SIMO dc-dc converter

Hello Satyajit,

I will forward your thread for the best LDOs to this team.

For the flyback, please have a look at LM5155. You will find there as well an Excel calculator for flyback.

Simulation can be done with pSpice for TI, for example.

Best regards,
Brigitte

Hi Brigitte,

Thanks for your inputs.

Thanks for suggesting part number. I couldn't find Excel sheet calculator though. Where do you find it exactly.

Also we have two options:

1. Feedback 8A output with isolation

2. Check possibility of feedback with 1.5A output without isolation

Can you suggest can we use 1.5A feedback signal from secondary to primary without isolation. 

Lastly, what isolation IC could you suggest if we use feedback from secondary to primary 

Hi Satyajit,

At 5V, 5A I would recommend our highest performance and new LDO, TPS7A57.  At 5V, 8A I would recommend 2 parallel TPS7A57 LDO's.The TPS7A57 recommended Vin max is 6V (abs max is 6.5V) but you only need 300 mV extra headroom for performance, so Vin = 5.3V and Vout = 5V.  If cost is an issue then you will want to parallel 2x TPS7A52 LDOs to meet the 5V, 5A and 3x TPS7A53 LDOs to meet the 5V, 8A.  The newer TPS7A57 performance and power density is better than the TPS7A52 and TPS7A53, however.

For 15V and 28V, 1.5A I would recommend using the LM317 for a low cost solution.  For high performance, you will want to use the TPS7A47 in a parallel configuration (probably 2x parallel TPS7A47 for each rail).

The TPS7A57 and TPS7A47 LDOs are already included in the design links below.  If you decide on the TPS7A52 or TPS7A53, please let me know and I can work to get those devices into the MS Excel calculator to make your designing much easier.

For new resources on paralleling LDOs please see the following links:

New, comprehensive design resources are available for paralleling LDOs using ballast resistors. 
Comprehensive Analysis and Universal Equations for Parallel LDO's Using Ballast Resistors
Parallel LDO Architecture Design Using Ballast Resistors

Simple calculator for complex parallel LDOs
PARALLEL-LDO-CALC

Thanks,

Stephen

Hi Stephen,

Stephen Ziel

Thanks for your suggestion. However, it seems input voltage is range is bit small for these ICs. 

I would need ICs with wide input range is input of system is varying large.

Can you suggest ICs with wide input range?

Hi Satyajit,

If your input voltage is 28V and the output is, say 5V at 8A, then you will dissipate (28-5)*8 = 184W across the linear regulator.  This is too much power dissipation for a linear regulator.  You will need a thermal resistance of less than 1 C/W to keep the linear regulator from overheating, which is probably not possible without significant thermal management such as water or liquid cooling.

I would recommend a switching converter for this design. Another option is an intermediate buss power supply, such as 28V to 5.5V, then have that 5.5V provide the input supply to the 5V outputs.  This will allow you to post regulate the 5.5V with linear regulators giving you the performance of the LDO for your final outputs.

Thanks,

Stephen

Stephen Ziel

Yes, this is a flyback converter. 28V is nominal input to flyback converter and it varies from 16 V to 48 V. Then it goes to transformer and rectifier. The rectifier output would have more variations as input is varied. That's why I requested ICs with more input range. Yes, I do prefer switching regulator due to reasons you mentioned. Can you recommend any?