WO2014059498A1

WO2014059498A1 - Bistable selection circuit configured for keeping the last selected state

Info

Publication number: WO2014059498A1
Application number: PCT/BR2013/000413
Authority: WO
Inventors: Frederico VERMEJO; Iannis Nicolaos PAPAIOANNNOU
Original assignee: Continental Brasil Indústria Automotiva Ltda.
Priority date: 2012-10-16
Filing date: 2013-08-14
Publication date: 2014-04-24
Also published as: BR102012026533A2

Abstract

The present invention relates to a bistable selection circuit (1), generally known as a flip-flop (switch on-switch off) circuit, designed to retain the most recently selected state in the absence of power supply (12, 22), using only passive and semiconductor components.

Description

BESTABLE SELECTION CIRCUIT CONFIGURED TO KEEP LAST SELECTED STATE

The present invention relates to a bistable selection circuit, commonly called a switch-type circuit (open or closed), configured to maintain the last selected state during power failure using only passive and semiconductor components.

Description of the prior art

There are three major groups of electro-electronic components, namely: (i) electromechanical components such as relays, contactors, mechanical switches, switches, for example, which usually contain an electrical component and a movable part that opens or closes; (ii) passive components, such as resistors, capacitors, inductors, for example, that do not contain moving parts; and (iii) active components, also called semiconductors, which are silicon / germanium-based components, configured to allow or prevent current to flow through their output as a function of an input current.

Selection circuits using electromechanical relays, ie electromechanical components, are widely employed in the state of the art. Generally, these relays consist of two distinct parts, the first being an electromagnetic coil and the second a mechanical contact. The mechanical contact is configured as a switch, and can conduct an electrical current when closed or restrict electrical current when open. When there is an electric current feeding the relay, this current creates a magnetic field in its coil, which attracts or repels mechanical contact, changing its position and therefore allowing or not the electric current to flow.

Preferably, the mechanical contact makes the connection between the relay output pins and thus opens or closes such pins in the presence or absence of power at the input pins. Thus, the operation of such circuits can be simplified to the operation of a selector switch, which when open prevents current from flowing, and when closed allows current to flow.

Additionally, these circuits are generally configured to change input voltages relative to circuit output voltages. Because of this, the circuits connected to the input and output of a relay may have totally different configurations. For example, the input circuit may be a low voltage direct current circuit and the output circuit a high voltage alternating current circuit, or even a circuit that simply modifies the voltage level of the direct current by transforming a voltage of 3.3V at a voltage of 5V.

It is noted, however, that such circuits have a huge disadvantage, which is the need to apply a constant electric current to a specific state. This is due to the fact that, generally, such devices remain open in the absence of power, only making the circuit output connection when a current is applied to the input. Thus, these devices have a not insignificant power consumption and, additionally, the mechanical mobile connection of these relays has an extremely short lifetime and a high current to create a sufficient magnetic field to move such a connection when compared to electronic components. , due not only to the constant mechanical movement that is required for the change of state but also to the electrical conduction through the terminals.

Another flaw that can be cited is that these relays usually lose their state setting if the power is disconnected, ie generally these relays are always initialized to a specific state, regardless of the state they were off, which can lead to in serious failures. As examples of such failures, one can cite the case where this type of relay is purposely shut down for performing some kind of preventive maintenance on a given power grid. Assuming that during the maintenance a momentary interruption of the power supply of the electric grid in question occurs, when the power is restored to the relay contacts may be initialized in the closed state, that is, allowing the power supply to the network being performed maintenance. This type of overheating can lead to serious occurrences, such as burning equipment, short circuits, or even damage to a worker who is performing maintenance on the mains.

There are some solutions for reducing the aforementioned problems that can be observed in the state of the art such as bistable relays. This type of relay further comprises the mechanical mobile connection, but this connection is stable in both open and closed positions. This type of relay can thus modify and maintain a position of the mobile connection from a control signal, which should not necessarily be maintained after its application.

Generally, the construction of these relays is carried out in two distinct ways, wherein the relay may have (i) two input pins, wherein the one-way voltage supply changes the position of the mobile connection to an open or closed one, and an opposite direction feed changes the position to the opposite position, or (ii) may have three input pins, where a current applied to two of the three pins modifies the position of the mobile connection, one pin being used as "sef, or that is, when a current is applied to this pin the mechanical mobile connection closes the output circuit, and a second pin being used as a reset, that is, when a current is applied to this mechanical mechanical connection opens the output circuit. Input pin is a common pin to both inputs, used to close the circuit in both cases.Note that there is a decrease in the energy required to control this type of relay, but is still mechanical moving connection and the current required to create a sufficient magnetic field to move such a connection.

