Note: Descriptions are shown in the official language in which they were submitted.
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TRAILER SIGNAL CONVERTER
FIELD OF THE INVENTION
The present invention relates to a device for transmitting and converting
signals, and
more specifically to a device for transmitting and converting signals from a
towing
vehicle to a towed vehicle.
BACKGROUND OF THE INVENTION
Towed vehicles, such as trailers, have brake signals that operate based on the
braking
signals of the towing vehicle. As is well known in the art, the braking
signals of the
towing vehicle are electrically connected to the braking system of the towed
vehicle,
such as via an electrical adapter, or the like. Typically, the signaling
system of the
towing vehicle has a signal lamp and a brake lamp that are operated by at
least two
separate filaments. However, most trailer signal systems usually combine the
turn and
brake signals into a single lamp with a single filament. Accordingly, an
adapter or
circuitry is required in order to interface the signal system of the towing
vehicle with
the signal system of the towed vehicle or trailer.
Adapters that interface the signaling system of the towing vehicle and their
respective
towed vehicle or trailer are well known. Most adapters use the power from the
signal
system of the towing vehicle to power the signaling system of the towed
vehicle. In
order to accomplish this, the adapter must increase the amount of current from
the
towing vehicle signaling system to the towed vehicle signaling system.
However,
there are many disadvantages to such adapters.
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One such disadvantage of known converters is that they do not have adequate
safety
and back-up features. For example, traditional converters typically do not
have
adequate overload and short circuit protection. As a result, traditional
converters
present a risk due to overheating should the load on the output exceed the
rated load.
Frequently, towed vehicles or trailers may have marking lights added to the
taillights,
for example, that may further increase the load on the output of the tail
channel of the
signaling system and, thus, the probability of exceeding the rated load of the
output is
quite possible. Traditional converters that have a means to detect short
circuits may
not have an automatic reset function wherein upon removal of the short circuit
the
converter starts normal operation.
Moreover, known adapters or converters fail to adequately protect the adapter
if the
load at the output exceeds the ratings of the converter. The failed attempts
of known
converters involve implementing thermal protection on the output driver.
However,
the thermal protection of the converter is a remedial measure. Thermal
protection
does not prevent the potential or eventual problem that causes overheating.
Additionally, these known converters fail to detect short circuits and, as a
result, can
be damaged due to short circuit conditions.
Devices have also been developed that illuminate the signaling system of the
towed
vehicle with power signals separate from the towing vehicle signaling system.
For
example, solid state switching devices, such as transistors, relay coils, or
other types of
signal detection devices, may be used. However, these devices also have many
disadvantages. For example, these devices can be damaged due to high power
dissipation such as caused by high currents during overload or short circuit.
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The towing vehicles may use a single bulb to indicate STOPLIGHT and TAILLIGHT
functions. This is done by driving the light continuously for STOPLIGHT and
for a
partial time for TAILLIGHT. When a towed vehicle with known converters is
connected to such towing vehicles, the TAILLIGHT may not function properly,
may
be very dim or flash.
Thus, the known converters are not capable of driving the lighting system of a
towed
vehicle to indicate a combined STOPLIGHT and TAILLIGHT bulb or light system.
In addition, the prior art utilizes "smart drivers" that integrate all
functions of a charge
pump, current sense, temperature sense, or combinations thereof onto a single
die.
That makes the cost of these "smart drivers" very expensive. Not to mention
that the
consumer must take these drivers with all of the manufacturers specifications
without
a choice or any options. If the functions were separated, they could be
tailored or fine
tuned by the consumer for the specific application they were purchased for.
Therefore, there is a need in the art for an improved trailer signal converter
or adapter.
The present invention seeks to overcome many of the shortcomings of known
adapters
and circuitry for connecting the signaling system of the towing vehicle with
the
signaling system of the towed vehicle.
DESCRIPTION OF THE DRAWING
Objects and advantages together with the operation of the invention may be
better
understood by reference to the following detailed description taken in
connection with
the following illustration, wherein:
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FiGURE 1 illustrates a block diagram of an apparatus and system for connecting
the
signaling system of a towing vehicle to the signaling system of a towed
vehicle in an
embodiment of the present invention.
SUMMARY OF THE INVENTION
A signal converter that may include a power supply, a microcontroller and a
current
sensing device. The microcontroller may be connected to the power supply, and
may
be configured to receive a plurality of inputs from a first vehicle, and
output a plurality
of output signals to one or more loads of a second vehicle. The current
sensing device
may be connected to the microcontroller to monitor current flow at the loads.
In
addition, the microcontroller may be capable of reducing the duty cycle of the
output
signal in response to the current flow rising above a first predetermined
threshold, and
resuming the output signal to full strength once the current flow falls bellow
a second
predetermined threshold.
