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AssigneeRobert Bosch GmbH
InventorsThomas Mohr, Norbert Knab, Albert Eisele, Juergen Rapp
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A method and a circuit arrangement suitable for performing the method are provided for protecting an electric motor (10) and/or its trigger circuit (12) against overload in the emergency-operation mode. The method of the invention and the associated circuit arrangement serve in particular to protect a motor vehicle direct-current fan motor operated by means of pulse width modulation, in which the trigger circuit is designed as an emergency-operation controller, with a microcontroller (16) preceding the motor end stage (22) and with a comparator assembly (14) for detecting overvoltages. The provisions according to the invention assure overload protection at elevated battery voltage and at the same time when the emergency-operation controller is activated in response to malfunctions in the normal triggering (12) of the electric motor (10). To that end, at least one overvoltage threshold (Us1, Us2) is defined; when it is exceeded, the power supplied to the motor is reduced or switched off.
A method for protecting an electric motor (10) and/or its trigger circuit (12) against overload, particularly for protecting a direct-current fan motor of a motor vehicle, wherein the electric motor is assigned a motor end stage for pulse-width modulated control (PWM) of the power supplied and is also assigned a controller for limiting the motor power on the occurrence of an elevated supply voltage, characterized in that the overload protection becomes operative in emergency operation of the electric motor (10), by activation of an emergency-operation controller (14, 16) upon the occurrence of a malfunction (28, 30) in the triggering (8) of the motor end stage, and the electric motor (10) is supplied with a defined emergency-operation power, which below a first overvoltage threshold (Us1) of the supply voltage has a specified value or course and is reduced or switched off if one or more overvoltage thresholds (Us1, Us2) are exceeded.
The method of one of the foregoing claims, characterized in that the electric motor (10) is switched off when the second overvoltage threshold (Us2) is reached.
The method of one of the foregoing claims for use in a 12-volt on-board electrical system of a motor vehicle, characterized in that the first overvoltage threshold (Us1) is fixed at a value of 14 V.
The method of one of the foregoing claims for use in a 12-volt on-board electrical system of a motor vehicle, characterized in that the second overvoltage threshold (Us2) is fixed at a value of 16 V.
The method of one of the foregoing claims, characterized in that the power of the electric motor (10) in the emergency-operation mode is regulated by means of a voltage monitoring circuit with a comparator assembly (14), to which a reference voltage (Uref) corresponding to the battery voltage (Ubat) is supplied as a reference value for the overvoltage thresholds (Us1, Us2).
A circuit arrangement for protecting an electric motor and/or its trigger circuit (12) against overload, in particular for protecting a direct-current fan motor of a motor vehicle, having a motor end stage for pulse-width modulated control (PWM) of the power supplied to the electric motor, and having a controller for limiting the motor power on the occurrence of an elevated supply voltage, in particular for performing the method of one of the foregoing claims, characterized in that for the overload protection in the emergency-operation mode of the electric motor (10), its trigger circuit (12) is embodied as an emergency-operation controller (14, 16, 22), which in addition to a PWM set-point value transducer (18) and the motor end stage (22) has a microcontroller (16), which precedes the motor end stage and which upon an interruption or a defective input of the set-point value signal of the pulse width modulation (PWMsol1) and/or of the switched supply voltage (U15) supplies a control voltage (PWM) to the motor end stage (22), corresponding to the specification of at least one overvoltage threshold (Us1, Us2) to the microcontroller.
Dependencies are inferred from the claim text.