Abstract: An earthing of an electronic circuit is disclosed in a device belonging to a low-voltage system with, for example, a maximum AC voltage of 1000 V or a maximum DC voltage of 1500 V in which the device is at the main voltage potential or is connected to the main voltage through a high-impedance coupling. An overvoltage protection of the interface between such an electronic circuit and a SELV (Safety Extra Low Voltage) circuit is also disclosed. The neutral point (COM) of the electronic device is coupled to protective earth (PE) through at least one breakdown-based overvoltage protector. The rated breakdown voltage of the overvoltage protector is higher than the voltage present across it in normal operating conditions but lower than the minimum dielectric strength of the component forming the interface between the electronic device and the SELV circuit.

Abstract: A circuit and method is disclosed for measuring the resistance of a resistive sensor, such as a PTC or NTC temperature sensor used for monitoring the temperature of the windings of an electric motor. The measurement circuit is based on an electronic circuit in which conductors from a sensor located in the object to be monitored are connected to an amplifier circuit in a feedback configuration that reduces the DC level supplied to the voltage divider when the sensor resistance increases. The measured signal is amplified and, using a comparator to compare it with the output voltage of a sawtooth generator, a continuous PWM (Pulse Width Modulation) signal is generated and transmitted in digital format to a SELV electronic circuit, for example through an opto-isolator. The essentially logarithmic signal amplification makes it possible to reliably distinguish between a short circuit in the sensor circuit and low values of sensor resistance.

Abstract: A circuit and method is disclosed for measuring the resistance of a resistive sensor, such as a PTC or NTC temperature sensor used for monitoring the temperature of the windings of an electric motor. The measurement circuit is based on an electronic circuit in which conductors from a sensor located in the object to be monitored are connected to an amplifier circuit in a feedback configuration that reduces the DC level supplied to the voltage divider when the sensor resistance increases. The measured signal is amplified and, using a comparator to compare it with the output voltage of a sawtooth generator, a continuous PWM (Pulse Width Modulation) signal is generated and transmitted in digital format to a SELV electronic circuit, for example through an opto-isolator. The essentially logarithmic signal amplification makes it possible to reliably distinguish between a short circuit in the sensor circuit and low values of sensor resistance.

Abstract: An earthing of an electronic circuit is disclosed in a device belonging to a low-voltage system with, for example, a maximum AC voltage of 1000 V or a maximum DC voltage of 1500 V in which the device is at the main voltage potential or is connected to the main voltage through a high-impedance coupling. An overvoltage protection of the interface between such an electronic circuit and a SELV (Safety Extra Low Voltage) circuit is also disclosed. The neutral point (COM) of the electronic device is coupled to protective earth (PE) through at least one breakdown-based overvoltage protector. The rated breakdown voltage of the overvoltage protector is higher than the voltage present across it in normal operating conditions but lower than the minimum dielectric strength of the component forming the interface between the electronic device and the SELV circuit.