In a separate attempt to solve these problems, devices were created that do not understand the mechanical parts present in electromechanical relays, such as solid state relays, TRIACs or optocouplers. Circuits of this type, however, can keep some of problems encountered in the state of the art, such as the need for constant current to define existing states, as well as creating additional problems, such as the need for isolation, the need for complex and specific control, price increases, among others, which may limit your application.

Examples of some prior art which address the above problems are US Patent Application 2006/0245129 A1, Canadian Patent CA 1,058,742 and US Patent 8,084,894.

US Patent Application US 2006/0245129 A1 describes a hybrid relay utilizing components of an electromechanical relay connected to a solid state relay comprising optocouplers. Although the author describes such a creation as a bistable solid state relay, it can be noted that in all configurations, electromechanical relays with moving mechanical connections are still used.

Canadian Patent CA 1,058,742, 1975, comprises a relay utilizing a magnet and its residual magnetism to control the output of the solid state relay. Thus, the use of a magnetization current is still necessary, as well as its use is limited and expensive due to the memory actuation realized by residual magnetism, using magnets.

US 8,084,894 discloses an oscillator circuit coupled to a transformer for isolation between a control circuit and an output circuit. Similar to the Canadian patent, such a configuration has a costly and interference-sensitive device as it still uses transformers and oscillators for system isolation.

As can be seen from the analysis of the above documents, none of the documents found has a simple, low cost key using only passive and semiconductor elements.

Objectives of the invention

Thus, it is an object of the present invention to provide a circuit of bistable selection, which retains last state information even during system power failure, using only passive and semiconductor elements.

It is another object of this invention to provide a selection circuit with a long service life as well as a reduction in cost and energy consumption over the elements found in the state of the art. Brief Description of the Invention

The objects of the invention are achieved by providing a bistable selection circuit comprising a control circuit that generates a control signal and at least one output element configured to generate an output signal. The bistable selection circuit is electrically connected to a voltage input and the control circuit is electrically connected to the output circuit and voltage input. Additionally, the bistable selection circuit is configured so that, at the moment the control circuit is fed by the voltage input and generates the control signal, the output element must modify the operating state between transmission or interruption. of a voltage at the output signal, dependent on the state defined by the control signal. In addition, the bistable selection circuit further has a memory element that stores the operating state of the output element and, at a time determined by the circuit input power failure, maintain the stored operating state.

Additionally, a bistable selection integrated circuit is described, the integrated circuit having at least two power supply terminals and two output terminals, further comprising a solid state relay. The integrated circuit has two operating states, a closed operating state that allows electrical connection between the output terminals and an open operating state that does not allow electrical connection between the output terminals. The integrated circuit shall maintain the last operating state during the moments when the power supply at the integrated circuit power terminals is interrupted.

In addition, a bistatic selection circuit is also presented. comprising voltage inputs and outputs. This circuit insulates between the outputs and the inputs, and is electrically connected to a control circuit. The bistable selection circuit comprising at least one first voltage follower, having at least one data input, one data output, one positive voltage input and one negative voltage input, a second voltage follower comprising at least one voltage input. data, a data output, a positive voltage input and a negative voltage input, and an electronic key having at least one data input, a data output, a positive voltage input and a negative voltage input. The bistable selection circuit further comprises a memory element having at least one data input, one data output, one clock, one positive voltage input and one negative voltage input. The first voltage follower data input is electrically connected to the control circuit via a first bus, and the first voltage follower output is electrically connected to the memory element data input. The second voltage follower data input is electrically connected to the control circuit via a second bus and the second voltage follower output is electrically connected to the memory element clock. The memory element output is electrically connected to the electronic key data input and the electronic key data output is electrically connected to the bistable selection circuit output via a fourth bus. Positive voltage and negative voltage inputs feed the bistable selection circuit. The bistable selection loop shall, in the presence of power, determine the state to be sent to the memory element via the first voltage follower and the first bus data signal and determine whether the first bus data signal it shall or shall not be transmitted to the electronic switch by means of the second voltage follower and the second bus data signal. The memory element must store the data signal from the first bus in the presence of power, and keep this signal at its output in the absence of power. Finally, a selection method comprising a bistable selection circuit or an integrated circuit as previously defined is proposed, the selection method comprising the steps of:

A) check the state of the power supply;

B) loading an operating state value of an output element stored in a memory element;

C) modify the operating state of the output element to the loaded value;

D) checking the occurrence of a signal that modifies the operating state of the output element;

E) in the presence of the signal, modify the operating state output element to the value determined by the signal;

F) storing the operating state of the output element in the memory element;

G) check the power supply.

