POWER CONVERSION SYSTEM FOR ELECTRICAL POWERED THRUSTERS

FIELD OF THE INVENTION

The present invention relates to a power conversion system for electrically- powered thrusters located on and/or inside a satellite.

BACKGROUND OF THE INVENTION

Electric propulsion is a technology, which enables spacecraft to manoeuvre with very high efficiency and specific impulse, but with relatively low thrust. Although electric propulsion systems consume significantly less propellant than their chemical counterparts, they require significantly more power to operate. This can pose a great challenge to small satellites, which are mass- and power-limited as a result of their comparatively small solar arrays and/or batteries.

Hence, an improved propulsion system would be advantageous, and in particular, a more efficient use of mass and power would be advantageous.

SUMMARY OF THE INVENTION

Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a satellite comprising an electrically-powered thruster and a power conversion system for providing electrical power to the electrically-powered thruster, said conversion system may comprising:

• a power input for inputting low voltage current with different polarity;

• a voltage converter and an electrical energy storage (9), said voltage converter may be electrically connected to the power input to receive low voltage current and may be configured to convert low voltage current into high voltage current, the voltage converter may have two high voltage output terminals with different polarity, wherein one of the high voltage output terminals may be connected to the electrical powered thruster, and the electrical energy storage may be electrically connected so that at least a part of the high voltage current is stored in the electrical energy storage;

• a switch electrically connected to other one of the high voltage output terminals of the voltage converter and may have an output terminal connected to said electrical powered thruster, wherein the switch may be configured to operate in a connected mode wherein a current may be conducted from the voltage converter to the electrical powered thruster and a disconnected mode wherein no current may be conducted from the voltage converter to the electrical powered thruster, said two modes may be selective in response to the switch receiving a control signal.

This is particularly, but not exclusively advantageous as the system facilitates the use of electric propulsion in mass- and power-limited satellites such as small satellites, nanosatellites or picosatellites.

In a preferred embodiment, the electrical energy storage may be electrically connected so that at least a part of power at the two high voltage output terminals may be provided by the electrical energy storage.

In another preferred embodiment, the switch may be controlled so that the power consumed by the thruster may be in the range 20.0 watts to 0.01 watts such as between 10.0 watts and 0.05 watts, preferably 0.25 watts to 1.0 watts.

In some embodiments, the switch may be connected to the positive terminal of the converter.

In other embodiments, the switch may be connected to the negative terminal of the converter.

In an preferred embodiment, the electrical energy storage comprises a coupled inductor or flyback converter adapted to provide a flyback converter stage. In some embodiments, the flyback converter is a DC/DC converter comprising two inductors adapted to convert DC from a first voltage to a second voltage.

In other preferred embodiments, the voltage converter is integrated into the electrical energy storage means, preferably by an inductor split, wherein two inductors convert DC/DC between a first voltage and a second voltage.

The voltage converter may comprising a first stage converter and a second stage converter wherein • the first stage converter may be connected to the power input to receive low voltage current and may be configured to convert the low voltage current into a medium voltage current, and

• the second stage converter may be electrically connected to the first stage converter to receive the medium voltage current and may be configured to convert the medium voltage current into said high current voltage, and wherein the second stage converter may be electrically connected to said two high voltage output terminals.

In an embodiment, the first stage converter may comprise a first inductor, a first diode, a first transistor and a first capacitor, wherein

• the first inductor and the first diode may be serially connected with the first inductor connected to the power input having positive polarity, and the first diode has an anode and a cathode and may be arranged with its anode connected to the first inductor;

• the first transistor may has a gate (G), a drain (D) and a source (S) where current may be conducted between the drain (D) and the source (S) terminal upon an electrical input provided to the gate (G), the drain (D) may be connected to said serial connection in between the first inductor and the first diode, and the source (S) may be connected to the power input having negative polarity;

• the first capacitor may be connected to said serial connection at the cathode side of the first diode and connected to the power input having negative polarity.

