• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Help with using UC3823n for a boost converter

Status
Not open for further replies.

darkfeffy

New Member
Hi all,

Please I need some help using the UC3823N PWM controller for a boost converter (with synchronous rectifier). I want to obtain 189Vdc at the output of the converter from a 48Vdc battery (for now used a dc supply). I have attached a schematic of the controller set-up and another for the boost.
My problem is the boost output voltage is lower than expected (55Vdc). The controller output duty is locked at 20% in this condition instead of approx 75%. I am using (Rt = 3.6kOhm and Ct = 4.7nF) and a +15Vdc supply. These give a 94kHz approx. frequency (as expected). I am using voltage mode control. The feedback (PIN 1) is a simple voltage divider that should convert 189Vdc to 2.55Vdc (to compare with the 2.55V reference). I have not used the E/A out pin (PIN 3) nor the CLK/LEB Pin (Pin 4). These pins are left floating. Vc (pin 13) is +15Vdc (I had tried connecting the Vc pin to a +5V supply but the controller wouldn't work, so I connected it to Vcc (pin 15) then it worked - I don't understand why). I inverted the output through a NAND before sending it to an IR21844 gate driver (which re-inverts the signals). Pin 1 reads 1.2V (this is less than the 2.55V reference). When the boost is NOT supplied, the controller gives an 85% duty (max) as expected. I used by-pass and filter capacitors. Any one help??

P.S: I wish to add that I used this very controller and this very set-up (but without the NAND inverter and with Vc = 5V) for a buck converter (96V to 52V) and it worked alright.

Thanks. Edwin
 

Attachments

darkfeffy

New Member
Suspected I might be having an issue with E/A pin unconnected, but I don't have much idea about doing compensation, control, etc...
Anyone help?
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top