For school we are designing a boost converter with PI control.
The control part and switching works fine up to the mosfet, when testing the mosfet with a purely resistive load (approximately 200ohms VDD-Drain) the mosfet output followed exactly our gate signal (Approx 40Khz). However once i connect the actual boost circuit (150mH inductor, 470uF cap, 25Ohm load, fast recovery diode). The mosfet switching then stops following the gating signal, instead switching at a rate closer to 150Hz giving us a very large ripple, taxing our supply greatly, etc.
Does anyone have any ideas as to why this could be happening? Our gating signal is still fine even when this is happening. However it could be seen as being a bit more noisy.
We are using an optocoupler between the switching and the gate driver, however the optocoupler common reference point is the other circuits common point.
Any insight would be appreciated.
James
The control part and switching works fine up to the mosfet, when testing the mosfet with a purely resistive load (approximately 200ohms VDD-Drain) the mosfet output followed exactly our gate signal (Approx 40Khz). However once i connect the actual boost circuit (150mH inductor, 470uF cap, 25Ohm load, fast recovery diode). The mosfet switching then stops following the gating signal, instead switching at a rate closer to 150Hz giving us a very large ripple, taxing our supply greatly, etc.
Does anyone have any ideas as to why this could be happening? Our gating signal is still fine even when this is happening. However it could be seen as being a bit more noisy.
We are using an optocoupler between the switching and the gate driver, however the optocoupler common reference point is the other circuits common point.
Any insight would be appreciated.
James