Temperature measurement method

#The present invention relates to temperature measurement using a sensor arranged in a high voltage environment. The sensor is, for example, located on a printed circuit board bearing power components. These power components form, for example, part of an inverter, as depicted in FIG. 1.

#In this FIG. 1, it can be seen that the sensor 100 which here is a negative temperature coefficient thermistor (still referred to as a CTN in English) is supplied by a voltage source 101 delivering a low voltage, e.g. of the order of 5 V. This sensor 100 is arranged on the same substrate as the switching cells 102 of the power inverter, each of these cells 102 being, for example, dimensioned for withstanding voltages of 430 V and currents of a maximum value of 350 A. Isolation between the high voltage circuit of the inverter and the low voltage circuit of the sensor 100 is ensured by means of a silicone gel covering the substrate. This isolation withstands voltages of the order of 1.5 kV. Nevertheless, the electrical isolation provided by the gel is not sufficient if a higher voltage is applied between the high voltage circuit and the low voltage circuit, which may occur in the event of an incident in the high voltage circuit.

#For protecting the sensor 100, it may then be necessary to add one or more additional isolating barriers, which may be costly in space and money.

#The invention may be better understood on reading the following description of a non-restrictive example of implementation thereof and on examining the accompanying drawing in which:

#FIG. 1 depicts a printed circuit board on which a temperature measurement is performed according to the prior art,

#FIG. 2 depicts a printed circuit board on which a temperature measurement is performed according to an example of implementation of the invention,

#FIG. 2 depicts an assembly 1 within which the method according to an example of embodiment of the invention may be implemented. This assembly 1 includes an inverter including a plurality of switching cells 2. Each switching cell 2 in the example considered is formed by the combination in parallel of a transistor, e.g. a field effect transistor, and a diode. Each transistor in the example described is a MOS transistor. The inverter depicted in FIG. 2 includes three branches each having two switching cells 2.

#Each cell 2 is, for example, configured for withstanding a current from the order of about ten amperes, in particular up to 350 A, and a voltage at its terminals of a few hundred volts, e.g. 430 V. In the example considered the inverter belongs to a high voltage circuit.

#As can be seen, a temperature sensor 4 is arranged at the level of the inverter, between two branches thereof. The temperature sensor 4 here is a negative temperature coefficient thermistor (CTN in English). This sensor 4 is supplied by a voltage source delivering a voltage of the order of 4.5 V to 5.5 V, i.e. a low voltage, through a measurement circuit 10 which will be described later. The circuit 10 supplies the sensor 4 with a low voltage isolatedly with respect to the high voltage of the inverter.