Appunti Automotive electronic system

NON-LINEAR CIRCUIT

RECTIFIER = is an electrical circuit that converts Ac current to Dc current in 1 direction.

SUPERDIODE = Op-Amp+diode, it dont have voltage fall amd its close to 0 Volt.

PEAK-DETECTOR = used to determinate the max value of a input signal (implementation

with diode + capacitor),

(Active version with diode + capacitor + switch + op-amp)

CLAMPER = is a circuit that fixes the + or - peak excursion to a defined value, Dc value. It

moves the whole signal up or down to a reference level.

Ex:

Vin cost. + PU = Vout min. Value is 0.

Vin cost. + PB = Vout min. Value is >0.

Vin cost. + NU = Vout max value is 0.

Vin cost. + NB = Vout max value is <0.

DC-DC CONVERTERS = circuit that use the concept of switching to realixe step up and step

down conversion, uses bulky inductor, more noise but high efficiency.(es. Buck or Boost)

It only transfers energy in 1 direction, but there is a case that is Bidirectional like: Dc motors

drivers, fuel cells or regenerative braking.

CAPITOLO 5# (A/D and D/A)

It base on a control unit, it use digital computers to act as system controllers.

Digital signal is encoded in BINARY 0 and 1

(Anagol signal are continuous real number)

●Continuity→ Sampling (campionamento), is a process of taking n numbers and defining

them in a shape of a waveform, it converts analog signals in a series of impulses(T sampling

period-time).

“Shannon nyquist Theorem” = the min sampling frequency of x is 2x , Aliasing is the

phenomenon of have a different signal by sampling, the result samples are different by the

original signal.

Solution: anti-aliasing filter, that is a low-pass filter used before a sampled to resctrict the

bandwidth of a signal.

●Precision→ Quantization, is needed to reduce precision to infinite to a finite value, n bit

quantizer will have a set of 2^n value.

(8 bit = 256 levels, 16 bit = 65.000, 24 bit = 16,8 milion), sarebbe 2^n(bit).

SAMPLE AND HOLD CIRCUIT:

Circuit that realize the sampling task, switch is controlled by a clock signal at sampling

frequency, it select two operation:

●sample (switch on, capacitor charges up to the input voltage)

●hold (switch off, the capacitor holds the charge).

ADC CIRCUIT (A/D) are quantization circuit, typology:

-Flash ADC, (very fast)consists of a series of comparators(Op-Amp), each one comparing

the input signal to a unique reference voltage, the encoder generate a binary number based

on the input.

-Dual slope ADC, (slow) it uses an integrator+comparator+digital counter with a control logic.

-Successive approx. ADC, (fast) it use a comparator+DAC, it uses digital logic to converge to

the digital representation that is closest to the input voltage.

-Sigma Delta ADC, (high resolution but complicated) principle are oversampling and noise

shaping.

DAC CIRCUIT (D/A), based on resolution, monotonicity, noise and THD. Tipology:

- R-2R Ladder DAC, every bit can switch by 0 and Vref.

- Succ. Approx DAC, switch controlled by Dn line input.

-Sigma delta DAC, is a reverse ADC sigma.

RECONSTRUCTION FILTER (ZOH) = after a Dac you need something Else to get your

analog signal “Back”, it is a low pass filter at the nyquist frequency. (Band-limitated), should

have:

-cost. phase delay in the pass band, -cost. Flat frequency response, -zero response from

nyq frequency.

CAPITOLO 6# (DIGITAL DOMAIN)

Use for arithmetic with BINARY NUMBER and “Boolean Algebra”, 0 and 1 variable with

And(^), Or(v), Not(-).

●Shannon's theorem● = an output can always be written as a sum of the products of the

input (output is 1).

Karnaugh maps→ they use a toroidally connected grid with grey code ordered bits.

BINARY CODE→ n= Sum. Bi*2^i (es: 13= 1*2^3 + 1*2^2 + 0*2^1 + 1*2^0 = 8+4+0+1)

N-Bits Adder, is the bulding block to realize n-bits adder circuits.

Clock→ is a square wave signal that tells the circuit when the propagate info to the block.

(Es: RING OSCILLATOR, wave generator based on a simple looped chain of ODD number

of NOT gates)

-ENCODER = is a “one-shot” (all lines are logic 0 and 1 line logic 1) to binary converter, if

there are 2^n input lines and only 1 of them will ever be high it produces n-bit output lines.

(Input line are 2x output Line, es. 4 to 2 encoder)

-DECODER = is a combinational logic circuit that converts binary info from n-coded inputs to

max 2^n UNIQUE output. (Opposto al encoder, 2 input e 2x output e hot one line at output).

-MULTIPLEXER = is a device that select one of several input signal into a single line, n input

and 1 output, It needs N control input bits for 2^n input lines).

There are two kinds of logic circuits:

-COMBINATORIAL, the Output depends only on the input at PRESENT time.

-SEQUENTIAL, the Output depends on PRESENT and PAST input. (It has A MEMORY!)

Typology of memory:

•SRAM, static Random access memory, is a VOLATILE memory (info remain only if i have

current) based on a simple looped chain of 2 NOT gates, it need a clock.

•LATCH (SR, set and reset), constructed from a pair of cross coupled NOR gates and its

asynchronous . (Se R=S=1 non esegue)

•FLIP-FLOP, is a circuit in "synchronous" that changes state only with a clock signal.

Typologies are SR, Toggle, JK or Data/Delay.

