Patent Application
20240300426
Not Applicable.
Not Applicable.
The present invention relates in general to power distribution systems for motor vehicles, and, more specifically, to power control for supplying an upfit subsystem with auxiliary loads added by a consumer as an upfit.
In view of the wide range of electrical devices and systems (i.e., electrical loads) and the various types of electrical power sources (e.g., generators, batteries, power converters and inverters, ultracapacitors, and fuel cells) used in transportation vehicles, electrical distribution and load management is an important aspect of vehicle operation. Certain electrical loads such as powertrain and braking systems are given priority access to electrical power to maintain vehicle responsiveness to driver control. In order to manage the application of power to various loads, a power distribution circuit may be used which is comprised of an electronic module including switching elements, electrical sensors, and a programmable controller which interfaces with the various electrical power sources and electrical loads in the vehicle.
Electrical power sources in a vehicle may include storage batteries, electrical generators, and electrical converters. Both gasoline-powered vehicles and electric vehicles may include a low voltage DC battery for supplying low voltage accessories, acting as a buffer for current surges, and (in the case of gas vehicles) operating a starter motor for a combustion engine (all of which are referred to herein as a start-up battery). The main electrical power source may include a generator driven by a combustion engine or a DC-DC converter which steps down a high voltage from an electric-vehicle battery pack to a nominal DC voltage for low voltage accessories.
Vehicle upfitting involves accessories or add-ons which customize a vehicle, such as adding a tailgate lift, handicap lift, or auxiliary exterior lighting. Police vehicles and pickup trucks are frequently customized with upfits. Some upfits may include self-contained power supplies, but many will tap into the original electrical system of the vehicle. To support such installations, vehicle manufacturers may provide a special power distribution box as original equipment on a vehicle in order to distribute main electrical power to multiple fuse-protected branch circuits. The upfit distribution box may be fed from a master power distribution module through a built-in relay in the main module so that if upfit operation creates an excessive power draw then the flow of electrical power from a main power bus can be interrupted (thereby protecting the high priority loads of the vehicle).
Some upfit loads in particular (e.g., a snowplow or a motorized winch) may be more likely to create power surges which may cause tripping of the built-in relay, especially if a user has not installed a recommended upfit battery as part of an upfit subsystem. While the built-in relay may isolate a main electrical power source, the start-up battery may continue to supply the upfit subsystem so that it maintains some functionality. Once a relay has been tripped (i.e., opened), modification of the upfit and then manual resetting of the relay may be required before operation can be restored.
The relay built into the power distribution control module may be a solid-state relay. A common solid-state relay circuit uses field effect transistors (FETs). Solid-state relays may typically be capable of supporting continuous current flow up to about 250 amps and brief surge current up to 400 amps. The main power distribution controller monitors the current and opens the solid-state relay if any prescribed limits are reached.
Compared to a mechanical relay, a solid-state relay may have limitations relating to its ability to repeatedly switch while in a loaded condition. Such limitations are partly due to the inherent generation of heat in the solid-state relay. Therefore, it is desirable to limit the number of times and the frequency at which a solid-state relay is switched. In an upfit subsystem, the user may be unable to ascertain the underlying cause when an interruption or degradation of operation results from the tripping of the relay.
In one aspect of the invention, a vehicle comprises a primary electrical power source and a start-up battery adapted to be recharged by the primary electrical power source. A power distribution circuit defines a main power bus coupled to the primary electrical power source and configured to selectably couple the main power bus to a plurality of priority loads, wherein the power distribution circuit includes a solid-state relay configured to selectably couple the main power bus to the start-up battery. An upfit subsystem is coupled to a junction between the solid-state relay and the start-up battery, wherein the upfit subsystem comprises a relay configured to selectably couple power received from the junction to at least one upfit load. Sensors monitor a first voltage at the junction and a second voltage at the main power bus. The solid-state relay is configured to open when an electrical output from the main power bus to the junction exceeds a tripping threshold. The solid-state relay is further configured to reclose after (A) a first voltage at the junction stabilizes at or above a predetermined voltage, and (B) a second voltage from the primary electrical power source at the main power bus is adjusted to match the first voltage.
