WO2011022850A2

WO2011022850A2 - Uninterruptible power supply for a medical administration appliance

Info

Publication number: WO2011022850A2
Application number: PCT/CH2010/000196
Authority: WO
Inventors: Michael Gentz
Original assignee: Tecpharma Licensing Ag
Priority date: 2009-08-27
Filing date: 2010-08-10
Publication date: 2011-03-03
Also published as: WO2011022850A3; CH701697A1

Abstract

An uninterruptible power supply for a medical administration appliance is specified. The power supply has a first energy source (210) and a rechargeable second energy source (120). A first current path (SP 1) is used to route energy from the rechargeable second energy source to a load (110). A second current path (SP 2) with a charging circuit (230) is used to route energy from the first energy source to the second energy source and thereby to charge the second energy source. In the normal mode, the load is supplied with energy essentially via the first current path from the rechargeable second energy source and the second energy source is charged via the second current path from the first energy source. A third current path (SP 3) from the first energy source to the load is designed to supply energy to the load from the first energy source in the event of failure of the second energy source or in the event of a reduced power output from the second energy source in an emergency mode.

Description

TITLE

Uninterruptible power supply for a medical administration appliance

TECHNICAL FIELD

The present invention relates to a power supply for a medical administration appliance and to a method for the operation of a power supply for such an administration appliance. Administration appliances of this kind are used for the regular administration of medicaments in liquid form, e.g. of insulin preparations.

PRIOR ART

The prior art discloses various kinds of medical administration appliances which administer a medicament to a patient by means of infusion. In this case, the administration of the medicament can be split particularly into small doses which are supplied to the patient over a relatively long period at certain intervals (e.g. every 10-30 minutes). In this context, it is advantageous and convenient for the patient to have portable appliances which perform such administration automatically and as far as possible without any further action by the patient. In this case, the appliance is permanently connected to the patient and has a reservoir for a medicament which is output in small volumes and at particular intervals and is supplied to the patient. By way of example, the medicament may be an insulin preparation for the treatment of diabetes.

A multiplicity of further medical administration appliances are known which are used in hospitals or even outside of these, for example, by medical staff or by patients themselves in order to administer medicaments, such as painkillers, or other substances, such as contrast agents for specific medical examinations, in precisely defined doses automatically over a particular time or at previously stipulated times.

Medical administration appliances of this kind frequently have a motor which drives a release apparatus in order to output a medicament from a container and thereby to supply it to the patient. In this case, the motor is frequently operated intermittently (i.e. with relatively long pauses between the periods in which the motor is activated) , with the release apparatus outputting a particular volume of the medicament from the container whenever the motor is activated.

A reliable and permanent power supply is essential for safe operation of the administration appliance. To this end, administration appliances from the prior art usually have at least one rechargeable and/or replaceable battery as an energy source. An interruption in the power supply can have dangerous consequences. When insulin is being administered, for example, an interruption can result in a dangerous undersupply of insulin. A critical state may arise, for example, if the output voltage from the battery drops below a particular value as a result of discharge and it is no longer possible to ensure an adequate power supply for the appliance. The energy source then needs to be replaced, which results in an interruption in the power supply. It is also possible for the energy source to be briefly isolated from the appliance, for example on account of external mechanical actions on the administration appliance, such as jolts, vibrations, etc. In addition, gradual failures in the energy source on account of corrosion at the contact points or general ageing of the battery with an associated reduced charge capacity, for example, are also possible. A particular problem when the energy source fails is the fact that this cannot be signalled to the user/patient by alarms (e.g. vibration alarm, buzzer, LED), since this would require the same energy source. To ensure safe operation and constant alerting despite such interruptions in the power supply for the administration appliance, appropriate precautions need to be taken.

WO 2008/049609 discloses an uninterruptible power supply for a medical appliance which has a primary cell and also a double-layer capacitor as an energy store. In the event of failure of the primary cell, the double-layer capacitor connected in parallel therewith briefly undertakes the supply of power to the appliance. This is possible only for a short period on account of the limited charge capacity of the double- layer capacitor, however. Furthermore, the double-layer capacitor requires a relatively large volume in the appliance and is expensive to manufacture.

WO 2008/121505 describes an insulin pump which has a replaceable battery and also a rechargeable lithium-ion battery for the power supply. In the normal mode, the replaceable battery supplies current to the pump. If it delivers too little voltage, however, the rechargeable battery undertakes the supply of power to the insulin pump.

