Electric lamp and discharge devices: systems – Special application
Reexamination Certificate
2000-07-13
2001-12-11
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Special application
C315S307000, C361S090000
Reexamination Certificate
active
06329754
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention involves a diagnostic system for a ballast of a high-pressure gas discharge lamp for a motor vehicle, having a light control module, which connects the ballast to an operating voltage source and monitors current reception of the ballast, and with the ballast, having: a voltage converter for supplying voltage to the high-pressure gas discharge lamp, a safety circuit for recognizing fault functions of the ballast and the high-pressure gas discharge lamp and turning the voltage converter off in case of a fault, and a diagnostic circuit for generating a fault signal in case of a fault.
Increasingly in more and more motor vehicles, illumination devices are being switched on or off via a light control module. A light control device for a motor vehicle is disclosed in DE 43 41 058 C1, with this example showing that a device of this type can be very complex. That is, here both a light control module as well as a lamp module are structured as “intelligent” structural assemblies, i.e. provided with a microcomputer, such that this type of light control device is quite expensive. Particularly in motor vehicle technology, however, constructions of light control devices that are especially simple are preferred for cost reasons.
For the most part, a light control module has a device for current control, which indicates to a vehicle driver, if incandescent lamps are controlled for example, whether an incandescent lamp must be changed. This is problematic in the control of high-pressure gas discharge lamps, which are increasingly used in motor vehicles, since they are driven by a ballast. In high-pressure gas discharge lamps, the light control module can not namely distinguish whether the lamp or its associated ballast is defective. Thus, it is advantageous, if the ballast takes over the diagnostics and transmits data to the light control module.
Standard commercial ballasts for high-pressure gas discharge lamps, for example such as those of the assignee, have for this purpose a diagnostic output, which is connected to the light control module via a diagnostic line. The cable expense for an additional diagnostic line per ballast thus causes additional costs, and this is also true for structural components for the output of diagnostic signals (output drivers, possibly even a microprocessor) within the ballast, with these additional costs accruing even if the diagnostic possibility is not to be used in a motor vehicle.
It is thus an object of this invention to create a diagnostic system for a ballast of a high-pressure gas discharge lamp in a motor vehicle, which is especially uncomplicated and inexpensive in structure.
SUMMARY OF THE INVENTION
According to principles of the invention in case of a fault, a diagnostic circuit modulates, as a function of the type of the fault that has occurred, current reception of a ballast using a switchable current sink and a light control module transforms the modulated current into a voltage signal and recognizes the type of the fault that has occurred from the voltage signal.
The diagnostic device of this invention thus advantageously does not require its own diagnostic line, since the diagnostic information is transmitted through a quiescent-current modulation on the supply line of the ballast.
Moreover, the expense of structural parts, for creating, transmitting and evaluating the diagnostic information in the ballast and in the light control device, is extremely small. Thus, no additional special outputs and inputs are required for the diagnostic information.
Additional advantageous embodiments and further developments of the diagnostic system of this invention result from the dependent claims.
Thus, the modulated quiescent current can advantageously be transformed, via a resistor that is connected in the supply line or via an output resistor of a current mirror circuit, into a voltage signal, which is captured at an input of switching and evaluation logic and evaluated by the switching and evaluation logic as to the type of the fault that has occurred.
The modulation of the quiescent current can advantageously be a pulse-width modulation at a low frequency, since this is not affected by a filter that eliminates high-frequency interfering pulses of the ballast (EMC filter).
It is especially advantageous for the diagnostic signal to be a square wave frequency with a defined pulse width. By allocation of a specific frequency to each possible fault, a simple coding of the faults can be achieved. In this way, the diagnostic data can be decoded both from frequency as well as from average value of the signal voltage.
Likewise, it is of special advantage for a fault-dependent modulation of this type to also be created in a ballast “without intelligence”, that is, without its own microcomputer, such that the ballast can be structured to be especially cost-effective. A microcomputer is only provided for the switching and evaluation logic of the light control module.
Furthermore, it is advantageous to display faults that have occurred to the driver in a display element, and furthermore, to save them also for later fault analyses in a fixed memory register (EEPROM).
REFERENCES:
patent: 5151631 (1992-09-01), Oda et al.
patent: 5347224 (1994-09-01), Brokaw
patent: 5452173 (1995-09-01), Brannon et al.
patent: 5751115 (1998-05-01), Jayaraman et al.
patent: A5291873 (1991-07-01), None
patent: A1-4343747 (1994-06-01), None
patent: C1-4341058 (1995-04-01), None
patent: A1-49200579 (1992-01-01), None
Daub Wolfgang
Radtke Volker
Hella KG & Hueck Co.
Tran Thuy Vinh
Wong Don
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