How to generate 4-channels phase-shifted PWM with 150kHz frequency
So I came up with solutions myself.

Instead of atmega88pa I'm going to use AT90PWM3B.
It has 3 'Power Stage Controllers', each implemented as double 12bit high frequency PWM generator, powered by 64MHz PLL.

With 150kHz frequency I'm able to get ~450 steps.

All power stages can be synchronized, each channel has S(et) and R(eset) value.