I'm designing a circuit using a MOSFET driver (On Semi FL5150) that draws its power from the 230v mains.
The datasheet shows a diode/resistor circuit to provide power. As this entails significant power dissipation I'm looking to use a capacitive power supply instead. I'm aware of the limitations and risks that this incurs and have these covered off as part of the product design.
The MOSFET driver internally has a zener diode that clamps at 17v. The circuit design requires a max current of 15mA so I have sized the power capacitor to provide that.
Part of the driver design is that the source of the MOSFET connects to the GND of the driver to complete the gate circuit. So the GND will also be at (or a diode drop less than) the supply voltage.
This requires that the capacitive power supply draws its power only in the half cycle where Neutral is more positive than Line so a bridge rectifier is not possible and a simple 1N4007 half wave design is used.
I have drawn up a schematic to model this. The areas I'm looking to check is the placement of the inrush limiting resistor. The way it is placed it will slow the charging current into the power capacitor, but will also affect the charging of the MOSFET gate thus slowing its switch on. I'm guessing not enough to matter.
Any feedback and comments are welcome. In particular have I placed the components in the appropriate place ?
Thanks
The datasheet shows a diode/resistor circuit to provide power. As this entails significant power dissipation I'm looking to use a capacitive power supply instead. I'm aware of the limitations and risks that this incurs and have these covered off as part of the product design.
The MOSFET driver internally has a zener diode that clamps at 17v. The circuit design requires a max current of 15mA so I have sized the power capacitor to provide that.
Part of the driver design is that the source of the MOSFET connects to the GND of the driver to complete the gate circuit. So the GND will also be at (or a diode drop less than) the supply voltage.
This requires that the capacitive power supply draws its power only in the half cycle where Neutral is more positive than Line so a bridge rectifier is not possible and a simple 1N4007 half wave design is used.
I have drawn up a schematic to model this. The areas I'm looking to check is the placement of the inrush limiting resistor. The way it is placed it will slow the charging current into the power capacitor, but will also affect the charging of the MOSFET gate thus slowing its switch on. I'm guessing not enough to matter.
Any feedback and comments are welcome. In particular have I placed the components in the appropriate place ?
Thanks