GB2397955A

GB2397955A - Power control for auxiliary devices in a vehicle

Info

Publication number: GB2397955A
Application number: GB0229158A
Authority: GB
Inventors: Nissim Pnini; Adrian Marino; Youry Kirpichnikov
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2002-12-14
Filing date: 2002-12-14
Publication date: 2004-08-04
Also published as: GB0229158D0

Abstract

An electrical device 3 is powered from a vehicle's electrical system. The device 3 contains a sensor 21 to detect whether the vehicle engine is running, and a current level controller 23 that sets the current drawn by the device 3 to one level if the engine is not running, and to a second higher level if the engine is running. The embodiment is a laptop computer with a hard disc 3 having two heating elements 5. A temperature sensor 10 detects low ambient temperature and activates only one heating element 5A if the engine is not running, but activates both heating elements 5A, 5B if the engine is running.

Description

TITLE: ELECTRICAL DEVICES FOR USE BY CONNECTION TO A

VEHICLE BATTERY

FIELD OF THE INVENTION

The present invention relates to electrical devices for use by connection to a vehicle battery.

BACKGROUND OF THE INVENTION

Various electrical devices such as personal, laptop and notebook computers, mobile telephone chargers, radios, compact disc (CD) players and the like are operated in a vehicle such as a car as peripheral devices powered by the vehicle's battery. Whenever the vehicle is parked and the engine is turned off, the current consumption by such a device may continue and may cause the vehicle battery rapidly to become discharged.

Several prior publications describe systems designed to protect a battery of a vehicle, e.g. a car, from being discharged beyond the point at which it can still provide sufficient electrical power to start the vehicle.

For example, WO 98/58436 describes a system whereby current drain to a load is measured and an estimate is made of whether this current drain would take the battery below a safe charge state. If so the load is disconnected.

US-A-6,362,599 describes a system which disconnects the load on a vehicle battery detected to have low charge state.

US-A-5,677,614 describes a system which disconnects the load, after a time interval, on a vehicle battery detected to have a low charge state.

WO-A-90/06614 describes a system which operates to disconnect the load on a vehicle battery detected to have a low charge state.

Another possibility is available in modern vehicles.

Such vehicles have electrical control systems which are designed to supply electrical power to peripheral device(s) only after the vehicle engine is sensed to be switched on or running. When this condition is sensed, all the current required by the peripheral device(s) is taken from the charging circuit including the vehicle's alternator without discharging the vehicle's battery. However, this condition does not address the need to power a peripheral device whilst the engine is not running.

SUMMARY OF THE PRESENT INVENTION

According to the present invention there is provided an electrical device for use in a vehicle including means for connecting the device to a battery or charging circuit of the vehicle to draw electrical current from the battery or charging circuit, means for sensing whether the engine of the vehicle is running and a current level controller within the device which is operable, depending on an output from the means for sensing, to set the current drawn by the device to a first level when the engine is not running and to a second higher level when the engine is running.

The invention is basically different from the prior art approaches described above and does not require use of any mechanism to disconnect the device from the battery.

Rather it assumes that there is a load in the electrical device that the user has powered up, and therefore does not want to be disconnected.

By the invention, therefore, the device is powered with a reduced current rating if the vehicle engine is not running, and with a full current rating when the engine is running.

The electrical device may be any one of the devices known for use as peripheral devices in a vehicle and JO powered by the battery of the vehicle. Examples include personal, laptop and notebook computers, telephones or radios, e.g. mobile telephones or radios, telephone or radio chargers, compact disc (CD) players, audio cassette players, data transfer terminals and the like. The invention is particularly applicable to control the current drawn by electrical heating means used to heat the hard disk of a laptop or personal computer carried in or on the vehicle.

Where the electrical device includes a heating means, the heating means may include a first electrical heater arranged to be operable whether or not the vehicle engine is running and a second electrical heater arranged to be operable only when the engine is sensed to be running. The device may include a temperature sensor which measures the temperature of a unit, e.g. hard disk, within the electrical device. The current level controller may be a microcontroller, which in response to an output from the temperature sensor is operable to control whether or not the heating means should be operated. The controller may be connected to a first switch to control current flow between the vehicle battery and the first heater and to a second switch to control current flow between a voltage generator 4 _1 in the vehicle charging circuit, e.g. an alternator, and the second heater. The means for sensing may be connected to an electronic control system of the vehicle which may be a known system per se.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a schematic circuit diagram of a device embodying the invention connected to a vehicle battery.