Finally, an automotive alarm system is provided that comprises a bistable selection circuit or an integrated circuit, or utilizes the selection method as previously defined.

Brief Description of the Drawings

The present invention will hereinafter be described in more detail based on an exemplary embodiment shown in the drawings. The figures show:

Figure 1 is a block diagram representing an electronic selection device found in the state of the art;

Figure 2 is a block diagram depicting a configuration of the electronic selection device according to the present invention; and

Figure 3 is an electronic circuit representing a specific electronic selection device utilizing commercial components in accordance with the present invention.

Detailed Description of the Figures

Figure 1 illustrates a prior art protection circuit 1, which presents a device generally used to isolate a control circuit 2 from an output circuit 3 of an electronic system. Preferably, this electronic system comprises a voltage input 4, generally comprising an alternating voltage of 110V or 220V, which are values used for commercial scale power transmission. However, as protection circuit 1 performs electrical isolation between control circuit 2 and output circuit 3, such values are not limited to those used on commercial scales, but are appropriate to the need of the electronic system in which the protective device is coupled.

Voltage input 4 is generally electrically connected to one or more output elements 5, which are devices that switch an output voltage 6 at system output terminals, ie, transmit or interrupt a voltage at system output 6. Some examples of output elements 5 are contactors, electromechanical relays, solid state relays, TRIACs, and optocouplers, among others.

Generally, these output elements 5 require a control signal 7, derived from control circuit 2, which may be a simple signal from sensors, for example, or preferably a signal from a microcontroller, a memory or a retainer. of states. When microcontrollers are used, they are usually powered by a direct voltage, and therefore voltage input 4 (usually alternating) must be treated before powering the microcontroller. Thus, voltage input 4 is preferably also electrically connected to a rectifier circuit 8, such as a simple circuit using diode and capacitor bridges, capable of transforming the alternating voltage of voltage input 4 into a direct voltage to power the control circuit 2, which comprises the microcontroller.

Control circuit 2, in turn, controls control signal 7 sent to output elements 5 so that they transmit or interrupt voltage at the output. These control signals 7 sent to the output elements 5 may be derived from sensor signal processing such as current sensors, temperature sensors, or analog ports, timers and even specific programming on microcontrollers, for example. Finally, as can be seen in figure 1, the transmission or interruption of the output voltage by the output contactors is performed to control the supply of an electric load 9.

Although several circuits use voltage input 4 as the signal to be transmitted at the output of output elements 5, other circuits use an output voltage completely different from the input voltage. In these circuits, the input voltage is not electrically connected to output elements 5, only to control circuit 2, which in turn connects to output elements 5 as a simple control signal, and an additional voltage distinct from the input voltage. The input is connected to the output pins of the output elements 5. In this way, the microcontroller can control the transmission or interruption of a signal at the output totally different from any of the signals it receives, ie there is complete isolation (or protection). of control circuit 2 relative to output circuit 3.

Although widely used, state-of-the-art circuits employing electromagnetic relays have several problems previously discussed, while using solid state relays generally does not allow the last state of the output to be memorized in the event of a power failure or shutdown. increase the final product price and require greater control complexity. These problems are solved by the present invention, which creates a bistable selector switch using only passive and semiconductor components, simplifying the circuit and reducing costs.

This configuration can be seen in figure 2, which illustrates a preferred system construction mode, which uses only three components to create a selection circuit, which further has two distinct supply voltages 21, 22 each having a pole. positive 21+, 22+ and a negative 21-, 22- pole of voltage. A voltage regulator 23 is electrically connected to a flip-flop 24, which in turn is connected to an electronic output switch 25. The voltage regulator 23 is switched on. supplied by the input voltage 21, and serves as the supply for the flip-flop 24.

If a high logic voltage signal is applied to data input 26 of flip-flop 24 together with a signal at clock input 27, this signal will be transmitted to output electronic switch 25, which generally means that the electronic switch 25 will output the output voltage 22 to the output terminals 28, preferably connected to an electrical charge 9.

