WO2000031603A1

WO2000031603A1 - Circuit for producing a stabilised supply voltage for a plurality of users

Info

Publication number: WO2000031603A1
Application number: PCT/DE1999/003516
Authority: WO
Inventors: Michael Lenz; Frank-Lothar Schwertlein; Heinrich Gschloessl
Original assignee: Infineon Technologies Ag
Priority date: 1998-11-19
Filing date: 1999-11-03
Publication date: 2000-06-02

Abstract

The present invention relates to a circuit for producing a stabilised supply voltage for a plurality of users, wherein said circuit comprises a voltage regulator for converting a first voltage at its input into a second voltage for use at its output. The second voltage is supplied to the control input of at least one impedance converter having its output connected respectively and exactly to one user, wherein the voltage applied at the output corresponds to that applied at the control input. It is thus possible to supply the same reference voltage to a plurality of users, while the circuit is further protected against potential interference.

Description

description

Circuit arrangement for generating a stabilized supply voltage for several consumers

The invention relates to a circuit arrangement for generating a stabilized supply voltage for several consumers with a voltage regulator, which converts a first voltage at its input into a second voltage and makes it available at its output.

Electronic control units are used to supply various components, e.g. a microcontroller, sensors for detecting certain operating states or actuators for setting desired setpoints, stabilized voltages are required. The generation of a constant and stabilized voltage is implemented, for example, by analog voltage regulators or clocked switching regulators. Various embodiments of linear voltage regulators are described, for example, in Tietze, Schenk, Semiconductor Circuit Technology, 10th Edition, Springer-Verlag, 1993, pages 542 to 555. Due to the ever increasing number of electrical consumers in electronic systems and the increasing complexity of the electronic controls, the power loss occurring in a voltage regulator rises sharply due to the ever increasing current. This power loss requires complex cooling measures.

In order to prevent malfunctions in an electronic control unit caused by power loss, it can be useful and necessary to use several voltage regulators to supply the large number of consumers. to use. This means that the power loss can be distributed across several housings or locations. The disadvantage of such a solution is that the output voltage generated by several voltage regulators may not be exactly the same are. However, this can lead to problems if the loads supplied by various voltage regulators are used for signal processing, for example in a microprocessor. The various reference voltages, i.e. the output voltages of the voltage regulators, can cause faults. This is particularly the case when the signal-processing consumers are carried out in so-called subnetworks, that is to say at a spatial distance from the control unit. The consumers outside the control unit are generally sensors that record the operating states of certain components. The lines leading to the outside from the control unit to the sensors are also at great risk of a short circuit.

The use of switching regulators instead of analog voltage regulators to reduce the power loss has the disadvantage of a high price.

Figure 1 shows a basic circuit arrangement with a voltage regulator, which supplies several consumers with a constant voltage, as is known from the prior art. The circuit arrangement has a control unit 10, on which a voltage regulator 3, a microprocessor 7, and two drivers 8, each of which controls a consumer 4, 5 located outside the control unit 10. The consumer 4 is shown by way of example as an actuator; this can be a servomotor, for example. The sensor 5 detects, for example, the temperature or speed of an electric motor. The control unit 10 has a first supply potential connection 1, which forms the input of the voltage regulator 3. The positive supply voltage Vbb is present at this. If the circuit arrangement were used in a motor vehicle, this would be 12 V, for example. The voltage regulator 3 also has a reference potential connection 9, which advantageously represents the ground potential. At output 2, voltage regulator 3 supplies a constant output voltage Vref, which is 5 V, for example. The voltage Vref present at the output 2 represents the supply voltage for the microcontroller 7 and the consumers 4, 5.

The control unit could be used in the automotive sector and could represent an electronic control unit (ECU) that monitors and controls various sensors or actuators in the car. An application would be conceivable, for example, in an ABS or an airbag control. Depending on the number of consumers, there is a more or less large power loss in the voltage regulator 3. This is determined from the voltage drop between output 2 and input 1 of voltage regulator 3 and the current flowing depending on the number of consumers. As already mentioned, the power loss due to the voltage regulator necessitates cooling measures.

