Car Audio Amplifier Midterm Presentation 28 February 2005 Team Members Car Audio Amp Group Stephan Sykes Team Leader Power Supply Dwayne Custer Amplifier Jacob Fulper Documentation Dr. Ray Winton Faculty Advisor Darius Boyce Input/Output Presentation Overview I. II. Introduction Amplifier A. B. Selection Functionality On/Off Switch Output Relay Jacob Fulper Dwayne Custer Darius Boyce Stephan Sykes III. Input/Output A. B. IV. V. Power Supply Conclusion I. Introduction Project Goal The car audio amplifier will allow music enthusiasts to listen to their MP3 player, or other headphone audio device, through their car speakers. I. Introduction 1. Advantages Over Competition Size – This device will be much smaller than most existing car audio amplifiers. Width ≤ 4”, Length ≤ 6”, Thickness ≤ 2” Cost – This device will cost less than most existing car audio amplifiers. Projected production cost: ≤ $15 Projected retail price: ≤ $45 Sound Quality – This device will provide the listener with higher quality of sound than its cheaper competitors, which include the FM transmitter and the cassette adapter. 2. 3. II. Amplifier Car Battery Portable Audio Player Power Supply On/Off Relay Amplifier Car Stereo Block Diagram Speakers II. Amplifier – Selection Class A B AB D Advantages Very low distortion Much more efficient than A Low distortion, good efficiency Very high efficiency Disadvantages Very inefficient Very much distortion Requires more circuit elements Small bandwidth II. Amplifier – Functionality Input Input Buffer/Filter Voltage Gain Element Current Gain Element High Level Block Diagram for the Amplifier II. Amplifier – Functionality Input Buffer/Filter – Maximally Flat, Audio Range (20Hz-22kHz) II. Amplifier – Functionality Voltage/Current Gain Elements Power = Voltage x Current Output Voltage Gain of 5 Class AB final stage Output current gain = 560k Vin V+ V+ RL V- V- II. Amplifier – Functionality Voltage and Current Gain Elements Final Output III. Input/Output Car Battery Portable Audio Player Power Supply On/Off Relay Amplifier Car Stereo Block Diagram Speakers III. Input/Output – On/Off The amplifier will only be on when the audio player is plugged into the jack. Portable Audio Player “ON” “OFF” On/Off 5V Switch (Jack) 0V 5V 0V Power Supply ±7V 0V Logic Audio Signal In Amplifier Audio Signal Out III. Input/Output – Output Relay To prevent damage, the car stereo will be disconnected from the speakers when Car Stereo the amplifier is on. 5V 0V Relay Audio Signal Out Amplifier Signal Car Stereo Out Out 5V 0V Logic 5V 0V Power Supply Speaker Amplifier “ON” Amplifier “OFF” ±7V 0V Amplifier Audio Signal In IV. Power Supply Car Battery Portable Audio Player Power Supply On/Off Relay Amplifier Car Stereo Block Diagram Speakers IV. Power Supply Every amplifier circuit requires an independent power supply to function. The following criteria define the requirements of the power supply: 2Ω 2Ω 2Ω 2Ω 12W 12W 12W 12W PL=4 x 12W=48W 0.5Ω 48W RL=2||2||2||2=0.5Ω VS(opt) 2RL PL 2 0.5 48 6.92V 7V IV. Power Supply Power supply requirements (continued): It should be noted that the amplifier needs voltage rails of ±VS(opt), which is ±7V. The actual efficiency of the amplifier will be greater than 70%, but… …the power supply will be designed to handle a worst case efficiency, η, of 50%. PS=PL/ η=48/0.5=96W PD=PS-PL=96-48=48W (Worst Case) ISmax=PS/VS(opt)=96/6.92=13.9A≈14A V. Portable Audio Player Conclusion – Recap Car Stereo On/Off Switch (Jack) Logic Relay Power Supply Amplifier Car Battery Speakers Acknowledgments Dr. Ray Winton Dr. James Harden Mr. Nishant Chandra Mr. Charles Simmons (Raytheon) Crutchfield New Media, LLC Any Questions?