Hello, expert.
This is the waveform of SW Pin of MP8017 demo board.
Is the waveform in the black circle okay?
I think the waveform will affect the efficiency.
Please let me know if there is any way to improve it.
Thank you.
Hello @sw-yun,
Which MP8017 demo board is this waveform referring too? Can you mention the complete demo board part number?
Hello, expert.
The demo board number is ML8017-L-00B.
Hello @sw-yun,
Thank you for confirming the board number. What were the test conditions(input and output voltages and currents) where this switch node waveform was observed?
Input voltage: 37~57VDC
Output voltage: 5V/2.4A
Switching frequency: 500KHZ
Increasing R19 resistor reduces notch.
But there is oscillation in the 2nd synchronous rectifier FET.
However, within what range can C4 be adjusted?
Hello @sw-yun,
I checked the eval board EVL8017-L-00B schematic and could only find C4 connected to SNBR pin.
Were there any modifications made on the eval board? Can you also share the waveform at SNBR pin?
The data sheet contains the schematic for the SSR FLYBACK.
(page 27)
I use Trans EP7, can I change the frequency from 500KHZ to 300KHZ?
Hello @sw-yun,
Yes, the MP8017 can also controlled using secondary side regulation as well. The notch observed is due to the presence of transformer leakage inductance, at the moment when Sync MOS is turned off, the leakage inductance extracts energy from the parasitic capacitance of Main MOS, resulting in a drop on the SW node voltage. This will not cause any damage to the FETs.
You can use the part at 300 khz with the EP7 transformer. You would also need to make sure the transformer primary inductance, peak drain currents of the FETS are taken into consideration.
Can you please calculate the trans inductance value?
Hello @sw-yun,
For the given parameters, your transformer inductance value should be around 80-85uH.
Hi.
EP7 transformer can’t make 80uH.
Should I change it to EP10?
Can you calculate the number of turns?
