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

1.4 Advantage of a Class-D Implementation

When comparing the integrated Class-D implementation to the discrete implementation, there are multiple advantages to consider. The first, and most evident advantage when observing Figure 1-1 and Figure 1-2, is the simplification of the circuit design. By using an integrated Class-D amplifier with digital input, it can receive the signal input directly from a microcontroller. Thus, the integrated Class-D amplifier, in this case, removes the need for signal conditioning circuitry. Second, because the integrated Class-D amplifier simplifies the circuit by replacing multiple components, it reduces the overall bill of material (BOM) cost. By choosing representative parts for each block replaced by the integrated Class-D amplifier, the estimated 1-kU cost of the replaced components is approximately double that of the integrated Class-D amplifier. This evaluation also includes the necessary external passive components for the implementation of the Class-D amplifier. Third, implementing a power amplifier using the integrated Class-D amplifier over the discrete implementation introduces board-size savings. Doing a layout analysis of the discrete components replaced by the integrated Class-D amplifier shows that they occupy approximately eight square inches (not including heat sinks) in total. The integrated Class-D amplifier, specifically the TAS3251 device for this analysis, requires only approximately three square inches. The size savings offered by the integrated Class-D amplifier can help greatly reduce system size. Finally, TI’s Class-D amplifiers offer high performance, and further functionality improvements, over the typical discrete implementation. The TAS3251 device has integrated protection and error reporting on-chip that enables real-time monitoring for overvoltage, undervoltage, and clipping, while also protecting against events like short circuits. Additionally, the TAS3251 device has greater than 108 dB SNR, and less that 0.01% total harmonic distortion (THD), so it delivers strong audio performance at the output of the amplifier.