[SHIFT REGISTERS is a cascade of flip-flop that shift info to 1 position to the right one

1→2→3, it can be in series(SISO) or parallel(PISO).]

FINITE STATE MACHINE(FSM) = is a mathematical model of computation, it is an abstract

machine that can be in exactly one of finite number of states at any given time. Change

State in response to external inputs TRANSITION(es. Tornello lock/unlock).

ARITHMETIC LOGIC UNIT(ALU) = is a combinational digital Electronic circuit that performs

arithmetic and bitwise operation on binary numbers. (es. CPU, GPU, FPU).

Input→data+code indication+status / Output→ result+status about operation

“LOGIC FAMILIES” = is a group of electronic logic gates constructed with a design, they are

bring together with a COLLECTOR. (Es. Automotive system)

OPEN-COLLECTOR can bring different families.

The controller area network(CAN) is a communication standard to defining rules for sharing

info, the BUS connects CAN with ECU.

PROCESSOR→ is a hardware device that executes instruction.

MICROPROCESSOR→ is a processor in which is contained in an IC.

MICROCONTROLLER→ contains a microprocessor with a reduced instruction set to control

product and device.

Architecture are:

•VON NEUMANN→ “SAME MEMORY" for instruction and operation, data bus and control

bus are shared.

•HARVARD→ “SEPARATE MEMORY” for inst and oper, can simultaneously do data and

instruction.

PLA→ (programmable logic array) is a device used to implement logic circuits, it has a set of

programmate and/or gates.

FPGAs→ field programmable pla, it's a pla that can be reconfigurated. Structure with matrix

of logic block, input/output block and interconnection with transistor/switch.

CAPITOLO 7# (OUTPUT STAGES)

Solid state switches, depend on the current and voltage levels. Typology:

-BJT and MOSFET (low voltage and current)

-IGBT (medium voltage 1kv and high current 300A)

-SCR (high voltage and current)

BJT

are Bipolar transistors, can be NPN or PNP silicon. It's like a switch On→Ic high and

OFF→Ic=0.

●​ 3 terminals: base(B), collector(C), emitter(E).

●​ Ib+ in, Ic+ in e Ie+ out.

●​ Large variety of current 1mA - 50A

●​ Voltage 1-100V

●​ Bf is static current ~100A

MOSFET

Are field effect transistors, can be N-type or P-Type

●​ 4 terminals: gate(G), body(B), Drain(D), source(S).

●​ Can be an Amplifier or a Switch

●​ D and B are symmetrucal

●​ 3 working region→Saturation (no Vds deep), Triode (Vds deep), Cut-off (Id=0).

Relays→are electromechanical switches, solid state relay(SSR) have instead no moving

parts and are resistant to vibration and are galvanically isolated.

“H-BRIDGE” → a DC motor can be controlled by a full bridge, it allows control over the

motor direction and allows Free Run or Braking. (Switches can “not” simultaneously closed).

Implementation with n Mosfets(low-side) and p Mosfets(high-side).

There are 4 configuration:

S1-S4, motor move R

S2-S3, motor move L

S2-S4, motor brakes

Open switch, motor coasts(free run)

“WAVEFORM GENERATION”→ Schmitt Trigger is a comparator with hysteresis used as an

oscillator.

Pulse width Modulation→ typically used to control electric engines(triangular waveform). It

has a 3 part system: ramp voltage generator, comparator and switch power device.

OFF→no voltage

ON→ all power supply

CAPITOLO 8# (ACTUATORS)

Actuator is a device that “transforms” the variations of an electrical quantity in a related

variation of a physical quantity. It translate info from a domain to another.

Typical: 1)temperature, 2)light; 3)force, displacement, motion; 4)motors; 5)acoustic.

(1)​ RESISTOR, is a simple thermal actuator, the device transforms the “power

dissipated” on it as HEAT. Imp Characteristic→ thermal resistance (K/W) and rated

power.

(2)​ LEDS, a Light Emitting Diode is a peculiar kind of diode, it's not made of Si but direct

band-gap material like GaAs. When fed with current it emits light(infrared, ultraviolet

or visible).

(3)​ SOLENOIDS, is composed by an electric coil and a “ferromagnetic core” that is

somewhat free to move with the coil(es. Electro-valves or magnetic field).

(4)​ AC MOTOR, is driven by an “AC CURRENT”, it consist of an outside STATOR having

coils supplied with ac current to produce a rotating magnetic field and an inside

ROTOR attached to the output shaft that produces the mech. rotation.

(speed→controlled by the current frequency)

It can be:

- SYNCHRONOUS, rotor=magnetic rotation

- ASYNCHRONOUS, rotor<magnetic motion (induction of Lenz's law)

DC MOTOR, work with “DC CURRENT”, in it the armature rotates while the magnetic

field created by permanent magnet.

It can be:

-BRUSHED, fixed magnet and rotary switch on the motor(COMMUTATOR), its a

rotating cylinder divided into multiple metal contact on the rotor(BRUSHES). It create

torque in 1 direction.

-BRUSHLESS, must be done by the control circuit, speed is controlled by current

magnitude through the windings.

Es: STEPPER MOTOR is a particular brushless dc motor, it divides a full rotation into

a number of equal steps. It's an Open Loop, it converts a train of input pulses into a

precisely increment in the shaft position(FIXED ANGLE).

There are two type “Wave drive”(only 1 face is active) or “Full/Half step drive”(2 or

more face active).

(5)​ LOUDSPEAKER, is an electroacoustic transducer that converts an electrical signal

to a sound. The AC signal is a