Method for managing the power supply of an electronic control unit during the starting phase of a motor vehicle

Abstract

A method for managing the power supply of an electronic control unit during the engine starting phase of a motor vehicle, the electronic control unit including a microcontroller, wherein a command to start the engine indicating the start of the starting phase is detected; the frequency of operation of the microcontroller is reduced; this reduced frequency of operation of the microcontroller is maintained for as long as effective starting of the engine has not been acknowledged; and the frequency of operation of the microcontroller is re-established once effective starting of the engine has been acknowledged.

Claims

1. A method for managing a power supply of an electronic control unit during an engine starting phase of a motor vehicle combustion engine, said electronic control unit comprising a microcontroller, the method comprising: receiving a command to start the combustion engine; in response to receiving the command to start the combustion engine, reduing a frequency of operation of the microcontroller to a predetermined reduced clock frequency while the internal combustion engine starts a turning over process; maintaining this reduced clock frequency of the microcontroller for as long as the turning over process of the combustion engine is being performed and the effective starting of the combustion engine has not been acknowledged; and increasing the frequency of operation of the microcontroller to a predetermined clock frequency for controlling a plurality of functions of the motor vehicle once the turning over process of the combustion engine is complete and the effective starting of the combustion engine has been acknowledged.

2. The management method as claimed in claim 1, wherein: when the command to start the combustion engine is detected and the frequency of operation of the microcontroller of the electronic control unit is reduced, only the inputs involved the starting of the combustion engine are powered, the other inputs not being powered or being inhibited; and when effective starting of the combustion engine has been acknowledged and the frequency of operation of the microcontroller of the electronic control unit has recovered to its nominal value, all the inputs of the microcontroller are continuously powered.

3. The management method as claimed in claim 2, wherein, when the frequency of operation of the microcontroller of the electronic control unit is reduced, the inputs involved in the starting of the combustion engine are powered periodically.

4. The management method as claimed in claim 3, wherein, when the electronic control unit is fitted with a CAN bus, the frequency of operation of the microcontroller of the electronic control unit during the starting of the combustion engine is equal to the clock frequency of said CAN bus.

5. The management method as claimed in claim 2, wherein, when the electronic control unit is fitted with a CAN bus, the frequency of operation of the microcontroller of the electronic control unit during the starting of the combustion engine is equal to the clock frequency of said CAN bus.

6. The management method as claimed in claim 1, wherein, when the electronic control unit is fitted with a CAN bus, the frequency of operation of the microcontroller of the electronic control unit during the starting of the combustion engine is equal to the clock frequency of said CAN bus.

7. The management method as claimed in claim 6, wherein the frequency of operation of the microcontroller of the electronic control unit during the starting of the combustion engine is of an order of 8 MHz.

8. The management method as claimed in claim 1, wherein the reduction in the frequency of operation of the microcontroller during the starting of the combustion engine is achieved by a phase locked loop.

9. The management method as claimed in claim 1, wherein receiving the command to start the combustion engine is performed by detecting operation of the vehicle ignition or by detecting actuation of a start button that starts the combustion engine or by software start control.

10. The management method as claimed in claim 1, wherein, when the microcontroller is equipped with a CAN bus, acquisition of an information item acknowledging effective starting of the combustion engine is performed by communication on said CAN bus.

11. The management method as claimed in claim 1, wherein acquisition of the information item acknowledging effective starting of the combustion engine is performed by monitoring a battery charging voltage, by detecting a positive gradient in a variation in said voltage and determining when said voltage exceeds a predefined threshold.

12. The management method as claimed in claim 1, wherein acquisition of the information item acknowledging effective starting of the combustion engine is performed by monitoring a charging voltage of tank capacitors, by detecting a positive gradient in the variation in said voltage and determining when said voltage exceeds a predefined threshold.

13. The management method as claimed in claim 1, further comprising: receiving a message from an engine management computer, the message acknowledging the effective starting of the combustion engine.

14. The management method as claimed in claim 1, further comprising: acknowledging the effective starting of the combustion engine in response to a voltage gradient of the power supply combined with a voltage of the power supply reaching a threshold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other objects, features and advantages of the present invention will become apparent from the following description, provided by way of non-limiting example with reference to the appended drawings, in which:

(2) FIG. 1, as discussed earlier, is a view illustrating, in solid line, the profile of variations in battery voltage during the vehicle engine starting phase and, in dotted line, the profile of variations in the voltage at the input to the electronic control unit, according to the prior art.

(3) FIG. 2 is a view illustrating, in solid line, the profile of variations in battery voltage during the vehicle engine starting phase and, in dotted line, the profile of variations in the voltage at the input to the electronic control unit, obtained by applying the method according to an aspect of the invention.

(4) FIG. 3 is a schematic view illustrating the electronic diagram of a first exemplary embodiment of the management method according to an aspect of the invention.

(5) FIG. 4 is a schematic view illustrating the electronic diagram of another exemplary embodiment of the management method according to an aspect of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) As illustrated in FIG. 3, an electronic control unit 1 generally comprises: a microcontroller 2, a voltage regulator 3, a clock 4, inputs, outputs, a memory, etc.

(7) This electronic control unit is powered by the battery 5 of the vehicle.

(8) Such an electronic control unit 1 also comprises, upstream of the voltage regulator 3, one or more tank capacitors 6.

(9) According to an aspect of the invention, the method for managing the power supply of the electronic control unit 1 during the motor vehicle starting phase comprises the following steps: detection of a command to start the engine 7, indicating the start of the initialize-start phase; reduction of the frequency of operation of the microcontroller 2 of the electronic control unit 1; the maintaining of this reduced frequency of operation of the microcontroller 2 of the electronic control unit 1 for as long as effective starting of the engine has not been acknowledged; re-establishment of the normal frequency of operation of the microcontroller 2 of the electronic control unit 1 once effective starting of the engine has been acknowledged.

