Patent Application
20160087317
This application relates to a structures and methods for controlling a traction battery heater and for heaters for high voltage side applications in hybrid electric vehicles.
Some hybrid or electric vehicles require heat to keep the high voltage batteries in their operating range.
A vehicle high-voltage side heater system is described. An example of such a system can include a controller to input a modulated control signal from a low-voltage side and a high-voltage side heater. The heater can be electrically coupled to the controller and controlled by the modulated control signal from the controller to connect a high voltage to the high-voltage side heater. In an example, the controller is isolated from the high voltage side power.
In an example, the controller includes a power supply, control logic circuitry and a driver, all electrically coupled to provide the modulated control signal in response to a modulated input signal at the low-voltage side.
In an example, the modulated control signal is a pulse width modulated signal.
In an example, the low-voltage side is at 12 volts.
In an example, the high-voltage side is greater than 100 volts and includes a traction battery.
In an example, the high-voltage side heater is selectively connected to the high-voltage based on the modulated control signal.
In an example, the controller includes an electrostatic discharge circuit receiving an input signal from the vehicle circuitry requesting operation of the high-voltage side heater.
In an example, the controller includes an electro-magnetic inference limiting circuit that is electrically connected to the electrostatic discharge circuit.
In an example, the controller includes a low dropout regulator connected to the electro-magnetic inference limiting circuit and configured to output a transformer driver signal.
In an example, the controller includes a transformer circuit receiving the transformer driver signal and configured to output a high-voltage side switch control signal.
In an example, the controller includes power transistor that is controlled by the high-voltage side switch control signal to selectively connect the high-voltage side heater to the high-voltage side power.
Various methods are described and some exemplary methods can be used with the structures described herein. A method of controlling a high-voltage side heater in a vehicle can include receiving a modulated control signal on a low-voltage side and filtering the modulated control signal on the low-voltage side. The method can further include outputting a driver control signal based on the filtered modulated control signal on the low-voltage side. The method can further include driving a transformer based on the driver control signal on the low-voltage side and switching the high-voltage heater between on and off states based on a signal from the transformer.
In an example, none of the steps on the low-voltage side are directly connected to low-voltage power.
In an example, filtering includes limiting electrostatic voltages and electro-magnetic interference transients in the modulated control signal.
In an example, outputting the driver control signal includes outputting a sense signal and a reset signal based on the filtered modulated signal a threshold adjustment signal, a reset delay signal, and a sense input signal.
In an example, outputting the driver control signal includes applying to the sense signal and the reset signal to logic circuitry to produce the driver control signal that is “on” when the high-voltage heater is to be off and “off” when the high-voltage heater is to be on.
In an example, outputting the driver control signal includes using the reset delay signal for under-voltage lockout to protect a high-voltage side switch performing switching the high-voltage heater between on and off states by keeping the high-voltage side switch from its linear operating region.
In an example, outputting the driver control signal includes applying hysteresis on the state of the sense input signal to reduce effects of noise and ripple on the modulated control signal.
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
The driver circuitry 204 can include a driver circuit to produce a signal to apply to a transformer. The driver circuit can output a 200 KHz signal to the transformer or two each of the two coils in a dual primary coil configuration. The transformer can step up the power from a primary input to a secondary output. The transformer can be a dual primary coil with a single secondary coil to be able to operate at close to a 50% duty cycle and can operate at a lower voltage than a single primary coil. Such a transformer can operate in a push-pull operation where the two primary coils operate opposite each other. The secondary output can further be conditioned before being applied to a switch 206 that applies high side voltage to a heater 208. The transformer can further operate to isolate the low-voltage side components from the high-voltage side power.
In the
At 405, the modulated control signal can be filtered and processed to reduce the effect of stay signals, e.g., electro-magnetic interference and/or electrostatic signal input. It will be appreciated that various capacitors and resistors can be positioned on the input line and selected to damping or eliminate high frequency signal components, e.g., greater than 1 KHz, and high voltages, e.g., greater than 100 volts or 10 of volts greater than the input modulated control signal. The various electrical elements can be chosen based on the value of the input signal and other component values as is known in the art.
