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Recent content by treez
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LEDs turning off causes EMC problem?
This circuit is an alternative to the above disclosed Sepic idea. Could readers possibly kindly confirm that this is indeed the lowest-component-count method of achieving my aims, set out in the first post ?- treez
- Post #21
- Forum: Circuit design
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LEDs turning off causes EMC problem?
ok Thanks, we are operating at 500KHz as usual for us. The spec for this converter is in the top few lines of my first post. It’s eight 300mA LEDs. They don’t all come on at once, but come on one-by-one in a line, thenm just stay on. I know nobody suggested it, but we cant do any linear...- treez
- Post #18
- Forum: Circuit design
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LEDs turning off causes EMC problem?
Hello mtripoli, Thankyou, But we cant use TLC5917, -only 120mA and Vin too low Also, Viper switching freq is too low. This way we do it is lowest componen count way possible –or so we believe. We have a pic to switch out the LED-shorting-FETs. We cannot do PWM of each LED because that...- treez
- Post #13
- Forum: Circuit design
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How to measure capacitor ripple current
well we are used to hearing how academic calculations are useless. but not in this case. U dont say topology so i assume boost. U know your duty cycle by scoping fet gate etc. u work out the boost diode trapezoid current shape. then either use integration ..or go to google and search for...- treez
- Post #4
- Forum: Circuit design
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PNP current limiter accuracy
Hello sorry if this is too many on the same topic-please delete me if you have seen enough of this I am doing a LED lamp powered by SEPIC SMPS. It is 10W and the LEDs will be end up being switched in one by one by FETs, so that the lamp comes on “chaser” style. Here is the schematic...- treez
- Thread
- Replies: 2
- Forum: Circuit design
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LEDs turning off causes EMC problem?
sorry, i forgot this diagram showing the LEDs coming on in sequence, and the way the LED current snaps down, just before the next LED is brought ON. (the FETs that switch in the LEDs, have had RC (10K, 1uF) filters put on their gates , to delay their turn-off, but it doesnt help that much as...- treez
- Post #11
- Forum: Circuit design
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LEDs turning off causes EMC problem?
Coming back to my earlier point if I may…., The LEDs of our lamp come on one by one then they all stay on. This means that as the next in the sequence is brought on, all the LEDs current suddenly go to zero (for about 1ms) , then rise back up again as the LEDs’ forward voltages builds up to a...- treez
- Post #10
- Forum: Circuit design
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LEDs turning off causes EMC problem?
Operahouse: thankyou for your interest. You are quite right, it is company policy to re-use as much of already existing circuitry as possible. Having said that, it would be difficult to do this with less parts-count than the above. This is an alternative but needs eight inductors and eight...- treez
- Post #9
- Forum: Circuit design
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LEDs turning off causes EMC problem?
thankyou all, by the way, we're going to go for this LED chaser... heres the output side... heres the input side ........ its only easy electronics so my boss wont mind me posting. any improvements or ICs for the output current limiter welcome. (we have to limit output current as it...- treez
- Post #7
- Forum: Circuit design
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8 parallel mini switchers casue bad EMC?
Macgyvers2000: Your answer is very intriguing. You are right i am a junior joe. I dont do our EMC testing, that is done by my boss alone.(and the eventual emc testing house who test to whatever we conform to which i am presuming is EN55022 or CISPR25 or whatever we all have to conform to as i...- treez
- Post #7
- Forum: Circuit design
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8 parallel mini switchers casue bad EMC?
We are trying to fit specific EMC rules of each of the various manufacturers who we build for. -they have there own EMC reuirement documents They are strict EMC standards.- treez
- Post #3
- Forum: Circuit design
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LEDs turning off causes EMC problem?
macgyvers2000 "It has been said several times before, but it's starting to become obvious... you need to bring in outside help with this one" "Sometimes it's okay to admit you don't know how to solve a problem... " I am afraid my boss has been trying to recruit a switch mode designer for 18...- treez
- Post #5
- Forum: Circuit design
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8 parallel mini switchers casue bad EMC?
hello, I am making a LED lamp using eight 300mA LEDs. (It is a re-design of my previous post's circuit) It will run off a battery with voltage 13.5V. I dont want all the LEDs to simply come on all at once, -i want them to come on in succession, LED "chaser" style. Therefore, i have...- treez
- Thread
- Replies: 6
- Forum: Circuit design
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LEDs turning off causes EMC problem?
hello, i am doing a lamp with 8 300mA LEDs powered by SMPS. Source is 13.5V The LEDs must come on one-by-one in a line then stay ON. The simple way is to put the 8 in series then switch out FETs which short out each of the LEDs. However, this means that just as the next LED is switched ON...- treez
- Thread
- Replies: 23
- Forum: Circuit design