(10) The method of an aspect of the invention thus makes it possible to reduce the power consumption during the motor vehicle engine starting phase and as a result makes it possible, for the same capacitance of the tank capacitor or capacitors 6 used at present, to reduce the voltage drop across the terminals of the tank capacitor or capacitors 6 upon vehicle engine starting. In other words, the method according to an aspect of the invention makes it possible to filter the variation in voltage at the input to the electronic control unit 1 as illustrated in FIG. 2, during the vehicle engine starting phase and particularly during the initialize-start phase t1, so that this voltage remains above the reset threshold U.sub.SR of the electronic control unit 1.

(11) Thus, the leeway regarding the capacitance of the tank capacitor or capacitors which is needed in order for the input voltage of the electronic control unit 1 to remain above the reset threshold U.sub.SR is improved. In that way, it is possible to obtain a profile for the voltage across the terminals of the tank capacitor or capacitors 6 upon vehicle engine starting with a voltage drop at the limit of the reset threshold U.sub.SR (a profile identical to that of the prior art illustrated in FIG. 1), using a lower capacitance of the tank capacitor or capacitors 6.

(12) The detection of the command to start the engine 7 is achieved in various ways. For example, the starting phase is detected: when the ignition is actuated (also referred to as the key-on command); by the pressing of a start button of a start/stop device (usually referred to as a start/stop button) in order to transmit to an engine management computer, a command to start or stop this engine; by software control of the start, in the case of vehicles incorporating a stop and go (stop/restart) function, namely a function that stops the engine when the vehicle is immobile and automatically restarts as soon as the vehicle starts to move again (following, for example, pressure on the throttle pedal or on the clutch pedal).

(13) When the command to start 7 is detected, the frequency of operation of the microcontroller of the electronic control unit is switched to a frequency below its normal or nominal operating frequency, which is generally comprised between 40 MHz and 80 MHz. This reduced frequency is of the order of 8 MHz.

(14) This reduction in frequency is achieved, in a way known per se, by means of a phase locked loop 8 (also known as a PLL).

(15) When the electronic control unit 1 is fitted with a CAN bus 9, the frequency of operation of the microcontroller 2 of the electronic control unit 1 during the starting phase is reduced to a value equal to the clock frequency of said CAN bus 9. Specifically, in instances in which the electronic control unit 1 is fitted with a CAN bus 9, the communications on said CAN bus 9 are substantial and essential during said starting phase. In general, the frequency of the CAN bus 9 is of the order of 500 kHz, requiring a microcontroller clock frequency of the order of 8 MHz. Thus, according to the method of an aspect of the invention, the frequency of operation of the microcontroller 2 of the electronic control unit 1 is reduced and maintained at a value of 8 MHz for as long as effective starting of the engine has not been acknowledged.

(16) In order to increase the power saving during the vehicle engine starting phase, only those stages which are essential during said vehicle engine starting phase, such as, for example, communications on the CAN bus 9 when the electronic control unit is equipped with such a CAN bus 9, or scrutiny of information pertaining to the stopping of the start procedure, are powered.

(17) Those functions which, on the other hand, are not necessary during the starting phase are, in a way known per se, switched off or inhibited (which means to say that although power is applied to them, these inputs are not read by the microcontroller 2).

(18) For preference and advantageously, as illustrated in FIG. 4, in order to further improve the power saving during the vehicle engine starting phase, those inputs which are powered during this starting phase are done so periodically. This periodic powering of the inputs during the vehicle engine starting phase is performed in a way known per se using a specific switched power supply 11.

(19) This mode of operation during which the frequency of operation of the microcontroller 2 of the electronic control unit 1 is reduced and, possibly, when certain inputs of the microcontroller 2 are not powered or are powered periodically is maintained throughout the entire duration of the vehicle engine starting phase. In other words, this mode of operation is maintained for as long as effective starting of the vehicle has not been acknowledged.

(20) The information item 10 acknowledging effective starting of the vehicle engine is obtained in a number of ways.

(21) For example, when the microcontroller 2 of the electronic control unit 1 is equipped with a CAN bus 9, acquisition of the information item 10 acknowledging effective starting of the engine is performed by communication on said CAN bus 9 which itself obtains this information in a way known per se directly from an engine management computer with which the vehicle is equipped.

(22) Advantageously, particularly when the vehicle is not equipped with a CAN bus 9, acquisition of the information item 10 acknowledging effective starting of the engine is performed by monitoring the battery 5 charging voltage. Thus, a positive gradient in the variation in said battery charging voltage, combined with the exceeding of a predefined threshold U.sub.E, are the characteristic signs that the vehicle engine is turning over, or in other words of acknowledgement of effective starting of the vehicle engine.

(23) According to another example, acquisition of the information item 10 acknowledging effective starting of the engine is performed by monitoring the tank capacitors' 6 charging voltage. As before, a positive gradient in the variation in said voltage and the exceeding of a predefined threshold U.sub.E are the characteristic signs that the vehicle engine is turning over, or in other words of acknowledgement of effective starting of the vehicle engine.

(24) For example, the threshold U.sub.E that makes it possible to define acquisition of the information item 10 acknowledging effective starting of the engine is higher than the maximum value of the voltage fluctuations during the intermediate starting phase t.sub.2 referred to as the on-starter phase.

(25) Finally, when effective starting of the vehicle has been acknowledged, the frequency of operation of the microcontroller of the electronic control unit is switched to its normal operating frequency, namely for example a frequency of the order of 40 MHz, in a way known per se, via the phase locked loop 8.

(26) In addition, those inputs which were no longer powered or which were powered periodically are once again powered continuously.