Patent Application
20220371461
This application claims priority to European Patent Application Number 21174469.3, filed May 18, 2021 the disclosure of which is incorporated by reference in their entireties herein.
Vehicle power distribution systems are used to distribute electrical power from the vehicle's battery and generator or DC/DC-Converter to various powered modules within the vehicle.
In conventional architectures, in order to protect the battery 2 and the powered modules 4 and 10 in the event of a short circuit, a fuse 5 is provided in the charging line 7. As such, if a short circuit causes an excessive current draw through the charging line 7, which exceeds the fuse's threshold, for example 250 amps (A), the fuse 5 may melt thereby preventing the current flow.
There are, however, problems with such conventional architectures. Firstly, if a short circuit 9 occurs on the generator line 8, a relatively high reverse current is drawn from the battery 2, via the battery line 3, through the charging line 7 to the generator line 8. This may cause the voltage on battery line 3 to drop low, which may cause faults in the critical powered module 4. Furthermore, the fuse 5 may melt in this scenario if the battery 6 is sufficiently charged to supply a current exceeding the rating of the fuse 5. If, however, the charge in the battery 2 is relatively weak, the fuse 5 may not melt, thereby resulting in the battery line 3 being held low. Conversely, in scenarios where the fuse 5 does melt, it requires replacement before normal vehicle operations can be restored. Given the complexity of modern vehicles, this is undesirable.
To address the above shortcomings, arrangements have been proposed which replace the melting fuse 5 with a low voltage switch or a number of field effect transistor (FET) switches under the control of a controller. However, when such arrangements are used to switch off relatively high currents, the large amounts of energy fed through the sensor system and the switch can result in damage to the controller and the switches. This can not only compromise their long-term reliability, but also typically necessitates the provision of heat sinks and thermal management systems to maintain their operation. This increases the cost and size of the assembly as a whole.
Accordingly, there is a need for new vehicle power distribution circuits and systems to address the above shortcomings.
The present disclosure relates to a vehicle power distribution circuit and a vehicle power system. In particular, the present disclosure is relevant to a short circuit protection device for automotive power architectures, vehicle power distribution boxes, and vehicle electrical architectures incorporating short circuit protection.
According to a first aspect, there is provided a vehicle power distribution circuit comprising: a charging line connecting a battery to a power line for charging the battery when a forward voltage is applied by the generator or DC/DC-Converter connected to the power line; an ideal diode arrangement provided in the charging line for conducting a forward current from the generator or DC/DC-Converter to the battery when the forward voltage is applied and for preventing conduction of a reverse current from the battery to the power line when a reverse voltage is applied.
In this way, robust and rapid short circuit protection may be provided, without significant power losses. Importantly, by utilising the characteristics of a perfect or ideal diode arrangement, the current at the moment when the short protection activates is effectively zero. As a consequence, unlike conventional arrangements, energy isn't lost during switching, thereby mitigating potential energy losses as heat. At the same time, the battery line is isolated from short circuits on the power line. Although ideal diode arrangements have previously been used to protect circuits when a battery is accidentally connected in reverse polarity, the present disclosure applies their characteristics to provide short circuit protection for reverse currents to the power line in a vehicle power distribution circuit.
In embodiments, the ideal diode arrangement includes: a metal-oxide-semiconductor field-effect transistor (MOSFET) connected in the charging line; and a controller for driving the MOSFET for emulating an ideal diode. In this way, a low forward voltage drop is achieved across the metal-oxide-semiconductor field-effect transistor (MOSFET), whereas a negligible reverse current is conducted in a short circuit scenario.
In embodiments, the MOSFET includes a body, and a gate, and wherein the gate is driven by the ideal diode controller and the body prevents the reverse current when the MOSFET is turned off by the gate.
In embodiments, the controller includes a comparator for comparing the voltage across the MOSFET, wherein the controller drives the gate to turn off the MOSFET when the comparator detects a reverse voltage across the MOSFET. In this way, a reverse voltage can be detected rapidly, using a robust comparator arrangement.
In embodiments, the vehicle power distribution circuit further includes a bypass circuit for bypassing the ideal diode arrangement, wherein the bypass circuit includes a current regulator for regulating a reverse current through the bypass circuit from the battery to the power line. In this way, a regulated reverse current may be provided from the battery.
In embodiments, the bypass circuit further includes a switch for selectively establishing a bypass current path from the battery to the power line. In this way, the regulated reverse current may be selectively provided when needed.
In embodiments, the bypass circuit path is established for enabling non-critical power modules to draw power from the battery.
According to a second aspect, there is provided a vehicle power distribution unit including a vehicle power distribution circuit according to any of the above statements.
According to a third aspect, there is provided a vehicle power system, including: a battery; a generator or DC/DC-Converter; a power line for connecting the generator or DC/DC-Converter to one or more powered modules; and a distribution circuit, the distribution circuit including a charging line connected between the battery and the power line for charging the battery when a forward voltage is applied by the generator or DC/DC-Converter, an ideal diode arrangement provided in the charging line for conducting a forward current from the generator or DC/DC-Converter to the battery when the forward voltage is applied and for preventing conduction of a reverse current from the battery to the power line when a reverse voltage is applied.