The second stage converter may comprise a second inductor, a second diode, a second transistor and a second capacitor, wherein

• the second inductor and the second diode may be serially connected with the second inductor connected to a terminal of the first stage converter having positive polarity, and the second diode has an anode and a cathode and may be arranged with its anode connected to the second inductor;

• the second transistor may has a gate (G), a drain (D) and a source (S) where current may be conducted between the drain (D) and the source (S) terminal upon an electrical input provided to the gate (G), the drain (D) may be connected to said serial connection in between the second inductor and the second diode, and the source (S) may be connected to the power input (4) having negative polarity;

• the second capacitor may be connected to said serial connection at the cathode side of the second diode and connected to the power input having negative polarity.

In another preferred embodiment of the invention, the thruster has an anode and a cathode, and wherein the anode may be connected to that of the high voltage output terminals having positive polarity and the cathode may be connected to that of the high voltage output terminals through the switch.

The switch may be a MOSFET transistor, but other types of transistors such as MEMS, BJT and IGBT may be used to obtain the present invention.

In some embodiments, said switch configured to operate in said connected mode and in said disconnected mode wherein no current may be conducted from the voltage converter to the electrical powered thruster at a frequency being between 1 and 400 Hz, such as between 1 and 200 Hz, preferably between 1 and 100 Hz.

In some embodiments, the power conversion system may further comprises a controller for sending control signals at least to said switch.

Preferably, the satellite is a miniaturized satellite, and the volume of the satellite may be smaller than 1 000 cm ³ .

In other embodiments, the satellite is larger than 1000 cm ³ .

The satellite may comprises a frame work in the form of a frame construction, wherein said frame work may comprises a structural frame at least in one end of said satellite connected to said frame construction of said satellite, and wherein at least a part of said structural frame may be solid, such as at least 50%, such as at least 70%, such as at least 95%. In other embodiments, the structural frame(s) of said satellite connected to said frame construction of said satellite may be solid.

Moreover, said structural frame(s) may provide(s) a void and wherein at least a part of the power conversion system may be contained within the void.

In some preferred embodiments, the satellite may further comprising at least two thrusters and a wherein the power conversion system may comprising a controllable gate configured to connect selective one of the thrusters to be powered. As an example, having several thrusters to be activated is achieved by having several independent switches in parallel to each other.

The invention relates in a second aspect of the invention, to a stacked circuit board for a miniaturize satellite, comprising electrical powered thrusters, said stacked circuit board may comprising :

• at least two circuit boards configured to be stacked and wherein each circuit board may has a thickness smaller than 1.6 mm such as smaller than 1.4 mm and larger than 0.1 mm;

• a SMD connector, such as a mezzanine connector, comprising a female part arranged on one of the circuit boards and a male part arranged on another of the circuit boards and may be configured to provide an electrical connection between two circuit boards when the female part and the male part are mechanically connected, said SMD connecter may be further arranged to provide and retain the stacked configuration;

• at least a part of a power conversion system for powering electrical powered thrusters; wherein said stacked circuit board may be adapted to fit into a void defined by an inner circumference of a frame work of the satellite.

This is particularly, but not exclusively advantageous as the stacked circuit board minimises the volume occupied by the electric propulsion system by being placed inside a void inside the structural frame of the satellite.

In some embodiments, the stacked circuit board comprising at least three circuit boards, and wherein a gap between two neighbouring circuit boards may be larger than a gap between two other neighbouring circuit boards. In a third aspect of the invention, the power conversion system may comprise a stacked circuit board.

