DE202013000114U1 - Hybrid power supply - Google Patents

Abstract

Hybrid power supply, characterized in that the flight control of a UAVs from the drive battery (or a generator) and a separate energy storage is supplied, which is automatically charged by the Flugakku (or generator).

Description

In the field of UAVs (Unmanned Aerial Vehicles) or RC model aircraft, more and more environmentally friendly and quiet electric drives are used. The electric motors are powered by powerful batteries (usually based on lithium, eg lithium polymer "LiPo" or lithium iron phosphate "LiFePO4"). In order to produce the necessary power and keep the currents within reasonable limits, high voltages are used (in the range of about 14 volts up to 60 volts).

For the control of these flying objects components from the RC model building are used (servomotors = servos, receivers, autopilots), which work with a low voltage (in the range of 6 volts up to 8.4 volts). For the supply of the flight control therefore own batteries are usually used. This drives up the weight and means an extra effort when charging the batteries. In order to dispense with additional batteries for the control, so-called BEC systems are currently used. BEC stands for "Battery Elimination Circuit". A BEC is a linear or clocked voltage regulator that generates a lower voltage for the receiving system or flight control from the high flight battery voltage.

• 1. Bei Ausfall des Flugakkus (z. B. durch Zellenbruch oder Tiefentladung) ist das Flugobjekt nicht mehr steuerbar, weil das BEC-System keine Energie mehr liefert.
• 2. Ein BEC-System kann nur einen geringen maximalen Strom zur Verfügung stellen. Bei einem Linear-BEC wird die Differenz von Ein- zu Ausgangsspannung in Wärme umgewandelt. Da die Wärmeenergie direkt proportional zum Strom ist, ist der entnehmbare Strom sehr klein (bis max. 3 A).
• 3. Bei einem getakteten BEC entsteht weniger Verlustwärme und das BEC kann mehr Strom liefern. Allerdings ist auch hier der Strom begrenzt und der Wirkungsgrad hängt stark von der entnommenen Leistung ab.
• 4. Die Rudermaschinen in einem Flugobjekt haben einen sehr großen Strombereich. Der mittlere Strom liegt (je nach Modell) z. B. bei nur 4 Ampère. Der Spitzenstrom im Anlaufmoment der Servomotoren liegt in dem Beispiel aber durchaus bei bis zu 30 oder 40 Ampère. Man müsste einen getakteten Regler (BEC) also für hohe Ströme auslegen (30 A–40 A). Beim mittleren Strom von 4 A ist der Wirkungsgrad eines solchen Wandlers aber sehr schlecht. Abgesehen davon wird ein 40 A BEC recht groß und vor allen Dingen teuer.

This results in significant disadvantages:

• 1. If the flight battery fails (eg due to cell breakage or deep discharge), the flying object can no longer be controlled because the BEC system no longer supplies any energy.
• 2. A BEC system can only provide a small maximum current. In a linear BEC, the difference between input and output voltage is converted into heat. Since the heat energy is directly proportional to the current, the removable current is very small (up to a maximum of 3 A).
• 3. With a cycled BEC there is less heat loss and the BEC can deliver more power. However, even here the power is limited and the efficiency depends strongly on the power taken.
• 4. The rudders in a flying object have a very large power range. The average current is (depending on the model) z. B. at only 4 amps. The peak current in the starting torque of the servomotors is in the example but certainly up to 30 or 40 amps. One would have to design a clocked controller (BEC) for high currents (30 A-40 A). At the average current of 4 A, the efficiency of such a converter is very bad. Apart from that, a 40 A BEC will be quite big and, above all, expensive.

Troubleshooting

With the invention it is achieved that the flight control in addition to the actual drive from the Flugakku can be fed (ie from a high voltage). Nevertheless, the control is fully maintained in the event of failure of the flight battery. For this purpose, a clocked DC / DC converter with relatively low power is used. The converter is followed by a charger, which charges a small high-current capable (eg 2-cell) lithium polymer battery. The flight control is powered by this battery, which is constantly recharged by the charger powered by the flight battery via the DC / DC converter.

An embodiment of the invention will be explained with reference to the drawing 1:

LIST OF REFERENCE NUMBERS

1a

Flugakku oder Generator (z. B. RAM Air Turbine)

1b

Isolierender DC/DC-Wandler

1c

Ausgangsspannung Wandler

1d

LiPo-Ladegerät

1e

Energiespeicher (LiPo-Akku)

1f

Equalizer für Zellen-Balancing

1g

Überwachungselektronik und Anzeige

1h

Flugsteuerung

Hybrid Power Supply - Sketch 1

1a

Flight battery or generator (eg RAM Air Turbine)

1b

Insulating DC / DC converter

1c

Output voltage converter

1d

LiPo charger

1e

Energy storage (LiPo battery)

1f

Equalizer for cell balancing

1g

Monitoring electronics and display

1h

flight control

From a primary voltage source (flight battery or generator ( 1a )) is a clocked and isolated DC / DC converter ( 1b ). The converter generates from the high input a small output voltage ( 1c ). The DC / DC converter serves as the basic power supply of the control unit and only has to provide the required average current. The converter is a charger with CC / CV charging characteristic downstream ( 1d ). The charger in turn powers or charges a (eg) 2-cell lithium polymer battery of low capacity ( 1e ). This battery serves as a low-impedance energy storage and covers the high current peaks of the control system. In addition, the system contains an equalizer ( 1f ), which ensures that the two cells of the lithium polymer battery (energy storage) always have the same voltage level. The LiPo battery ( 1e ) now supplies the flight control ( 1h ). It's all done by electronics ( 1g ), which among other things visually displays all states.

