I have built control logic for an symmetrical flyback converter based on IC SG2525. This IC has 2 outputs to control external BUZ11, one for each primary winding. From output of transformer positive side (+40V) i have isolated feedback (voltage to freq. via transformer to freq. to voltage) to the control electronics to get good regulation but I have no feedback from negative side (-40V) and no control of negative voltage. SG2525 has only one input to control duty cycle of 2 outputs. Is there any simple way to also keep track of the negative? //Peter