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Output disabled by over-voltage protection

Question asked by SYLye on Dec 20, 2010
Latest reply on Jan 4, 2011 by StevenLee

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Hi,
I am having Agilent Technologies Low-Profile Modular Power Systems mainframe, N6700B with DC power module N6732B.
My OV protection is set as 7.5V. The voltage supply is set as 5V, current = 0.5A
When I connect the power supply to my circuit, it shown OV failure.
Using another power system to supply same V & A, the circuit is running fine without failure.
Why is there indication of OV? What does it means?

Thanks.

-SY

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StevenLee Dec 21, 2010 1:01 PM
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Hi,

OV means over-voltage protection which means the power supply output has exceeded 7.5V. There could a number of different reason for this behavior. Let's start by trying to understand the setup here. Just a few questions for my understanding if you dont mind

1. Is the moduels in local or remote sensing?
2. What is the power supply being connect to? Resistance load?
3. Are you hot switching? Basically that means with the output fully on you then connect the leads to the DUT?

Let me know and hopefully we can find the reason based on the answers to the above questions.

Steven
Agilent Technologies
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SYLye Dec 21, 2010 8:08 PM
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Hi Steven,

I got some clue during other test runs yesterday. Basically, I reduce the supply voltage to 4V and current to 0.08A and the circuit is running fine. OVP happened on higher voltage / current supplied.

If I am not mistaken, there is a voltage drop in the load leads (due to over-supply voltage to certain component, maybe), the voltage sensed by OVP thus higher than the voltage being regualted at the load. Thus, system trigger the OVP failure.

1. Is the moduels in local or remote sensing? Remote sensing
2. What is the power supply being connect to? Resistance load? Resistance load
3. Are you hot switching? Basically that means with the output fully on you then connect the leads to the DUT? Yes

Aprreciate your comments.

Thanks.

-SY
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SYLye Dec 26, 2010 10:20 PM
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HI Steven,

Due to the OVP, I am having problem to set the power module to CC mode.
The power module trigger OVP instead of change to CC mode when the voltage is increase / resistance is decreased.
Below examples is done based on simple resistor-only circuit.

For example:
Case 1: Voltage setting = 5V; Current setting = 0.06A (min current setting) with a 500 Ohm resistor.
The unit in CV at 0.01A

To have CC mode:
Case 2: Voltage setting = 5V; Current setting = 0.06A with a 50 Ohm resistor.
The unit should go into CC mode at 0.06A and the voltage is 3V.
Instead of go into CC mode, the power module trigger OV.
The maximum Voltage applicable to a single 50 Ohm resistor without OV failure is 0.5V (Current setting = 0.06A)

Can you please help on this?

Thanks.

-SY
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StevenLee Jan 4, 2011 7:35 AM
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Hi SY Lye,

Can you answer questions 1 and 3 below? I still don't have a clear answer to those two questions.

1. Is the moduels in local or remote sensing?
2. What is the power supply being connect to? Resistance load?
3. Are you hot switching? Basically that means with the output fully on you then connect the leads to the DUT?

Can you give m a detail description of process that you are running? As much detail as possible including the order which you turn on the output and physically connect the resistor to the output.. What you are described to me is not something that I would expect from a functional power supply under the proper setup. So the problem is either going to be a defective power supply or a improper setup here. I'm trying to narrow down to see which one it might be.

Steven
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