bruce mayer, pe registered electrical & mechanical engineer bmayer@chabotcollege
DESCRIPTION
Engineering 43. Chp 2 Tutorial Problem 2-24 Solution. Bruce Mayer, PE Registered Electrical & Mechanical Engineer [email protected]. Amplifier Driving Speaker. Consider an Amplifier Circuit connected to a Speaker. Speaker a.k.a. the “LOAD”. Driving Circuit a.k.a. the “SOURCE”. - PowerPoint PPT PresentationTRANSCRIPT
[email protected] • ENGR-25_Prob_2-24_Solution.ppt1
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
Bruce Mayer, PERegistered Electrical & Mechanical Engineer
Engineering 43
Chp 2 Chp 2 TutorialTutorial
Problem 2-24Problem 2-24SolutionSolution
[email protected] • ENGR-25_Prob_2-24_Solution.ppt2
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
Amplifier Driving SpeakerAmplifier Driving Speaker Consider an Amplifier Circuit
connected to a Speaker
DrivingCircuita.k.a. the
“SOURCE”
Speakera.k.a. the
“LOAD”
[email protected] • ENGR-25_Prob_2-24_Solution.ppt3
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
Circuit SimplificationCircuit Simplification Thévenin’s Equivalent Circuit Theorem (c.f. ENGR43)
Allows Tremendous Simplification of the Amp Ckt
Thevenin +
RS
VS
[email protected] • ENGR-25_Prob_2-24_Solution.ppt4
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
Maximum Power TransferMaximum Power Transfer The Simplest Model
for a Speaker is to Consider it as a RESISTOR only
Since the “Load” Does the “Work” We Would like to Transfer the Maximum Amount of Power from the “Source” to the “Load”
BASIC MODEL FOR THE ANALYSIS OF POWER TRANSFER
+
─
RS
VS SPEAKERMODEL
RL
Anything Less Results in Lost Energy in the Driving Ckt in the form of Heat
[email protected] • ENGR-25_Prob_2-24_Solution.ppt5
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
The Final Ckt ModelThe Final Ckt Model
Source Load
Driving Circuit The Speaker
[email protected] • ENGR-25_Prob_2-24_Solution.ppt6
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
Electrical Power PhysicsElectrical Power Physics For ANY Electrical
Device with a:• Potential, V, across it
• A current, I, thru it
V
I
Then the Power Used by the Device:
Now OHM’s Law Relates the Voltage-across and Current-Thru a resistor
VIP
RIV
[email protected] • ENGR-25_Prob_2-24_Solution.ppt7
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
Voltage DivisionVoltage Division Recall the Reduced
Ckt ModelSource Load
This SINGLE LOOP Ckt effectively divides VS across RS and RL
Analysis of this “Voltage Divider” Ckt produces a Relationship between VS & VL
LS
LSL RR
RVV
[email protected] • ENGR-25_Prob_2-24_Solution.ppt8
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
Summary to This PointSummary to This Point What we KNOW
• By Thévenin Analysis of the Driving Ckt we determined VS & RS
Note that VS & RS are FIXED and beyond our Control as Speaker Designers
The Speaker Designer CAN, however control the Load Resistance, RL
Thus Our Goal
Find RL such the Driving Ckt Operates
at the Highest Efficiency; i.e., we seek RL that will
MAXIMIZE Driver→Load
Power Transfer
[email protected] • ENGR-25_Prob_2-24_Solution.ppt9
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
Analytical Game PlanAnalytical Game Plan
Goal Find RL to Maximize PL(RL)
From the Physics we Know
32
1
LS
LSL
LLL
LLL
RR
RVV
IRV
IVP
[email protected] • ENGR-25_Prob_2-24_Solution.ppt10
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
The MATLAB ProblemThe MATLAB ProblemSource Load
RS = 10Ω, 15Ω, 20Ω, 25Ω
RL = 10Ω, 15Ω, 20Ω, 25Ω, 30Ω
And 2
2 S
LS
LL V
RR
RP
Define Transfer Ratio, r
2LS
L
RR
Rr
Then 2SL rVP
So to Maximize PL need to Maximize r
[email protected] • ENGR-25_Prob_2-24_Solution.ppt11
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
MATLAB Game PlanMATLAB Game Plan
Concept Test ALL possible Resistor Combinations then Check for Best
Because we have a small number of allowable values for RS and RL, the most direct way to choose RL is to compute the values of r for each combination of RS and RL. • Since there are four possible values of RS
and five values of RL, there are 4(5) = 20 combinations.
