If your MCU's PWM can be gated by an on-chip comparator, you can implement the control loop of a boost converter in hardware inside your MCU, only needing an external inductor, N-MOSFET, Schottky diode, smoothing cap and a potential divider for feedback. The feedback disables the PWM on a cycle by cycle basis if the output voltage is over the threshold thus regulating it.
Set the on time so the inductor doesn't saturate starting fron zero flux and the off time slightly greater than the on time, to avoid flux walking during startup. If you need more output current, you can run a software control loop to reduce the off time in proportion to the output voltage.
Excessive ripple is likely to cause display flicker so you'll probably need a LC filter or a capacitance multiplier after the point the feedback divider taps from.