On account of the intermittent operation of the motor, many administration appliances respectively require a relatively large amount of energy for a brief time, whereas afterwards only very little energy is required for a relatively long time until the next administration. There are thus pronounced current peaks. These current peaks place a considerable load on the replaceable battery, however, which has an adverse effect on the capacity thereof and hence on the operating time thereof.

US 2009/0069749 shows an infusion pump in which a rechargeable battery and a replaceable zinc-air battery are used. In this case, the power supply is designed such that the rechargeable battery supplies current to the infusion pump, while the replaceable zinc-air battery is used to charge the rechargeable battery. As a result, the current peaks do not affect the replaceable battery. However, failure of the rechargeable battery, for example on account of mechanical, external influences, corrosion or the like, cannot be compensated for by the replaceable battery, since this is not suitable for providing the requisite flow of current for operation.

ILLUSTRATION OF THE INVENTION It is an object of the invention to specify a power supply for a medical administration appliance which is tolerant toward faults in the power supply.

This object is achieved by a power supply having the features of Claim 1. Further embodiments are specified in the dependent claims.

The present invention thus provides a power supply for a medical administration appliance having an electrical load, having the following features:

The power supply has a first energy source and a rechargeable second energy source.

The power supply has a first current path in order to route energy from the rechargeable second energy source to the load, and the power supply has a second current path having a charging circuit in order to route energy from the first energy source to the second energy source and thereby to charge the second energy source.

The power supply is designed to supply energy to the load essentially from the rechargeable second energy source via the first current path and to charge the second energy source via the second current path from the first energy source, in the normal mode. In this context, the term "essentially" is to be understood to mean that in this operating state the flow of energy (the transmitted electrical power) from the second energy source to the load is much larger, at least by a factor of 5, than the flow of energy from the first energy source to the load.

Furthermore, the power supply has a third current path from the first energy source to the load which is designed to supply the load with energy from the first energy source in the event of failure of the second energy source or in the event of a reduced power output or output voltage from the second energy source in an emergency mode. In this case, the load can be supplied with energy completely from the first energy source

(e.g. in the event of complete failure of the second energy source) , or the first energy source can provide the load with a proportion of the required energy in addition to the second energy source (e.g. in the event of a partly reduced performance capability or output voltage for the second energy source) .

The fact that power is supplied from the second, rechargeable energy source in the normal mode conserves the first energy source, since in the normal mode this is loaded only by means of the relatively weak charging current. On the other hand, the fact that the load is supplied with energy via the third current path from the first energy source in the event of a drop in the performance capability of the second energy source means that the power supply for the administration appliance operates without interruption.

The first current path is preferably designed such that at peak load it admits at least one particular maximum flow of energy (maximum transmitted electrical power) , and the charging circuit limits the charging current in the second current path such that the maximum flow of energy in the first current path is much, at least by a factor of 5, larger than the maximum flow of energy in the second current path. The third current path is preferably designed such that it likewise admits a maximum flow of energy from the first energy source to the load which is larger than the maximum flow of energy, which is limited via the charging circuit, in the second current path.

The change from the normal mode to the emergency mode is preferably made continuously, i.e. the further the charge state of the second energy source and hence the output voltage thereof drops, the greater the extent to which the third current path undertakes the supply of energy to the load. The normal mode is adopted particularly when the second energy source reaches a charge state and hence an output voltage which exceeds a particular threshold. Above this threshold, the flow of energy is primarily via the first current path. Below this threshold, the third current path gradually undertakes an increasing portion of the supply of power to the load.

The power supply is preferably designed such that a change from the normal mode to the emergency mode is made purely passively. To this end, the first and third current paths preferably respectively have one or more components which are designed to prompt a change from the normal mode to the emergency mode continuously and without active control intervention. The components may be nonlinear resistor elements, in particular, i.e. nonlinear elements across which there is a voltage drop when a current flows and which are connected in series with the load. The nonlinear resistor elements may be one or more series-connected diodes, in particular, e.g. Schottky diodes, which produce a controlled and relatively low, nonlinearly current-dependent voltage drop in the forward direction. In order to ensure that in the normal mode the current flows primarily through the first current path, the components in the first and third current paths are advantageously designed such that in the normal mode the voltage drop across the components in the third current path is higher overall than across the components in the first current path.

