Interleaved continuous flyback power converter system

Claim 2

An interleaved continuous flyback power converter system for providing power to a load, said system comprising: an output port for coupling said system to said load; and first and second flyback power converters, wherein said converters are coupled in parallel to said output port and operate in continuous mode, and further wherein each said power converter comprises: an input port for receiving an input voltage; a transformer having a primary winding and a secondary winding, wherein a first terminal of said primary winding is coupled to a first terminal of said input port and further wherein a second terminal of said secondary winding is coupled to a second terminal of said output port; a power switch, said power switch having first and second conduction terminals, wherein voltage across said first and second conduction terminals defines a switch voltage, and further wherein said first conduction terminal of said power switch is coupled to a second terminal of said primary winding and said second conduction terminal of said power switch is coupled to a second terminal of said input port, said power switch being switched to alternating ON and OFF states, wherein power is coupled from said input port to said primary winding during said ON states and wherein substantially no power is coupled from said input port to said primary winding during said OFF states, said transformer storing energy during said ON states and releasing energy to the output port during said OFF states, further wherein said switch voltage is substantially zero volts when said power switch is switched to said ON state from said OFF state; a series combination of a clamp capacitor and a clamp switch, said series combination having one terminal coupled to the first terminal of said input port and the first terminal of said primary winding, said series combination having a second terminal coupled to said second terminal of said primary winding, said clamp switch having an auxiliary ON state and an auxiliary OFF state; and a rectifier, wherein a first terminal of said rectifier is coupled to a first terminal of said secondary winding and a second terminal of said rectifier is coupled to a first terminal of said output port such that current is substantially blocked from flowing from said output port to said secondary winding during said ON states of the power switch and is enabled to flow to said output port during said OFF states; said system further comprising: an output capacitor coupled to said output port; and control means coupled to each of said clamp switches and each of said power switches for switching said power and clamp switches between said ON and OFF states and said auxiliary ON and OFF states, respectively.

Claim 3

The flyback power converter system of claim 1, wherein said power switch is switched between successive ON and OFF states at a frequency of at least 125 kHz.

Claim 4

The flyback power converter system of claim 2, wherein each of said power switches operates at a duty ratio of 50%.

Claim 5

The flyback power converter system of claim 2, wherein each of said power switches operates at a duty ratio greater than 50%.

Claim 6

The flyback power converter system of claim 2, wherein each of said power switches operates at a duty ratio less than 50%.

Claim 7

The flyback power converter system of claim 2, wherein each power converter provides an output current, having a current ripple, to said output port, and further wherein the current outputs of said power converters are interleaved such that overall current ripple of the system is lower than current ripple separately generated by each said converter.

Claim 8

The flyback power converter system of claim 2, wherein there are less than 8 turns in the primary winding and less than 3 turns in the secondary winding.

Claim 9

The flyback power converter system of claim 1, wherein said rectifier is forward biased during said OFF state to enable a secondary current to be conducted in said secondary winding during said OFF state and reverse biased during said ON state to prevent said secondary current from being conducted during said ON state.

Claim 10

The flyback power converter system of claim 8, wherein each said power converter further comprises: a current path enabling electrical current to be conducted through said current path from said first conduction terminal to said clamp capacitor during said OFF state; wherein electrical current is enabled to be conducted from said clamp capacitor to said first conduction terminal during said auxiliary ON state and wherein electrical current is not enabled to be conducted from said clamp capacitor to said first conduction terminal during said auxiliary OFF state; further wherein said clamp switch is switched to said auxiliary ON state while said power switch is in said OFF state, enabling a reverse current to be conducted from said clamp capacitor through said first conduction terminal and said primary winding, and wherein said clamp switch is switched to said auxiliary OFF state a selected period of time before said power switch is switched to said ON state such that said reverse current conducted through said primary winding lowers said switch voltage to approximately zero volts before said power switch is switched to said ON state.

