Power supply control issue with PXI-6221

[Yongqiang]

I am using on PXI-6221 card to control 8 TDK-Lambda UP60-7 power supplies, with the analog ouput as the control voltage. Each power supply works individually but share the same control voltage. The system used to work fine until a shortage happened in the circuit loop of one power supply. Now if I power up more than 4 of them, the output voltage become very unstable.  I turned on each one of them, two of them, up to 4, the input/output is acceptable. As I turned on more of them, the unstability became worse and worse.

has anybody got experience on this? any inputs?

thanks a lot!!!

[jyang72211]

Would it be possible that the analog out is not supplying enough current for the control input of the power supply?  A easy thing to try would be to use two analog output for more current and see would that solve the problem.  You mentioned that there was a shortage in the control loop.  Did you mean you had a short?  Was there sparks?  What happened?  Maybe your PCI card got damaged. 

[Chris V]

Hi Yongqiang,

jyang72211 asks a good question: what was the severity of the short you had?  Could it have affected/damaged the board?

It looks like the PXI-6221 has two analog outputs.  Have you tried both of them and gotten the same behavior?

According to the spec sheet, each can only output +/- 5 mA. Could you possibly be trying to draw more current than this?

Have a great day,

Chris