Integrated magnetic converter circuit and method with improved filtering

A dc/dc conversion method comprising:

• providing a voltage to a primary winding of a transformer, the voltage causing a first current to flow in a first secondary winding, a second current to flow in a second secondary winding, and a third current to flow in a third secondary winding, the third current being a summation of the first and second currents;
• rectifying the first current using a first rectifier;
• rectifying the second current using a second rectifier;
• filtering the third current using inductance of the third secondary winding, the third winding being connected in series with an output capacitor;
• charging the output capacitor using the third current;
• providing dc power to a power-consuming device using the output capacitor.

A dc/dc converter circuit comprising:

• (A) a magnetic core, the magnetic core having a center leg, a first outer leg, and a second outer leg, the first and second outer legs being disposed on opposite sides of the center leg;
• (B) a primary winding;
• (C) an output capacitor, the output capacitor having first and second terminals which respectively form first and second output terminals of the dc/dc converter circuit;
• (D) a first secondary winding, the first secondary winding being wound around the first outer leg of the magnetic core,
• (E) a second secondary winding, the second secondary winding being wound around the second outer leg of the magnetic core, and
• (F) a third secondary winding, the third secondary winding implementing a filtering inductor and being connected in series with the output capacitor;
• (G) a first rectifier, the first rectifier being connected between the output capacitor and the first secondary winding;
• (H) a second rectifier, the second rectifier being connected between the output capacitor and the second secondary winding;
• (I) a circuit board, the circuit board having the magnetic core mounted thereto, with the first and second outer legs and the center leg of the transformer extending through holes formed in the circuit board, and the circuit board having traces which at least partially form the primary winding, the first secondary winding, the second secondary winding, and the third secondary winding;
• (J) an drive circuit, the drive circuit being connected to receive power from an input voltage source and being connected across the primary winding to provide a pulse width modulated voltage to the primary winding;
• and
• (K) a feedback control circuit, the feedback control circuit including a voltage measurement circuit, the voltage measurement circuit being connected to the output capacitor to measure an output voltage across the first and second output terminals, and the feedback control circuit controlling the drive circuit to vary a duty cycle of a pulse width modulated voltage applied by the drive circuit to the primary winding, the duty cycle being controlled based on the measured output voltage to minimize deviation from of the output voltage from a setpoint level.