Improving Power Supply Thermal Performance.

Ideas for managing heat issues in power supply electronics:

Overview
In general the approach falls under:

1. Reduce power at load to reduce heat generation (via losses in the supply)
2. Choose an architecture with optimal heat performance
3. Choose the correct power supply topology and increase efficiency of power supply
4. Reduce power density (improve heat dissipation from the supply)
5. Increase heat flux from the device

At the Load
First thing first try to reduce the power consumption at the load. Less power drawn, less loss, less heat.

• Reduce the number of loads
• Use higher efficiency loads

Architecture
Evaluate your architecture for opportunities for improvement. For example distributing the load across multiple power supplies, or introducing dynamic scaling and power management into your design.

• change system architecture (e.g. implement a big/little cpu architecture)
• implement power saving or depowering or scaling

Topology
Choose the correct topology. Bucks are very efficient, LDOs are not. There are more exotic topologies which may be more suitable for your application.

• LDO to buck
• LDO to series buck-LDO
• zero crossing, etc

Optimize PSU Design
Once system level aspects of the design have been addressed and the correct power supply topology has been chosen it is now time for detail design. Start with the switching elements, then the bootstrap, then move to the output filter, the input filter and finally the strapping options/control.

• Choose lower loss inductor
• Choose lower loss FETs
• Optimize switching frequency and inductor combo
• Increase di/dt if possible
• If your device has a bootstrap power supply then optimize its design
• Choose lower I_q controller
• Reduce capacitor losses (e.g. use low ESR ceramic caps)
• Review power consumption on every pin and optimize
• increase the efficiency
  https://fscdn.rohm.com/en/products/databook/applinote/ic/power/switching...

Improve Thermal Performance
With an understanding of the design, efficiency and the amount of heat to be removed from the design we can now address the thermal performance of the design. The solution will depend a lot on where your heat is. The first approach is (if possible) to reduce the power density (Watt/Liter) of the design. When this becomes impossible then choose components with better heat dissipation (and therefore lower T_rise). When that fails forcibly remove heat from the design.

• Use more components (e.g. parallel inductors or FETs)
• Use more power supplies in your design (e.g. ORing)
• Increase the spacing between components
• Improve passive mechanisms of heat removal (e.g. heat vias, copper, etc)
• Use larger current devices
• Use larger package devices
• Increase heat removal (e.g. air flow)
• Add heatsink / Increase size of heatsink