SLAA898 September   2022 TAS3251 , TPA3255

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 Power Amplifiers
    2. 1.2 Discrete Power Amplifier Implementation
    3. 1.3 Class-D Amplifier Implementation
    4. 1.4 Advantage of a Class-D Implementation
  4. 2Background
    1. 2.1 Why Use Constant Voltage Audio Systems
    2. 2.2 Basic Principle of Constant Voltage Systems
    3. 2.3 Power Loss in Transformer
    4. 2.4 Auto-Transformer
  5. 3System Test (Based on TPA3255)
    1. 3.1 Transformer Characteristics
      1. 3.1.1 Turns Ratio and Resistance Match
      2. 3.1.2 DCR of the Transformer
    2. 3.2 System Build-Up
    3. 3.3 System Test
  6. 4Efficiency Analysis and Optimization
    1. 4.1 Efficiency of Three Parts
      1. 4.1.1 Efficiency for TPA3255
      2. 4.1.2 Efficiency for Step-Up Transformer
      3. 4.1.3 Efficiency for Step-Down Transformer 330-040
    2. 4.2 Improvements on System Efficiency
      1. 4.2.1 Improve Resistance Matching
      2. 4.2.2 Apply a Transformer With Less Power Loss
  7. 5Considerations on Building a Constant Voltage System
    1. 5.1 Transformer Saturation
    2. 5.2 Low DCR
    3. 5.3 Resistance Matching

1.2 Discrete Power Amplifier Implementation

Figure 1-1 shows a traditional, discrete implementation for the power amplifier in a fire safety application.

GUID-16A65E65-614B-49A2-8D73-3D760FB51A4A-low.gifFigure 1-1 Power Amplifier Discrete Implementation

This implementation scheme requires many different components to achieve the waveform amplification. The transceiver at the beginning of the signal chain enables communication between the power amplifier board and a central control unit. The digital processing block then decides which audio signal to send through the system. Then, the audio CODEC, along with various operation amplifiers, switches, and a triangle-wave generator, condition the audio signal to be a usable input for the FET driver. The FET driver then drives the FETs, which creates the final audio signal. That signal is then sent through the transformer and to the notification appliance circuits (NACs).

This implementation scheme requires many different components to achieve the waveform amplification. The transceiver at the beginning of the signal chain enables communication between the power amplifier board and a central control unit. The digital processing block then uses the appropriate audio signal to send through the system. Then, the audio CODEC, along with various operation amplifiers, switches, and a triangle wave generator, condition the audio signal to be a usable input for the FET driver. The FET driver then drives the FETs, creating the final audio signal. That signal is then sent through the transformer and to the NACs.