The first, second and third aspect of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The present invention and in particular preferred embodiments according to the invention will now be described in more details with regard to the accompanying figures. The figures show ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 shows a first embodiment of an electrical circuit for providing electrical power to electrical powered thrusters in a satellite;

Figure 2 shows a second embodiment of an electrical circuit for providing electrical power to electrical powered thrusters in a satellite;

Figure 3 shows a third embodiment of an electrical circuit for providing electrical power to electrical powered thrusters in a satellite;

Figure 4 is divided into Figure 4a and 4b, which shows a first and second embodiment of a stacked circuit board for a satellite without any electrical components illustrated;

Figure 5 shows two circuit boards for a satellite without any electrical components illustrated;

Figure 6 shows two circuit boards for a satellite seen from another angle without any electrical components illustrated; Figure 7 shows another embodiment of an unstacked circuit board for a satellite arranged in a structural frame of a satellite;

Figure 8 shows an embodiment of a stacked circuit board for a satellite arranged in a void in structural frame of a satellite;

Figure 9 shows a satellite and a typical frame work for a satellite.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to fig. 1, an embodiment of the invention will now be detailed. In general, the invention relates to a satellite 1 comprising an electrically-powered thruster 2 and a power conversion system 3 for providing electrical power to the electrically-powered thruster; and

Figure 10 an embodiment of a flyback converter.

The satellite 1 is typically a so-called "small satellite", "a miniaturized satellite" or a "nanosatellite", typically with a weight of 500 kg or below. Sometimes the satellite 1 may be defined as a "microsatellite" or "microsat" with a weight of 100 kg or below. Other times the satellite 1 may even be referred to as a "nanosatellite" with a weight of 10 kg or below. The disclosed satellite types is not to be construed as being limiting, as other types of satellites may be used.

It is to be understood, that the satellite 1 is not necessarily a small, low weight satellite. Thus, in some embodiments, the weight of the satellite 1 may exceed 500 kg.

The electrically-powered thruster is an electric propulsion thruster, specifically an electromagnetic thruster, more specifically a vacuum arc thruster. The electrically powered thruster may also be an electrostatic or electrothermal thruster.

The power conversion system 3 comprises a power input 4 for inputting low voltage current with different polarity, typically being a DC current. The power conversion system 3 further comprising a voltage converter 5, which is electrically connected to the power input 4 to receive low voltage current and being configured to convert low voltage current into high voltage current. In preferred embodiments, the low voltage current has a voltage of 5 V DC and the voltage current has a voltage of 500 DC, but the invention is not limited to these levels of voltages.

As will become apparent from the following description, the level of the high voltage output is selected in accordance with the input voltage requirement for the thruster.

The voltage converter 5 further comprises two high voltage output terminals 6a, 6b with different polarity, whereby the output terminals 6a, 6b serves a DC current supply for the thruster. One of the high voltage output terminals 6a is electrically connected to the electrical powered thruster 2, to provide high voltage current to the electrical powered thruster 2.

The thrust provided by the thruster is proportional to the electrical power input the thruster, which may be evaluated by:

Where P is the electrical power consumed by the thruster, U is the voltage potential to which the thruster is connected, I is the current fed into the thruster, t is the time, F is the thrust force produced, q is the thruster efficiency, g is standard gravitational acceleration on Earth, and I _sp is the specific impulse of the propulsion system. As indicated, the voltage potential U is approximated to be constant over time, whereas the current is varying with time. Thus, by this, it can be seen that the thrust provided by the thruster can be controlled by varying the current I.

In preferred embodiment, the voltage potential for the thruster is provided by an electrical energy storage 9 as shown inter alia in fig. 1, that is the power conversion system 3 further comprises an electrical energy storage 9, which is electrically connected so that at least a part of the high voltage current is stored in the electrical energy storage 9. By this, the voltage conversion system 5 may be viewed as a source of high voltage electrical energy, which is stored in the electrical energy storage 9.

The electrical energy storage 9 can be arranged so as to be combined with the voltage converter 5 as illustrated in fig. 1 and/or as a separate electrical energy storage 9 electrically connected to said voltage converter as illustrated in fig. 2.

