Loosely regulated feedback control for high efficiency isolated DC-DC converters
The improved DC-DC converter apparatus includes a primary side circuit and a secondary side circuit that is galvanically isolated from the primary. The primary side induces a voltage in the secondary side that provides an output voltage for driving POLs. A flux-control device measures the transformer primary side flux to control the primary side duty cycle, thereby loosely regulating the output voltage of the secondary side circuit.
1. An isolated DC-DC converter system comprising:
a primary side circuit;
a secondary side circuit;
a transformer comprising at least one primary side winding and a secondary side winding; and
a flux-control device;
wherein
said primary side circuit is configured to accept an input voltage;
said secondary side circuit is galvanically isolated from said primary side circuit by said transformer;
said secondary side circuit is configured to generate an output voltage determined by a duty cycle of said primary side circuit;
said flux-control device is configured to vary said duty cycle of said primary side circuit based only upon a measured volt-second of a monitored primary side winding of said transformer; and
said flux-control device is configured to loosely regulate said output voltage by adjusting said duty cycle of said primary side circuit.
2. The isolated DC-DC converter system of claim 1 , wherein said flux-control device is configured to allow 2% or greater variation in said output voltage in response to changes in said input voltage.
3. The isolated DC-DC converter system of claim 1 wherein said flux-control device comprises an RC circuit configured to measure the volt-second of said monitored primary side winding of said transformer.
4. The isolated DC-DC converter system of claim 1 wherein said flux-control device comprises:
an RC circuit configured to measure the volt-second of said monitored primary side winding of said transformer; and
a voltage comparator circuit configured to control said duty cycle based upon an output of said RC circuit.
5. The isolated DC-DC converter system of claim 1 wherein said flux-control device comprises:
an RC circuit configured to measure the volt-second of said monitored primary side winding of said transformer;
a voltage comparator circuit configured to control said duty cycle based upon an output of said RC circuit; and
a discharge circuit configured to discharge said RC circuit.
6. The isolated DC-DC converter system of claim 1 wherein said flux-control device estimates and regulates a peak flux in said monitored primary side winding of said transformer.
7. An isolated DC-DC converter method-comprising:
in an isolated DC-DC converter comprising a primary side circuit galvanically isolated from a secondary side circuit, a galvanic isolation provided by a transformer comprising at least one primary winding and a secondary winding,
measuring a volt-second of a monitored primary side winding of said transformer; and
loosely regulating a voltage output of said secondary side circuit by altering a duty cycle of said monitored primary side circuit based only on said volt-second measurement.
8. The isolated DC-DC converter method of claim 7 wherein said loose regulation occurs only during normal operating states of said isolated DC-DC converter.
9. The isolated DC-DC converter method of claim 7 wherein said volt-second measurement of said monitored primary side winding is measured using an RC circuit.
10. The isolated DC-DC converter method of claim 7 further comprising:
measuring said volt-second of said monitored primary side winding of said transformer with an RC circuit; and
adjusting the duty cycle of said primary side circuit based on the output of said RC circuit.