Magnethicc
Member level 2
Hi everyone,
I need to design an isolated 30W housekeeping power supply:
Topology = Flyback
Input Voltage = +30VDC (Primary)
Output Voltage = +17VDC (Secondary), +12V (Primary Sensing)
Output Power = ~30W (Almost all of it to the +17VDC secondary output)
Efficiency = ~90%
Control = Peak Current Mode Control with Primary side sensing
Switching Frequency = 120kHz
X'mer:
Magnetic Core = PC40-EER28L, AL=240nH/N^2
Peak Flux Density = 200mT
Number of Primary Turns = 30 (Lprimary = 216uH)
Number of Secondary Turns = 15
Number of Sensing Turns = 11
Build -
1- Primary - 2 Wires x 15Turns
2- Primary Sensing - 1 Wire x 11Turns
3- Secondary - 2 Wires x 15T
4- Secondary - 2 Wires x 15T (In parallel with 3)
5- Primary - 2 Wires x 15Turns (In series with 1)
Input Calculations:
Duty came out to be 0.522
Input Average Current = ~1A
Input Peak Current =2.2A
Input RMS Current = 1.35A
Input Winding Current Density = 5.5A/mm^2
Output Calculations
+17V Ripple Current = 1.25A
+17V Winding RMS current = 2.3A
+17V Winding Current Density = 4.5A/mm^2
Notes:
* MOSFET - TPH5900CNH,L1Q - 64mOhms
* +17V Output Diode - 3x RF201LAM2S - Fast Recovery, 3 In parallel
* The +17V is supplying 3 Fans as well as a Buck Converter (Stable +12V)
Questions:
1. Does anyone have any notes regarding the design above?
2. Does anyone have any experience with low input voltage flybacks and could give me some tips to consider while designing and laying it out?
Thank You.
I need to design an isolated 30W housekeeping power supply:
Topology = Flyback
Input Voltage = +30VDC (Primary)
Output Voltage = +17VDC (Secondary), +12V (Primary Sensing)
Output Power = ~30W (Almost all of it to the +17VDC secondary output)
Efficiency = ~90%
Control = Peak Current Mode Control with Primary side sensing
Switching Frequency = 120kHz
X'mer:
Magnetic Core = PC40-EER28L, AL=240nH/N^2
Peak Flux Density = 200mT
Number of Primary Turns = 30 (Lprimary = 216uH)
Number of Secondary Turns = 15
Number of Sensing Turns = 11
Build -
1- Primary - 2 Wires x 15Turns
2- Primary Sensing - 1 Wire x 11Turns
3- Secondary - 2 Wires x 15T
4- Secondary - 2 Wires x 15T (In parallel with 3)
5- Primary - 2 Wires x 15Turns (In series with 1)
Input Calculations:
Duty came out to be 0.522
Input Average Current = ~1A
Input Peak Current =2.2A
Input RMS Current = 1.35A
Input Winding Current Density = 5.5A/mm^2
Output Calculations
+17V Ripple Current = 1.25A
+17V Winding RMS current = 2.3A
+17V Winding Current Density = 4.5A/mm^2
Notes:
* MOSFET - TPH5900CNH,L1Q - 64mOhms
* +17V Output Diode - 3x RF201LAM2S - Fast Recovery, 3 In parallel
* The +17V is supplying 3 Fans as well as a Buck Converter (Stable +12V)
Questions:
1. Does anyone have any notes regarding the design above?
2. Does anyone have any experience with low input voltage flybacks and could give me some tips to consider while designing and laying it out?
Thank You.