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

3.1.2 DCR of the Transformer

Another important transformer parameter is the DC resistance of the primary and secondary sides. It can be used to estimate the copper loss in the winding. DCR is obtained by directly measuring two taps with the other side open (without any load).

For step-up transformer 1, the DCR is as listed in Table 3-4.

Table 3-4 DCR for Peavey® Step-Up Transformer
SideTapsDCR (Ω)
Primary (common tap: tap 1)1,20.143
1,30.154
1,40.18
1,50.26
Secondary (common tap: tap A)A,B0.42
A,C0.69

For step-up transformer 2, the DCR is as listed in Table 3-5.

Table 3-5 DCR for EDCOR® Step-Up Transformer
SideTapsDCR (Ω)
Primary (common tap: Wht)Wht, 4 Ω0.2
Wht, 8 Ω0.36
Primary (common tap: Blk)Blk, 70 V0.53
Blk, 100 V0.96

For step down transformer, DCR is as listed in Table 3-6.

Table 3-6 DCR for Peavey® Step-Down Transformer
SideTapsDCR (Ω)
Primary (common tap: PRI Blk)PRI Blk, 10 W27.7
PRI Blk, 5 W54.4
PRI Blk, 2.5 W87.7
PRI Blk, 1.25 W141.2
PRI Blk, 0.62 W221.2
Secondary (common tap: SEC Blk)SEC Blk 4 Ω0.54
SEC Blk 8 Ω0.72