FIG. 2 is a flow diagram illustrating operational steps in the use of the device shown in FIG. 1.

FIG. 3 is a series of graphs of illustrating energisation with time of the device shown in FIG. 1.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 is a schematic circuit diagram of a device embodying the invention connected to a vehicle battery 1.

In particular, the device comprises a hard disk 3 and its associated heating means 5 incorporated in the central processing unit 7 of a personal computer for operation by a user within the vehicle. The computer may for example be used by a member of the emergency services, such as the police. The hard disk 3 is intended to be used over a wide operating temperature range, e.g. from -20 C to 55 C. The hard disk 3 has a minimum low operating temperature, which is +5 C. In order to provide operation when the ambient temperature is lower than +5 C, it is necessary to heat the hard disk 3 to increase its temperature to +5 C. This is done by the heating means 5 drawing electrical current from the vehicle battery 1 and heating the hard disk 3 electrically. However, the vehicle battery current consumption which may be used to provide electrical heating of the hard disk 3 is limited typically to 200mA. This results in slow booting up of the computer in which the hard disk 3 is incorporated, because booting up can only begin when the minimum operating temperature (+5 C) is reached by the electrical heating.

The invention allows extra current to be supplied to the heating means 5 of the hard disk 3 allowing current at a level above 200mA to be supplied without drawing the extra current directly from the vehicle battery. This extra current is taken from a charging circuit including the vehicle alternator as soon as the engine has been turned on (after ignition) and is running. The extra current increases the heating rate of the hard disk 3 and enable the minimum operating temperature to be reached, and the computer then to boot up, much sooner.

The circuit shown in FIG. 1 includes a first switch 9 allowing connection to be made between a positive terminal la of the battery 1 and the heating means 5. The battery 1 has a negative terminal lb which is earthed. The switch 9 when closed allows current to be drawn from the battery 1 as in known circuits. The heating means 5 of the circuit of FIG. 1 includes a first resistive electrical heater 5a connected to the switch 9 and also a second resistive electrical heater 5b. A second switch 11 is connected between the heater 5b and the positive terminal la of the battery 1. The positive terminal la of the battery 1 is also connected in a charging circuit, a conduit 12 of which is shown, to an alternator 13 of the vehicle which is at a greater positive potential and keeps the battery charged when the vehicle engine is running.

The switch 11 is open when the engine of the vehicle is not running. The switch 11 is closed when the vehicle is running. Closing of the switch 11 allows connection of the heater 5b to allow additional current to be drawn thereby.

Determination of whether or not the vehicle engine is running is made as follows. An adapter 15 is connected to an electronic control system 17 of the vehicle and receives an output signal from the control system 17. Such a control system 17 is able to indicate whether the engine is running and provide an output signal in a known manner. In practice, the adapter 15 may be a unit external to the computer which converts a signal from a vehicle bus of the control system 17 to a known FireWire (should this be Firewall?) format in accordance with IEEE 1394 standard.

The adapter 15 has an output connection to a FireWire controller 19 within the CPU 7. The controller 19 is a microcontroller which handles FireWire functionality for the CPU 7 by conversion of the signal from the adapter 15 provided in turn from the control system 17. The controller 19 is connected to a detector 21 which applies logical operations to the signal applied thereto to determine within the CPU 7 the engine running state. The detector 21 is connected to a current level controller 23 within the CPU 7. The controller 23 is connected to the switch 11 and outputs from the detector 21 control opening and closing of the switch 11. The controller 23 is also connected to the switch 9 and to a temperature sensor 10.

Operation of the circuit shown in FIG. 1 is illustrated in FIG 2. In a start step 31 initiated by a controller 23 in the CPU, the temperature T of the hard disk 3 is determined in a known manner by the temperature sensor 10. If T is below (colder than) -20 C no action is taken. If T is above (warmer than) -20 C switch 9 is closed and heater 5a is turned on in a step 33. A signal from the detector 21 is obtained and in step 35 indicates whether the vehicle engine is running. If the engine is running, the switch 11 is closed by the controller 23 in response to an output from the detector 21 and the heater 5b is thereby turned on in step 37. If the engine is not running, the switch 11 is not closed. In both cases, the temperature of the hard disk 3 is monitored. When the temperature is greater than -5 C, neither of the heaters 5a and 5b is required and in step 39 both heaters 5a and 5b are turned off by the controller 23 opening switches 9 and 11 giving the state indicated by reference numeral 41 in which the hard disk 3 can be operated without external heating assistance. The controller 23 repeats the process when the temperature of the hard disk is detected to be below 5 C, e.g. next time boot up of the computer incorporating CPU 7 is required.