Embodiments of the present invention are adapted for electric power distribution in road vehicles (e.g., combustion-engine vehicles and electric-powertrain vehicles) which include an upfit power supply system which can connect vehicle electrical power to upfit subsystems of the types used in vehicle customization, such as in police vehicle accessories, plow trucks, bucket trucks, or pickup trucks with a tailgate lift, a winch, exterior lighting, or other electrical accessory. A main power distribution circuit may include a portion which is configured to deliver power to an engine-compartment mounted fuse box, for example. Because of cost and/or packaging limitations, the upfit portion of the main power distribution controller (PDC) module may be limited to providing current to the upfit subsystem no more than 200 amps continuous (250 amp current surges). Large plows or lifts may draw more current than this, especially if a recommended, dedicated upfit battery has not been installed is the upfit subsystem. Current in excess of the limit will trip a protective relay in the PDC, thereby cutting off the upfit subsystem (as well as the vehicle's storage battery) from the main source of electrical power such as a DC-DC converter which taps power from the high voltage battery pack of an electric vehicle to supply a lower voltage to various vehicle accessories and to recharge the storage battery. The protective relay in the PDC may be a FET relay of a type which is not intended to be opened and closed for an excessive number of times (or at an excessively high repetition rate) when under electrical load.
Various sensors may be used to characterize operation of the electrical system, including having battery management sensors (BMS) associated with the vehicle start-up battery and the upfit battery (if present). The batteries may each be protected by a fuse. When the PDC FET relay has tripped (e.g., due to an electric upfit motor starting), the PDC or another electronic controller measures, stores, and graphs the upfit current and/or voltage trajectory which is then displayed to the user on a touchscreen or other display screen in the vehicle to show the electrical drops and/or spikes being caused by upfit operation. The trajectory display can also be initiated when an upfit load approaches within a predetermined percentage (e.g., 10%) of the maximum continuous running current or the maximum surge current of the FET relay. These displays may also be useful for developers/installers of upfitter equipment to help ensure the upfit operates within the available electrical supply.
When the FET relay is tripped, an audio tone may be generated (using interior speakers or an exterior sound exciter), and a warning message may be displayed on the touchscreen. The warning may also comprise a graph of current flows from either or both of the FET relay and the BMS. Data representing the last several tripping events can be stored for later recall, enabling a user to identify what is going on with their vehicle.
In order to restore main electrical power to the upfit subsystem, the start-up battery voltage is monitored. Once the voltage recovers to a predetermined voltage and is stabilized (indicating that the surge is over) then the voltage from the main source (e.g., the DC-DC converter) is decreased to the level of the stabilized voltage and then the FET relay is reclosed. The predetermined voltage is a voltage level which is sufficient to enable proper operation of the main priority loads of the vehicle. This allows the DC-DC converter to again support the load. Once the FET relay is closed, the output voltage of the main source is dynamically raised until either the maximum current for the FET relay is reached (e.g., 200 amps) or a nominal battery charging voltage is reached. If current flowing from the start-up battery gets close to blowing a battery fuse then a relay between the battery and the upfit subsystem (e.g., a mechanical relay) is opened. In another embodiment, upfit relays in the upfit subsystem can be selectably controlled in a priority order (as established by the user) to prevent tripping the FET relay. In another embodiment, if the FET relay is opened/closed too frequently (x number of times in a time period y) then a warning can be generated and a supplemental reset time could be implemented before a reclosed of the FET relay to slow down the frequency. The same measures can also be applied to the optional upfit battery and/or relay.
Referring to
PDC 13 may be comprised of an electronic module comprised of an integrated microcontroller or other logic circuits for performing power distribution functions, and/or PDC 13 may be coupled with a main controller 18 for sharing some or all of the computation and control functions.
PDC 13 may control many different circuits or branches, each branch supplying different loads or subsystems. Each branch may have a respective relay built into PDC 13 or controlled by PDC 13 for selectively energizing different branches.
One function of PDC 13 may be to provide current from sources 14 and 17 to a low-voltage start-up battery 21. Battery 21 is configured to supply various low voltage (e.g., 12 volt) accessories and/or to provide power to a starter motor for starting an internal combustion engine. Start-up battery 21 can be recharged through a solid-state FET relay 20 in PDC 13 via a fuse 23. Likewise, FET relay 20 can be closed to supply main power from main power bus A to other low voltage DC loads (not shown) that may be connected to a junction B between FET relay 20 and start-up battery 21.