If the opposite happens, a low-level voltage signal is applied to data input 26 of flip-flop 24 together with a signal at clock input 27, this signal will also be transmitted to output electronic switch 25, the which generally means that the electronic output switch 25 will not interrupt the output voltage 22 at the output terminals 28.

Also, if there is a voltage drop or system shutdown, the voltage regulator 23 will no longer feed the flip-flop 24, but it will be configured to keep the last state in its output, ie even if there is no power on the flip -flop 24, this will keep at its output the logical level of the last signal applied to data input 26 along with a signal at clock input 27.

In this way a simple, efficient and inexpensive integrated circuit with only three components (voltage regulator 23, flip-flop 24 and electronic output switch 25) can be manufactured, with four or six inputs (positive supply voltage 21 +, negative supply voltage 21-, data input signal 26 from flip-flop 24, clock input 27 of flip-flop 24, positive output voltage 22+ and negative output voltage 22-) and one or two outputs (terminals 28), capable of functioning as a bistable selection circuit, with memory of the last state even without power. That is, a simple integrated circuit consisting of these three components can control an electrical load 9 from an input supply voltage 21, an electrical load supply voltage 22 and a simple binary control signal. Preferably, the circuit utilizes a D-type flip-flop, which stores information of only one bit. Additionally, circuits that invert the output relative to the input signal may be used, or more complex circuits, such as the use of nonvolatile memory in place of the flip-flop, or the use of control elements. more complex outputs. Also, it is anticipated that the system will comprise only a supply voltage for the input and output. It should be noted, however, that the present invention in its simplest configuration presents a large cost reduction, as well as the complexity of control required.

This is mainly due to the fact that simple flip flops are used, and a high side switch type electronic switch, preferably, or low side switch. The operation of both circuits is identical, ie the switch is opened or closed for a battery to power the charge. The difference with these circuits is that when the switch is connected directly to the positive pole of the system, that switch can be made up of a simple transistor (semiconductor, which does not comprise electromechanical parts).

Figure 3, on the other hand, illustrates a specific embodiment of a bistable selection circuit utilizing commercially sold components. In this specific configuration, voltage followers U1, U2, U3 are configured to power a memory element U4 and an electronic switch U5. As an example, commercially sold components that may be used to produce such a circuit may be MC74VHC1 GT50 type voltage followers U1 to U3, an FM1 type U4 memory element 105 and a BSP772T type U5 electronic switch.

Voltage followers U1, U2, U3 MC74VHC1 GT50 are buffers that have five pins, the first being unconnected, the second being the data input, the third being the ground (negative voltage input), the fourth the output (in data input) and the fifth is the positive voltage input. These components, usually unit gain operational amplifiers, are usually configured to copy the voltage at their input to their output, preferably used to isolate and connect. output to input, usually with different impedances. In this specific case, these components are configured to adapt the logic levels of direct current with different voltages, ie in this case the buffer receives a 3.3V signal and a 5V supply and thus when the system is switched on. saturated with a positive input signal at the input voltage (in case 3.3V), its output will receive the logic level of the power supply (in case 5V).

The memory element U4 FM1105 is a power retainer, which has eight pins, the first being the positive voltage input, the second the first data output (depending on the first data input), the third the second input. data, the fourth clock, the fifth the second output (depending on the second input), the sixth negative voltage input, the seventh the first input and the eighth the input. This component is a memory device configured to store conventional logic inputs and maintain the stored state in the absence of power, which in this specific case, as already exemplified, has the function of a type D flip-flop, requiring only one input and output. of data to store one-bit information.

Finally, the U5BSP772T electronic switch is a high side switch, which also has eight pins, the first being ground (negative voltage input), the second being data input, the third being data output, the fourth not connected and from the fifth to the eighth positive voltage input. This device is configured to function as a key that opens and closes the system, ie this device controls the transmission or interruption of a current at its output, ie whether or not there is voltage at its output.

A control circuit (not shown) must be configured to send data to the protective electrical circuit. In this specific configuration, the data input of the first voltage follower U1 is connected to the control circuit (not shown) via a first bus B1, and the output of the first voltage follower U1 is connected to the data input. memory element U4. The second voltage follower U2 data input is connected to the control circuit (not shown) via a second bus B2, and the second voltage follower U2 output is connected to the clock of memory element U4. The data input of the third voltage follower U3 is connected to the output of memory element U4, and the output of the third voltage follower U3 is connected to the control circuit (not shown) via a third bus B3. Memory element output U4 is also connected to data input of electronic switch U5, and data output of electronic key U5 is connected to system output via a fourth bus B4 and control circuit (not shown). via a fifth bus B5.