A disadvantage of the known circuit arrangement is that the function of the entire circuit arrangement can be impaired in the event of a short circuit on one of the supply lines 20. If the reference potential is present on one of the supply lines 20 due to a fault, this inevitably leads to the destruction of the controller 7, which carries out the control of all consumers. If the microcontroller 7 fails, the entire circuit arrangement fails. Voltage regulators, however, are usually designed to be short-circuit proof. Likewise, the circuit arrangement can be impaired if an overload can occur due to a fault in the consumer.

The object of the present invention is therefore to provide a circuit arrangement for generating stabilized voltage for a plurality of consumers, which can provide each consumer with exactly the same reference voltage. Furthermore, the power loss occurring during operation can be dissipated or distributed in a simple manner. This object is achieved with the features of patent claim 1.

According to the invention, it is provided that the voltage present at the output of the voltage regulator is fed to at least one impedance converter at its control input, the output of the impedance converter being connected to exactly one consumer each and the voltage present at the output of the voltage regulator being present at the control input of the impedance converter. corresponds to the tension.

If an impedance converter is connected upstream of every consumer that requires the same reference voltage, that is, the output voltage of the voltage regulator, the voltage generated by the voltage regulator can be "passed on" to other consumers decoupled. Consequently, only an expensive voltage regulator is required, while the reference voltage is provided by the impedance converters, which are connected between the output of the voltage regulator and the supply potential connection of the respective consumer.

Of course, it is not necessary to switch an impedance converter between each consumer and the voltage regulator if an exact reference voltage is not required at the consumer.

Embodiments of the invention can be found in the subclaims.

According to the invention, the supply voltage input of the impedance converter is connected to the input of the voltage regulator. This means nothing other than that the positive supply voltage is present at the supply voltage input of the impedance converter. The output of the impedance converter is connected to the supply voltage input via the load path of a power transistor. A driver circuit controls the power transistor so that the control input applied voltage at the output of the impedance converter is available. The advantage of this circuit arrangement is that the current is conducted past the voltage regulator, so that the power loss is generated in the impedance converter. However, since a correspondingly large number of impedance converters are provided in a complex system, the power loss is distributed over several locations or components. The power transistor is advantageously a PNP transistor.

Another advantage is the high precision of the reference voltage made available to the consumers. The risk of a malfunction of the circuit arrangement due to a short circuit or overcurrent is further reduced.

A differential amplifier is advantageously provided in the impedance converter of the circuit arrangement according to the invention, the negative input of which is connected to the connection point of the collector of the power transistor to the output of the impedance converter. The positive input of the differential amplifier is connected to the control input of the impedance converter, the output of the differential amplifier controlling a transistor which regulates the voltage drop across the load path of the power transistor. The collector-emitter path of this transistor is located between the base of the power transistor and a reference potential connection.

Furthermore, a further transistor is provided, the base connection of which is connected to the control input of the impedance converter and the collector-emitter path is connected in series with a current source between the supply voltage input and the reference potential connection. The connection point between the current source and the emitter of a further transistor is connected to an operating potential connection of the differential amplifier. This will possible that by applying a very low voltage at the control input of the impedance converter can be operated in power saving mode. Due to a low potential at the control input, the output of the impedance converter is switched to high resistance and therefore reduces its current consumption to a few μA.

A saturation control for the power transistor is advantageously provided, which reduces the reverse current in the case of an inverse operation and controls the base current in the drop mode. Inverse operation can occur, for example, due to a short-circuit in the supply voltage, with a brief interruption of the supply voltage, or with reverse polarity. On the one hand, the reverse current is prevented by the bipolar power transistor, which, in contrast to a MOSFET, does not have an integrated, anti-parallel diode. The backflow is also limited by the saturation control. This is described, for example, in EP 0 374 288 B1. The control of the base current in drop mode leads to an optimized power control of the power transistor. The base current is regulated against the reference potential, advantageously the ground potential.

