Control for electrical heating circuit, in particular for motor vehicle

A device for controlling an electric heating circuit comprising a positive number N of heating elements connected in parallel, the control device comprising:

• a positive number N of electronic switches, each connected in series with one out of the positive number N of heating elements, the positive number N of electronic switches:
• correspond to the positive number N of heating elements, and
• switch from an open position to a closed position or from a closed position to an open position based on the positive number P of comparison signals;
• a connector/receiver that:
• receives a power setpoint in the form of a pulse width modulation (PWM) control signal of variable duty cycle as a function of the power, and
• transfers an equivalent PWM signal with the variable duty cycle and a power amplitude, the equivalent PWM signal and the power amplitude being based on a reference voltage supplied by a pull up resistor;
• a low-pass RC filter, with a time constant greater than a period of the PWM control signal, that obtains an average value of the PWM control signal received directly from the connector/receiver to the low-pass RC filter;
• a positive number P of comparators that, when P is less than or equal to N:
• compare the obtained average value with a corresponding positive number P of threshold values, and
• generate a positive number P of comparison signals based on each of the positive number P of comparisons performed by the positive number P of comparators;
• and
• wherein the device processes the PWM control signal, processes the equivalent PWM signal, and controls the electric heating circuit without using a microcontroller.

A method for controlling an electric heating circuit comprising a plurality of heating elements connected in parallel, each heating element connected in series with an associated electronic switch, the method comprising:

• receiving, by a connector/receiver, a pulse width modulation (PWM) control signal of variable duty cycle;
• transferring, by the connector/receiver, an equivalent PWM signal with the variable duty cycle, an amplitude of the variable duty cycle being based on a reference voltage supplied by a pull up resistor;
• obtaining, by a low-pass RC filter, an average value of the received PWM control signal, the PWM control signal being transferred directly from the connector/receiver to the low-pass RC filter;
• comparing, by a plurality of comparators, the average value of the received PWM control signal to a corresponding threshold value, the corresponding threshold value being unique to each comparator out of the plurality of comparators;
• generating a plurality of comparison signals based on each of the comparisons performed by the plurality of comparators;
• and
• switching, using the plurality of comparison signals, a plurality of electronic switches from an open position to a closed position or from a closed position to an open position, each electronic switch out of the plurality of electronic switches corresponding to each heating element out of the plurality of heating elements,
• wherein:
• processing the PWM control signal, processing the equivalent PWM signal, and controlling the electric heating circuit is performed without using a microcontroller.