ZHCU740
I'm doing the design with tps92641, www.ti.com.cn/.../zhcu740.pdf In the document, I see an excel design tool, LED driver calculator tool, which can be provided to me.
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ZHCU740
I'm doing the design with tps92641, www.ti.com.cn/.../zhcu740.pdf In the document, I see an excel design tool, LED driver calculator tool, which can be provided to me.
Hello Zhang,
The excel tool was in development. I reviewed a revision of it and it isn't ready to be used as a design tool. Let me know what you want to design and I can direct you or help with the design.
Best Regards,
hello,
our design requirements:
Input:36-48V
Output:30-33V 3A
please help us with the TPS92641 design
thanks a lot !
Hello,
What switching frequency range are you interested in?
Are there dimming requirements?
Are there any other requirements for your design?
Best Regards,
Hello,
Here is a starting point for a design with switching frequency of 360 Khz:
Ron = 75 Kohm
Con = 470 pF
Rvout1 = 233 Kohm
Rvout2 = 20 Kohm
Rcs = 0.085 ohms (1 watt minimum rated) Uses full range of Iadj, 3A out when Iadj is 2.54V.
Inductor value 33 uH (rated for peak current plus margin)
Peak current = 3.435A
current ripple, peak to peak = 0.871 Apkpk
Vovp = 38.6V
Need to chose MOSFETs for design, RDSon 0.015 to 0.03 ohm, can be out of this range if needed, Qgatetot 40 nC or less is desirable (this is just a rough choice for this switching frequency and current).
Best Regards,
Hello,
Ron is 100K, there is no Con? My calculations are 75 Kohm and 470 pF
Rvout resistors look okay
Rcs is 0.05 ohm, and a note of 200 mV for Vcs, this is 4A of current
Upper and lower mosfets look okay
Shunt FET looks okay however you don't want C22 or C23 when shunt FET dimming.
UVLO resistors won't let this turn on until 40V. I would lower this maybe make R65 82.5 Kohm.
Do you have an RC filter on iadj pin from LED G DAC? Do you want one?
You need some ceramic capacitance for Vin (see datasheet). Also need ceramic capacitance near the upper and lower MOSFET for the power loop.
Best Regards,
hello,
In the debug, I found the Inductor would scream noise.
please help us analyse and optimize it .
Thank you!
Hello,
There can be a lot of reasons for that. Have you looked at the switching waveforms? Are you dimming when this happens? Is it working correct otherwise? What is the inductor you are using? If you have the datasheet or information about it.
"In the debug, I found the Inductor would scream noise. " is very vague. I need much more information.
Best Regards,
Hello,
You are using a lower value for Rcs then I mentioned to use. It can go above 5A if Iadj is high. Do you have a scope picture of this?
Best Regards,
Hello,
Did you add the Con that was missing on the schematic?
What is the part number of the inductor you are using? Do you have a datasheet?
Are you dimming during this picture? If so do use dim while debugging the circuit.
What voltage is Iadj at? Have you increase Rcs, R76?
Are C22 and C23 removed? If not remove them, their connection does not go to Rcs, R76 (look at Figure 13 on page 11 of the datasheet), this is outside of the regulation loop.
Do you have an updated schematic?
Best Regards,