A signal converter that may include a power supply, a microcontroller and a
current
sensing device. The microcontroller may be connected to the power supply. The
microcontroller may also include a plurality of input channels to receive
input signals
from a first vehicle and a plurality of output channels to send output signals
to one or
more output devices of a second vehicle. The current sensing device may be
connected to the microcontroller to monitor the current drawn by the output
devices.
The output channels may be configured to stagger activity on the output
signals. In
addition, the microcontroller may be capable of limiting the power of the
output
signals in response to the current draw rising above a first predetermined
threshold,
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and resuming the output signal to full strength once the current draw falls
bellow a
second predetermined threshold.
A method of converting a signal that may include receiving an input signal,
sending an
output signal, measuring current flow, measuring temperature, reducing the
power of
the output signal, and restoring the output signal. The output signal may be
received
from a first vehicle at an input channel of a microcontroller on a signal
converting
device. The output signal may be sent to an output device of a second vehicle
from an
output channel of the microcontroller in response to said input signal. The
current
flow may be measured at the load while the output signal is being sent to
determine
the presence of a circuit fault. The temperature of the signal converting
device may be
measured. The power of the output signal may be reduced in response to a
circuit
fault or in response to the temperature rising above a first predetermined
threshold.
The output signal may be restored to full strength once the circuit fault is
removed and
the temperature is below a second predetermined threshold.
DETAILED DESCRIPTION
While the invention is described herein with reference to several embodiments,
it
should be clear that the invention should not be limited only to the
embodiments
disclosed or discussed. The description of the embodiments herein is
illustrative of the
invention and should not limit the scope of the invention as described or
claimed.
With reference to FIGURE 1, an embodiment of an adapter or trailer signal
converter
10 is provided. The adapter 10 may be used to transmit signals and/or convert
signals
from a signaling system of a towing vehicle to a signaling system of a towed
vehicle
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or trailer. The towing vehicle may be, for example, an automobile, a truck, a
tractor or
any other appropriate type of towing vehicle having a signaling system. The
towed
vehicle may be a cargo trailer, a livestock trailer, a vehicle trailer or any
other
appropriate type trailer or vehicle capable of being towed that has a
signaling system,
such as a brake and/or turn signal.
Unlike the prior art, the adapter or trailer signal converter 10 may detect
the presence
of overload and short circuit and takes action to protect the converter 10
from
overheating. The adapter 10 may do so by reducing the duty cycle of the output
drive.
In addition, should the fault in the output be removed, the converter 10 may
automatically detect that without resetting it and start driving the output
loads
normally again. In addition, the trailer signal converter 10 may also separate
the
control of various functions, such as a current sense, charge pump, power
drive with
low heat dissipation and temperature sensing, and the like, for example, so
that the
consumer may tailor them to their own specifications or fine tune the
functions for a
specific application.
The trailer signal converter or adapter 10 may include a circuit board 12
having an
input 14 and an output 16. As illustrated in FIGURE 1, the adapter 10 may have
the
input 14 on one side of the circuit board 12 and the output 16 on the opposing
side of
the circuit board 12. It is to be understood, however, that the input 14 and
the output
16 may be positioned at any appropriate location on the circuit board, such as
on the
same side of the circuit board 12. The input and the output 16 may also be
implemented by using one or more connectors (not shown).
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The circuit board 12 may be assembled into a box (not shown) and potted using
any
appropriate type of material. Preferably, the circuit board 12 may be potted
using a
material that is suitable to protect the components from thermal cycling. In
addition,
the circuit board 12 may be overmolded as an alternative. In use, the box may
be
mounted or otherwise positioned in the interior or on the exterior of a towing
vehicle.
A power supply 18 may be incorporated into the circuit board 12. The power
supply
18 may be of any appropriate type, but the power supply 18 may preferably be
derived
from the power supply of the towing vehicle. The power supply 18 may power a
microcontroller 20 and the associated circuits of the trailer signal converter
or adapter
10, as shown in FIGURE 1. The power supply of the towing vehicle may also
provide
power to the adapter 10 and may work in combination with the power supply 18
to
power the adapter 10.
The microcontroller 20 may store data, such as a program, or the like, in
memory,
such as, flash memory, for example. The data may be software that may be
utilized to
control the operation of the trailer signal converter or adapter 10. The input
14 may be
in communication with the microcontroller 20. For example, the microcontroller
20
may analyze signals from the input 14. The signals at the input 14 may be
defined by
channels, such as a left turn channel, a right turn channel, a stop light
channel, a tail
channel, a backup channel, and the like.