Resistors R1 to R1 1, capacitors C1 to C5 and diodes D1 can be calculated and used depending on the circuit components, both for the power supply of the components and for the treatment and transmission of signals between them, being the positive voltage and voltage inputs. configured to power the bistable selection circuit. Also, although all negative voltage inputs are usually connected to a single ground T, there are three possible distinct positive voltage inputs for system power.

The first voltage follower U1 and the third voltage follower U3 receive a positive voltage from a possible V _mc controller of the control circuit (not shown), preferably 3.3V. In the first voltage follower U1, this positive voltage from a possible V _mc controller is used for signal processing at the data input, while in the third voltage follower U3 this positive voltage from a possible V _mc controller is connected to the voltage. positive feeding. This is due to the fact that these signals that come into contact with the possible control circuit microcontroller (not shown) and therefore must respect the voltage limit of the same.

The positive supply voltage of electronic switch U5 is fed by a second voltage V _kt from the control circuit (not shown). This is due to the fact that this voltage defines the logical output level of the system and can therefore be changed depending on the output circuit (not shown) to which it is connected, or adjustments to the voltage from the memory element. U4. The other positive voltage supply V I preferably have the usual amount of high logic level, ie, preferably 5V, which may originate from the control circuit itself (not shown) or a separate voltage source (not shown). Thus, the feeds of the components that come into contact with the control circuit may have a distinct supply, preferably from the control circuit, of the components that come in direct contact with the output, which may have a separate supply.

Thus, the data signal of the first bus B1 is the signal that determines the state to be sent to memory element U4, while the data signal of the second bus B2 is the signal that determines whether the data signal of the first bus B1 may or may not be transmitted to electronic switch U5, ie the clock of memory element U4.

Third bus B3 and fifth bus B5 data signals serve as flags for the control circuit (not shown), ie determine the status of memory element U4 via the third bus data signal B3 and the status of the electronic switch U5 via the fifth bus data signal B5. In the presence of power, memory element U4 stores the data signal of the first bus B1, which is kept at its output even in the absence of power.

The fourth bus signal B4 is the signal that determines the system output. Such a signal can control the operation of an electrical charge by being directly connected to the load, for example, or even being connected to a power circuit (not shown) which in turn is connected to the electrical charge. The load supply circuit may be directly connected to the fourth bus, ie having the same power supply as the integrated circuit, or having an indirect supply, wherein the fourth bus is connected to a power circuit comprising a separate supply.

This bistable selection circuit can also be made as a single integrated circuit. Although such an integrated circuit may have, in this particular configuration, two inputs and three outputs in addition to the power supply, the simplified configuration of this circuit may have only two inputs and one output.

Using the teachings of the present invention, an integrated circuit is provided, especially used as an electronic selector switch, having memory of the last state. The bistable selection circuit thus has two operating states, a closed operating state, which allows electrical connection between output terminals and an open operating state, which does not allow electrical connection between output terminals. The closed operating state allows current to pass, that is, it allows the transmission of voltage at its output terminals, while the open operating state interrupts such transmission.

At a time when the power supply in the integrated circuit power terminals is interrupted, the instant immediately after the power supply is restored, the integrated circuit is able to return to the last operating state, for example by means of a flip flop that stores the operating state of the circuit, including the possible use of a microprocessor to determine the operating state of the circuit and the stored or loaded flip-flop values.

Obviously, there is a minimum time limit for this next instant, derived from the time required for current to flow through the entire circuit, opening or closing the component connections. Generally, this time is measured in tens of microseconds (ps) using the aforementioned electronics.

Finally, a method of protection of electronic devices comprising at least one of the previously defined circuits is proposed. A generalization of the method that can be used for all circuits comprises the steps of:

A) check the state of the power supply;

B) load an operating state value of an element of output stored in a memory element;

C) modify the operating state of the output element to the loaded value;

F) storing the operating state of the output element in the memory element;

G) check the power supply.

Where, in the event of power failure in step A or G, the method returns to step A, while in the hypothesis of the presence of power in step G, the method returns to step D.

