Current measurement for an electric heater
AssigneeValeo Systemes Thermiques
InventorsBertrand Puzenat, Laetitia Gestas
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Abstract
The invention relates to a method for measuring a current or voltage output quantity of a switched-mode power supply circuit (H), referred to as a chopper circuit, of period T and of cyclic ratio α, belonging to the interval]0; 1[, such that, at each period, the supply current is non-zero during an “ON” phase of duration αT, and zero during an “OFF” phase of duration (1−α)T. The measurement method includes the following steps: measuring the value Gon of an image of the output quantity during an “ON” phase; measuring the value Goff of an image of the output quantity during an “OFF” phase; calculating the difference ΔG=Gon−Goff; and using the difference ΔG for evaluating the output quantity.
Claims16
A method for measuring a current or voltage output quantity of a switched-mode power supply circuit, called chopper circuit, of period T and of duty cycle α, belonging to the interval]0;
- 1[, such that, at each period, the power supply current is non-zero during an on phase of duration αT and zero during an off phase of duration (1−α)T, wherein the measurement method comprises the following steps:
- measuring the value Gon of the current or voltage output quantity during an on phase;
- measuring the value Goff of the current or voltage output quantity during an off phase;
- calculating the difference ΔG=Gon−Goff;
- and
- using the difference ΔG to evaluate the current or voltage output quantity.
A device for measuring an output quantity of a switched-mode power supply circuit, called chopper circuit, of period T and of duty cycle α, belonging to the interval]0;
- 1[, such that, at each period, the power supply current is normally-non-zero during an on phase of duration αT and zero during an off phase of duration (1−α)T, the device comprising:
- a circuit for amplifying a representative voltage of the quantity to be measured;
- and
- a unit for measuring the amplified voltage at the output of the amplification circuit, which is designed to:
- measure the value Gon of the amplified voltage during an on phase;
- measure the Goff value of the amplified voltage during an off phase,
- calculate the difference ΔG=Gon−Goff, and
- use the value of the difference ΔG to evaluate the output quantity.
Dependencies are inferred from the claim text.