Hi All,
Having an almost philosophical thought regarding poor thermal dissipation of surface mounted Silicon carbide diodes with thermal pads.
I tested my resonant converter and expected >90% efficiency but only get around 70% at full-load. I put a FLIR camera onto the board and noticed that the Silicon carbide diodes heat up to around 58 degrees celcius, with 25 degrees ambient temperature. The only other thing that gets remotely warm is the resonant inductors that are from Coilcraft, so this led me to believe that the majority of the power is being lost in the diodes, due to poor thermal resistance or how I layed out the thermal structure of the board.
My question is, does having high thermal resistance due to poor layout increase power dissipation? I would think it would, but it could be that the diodes are dissipating the exact same amount of power, but because the thermal resistance is higher, the diodes are getting hotter with the same level of actual power dissipation. To illustrate, let's say that a diode dissipates 20W of power.
Thermal resistance = 1.5C/W - would heat the device up 30 degrees C.
Thermal resistance = 3C/W - would heat the device up 60 degrees C
Even though both devices dissipate 20W, one gets much hotter because of the increase thermal impedance from the case to the junction and ambient. In this case, the efficiency of the converter is not affected at all by the increased thermal impedance. But I expect this is not the case and instead the poor connection I have made with the thermal layout, has caused the majority of the dissipation, because I cannot for the life of me see where else the power could be lost within the circuit. The inverter switches are below 30 degrees, and no other component on the board really gets hotter than 35 degrees Celcius. Diodes approach 60 degrees.
TIA for any answers!
Having an almost philosophical thought regarding poor thermal dissipation of surface mounted Silicon carbide diodes with thermal pads.
I tested my resonant converter and expected >90% efficiency but only get around 70% at full-load. I put a FLIR camera onto the board and noticed that the Silicon carbide diodes heat up to around 58 degrees celcius, with 25 degrees ambient temperature. The only other thing that gets remotely warm is the resonant inductors that are from Coilcraft, so this led me to believe that the majority of the power is being lost in the diodes, due to poor thermal resistance or how I layed out the thermal structure of the board.
My question is, does having high thermal resistance due to poor layout increase power dissipation? I would think it would, but it could be that the diodes are dissipating the exact same amount of power, but because the thermal resistance is higher, the diodes are getting hotter with the same level of actual power dissipation. To illustrate, let's say that a diode dissipates 20W of power.
Thermal resistance = 1.5C/W - would heat the device up 30 degrees C.
Thermal resistance = 3C/W - would heat the device up 60 degrees C
Even though both devices dissipate 20W, one gets much hotter because of the increase thermal impedance from the case to the junction and ambient. In this case, the efficiency of the converter is not affected at all by the increased thermal impedance. But I expect this is not the case and instead the poor connection I have made with the thermal layout, has caused the majority of the dissipation, because I cannot for the life of me see where else the power could be lost within the circuit. The inverter switches are below 30 degrees, and no other component on the board really gets hotter than 35 degrees Celcius. Diodes approach 60 degrees.
TIA for any answers!