In the circuit illustrated by Figure 2, steps A and G are performed by checking for the presence of voltage at the supply voltage poles, ie the presence of a voltage difference between the 21 + positive supply voltage, the supply voltage. 21, while steps B and F are performed by flip-flop 24 and steps C and E are performed by the electronic output switch 25. Again, the control circuit (not shown) is responsible for controlling the performance of such steps by such components via data input signal 26 and clock input 27 of flip-flop 24, as well as performing verification step D.

Finally, in the circuit illustrated in figure 3, steps A and G are performed by checking for the presence of voltage at the positive voltage inputs, preferably at the positive voltage supply voltage input, ie the presence of a voltage difference between the positive supply voltage V _{a and} i ground T, while steps B and D are performed by memory element U4 and steps C and E are carried out by electronic switch U5. Again, the control circuit (not shown) is responsible for controlling the performance of such steps by such components by means of the first and second buses B1 and B2, as well as performing the verification step D. Preferably, the present invention is applied to inhibit theft of a vehicle. The bistable selection circuit of the present invention has the role of "cutting off power" so that the vehicle cannot function. Simply put, it is an on / off toggle switch that must be on before the vehicle can be started. In addition, circuit protection is already provided by other vehicle circuit components, and the integrated circuits containing the electronic switches generally include over voltage, undervoltage, over temperature, and over current, among others, as well as the function of diagnosis.

Having described a preferred embodiment example, it should be understood that the scope of the present invention encompasses other possible variations, being limited only by the content of the appended claims, including the possible equivalents thereof.

Claims

1. Bistable selection circuit comprising:

a control circuit configured to generate a control signal;

at least one output element configured to generate an output signal;

the bistable selection circuit being electrically connected to a voltage input;

the control circuit being electrically connected to the output element and voltage input;

the bistable selection circuit being set to: the instant the control circuit is powered by the voltage input and generates the control signal, the output element modifies the operating state between the transmission or interruption of a voltage in the control signal. output depending on the control signal;

the bistable selection circuit being characterized by the fact that it additionally has:

a memory element, set to:

store the operating state of the output element; and at a time determined by the lack of supply of the bistable selection circuit by the voltage input, maintain the stored operating state.

Bistable selection circuit according to claim 1, characterized in that the control circuit comprises a microcontroller.

Bistable selection circuit according to claim 2, characterized in that the control circuit microcontroller is configured to generate the control signal.

Bistable selection circuit according to one of Claims 1 to 3, characterized in that the memory element is electrically connected to the control circuit and the output element.

Bistable selection circuit according to one of the claims 1 to 4, characterized in that the memory element is a type D flipflop.

Bistable selection circuit according to Claim 5, characterized in that the D-type flip-flop is an FM1 105 integrated circuit.

Bistable selection circuit according to one of Claims 1 to 6, characterized in that the output circuit is electrically connected to an electric charge.

Bistable selection circuit according to Claim 7, characterized in that the output circuit is electrically connected to the electrical load by means of a power circuit.

Bistable selection circuit according to one of Claims 1 to 8, characterized in that the output circuit supplies electronic devices.

Bistable selection circuit according to one of Claims 1 to 9, characterized in that the output element is an electronic switch.

Bistable selection circuit according to claim 10, characterized in that the electronic switch is a high side switch.

Bistable selection circuit according to claim 11, characterized in that the high side switch is of type U5BSP772T.

Bistable selection circuit according to one of Claims 1 to 12, characterized in that it is composed exclusively of passive or semiconductor elements.

14. Bistable selection integrated circuit, the integrated circuit having at least two power supply terminals and two output terminals, the integrated circuit configured to have two operating states, as follows:

a closed operating state allowing electrical connection between output terminals; and

an open operating state that does not allow electrical connection between output terminals;

integrated circuit being characterized by the fact that it keeps the optimum operating state during times when the power supply to the integrated circuit power terminals is interrupted.

Integrated circuit according to Claim 14, characterized in that the integrated circuit comprises a memory element for storing the operating state.

Integrated circuit according to Claim 15, characterized in that the memory element is a type D flip-flop.

Integrated circuit according to one of Claims 14 to 16, characterized in that the integrated circuit comprises a microprocessor configured to determine the operating state.

Integrated circuit according to one of Claims 14 to 17, characterized in that the output terminals are electrically connected to an electrically charged load.

Integrated circuit according to one of Claims 14 to 18, characterized in that the output terminals are electrically connected to the electrically charged load by means of a power circuit.