Claim 11

The flyback power converter system of claim 9, wherein said secondary current increases in value at the beginning of the OFF state of the power switch and decreases in value prior to the end of the auxiliary ON state of said clamp switch.

Claim 12

The flyback power converter system of claim 10, wherein said clamp switch of each said power converter is a FET and said current path comprises a body diode of said FET.

Claim 13

The flyback power converter system of claim 11, wherein each said transformer further comprises a primary leakage inductance, and further wherein said clamp capacitor, said clamp switch and said primary leakage inductance in each said converter generate said reverse current in said primary leakage inductance during the OFF state of the corresponding power switch, said reverse current lowering the voltage across said power switch in said selected time period prior to said power switch being switched to its ON state.

Claim 14

The flyback power converter system of claim 8, wherein said secondary current is substantially equal to zero amps when said rectifier becomes forward biased during said OFF state.

Claim 15

The flyback power converter system of claim 8, further comprising means for reducing reverse recovery losses in said rectifier when said rectifier becomes reverse biased.

Claim 16

The flyback power converter system of claim 8, wherein said secondary current increases in value at the beginning of the OFF state of each of said power switches and decreases in value prior to the end of each said OFF state.

Claim 17

The flyback power converter system of claim 15, wherein said secondary current contributed by each power converter has a substantially half-sinusoidal waveform during the OFF period of said power converter such that said secondary current comprises a plurality of substantially half-sinusoidal waveforms.

Claim 18

The flyback power converter system of claim 16, wherein charge contributed to said output current by said first power converter is substantially equal to charge contributed to said output current by said second power converter.

Claim 19

The flyback power converter system of claim 1, wherein there are less than 17 turns in the primary winding and less than 6 turns in the secondary winding.

Claim 20

The flyback power converter system of claim 1, wherein said system produces an output voltage at said output port of not more than 48 volts.

Claim 21

The flyback power converter system of claim 19, wherein said system produces an output voltage at said output port of not more than 24 volts.

Claim 22

The flyback power converter system of claim 20, wherein said system produces an output voltage of not more than 5 volts and an output power greater than 100 watts.

Claim 23

The flyback power converter system of claim 1, wherein said output capacitor is a multilayer plastic capacitor.

Claim 24

The flyback power converter system of claim 1, wherein said output voltage waveform does not include undesirable harmonic content thereby eliminating the need for a secondary side choke.

Claim 25

The flyback power converter system of claim 1 having a reduced level of Electromagnetic Interference (EMI) in the secondary circuit.

Claim 26

The flyback power converter system of claim 24, wherein EMI is reduced when the power switch is turned ON.

Claim 27

The flyback power converter system of claim 1, wherein said transformer of each said power converter comprises a plurality of series-connected transformers.

Claim 28

The flyback power converter system of claim 1, wherein said control means causes said two power converters to operate 180 degrees out of phase with respect to each other.

Claim 29

The flyback power converter system of claim 1, wherein the voltage across each said clamp capacitor has a substantially sinusoidal shape during the OFF state of the power switch with which said clamp capacitor is associated.

Claim 30

The flyback power converter system of claim 1, wherein current flowing through said clamp capacitor during the OFF state of the power switch with which said clamp capacitor is associated has a substantially sinusoidal shape.

Claim 31

The flyback power converter system of claim 1, wherein current flowing through said clamp capacitor, during the OFF state of the power switch with which said clamp capacitor is associated, has a waveform that corresponds substantially to a half-cycle of a sinusoid.

Claim 32

The flyback power converter system of claim 1, wherein each said transformer comprises a magnetizing inductance through which a corresponding magnetizing current flows, and further wherein each said power switch is operated such that said magnetizing current of said magnetizing inductance flows continuously in one direction during successive ON states of each said power switch.

