High voltage side overcurrent and overvoltage protection circuit

A protection circuit for a high voltage (HV) DC/DC flyback switching power supply, comprising:

• a protection circuit transistor (Mprot) in electrical series connection with a first pole of a HV cellstack, a primary inductor, a switching transistor, and a second pole of a HV cellstack on a HV input side of the HV DC/DC flyback switching power supply, wherein a gate of the switching transistor is controlled by a switching regulator connected to be powered by the HV cellstack from a power supply by means of an electrical parallel connection to the electrical series connection of the protection circuit transistor and the switching transistor, wherein the protection circuit transistor has a gate connected to a switching node providing a switching voltage of the HV input side, wherein the switching node is in electrical series connection between the primary inductor and the switching transistor;
• a rectifying diode connected between the switching node and the gate of the protection circuit transistor, wherein the rectifying diode is configured for rectifying voltage peaks caused by inductance of the primary inductor to power the protection circuit;
• and
• a sensing block configured to detect an electrical failure on the HV input side.