Thus, no active elements such as charge controllers are used which, by way of example, would actively measure the output voltage of the second energy source and then make a (possibly abrupt) change to the emergency mode if necessary. This means that not only is the power supply simple and inexpensive to manufacture but there is also a reduction in the energy consumption of the power supply, said energy consumption being additionally present in the case of active circuits. In addition, this type of implementation has a high level of reliability, since only very few and simple components are needed, which results in a very low failure rate. The charging circuit is advantageously designed such that at least in the normal mode the charge voltage is permanently across the second energy source. This firstly reduces the complexity of the circuit design and secondly ensures that the second energy source is always in an optimum charge state. It is particularly advantageous if the charging circuit has exclusively passive elements. Preferably, the charging circuit is formed only by one or more electrical resistors. The charging circuit therefore has a very simple, reliable and inexpensive design.

In many cases, the output voltage from the first energy source will be lower in the normal mode than the output voltage from the second energy source. By way of example, the first energy source may be a normal alkaline battery (rated output voltage approximately 1.5 volts), while the second energy source may be an Li-ion or Li polymer battery (rated output voltage approximately 3.3-3.6 V or 3.6-4.0 V, depending on the electrochemistry) . In this case, the power supply preferably comprises a DC/DC converter in order to convert the output voltage of the first energy source into a higher voltage.

In order to maintain the power supply for the administration appliance in the long term too, the first energy source is advantageously a replaceable battery or a replaceable charged storage battery (i.e. likewise a chargeable battery) . In the case of discharge, the first energy source can then simply be replaced by a new one. Other embodiments are also conceivable, however: by way of example, a non- replaceable battery or a non-replaceable storage battery, which is possibly recharged by a suitable device, e.g. a charging station.

In one preferred embodiment, the power supply comprises a load shed switch which is designed to isolate the second energy source from the load in a further operating state. In this case, the load shed switch is advantageously formed by an electronic switch. This isolation can be effected automatically when the output voltage of the second energy source drops below a deep- discharge threshold. Deep discharge of the second energy source, which would inflict irreversible damage on the energy source, can be prevented thereby. Preferably, the load shed switch is designed such that it automatically (re) connects the second energy source to the load when the charge voltage exceeds a particular value.

Particular advantages arise if the load shed switch can be specifically (actively) operated by a control signal in order to isolate the second energy source from the load and/or to connect the second energy source to the load. To this end, the load shed switch preferably has an appropriate control connection. This allows the second energy source to be specifically isolated from the load, for example after the administration appliance has been manufactured, in order to minimize the discharge of said energy source during storage of the appliance. This allows the administration appliance to be stored for a relatively long period, that is to say over several years. A specifically operatable load shed switch is also advantageous independently of the rest of the design of the power supply as described above. In this respect, the present invention also relates to a power supply for a medical administration appliance having a load, wherein the power supply has the following features:

The power supply also comprises a load shed switch in order to isolate the second energy source from the load. In this case, the load shed switch can be actively operated by a control signal in order to isolate the second energy source from the load and/or to connect the second energy source to the load. To this end, it may have an appropriate control connection.

The present invention also comprises a medical administration appliance for administering a medicament in liquid form having a power supply of the type described above. In addition, the administration appliance will usually have a reservoir for the medicament and a release device for transmitting the drive motion of a motor to the reservoir. In particular, the invention also relates to a medical administration appliance having a load which comprises an electric motor and a motor controller, wherein the motor controller is designed to activate the motor intermittently in order to release the medicament incrementally. The charging circuit then produces a charging current which is smaller than the current in the first current path in the activation phases.

The administration appliance may be of modular design, wherein the valuable electronic components and the drive motor are accommodated in a reusable base module and the container for the medicament is accommodated in a disposable cartridge. It is then preferred for both the first and the second energy source to be accommodated in the base unit, that is to say for the administration appliance to have a housing unit which accommodates both the first energy source and the second energy source. This avoids interference-prone electrical contacts between base unit and cartridge. The invention also specifies a method for the operation of a medical administration appliance having a power supply and an electrical load. The power supply comprises a first energy source and a rechargeable second energy source. In the normal mode, the load is supplied with energy essentially from the second energy source, and the second energy source is charged from the first energy source. In the event of failure of the second energy source or in the event of a reduced power output from the second energy source, the load is supplied with energy from the first energy source in an emergency mode. In this case, in preferred embodiments, the load comprises an electric motor, wherein the electric motor is operated intermittently, so that activation phases, in which the motor is activated, have pauses between them, and the second energy source is charged with a charging current which is smaller than the current through the motor in the activation phases.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention are described below with reference to the drawings, which are used merely for the purpose of explanation and should not be interpreted as limiting, and in which: Figure 1 shows a schematic electrical circuit diagram of a power supply for a medical administration appliance;

