H
Henrik [7182]
- Jan 1, 1970
- 0
Hello Experts,
This is my first time designing a SEPIC type switchmode power supply with
the LM3478MM from national as my controller.
My design is pretty much the standard application as shown in the datasheet.
The design is made to supply 24V out from a 15-32V input. Ouput current is
1A.
My problem is that my two inductors and the MOSFET gets insanely hot. Much
more hot that I had anticipated. So I wonder if there is somewhere I have
missed something vital.
I am using CDRH127 series 22uH inductors from Sumida, which are rated at
3.3Amp and has a DCR of 43mR
I use a 39K resistor to obtain approx. 400kHz switch frequency.
I use 7mR as Rsense and MBRS360 as my power diode.
My Compensation-filter consists of 100nF and 1K.
My Mos-Fet is NP55N055 from NEC which has 12.5mR on-resistance.
Since I am a novice in the field of SMPS, this has me baffled quite a bit,
and I hope that someone could lead me on right path.
Thanking you all in advance.
Best regards
Henrik
This is my first time designing a SEPIC type switchmode power supply with
the LM3478MM from national as my controller.
My design is pretty much the standard application as shown in the datasheet.
The design is made to supply 24V out from a 15-32V input. Ouput current is
1A.
My problem is that my two inductors and the MOSFET gets insanely hot. Much
more hot that I had anticipated. So I wonder if there is somewhere I have
missed something vital.
I am using CDRH127 series 22uH inductors from Sumida, which are rated at
3.3Amp and has a DCR of 43mR
I use a 39K resistor to obtain approx. 400kHz switch frequency.
I use 7mR as Rsense and MBRS360 as my power diode.
My Compensation-filter consists of 100nF and 1K.
My Mos-Fet is NP55N055 from NEC which has 12.5mR on-resistance.
Since I am a novice in the field of SMPS, this has me baffled quite a bit,
and I hope that someone could lead me on right path.
Thanking you all in advance.
Best regards
Henrik