I'm working on a TP4056-based 1S LIPO solar charger which includes a load sharing (aka power path) function. But I don't have a panel to test with. So I'd like to simulate the circuit in LT-Spice.
But I've never used spice, LT or otherwise, so I was hoping to find an example of a solar panel equivalent circuit that I could import, then add the rest of the circuit, which is pretty simple.
Can someone suggest where I would find such a file? It would be something like a 5V panel, 200mA.
Wild guess to open discussion: a string of silicon power diodes with a parallel current source that represents illumination.
LT Spice is great. It shouldn't take long to enter and run a circuit; ask here if it doesn't work. There are no doubt a lot of tutorials on youtube.
Get a panel. You may have to settle for 12V, based on availability from current consumer cast-offs.
RL
Put this in your standard.dio:
*I_DD=Isc-Voc/Ri=8.563-0.622/1.156=8.024 *I_s=300n(guess) *U_T=26mV *U_D=0.622 *n*U_T*ln(I_DD/IS)=U_D *n=U_D/(U_T*ln(I_DD/IS))=1.398 *duh.. have2guess for a better fit *I_s=3n .model PVCELL D(Is=3n N=1.1)^MThis in an .asc:
Version 4 SHEET 1 988 812 WIRE -288 192 -288 176 WIRE -288 704 -352 704 WIRE -288 768 -352 768 WIRE -192 176 -288 176 WIRE -192 176 -192 64 WIRE 64 64 -192 64 FLAG -192 256 0 FLAG -288 768 0 FLAG 64 144 0 SYMBOL current -192 256 R180 WINDOW 0 24 88 Left 0 WINDOW 3 24 0 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName I1 SYMATTR Value 8.563 SYMBOL diode -304 192 R0 SYMATTR InstName D1 SYMATTR Value PVCELL SYMBOL diode -304 256 R0 SYMATTR InstName D2 SYMATTR Value PVCELL SYMBOL diode -304 320 R0 SYMATTR InstName D3 SYMATTR Value PVCELL SYMBOL diode -304 384 R0 SYMATTR InstName D4 SYMATTR Value PVCELL SYMBOL diode -304 448 R0 SYMATTR InstName D5 SYMATTR Value PVCELL SYMBOL diode -304 512 R0 SYMATTR InstName D6 SYMATTR Value PVCELL SYMBOL diode -304 576 R0 SYMATTR InstName D7 SYMATTR Value PVCELL SYMBOL diode -304 640 R0 SYMATTR InstName D8 SYMATTR Value PVCELL SYMBOL diode -368 704 R0 SYMATTR InstName D9 SYMATTR Value PVCELL SYMBOL current 64 64 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName I2 SYMATTR Value PWL(0 0 1 8.563) TEXT -370 796 Left 0 !.tran 0 1 0 0.001
Apologies,
A phony carriage return slipped in... More correct:
*I_DD=Isc-Voc/Ri=8.563-0.622/1.156=8.024 *I_s=300n(guess) *U_T=26mV *U_D=0.622 *n*U_T*ln(I_DD/IS)=U_D *n=U_D/(U_T*ln(I_DD/IS))=1.398 *duh.. have2guess for a better fit *I_s=3n .model PVCELL D(Is=3n N=1.1)
Yes, back when I was doing a MPPT function in a Space design, we just used the diode string for simulation and test
Just remember to add a lot of capacitance, since that can be huge on solar arrays
Cheers
Klaus
Thanks very much.
Can you tell me what all of that produces - in terms of the open circuit voltage and the short circuit current of a panel? Sorry to be so dense, but I have no experience with simulation at all. So does all of this create a new "device" that I can place on the schematic?
It's all guesses. bad ones. I tried to calculate an N. but it turned ot wrong. so it's trial and error basically. (the lines starting with * are all comments)
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