used provide an input to a microcontroller with say a pull up resistor...
Hello,
I am writing Regarding the Boost’s RHPZ.
I was wondering if the following Continuous mode boost LED driver would have an RHPZ problem……
****** Schematic of boost LED driver:-
**** UC3842 DATASHEET….
http://www.fairchildsemi.com/ds/UC/UC3842.pdf
This converter only has a current...
Thankyou Cabraham,
You're right i will be going to use that family..the cheap UC38C42, the LT1242 as in the above (first post) schematic is very similar.
I am wondering what i am going to do about the control voltage, because my feedback pin is grounded meaning that the current sense...
Cabraham
Thankyou very much for your reference…..very good articles there
The oscillations from subharmonic oscillation will always (at lease I think so?) be of too small amplitude on the output current to bother me…
–However, these oscillations are said to possibly cause a high pitched...
hello,
I am doing a current mode buck converter using a UC3842 PWM controller and a low side mosfet.
Input voltage is 160V.
Output voltage is to be 110V.
The load is a long series string of 150mA LEDs.
The duty cycle will end up being 110/160 = 0.69.
-However, this duty cycle is greater...
Hello,
The following article states that current mode control is best, period:- (see first paragraph, left of man's picture)
http://www.powersystemsdesign.com/design_tips_june07.pdf
.....................
The following article states that sometimes current mode is best, and sometimes voltage...
macgyvers2000:-
thanks for getting back on this...
"the cheap CFLs are failing so quickly"
Do you think these "light-bulb" CFL's are failing because of the electrolytic capacitor in them being the weakest link ?
...this is the sort of ON/OFF controller circuit that could be put on an IC, for example:-
...i am wondering why this type of ON/OFF control is not done at higher powers say 200W + ?
...it works fine in the Peakswitch and they do up to ~120W