Figure 2 shows a schematic electrical circuit diagram portion from the power supply in figure 1 with a detailed illustration of the load shed switch;

Figure 3 shows a graph with the current/voltage characteristics for the current paths SP 1 and SP 3 in the power supply in figure 1; and Figure 4 shows a state diagram for the load shed switch in the power supply in figure 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 shows an electrical circuit diagram of a preferred exemplary embodiment of an inventive power supply for a medical administration appliance. The power supply comprises a load circuit 100, charging electronics 200 connected thereto and a safety circuit 300, which is connected both to the load circuit 100 and to the charging electronics 200. The charging electronics 200 have a disposable battery 210 as first energy source. The load circuit 100 has a load 110 and a rechargeable battery 120 as second energy source. By way of example, the load 110 comprises a motor with a motor controller.

For the administration appliance to dispense medicaments, the motor controller drives the motor in order to output the medicament from the container. In this case, the motor can be operated by the motor controller intermittently, in particular, which means that it executes a certain number of (partial) revolutions at particular administration times in order to supply the patient with a particular volume of a medicament. In this case, only a small portion of the medicament which is present in the container is output in each case. The load 110 thus exhibits pronounced current peaks, during which an increased amount of energy is consumed. In addition to the motor, the load may have a multiplicity of other energy-consuming components, however, such as a computer unit, which stipulates the times and the volume of the administration, for example, an appliance display, an internal clock, etc. In addition, there could also be an alarm unit which warns the user when the medicament container is close to being empty, for example, or when the supply voltage drops below a particular value. A large number of further energy-consuming components of the load 110 is conceivable. The rechargeable battery 120 is a storage battery which has as little self-discharge as possible and a high power density, for example a lithium-ion or lithium polymer storage battery. In the normal mode of the administration appliance, it preferably has a charge state of less than approximately 80% of full charge, since a full charge of 100% can adversely affect the life of the storage battery. Depending on the embodiment of the rechargeable battery, the rated output voltage in this exemplary embodiment is 3.3-3.5 V (for phosphate-based lithium polymer storage batteries) or 3.6-4.0 V (for nickel, cobalt, manganese types), for example.

The load electronics have a load shed switch 130 which connects the rechargeable battery 120 to the load. The load shed switch 130, which is shown in detail in figure 2, is used to isolate and hence electrically insulate the rechargeable battery 120 completely from the load when needed. The load shed switch 130 can be implemented by any switch, for example a mechanical push or toggle switch, a relay, a reed relay, a pull- out seal or a membrane switch. A mechanical switch does not require any power, but instead needs to be operated manually by the user. Advantageously, the load shed switch 130 is therefore in the form of an electronic switch which, by way of example, comprises integrated switch and logic chips or else discrete metal oxide semiconductor field-effect transistors and passive R/C components .

In the present exemplary embodiment, the load shed switch 130 has an electronic switch 131 which has at least one first and a second connection, wherein the first connection is connected to the rechargeable battery 120. A further connection may be connected to the other pole of the battery 120 in order to apply an operating voltage to the electronic switch 130. The operating voltage for the switch 130 may alternatively have another voltage source (battery 210 or third sources) or else a control signal applied to it. The prior art discloses suitable electronic switches which have a practically negligible quiescent current, so that the switch 130 places practically no load on the battery 120 even over a relatively long time. The switch 131 has two switching states, a conducting state and an interrupting state. In the conducting state, the first and second connections of the switch 131 are connected to one another, and a current can flow from the first to the second connection of the switch 131 essentially without a voltage drop. In the interrupting state, the first and second connections have the highest possible resistance between them, so that a flow of current is prevented. The switch 131 can be actuated by a logic circuit 132 of the load shed switch 130 via an actuation line.

The logic circuit 132 has two inputs, which are identified by a and b in figure 2. Input a may be connected to a button, for example, which is mounted outside the administration appliance. By operating the button, a control signal SA (see figure 2) is sent to the logic circuit 132 of the load shed switch 130. This prompts the logic circuit 132 to open or close the switch 131.

