Resonant current driven power source for low input voltages

A method for regulating a DC voltage, comprising the steps of:

• converting an input DC voltage into an AC voltage having substantially no DC components and applying said AC voltage across an LC circuit including an inductor and a capacitor electrically coupled to one another;
• converting said AC voltage appearing across said capacitor into a DC output voltage for supplying said DC output voltage to a load;
• and
• prior to applying said AC voltage across said LC circuit, stepping said AC voltage up to a level substantially greater than the level of said input DC voltage to improve the operating efficiency of the power source for low input voltages.

A power source, comprising:

• an LC circuit including an inductor and a capacitor electrically coupled to one another;
• said LC circuit having a resonant frequency determined by said inductor and capacitor;
• a switching circuit for switching current flow through said LC circuit at a switching frequency which is lower than said resonant frequency, said switching circuit permitting current flow through said LC circuit only in a single direction during each half cycle of said switching frequency;
• an output transformer having a primary and a secondary winding;
• said capacitor being coupled only in parallel with said primary winding;
• an output circuit coupled to said secondary winding for applying power to a load;
• a power input circuit for receiving a DC voltage and converting it to an AC voltage and applying said AC voltage to said LC circuit during a portion of each half cycle of said switching frequency, the polarity of said AC voltage being reversed for each successive half cycle of said switching frequency so as to cause an AC current flow through said LC circuit;
• said input circuit including an input transformer having a center-tapped primary to which said DC voltage is applied and having a center-tapped secondary through which said AC voltage is applied across said LC circuit;
• the level of said AC voltage being changed by the input transformer to improve the operating efficiency of the power source for low input voltages;
• and
• a control circuit for controlling the operation of said power input circuit by adjusting the portion of each said half cycle during which said AC voltage is applied to said LC circuit so as to adjust the output voltage applied to said load.

A method for regulating a DC voltage in a power source including an LC circuit having an inductor and a capacitor electrically coupled to one another, said LC circuit having a resonant frequency determined by said inductor and capacitor, an output transformer having a primary and a secondary winding, said capacitor being coupled only in parallel with said primary winding, and an output circuit coupled to said secondary winding for applying an output voltage to a load, said method comprising the steps of:

• controlling current flow through said LC circuit at a switching frequency which is lower than said resonant frequency in such a manner that current is permitted to flow through said LC circuit only in a single direction during each half cycle of said switching frequency;
• converting said DC voltage to an AC voltage and applying said AC voltage to said LC circuit during a portion of each half cycle of said switching frequency, the polarity of said AC voltage being reversed for each successive half cycle of said switching frequency so as to cause an AC current flow through said LC circuit;
• prior to applying said AC voltage to said LC circuit, changing the level of said AC voltage to a level different from that of said DC voltage to improve the operating efficiency of the power source for low input voltages;
• and
• adjusting the portion of each said half cycle during which the AC voltage is applied to said LC circuit so as to adjust the output voltage applied to said load.

A power source comprising:

• and LC circuit including an inductor and a capacitor electrically coupled to one another;
• an input inverter circuit for converting an input DC voltage into an AC voltage having substantially no DC components, said input inverter circuit applying said AC voltage across said LC circuit in a manner which causes said inductor and capacitor to resonate with one another, a resonant AC voltage thereby appearing across said capacitor;
• and
• an output circuit for applying power from said inverter circuit to a load;
• said input inverter including a transformer having a center-tapped primary to which said DC voltage is applied and having a center-tapped secondary through which said AC voltage is applied across said LC circuit for changing the level of said AC voltage to a level different from the level of said DC voltage to improve the operating efficiency of the power source for low input voltages.

A method for regulating a DC voltage, comprising the steps of:

• converting an input DC voltage into an AC voltage having substantially no DC components and applying said AC voltage across an LC circuit including an inductor and a capacitor electrically coupled to one another;
• converting said AC voltage appearing across said capacitor into a DC output voltage for applying said DC output voltage to a load;
• and
• prior to applying said AC voltage across said LC circuit, changing the level of said AC voltage to a level different from the level of said DC voltage to improve the operating efficiency of the power source for low input voltages.