Method and circuit arrangement for comparing output signals...

Details Method and circuit arrangement for comparing output signals... Method and circuit arrangement for comparing output signals...

1999-11-22

2001-06-05

Tong, Nina (Department: 2632)

Communications: electrical

Land vehicle alarms or indicators

External signal light system

C340S475000, C340S458000, C340S661000, C340S664000

Reexamination Certificate

active

06243009

ABSTRACT:

PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 198 54 051.5, filed on Nov. 24, 1998, the entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a method for comparing a measured circuit output signal with reference signals having different reference levels or thresholds. The measured output signals come, for example, from an electronic blinker-hazard flasher circuit. The method is performed in a respective comparator circuit for providing information regarding the operational status of the flasher circuit and its components.
BACKGROUND INFORMATION
Comparator circuits for comparing signals with reference signals are well known in the art, see for example European Patent Publication EP 0,870,646 A1. Present
FIG. 2
corresponding to FIG. 3
a
of the just mentioned European Patent Publication shows an example of a conventional comparator circuit that is used in an electronic blinker, for example for a vehicle. The terms “blinker” or “blinker circuit” in this context refer to that part of the circuit which generates directional or turn signals while the term “hazard flasher” refers to the circuit when it functions as a hazard indicator. These terms may be used in combination or interchangeably.
Present
FIG. 2
shows a comparator circuit for an electronic blinker in which a voltage drop across a measuring shunt resistor represents the current flowing through the blinker circuit. The voltage drop is compared with reference voltages having different voltage levels. The various results of the comparing provide indications or informations regarding the operational status of the blinker circuit, for example whether blinker lamps or bulbs have failed, whether additional bulbs have been connected to the blinker circuit, for example the bulbs of a trailer or whether a short-circuit exists in the blinker circuit.
Referring to
FIG. 2
, the conventional comparator circuit
25
comprises an input terminal
26
that is connected to receive the above mentioned voltage drop from the output of the blinker circuit. The comparator circuit
25
has, for example, four comparators K
1
, K
2
, K
3
and K
4
. One input of each comparator is connected in common to the input terminal
26
. The other input of each comparator is connected to a different reference voltage V
ref1
, V
ref2
, V
ref3
, and V
ref4
. These different reference voltages are generated by respective voltage divider circuits
33
, only one of which is shown in FIG.
2
. The output of each comparator is connected to a respective separate signal debouncing circuit
27
,
28
,
29
and
30
. The outputs of the debouncing circuits in turn are connected to respective inputs IN
1
, IN
2
, IN
3
and IN
4
of a central control unit
31
for further processing. Each comparator with its respective reference voltage V
ref1
, V
ref2
, V
ref3
and V
ref4
forms thus a discrete stage in the circuit. The reference voltages V
ref1
, V
ref2
, V
ref3
and V
ref4
can be generated in any desirable manner, for example with the help of the above mentioned voltage dividers
33
connected with one terminal
32
to a supply voltage and with the other terminal
34
to a reference potential, preferably ground. The size and arrangement of the resistors
33
′ and a rectifier
33
″ will be selected in accordance with the required different reference voltage levels or thresholds.
The just described conventional circuit arrangement has the disadvantage that each discrete stage requires its own comparator, its own reference voltage supply circuit, and its own debouncing circuit, whereby the circuit component requirements multiply rapidly when several input signals are to be compared with a plurality of reference voltages. While the circuit components may be identical circuit components, they still increase the efforts and expense for such conventional circuits and make the respective printed circuit chips more expensive.
OBJECTS OF THE INVENTION
In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:
to provide a method and circuit arrangement for comparing output signals, particularly blinker or hazard flasher circuit output signals with a plurality of different reference signal levels or thresholds in a single comparator to thereby reduce the number of required identical circuit components;
to provide a simple, yet effective monitoring circuit for checking the operational status of another circuit such as a blinker circuit or hazard flasher and its peripheral components such as lamps;
to operate such monitoring circuits with an optimally low power consumption; and
to provide information regarding a short-circuit, operating and/or failed circuit components, and the number of certain components such as lamps.
SUMMARY OF THE INVENTION
According to the method of the invention a measured circuit output signal that contains status information regarding a monitored circuit, is compared in a single comparator with different voltage reference levels or thresholds to ascertain the respective status information. The present method is characterized by the following steps. A control unit provides input control signals to a comparator signal level generator circuit whereby each control signal causes the comparator signal level generator to generate a certain voltage reference threshold or level that differs from other thresholds. The measured output signal from the circuit to be monitored is used as an input signal to the single comparator for comparing with the respective reference voltage level. The comparator output signals are then further processed for evaluation and ascertaining the status information regarding the circuit that is being monitored. Preferably, the output signals from the single comparator are debounced in a single signal debouncing circuit.
The circuit arrangement according to the invention for performing the present method is characterized by a control unit connected with its control output through a conductor to a reference voltage level generator input having an output connected to one input of a single comparator which thus receives different reference thresholds as said one input. The other input of the single comparator is connected to the output voltage of the circuit to be monitored such as a blinker hazard flasher circuit to receive the measured voltage circuit output signal. The output of the single comparator is connected to further circuits for signal processing to ascertain the status information. In a preferred embodiment the output of the signal comparator is connected to a signal debouncing circuit providing at its output a signal for further processing and for displaying or indicating the various status informations of the monitored circuit.
The main advantage of the invention is seen in that by using but one comparator and but one debouncer circuit for processing several input signals, substantial savings are achieved in form of smaller size integrated circuit chips, thereby reducing production costs and the current or power consumption of the monitoring circuit arrangement of the invention.


REFERENCES:
patent: 5801623 (1998-09-01), Chen et al.
patent: 5805061 (1998-09-01), Fritz et al.
patent: 5905439 (1999-05-01), McIntyre
patent: 5907283 (1999-05-01), Kim
patent: 6028512 (2000-02-01), Schropp et al.
patent: 6118384 (2000-09-01), Sheldon et al.
patent: 0870646 (1998-10-01), None

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