Build Log – DIY CAR PC / Car entertainment system – Power Supply.

Since this will be a completely homemade solution, while searching for different options available for powering up the cubieboard and the amplifier, I have considered following criteria.

  • The Power supply should be able to deliver at least 150W.
  • As Minimum components as possible (to save space)
  • Topology with minimum loss of power, more density and relaxed transformer rules.
  • Since the output voltage needed is between 15-16V, there is no need of buck regulation.

I chose the push-pull  Sepic topology for this SMPS. Alongwith various sources on the internet, Information posted on This blog was very helpful in the design process. I used the famous SMPS controller IC UC3843. This IC has totem-pole output and is capable of driving the gates of power mosfets directly. SEPIC topology results in lesser power losses and good efficiency. Apart from that, it also accepts the wide range of input voltage while keeping the output voltage constant and also the isolation between positive rails of input and output unlike boost converter. So when i switch off UC3843, there is no voltage seen at the output.

I am preparing the schematic diagram, as i designed the PCB first. The power supply is working very good but the maximum limits are yet to be tested using CAR battery as a source. Two power supplies are required. One for powering the amplifier and other for LCD and Rear CAM. using separate supply for LCD and CAM will ensure that they keep running even when the battery voltage drops to 9V. The UC3843 chips have their positive rails taken out to power them through relay, in order to contain the power consumption during the “OFF” mode.


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