PMP7327

Hello Danilo,

The circuit using the BQ24640 could be kept the same size if you want to utilize the same voltage range and charging current for the capacitor bank.

However if you are wanting to increased the power you can pull into your load you should consider a larger buck boost converter.

Are you planning on the same voltages?

Hi,

Yes, I want to increase the charging power. But the idea is to keep the same voltage and increase the charging current. So I wonder if I could just repeat this circuit on parallel to reach the current I need.  

Hello Danilo,

OK.

Could you list out your desired parameters and we can see what sort of adjustments would be needed to this sort of design. The below parameters will give us a start. Some of them will seem redundant from what you already have posted but it will be convenient to have it all in one spot.

Input Voltage Range:

Capacitor Bank Size (Farads & Voltage):

Desired Charging Current:

Max and Min Capacitor Voltages (Determine Energy Storage):

Output Voltage to System:

Output Current to System:

Length of discharge:

Ryan, please see the answers below:

Input Voltage Range: 24VDC (or 30VDC as an option)

Capacitor Bank Size (Farads & Voltage): 1750F

Desired Charging Current: 10A

Max and Min Capacitor Voltages (Determine Energy Storage): 20 to 30 VDC

Output Voltage to System: 24V

Output Current to System: 40A

Length of discharge: I don´t know. I think it could be 100%. Supercaps doesn´t wear with long discharges, right?

Thanks for the suport.

Hello Danilo,

Input Case:

-Using 24 volts will work fine with the BQ24640 but you will need a a intermediate rail if 30 volt input is used.

-The charge current of 10A should be acheivable if the the right FETs and power components are selected. Have you looked through the datasheet to determine what sort of inductor and filter capacitor you will need for this current?

Capacitors:

-The BQ24640 is a buck charger meaning that the capacitor voltage is limited to some value below the input voltage. This means that you will need to adjust the expectations you have for the capacitor voltages.

The question regarding the length of the discharge was to understand how long the system would need to output 24V @ 40A to determine if it was possible.

From the looks of your design the topology of PMP7327 could work but the changes that you will need to make to handle the specifics of your application will leave with a nearly a completely new circuit outside of the BQ24640.

I would recommend looking into the WEBENCH tool available on the website to help design the second stage buck-boost power converter to take the energy from the capacitors and regulate it to the 24V @ 40A.