A sensor 22 monitors battery 21 and provides various parametric data including battery current and battery voltage to PDC 13 and/or main controller 18 over a multiplex bus 19. Main controller 18 is further connected to a human machine interface (HMI) 24 which is further connected to an audio loudspeaker 25. PDC 13 includes additional sensors or monitoring circuitry (and/or may also be in communication with other electrical sensors in vehicle 10) to quantify voltage and current flow at various locations, such as at FET relay 20, main source 14, and main power bus A.
PDC 13 is coupled to a relay 26 (e.g., a discrete mechanical relay) to selectively couple electric power from junction B to upfit subsystem 12. Upfit subsystem 12 may include a plurality of upfit loads 27 via a plurality of upfit relays 28. Upfit loads 27 may be connected in separate branch circuits which are selectably coupled to power from junction B by respective individual relays within relays 28. In some upfit installations, an up fit battery 30 (having a corresponding upfit battery sensor 31) is connected in parallel with battery 21 to provide additional electrical power to the input of upfit relays 28. An upfit controller 32 and a user interface 33 are configured to enable manual control of relays 28 in order to selectively activate upfit loads 27. Upfit controller 32 may be communicatively coupled with PDC 13.
A warning event and/or a tripping event can also be determined based on current flow to the upfit subsystem. For a warning event, current is monitored to detect instances when the current closely approaches a maximum permissible limit. When this occurs, a warning is generated to a user in order to inform them that a contemporaneous action taken by the upfit subsystem has come close to causing a power interruption.
For a tripping event,
After tripping of the solid-state relay, the present invention attempts to reclose the solid-state relay in order to support the desired use of the upfit subsystem once the event that caused the power surge has ended. Furthermore, the re-closing of the solid-state relay is performed in a manner which avoids harmful stress on the solid-state relay.
After making the warning, the invention attempts to reclose the solid-state relay by waiting for the upfit-side voltage to stabilize in step 73. To be considered stabilized, the voltage needs to recover at or above a predetermined voltage. Once the voltage is stabilized, then the output voltage from the main electrical power source is decreased in step 74 in preparation for re-closing the solid-state relay. The decrease continues until it matches the level of the stabilized voltage at the upfit side, and then the relay is re-closed in step 75. Once the relay is re-closed, current draw and voltage continue to be continuously monitored to ensure that adequate power continues to be available for the high-priority vehicle electrical loads and to ensure that the start-up battery is protected from excessive depletion. Thus, a check is performed in step 76 to determine whether the current through the solid-state relay and the current through the battery are at acceptable levels. If current flowing from the startup battery to the upfit subsystem is excessive, then the mechanical isolation relay is opened in step 77. Excessive battery current is a level of battery current that approaches a tripping current of the battery fuse. If current flowing through the solid-state relay is excessive, then it is re-opened in step 77. If no excessive currents have begun to flow, then the output voltage from the main power source is caused to ramp up in step 78. A check is performed in step 79 to determine whether the ramping up of the main source voltage has returned it to the nominal level. If not, then a return is made to step 76. Once the nominal main source voltage is reached, then further ramping up is discontinued and normal monitoring is restored.
In another embodiment, additional actions may be taken in the event that the upfit subsystem as a whole continues to draw an excessive current that prevents re-closing of the solid-state relay. In some embodiments, the upfit subsystem may have multiple different loads controlled by different respective upfit relays which can selectively operate some loads at a higher priority than other loads. Thus, a check is performed in step 85 to determine whether the upfit-side voltage is stabilized at a supportable level while the solid-state relay is still in an open state. If it has not, then a check is performed in step 86 to determine whether there are multiple upfit relays. If not, then the solid-state FET relay remains open at step 87. Otherwise, a user-defined priority scheme may be used to open a subset of the upfit relays in step 88 for the low priority loads in order to reduce the current drawn by the upfit subsystem to a supportable level. Then a return can be made to re-close the solid-state relay.
