Constant DC current input to constant DC voltage output power supply covering a wide programmable range

1. An apparatus comprising:

an active bridge section with input terminals that receive power from a direct current (“DC”) constant current source, wherein the active bridge section operates at a fixed switching frequency;

a resonant section comprising a resonant inductor, a transformer and a resonant capacitor, the resonant inductor connected in series with a primary winding of the transformer and the resonant capacitor connected in parallel with a secondary winding of the transformer, the resonant section connected to an output of the active bridge section;

an output rectifier section that receives power from the resonant section and comprising output terminals for connection to a load; and

a controller that regulates output voltage to the load, wherein the controller regulates output voltage to the load by controlling switching of the active bridge section,

wherein the fixed switching frequency of the active bridge section matches a resonant frequency of the resonant section.

2. The apparatus of claim 1 , wherein the controller regulates output voltage to the load using a symmetrical phase shift modulation of a phase shift angle between a first leg and a second leg of the active bridge section, wherein the first leg and the second leg each operate at a 50 percent duty cycle.

3. The apparatus of claim 2 , wherein the controller regulates output voltage according to:

V

out

=

Z

o

⁢

I

i

⁢

n

n

⁢

sin

⁢

α

2

wherein:

Z o is a characteristic impedance of the resonant section;

V out is output voltage;

I in is input current;

n is a turns ratio of the transformer; and

α is the phase shift angle.

4. The apparatus of claim 1 , wherein the active bridge section comprises a full active bridge and the output rectifier section comprises a full-bridge regulator and the resonant section is configured as a parallel resonant section.

5. The apparatus of claim 1 , wherein the transformer further comprises two or more secondary windings and each winding comprises a different number of turns.

6. The apparatus of claim 5 , wherein at least one secondary winding comprises a capacitor connected in parallel with the secondary winding, and wherein capacitors connected to the secondary windings combine to form the resonant capacitor.

7. The apparatus of claim 5 , wherein each secondary winding comprises a switch connected in series with the secondary winding to disconnect the secondary winding.

8. The apparatus of claim 5 , wherein each secondary winding is connected to an output rectifier section and each output rectifier section is connected in parallel to the output terminals.

9. The apparatus of claim 8 , wherein two or more secondary windings are connected to a single output rectifier section.

10. The apparatus of claim 5 , wherein each secondary winding is related by a common turns ratio.

11. The apparatus of claim 5 , wherein each secondary winding is related by:

n

1

⁢

:

⁢

n

2

⁢

:

⁢

n

3

⁢

⁢

…

⁢

⁢

n

m

=

1

⁢

:

⁢

r

⁢

:

⁢

r

1

⁢

⁢

…

⁢

⁢

r

m

-

1

r

=

(

V

max

V

min

)

1

m

wherein:

m is the number of secondary windings;

V max is a maximum voltage of a desired output voltage range; and

V min is a minimum voltage of the desired output voltage range.

12. The apparatus of claim 1 , wherein the output rectifier section comprises active switches.

13. The apparatus of claim 1 , wherein the output rectifier section is configured as a full bridge rectifier and comprises an inductor and a capacitor configured as a low pass filter.

14. A apparatus comprising:

an active bridge section with input terminals that receive power from a direct current (“DC”) constant current source, wherein the active bridge section operates at a fixed switching frequency;

a resonant section comprising a resonant inductor, a transformer and a resonant capacitor, the resonant inductor connected in series with a primary winding of the transformer and the resonant capacitor connected in parallel with a secondary winding of the transformer, the resonant section connected to an output of the active bridge section, wherein the transformer comprises two or more secondary windings and each secondary winding comprises a different number of turns;

one or more output rectifier sections, wherein each secondary winding is connected to an output rectifier section and each rectifier section is connected in parallel to output terminals for connection to a load; and

a controller that regulates output voltage to the load, wherein the controller regulates output voltage to the load by controlling switching of the active bridge section.

15. The apparatus of claim 14 , wherein the fixed switching frequency of the active bridge section matches a resonant frequency of the resonant section.

16. The apparatus of claim 14 , wherein at least one secondary winding comprises a resonant capacitor connected in parallel with the secondary winding, and wherein capacitors connected to the secondary windings combine to form the resonant capacitor.

17. The apparatus of claim 14 , wherein each secondary winding comprises a switch connected in series with the secondary winding to disconnect the secondary winding.

18. The apparatus of claim 14 , wherein the controller regulates output voltage to the load using a symmetrical phase shift modulation of a phase shift angle between a first leg and a second leg of the active bridge section, wherein the first leg and the second leg each operate at a 50 percent duty cycle and wherein the controller regulates output voltage according to:

V

out

=

Z

o

⁢

I

i

⁢

n

n

⁢

sin

⁢

α

2

wherein:

Z o is a characteristic impedance of the resonant section;

V out is output voltage;

I in is input current;

n is a turns ratio of the transformer; and

α is the phase shift angle.

19. The apparatus of claim 14 , wherein the active bridge section comprises a full active bridge and the output rectifier section comprises a full-bridge regulator and the resonant section is configured as a parallel resonant section.

20. An apparatus comprising:

an active bridge section with input terminals that receive power from a direct current (“DC”) constant current source, wherein the active bridge section operates at a fixed switching frequency;

a resonant section comprising:

a resonant inductor;

a transformer comprising a primary winding and a plurality of secondary windings, each secondary winding comprises a different number of turns;

a resonant capacitor; and

a switch configured to connect and disconnect each secondary winding,

wherein the resonant inductor is connected in series with the primary winding and the resonant capacitor comprises one or more capacitors connected in parallel with one or more of the secondary windings,

wherein the resonant section is connected to an output of the active bridge section;

one or more output rectifier sections, wherein each secondary winding is connected to an output rectifier section and each rectifier section is connected in parallel to output terminals for connection to a load, wherein each rectifier section comprises a full bridge rectifier and a filter inductor connected to an output of the full bridge rectifier, and the one or more output rectifier sections connect in parallel to an output capacitor, which is connected in parallel with the output terminals; and

a controller that regulates output voltage to the load, wherein the controller regulates output voltage to the load by controlling switching of the active bridge section,

wherein the fixed switching frequency of the active bridge section matches a resonant frequency of the resonant section.