This would likely go better if you post a drawing of your H bridge circuit. Yes, it can be done using discreet components rather than using a uC. Since you mentioned ADC that sort of implies using a uC. You could use a triangle wave generator feeding a comparator and vary the ref voltage to the comparator (analog voltage in) to control the PWM out. However, you make no mention of what the analog voltage(s) will be? Therefore the replies are generic in nature. What exactly do you want to do and what do you already have?
Ron