Fine tuned multiple output converter

1. A controller for regulating the output voltages in a multiple output flyback converter, the converter having a primary electronically controlled switch operatively associated with a primary winding and an active clamp and a plurality of secondary windings electromagnetically coupled to the primary winding, each of the secondary windings operatively associated with a particular one of a plurality of secondary electronically controlled switches and a respective one of a plurality of outputs, each of the plurality of outputs exhibiting an output voltage, the controller comprising:

a plurality of error circuits, each of said plurality of error circuits coupled to a respective one of the particular outputs and arranged to output an error signal representative of the difference between a predetermined reference voltage and a function of the respective output voltage;

a comparison circuit arranged to compare each of the output error signals with a time varying signal and output a plurality of comparison signals each reflecting the comparison of a respective one of the output error signals with the time varying signal; and

a control circuit arranged to control the alternate closing and opening of the primary electronically controlled switch responsive to the dynamically detected output comparison signal associated with the largest of the differences between the predetermined reference voltage and the function of the respective output voltage and to control the closing and opening of each of the plurality of secondary electronically controlled switches responsive to the respective comparison signal.

2. A controller according to claim 1 , arranged such that the opening and closing of the primary electronically controlled switch is directly opposite the opening and closing of the respective secondary electronically controlled switch associated with said largest difference.

3. A controller according to claim 1 , wherein said control circuit simultaneously opens said plurality of secondary electronically controlled switches prior to closing said primary switch.

4. A controller according to claim 1 , wherein said control circuit further comprises a ramp voltage generator arranged to generate the time varying signal and wherein said comparison circuit comprises a plurality of comparators, each of said plurality of comparators associated with a particular one of said output error signals and in communication with said ramp voltage generator, said control of the closing and opening of each of said plurality of secondary switches responsive to a respective comparator.

5. A method of regulating output voltages in a multiple output flyback converter having a primary side electronically controlled switch associated with a primary winding and a plurality of secondary side electronically controlled switches each associated with a particular secondary winding and a particular output, said method comprising:

comparing a voltage component of each of the particular outputs to a reference voltage to determine a plurality of respective error values;

comparing each of the respective error values with a time varying signal to produce a plurality of comparison signals each reflecting the comparison of a respective one of the respective error values with the time varying signal;

dynamically determining the comparison signal reflecting the largest error value;

controlling the duty cycle of the primary side electronically controlled switch responsive to said dynamically determined comparison signal reflecting the largest error value thereby regulating the output voltage having the largest error value;

controlling the secondary side electronically controlled switch associated with the output voltage having the largest error value opposite the primary switch;

controlling each of the secondary side electronically controlled switches not associated with the largest error value responsive to the respective comparison signal to regulate the respective outputs; and

actively clamping a voltage spike associated with the first electronically controlled switch to a maximum value.

6. The method of claim 5 , further comprising:

opening the plurality of secondary side switches prior to closing the primary side electronically controlled switch.

7. The method of claim 5 , wherein said active clamping forces a respective constant voltage at each of the particular outputs when the primary side electronically controlled switch is open, said respective constant voltage being a function of the turns ratio of the respective secondary winding to the primary winding.

8. The method of claim 5 , wherein said controlling each of the secondary side electronically controlled switches not associated with the largest error value is by leading edge modulation.

9. A multiple output flyback converter comprising:

a primary winding;

a first electronically controlled switch operatively connected to an end of said primary winding and arranged to draw current through said primary winding when said first electronically controlled switch is closed and to interrupt said current through said primary winding when said first electronically controlled switch is open;

an active clamp operatively connected to said end of said primary winding and arranged to clamp a voltage spike at said end of said primary winding from exceeding a predetermined value;

a plurality of secondary windings electromagnetically coupled to said primary winding, each associated with a respective output arranged to provide an output voltage;

a plurality of second electronically controlled switches each connected in series with a respective one of said plurality of secondary windings and arranged to allow current flow through said respective secondary winding when closed; and

a controller operatively coupled to the control terminal of each of said plurality of second electronically controlled switches, arranged to receive an indication of each of the respective output voltages and in communication with the control terminal of said first electronically controlled switch,

said controller comprising:

a plurality of error circuits each of said plurality of error circuits coupled to a respective one of the outputs and arranged to output an error signal representative of the difference between a predetermined reference voltage and a function of the respective output voltage;

a comparison circuit arranged to compare each of the output error signals with a time varying signal and output a plurality of comparison signals each reflecting the comparison of a respective one of the output error signals with the time varying signal; and

a control circuit arranged to control the alternate closing and opening of the primary electronically controlled switch responsive to the dynamically detected output comparison signal associated with the largest of the differences between the predetermined reference voltage and the function of the respective output voltage and to control the closing and opening of each of the plurality of secondary electronically controlled switches responsive to the respective comparison signal.

10. A multiple output flyback converter according to claim 9 , wherein said controller is further operative to control the opening and closing of the second electronically controlled switch connected to the secondary winding associated with the largest of the differences between the predetermined reference voltage and the function of the respective output voltage opposite the closing and opening of the primary electronically controlled switch.

11. A multiple output flyback converter according to claim 9 , wherein said controller is further operative to apply leading edge modulation to each of said secondary electronically controlled switches responsive to an error condition of said respective associated output voltage.

12. A multiple output flyback converter according to claim 9 , wherein said control circuitry is further operative to simultaneously open said plurality of second electronically controlled switches prior to closing said first electronically controlled switch.

13. A multiple output flyback converter according to claim 9 , wherein said controller further comprises:

a ramp voltage generator arranged to provide the time varying signal; and

wherein said comparison circuit comprises a plurality of comparators, each of said plurality of comparators associated with a particular one of said output error signals and in communication with said ramp voltage generator, said control of the closing and opening of each of said plurality of secondary switches responsive to a respective comparator.

14. A multiple output flyback converter according to claim 9 , wherein said active clamp forces a respective value for each of said respective output voltages when said first electronically controlled switch is open, said respective value being a function of the turns ratio of said respective secondary winding to said primary winding.

15. A multiple output flyback converter according to claim 9 , wherein each of said plurality of second electronically controlled switches comprises a metal oxide semiconductor field effect transistor.

16. A multiple output flyback converter according to claim 9 , wherein each of said plurality of second electronically controlled switches comprises a single n-channel metal-oxide-semiconductor field-effect-transistor exhibiting a source terminal, a drain terminal and a gate terminal, wherein said control terminal is represented by said gate terminal, said drain terminal is connected to said respective secondary winding and said source terminal is connected to a common point.