Resonant power converter having switched series transformer
A multi-transformer LLC (resonant) power converter having at least two transformers including a first T 1 and a second transformer T 2 in series includes a switch network configured for receiving input power including a first and second switched node. Resonant circuitry is coupled between the first and second switched node including a series combination of an inductor, a capacitor, a primary winding of T 1 and a primary winding of a T 2 . At least one switch is operable for providing a first mode that includes T 2 in the resonant circuitry and a second mode that excludes T 2 from the resonant circuitry. Secondary windings of T 2 and T 1 are connected electrically in parallel for driving an output capacitor (Co) through respective rectifiers which provide conversion from AC to DC.
1. A resonant power converter, comprising:
a switch network comprising a plurality of power switches configured for receiving input power having a time varying voltage Vin, said switch network providing a first switched node and a second switched node;
resonant circuitry coupled to receive biasing provided by said first switched node, said resonant circuitry comprising in series combination an inductor, a capacitor, a primary winding of a first transformer (T 1 ) and a primary winding of a second transformer (T 2 ), wherein said second switched node is directly connected to a low side node of said T 2 ;
at least one switch connected in parallel to said primary winding of said T 2 operable for providing a first mode that includes said T 2 in said resonant circuitry and a second mode that excludes said T 2 from said resonant circuitry;
wherein a secondary winding on a secondary side of said T 2 and a secondary winding on a secondary side of said T 1 are connected electrically in parallel for driving an output capacitor (Co), and
a first rectifier and a second rectifier, wherein a secondary winding of said T 1 is connected across said Cout by said first rectifier, and wherein a secondary winding of said T 2 is connected across said Cout by said second rectifier.
2. The resonant power converter of claim 1 , wherein said resonant power converter is configured to be in said first mode when said Vin is ≧a predetermined voltage threshold (Vth), and said second mode when said Vin is <said Vth.
3. The resonant power converter of claim 1 , wherein said switch comprises a bidirectional switch.
4. The power converter of claim 3 , wherein the bidirectional switch comprises a plurality of power MOS switches hooked in series.
5. The resonant power converter of claim 1 , wherein said switch network is configured to provide switchable operation between full bridge operation and half bridge operation for said resonant power converter.
6. A method of power converting, comprising:
providing a switch network comprising a plurality of power switches configured for receiving input power having a time varying voltage Vin, said switch network providing said switch network providing a first switched node and a second switched node and a resonant power converter comprising in series an inductor, a capacitor, a primary winding of a first transformer (T i ) and a primary winding of a second transformer (T 2 ), wherein said second switched node is directly connected to a low side node of said T 2 ;
at least one switch connected in parallel to said primary winding of said T 2 , wherein a secondary winding of T 2 and a secondary winding of T 1 are connected electrically in parallel for driving an output capacitor (Co), including a first rectifier and a second rectifier, wherein a secondary winding of said T 1 is connected across said Cout by said first rectifier, and wherein a secondary winding of said T 2 is connected across said Cout by said second rectifier;
switching using said switch between a first mode where a first resonant current passes through said inductor, said capacitor, said primary winding of said T 1 and said primary winding of said T 2 and a second mode where a second resonant current passes through said inductor, said capacitor, said primary winding of said T 1 that bypasses said primary winding of said T 2 .
7. The method of claim 6 , wherein said resonant power converter is in said first mode when said Vin is ≧a predetermined voltage threshold (Vth), and said second mode when said Vin is <said Vth.
8. The method of claim 6 , wherein said switching is implemented by a bidirectional switch.
9. The method of claim 6 , wherein said resonant power converter is switched between full bridge operation and half bridge operation.
10. A resonant power converter, comprising:
a switch network comprising a plurality of power switches configured for receiving input power having a time varying voltage Vin, said switch network providing said switch network providing a first switched node and a second switched node;
resonant circuitry coupled to receive biasing provided by said first switched node, said resonant circuitry comprising in series combination an inductor, a capacitor, a primary winding of a first transformer (T 1 ) and a primary winding of a second transformer (T 2 ), wherein said second switched node is directly connected to a low side node of said T 2 ;
at least one switch operable for providing a first mode that includes said T 2 in said resonant circuitry and a second mode that excludes said T 2 from said resonant circuitry;
wherein a secondary winding on a secondary side of said T 2 and a secondary winding on a secondary side of said T 1 are connected electrically in parallel for driving an output capacitor (Co), and
a first rectifier and a second rectifier, wherein a secondary winding of said T 1 is connected across said Cout by said first rectifier, and wherein a secondary winding of said T 2 is connected across said Cout by said second rectifier,
wherein said resonant power converter is configured to be in said first mode when said Vin is ≧a predetermined voltage threshold (Vth), and said second mode when said Vin is <said Vth.
11. The resonant power converter of claim 1 , wherein said T 1 is larger in size than said T 2 .
12. The method of claim 6 , wherein said T 1 is larger in size than said T 2 .
13. The resonant power converter of claim 10 , wherein said T 1 is larger in size than said T 2 .