PLC810PG based battery charger

Posted by: cenk on 07/15/2010

Hello,

i'm designing a 280W battery charger by using PIXIs designer. i've datasheets and reference design manuals about Hiper PLC family.

my question is about controlling output voltage. to make output current constant, i have to decrease output voltage. in the "PLC810PG based 414W PSU for Lead Battery Charger" reference design it is made by an opamp comparator circuit.
the question is what is the permitted margin of the output voltage of a 28V charger. can i decrease the output voltage to 20V levels by increasing optocupler current.

thanks for your answer.

Comments

First you need a CV-CC (constant voltage - constant current) feedback error amp design on the secondary.
It has been discussed here:
http://www.powerint.com/forum/power-supply-design/how-design-current-limited-constant-potential-battery-charger-using-topswi

Second, you will need to design the LLC resonant tank (powertrain) so that it can operate at output voltage down as low as 20V. Enter 20V / 10A as your output voltage into the HiperPLC PIXls spreadsheet. Iterate your design so that operating frequency is 100 kHz and resonant frequency is around 85-90 kHz. The value of Q should be 1.5~2. (Reduce leakage inductance to increase Q). Kratio (Lp/Ls) should be low, <4, so as to reduce the frequency variation required to regulate between 20 and 28V. Fix the values of Lp, Ls, C, and transformer turns. Then change the output specification to 28V. Examine the results to see if they are acceptable (Vmin). You may need to repeat the 20V step with a new value of Q. If Vmin in step 2 is too high, you need to raise Q.

Hello again,

Firstly thanks a lot for your guidance about designing PLC810PG. i'll use your comments designing the circuit. they are very useful for me.

Now, i want to take your opinion about my design.
1. as my system includes microcontroller, all controls and measurements are made by it. so i decided to use an opamp controllable feedback (please see the attachment). the microcontroller will measure output current and will apply the required pwm signal to the RTN pin of the opamp. by increasing optocupler's current, output voltage could be decreased so the output current will be constant. is it a good way of controlling voltage 20-28VDC.
2. as you know my design is 280W so i choose a KoolMu 77083 core for PFC circuit. the design guide says that it is better to ferrit core. do you approve it.
3.which core can i choose for LLC transformer? can you give me core type for 280W design.

thanks for your help.
have a nice day.

PLC810PG CC feedback circuit

1) It is probably simpler to just use a current sense resistor connected to the RTN node.

2) A PQ3230 would probably work for the PFC choke if you have some airflow.

3) An ETD39 would probably be a good starting point.

thanks for your help,

i'll apply your suggestion to my design.

have a nice day & work.