SLLA618 October   2023 ATL431 , ATL431LI , TL431 , TL431LI , TLVH432

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Designing for SSR With a Shunt Reference
    1. 2.1 Setting the Output Voltage
    2. 2.2 Biasing a Shunt Reference
    3. 2.3 Designing for Transient Response
  6. 3Power Considerations
  7. 4Methodology
    1. 4.1 Shunt Reference Implementation
    2. 4.2 Accuracy Comparison
    3. 4.3 Power Consumption Comparison
    4. 4.4 Transient Response Comparison
  8. 5Results
  9. 6Summary
  10. 7References

4.3 Power Consumption Comparison

As explained in Section 3: the power dissipation of the feedback network can be calculated as the total output voltage multiplied by the total current flowing through this feedback network, which is shown in Equation 4. The currents in these equations were calculated by measuring the voltage drop across the optocoupler resistance (11 kΩ), biasing resistance (changed from device to device), and R1 (150 kΩ) and then dividing these voltage drops by their respective resistances. This is shown in Equation 6, where the reference voltage is assumed to be the internal reference of the shunt reference for simplicity.

Equation 6. Pdissipation=Vout×V1-VAnode11 kΩ+V1-VKARbias+V1-VREF150 kΩ

Using Equation 6 and the sampled data, Table 4-3 below was constructed to compare the power dissipation of the feedback network with different shunt references under each of the three load conditions.

Table 4-3 Feedback Network Power Consumption
ComponentIKA(min)Standby Mode Power Consumption20 W Load Power Consumption40 W Load Power Consumption
TL4311 mA28.29 mW24.65 mW20.82 mW
TLVH432100 µA6.74 mW5.96 mW5.12 mW
ATL43135 µA4.45 mW3.83 mW3.30 mW
TL431LI1 mA28.11 mW23.78 mW20.59 mW
ATL431LI80 µA5.31 mW4.44 mW3.87 mW

Table 4-3 confirms that a lower bias current, Ibias, reduces the power dissipation across the feedback network. This reduction also shows that the feedback network consistently dissipates more power in standby mode than when the flyback converter is at max load condition. This is due to the lower feedback current, IFB(secondary), flowing through the optocoupler diode when a load is applied to the output. The ATL431 is an excellent choice for meeting strict power consumption requirements.