How to get 1 to 17V out of 5V

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pkaras

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I am looking for a simple solution how to get 1V, 3V, 5V, 7V, 9V, 11V, 13V, 15V and 17V outputs supplying 5V. The idea is to use a microcontroller which would switch between these ranges. Max current will be only 40mA. There is no need in great accuracy - it could be 0.5 or 1.5V when 1V is expected.

I was thinking about using two DC-DC converters, but that would make final solution quite complicated.
 

You can use a single DC/DC boost converter with a digital resistor to adjust the output voltage.
 

Do you know any digital resistors that are rated at 40+mA?
 

Besides a voltage boost function, you also need a means to reduce the voltage which isn't possible in basic boost topology. Considering the low current requirement, a separate linear regulator stage seems more appropriate than a buck/boost topology.

Variable boost converters for low current can be found e.g. in flash/processor programming adaptors like PICkit. They are often using processor generated pwm and voltage control through ADC measurement, minimal hardware effort with a bit of software, if a processor is already in use.
 

shaiko, I have looked at DigiKey before asking. It does not provide a column for Watts. I looked though several datasheets, but they specify mA, not mW. For example: https://ww1.microchip.com/downloads/en/DeviceDoc/22147a.pdf

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FvM, I was considering using two DC-DC converters - one step-up and one step-down. That's why I said it was complicated.
I have also looked for Sepic, which would be a perfect fit in my case, but could not find one that fits my requirements.

I will look at PICkit schematics.
 

SEPIC or transformer flyback are ways to control the output range with a single pwm switch. You need
- a switch transistor
- coupled inductors
- a diode and filter capacitor
- an additional capacitor in case of SEPIC
PWM generation can be done by the processor or a switch-mode controller.
 

FvM, from your answer it looks like an easy job to do, but when I look into SEPIC related literature it is quite complex. I even found one documents where authors admit that: "Unfortunately, the SEPIC topology is difficult to understand".

Could you help me choosing those components you have listed?
 

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