The power conversion system 3 further comprises a switch 7 electrically connected to the other one of the high voltage output terminals 6b of the voltage converter 5 and has an output terminal 8 connected to said electrical powered thruster 2, wherein the switch 7 being configured to operate in a connected mode wherein a current is conducted from the voltage converter 5 to the electrical powered thruster 2 and a disconnected mode wherein no current is conducted from the voltage converter 5 to the electrical powered thruster 2. Said two modes being selective in response to the switch 7 receiving a control signal. The differentiation between connected mode and disconnected mode makes it possible to control firing of the thruster, by such as a controller sending a control signal to the switch 7.

By this configuration of electrical energy storage 9, voltage converter 5 and the switch 7 may be operated with the aim to store electrical energy in the electrical energy storage 9, whereas the thruster may be operated with the aim of providing a desired thrust. This has the advantage that operation of the thruster can be made highly independent of provision of electrical energy to the electrical energy storage 9. It is to be mentioned that operation of the thruster as per desire may have to be made in relation to the amount of electrical energy stored in the electrical energy storage 9.

As presented in the above equation for the power consumed by the thruster, the variation over time of the current I may be viewed as a control parameter, and as indicated in fig. 1, the input to the switch 7 may be a stepwise on-off variation with time. Thus, the current and thereby the power consumed can be controlled by varying the frequency and the duration of the on and off periods. It is to be noted that the duration of an on period may not need to be the same as the duration of the off period.

In preferred embodiment, the electrical energy storage is electrically connected so that at least a part of power at the two high voltage output terminals 6a, 6b is provided by the electrical energy storage 9.

In another preferred embodiment, the electrical energy storage converts low voltage to high voltage, from between 2 V and 5 V into between 400 V and 900 V, more particularly, the electrical energy storage converts low voltage to high voltage from between 3.3 V and 12 V into between 500 V and 800 V.

Preferably, in some embodiments, the switch 7 is controlled so that the power consumed by the thruster is in the range 20.0 watt to 0.01 watt such as between 10.0 w and 0.05 w, preferably 0.25 watts to 1.0 watts. However, it is noted that the power consumed by the thruster is also influenced by the type of thruster used.

Thrusters usable in connection with the present invention typically requires a pulsed voltage potential to be applied to electrical terminals of the thrusters and this pulsed voltage potential is provided by the input to the switch 7. A thruster useable in connection with the present invention typically has a polarity (anode cathode), however, the switch 7 may in some embodiments, be connected to the positive terminal of the converter 5, or the switch 7 may in other embodiments, be connected to the negative terminal of the converter 5.

Although, the voltage converter 5 may be designed to convert low voltage current into high voltage current in a single stage, it may be advantageous to convert the low voltage into high voltage in two or more stages, which provides customisability for different power buses on different satellites. One such example is illustrated in fig. 3, wherein the voltage converter 5 comprises a first stage converter 10 and a second stage converter 11, and wherein the first stage converter 10 is connected to a power input to receive low voltage current and is configured to convert the low voltage current into a medium voltage current. The second stage converter 11 is electrically connected to the first stage converter 10 to receive the medium voltage current and is configured to convert the medium voltage current into said high current voltage, and wherein the second stage converter is electrically connected to said two high voltage output terminals 6a, 6b. Sometimes a stage converter may be described as a power or boost converter.

In a preferred embodiment, the power input to the first stage converter 10 is 5 volts, and the first stage converter 10 is configured to provide as output 12 volts to the input of the second stage converter 11. The second stage converter 11 is in a preferred embodiment configured to output 500 volts.

Reference is made to fig. 3 schematically illustrating a preferred embodiment of a first stage converter 10. The illustrated first stage converter 10 comprises a first inductor 12, a first diode 13, a first transistor 14 and a first capacitor 15, wherein the first inductor 12 and the first diode 13 are serially connected with the first conductor 12 connected to the power input 4 having positive polarity, and the first diode 13 has an anode and a cathode and is arranged with its anode connected to the first inductor 12. The first transistor 14 has gate G, a drain D and a source S where current is conducted between the drain D and the source S terminal upon an electrical input provided to the gate G, the drain D is connected to said serial connection in between the first inductor 12 and the first diode 13, and the source S is connected to the power input 4 having negative polarity. The first capacitor

15 is connected to said serial connection at the cathode side of the first diode 13 and connected to the power input 4 having negative polarity.

