The invention is directed to an automotive auxiliary unit with an electronic protection unit comprising an inverse-polarity protection unit and an overcurrent protection unit.

Automotive auxiliary units are commonly provided with an inverse-polarity protection unit and a separate overcurrent protection unit.

The inverse-polarity protection unit avoids supplying inverse-polarity supply voltages to an electric component of the auxiliary unit. The inverse-polarity supply voltage may cause a malfunction of the automotive auxiliary unit or may damage the electric component. Inverse-polarity protection units commonly comprise a semiconductor switch being arranged In the electric feed line of the electric component. The semiconductor switch is highly-conductive in case of normal-polarity supply voltages and is substantially non-conductive in case of inverse- polarity supply voltages. Such an inverse-polarity protection unit is, for example, disclosed in US 6,611,410 Bl.

The overcurrent protection unit avoids providing an overcurrent to an electric component of the auxiliary unit. The term "overcurrent" in this context means any electric current with a higher current level than a specified maximum current level. Particularly, electronic components are very sensitive to an overcurrent and may be damaged when being provided with a too high electric current. Overcurrent protection units commonly comprise a sense resistor with a low and well-defined electric resistance being electrically connected -in series with the electric component. The voltage drop at the sense resistor is evaluated to determine the present current level of the electric current passing the sense resistor and thereby to determine the current level being provided to the electric component. Such an overcurrent protection unit is, for example, disclosed in US 2017/0134017 Al.

It is an object of the invention to provide a compact and cost-efficient automotive auxiliary unit with an inverse-polarity protection and an overcurrent protection.

This object Is achieved with an automotive auxiliary unit with an electronic protection unit with the features of claim 1.

The automotive auxiliary unit according to the invention is provided with an inverse polarity protection unit comprising a semiconductor switch. The semiconductor switch provides a high electric conductance in case of normal-polarity supply voltages and provides a negligible electric conductance in case of inverse-polarity supply voltages. The semiconductor switch is arranged in the electric feed line of an electric component so that an energization of the electric component is avoided in case of an inverse-polarity supply voltage. The semiconductor switch can, for example, be arranged in the electric feed line of a motor control unit or can be arranged between the motor control unit and an electromagnetic coil of an electric motor.

The automotive auxiliary unit according to the invention is also provided with an overcurrent protection unit being electrically connected with the semiconductor switch of the inverse-polarity protection unit. The overcurrent protection unit detects and evaluates the voltage drop at the semiconductor switch to determine the present current level of the electric current passing the semiconductor switch and thereby to determine the feed current of the electric component. This allows providing an overcurrent protection for the electric component without requiring any additional sense resistor or other current sensing element. As a result, the automotive auxiliary unit according to the invention can be provided very compact and cost-efficient.

In a preferred embodiment of the invention, the semiconductor switch is a MOSFET. MOSFETs have a very high electric conductance when being provided with a forward bias voltage and have very low electric conductance when being provided with an inverse bias voltage. In addition, MOSFETs are cost-efficient and can be easily integrated onto circuit boards of automotive auxiliary unit electronics.

An embodiment of the invention is described with reference to the enclosed figure showing a schematic representation of an automotive auxiliary unit with an electronic protection unit according to the invention.

The figure shows an automotive auxiliary unit 10, for example a coolant pump or a lubricant pump of a motor vehicle. The automotive auxiliary unit 10 comprises a power supply terminal 12, an electronics unit 14 and an electronic protection unit 16 being electrically connected in series with the power supply terminal 12 and the electronics unit 14.

The electronic protection unit 16 comprises an inverse-polarity protection unit 18 with a semiconductor switch 20, an overcurrent protection unit 22 and a protection control unit 24.

In the present embodiment of the invention, the semiconductor switch 20 is a MOSFET. The input of the semiconductor switch 20 is electrically connected with the power supply terminal 12, the output of the semiconductor switch 20 is electrically connected with the electronics unit 14 and the control terminal of the semiconductor switch 20 is electrically connected with an inverse-polarity protection control unit 26. If the power supply terminal 12 is provided with a positive supply voltage, the semiconductor switch 20 is provided with a forward bias voltage so that the semiconductor switch 20 is highly conductive. If the power supply terminal 12 is provided with a negative supply voltage, the semiconductor switch 20 is provided with a inverse bias voltage so that the semiconductor switch 20 is substantially non-conductive.

The overcurrent protection unit 22 is electrically connected with the input of the semiconductor switch 20 and with the output of the semiconductor switch 20 to detect the voltage drop at the semiconductor switch 20. The overcurrent protection unit 22 is provided with an overcurrent protection evaluation unit 28 which evaluates the detected voltage drop to determine the present current level passing the semiconductor switch 20 and feeding the electronics unit 14.

The protection control unit 24 is connected with the inverse-polarity protection control unit 26 and with the overcurrent protection unit 22 via signal lines. In case of an overcurrent event, the overcurrent protection unit 22 provides an overcurrent signal to the protection control unit 24. The protection control unit 24 in turn provides an interrupt signal to the inverse-polarity protection control unit 26 which, as a result, switches off the semiconductor switch 20 to interrupt the electric connection between the power supply terminal 12 and the electronics unit 14.

Reference list automotive auxiliary unit

power supply terminal

electronics unit

electronic protection unit

inverse-polarity protection unit

semiconductor switch

overcurrent protection unit

protection control unit

inverse-polarity protection control unit overcurrent protection evaluation unit