Achieved benefits

With the invention it is achieved that the flight control can be completely fed from the flight battery (ie from a high voltage). The weight of the overall system is very low. In case of failure of the flight battery, the flying object can land safely because it is supplied during this time from the energy storage.

• 1. Bei Ausfall des Flugakkus (oder eines Generators) bleibt das Flugobjekt voll steuerbar – und zwar so lange, bis der Energiespeicher leer ist.
• 2. Durch den niederohmigen Energiespeicher können sehr hohe Impulsströme abgegeben werden.
• 3. Dadurch, dass der DC/DC-Wandler nur den Grundstrom und nicht die Stromspitzen liefern muss, ist das System klein und leicht und hat einen sehr hohen Wirkungsgrad, da der Wandler immer mit einem optimalen Wirkungsgrad arbeitet.
• 4. Dadurch, dass der DC/DC-Wandler isoliert ist, können auch Doppelstromversorgungen eingesetzt werden, da die beiden Energiesysteme keine elektrische Verbindung zueinander haben. Durch die Parallelschaltung mehrerer Systeme sind alle zu speisenden Anwendungen elektrisch isoliert.
• 5. Durch die integrierte Ladeschaltung mit Equalizer wird der Energiespeicher optimal überwacht, geschont und ist damit wartungsfrei.
• 6. Durch die Auslegung der Elektronik wird sichergestellt, dass der das Gesamtsystem im inaktiven Zustand (also ohne angeschlossenen Flugakku oder Generator) keinen Strom verbraucht und sich der Energiespeicher daher nicht schleichend entlädt.
• 7. Durch die Auslegung der Elektronik wird weiterhin sichergestellt, dass die Einzelzellen des Energiespeichers nicht zu 100% bis an die maximale Ladeschlussspannung geladen werden. Dadurch wird die Lebensdauer des Energiespeichers drastisch gesteigert, da der DOD-Wert (Depth Of Discharge) des Akkus sehr niedrig ist.
• 8. Durch die Auslegung der Elektronik kann der Anwender per Knopfdruck jederzeit den Ladezustand des Energiespeichers ablesen.

Very high current peaks of the servomotors are also covered by the energy storage without problems. Furthermore, the efficiency and thus the effectiveness of the system are very high, since the DC / DC converter can operate in the optimum range.

• 1. In case of failure of the flight battery (or a generator), the flying object remains fully controllable - and that until the energy storage is empty.
• 2. Due to the low-impedance energy storage very high pulse currents can be delivered.
• 3. The fact that the DC / DC converter only has to supply the base current and not the current peaks, the system is small and light and has a very high efficiency, since the converter always works with an optimal efficiency.
• 4. The fact that the DC / DC converter is isolated, double power supplies can be used, since the two energy systems have no electrical connection to each other. By connecting several systems in parallel, all applications to be fed are electrically isolated.
• 5. Thanks to the integrated charging circuit with equalizer, the energy storage device is optimally monitored, protected and thus maintenance-free.
• 6. The design of the electronics ensures that the entire system in the inactive state (ie without connected flight battery or generator) consumes no electricity and the energy storage therefore does not creep slowly.
• 7. The design of the electronics also ensures that the individual cells of the energy storage are not charged to 100% up to the maximum charge end voltage. This drastically increases the life of the energy storage device, as the DOD (Depth Of Discharge) of the battery is very low.
• 8. By designing the electronics, the user can read the charge status of the energy store at any time by pressing a button.

Claims (9)

Hybrid power supply, characterized in that the flight control of a UAVs from the drive battery (or a generator) and a separate energy storage is supplied, which is automatically charged by the Flugakku (or generator). Hybrid power supply according to one of the preceding claims, characterized in that a clocked DC / DC converter accepts the basic supply of the control unit and additionally feeds a charger. Hybrid power supply according to one of the preceding claims, characterized in that the separate energy storage with the charging circuit is charged permanently when the flight battery is connected or the generator is in operation. Hybrid power supply according to one of the preceding claims, characterized in that the charging circuit is followed by an equalizer, which ensures the identical single-cell voltage of the cells of the energy store. Hybrid power supply according to one of the preceding claims, characterized in that the system has no power consumption in the inactive state and the energy storage is not discharged creeping. Hybrid power supply according to one of the preceding claims, characterized in that the entire electronics and the energy storage are monitored (eg single cell voltage, temperature) and a malfunction is prevented. Hybrid power supply according to one of the preceding claims, characterized in that the energy storage is not loaded to 100% up to the end-of-charge voltage (small DOD value) and thus the number of charging cycles per se and the life of the energy storage can be extended considerably. Hybrid power supply according to one of the preceding claims, characterized in that the current state of charge of the energy storage is displayed by a simple button press. Hybrid power supply according to one of the preceding claims, characterized in that the DC / DC converter is galvanically isolated.

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