• Switching controller chip

    esenes • 08/16/2018 at 13:57 • 3 comments

    Here it comes the hard point: once decided that this will be a boost-type power supply, the hard point is the selection of the PWM controller IC. In the jungle of the DC-DC controller chips, we have to consider:

    • Integrated or external switching MOSFET
    • Slope compensation
    • Soft-start capability
    • Switching frequency solution (up to 1 MHz)
    • Overcurrent detection
    • Packaging of the IC
    • Maximum ratings of voltage and current

    Since the idea is to build something new, all the usual design are not the way. This rules out the commonly used chips for nixie power supplies:

    • MC34063
    • MAX1771
    • MAX771
    • UCC3808
    • 555 timer-based solutions

    ... but makes the journey more interesting !

    So what are we looking for ? To begin:

    1. A chip by Linear Technology, in order to have a model in LTCSpice to simulate it. If you are new to LTCSpice you can take a look to the numerous tutorials, like this.
    2. A package that can be soldered by hand, so no packages without leads ... and I don't even mention the ball bonded ones
    3. Internal switching transistor or external to be seen
    4. I don't really care of the efficiency, as long as it's reasonable.

    <draft to be finished>

  • Key requirements

    esenes • 08/16/2018 at 13:07 • 0 comments

    What I want from my power supply is to be able to drive a nixie clock, so more than 4 tubes.

    So the key requirements are:

    • DC-DC boost converter
    • Vin 5 or 12 V
    • Vout around 170 V
    • Iout around 50 mA

    Now, the idea is to build a boost converter and not a flyback one. This is because for me it is more challenging the boost type and there is no need to use a transformer. In the future maybe I will design also a flyback transformer, eventually involving voltage multiplier stages.

    Some inspiration came from:

    • This project here on hackaday
    • This design based on MAX1771 
    • A very well made project on how to build the full clock, including the power supply
    • Another already available design based on MC34063
    • The great design step-by-steb explained by surfncircuits

    the idea is to take a lot of inspiration from these great guys, but building something new. So I will use a different IC from the ones that are commonly used in the examples online.