The second input b of the logic circuit 132 is connected to the second connection of the switch 131, which is remote from the battery 120. The logic circuit 132 is designed such that it measures the voltage applied to its input b, which voltage forms a control signal SB (see figure 2) . If the voltage at the input b exceeds a particular value, the logic circuit 132 closes the switch 131. The switch 131 then thus adopts its conducting position. This functionality of the load shed switch 130 is explained in more detail below.

The load shed switch 130 has its second connection, which is remote from the battery 120, connected to the load 110 via a nonlinear, resistive electrical element 101. The resistive element 101 is in this case a diode, e.g. a Schottky diode, which has a nonlinear characteristic. A current flowing from the load shed switch 130 to the load 110 firstly encounters a much lower resistance than a current which is flowing in the opposite direction. The diode 101 thus has a nonconducting direction and a forward direction for the current, the forward direction being directed from the load shed switch 130 to the load 110. Secondly, there is a certain, relatively small voltage drop in the forward direction of the diode 101 too.

The output voltage of the replaceable battery 210 is lower than the rated voltage of the rechargeable battery 120. The output voltage of the replaceable battery 210 is converted to a higher operating voltage by means of a DC/DC converter 220. This operating voltage is a little above the typical operating point of the rechargeable battery 120. In other embodiments, the replaceable battery 210 may already have a sufficiently high voltage, which means that the DC/DC converter 220 can be dispensed with.

The output of the DC/DC converter is connected to a charging circuit 230. The charging circuit 230 may have been selected from a multiplicity of charging circuits which are known from the prior art. These may be integrated circuits, for example. Preferably, however, a simple current source and particularly preferably a simple resistor are used as the charging circuit. The charging circuit 230 then thus has exclusively passive elements which automatically cause a flow of current when there is a voltage difference between the connections of the charging circuit 230. In the exemplary embodiment, the charging circuit 230 is formed by a resistor of approximately 220 ohms, for example. In this case, a carbon layer resistor, a metal layer resistor or another resistor from the prior art can be used.

The output of the DC/DC converter is also connected to the input of the safety circuit 300. In this case, the safety circuit comprises two series-connected diodes 301 and 302. The diodes 301, 302 in turn each have a nonlinear characteristic. In the exemplary embodiment, a respective Schottky diode is again used. Accordingly, the diodes 301 and 302 likewise have a voltage drop in the forward direction. The output of the safety circuit 300 is connected to the load 110 of the load circuit 100. In this case, the diodes 301 and 302 are arranged such that they pass current flowing from the charging electronics 200 to the load circuit 100 and block a current in the opposite direction. The charging electronics 200 are also connected to the second connection of the load shed switch 130 of the load circuit 100 via the output of the charging circuit 230. In the normal mode, the power supply adopts a first operating state, in which the rechargeable battery 120 has a charge state which is sufficient for supplying power to the load 110. The load shed switch 130 is then in its closed state. In this first operating state, the load 110 is essentially supplied with current via a first current path SP 1. In this case, the current is supplied by the rechargeable battery 120 via the load shed switch 130 and the diode 101 in the load 110. At the same time, the rechargeable battery 120 is charged by the replaceable battery 210 via a second current path SP 2. In this case, the current path SP 2 is routed from the battery 210 via the DC/DC converter 220 and the charging circuit 230 to the second connection of the load shed switch 130. On account of the charging circuit 230, which is formed by a resistor, a charging current in the current path 2 is limited in terms of its magnitude. The effect of this is that current peaks which are caused by a briefly increased energy consumption by the load 110 during medicament administration, for example, hardly affect the charging current, which is kept at a low value of 0.5 itiA to 2 mA, for example, by the charging circuit 230. This conserves the replaceable battery 210 to a considerable degree and extends its life.