The second stage converter 11 comprises a second inductor 16, a second diode 17, a second transistor 18 and a second capacitor 19, wherein the second inductor

16 and the second diode 17 are serially connected with the second inductor 16 connected to a terminal of the first stage converter 10 having positive polarity, and the second diode 17 has an anode and a cathode and is arranged with its anode connected to the second inductor 16. The second transistor 18 has gate G, a drain D and a source S where current is conducted between the drain D and the source S terminal upon an electrical input provided to the gate G, the drain D is connected to said serial connection in between the second inductor 16 and the second diode 17, and the source S is connected to the power input 4 having negative polarity. The second capacitor 19 is connected to said serial connection at the cathode side of the second diode 17 and connected to the power input 4 having negative polarity. It is noted that a common ground is used for the embodiment shown in fig. 3. Further, the first and second inductors 12, 16 may be of a type comprising a conductor coiled around a ferrite core.

Both the first and the second stage converters 10, 11 are controlled by an on-off signal applied to the first and the second transistors 14, 18, and the actual voltage conversion of the two stage converters 10, 11 is influenced by inter alia the frequency of the on-off signal and the selection of the electrical components of the voltage converters 10, 11. The control signal for the first and the second transistors 14, 18 may be provided by a controller, e.g. as disclosed in connection with fig. 3. In embodiments, where the control signal for the semiconductor switches 14, 18 is provided by a controller, drive gates may be used to convert and output signal from a controller to an input to the semiconductor switches 14, 18. As an alternative to the use of a controller, a stable multivibrator may be implemented in the electrical circuit to provide the control signal.

In some preferred embodiments, the thruster 2 has an anode and a cathode, and the anode is connected to the high voltage output terminal of 6a, 6b having positive polarity and the cathode is connected to the high voltage output terminal of 6a, 6b through the switch 7 (as shown in fig. 3). In other embodiments, the anode may be electrically connected to the high voltage output terminal of 6a, 6b having positive polarity through the switch 7, while the cathode is electrically connected to the high voltage output terminal of 6a, 6b.

As disclosed herein, the switch 7 is in preferred embodiments a MOSFET transistor, but other types of transistors such as MEMS, BJT, and IGBT can also be used to obtain the present invention. Depending on the positioning regarding polarity of the switch, either a NPN or a PNP type is used.

In some embodiments, said switch (7) configured to operate in said connected mode and in said disconnected mode wherein no current is conducted from the voltage converter (5) to the electrical powered thruster at a frequency being between 1 and 400 Hz, such as between 1 and 200 Hz, preferably between 1 and 100 Hz.

In other preferred embodiments, the satellite disclosed herein is a miniaturized satellite. The volume of the miniaturized satellite is in some embodiments smaller than 1 000 cm ³ , more preferably smaller than 375 cm ³ , more preferably smaller than 250 cm ³ .

With reference to fig. 9, one embodiment of the invention is illustrated. The satellite 27 in fig. 9 comprises a frame work (23) in the form of a frame construction and is a typical frame construction for a satellite 27.

With reference to fig. 8, a structural frame from one end of the frame work (23) of the satellite is illustrated, with a void (24) delimited by one or more frame elements (26) and wherein at least a part of the power conversion system 3 is contained within the void (24). The size of the void is predetermined to fit specifically at least the part of the power conversion system 3.

