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Old 24th April 2006, 08:56 AM   #1
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Default DIY UcD thermal tracking circuit

Hi to all. Anyone have ideas about thermal tracking in DIY UcD?
Best regards.
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Old 24th April 2006, 06:38 PM   #2
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Hi.

With respect to what?

Nice work.
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Old 24th April 2006, 06:44 PM   #3
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After power up swithing frequency slowly decrease, then stop. After few minutes it goes up. I think is thermal unstability.
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Old 24th April 2006, 06:52 PM   #4
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What's the frequency variation like? How long before it settles?

Have you measured it again after it's been loaded down?

Have you further tried to narrow down the offensive part by say.. applying cold spray.. or hot air?

Something so simple as a better selection of input pair transitors (lower parasitics) could possibly help minimize this.. if they're to blame, even epoxying them together perhaps. Find the guilty party first though.

Might check out the components in the feedback loop as well.

Neat problem
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Old 24th April 2006, 06:56 PM   #5
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Thanks I try your recomendations.
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Old 24th April 2006, 06:59 PM   #6
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Ok. If its not thermal unstability, what this may be?
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Old 24th April 2006, 07:04 PM   #7
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Quote:
Originally posted by oldmaelstrom2
Ok. If its not thermal unstability, what this may be?

Why have you given up on the idea so soon?
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Old 25th April 2006, 05:03 PM   #8
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Hi. I try worm air upon a pcb - result: the swithing freq. is increase.
Then i glue together transistors in diferential amplifier all work fine. The freq is changing from 350 khz to 348khZ, then increasing to 352khz, so i have +/- 5 khz unbalance. Its normal or not. How is fixed in original UcD modeles from HYPEX?
Best regards.
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