A third current path SP 3 is routed from the charging electronics 200 via the two diodes 301, 302 of the safety circuit 300 to the load 110 of the load circuit 100. In the first operating state, however, the energy is routed to the load 110 essentially not via this current path 3 but rather via the current path SP 1. The reason for this is that the total resistance of the current path SP 3 is significantly higher than that of the current path SP 1, as illustrated by the characteristics in the graph in figure 3. A voltage difference of 350 mV across the diode 101 in the current path SP 1 brings about a current of approximately 50 mA in the current path SP 1, while the same voltage difference across the diodes 301, 302 in the current path SP 3 brings about only a current of approximately 1 mA (see dashed line in figure 3) . In the normal mode, the current path 1 therefore carries a current which is a multiple larger than the one in the current path 3. If the output voltage of the rechargeable battery 120 drops below the typical operating point, however, so that the performance capability of the rechargeable battery decreases, the load is increasingly also supplied with current via the current path SP 3. The reason for the fall in the output voltage of the rechargeable battery 120 may be diverse in this case. By way of example, the rechargeable battery 120 or the load shed switch may be faulty, the rechargeable battery 120 may be briefly or permanently isolated from the load on account of a mechanical, external effect, etc. In the emergency mode, the load 110 is supplied with the energy essentially via the current path SP 3. In this case, the change from the normal mode (first operating state) to the emergency mode (second operating state) is made continuously, automatically and without a time delay, and in the present preferred embodiment purely passively, i.e. without active control intervention.

The emergency mode is automatically exited again and the normal mode readopted as soon as the output voltage of the rechargeable battery 120 is sufficiently high again.

A further operating state is adopted by the power supply when the rechargeable battery 120 is isolated from the load by the load shed switch 130. In this case, the functionality of the load shed switch 130 can best be described with reference to the state diagram in figure 4. This has different states Sl, S2, S3 and transitions A, B, C, D which the load shed switch 130 can adopt. The states Sl, S2, S3, S4 and the transitions A, B, C, D, E, F are in this case denoted as follows:

Sl: active operation with replaceable battery 210 (normal mode) , S2: active operation without replaceable battery 210,

S3: storage state (without replaceable battery 210),

S4: emergency mode when rechargeable battery 120 has failed,

A: removal of the replaceable battery 210,

B: insertion of the replaceable battery 210,

C: control signal SA,

D: insertion of the replaceable battery 210,

E: failure of the rechargeable battery 120, and

F: adequate charge state reached by the rechargeable battery 120. Sl symbolizes the normal operation of the portable medical administration appliance, wherein the replaceable battery 210 has been inserted and is in a charged state. Removal of the replaceable battery 210 or a drop in the charge state of the replaceable battery 210 prompts state S2 to be adopted, this state being able to be exited again in the direction of state Sl as a result of the insertion of a fresh replaceable battery 210. When the user initiates the control signal SA in the state S2, the rechargeable battery 120 is isolated from the load and the storage state S3 is adopted. When a fresh replaceable battery 210 is inserted, the voltage at the input b of the logic circuit 132 rises and the rechargeable battery 120 is connected to the load again, as a result of which the state S3 is exited and active operation with an inserted replaceable battery 210, corresponding to state Sl, is adopted again. State S4 is adopted when the rechargeable battery 120 no longer has a sufficiently high output voltage to operate the load 110, which means that the active operation is ensured by the replaceable battery 210 via the current path SP 3. This state is exited again when the charge state and hence the output voltage of the rechargeable battery is sufficiently high again. These transitions are continuous.

Upon completion of the manufacture of the medical 5 administration appliance, following a successful final test in the appliance, the replaceable battery 210 can thus be removed from the appliance. The manufacturer can then initiate the control signal SA, as a result of which the rechargeable battery 120, which . has

10 previously advantageously been put into an optimum, defined charge state of 50-70%, for example, is completely isolated from the load. In this state

(corresponding to the aforementioned state S3) , the administration appliance can be stored in the longer

15 term for several years. When a replaceable battery 210 is inserted by the end user, the rechargeable battery 120 is automatically reconnected to the load by the load shed switch 130, with a possible loss of charge from the rechargeable battery 120 during storage being

20. compensated for again by the replaceable battery 210.

The administration appliance is ready for use in line with the state Sl.

The invention is naturally not limited to the above 25 exemplary embodiment, and a large number of modifications are possible. Thus, by way of example, it would also be possible to use other diode types instead of Schottky diodes 101, 301 and 302. Instead of diodes, it would also be possible to use other, preferably 30 nonlinear electrical elements, or a combination of diodes and further elements would be conceivable. In addition, the load 110 does not necessarily need to have a motor controller which drives the motor intermittently. The administration appliance could 35 equally be designed to administer the medicament stored in the container to the patient completely, in one go. Instead of being connected to a button outside the administration appliance, the input a of the logic circuit 132 could also be connected to an internal output of a control unit which the user uses to initiate the control signal SA, for example by means of a command within a menu guide. In addition, the logic circuit 132 could be designed such that if the voltage at the input b drops below a particular value indicating deep discharge then it sends the switch 131 a signal to open and hence isolate the rechargeable battery 120 from the load. A large number of further modifications are possible.