The impedance converter is advantageously designed in a monolithically integrated form. As a separate component, it can be placed in a circuit arrangement in a simple manner at the desired locations.

In a further advantageous embodiment, the voltage present at the control input of the impedance converter is controlled via a microcontroller. The voltage specified by the microcontroller can change between the second voltage, that is to say the voltage present at the output of the main voltage regulator, and a reference potential. The advantage is the flexible use of the impedance converter. The impedance converter can then be used, for example, as a voltage regulator, which is one of the main voltage voltage-dependent voltage precisely generated and made available to the respective consumer. However, it is also conceivable to use the impedance converter as a switched controller. In this case, the control input of the impedance converter is alternately acted upon by the voltage present at the output of the main voltage converter and by a voltage value below a threshold value which puts the impedance converter into the sleep mode. It is thus possible, for example, to read out information from a sensor only at certain times, that is to say to only supply the sensor with a voltage while it is in the rest mode in the rest of the time. This enables a very effective power saving mode. It is also possible, as already mentioned, to use the impedance converter as a high-side switch, which switches the voltage present at the supply voltage input of the impedance converter.

The circuit arrangement according to the invention is advantageously used in an electrical control unit in the motor vehicle sector.

The invention is illustrated below with the aid of several figures. Show it

FIG. 1 shows a basic circuit arrangement known from the prior art with a voltage regulator,

FIG. 2 shows the basic structure of the circuit arrangement according to the invention, which has a number of impedance converters corresponding to the number of consumers,

3 shows the circuit implementation of the impedance converter described in FIG. 2 and Figure 4 shows another embodiment of the circuit arrangement according to the invention and

FIG. 2 shows a circuit arrangement that could be used as a control unit in a motor vehicle, for example. The control unit 10 differs from the control unit shown in FIG. 1 mainly in that, in addition to a voltage regulator 3, a microcontroller 7, drivers 8 and consumers 4, 5, it has an impedance converter 6, each between the supply voltage connection of the consumers 4, 5 and the output 2 of the voltage regulator 3 are switched. FIG. 2 shows two consumers 4, 5, each of which is assigned an impedance converter 6. An impedance converter 6 each has a supply voltage input IN, which is connected to the first supply potential connection 1, to which a positive supply voltage Vbb is present. A control input ADJ is connected to output 2 of the voltage regulator, to which a reference voltage Vref is present. The reference voltage is generally less than the supply potential Vbb and is predetermined by the output of the voltage regulator 3. An output Q, which is regulated in such a way that the same voltage is applied to it as at the control input ADJ, is connected to the consumer 4 or 5 and serves this as a supply potential connection. Each of the impedance converters is connected to a reference potential connection 9, as is the voltage regulator 3. The reference potential connections 9 can be connected to one another internally.

The advantage of this circuit arrangement is that the power loss is no longer generated at the voltage regulator 3, but at the impedance converters 6. The current required by the consumer is conducted around the voltage regulator 3. The power loss caused by the voltage regulator 3 is now only due to the current it needs and the falling voltage. The impedance converters 6 are advantageously designed as individual, packaged semiconductor components. elements, therefore the power loss can be spatially distributed.

Another advantage is the increased reliability of the entire circuit arrangement. If a short circuit or overcurrent occurs on the supply line 20, which is, for example, outside the control unit 10, the consumer 4, 5 can be damaged as a result, but the entire circuit arrangement is not impaired. The impedance converter 6 is advantageously designed for current and overvoltage, so that this damage is prevented by this control unit 10. A decoupling of the various outputs to the consumers from the control unit is thus achieved.

