hi
I have a problem with a design that generates 205v at 30ma. I am using a MC33025 in a voltage mode push pull configuration clocked at 50khz. My problem is that the transformer is clicking during power up only and I assume that this is because its going into saturation, am I correct? my transformer is primary winding 3 and sec 40 winding, on a 3c90 bobbin. the supply is 24v nominal to get 205v output. all is ok once up( no clicking). note the ramp signal is controlled and I have a softstart 10Uf cap. It takes a few seconds +6 to reach max voltage
how do I avoid this clicking? would increasing my turns help say 6:80 or 12:160?
any help please
Regards
Ross
I have a problem with a design that generates 205v at 30ma. I am using a MC33025 in a voltage mode push pull configuration clocked at 50khz. My problem is that the transformer is clicking during power up only and I assume that this is because its going into saturation, am I correct? my transformer is primary winding 3 and sec 40 winding, on a 3c90 bobbin. the supply is 24v nominal to get 205v output. all is ok once up( no clicking). note the ramp signal is controlled and I have a softstart 10Uf cap. It takes a few seconds +6 to reach max voltage
how do I avoid this clicking? would increasing my turns help say 6:80 or 12:160?
any help please
Regards
Ross
I'm doing an MC33025-based PSU and stumbled across this in a websearch. I realize this thread is a bit old, but......did you ever receive a suitable response?
Couple of points:
1. MOSFET-based circuit: Assuming it IS, 24V drive may be over-driving them, since most MOSFETs have Vgs(max) of ~20V.
2. 50kHz: Clock- or switching- freq? Not knowing the detailed magnetic properties of the 3C90 material, I would ask if a 3T+3T primary too few turns?
Assuming a 25kHz switching frequency, you might consider raising the primary windings to 6T+6T.
Assuming that your xfmr is saturating at start-up, either- or both of these could be the cause.
Couple of points:
1. MOSFET-based circuit: Assuming it IS, 24V drive may be over-driving them, since most MOSFETs have Vgs(max) of ~20V.
2. 50kHz: Clock- or switching- freq? Not knowing the detailed magnetic properties of the 3C90 material, I would ask if a 3T+3T primary too few turns?
Assuming a 25kHz switching frequency, you might consider raising the primary windings to 6T+6T.
Assuming that your xfmr is saturating at start-up, either- or both of these could be the cause.