-1

[![enter image description here][1]][1]enter image description hereI've this circuit of 60v to 12v buck converter. In this UC3845B is used for gate firing. I didn't get one thing in the circuit that the Cathode of rectifier diode is connected to the ground of Error Amplifier circuit or Gate firing circuit.What is the purpose of doing this? P.S. This circuit is proven and working perfectly fine.

[![enter image description here][3]][3]

Hrishikesh Dixit
  • 87
  • 1
  • 7
  • The circuit may be proven and working perfectly fine but it's invisible to all readers of this site. – Andy aka Sep 09 '18 at 13:27
  • My apologies as i'm new to web site. I've uploaded the image of circuit – Hrishikesh Dixit Sep 09 '18 at 13:31
  • The schematic is very badly laid out. See [Rules and guidelines for drawing good schematics](https://electronics.stackexchange.com/questions/28251/rules-and-guidelines-for-drawing-good-schematics/28255?s=1|0.0000#28255) for some excellent guidance. You should also turn off the grid before taking screengrabs. – Transistor Sep 09 '18 at 14:01

1 Answers1

0

I didn't get one thing in the circuit that the Cathode of rectifier diode is connected to the ground of Error Amplifier circuit or Gate firing circuit.

It's the anode of both diodes that is connected to ground: -

enter image description here

The cathodes are connected to the switching output from the MOSFET and this is conventionally how a buck converter works: -

enter image description here

Andy aka
  • 434,556
  • 28
  • 351
  • 777
  • If you can see the below circuit of Uc3845B, u can see the netlist connected via Port 4; which is ground of 3845B. – Hrishikesh Dixit Sep 09 '18 at 13:48
  • Yes I see that and expect that to be present but what is your point? – Andy aka Sep 09 '18 at 13:51
  • Anode is grounded so that it can work when switch is off. But cathode is connected to ground of error amplifier circuit. Can you explain why? I've highlighted the nets in red in updated image – Hrishikesh Dixit Sep 09 '18 at 13:54
  • It looks like a mistake to me because it would short the switching output completely given the GND is also a net used in both upper and lower circuit. Check the PCB to see what really happens - possibly there is a cut in a track somewhere. – Andy aka Sep 09 '18 at 13:56
  • Exactly !! It also seemed to be mistake to me. But this circuit is working perfectly fine. – Hrishikesh Dixit Sep 09 '18 at 13:57
  • Check the PCB.. – Andy aka Sep 09 '18 at 13:58
  • Please check the image of PCB https://i.stack.imgur.com/ECruL.jpg https://i.stack.imgur.com/P34Td.jpg – Hrishikesh Dixit Sep 09 '18 at 14:25
  • You are better placed than me to look for modifications and now is your chance to demonstrate your skills with a multimeter and buzz the "rogue" connection. – Andy aka Sep 09 '18 at 14:51