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HOW TO USE THE SPREADSHEET
This spreadsheet will calculate for you every parameter needed to design a power supply using the NCP1380 or the NCP1379.
The zones underlined in pink need data from the user.
The zones underlined in yellow are calculation results.
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Minimum AC input voltage:
Maximum AC input voltage:
Maximum output power:
Output voltage:
Estimated efficiency:
Output diode forward voltage:
Switching frequency at maximum output power, low line:
Mosfet Coss:
MOSFET Rdson at Tj = 110 °C:
Bulk voltage ripple:
Minimum DC voltage including bulk ripple (for transformer calculation):
Total Propagation delay time:
MOSFET breakdown voltage:
Derating factor for the MOSFET breakdown voltage:
Leakage inductance ratio (kleak = Lleak / Lp)
Clamping diode recovery time overshoot:
The losses caused by the clamping resistor are plotted below for different value of kleak.
Clamping coefficient (k
Enter your value for Nps:
Enter your value for Lp:
Enter the normalized value for Rsense:
Auxiliary winding turn ratio
Desired value for VCC:
Desired Output voltage ripple:
Enter your choice of output capacitor:
Panasonic serie FM: Two 680 uF cap (3.29 A, 16m, 35 V)
Designer value for Ct:
* The function named "Chrono" below allows to calculate the peak current and the switching frequency for a defined output power and for a defined valley.
INPUTS:
OUPUT: a two line vector containing the peak current (1st line) and the switching
* The function below calculate the switching frequency and the corresponding valley for a decreasing output power.
Indeed, as there is hysteresis for the valley lockout, for a given ouput power, we can have two different couple of (Ipk,Fsw) delivering the same ouput power.
INPUTS: - Pmax: the starting output power
OUTPUT: a matrix containing the switching frequency, the peak current and the
* The function below calculate the switching frequency and the corresponding valley for an increasing output power.
Indeed, as there is hysteresis for the valley lockout, for a given ouput power, we can have two different couple of (Ipk,Fsw) delivering the same ouput power.
INPUTS: - Pmin: the lowest starting output power
OUTPUT: a matrix containing the switching frequency, the peak current and the
Predicting the evolution of the switching frequency
Enter below the input voltage (rms) at which you want to see the frequency evolution (these voltage will also be used for the losses calculation)
Note:
The MOSFET losses (conduction and switching) are calculated only for the quasi-resonant mode from the 1st valley to the 4th valley.
The losses are not calculated in VCO mode and that's why the curves shows a zero value at low output power.
Total propagation delay:
Output power capability at high line:
Ouput power limit wanted by the power supply designer:
The corresponding peak current is:
The corresponding switching frequency is:
OPP peak current reduction :
Primary to Auxiliary winding (Naux/Np) turn ratio:
OPP lower resistor:
Note to the power supply designer:
The maximum OPP voltage that can be applied to the NCP1380 is -0.3 V.
Applying OPP voltage lower than -0.3 V can lead to an erratic behavior of the OPP.
If the OPP voltage calculated is below this limit, the output power limit must be increased.
We consider the leakage inductance equal to 1% of primary inductance.
We consider a 20% ripple on Vclamp to calculate Cclp:
Startup resistor calculation
Chosen value for Cvcc1:
*Half wave connexion
dc voltage at which the controller should start switching:
dc voltage at which the controller should stop switching:
BO bridge lower resistor calculation:
BO bridge lower resistor calculation:
* MOSFET Heatsink Calculation
MOSFET C
Power loss at minimum input voltage
Junction temperature for MOS die :
Ambient temperature :
Heatsink calculation :
Junction to case coefficient (°C/W):
Case to heatsink coefficient (°C/W):
* O
Diode forward voltage at low current:
Diode dynamic resistance:
Junction temperature for diode die :
Ambient temperature :
Heatsink calculation :
*
*
*
*
MOSFET C
Power loss at minimum input voltage
*
*
Diode forward voltage at low current:
Diode dynamic resistance:
Junction temperature for diode die :
Ambient temperature :
Heatsink calculation :
Peak inverse voltage :
*
Bulk cap:
Minimum bulk voltage (including ripple):
Threshold voltage of one diode of the diode bridge:
Dymanic resistance of one diode of the diode bridge:
(The diode bridge used is a KBU4K)
Line frequency:
Diode conduction time:
*
Secondary winding DC resistance:
Secondary winding AC resistance:
Secondary winding DC resistance:
Secondary winding AC resistance:
Core loss:
* Total losses at max input power
Estimated efficiency at low line:
Mosfet : 1 MOS IRFS4321PBF BV = 150 V D²PAK
RdsON @ Tj = 110°C :
Body diode voltage drop:
NCP4302 delay time:
At minimum input voltage:
Total power loss with synchronous rectification
Estimated efficiency with SR:
FB pullup resistor inside NCP1380:
Current in the TL431 bridge:
Optocoupler transfer ratio:
Optocoupler parasitic capacitance:
Desired Cross over frequency:
Desired phase margin:
Needed phase boost: