GB2231178A

GB2231178A - Display and control unit particularly for a vehicle air-conditioning system

Info

Publication number: GB2231178A
Application number: GB9006708A
Authority: GB
Inventors: Aldo Serraglio
Original assignee: Marelli Autronica SpA
Current assignee: Marelli Europe SpA
Priority date: 1989-03-31
Filing date: 1990-03-26
Publication date: 1990-11-07
Anticipated expiration: 2010-03-26
Also published as: GB2231178B; DE4010021A1; IT8967232A0; ES2021243A6; IT1232073B; SE9001164D0; SE9001164L; DE4010021C2; FR2645081A1; FR2645081B1; GB9006708D0

Description

1 - s 1- -1- 7 a AN ELECTRONIC DISPLAY AND CONTROL UNIT FOR A SYSTEM,

PARTICULARLY A UNIT FOR CONTROLLING AN AIR-CONDITIONING SYSTEM FOR USE IN A MOTOR VEHICLE

The present invention relates to an electronic display and control unit for a system for use in a motor vehiclef and in particular to a control unit for an air-conditioning system according to the introductory part of Claim 1.

The electronic or central control units of modern air-conditioning systems for the passenger compartments of motor vehicles have very large numbers of optical indicators, typically light-emitting diodes (LEDs) or the like. Many of these optical indicators are usually lit in operation and this involves a considerable current consumption.

Two solutions are currently used for supplying the optical indicators. In a first solution, the light-emitting diodes are supplied at a low voltage (for example, a voltage of 5V) by the integrated current-regulator/ stabiliser of the electronic display and control unit to which the optical indicators belong. For this purpose.. the integrated currentregulator/stabiliser of the electronic unit must be of quite high power and is expensive because it must be provided with a suitable heat dissipator.

According to another solution, the light-emitting diodes of the electronic display and control unit are supplied by means of an additional voltage regulator which is separate and distinct from the unit, and which is connected to the battery of the motor vehicle and provided with suitable heat dissipators.

The second solution described above unsatisfactory since it requires the use of an is also 2 additional device and in any event involves a high dissipation of energy as heat.

The object of the present invention is to enable the optical indicators to be energised without the need to overdimension the integrated currentregulator of the electronic unit and without the need for an additional regulatorlstabiliser.

According to the invention, this object is achieved by means of a unit of the type specified above, whose main characteristic lies in the fact that:

the optical indicators are connected to the supply -terminal, and in that the control circuit has an input which is intended to be connected to the battery and is arranged to monitor the value of the voltage delivered by the battery in operation and to energise the optical indicators, enabling an on/off current to flow from the battery to the indicators through the supply terminal with a duty-cycle which is variable in a predetermined manner in dependence on the value of the battery voltage.

Further characteristics and advantages of the description will become clear from the detailed description which follows with reference to the appended drawings, provided by way of nonlimiting example, in which:

Figure 1 is a diagram which shows part of an air-conditioning system for the passenger compartment of a motor vehicle, including an electronic display and control unit according to the invention, 1 3 Figure 2 is a graph showing an example of the trace of the current supplied to the light-emitting diodes of the electronic unit of the system of Figure 1, in operation, and Figure 3 is a graph showing examples of traces of the times for which the light-emitting diodes are energised as functions of the battery-voltage value shown on the abscissa.

Figure 1 shows schematically part of a system for use in a motor vehicle, particularly an air-conditioning system. This system includes an electronic display and -control unit, generally indicated 1. The unit has a supply terminal 2 connected to the battery 3 of the motor vehicle. In operation, the battery delivers a direct voltage V B whose value may fluctuate within a predetermined range, for example, between 9 and 19 V.

Sensors and/or control devices, indicated A-N, are also connected to the electronic unit 1. These devices may, for example, include sensors for sensing the temperature inside and outside the passenger compartment of the vehicle, manual control and operating devices by means of which the user can set the desired air conditions, etc.

The unit 1 is also connected to actuator devices, indicated P-Z, such as, for example, electric fans, valves for closing air-supply ducts. etc. The air conditions set by the user are produced in the passenger compartment of the motor vehicle by the unit 1 by means of these devices.

The electronic unit 1 includes a microprocessor 4 4 connected to the sensors and/or control devices A-N and to the actuator devices P-Z.

The microprocessor 4 is provided with integrated memory devices, in known manner, and is supplied with a stabilised supply voltage by an integrated stabilised supply 5.

The microprocessor 4 is arranged, by conventional programming techniques, to acquire information signals from the devices A-N and, according to predetermined methods, to generate control signals to be imparted to the actuator devices T-Z.

Light-emitting diodes (LEDs), indicated D 1-D n 1 have their anodes connected to the supply terminal 2 through respective current-limiting resistors R 1-R n.

The cathodes of the diodes D 1-D n are intended to provide the user with an optical indication of the operating conditions of the air-conditioning system at any time.

Each time the microprocessor 4 has to energise one or more light-emitting diodes; it applies to the switching devices C associated with the diodes signals adapted to bring the cathodes of the diodes to a "low" level, thus enabling current to flow from the battery 3 to the diodes to be energised through the supply terminal 2. Conveniently, the microprocessor 4 is arranged particularly to enable current to flow intermittently in the diodes to be energised, at a frequency, for example, of 100 Hz and with a predetermined duty-cycle.

One input of the microprocessor 4, indicated 4a, is 1 connected to the supply terminal 2. The terminal 4a of the microprocessor represents the input of a so-called Uanalog channel" and the analog signal which is supplied to this terminal in operation is converted into digital form by the microprocessor for subsequent processing.

According to the invention, the microprocessor 4 is arranged to monitor the value of the voltage delivered by the battery 3 in operation, by means of the analog channel 4a, and to energise the light-emitting diodes with a duty cycle which is variable according to a predetermined function that decreases as the voltage of the battery 3 increases. In other words, when the voltage of the battery 3 decreases, the time T on for which the light-emitting diodes are energised during each energisation period T (Figure 2) is increased.

Figure 3 shows two graphs, and b, which represent examples of traces of two different predetermined laws for the variation of the energisation time T on o f the light-emitting diodes in dependence on the value assumed by the voltage V B delivered by the battery 3. These graphs can be stored. in tabulated form, in memory devices of the microprocessor 4 by wholly conventional techniques.

in Figure 1, a sensor for detecting that a light in the motor vehicle is lit is indicated 6. The sensor 6 may be constituted, for example, by a detector for detecting whether a lamp which illuminates the dashboard of the vehicle is on or off. This sensor is connected to an input of the microprocessor 4. The latter is thus arranged to vary the duty cycle for energising the light-emitting diodes to be energised, 6 according to at least f irst and second predetermined functions of the value of the voltage V b of the battery 3, for example, the two functions a and b of Figure 3. In conditions in which the sensor 6 indicates that the dashboard of the vehicle is not illuminated (a situation probably indicative of daylight operation), the microprocessor 4 makes operative that law according to which the energisation time of the light-emitting diodes is varied in dependence on that V,3 which corresponds to higher values of T on f or a given V B, that is, with reference to Figure 3, the law corresponding to the graph a.

However, when the sensor instrument panel of the passenger compartment illuminated (a situation probably indicative operation in conditions of low ambient light, 6 indicates that the is of f or example, night driving) the microprocessor 4 makes operative the other law for the variation of T on in dependence on V B. The system described above enables the best use to be made of the energy for lighting the light-emitting diodes of the display and control unit 1 without overloading the regulator/stabiliser 5 of the unit and without the use of an additional voltage regulator device. The system also enables a drastic reduction in the energy dissipated as heat.

Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the present invention.

t :1 7 Thus, for example, a dedicated (customised) integrated circuit could be used instead of the microprocessor 4.

8

Claims

1. An electronic display and control unit for a system for use in a motor vehicle, particularly a control unit for an air-conditioning system comprising:

at least one supply terminal the battery of the motor vehicle, a control circuit for connection to arranged to acquire information signals from the sytem and to provide the system with control signals in a predetermined manner, and a plurality of optical indicators (D 1-D n), particularly light-emitting diodes (LEDs) or the like, piloted by the control circuit characterised in that the optical indicators (D 1-D n are connected to the at least one supply terminal and in that the control circuit has an input which is intended to be connected to the battery and is arranged to monitor the value of the voltage (V B) delivered by the battery in operation and to energise the optical indicators (D 1-D n), enabling an on-of f current to f low f rom the battery to the indicators (D 1-D n) through the supply terminal with a duty-cycle which is variable in a predetermined manner in dependence on the value of the battery voltage (V b).

2. A unit according to Claim 1, characterised in taht the control circuit is arranged to enable a current f low with a duty cycle (T on /T) which decreases as the battery voltage (VB) increases.

3. A unit according to Claim 1 or Claim 2, characterised in that the control circuit is 1 1 1 9 arranged to energise a plurality of optical indicators (D 1-D n) in a multiplexed manner.

4. A unit according to any one of the preceding claims, characterised in that the control circuit is arranged to vary the duty cycle (T on /T) according to at least first (a) and second (b) predetermined functions of the voltage (VB) of the battery, the values of the duty cyle (T on /T) according to the first function (a) being greater for each value of the battery voltage (V B) than the values of the duty cycle according to the second function (b), and in that control means connected to the control circuit are provided and are adapted to enable the first or second function to be made operative selectively.

5. A unit according to Claim 4, characterised in that the control means comprise a sensor for detecting that a light of a motor vehicle is on, the sensor providing the control circuit with an activation signal for making the first or second function operative when the light is on or off.

6. A unit substantially as described and illustrated, and for the purposes specified.

Published 1990 atThe Patent Office, State House, 66.171 IilghHolborn, LondonWC1R4TP. Further copies maybe obtainedfrom The PatentOMceSales Branch. St Mary Cray, Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1187 1