Researchers Submit Patent Application, "Electric System Comprising a Load Driving Apparatus by Auto-Recovery Mode, and Method of Operating the Apparatus", for Approval
The patent's assignee is Stmicroelectronics S.r.l.
News editors obtained the following quote from the background information supplied by the inventors: "There are electric loads requiring for their starting-up or switching-on a current, known as 'start-up current', which can reach values which cannot be supplied by some types of power devices adapted to drive loads. Particularly, lateral flow power transistors, such as those manufactured by the BCD technology (Bipolar CMOS DMOS), as opposed to VIPower transistors, may not be capable of sustaining start-up currents of some types of loads, such as those used, for example, on motor vehicles, incandescent lamps or, generally, linear loads. These power transistors, operating as switches, manage the starting-up or switching-on step of the load by applying the auto-recovery mode.
"According to the auto-recovery mode, when the current absorbed by the load reaches a predetermined threshold value, the power transistor is switched many times between the switching-off and starting-up, to supply the load with a current having a PWM-type trend and taking a maximum value not greater than the threshold value. The average current supplied to the load in the auto-recovery mode is such as to take it, during a suitable time range and without anomalies, to the standard operation. Indeed, when the maximum current absorbed by the load in a PWM cycle is less than the threshold value, the auto-recovery mode is interrupted and the power transistor remains switched to supply a nominal current to the electric load.
"Electronic circuits on which power devices for driving electric load are integrated, offering the capability of operating in an auto-recovery mode, are often managed by a microcontroller outside the integrated circuit, such as, for example, the central unit of a car. Typically, such an outer or external microcontroller is capable of adopting protection provisions entailing the switching-off of the power devices in the presence of particular abnormal conditions.
"Moreover, power devices, such as MOSFETs, driving loads have the capability of switching off when non-sustainable junction temperatures are reached, by performing a so-called thermal shut down. The occurrence of abnormal operation conditions are observed in which the power transistor does not supply the load which it was designed for, but instead supplies a short-circuit or an overload.
"According to standard driving techniques, the short-circuit or overload conditions leading to an overcurrent state, are managed based on the auto-recovery mode until the occurrence of a temperature increase such as to cause the thermal shut down."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "The Applicant has observed the standard techniques, based on the auto-recovery and thermal shut down, may not be adequate with reference to the management of anomalies caused by an overload and short-circuit. Specifically, standard techniques may not ensure life cycles which are sufficiently long for the power devices supplying electric loads.
"Accordingly, a driving apparatus is described herein for an electric load to address the shortcomings of the standard techniques. The driving apparatus may include a power device having a control terminal and an output terminal for an output current to be supplied to the electric load, and a control module configured to drive the power device in an auto-recovery mode, by switching between activation and deactivation for the occurrence of an overcurrent condition, wherein the output current reaches a threshold current. The control module may also evaluate a first time interval; generate a limit signal when the time interval is equal to a time threshold; and drive the power device to a switching-off condition at least as a function of the limit signal. The time interval is between a time wherein the overcurrent condition occurs, and a first time.
BRIEF DESCRIPTION OF THE DRAWINGS
"To better understand the embodiments and appreciate their advantages in the following some will be described in an exemplifying non-limiting way, referring to the attached drawings, wherein:
"FIG. 1 shows a particular embodiment of an electric system comprising a power device and electric load in accordance with the invention;
"FIG. 2 schematically shows the trend of a start-up current of a resistive load and the trend of the output current of the power device as shown in FIG. 1 in the auto-recovery mode;
"FIG. 3 shows a particular embodiment of a module for detecting the temperature, usable in the driving apparatus;
"FIG. 4 shows, by a flow chart, a first embodiment of a driving method implementable by the driving apparatus of FIG. 1;
"FIG. 5 shows by a flow chart, a second embodiment of a driving method implementable by the driving apparatus of FIG. 1;
"FIG. 6 shows a further particular embodiment of a module for detecting the temperature usable in the driving apparatus for implementing method of FIG. 5;
"FIG. 7 schematically shows different trends of the output current of the power device and a warning signal generated by the driving apparatus, in different possible operative conditions; and
"FIG. 8 refers to computer simulations and shows the output current trend of the power device, the trend of a warning signal and trend of the temperature of the power device in the implementation of method of FIG. 4, in a short-circuit condition."
For additional information on this patent application, see: TORRISI,
Keywords for this news article include: Microcontroller, Stmicroelectronics S.r.l.
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