Another advantage of the circuit arrangement according to the invention is that only a precise voltage regulator is required, which is generally expensive and complex to manufacture. This is the voltage regulator 3 in FIG. 2. The impedance converters 6 use the precision and accuracy of the voltage regulator 3 and precisely regulate this predetermined reference voltage. Accordingly, every consumer receives the same reference voltage. The use of several voltage regulators, which could lead to problems in the entire circuit arrangement due to the different reference voltages, is thus avoided. The circuit arrangement according to the invention is also significantly cheaper.

Figure 3 shows the circuit implementation of the impedance converter described in Figure 2. The impedance converter

6, which is ideally designed as a separate packaged semiconductor component, has four different outputs. The supply potential of the entire circuit arrangement, for example the control unit, is present at the supply voltage input IN. The supply voltage input IN is over the

Load path of a bipolar PNP power transistor connected to the output Q of the impedance converter 6. The output is Q hereby connected to the collector, while the supply voltage input IN is connected to the emitter. The output is also connected to the inverting input of the differential amplifier 12. The non-inverting input is connected to the control input ADJ. On the output side, the differential amplifier 12 is connected to the base connection of a bipolar transistor 13, which has its collector connected to the base connection of the power transistor 11, while the emitter is connected to the reference potential connection 9. The bipolar transistor 13 is of the opposite conductivity type as the power transistor 11. This circuit arrangement consequently works as an impedance converter.

It is essential that the PNP transistor 11 is a so-called

Has low drop switching. The drop voltage, that is to say the voltage dropping minimally across the PNP transistor between the emitter and the collector, is kept as small as possible in order to enable the precision of the impedance converter to be achieved even with a slightly higher supply voltage Vbb than the voltage present at the control input ADJ 6 is not affected. This is particularly important in the automotive sector, where, for example, a sharp drop in the supply voltage of 12 V can be observed during the starting process. With a small drop voltage, however, the voltage present at output Q, which is identical to the voltage present at control input ADJ, remains at a stable value. The differential amplifier works in its common mode range. This means that the control loop remains closed.

Furthermore, a saturation regulator 16 is provided which reduces a reverse current in the event of a possible inverse operation of the impedance converter. In practice, the control loop of the impedance converter 6 at output Q is compensated for ground by a capacitor that has a small μF capacitance. If the supply voltage at the supply voltage input IN breaks down during operation, the voltage results a significantly higher value at output Q than for the supply voltage, since voltage is still present at the capacitive load. For example, in the event of a short circuit at the supply voltage input IN - caused, for example, by switching off the voltage supply at which other consumers are connected - the voltage at the supply voltage input IN goes to zero, while at its output Q the voltage is initially maintained by the smoothing compensator. As a result, a current flows in the opposite direction to the original direction (reverse current), which can lead to a functional impairment or even destruction of the impedance converter if it is not limited by the saturation control to values that are not critical for the component. Such a saturation regulator is described, for example, in EP 0 376 288 B1.

The impedance converter according to FIG. 3 has a further bipolar transistor 14 which is connected with its base connection to the control input ADJ. The collector of the further transistor 14 is connected to the reference potential connection 9 in

Connection while the emitter of transistor 14 is connected to the first supply potential terminal via a current source 15. The connection point between the current source 15 and the emitter of the transistor 14 is connected to an operating potential connection of the differential amplifier 12.

If a voltage below a certain point is applied to the control input ADJ of the impedance converter 6, this circuit ensures that the output Q becomes high-resistance and thus its current consumption is reduced to a few μA. A typical switching threshold at which the impedance converter 6 is brought into a power-saving mode is typically 0.8 V. It is thus possible to supply the consumer with power only when this is also necessary. The control input ADJ is therefore expediently supplied with a voltage by a microcontroller. It is also possible to use the impedance converter shown in FIG. 3 as a high-side switch. For this purpose, the control input ADJ is switched to the potential at the supply voltage input IN or above. The differential amplifier is then in large-signal operation and therefore fully controls the power transistor 11. The saturation control then takes on the task of optimally controlling the base current of the power transistor 11, so that the lowest possible voltage drops from the collector-emitter path when the base current is optimized.

