Switching between two different power supplies on a PCB can be achieved using various methods, depending on the requirements and constraints of your design. Here are a few common approaches:
- Diode ORing: Use diodes to connect the outputs of the two power supplies together. This allows the higher voltage supply to power the circuit while the lower voltage supply is inactive. Diode ORing ensures power supply redundancy but introduces a voltage drop across the diodes.
- Power Management ICs: Utilize power management ICs that are designed for power source selection. These ICs often feature low dropout voltage regulators and can automatically switch between power sources based on their availability and quality.
- FET-Based Switching: Employ MOSFETs or other types of FETs as switches to selectively connect the desired power supply to the circuit. The FETs can be controlled by logic signals or microcontroller pins.
- Relays or Solid-State Relays (SSRs): Use relays or SSRs to physically or electronically switch between the two power sources. Relays are suitable for lower-frequency applications, while SSRs can be used for high-frequency switching.
- Automatic Switchover Circuits: Design a circuit that monitors the voltage levels of both power supplies and automatically switches to the one with the higher voltage. This approach is useful when you have a primary and backup power supply.
- Manual Switches: Include a manual switch that allows users to manually select which power supply is active. This approach is simple but relies on user intervention.
- Priority-Based Switching: Implement a circuit that intelligently selects the power source based on predefined priorities or conditions. This can be useful for complex systems with multiple power sources.
- Ideal Diode Controllers: Ideal diode controllers are ICs that mimic the behavior of diodes but with lower voltage drops. They can be used to switch between power sources while minimizing the voltage drop.
Remember to consider factors like voltage compatibility, current handling capability, voltage transient protection, and power supply sequencing when implementing power source switching on your PCB. Select the method that best suits your design’s requirements and constraints. It’s also important to ensure that switching between power sources is seamless and reliable to prevent disruptions in your circuit’s operation.