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HOW TO USE THE SPREADSHEET
This spreadsheet will calculate for you every parameter needed to design a power supply using a NCL30488 controller.
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:
Minimum line Frequency:
Typical line frequency:
Maximum output current:
Minimum output voltage:
Maximum output voltage:
Estimated efficiency:
Output diode forward voltage:
Minimum output power:
Maximum output power:
Mosfet Coss:
MOSFET Rdson at Tj = 110 °C:
MOSFET breakdown voltage:
Derating factor for the MOSFET breakdown voltage:
Total gate charge:
Total Propagation delay time:
Maximum peak current:
Internal reference voltage for CC regulation:
Internal divider from Vcontrol to VCS:
Internal reference voltage for CV regulation:
Constant voltage OTA transconductance:
Brown-out thresholds:
Internal coefficient for VHV to VVS conversion:
Voltage to current conversion ratio on VIN pin:
Maximum current in ZCD pin:
ZCD input clamp voltage:
Threshold for leakage inductance reset detection:
Threshold for line range detection:
Supply Current device enabled, no load on DRV pin:
Startup threshold (minimum value):
UVLO threshold (minimum value):
Minimum DC voltage including bulk ripple (for transformer calculation):
Leakage inductance ratio (kleak = Lleak / Lp)
Clamping diode recovery time overshoot:
Output voltage for fast OVP triggering:
Estimated Clamping coefficient (k
( kc value should be selected between 1.5 and 2)
Choose maximum duty-cycle at sinus top, max Pout, low Line:
Calculate turn ratio:
Enter your value for Nsp (
At sinusoid top:
Choose Lp so that the switching frequency is below 130 kHz (Fsw) at the low line range nominal voltage (typ 115 V rms).
Practically, we can decide to meet this target starting from Vin,pk / 2:
Target Fsw at VinLLtyp,pk / 2:
Note
: The value of Lp may need to be adjusted later on to make sure that the demagnetization time is always above 2 µs when the output load is between 100% to 25% of nominal output load to garanty a proper CV operation (see: OUTPUT CURRENT VARIATION PARAGRAPH)
Enter your value for Lp:
Primary rms current at Sinus top (rms value over 1 switching cycle) and Vout,max:
Secondary peak current at Vout,max:
Secondary rms current at Sinus top (rms value over 1 switching cycle) and Vout,max:
Enter the normalized value for Rsense:
Power dissipated in sense resistor:
Desired value for VCC at Vout,min:
Enter your value for Naux:
VCC value at maximum output voltage:
Verify at which output voltage VCC OVP triggers:
If V outOVP2 is smaller than V outOVP , then V CC OVP will trigger before the fast OVP.
Choose a secondary rectifier with a breakdown voltage twice the one calulated above
The output capacitor must be large enough to avoid excessive current ripple in the LED.
Specify the ratio peak to peak ripple over dc output current value (cannot be grater than 1 to respect flicker index):
Minimum dynamic resistance of LED:
Output capacitor RMS current:
Choose Cout value such that it can handle the RMS current:
Enter your value for RLFF:
Enter your value for CS pin capacitor:
Ratio RZCDU / RZCDL for output voltage setpoint:
Choose a value for the upper resistor (RZCDU) between 10 kΩ and 100 kΩ:
Calculate the lower resistor value:
Time variable for zoom and operating point calculations:
Enter the line voltage and frequency to plot the output current:
Time variable for zoom: t2
To simplify expression writting:
CC operation neglecting leakage inductance and propagation delays:
Plots description:
- VCSLL(t): current sense voltage at Vout2 (by default VoutMAX) and VinLLrms
- VCSLL1(t): current sense voltage at Vout1 (by default VoutMIN) and VinLLrms
- VCSHL(t): current sense voltage at Vout2 (by default VoutMAX) and VinHLrms
- VCSLLOVP(t2): current sense voltage at VoutOVP and VinLLrms
- tdemag LL(t): demagnetization duration at Vout2 (by default VoutMAX) and VinLLrms
- tdemagH L(t): demagnetization duration at Vout2 (by default VoutMAX) and VinHLrms
- Fsw LL(t2): switching frequency at Vout2 (by default VoutMAX) and VinLLrms
- FswH L(t2): switching frequency at Vout2 (by default VoutMAX) and VinHLrms
- FswL L1(t2): switching frequency at Vout1 (by default VoutMIN) and VinLLrms
- FswL LOVP(t2): switching frequency at VoutOVP and VinLLrms
We consider the leakage inductance equal to 1% of primary inductance.
Leakage inductance coefficient:
Switching frequency at sine wave top, lowest line at VoutOVP
(extracted from THEORICAL WAVEFORMS section)
We choose a 6% voltage ripple for the clamping voltage:
* Rclamp peak power loss at sinus waveform top:
* Average power losses in Rclamp over one line cycle:
Maximum junction temperature:
Typical ambient temperature:
Maximum ambient temperature:
* MOSFET Switching losses :
* Outout Diode calculation
Thermal Resistances of diode package:
Maximum junction temperature:
We can deduce the package power dissipation:
Chosen diode parameters (example MURD530 diode in DPAK package)
* MURS 230 in SMB package:
* MURD530 in DPAK package:
* MURD340 in DPAK:
* MURD550 in DPAK
Max Forward voltage drop at Iout (25°C):
Diode dynamic resistance
(can be extracted from diode I-V curves in datasheet):
Power dissipated by the diode (worst case):
* Dummy-load resistor estimation
If we consider there is no input voltage ripple in standby:
* Dummy-load resistor estimation
If we consider there is no input voltage ripple in standby: