Hi All,
I am currently trying to use a N6752A to emulate a battery charger. This is a task that I often perform with the E3633A. The task involves forcing the supply into CC mode with a voltage and current limit. I use a source meter(in this case the N6785A) to sink the current. The idea is that the supply increases current until it hits the current limit. Then, when the voltage at the source meter increases, the supply enters CV mode and reduces the current to maintain the voltage set by the SMU.
For the E3633A this works perfectly. I am able to set a 4.4V/2A limit and enable/disable the supply. For the N6752A this also works well in steady state. However, when I enable or disable the supply, it seems like the supply pulls down the SMU before the supply enters high impedance mode. I have attached the scope shot image of this - SMU in pink, N6752 in yellow. I am wondering if there is a setting to allow the N6752A to enter high impedance mode when either being enabled or disabled.
As a side note I saw that option 61(output disconnect relays) would probably work for this by physically disconnecting the supply. I would like to find an alternative way if possible. Does option 61 get installed into the power supply module? Or does it get installed into the mainframe?
Thanks,
JB
Hello JB,
Looks like you have captured the down-programming capabilty of the N6752A power supply module. This is used to deliver short voltage down-programming (fall) time when you need to generate arbs. The down-programmer sinks power from the connected circuit and allows us not to wait for longer time when the voltage will drop to zero. However, this adds the complexety when you do not need power supply to sink power. We have described similar issue in our blog post here (part 1) and here (part 2). You can find some work around tips there.
You have a good point about using the Option 761 "Output Disconnect Relays" but I'm not sure if it will open the circuit immidiately before down-programmer starts to sink power when you hit "Off" button on the channel or via SCPI. The option is installed in module and correcsponding checkbox on the module should be marked near the Product number (reffer to the picture attached). The option is only factory installable and should be offered only for new module.
Best regards,
Alexey