The output channels 16 may be activated or turned on at staggering intervals
or times
in order to reliably detect problematic conditions that may exist at the
output 16 of the
adapter or trailer signal converter 10, such as an over load or a short
circuit. In an
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embodiment, the microcontroller 20 may implement "exclusive OR" logic with
STOPLIGHT and TURN channels to transmit or convert the signal to the output
16.
Alternately, the output TURN signals in 16 may be in synchronization with the
input
TURN signals in 14.
One of ordinary skill in the art will appreciate that other appropriate logic
may be used
to transmit or convert signals from the towing vehicle to the towed vehicle.
Advantageously, the microcontroller 20 may also determine a short circuit or
excessive load on the output 16 by reading the outputs of a current sense 26,
as shown
in FIGURE 1. Any appropriate device, such as a sampling resistor or a printed
circuit
trace, may be used as the current sense 26.
For example, the microcontroller 20 may determine the amount of current in the
load
to determine the presence of an overload or a short circuit at the output 16.
More
specifically, the microcontroller 20 may compare the amount of current at the
output
16, at a specific time after turning the corresponding output 16 ON, to a
known current
or a predetermined current at the output 16 to determine the presence of an
excessive
load or short circuit.
Based on the amount of current, the microcontroller 20 may control various
components of the microcontroller 20. As an example, the microcontroller 20
may
turn the output 30 off. The microcontroller 20 may then retry again after a
predetermined time interval, for example, two (2) seconds, or the like. The
microcontroller 20 may then resume normal operation if the microcontroller 20
does
not detect an overload or short circuit after the retry.
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In conserving power or otherwise controlling the trailer signal converter or
adapter 10,
the microcontroller 20 may monitor the voltage or the current from the power
source
of the signaling system. With further reference to FIGURE 1, a current sensor
26 may
be in communication with the microcontroller 20. The current sensor 26 may
monitor
the current transmitted to the output 16. The current sensor 26 may comprise,
for
example, a sampling resistor or a printed circuit trace. The current sensor 26
may also
monitor the current prior to turning the channel on and after turning the
channel on.
Accordingly, the current sensor 26 may monitor the current to detect open,
overload or
short circuit conditions.
For example, some signaling systems of towing vehicles have some voltage
present on
the stoplight channel input even when the stop light channel input is not
active. The
stoplight channel and tail channel may use analog inputs. The threshold at
which the
analog inputs of these channels is recognized as active may be programmed into
the
microcontroller 20. Thus, in an embodiment, the stoplight input may only be
recognized as active when the voltage exceeds a predetermined threshold. By
determining the analog voltage level of the tail channel at the input 14,
issues or
problems with voltage drop along the input 14 may be identified and remedied.
The microcontroller 20 may further include memory. The memory may be of any
appropriate type, such as Electrically Erasable Programmable Read-Only Memory
(EEPROM). EEPROM is a type of non-volatile memory that may be used in
computers and other electronic devices to store small amounts of data that
must be
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saved when power is removed, e.g., calibration tables or device configuration.
The
EEPROM may be used for calibration of the current on each channel of the input
14
and/or the output 16. Since the current sensor 26 detects current, the current
sensor
can be calibrated and the calibration factor may be stored on the memory of
the
microcontroller 20. The memory of the microcontroller 20 may store software or
other logic to operate the trailer signal converter or adapter 10.
In an embodiment, temperature sensor 28 may provide temperature sensing by,
for
example, use of a thermistor, such as a Negative Temperature Coefficient (NTC)
thermistor. In a NTC thermistor, the resistance may decrease with increasing
temperature. The temperature sensing 28 may be a separate component(s) to the
microcontroller 20 and may be located at a different and even multiple
locations on the
adapter 10. For example, the temperature sensor 28 may be located adjacent to
the tail
output drive of 30.
The temperature may be used by the microcontroller 20 in determining whether
to turn
the power off at the output 16, whether to limit the power at the output 16,
such as by
pulse-width modulation (PWM) or any other appropriate method known to one or
ordinary skill in the art, or whether to take some sort of other action. The
channels at
the output 16 may reactivated or otherwise be turned back on when the
temperature
returns to a safe value or drops below a predetermined value. The current and
voltage
may be sensed at a predetermined time after first transmitting the power to
the output
16. The temperature may be sensed periodically.
In some towing vehicles, for example, PWM may be used on the tail channel so
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the same light can be used on the stoplight channel and the tail channel. The
stoplight
may turn ON with continuous voltage, whereas the tail may be turned ON using
PWM
to reduce the intensity of the light. Also, some towing vehicles use pseudo-
multiplex
signals that require decoding or conversion back to conventional signals to
drive the
towed vehicle signaling system.