20. Bistable selection circuit comprising voltage inputs and outputs, the circuit being electrically connected to a control circuit and comprising at least:

a first voltage follower (U1) having at least one data input, one data output, one positive voltage input and one negative voltage input;

a second voltage follower (U2) comprising at least one data input, one data output, one positive voltage input and one negative voltage input;

an electronic key (U5) having at least one data input, one data output, one positive voltage input and one negative voltage input;

the bistable selection circuit being further characterized by a memory element (U4) comprising at least one data input, one data output, one clock, one positive voltage input and one negative voltage input; the first voltage follower (U1) data input being electrically connected to the control circuit via a first bus (B1) and the first voltage follower (U1) output being electrically connected to the memory element data input (U4);

the second voltage follower (U2) data input being electrically connected to the control circuit via a second bus (B2) and the second voltage follower (U2) output being electrically connected to the memory element clock (U4) ;

the memory element output (U4) being electrically connected to the electronic key data input (U5) and the electronic key data output (U5) being electrically connected to the bistable selection circuit output by a quarter bus (B4);

the positive voltage and negative voltage inputs being configured to power the bistable selection circuit;

the bistable selection circuit being configured such that, in the presence of power, the data signal from the first bus (B1) determines the state to be sent to memory element (U4) via the first voltage follower (U1) and the second bus data signal (B2) determines whether or not the first bus data signal (B1) is to be transmitted to the electronic switch (U5) via the second voltage follower (U2);

the memory element (U4) being configured to store the first bus data signal (B1) in the presence of the power supply and to keep this signal in its data output in the absence of the power supply.

Bistable selection circuit according to claim

20, characterized in that the fourth bus signal (B4) is electrically connected to an electrical charge.

Bistable selection circuit according to claim

21, characterized in that the fourth bus signal (B4) is electrically connected to an electrical charge by means of a power circuit.

23. Bistable selection circuit according to one of the following 20 to 22, further comprising a third voltage follower (U3) having at least one data input, one data output, one positive voltage input and one negative voltage input;

the third voltage follower (U3) data input being connected to the memory element output (U4) and the third voltage follower (U3) output being connected to the control circuit via a third bus (B3);

the control circuit being configured to determine the operating state of the memory element (U4) via the third bus (B3).

Bistable selection circuit according to one of Claims 20 to 23, characterized in that it further comprises a fifth bus (B5) electrically connecting the output of the electronic switch (U5) to the control circuit;

the control circuit being configured to determine the operating state of switch (U5) via fifth bus (B5).

Bistable selection circuit according to one of Claims 20 to 24, characterized in that it comprises separate feeds for the components that come into contact with the control circuit.

Bistable selection circuit according to Claim 25, characterized in that the feeds of the components that come into contact with the control circuit are from the control circuit.

Bistable selection circuit according to one of Claims 20 to 26, characterized in that the voltage followers are components of type MC74VHC GT50, the memory element (U4) is a component of type FM1 05 and the electronic key. (U5) be a component of type BSP772T.

28. Bistable selection circuit according to one of the claims 20 to 27, characterized in that it further comprises resistors, capacitors and diodes for the treatment of power and signals of the bistable selection circuit.

Bistable selection circuit according to one of Claims 20 to 28, characterized in that it is manufactured as a single integrated circuit.

Selection method characterized in that it comprises a bistable selection circuit as defined in one of claims 1 to 13, an integrated circuit as defined in one of claims 14 to 19, or a bistable selection circuit as defined in one of claims 20 to 29, the selection method comprising the steps of:

A. Check the state of the power supply:

B. load an operating state value from an output element stored in a memory element;

C. modify the operating state of the output element to the loaded value;

D. verify the occurrence of a signal that modifies the operating state of the output element;

E. In the presence of the signal, modify the state of operation of the output element to the value determined by the signal;

F. store the operating state of the output element in the memory element;

G. Check the power supply.

Selection method according to claim 30, characterized in that in the event of power failure in step A or G, return to step A.

Selection method according to claim 30 or 31, characterized in that in the hypothesis of the presence of feeding in step G, return to step D.

Automotive alarm system, characterized in that it comprises a bistable selection circuit as defined in one of claims 1 to 13, an integrated circuit as defined in one of the claims. claims 14 to 19, or a bistable selection circuit as defined in one of claims 20 to 29 or using a selection method as defined in one of claims 30 to 32.