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Change Output Voltage of TPS23756EVM
We have purchased a TPS23756EVM with 5V output voltage for the previous project. However, for the current project, the preferred output voltage is 11V. Would you please kindly suggest the corresponding change of the device value in this EVM? Thanks a lot in advance.
TPS23756EVM may not be a good starting point for an 11V design. TPS23756EVM was designed to support a wide input voltage range from an adapter source. TPS23754EVM-383 (12V output) may be a better starting point with the output slightly adjusted down. If TPS23754EVM-383 doesn't appear to be suitable, please specify the reason and I can look for another suitable reference design.
I have a similar question : I bought a TPS23754EVM-383 and I would like to get 24 V DC. Is it possible to adjust R25 R23 maybe R18 to get 24 V.
A design change of this magnitude would require new custom transformer (T1), secondary FET drive circuitry (for Q3/Q5), output filter (L2, C11/C12), and other various component values to re-compensate the feedback loop (including output voltage set point).
Alternatively, you could start with TPS23754EVM-420 and make these mods as a simpler path:
T2 changed to POE300F-24L
Q1 replaced by D100 (ES3C-13-F)
R3, R4 changed to 6.49k
C15, C16, C17 changed to 10uF, 50V, X5R
C19 changed to 33uF, 50V
C20 changed to 0.1uF, 50V
R30 changed to 4.75k
R25 changed to 1.78k
R27 changed to 5.11k
U4 changed to TL431A
DNP R24, C18, C28, C30
T3, C27, Q3, D17, R23 are not required but can be left on PCB
I plan to modify the 23754evm-383 circuit to 13.8V for lead asid battery charging purpose. After I modify the R25 (from 11k change to 9.1k) then I able to get the voltage 13.85V, but I found the transformer (coilcraft, JA4289-AL 2A@12V) will get hot very fast although the circuit load only 100mA. Do I need change the circuit to higher power transformer and other feedback circuit value? If yes what the parts I should modify? Thanks
I would think that increasing VOUT slightly would not cause an issue. Try installing a POT for R25 set initially to 11K to get the circuit working normally. Collect scope waveforms for normal operation including the switching waveforms at primary and secondary. Then slowly decrease the POT while monitoring the circuit waveforms to observe when an abnormal behaviour occurs. We can use the abnormal waveforms to get a better idea of what is happening.
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