Reference is made to fig. 4a, 4b illustrating a stacked circuit board for a satellite comprising electrical powered thrusters (not shown). The stacked circuit board 25 is preferred in multiple embodiments of the invention and comprises at least two circuit boards configured to be stacked and wherein each circuit board has a thickness smaller than 1.6 mm such as smaller than 1.4 mm and larger than 0.1 mm. It is noted, that the thickness here considered is the thickness of the circuit board itself, not including electrical components mounted on the circuit board 21. A stacked circuit board is defined as the majority of both circuits boards being stacked are overlapping, such as at least 50%, such as at least 60%, such as at least 85%, as illustrated in figure 4b. The thickness of a circuit board is measured as the thickness of the circuit board 21 without any electrical components.

The circuit board further comprises at least one SMD connector 22, such as a mezzanine connector, comprising a female part arranged on one of the circuit boards and a male part arranged on another of the circuit boards and being configured to provide an electrical connection between two circuit boards when the female part and the male part are mechanically connected, said SMD connecter(s) 22 being further arranged to provide and retain the stacked configuration. By a stacked configuration is meant that the SMD connector(s) 22 retain the individual circuit boards on top of each other at least to a degree fulfilling the definition of stacked as disclosed above.

The circuit board further comprises at least a part of a power conversion system for powering the electrical powered thrusters, wherein said stacked circuit board is adapted to fit into a void defined by an inner circumference of a frame work of the satellite. The frame work is typically an element, which provide at least some of mechanical strength to the satellite.

In some embodiments, the stacked circuit board comprises at least three circuit boards, and wherein a gap between two neighbouring circuit boards is larger than a gap between two other neighbouring circuit boards.

In preferred embodiments, the power conversion system 3 comprises a stacked circuit board (25).

Reference is made to fig. 10 schematically illustrating another preferred embodiment of a flyback converter. The illustrated converter comprises a coupled inductor 120, a diode 13, a transistor 14 and a capacitor 15, wherein the coupled inductor 120 and the diode 13 are serially connected at the output end of the coupled inductor 120. The diode 13 has an anode and a cathode and is arranged with its anode connected to the output end of the coupled inductor 120. The transistor 14 has a gate G, a drain D and a source S where current is conducted between the drain D and the source S terminal upon an electrical input provided to the gate G, the drain D is connected to the input end of the coupled inductor 120, and the source S is connected to the power input. The capacitor 15 is connected to said serial connection at the cathode side of the diode 13. In some preferred embodiments, the thruster 2 has an anode and a cathode, and the anode is connected to the cathode of the diode 13 having positive polarity and the cathode of the thruster 2 is connected to the ground G, through D of the switch 7.

In the following, preferred embodiments and aspects of the invention are presented as a list of items: Item 1. A satellite 1 comprising an electrical powered thruster 2 and a power conversion system 3 for providing electrical power to the electrical powered thruster, said conversion system comprising:

• a power input 4 for inputting low voltage current with different polarity;

• a voltage converter 5 and an electrical energy storage 9, said voltage converter being 5 electrically connected to the power input 4 to receive low voltage current and being configured to convert low voltage current into high voltage current, the voltage converter 5 having two high voltage output terminals 6a, 6b with different polarity, wherein one of the high voltage output terminals 6a is connected to the electrical powered thruster, and the electrical energy storage 9 being electrically connected so that at least a part of the high voltage current is stored in the electrical energy storage 9;

• a switch 7 electrically connected to other one of the high voltage output terminals 6b of the voltage converter 5 and having an output terminal 8 connected to said electrical powered thruster 2, wherein the switch 7 being configured to operate in a connected mode wherein a current is conducted from the voltage converter 5 to the electrical powered thruster 2 and a disconnected mode wherein no current is conducted from the voltage converter 5 to the electrical powered thruster, said two modes being selective in response to the switch 7 receiving a control signal.

Item 2. A satellite according to Item 1, wherein the electrical energy storage is electrically connected so that at least a part of power at the two high voltage output terminals 6a, 6b is provided by the electrical energy storage 9.

