Group 2: High power audio bass amplifier - PowerPoint PPT Presentation

1 / 28
About This Presentation
Title:

Group 2: High power audio bass amplifier

Description:

Group 2: High power audio bass amplifier Nithin Cherian Steve Lapen James Sears ECE 345 Spring 2002 Objectives Use switching power processing techniques to achieve ... – PowerPoint PPT presentation

Number of Views:159
Avg rating:3.0/5.0
Slides: 29
Provided by: JimWol
Category:
Tags: amplifier | audio | bass | group | high | power

less

Transcript and Presenter's Notes

Title: Group 2: High power audio bass amplifier


1
Group 2 High power audio bass amplifier
  • Nithin Cherian
  • Steve Lapen
  • James Sears
  • ECE 345
  • Spring 2002

2
Objectives
  • Use switching power processing techniques to
    achieve
  • Product Features
  • Frequency response 30Hz - 1,000Hz
  • Efficiency 50 or better (at normal listening
    volume)
  • Peak instantaneous output power 1000W (into 2?
    load)
  • Maximum time-average output power 500W (into 2?
    load)
  • Product Benefits
  • Efficiency superior to that of a linear amplifier
  • Reduced heat production
  • Minimal distortion of audio signal

3
Preamplifier basics
  • Amplify signal to usable level
  • Add Controls for User Interface
  • Filter signal frequencies that are too high for
    proper amplification
  • Limit signal to an acceptable level for PWM
    generation

4
Preamp Components
  • Voltage Buffer
  • Inverting Gain Stage
  • Overall LPF to limit output frequencies to 20
    1000HZ
  • 3 Band EQ
  • Inverting Summer

5
(No Transcript)
6
EQ
  • 3 Bands
  • LO 0 250Hz
  • MID 250 750Hz
  • HI 750 1250Hz

7
EQ Filter Implementation
  • Utilized LP, BP, HP Butterworth Filter Model
  • 2nd Order Filters using Sallen-Key Topology

8
Preamp Hi Band
  • HPF response

9
Preamp Lo Band
  • LPF response

10
Preamp Mid Band
  • BPF response

11
Preamp Design Problems
  • Ground Noise
  • Filter Resonance
  • Precise Components for prototyping
  • Output Voltage amplitude
  • Integration with PWM circuit

12
PWM Generation
  • Triangle wave generation
  • Compare triangle with incoming signal
  • Duty cycle varies with input signal

13
PWM Generation (component selection)
  • Function Generation
  • MAXIM MAX038
  • Wide range of stable oscillation (0.1Hz 20MHz)
  • Output symmetrical about ground
  • Comparator
  • MAXIM MAX913
  • Stable with slow moving inputs
  • Low power consumption (6mA _at_ 5V)
  • Ultra fast propagation delay (10ns)
  • Dual Supply Operation

14
PWM Generation results
  • Noise coupling through supplies
  • Supply decoupling
  • Attention to layout
  • Short wires
  • Short component leads
  • Stable operation

15
PWM Generation results (contd)
16
Dead-time
Prevents both FETs from being on
simultaneously Two general approaches Inverter
propagation delay Asymmetric RC delay
17
Power Bridge
  • Half bridge topology consists of two MOSFETs
    operated as switches
  • The purpose of the half bridge is to alternately
    connect the load to positive and negative DC
    voltage such that the output is AC.

18
Choosing Power Components
  • FETs
  • - Blocking voltage
  • - Current capacity
  • - On-state drain-source resistance
  • - total gate charge

19
Choosing Power Components
  • Diodes
  • -Ultrafast reverse recovery necessary to avoid
    FET damage
  • Gate resistors
  • -Proper resistance is required to avoid
    deleterious ringing.

20
Output Filter
  • MATLAB design for inductance and capacitance
    values
  • Saturation constraints
  • Good agreement between idealized design and
    reality

21
Problems Addressed
  • Noise coupling between high-power and low-power
    ends of circuit
  • Steps taken
  • Numerous layout revisions
  • Metal shielding
  • Increased dead time
  • RC filters on optocouplers
  • Reverse parallel FETs
  • Gate resistance adjustments

22
Describe project build and functional tests
  • Protoboard test
  • Illustrated the importance of layout
  • Permanent construction
  • Test functionality
  • Lowered voltage / smaller load

23
Testing
  • Efficiency
  • Output Power
  • Frequency Response
  • Gain linearity

24
Efficiency
  • Power out / Power in

25
Max Output Power
Average power 140 W Peak instantaneous power
280 W Load current 11.3 A amplitude
26
Frequency Response
  • Measures output level vs. frequency
  • System is flat (within /- 3dB) over the range
    20Hz 5kHz

27
Gain linearity
  • Measures the increase in output level for a
    corresponding increase in input level

28
Future Improvements
  • Add proportional integral controller to eliminate
    DC offset.
  • Pinpoint cause of unsymmetrical gate drive glitch
  • Consolidate entire circuit and enclose in housing
Write a Comment
User Comments (0)
About PowerShow.com