FIG.s 3(a) to (d) illustrate the effect of using the invention. FIG.s 3(a) and FIG. 3(b) illustrate use of the single heater 5a only as in the prior art. In FIG. 3(a), the computer containing the CPU 7 is switched on at a time tl. The heater 5a is switched on at time tl and as indicated in FIG. l(a) drawing a current I of 200mA until a time t2 when the hard disk 3 has reached its minimum operating temperature. The heater 5a is then turned off. As a working example, the ambient temperature is -2 C at the time tl as shown in FIG. 2. The temperature of the hard disk 3 increases linearly by heating from the heater 5a until at the time t2 the temperature reaches the minimum operating temperature of 5 C. The computer is now ready for boot up.

In FIG. 3(c), the same procedure is initially applied as illustrated in FIG. 3(a) and (b), i.e. the temperature of the hard disk 3 increases linearly from -2 C following time tl by heating using the heater 5a. However, at a time t3 which occurs before t2 is reached, the engine of the vehicle is sensed to be running. At t3 the heater 5b is also switched on. The current I consumed increases to a level above 200mA, e.g. typically 400mA, as shown in FIG. 3(c). The heating by both heaters 5a and 5b continues until the minimum operating temperature of 5 C is reached at a time t4. The heaters 5a and 5b are then turned off. As shown in FIG. 3(d), the rate of heating is increased using both heaters 5a and 5b so the temperature of 5 C at time T4 is reached more quickly, i.e. the elapsed time from tl to t4 in FIG.s 3(c) and 3(d) is less than the elapsed time from tl to t2 in FIG.s 3(a) and 3(b). Thus the invention beneficially allows more rapid reaching of the minimum operating temperature at which booting up of the computer containing the CPU 7 can begin.

Claims

1. An electrical device for use in a vehicle including means for connecting the device to a battery or charging circuit of the vehicle to draw electrical current from the battery or charging circuit, means for sensing whether the engine of the vehicle is running and a current level controller within the device which is operable, depending on an output from the means for sensing, to set the current drawn by the device to a first level when the engine is not running and to a second higher level when the engine is running.

2. An electrical device according to claim l and which comprises a personal, laptop or notebook computer, a data transfer terminal, a telephone or radio charger, a telephone or radio, an audio cassette player, or a compact disc (CD) player.

3. An electrical device according to claim 2 comprising a computer having a hard disk and heating means for electrically heating the hard disk, and wherein the current level controller is operable to control the current drawn by the heating heating means from the battery or charging circuit.

4. An electrical device according to claim 3 and wherein the heating means includes a first electrical heater arranged to be operable whether or not the vehicle engine is running and a second electrical heater arranged to be operable only when the engine is sensed to be running.

5. An electrical device according to any one of the preceding claims and wherein the device includes a temperature sensor which is arranged to measure the temperature of a unit within the electrical device.

6. An electrical device according to claim 5 and wherein the current level controller is operable, in response to an output from the temperature sensor, to control whether or not the heating means is operated.

7. An electrical device according to claim 6 and wherein the heating means includes a first electrical heater arranged to be operable whether or not the vehicle engine is running and a second electrical heater arranged to be operable only when the engine is sensed to be running and wherein the controller is connected to the means for sensing and to a first switch to control current flow between the vehicle battery and the first heater and to a second switch to control current flow between a voltage generator in the charging circuit of the vehicle and the second heater.

8. An electrical device according to any one of the preceding claims and wherein the means for sensing is connected to an electronic control system of the vehicle.

9. An electrical device according to claim 1 and substantially as described herein with reference to the accompanying drawings.

10. A method of operating an electrical device according to claim 1 when connected to a battery and vehicle charging circuit of a vehicle, the method being substantially as described herein with reference to the accompanying drawings