Item 3. A satellite according to Items 1 or 2, wherein the switch is controlled so that the power consumed by the thruster is in the range 20.0 watts to 0.01 watts such as between 10.0 watts and 0.05 watts, preferably 0.25 watts to 1.0 watts.

Item 4. A satellite according to any one of Items 1 - 3, wherein the switch 7 is connected to the positive terminal of the converter 5.

Item 5. A satellite according to any one of Items 1 - 4, wherein the switch 7 is connected to the negative terminal of the converter 5. Item 6. A satellite according to any one of Items 1 - 5, wherein the voltage converter 5 comprising a first stage converter 10 and a second stage converter 11 wherein

• the first stage converter 10 is connected to the power input 4 to receive low voltage current and is configured to convert the low voltage current into a medium voltage current, and

• the second stage converter 11 is electrically connected to the first stage converter 10 to receive the medium voltage current and is configured to convert the medium voltage current into said high current voltage, and wherein the second stage converter is electrically connected to said two high voltage output terminals 6a, 6b.

Item 7. A satellite according to Item 6, wherein the first stage converter 10 comprising a first inductor 12, a first diode 13, a first transistor 14 and a first capacitor 15, wherein

• the first inductor 12 and the first diode 13 are serially connected with the first inductor 12 connected to the power input 4 having positive polarity, and the first diode 13 has an anode and a cathode and is arranged with its anode connected to the first inductor 12;

• the first transistor 14 has a gate G, a drain D and a source S where current is conducted between the drain D and the source S terminal upon an electrical input provided to the gate G, the drain D is connected to said serial connection in between the first inductor 12 and the first diode 13, and the source S is connected to the power input 4 having negative polarity;

• the first capacitor 15 is connected to said serial connection at the cathode side of the first diode 13 and connected to the power input 4 having negative polarity.

Item 8. A satellite according to Items 6 or 7, wherein the second stage converter 11 comprising a second inductor 16, a second diode 17, a second transistor 18 and a second capacitor 19, wherein • the second inductor 16 and the second diode 17 are serially connected with the second inductor 16 connected to a terminal of the first stage converter 10 having positive polarity, and the second diode 17 has an anode and a cathode and is arranged with its anode connected to the second inductor 16;

• the second transistor 18 has a gate G, a drain D and a source S where current is conducted between the drain D and the source S terminal upon an electrical input provided to the gate G, the drain D is connected to said serial connection in between the second inductor 16 and the second diode 17, and the source S is connected to the power input 4 having negative polarity;

• the second capacitor 19 is connected to said serial connection at the cathode side of the second diode 17 and connected to the power input 4 having negative polarity.

Item 9. A satellite according to any one of Items 1 - 8, wherein thruster 2 has an anode and a cathode, and wherein the anode is connected to that of the high voltage output terminals 6a, 6b having positive polarity and the cathode is connected to that of the high voltage output terminals 6a, 6b through the switch 7.

Item 10. A satellite according to any one of Items 1 - 9, wherein the switch 7 is a MOSFET transistor.

Item 11. A satellite according to any one of Items 1 to 10, wherein the satellite is a miniaturized satellite.

Item 12. A satellite according to Item 11, where the volume of the satellite is smaller than 1.000 cm ³ .

Item 13. A satellite according to any of the Items 1 - 12, wherein the power conversion system 3 further comprises a controller 20 for sending control signals at least to said switch 7. Item 14. A satellite according to any one of Items 1 - 13, wherein the satellite comprises a frame work 12 in the form of a frame construction, and wherein said frame work 23 comprises a structural frame at least in one end of said satellite connected to said frame construction of said satellite, and wherein at least a part of said structural frame is solid, such as at least 50%, such as at least 70%, such as at least 95%.

Item 15. A satellite according to any one of Items 1 - 14, wherein the structural frame(s) of said satellite connected to said frame construction of said satellite is solid.

