Riassunti Automotive Electronics Systems, prof. Puglisi

AUTOMOTIVE ELECTRONIC SYSTEMS

NUTS AND BOLTS OF ELECTRONICS

• OPEN CIRCUIT ➔ AN IDEAL OPEN CIRCUIT IS SOMETHING WHERE THE CURRENT IS ALWAYS GOING TO BE ZERO, REGARDLESS THE VOLTAGE ACROSS IT.
• SHORT CIRCUIT ➔ AN IDEAL SHORT CIRCUIT IS AN ELEMENT THAT HAS A ZERO DROP VOLTAGE BETWEEN ITS NODES, REGARDLESS THE CURRENT FLOW ACROSS IT.
• IDEAL VOLTAGE SOURCE ➔ IT IS AN ELEMENT THAT HAS A CONSTANT VOLTAGE, REGARDLESS THE CURRENT FLOW THROUGH IT.
• IDEAL CURRENT SOURCE ➔ IT IS AN ELEMENT THAT PRODUCES A CONSTANT CURRENT, REGARDLESS THE VOLTAGE AT ITS ENDS.
• RESISTOR ➔ IT IS AN ELEMENT THAT ESTABLISHES A LINEAR RELATIONSHIP BETWEEN VOLTAGE AND CURRENT (FIRST OHM’S LAW): ΔV = R · I
  • WHERE [R] = OHM = Ω IS THE RESISTANCE!
  • A RESISTOR CAN ONLY ABSORB ENERGY AND CANNOT PRODUCE IT:
  • [P] = WATT = W ➔ P = ΔV · I = R · I² = ^ΔV2/_R
• SERIES CONNECTION:
  • V_A — R₁ — R₂ — V_B
  • I₁ = I₂ ➔ R_eq = R₁ + R₂
• PARALLEL CONNECTION:
  • V_A — R₁
  • ΔV₁ = ΔV₂ ➔ R_eq = (¹/_R1 + ¹/_R2)^-1

AUTOMOTIVE ELECTRONIC SYSTEMS

NUTS AND BOLTS OF ELECTRONICS

• OPEN CIRCUIT → AN IDEAL OPEN CIRCUIT IS SOMETHING WHERE THE CURRENT IS ALWAYS GOING TO BE ZERO, REGARDLESS THE VOLTAGE ACROSS IT.
• SHORT CIRCUIT → AN IDEAL SHORT CIRCUIT IS AN ELEMENT THAT HAS A ZERO DROP VOLTAGE BETWEEN ITS NODES, REGARDLESS THE CURRENT FLOW ACROSS IT.
• IDEAL VOLTAGE SOURCE → IT IS AN ELEMENT THAT HAS A CONSTANT VOLTAGE, REGARDLESS THE CURRENT FLOW THROUGH IT.
• IDEAL CURRENT SOURCE → IT IS AN ELEMENT THAT PRODUCES A CONSTANT CURRENT, REGARDLESS THE VOLTAGE AT ITS ENDS.
• RESISTOR → IT IS AN ELEMENT THAT ESTABLISHES A LINEAR RELATIONSHIP BETWEEN VOLTAGE AND CURRENT (FIRST OHM’S LAW): ΔV = R·IWHERE [R]= OHM = Ω IS THE RESISTANCE!A RESISTOR CAN ONLY ABSORB ENERGY AND CANNOT PRODUCE IT:[P]= WATT = W → P = ΔV·I = R·I² = ^ΔV²/_R
• SERIES CONNECTION: I₁ = I₂ => R_eq = R₁ + R₂
• PARALLEL CONNECTION: ΔV₁ = ΔV₂ => R_eq = (¹/_R1 + ¹/_R2)^-1

KIRCHHOFF LAWS

• A NODE IS A POINT WHERE AT LEAST THREE BRANCHES MEET.
• A BRANCH IS WHAT STAYS BETWEEN TWO NODES.

FIRST KIRCHHOFF LAW → THE ALGEBRAIC SUM OF THE CURRENTS IN A NODE IS ZERO!

SECOND KIRCHHOFF LAW → STARTING FROM A POINT OF OUR CIRCUIT AND COMPLETING A CLOSED PATH, THE ALGEBRAIC SUM OF THE VOLTAGE DROPS IS ZERO!

CAPACITOR ➔ IT IS AN ELEMENT THAT ESTABLISHES A LINEAR RELATIONSHIP BETWEEN THE STORED CHARGE AND THE VOLTAGE: Q = C.ΔV WHERE [ C ] = FARAD➔ F IS THE CAPACITANCE!

dQ/dt = I = C dV/dt ➔ IF THERE IS A CONSTANT VOLTAGE DROP BETWEEN THE TWO ENDS OF THE CAPACITOR, THERE WON’T BE CURRENT FLOW THROUGH IT; INSTEAD, IF THERE IS A TIME-DEPENDENT VOLTAGE DROP, THERE WILL BE CURRENT FLOW!

SERIES CONNECTION →

Q₁ = Q₂ ➔ C_eq = (1/C₁ + 1/C₂)^-1

PARALLEL CONNECTION →

ΔV₁ = ΔV₂ ➔ C_eq = C₁ + C₂

INDUCTOR ➔ IT IS A NON-LINEAR ELEMENT: INDUCTORS STORE MAGNETIC ENERGY WHEN THEY ARE FED WITH A NON-CONSTANT CURRENT OVER TIME:

ΔV_e = L · dI/dt WHERE [ L ] = HENRY➔ H IS THE INDUCTANCE

SERIES CONNECTION →

L_eq = L₁ + L₂

PARALLEL CONNECTION →

L_eq = (1/L₁ + 1/L₂)^-1

EQUIVALENT CIRCUITS:

1. THEVENIN’S THEOREM ➔ A GENERIC BLACK BOX NON-DYNAMIC LINEAR CIRCUIT OBSERVED BY TWO NODES CAN BE REPRESENTED BY A SERIES OF AN IDEAL VOLTAGE GENERATOR AND A RESISTOR

2) Norton's Theorem

A generic black box non-dynamic linear circuit observed by two nodes can be represented by a current source in parallel with a resistor.

• Charging/Discharging a Capacitor

1) Charging a Capacitor

No current can flow through the right mesh because during the charging, T₂ switch is closed and T₂ switch is open!

T₁ and T₂ are two ideal switches and ΔV comes from a battery since it can be considered a source of constant voltage; at t=0⁺ the capacitor is discharged since it has no charge stored yet. When T₁ gets closed the voltage ΔV must fall across the series R and C.

ΔV = ΔV_C + ΔV_R = R⋅I + ^Q/_C = constant over time while RI and ^Q/_C vary during the cha