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##

## PathSim example of a diode circuit

## (Nonlinear algebraic loop)

##

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# IMPORTS ===============================================================================

import numpy as np

import matplotlib.pyplot as plt

from pathsim import Simulation, Connection

from pathsim.blocks import (

Source,

Amplifier,

Function,

Adder,

Scope

)

# DIODE CIRCUIT =========================================================================

# Circuit parameters

R = 1000.0 # Resistor (Ohms)

I_s = 1e-12 # Diode saturation current (A)

V_T = 0.026 # Thermal voltage at room temperature (V)

# Define diode current function: i = I_s * (exp(v_diode/(n*V_T)) - 1)

def diode_current(v_diode):

"""Diode current as function of diode voltage"""

clipped = np.clip(v_diode/V_T, None, 23)

return I_s * (np.exp(clipped) - 1)

# Define voltage source function

def voltage_source(t):

"""Sinusoidal voltage source"""

return 5.0 * np.sin(2 * np.pi * t)

# Blocks that define the system

Src = Source(voltage_source) # Voltage source

DiodeFn = Function(diode_current) # Diode i-v characteristic

ResAmp = Amplifier(-R) # -R (negative resistance)

Add = Adder() # Adder for KVL

Sc1 = Scope(labels=["v_source", "v_diode"])

Sc2 = Scope(labels=["i_diode"])

blocks = [Src, DiodeFn, ResAmp, Add, Sc1, Sc2]

connections = [

Connection(Src, Add[0], Sc1[0]), # Source to adder and scope

Connection(Add, DiodeFn, Sc1[1]), # Diode voltage to function and scope

Connection(DiodeFn, ResAmp, Sc2), # Diode current to resistor and scope

Connection(ResAmp, Add[1]), # Voltage drop back to adder (algebraic loop)

]

# Simulation instance

Sim = Simulation(

blocks,

connections,

dt=0.01,

tolerance_fpi=1e-12

)

# Run Example ===========================================================================

if __name__ == "__main__":

# Run the simulation for 2 seconds

Sim.run(duration=2.0)

# Plot the results

Sim.plot()

plt.show()