3 options for acdc module power supply to realize bias power in application

Bias power is very important in the power supply. Inside the power supply, a bias power supply is required to power up the IC. Outside the power supply, a bias power supply may be required to power up the MCU and/or other local power supplies in the system. Many low-voltage ICs (rated voltages less than 100Vdc) integrate the bias power supply into the IC. However, foracdc module power supplyIn terms of things will become more complicated, because now need to deal with much higher input voltage.

There are several design methods for bias power supplies. I will introduce 3 options for implementing bias power in acdc applications: linear, buck converter or flyback converter.

1. Linear bias power supply

The BJT linear circuit can provide a simple bias power solution with at least the number of components. However, the main disadvantage of using this program is low efficiency.

2. Flyback bias power supply

Flyback converter bias power (PMP8764 in Figure 2) is a commonly used bias power solution, which not only provides safety isolation, but also provides multiple bias outputs.

Due to the use of primary-side voltage regulation (PSR) technology, the optocoupler and compensation circuit can be removed from the flyback bias power supply while maintaining a 5% output voltage regulation.

3. Step-down bias power supply

In certain applications such as electronic metering, isolation is not required, and custom transformers in flyback converters are too expensive for cost-sensitive markets. In this case, a buck converter is a better option to implement a low-cost bias power solution because of the use of standard inductors. In addition, the use of PSR controller (UCC28700 series) can also achieve fast load transient response, because the PSR controller has cycle-by-cycle voltage sensing characteristics.

For applications that require a low output voltage (9V or lower) bias power supply, the p-channel MOSFET buck converter is a perfect alternative to flyback bias power.