Energy recovery from the leakage inductance of the transformer
AssigneeRompower Technology Holdings, LLC
InventorIonel Jitaru
Life of this patent
Estimating the term…
Abstract
Electronic circuitry and method of operating the same to shape and reduce the circulating current through the active clamp in a flyback converter and to harvest most of the leakage inductance energy to provide the bias power. Methodologies for minimizing the circulating energy in the clamp circuit in order to improve efficiency of operation of the same. A method for using a portion of the leakage inductance energy in order to create zero voltage switching conditions at the main primary switch.
Claims18
An electronic circuitry having primary and secondary sides and comprising:
- a flyback power converter including:
- an input voltage source;
- a transformer having primary and secondary windings, on the primary and secondary sides, respectively;
- a main switch in series with the primary winding on the primary side;
- and
- a synchronous rectifier in series with the secondary winding on the secondary side;
- an active clamp circuit across the main switch, the active clamp circuit containing a clamp switch and the clamp capacitor in series with the clamp switch;
- an auxiliary circuit that contains two additional rectifiers connected in parallel with one another and in series with an electronic component configured to store electromagnetic energy;
- wherein the clamp switch is configured to be turned on at a moment of time after the main switch is turned off;
- wherein the clamp switch is configured to be turned off at a moment of time prior to the moment of time at which current passing through the secondary winding reaches a zero level;
- wherein the electronic circuitry is characterized by a first value of rms current through the clamp capacitor;
- wherein a cathode of a first of the two additional rectifiers is directly electrically connected with a cathode of the active clamp circuit;
- wherein an anode of a second of the two additional rectifiers is directly electrically connected with the cathode of the first of the two additional rectifiers;
- wherein a cathode of the second of the two additional rectifiers is directly electrically connected with a first terminal of said electronic component;
- and
- wherein a second terminal of said electronic component is electrically connected with an anode of the second of the two additional rectifiers, wherein said auxiliary circuit is configured to reduce the rms current through the clamp capacitor from the first value to a second value, the second value being at least 40% lower than the first value.
The electronic circuitry according 3, wherein the primary side includes a driving winding, a first terminal of the driving winding directly connected to a terminal of the primary winding, the second terminal of the driving winding directly connected to a differential electronic circuitry, wherein the differential electronic circuitry is configured to generate a control voltage signal to the clamp switch to drive the active clamp circuit.
A method for operation of electronic circuitry having primary and secondary sides and comprising:
- a flyback power converter including
- an input voltage source,
- a transformer having primary and secondary windings, on the primary and secondary sides, respectively,
- a main switch in series with the primary winding on the primary side, and
- a synchronous rectifier in series with the secondary winding on the secondary side, and
- an active clamp circuit across the main switch, the active clamp circuit containing a clamp switch and the clamp capacitor in series with the clamp switch,
- wherein said circuitry is characterized by an electrical charge, injected into the clamp capacitor after the main switch is turned off, in operation, said electrical charge having a first charge value,
- the method comprising:
- electrically-connecting said circuitry with an auxiliary electronic circuit in series with the clamp capacitor, wherein the auxiliary circuit contains two rectifiers and an auxiliary energy storage;
- and
- directing a current, flowing through a leakage inductance of the primary side in operation of said circuitry, to flow through the clamp capacitor and then through a first of the two rectifiers towards the auxiliary energy storage to change said first charge value to a second charge value,
- wherein the second charge value is smaller than the first charge value,
- wherein a current passing through the clamp capacitor after the mains switch is turned off is a clamp capacitor current.
Dependencies are inferred from the claim text.