In embodiments, the vehicle power system further includes a battery line for connecting the battery to one or more critical powered modules.
In embodiments, the ideal diode arrangement includes a MOSFET connected in the charging line, and a controller for driving the MOSFET for emulating an ideal diode.
In embodiments, the MOSFET includes a body, and a gate, and wherein the gate is driven by the ideal diode controller and the body prevents the reverse current when the MOSFET is turned off by the gate.
In embodiments, the controller includes a comparator for comparing the voltage across the MOSFET, wherein the controller drives the gate to turn off the MOSFET when the comparator detects a reverse voltage across the MOSFET.
In embodiments, the vehicle power system further includes a bypass circuit for bypassing the ideal diode arrangement, wherein the bypass circuit includes a current regulator for regulating the reverse current through the bypass circuit from the battery to the power line.
In embodiments, the bypass circuit further includes a switch for selectively establishing a bypass current path from the battery to the power line.
In embodiments, the bypass circuit path is established for enabling non-critical power modules to draw power from the battery.
Illustrative embodiments will now be described with reference to the accompanying drawings in which:
A charging line 7 within the power distribution circuit 1 connects between the battery 2 and the generator or DC/DC-Converter 6 via their respective battery and power lines 3, 8. An ideal diode arrangement 11 is provided in the charging line 7 and is arranged for conducting a forward current from the generator or DC/DC-Converter 6 to the battery 2 arrangement for charging the battery 2. Conversely, the ideal diode arrangement 11 prevents the conducting of a reverse current from the battery 2 to the power line 8 when a reverse voltage is applied.
As is known in the art, a perfect or ideal diode is not a diode in the conventional sense, but is an arrangement of a MOSFET and an ideal diode controller that emulates the behaviour of an ideal diode. Consequently, the arrangement provides very low forward voltage drop and negligible reverse current when a reverse voltage is applied. Within the arrangement, the source and gate of the MOSFET are connected in the charging line 7 such that the MOSFET body blocks the reverse current when the MOSFET is turned off. Conversely, when the MOSFET is on, the forward voltage drops and power dissipation is minimal The switching of the MOSFET is controlled by the driving of the MOSFET's gate by the ideal diode controller, which senses a reverse current through the MOSFET, and drives the gate to turn it off, thereby blocking the reverse current.
In this embodiment, the MOSFET is an N-channel MOSFET, although other MOSFET configurations are possible. The ideal diode controller has an internal charge pump for driving the MOSFET gate higher than its anode, a forward comparator for turning on the MOSFET, and a reverse current comparator for turning off the MOSFET when a reverse current is detected. The reverse comparator monitors the voltage across controller's anode and cathode and, if a reverse current is detected, the MOSFET's gate is shorted with a strong pulldown current. This rapidly provides a strong gate drive to pull down the gate to the source voltage, thereby turning off the MOSFET rapidly. As such, the ideal diode arrangement 11 may provide a rapid response to prevent the conduction of a reverse current through the MOSFET and hence the charging line 7. Furthermore, advantageously, by using a comparator, the shutdown current threshold may be set extremely low, thereby allowing the emulation of an ideal diode response.
In use, the vehicle power distribution circuit 1 provides a forward current path for allowing the generator or DC/DC-Converter 6 to charge the battery 2 (shown right to left in
The components of the generator or DC/DC-Converter 6 are internally protected from short circuits. However, in the event of a short circuit 9 on the power line 8 or within the generator or DC/DC-Converter 6 itself, the voltage in the power line 8 drops lower than the battery 2, thereby applying a reverse voltage across the ideal diode arrangement 11. However, the onset of the current reversal causes the ideal diode arrangement 11 to rapidly turn off the MOSFET thereby preventing a reverse current (shown left to right in
Accordingly, with the above described arrangements a vehicle power distribution circuit and power architecture system may be provided which allows for robust and rapid short circuit protection, without significant power losses. Importantly, by utilising the characteristics of a perfect or ideal diode arrangement, the current at the moment when the short protection activates, is zero or substantially so. As a consequence, energy isn't lost during switching of the MOSFET, which could otherwise cause heating of the circuit.
It will be understood that the embodiments illustrated above shows an application only for the purposes of illustration. In practice, embodiments may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement.
For example, although the arrangement allows for short circuit protection without the need for complex microprocessors, it will be understood that implementations may be used in conjunction with one or more microprocessors, for instance to provide performance feedback and fault monitoring.
Moreover, although a vehicle power distribution circuit has been described in the illustrative embodiments, it will be understood that the circuit may be incorporated into a distribution box or form part of a power distribution system incorporated into a vehicle.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21174469.3 | May 2021 | EP | regional |
