MP6951 Power estimation

AC-DC Power Converters
1

Hello, I am using the MP6951 and it is running quite hot (~130°C with an ambiant of ~25/30°C). I am therefore trying to compute an estimate of the device power it dissipates.

The datasheet gives a typical operating current of ~2.3mA but no mention of the power source. I guess it is from HVC ? And if correct, this current would include: 1/ VDD capacitor charging current, 2/ MOSFET gate charging current and 3/ internal operating current , Am I correct ?

I can compute the second point 2/ current share and scale it according to my MOSFET arrangement but how can I derive the 1/ and 3/ shares ? Especially when a higher MOSFET gate load turns into a higher voltage drop on VDD capacitor and therefore a high charging time (higher average current).

Best regards

Pascal

2

Hi Pascal,

The two main power paths where heat generation could be present:

  1. Input current

  2. Driving the MOSFET

What is the voltage drop across the HVC and SRD resistors? You can then calculate input current.

What is your charging current of the MOSFET? Can be calculated with gate charge and switching frequency.

Best,

Tyler