LIST OF REFERENCE SYMBOLS

100 Load circuit 200 Charging electronics

101 Diode 210 Replaceable battery 110 Load 220 DC/DC converter

120 Rechargeable battery 230 Charging circuit

130 Load shed switch 300 Safety circuit

131 Switch 301 Diode

132 Logic circuit 302 Diode

133 Disconnection signal

Claims

PATENT CLAIMS

1. Power supply for a medical administration appliance having an electrical load (110) ,

wherein the power supply has a first energy source (210) and a rechargeable second energy source (120),

wherein the power supply has a first current path (SP 1) in order to route energy from the rechargeable second energy source (120) to the load (110), and wherein the power supply has a second current path (SP 2) with a charging circuit (230) in order to route energy from the first energy source (210) to the second energy source (120) and thereby to charge the second energy source (120) ,

wherein the power supply is designed to supply energy to the load (110) essentially via the first current path (SP 1) from the rechargeable second energy source (120) and to charge the second energy source via the second current path (SP 2) from the first energy source, in the normal mode, characterized in that the power supply has a third current path (SP 3) from the first energy source to the load which is designed to supply energy to the load (110) from the first energy source in the event of failure of the second energy source (120) or in the event of a reduced power output from the second energy source (120) in an emergency mode.

2. Power supply according to Claim 1, wherein the first and third current paths respectively have one or more components (101, 301, 302) which are designed to prompt a change from the normal mode to the emergency mode continuously and without active control intervention.

3. Power supply according to one of Claims 1 and 2, wherein the components (101, 301, 302) of the first and third current paths are nonlinear resistor elements, and wherein in the normal mode there is a voltage drop across the resistor elements of the third current path which is higher than a voltage drop across the resistor elements of the first current path.

4. Power supply according to one of the preceding claims, wherein the charging circuit (230) is designed such that at least in the normal mode there is permanently a charge voltage across the second energy source (120) .

5. Power supply according to one of the preceding claims, wherein the charging circuit (230) consists of one or more components, particularly one or more resistors, which are designed to limit a current through the charging circuit without active control intervention.

6. Power supply according to one of the preceding claims, wherein the first energy source (210) has an output voltage in the normal mode which is lower than the output voltage of the second energy source (120), and wherein the power supply comprises a DC/DC converter (220) in order to convert the output voltage of the first energy source (210) into a higher voltage.

7. Power supply according to one of the preceding claims, wherein the first energy source (210) is a replaceable battery.

8. Power supply according to one of the preceding claims, which comprises a load shed switch (130) which is designed to isolate the second energy source (120) completely from the load.

9. Power supply according to Claim 8, wherein the load shed switch (130) is designed such that it automatically connects the second energy source

(120) to the load when the charge voltage exceeds a minimum value for the first time.

10. Power supply according to Claim 8 or 9, wherein the load shed switch (130) can be actively operated by a control signal in order to isolate the second energy source (120) from the load and/or to connect the second energy source to the load.

11. Medical administration appliance for administering a medicament in liquid form, which has a power supply according to one of the preceding claims and an electrical load (110) .

12. Medical administration appliance according to Claim 11,

wherein the load (110) comprises an electric motor and a motor controller,

wherein the motor controller is designed to activate the motor intermittently in activation phases in order to release the medicament incrementally, and

wherein the charging circuit produces a charging current which is smaller than the current in the first current path in the activation phases.

13. Medical administration appliance according to Claim 11 or 12, which has a common housing unit which accommodates both the first energy source (210) and the second energy source (120) .

14. Method for the operation of a medical administration appliance having a power supply and an electrical load (110) , wherein the power supply has a first energy source (210) and a second energy source (120),

wherein in the normal mode the load (110) is supplied with energy essentially from the second energy source (120) and the second energy source (120) is charged from the first energy source (210), and

wherein the load (110) is supplied with energy from the first energy source in the event of failure of the second energy source (120) or in the event of a reduced power output from the second energy source (120) in an emergency mode.

15. Method according to Claim 14, wherein the load

(110) comprises an electric motor,

wherein the electric motor is operated intermittently, so that activation phases, in which the motor is activated, have pauses between them, and

wherein the second energy source (210) is charged with a charging current which is smaller than the current through the motor in the activation phases .