Switch mode power supply with reduced switching losses

A switch mode power supply, comprising:

• a switching transistor having a load path formed by a first main connection and a second main connection, said first main connection and said second main connection for receiving a voltage applied thereto, said switching transistor including a semiconductor body with a semiconductor layer of a first conductance type forming a drift area;
• a load connected in series with said load path of said switching transistor;
• a continuous drain region of a second conductance type incorporated into said drift area and connected to said first main connection;
• a continuous source region of the second conductance type incorporated into said drift area and connected to said second main connection;
• a reverse-biased pn-junction produced by an interaction between said semiconductor body and said continuous drain region and between said semiconductor body and said continuous source region;
• said reverse-biased pn-junction having a large inner voltage-dependent surface area that is variable as a function of the voltage applied to said first main connection and said second main connection;
• when the voltage applied is 10 V, said switching transistor is characterized by a first product of a switch-on resistance Ron and a gate charge Qgtot, the first product given by:
• Ron*Qgtot/10 V≦2.5 ns;
• and
• when the voltage applied is 400 V, said switching transistor is characterized by a second product of the switch-on resistance Ron and energy Eds stored in a drain-source capacitance, the second product given by Ron*Eds≦1.6 V2 μs.