At 407, a driver control signal is output based on the filtered modulated control signal. In an example, an integrated circuit can receive the filtered modulated control signal as an input signal. The integrated circuit can receive a sense input signal that is the filtered modulated control signal that is passed through a voltage divider. The integrated circuit can further receive a delay signal to control how fast the integrated circuit switches the output. The integrated circuit can further receive a reset signal that is set by a voltage divider network. The reset function can be activated during a power up sequence or during normal operation if the output voltage drops outside the set limits. The reset threshold voltage can be decreased by the connection of an external resistor divider to a reset lead on the integrated circuit. The integrated circuit can be protected against reverse battery, short circuit, and thermal overload conditions, and can withstand load dump transients making it suitable for use in automotive environments. The selection of the reset threshold voltage the reset signal can provide hysteresis when producing the output based on the modulated control signal. In an example, the integrated circuit produces two output signals that can be passed to logic circuits to produce the driver control signal. In an example the integrated circuit produces a reset output signal and a sense output signal, which are supplied to a NAND gate with its output to the transformer driver.
At 409, the transformer is driven based on signals from step 407. Accordingly, as the input and output from step 407 are pulse modulated signals at the low-voltage side, the input to a transformer driver is also pulse width controlled and modified by the reset signal. In an example, an integrated circuit driver is provided and it sends driving signals to a two coil primary side of the transformer. These driver output signals work in opposition so that the two coil primary side operates in a push-pull configuration with the single coil secondary. The integrated circuit can output a signal when its input from step 407 is off and not output signal when its input from step 407 is positive.
At 411, the transformer output is applied to a switch at the high-voltage side. This switch selectively connects the HV heater to the HV power. In an example, the HV switch is a power MOSFET with the transformer output connected to a gate of the power MOSFET. In an example, the HV heater has one terminal connected to the positive HV power supply and another terminal connected to a drain of the power MOSFET. The source of the power MOSFET is connected to the HV negative terminal. Accordingly when the switch is conducting, i.e., gate is powered; the HV power is applied to the HV heater. When in the switch is off, then a flywheel diode connected from the drain to the HV positive terminal in parallel with the heater protects the heater.
The above described embodiments address the need to control a HV-side heater with a control signal from the low voltage (LV) side. It is within the scope of the present disclosure to use the teachings of the present disclosure to control HV loads other than heaters. This can be desirable when it is easier to build LV side circuitry to control loads on the HV side. However, the LV circuitry can be galvanically isolated from the HV side power.
It will be recognized that in some embodiments, the elements on the low side are not connected directly to the low voltage on the low side. The input signal is used to derive the signal to the transformer to switch the HV side switch that connects the high voltage on the HV side to the heater. It will be recognized that when integrated circuits are used, then they may be connected to an IC rail, e.g., 5 volts or 3.3 volts, and not directly connected to the LV side power. However, the IC rail can be derived from the LV side power.
The present inventors have found that the presently described design provides various benefits. Some of which include, but are not limited to, the reduction in the number of inputs required to drive and control the HV heater. The circuitry to drive and control the HV heater can be assembled in to a single module that has an input signal from the LV side and connects the heater on the HV side. In an example, single module need not include the heater. The heater can be a component of the battery pack with connections to the output of such a single module. Moreover, there is no need to connect the single module to the LV power terminal directly, e.g., there is no direct connection to the positive LV side power rail. Such a compact design can accommodate 2 kWatt heater power as it is on the HV side and uses a HV power switch to connect the heater to the HV supply.
It is further recognized that various examples do not require a heat sink as the components do not operate directly on the LV supply of the vehicle and only the power switch and the heater are subject to the HV supply.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.