An impedance converter used as a high-side switch has short on / off times. Furthermore, it requires only a small amount of current in sleep mode. The control as to whether the impedance converter is used as a controller or switch is selected by the voltage at the control input ADJ.

FIG. 4 shows a further exemplary embodiment of the circuit arrangement according to the invention. The impedance converter 6 is constructed as described in FIG. 3.

The supply voltage Vbb present at the first supply potential connection 1 is regulated down to a reference voltage Vref via a voltage regulator 3 at the output 2 of the voltage regulator. This is fed to a microcontroller 7, which can generate a digital signal at the output 21 of the microcontroller 7 via two transistors 17 and 18 connected in series with its load path. At this output 21, either the reference voltage Vref can be applied to the control input ADJ, so that exactly this voltage is corrected at the output Q of the impedance converter 6. In the other case, the reference potential can be applied to the control input ADJ, so that the impedance converter is switched to the sleep mode. The output Q of the impedance converter 6 and the voltage regulator 2 are connected to compensation capacitors 22 and 23. The transistors 17 and 18 are of the opposite conduction type and are made of one in a known manner Driver 19 in the microcontroller 7 controlled. The two transistors 17 and 18 form an inverter.

The controller 7 can of course have a large number of inverter stages, so that a large number of impedance converters 6 can also be controlled. The number of impedance converters depends on the use of the entire circuit arrangement.

Claims

claims

1. Circuit arrangement for generating a stabilized supply voltage for several consumers (4, 5) with a voltage regulator (3) which converts a first voltage at its input (1) into a second voltage and provides it at its output (2), characterized in that that the first or second voltage is supplied to at least one impedance converter (6) at a control input (ADJ), which is connected with its output (Q) to exactly one consumer (4, 5), the output (Q ) applied voltage corresponds to the voltage applied to the control input (ADJ).

2. Circuit arrangement according to claim 1, characterized in that the impedance converter identifies the following further features;

a supply voltage input (IN) which is connected to the input (1) of the voltage regulator,

an output (Q) which is connected to a supply voltage input (IN) via the load path of a power transistor (11),

- A driver circuit (12, 13, 14, 15) which controls the power transistor (11) so that the voltage present at the control input (ADJ) is made available at the output (Q).

3. Circuit arrangement according to claim 2, characterized in that a differential amplifier (12) is provided, the negative input of which is connected to the connection point of the collector of the power transistor (11) and the output (Q) and the positive input of which is connected to the control input (ADJ) is connected, the output of the differential amplifier (12) controlling a transistor (13) which regulates and also regulates the voltage drop across the load path of the power transistor (11) the collector-emitter path is located between the base of the power transistor (11) and a reference potential connection (9).

4. Circuit arrangement according to claim 2 or 3, characterized in that a further transistor (14) is provided, the base connection of which is connected to the control input (ADJ) and the collector-emitter path of which is connected in series with a current source (15) between the Supply voltage input (IN) and the reference potential connection (9) is connected, the connection point between the current source (15) and the emitter of the further transistor (14) being connected to an operating potential connection of the differential amplifier (12).

5. Circuit arrangement according to claim 2 to 4, characterized in that a saturation control (16) for the power transistor (11) is provided, which regulates the base current in the drop region and which reduces the reverse current in the case of inverse operation.

6. Circuit arrangement according to one of the claims 2 to 5, characterized in that the impedance converter (6) is monolithically integrated.

7. Circuit arrangement according to one of the claims 1 to 6, characterized in that the power transistor (11) is in a bipolar PNP transistor.

8. Circuit arrangement according to one of the claims 1 to 7, characterized in that the voltage applied to the control input (7ADJ) of the impedance converter (6) is controlled via a microcontroller (7).

9. Circuit arrangement according to claim 8, characterized in that the voltage predetermined by the microcontroller (7) can be changed between the second voltage and a reference potential.

10. Use of the circuit arrangement according to one of claims 1 to 9 in an electrical control device for a motor vehicle application.