Electric propulsion system including heaterless dispenser cathode

1. A circuit for igniting and sustaining an electron discharge, comprising:

an ignitor circuit including:

a voltage transformer which is an in-phase transformer that includes a primary and a secondary, the primary including a first dot terminal and a first non-dot terminal, and the secondary including a second dot terminal and a second non-dot terminal;

a switch connected in series between the first-non dot terminal of the primary of the transformer and a DC source return, the switch configured to receive a driving signal;

a reset circuit connected in parallel to the primary of the voltage transformer;

a first rectifier connected in series between the second dot terminal of the secondary of the voltage transformer and a first node, the first node connecting an output of the first rectifier to a keeper;

the second non-dot terminal of the secondary of the voltage transformer connected to a dispenser cathode via a second node that is different than the first node; and

a sustaining circuit including:

a current source having a return connected to the second node; and

a second rectifier connected in series between the current source and the first node.

2. The circuit of claim 1 , further comprising a plurality of power sources connected to at least one input power connection, the at least one power input connection providing input power to each of the ignitor circuit and the sustaining circuit.

3. The circuit of claim 2 , wherein the voltage transformer is connected to a DC power source through the at least one power input.

4. The circuit of claim 3 , wherein the high ratio transformer has a winding ratio of at least 10 to 1.

5. The circuit of claim 4 , wherein the winding ratio is at least 100:1.

6. The circuit of claim 4 , wherein the winding ratio is approximately 60:1.

7. The circuit of claim 1 , wherein the circuit characterized by a lack of an output capacitor.

8. The circuit of claim 1 , wherein:

the reset circuit comprises a linear arranged diode and Zener diode;

a cathode of the diode and a cathode of the Zener diode are connected in series;

an anode of the diode is connected in series to a first terminal of the reset circuit; and

an anode of the Zener diode is connected in series to a second terminal of the reset circuit that is different from the first terminal.

9. The circuit of claim 1 , wherein the switch is connected in series between a primary of the transformer and a DC source return, and the switch is controlled via a controller.

10. The circuit of claim 9 , wherein the switch is a MOSFET (metal oxide semi-conductor field effect transistor).

11. The circuit of claim 1 , wherein when the switch is closed, and the DC source is applied across a primary of the transformer to produce a voltage on a secondary of the transformer.

12. The circuit of claim 1 , wherein the current source comprises an isolated converter and an inductor.

13. The circuit of claim 12 , wherein the current source is a buck based converter.

14. The circuit of claim 12 , wherein the sustaining circuit further comprises a DC load connecting an input of the second rectifier to the second node.

15. The circuit of claim 12 , wherein a voltage of the DC load is set to a higher level than an expected discharge of the dispenser cathode.

16. The circuit of claim 1 , wherein the current source includes an inductor connected in series with an input of the second rectifier.