[email protected] • ENGR-25_Prob_2-24_Solution.ppt12
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
MATLAB Plan (2)MATLAB Plan (2)
We can use an array operation in MATLAB to compute r for each of these combinations by defining two 5 × 4 2D-Arrays R_L and R_S. • The five rows of R_L contain the five
values of RL, and its four columns are identical.
• The four columns of R_S contain the four values of RS, and its five rows are identical.
[email protected] • ENGR-25_Prob_2-24_Solution.ppt13
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
MATLAB Plan (3)MATLAB Plan (3)
The Arrays we Need
30303030
25252525
20202020
15151515
10101010
LR
25201510
25201510
25201510
25201510
25201510
SR
• These Arrays MUST have the same size so that we can perform element-by- element operations with them.
2LS
L
RR
Rr
[email protected] • ENGR-25_Prob_2-24_Solution.ppt14
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
Th
e MA
TL
AB
Co
de
Th
e MA
TL
AB
Co
de
% Bruce Mayer, PE% ENGR22 * 20Jan07 * Rev. 13Sep08% Prob 2.24 * file Demo_Prob2_24_0809.m%% Since all COLUMNS in RL are the same, Define one Col and Replicate in Row Vector% Define RL cola = [10;15;20;25;30];% Make Array R_L by using a in 4-element Row VectorR_L = [a,a,a,a]%% Since all ROWS in RS are the same, Define one Row and Replicate in Col Vector% Define RS rowb = [10,15,20,25];% Make Array R_S by using a in 5-element Col VectorR_S=[b;b;b;b;b]%% Use Element-by-Element Operations to Calc r%% First Sum RS & RL for the 20 combosRsum = R_S+R_L%% Now sq the 20 sumsRsumSq = Rsum.^2 % need "dot" as this is element-by-element%% Finally Divide RL by SQd sumsr = R_L./RsumSq%% Use the max(A) command to find the max value in each COL, and the ROW in in Which the max Values Occurs[max_ratio, row] = max(r)
[email protected] • ENGR-25_Prob_2-24_Solution.ppt15
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
The .m-File OutPutThe .m-File OutPutR_L =
10 10 10 10 15 15 15 15 20 20 20 20 25 25 25 25 30 30 30 30
R_S =
10 15 20 25 10 15 20 25 10 15 20 25 10 15 20 25 10 15 20 25
Rsum =
20 25 30 35 25 30 35 40 30 35 40 45 35 40 45 50 40 45 50 55
r =
0.0250 0.0160 0.0111 0.0082 0.0240 0.0167 0.0122 0.0094 0.0222 0.0163 0.0125 0.0099 0.0204 0.0156 0.0123 0.0100 0.0187 0.0148 0.0120 0.0099
max_ratio =
0.0250 0.0167 0.0125 0.0100
row =
1 2 3 4
RS = 10 RS = 15 RS = 20 RS = 25RL =
10RL = 15RL = 20RL = 25RL = 30
[email protected] • ENGR-25_Prob_2-24_Solution.ppt16
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
[email protected] • ENGR-25_Prob_2-24_Solution.ppt17
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
[email protected] • ENGR-25_Prob_2-24_Solution.ppt18
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
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[email protected] • ENGR-25_Prob_2-24_Solution.ppt19
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods
[email protected] • ENGR-25_Prob_2-24_Solution.ppt20
Bruce Mayer, PE ENGR/MTH/PHYS25: Computational Methods