Claim 33

A flyback power converter system for providing power to a load, said system comprising: an output port for coupling said system to said load; and N flyback power converters, where N is an integer greater than two, wherein said N flyback power converters are coupled in parallel to said output port and operated in continuous mode, and further wherein each of said power converters is operated 360/N degrees out of phase with respect to another one of said power converters and each of said power converters comprises: an input port for receiving an input voltage; a transformer having a primary winding and a secondary winding, wherein a first terminal of said primary winding is coupled to a first terminal of said input port and further wherein a second terminal of said secondary winding is coupled to a second terminal of said output port; a power switch, said power switch having first and second conduction terminals, wherein voltage across said first and second conduction terminals defines a switch voltage, and further wherein said first conduction terminal of said power switch is coupled to a second terminal of said primary winding and said second conduction terminal of said power switch is coupled to a second terminal of said input port, said power switch being switched to alternating ON and OFF states, wherein power is coupled from said input port to said primary winding during said ON states and wherein substantially no power is coupled from said input port to said primary winding during said OFF states, said transformer storing energy during said ON states and releasing energy to the output port during said OFF states, further wherein said switch voltage is substantially zero volts when said power switch is switched to said ON state from said OFF state; a series combination of a clamp capacitor and a clamp switch, said series combination having one terminal coupled to the first terminal of said input port and the first terminal of said primary winding, said series combination having a second terminal coupled to said second terminal of said primary winding, said clamp switch having an auxiliary ON state and an auxiliary OFF state; and a rectifier, wherein a first terminal of said rectifier is coupled to a first terminal of said secondary winding and a second terminal of said rectifier is coupled to a first terminal of said output port such that current is substantially blocked from flowing from said output port to said secondary winding during said ON states of the power switch and is enabled to flow to said output port during said OFF states; said system further comprising: an output capacitor coupled to said output port; and control means coupled to each of said clamp switches and each of said power switches for switching said power and clamp switches between said ON and OFF states and said auxiliary ON and OFF states, respectively.

Claim 34

A flyback power converter system for providing power to a load, said system comprising: an output port for coupling said system to said load; and N flyback power converters, where N is an integer greater than two, wherein said N flyback power converters are coupled in parallel to said output port and operated in continuous mode, and further wherein each of said power converters is operated 360/N degrees out of phase with respect to another one of said power converters and each of said power converters comprises: an input port for receiving an input voltage; a transformer having a primary winding and a secondary winding, wherein a first terminal of said primary winding is coupled to a first terminal of said input port and further wherein a second terminal of said secondary winding is coupled to a second terminal of said output port; a power switch, said power switch having first and second conduction terminals, wherein voltage across said first and second conduction terminals defines a switch voltage, and further wherein said first conduction terminal of said power switch is coupled to a second terminal of said primary winding and said second conduction terminal of said power switch is coupled to a second terminal of said input port, said power switch being switched to alternating ON and OFF states, wherein power is coupled from said input port to said primary winding during said ON states and wherein substantially no power is coupled from said input port to said primary winding during said OFF states, said transformer storing energy during said ON states and releasing energy to the output port during said OFF states, further wherein said switch voltage is substantially zero volts when said power switch is switched to said ON state from said OFF state; a series combination of a clamp capacitor and a clamp switch, said series combination having one terminal coupled to the first terminal of said input port and the first terminal of said primary winding, said series combination having a second terminal coupled to said second terminal of said primary winding, said clamp switch having an auxiliary ON state and an auxiliary OFF state; and a rectifier, wherein a first terminal of said rectifier is coupled to a first terminal of said secondary winding and a second terminal of said rectifier is coupled to a first terminal of said output port such that current is substantially blocked from flowing from said output port to said secondary winding during said ON states of the power switch and is enabled to flow to said output port during said OFF states; said system further comprising: an output capacitor coupled to said output port; and control means coupled to each of said clamp switches and each of said power switches for switching said power and clamp switches between said ON and OFF states and said auxiliary ON and OFF states, respectively.