Item 16. A satellite according to Item 14 or 15, wherein said structural frame(s) provides a void 24 and wherein at least a part of the power conversion system 3 is contained within the void 24.

Item 17. A satellite according to any of one of Items 1 - 16, further comprising at least two thrusters and a wherein the power conversion system comprising a controllable gate configured to connect selective one of the thrusters to be powered.

Item 18. A satellite according to any of Items 1 - 17, wherein said switch 7 configured to operate in said connected mode and in said disconnected mode wherein no current is conducted from the voltage converter 5 to the electrical powered thruster at a frequency being between 1 and 400 Hz, such as between 1 and 200 Hz, preferably between 1 and 100 Hz.

Item 19. A stacked circuit board for a miniaturize satellite comprising electrical powered thrusters, said stacked circuit board comprising:

• at least two circuit boards configured to be stacked and wherein each circuit board has a thickness smaller than 1.6 mm such as smaller than 1.4 mm and larger than 0.1 mm;

• a SMD connector, such as a mezzanine connector, comprising a female part arranged on one of the circuit boards and a male part arranged on another of the circuit boards and being configured to provide an electrical connection between two circuit boards when the female part and the male part are mechanically connected, said SMD connecter being further arranged to provide and retain the stacked configuration;

• at least a part of a power conversion system for powering electrical powered thrusters; wherein said stacked circuit board is adapted to fit into a void defined by an inner circumference of a frame work of the satellite.

Item 20. A stacked circuit board according to Item 19, wherein the stacked circuit board comprises at least three circuit boards, and wherein a gap between two neighbouring circuit boards is larger than a gap between two other neighbouring circuit boards.

Item 21. A satellite according to any one of Items 1-18, wherein the power conversion system comprises a stacked circuit board according to any one of Items 19-20.

Item 22. A satellite with electrical powered thrusters, comprising a stacked circuit board 1, said stacked circuit board comprising:

• at least two circuit boards adapted to be stacked and wherein each circuit board has a thickness smaller than 1.6 mm such as smaller than 1.4 mm and larger than 0.1 mm;

• an SMD connector, such as a mezzanine connector, comprising a female part arranged on one of the circuit boards and a male part arranged on another of the circuit boards and being configured to provide an electrical connection between two circuit boards when the female part and the male part are mechanically connected, said SMD connector being further arranged to provide and retain the stacked configuration;

• at least a part of a power conversion system for powering the electrical powered thrusters wherein said stacked circuit board is adapted to fit into a void defined by an inner circumference of a frame work of the satellite.

Item 23. A satellite with electrical powered thrusters according to Item 22, wherein the stacked circuit board comprises at least three circuit boards, and wherein a gap between two neighbouring circuit boards is larger than a gap between two other neighbouring circuit boards.

Item 24. A satellite 1 according to claim Item 1, wherein the conversion system comprises a flyback converter.

Item 25. A satellite according to Item 24, wherein the flyback converter is integrated into the the electrical energy storage.

Item 26. A satellite according to Item 1, wherein the voltage converter 5 is a flyback converter.

Item 27. A satellite according to Item 26, wherein the flyback converter is integrated into the electrical energy storage.

The individual elements of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way such as in a single unit, in a plurality of units or as part of separate functional units. The invention may be implemented in a single unit, or be both physically and functionally distributed between different units and processors.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous. LIST OF REFERENCE SYMBOLS USED

Satellite

2 Electrical powered thruster

3 Power conversion system

4 Power input

5 Voltage converter

6 Voltage output terminals

7 Switch

8 Output terminal (of switch)

9 Electrical energy storage

10 First stage converter

11 Second stage converter

12 First inductor

13 First diode

14 First transistor

15 First capacitor

16 Second inductor

17 Second diode

18 Second transistor

19 Second capacitor

20 Controller

21 Circuit board

22 SMD connector

23 Frame work

24 Void

25 Stacked circuit board

26 Frame elements

27 Satellite