In an embodiment, the microcontroller 20 may detect the PMW/pseudo-multiplex
scheme on the channels of the input 14 and drives of the outputs 16 for the
signaling
system of the towed vehicle. The towed vehicle may use same light for turn and
tail
channels. With reference to FIGURE 1, the microcontroller 20 may be programmed
to send signals, such as PWM/pseudo-multiplex signals to the gate drive 24.
The microcontroller 20 may be programmed to detect various PWM/pseudo-
multiplex
schemes that may be used by the towing vehicle. For example, the
microcontroller 20
may receive a single PWM/pseudo-multiplex signal that contains information
related
to the stop light signal, tail light signal, and left turn light signal on the
left turn input
line and information related to the stop light signal, tail light signal, and
right turn
signal on right turn input line. The microcontroller 20 may be programmed to
automatically detect the presence of this PWM/pseudo-multiplex signal scheme
and
decode the stop light signal, tail light signal, and left and right turn light
signals to be
sent to the towed vehicle.
The microcontroller 20 may further be configured to receive and automatically
detect
a PWM/pseudo-multiplex signal scheme on only the stop light input. For
example, the
left and right turn signals may be separate and discrete signals configured as
standard
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high/low voltage inputs, while the stop light and tail light signals may be
provided on
a single input. In an embodiment, the stop signal may be a standard high-low
voltage
signal while tail light signal is a PWM/pseudo-multiplex signal on the stop
light signal
input line. It will be appreciated that the stop light signal and tail light
signal may also
both be PWM/pseudo-multiplex signals. The microcontroller 20 may be programmed
to automatically detect the presence of this signal scheme and decode the tail
light and
stop light signals appropriately to be sent to the towed vehicle.
Depending on the signal transmitted by the input 14, the microcontroller 20
may
activate or "turn on" a charge pump 22 to transmit signals to the output 16.
In
addition, the charge pump 22 may drive a gate drive 24, as illustrated in
FIGURE 1.
In a preferred embodiment, the output drive 26 may be a N-channel Metal-Oxide-
Semiconductor Field-Effect Transistor (MOSFET). A MOSFET is a device that may
be used to amplify or switch electronic signals. The MOSFET may be composed of
a
channel of either N-type (N for negative) or P-type (P for positive)
semiconductor
material. A P-channel MOSFET may be used without a charge pump. The gate drive
24 may also control or switch the power to the output 16. The gate drive 24
may be
composed of switching transistors semiconductor. One of ordinary skill in the
art will
appreciate that any other appropriate schemes and devices may be used in place
of the
gate drive 24 and charge pump 22. Keeping the MOSFET, current sense 26, and
charge pump 22 separate may give an optimum performance in terms of power
dissipation and detecting overload and short circuit on the output channel(s).
Alternatively, the MOSFET may be a smart power MOSFET. The smart power
MOSFET may include an integrated charge pump 22 and current sense 26, thus
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decreasing the number of components of the adapter 10. The outputs of the
current
sense can be used to detect faults such as overload and short circuit.
The output drive 30 may preferably have a low on resistance (RDSon) to
dissipate
power. As a result, heat generation may be maintained at a relatively low
level. In an
embodiment, the charge pump 22 may drive the gate drive 24 of the N-channel
MOSFETs, such as in high-side driving, for example.
With reference to FIGURE 1, the microcontroller 20 may be used to control the
use of
the charge pump 22 to conserve power when the trailer signal convert or
adapter 10
does not require use of the charge pump 22. To keep the quiescent current low,
such
as less than 1 mA, the charge pump 22 may be turned on only when necessary. In
an
embodiment where the current sensor 26, the gate drive 24 and the charge pump
22 are
separate components, the adapter 10 may maximize the performance related to
power
dissipation and detection of overload and short circuits on the output 16. In
addition,
the use of separate components may allow for tailoring and fine tuning of the
adapter
10 to a specific use.
The gate drive 24 and the current sensor 26 may also be in communication with
an
output drive 30. The output drive 30 may be in communication with the output
16 in
order to transmit the signals to the towed vehicle. The adapter 10 may have a
circuit
programming adapter 38 for communicating with the computer 40 to program the
memory in microcontroller 20.
The adapter 10 may reduce its power consumption by entering into sleep mode
after
the inputs have been inactive for a predetermined period of time. While in
sleep mode,
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the adapter 10 may reduce its power consumption by powering down some
components of the adapter 10. The adapter 10 may wakeup from sleep mode once
any
activity is sensed on any input line. Alternatively, the adapter 10 may go to
sleep and
periodically wake up and poll each input line to determine if any inputs are
active and
wakeup the adapter from sleep mode once an active input is detected.
The embodiments of the invention have been described above and, obviously,
modifications and alternations will occur to others upon reading and
understanding
this specification. The claims as follows are intended to include all
modifications and
alterations insofar as they come within the scope of the claims or the
equivalent
thereof.
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