I am using Digilent Analog Discovery.
I have a Delta Electronics 19V adapter. I have seen very high noise. When laptop charging.
Products - AC/DC Adapters - ADP-65JH BB - Delta Group
Adapter has very high noise and 300mV ripple.
Do you have suggestion?
I have a Delta Electronics 19V adapter. I have seen very high noise. When laptop charging.
Products - AC/DC Adapters - ADP-65JH BB - Delta Group
Adapter has very high noise and 300mV ripple.
Do you have suggestion?
Any laptop does not require a smooth supply and ripple doesn't matter because it is catered for within the laptop.
As Jon has already explained, the laptop doesn't care. The laptop has got an accumulator (battery) inside that acts as a huge capacitor. The charger is designed for charging laptop batteries.
If you use the charger for instance with an audio power amplifier, you can add a solid capacitor at the charger output (2200uF-10000uF) and you have much less ripple. Chargers are manufactured to be cheap and used for this particular purpose. If we chose to use them for another purpose, it it for us to modify them for that purpose.
Ok.
Scope is very fine working with laptop battery. (Not connected adapter)
When laptop charging, I don't mesurement correctly small signalls.
Because charge adapter is very high noise generating.
Scope is very fine working with laptop battery. (Not connected adapter)
When laptop charging, I don't mesurement correctly small signalls.
Because charge adapter is very high noise generating.
This kind of problem is invariably caused by common-mode noise and/or Y capacitors: cheap supplies generate a lot of CM hash, which is then masked by a large Y cap (not actually removed) to pass EMC tests.
Unfortunately, the noise is still present, but instead of being generated by a ~high-impedance, ~high-voltage source, it appears to come from a low-voltage, low impedance source, but the result when the ground is connected via a low impedance path is an almost identical noise current, and in addition, the Y cap closes ground/mains circuits in HF, creating HF ground loops and coupling hash from other sources.
The simplest solution is to operate the laptop from the battery for critical measurements.
Otherwise, a classical linear supply with a low capacitance transformer is the best solution.
Medical supplies are also much better, but much more expensive than the OEM brick.
Unfortunately, the noise is still present, but instead of being generated by a ~high-impedance, ~high-voltage source, it appears to come from a low-voltage, low impedance source, but the result when the ground is connected via a low impedance path is an almost identical noise current, and in addition, the Y cap closes ground/mains circuits in HF, creating HF ground loops and coupling hash from other sources.
The simplest solution is to operate the laptop from the battery for critical measurements.
Otherwise, a classical linear supply with a low capacitance transformer is the best solution.
Medical supplies are also much better, but much more expensive than the OEM brick.
Or isolate the device being measured from any earthed connection (in a safe manner), so that the ground loop is cut (but in another spot in the loop).
Many possible ways 🙂
Many possible ways 🙂
- Status
- Not open for further replies.