METHOD FOR DETECTING A REVERSE CURRENT IN A SWITCHING STRUCTURE SUPPLYING AN INDUCTIVE LOAD
First Claim
1. A method for detecting a reverse current in a switching structure supplying power to an inductive load, the switching structure comprising at least one power switch and being designed to drive a current in the load in accordance with a duty cycle, the switching structure being linked firstly to an electric power source (Vps) and secondly to a ground (mas) in order to control the inductive load, the method comprising a control phase in which the current from the power source (Vps) supplies power to the inductive load in accordance with a given duty cycle and a freewheeling phase in which the induced current from the inductive load decreasing, the reverse current being liable to be created in the switching structure during a freewheeling phase following a high duty cycle in a previous control phase creating a counter-electromotive force (cemf) in the inductive load t, wherein the counter-electromotive force (cemf) at a given instant is approximated as being substantially proportional to an integration of the duty cycle (integ[Dut cycl]) as a function of time, the reverse current either being calculated as a function of an estimated counter-electromotive force (cemf) or a reversal of a current criterion being established.
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Abstract
A method for detecting a reverse current in a switching structure supplying power to an inductive load, having at least one switch and linked to an electric power source and to a ground for a control phase in which the current from the source supplies power to the load in accordance with a given duty cycle and a freewheeling phase in which the induced current from the load is decreasing, the reverse current being liable to be created during a freewheeling phase following a high duty cycle in a previous control phase creating a counter-electromotive force (cemf). The cemf is approximated proportionally to the integration of the duty cycle (integ[Dut cycl]) as a function of time (t), the reverse current either being calculated as a function of the estimated cemf or a reversal of the current criterion being established.
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Citations
10 Claims
- 1. A method for detecting a reverse current in a switching structure supplying power to an inductive load, the switching structure comprising at least one power switch and being designed to drive a current in the load in accordance with a duty cycle, the switching structure being linked firstly to an electric power source (Vps) and secondly to a ground (mas) in order to control the inductive load, the method comprising a control phase in which the current from the power source (Vps) supplies power to the inductive load in accordance with a given duty cycle and a freewheeling phase in which the induced current from the inductive load decreasing, the reverse current being liable to be created in the switching structure during a freewheeling phase following a high duty cycle in a previous control phase creating a counter-electromotive force (cemf) in the inductive load t, wherein the counter-electromotive force (cemf) at a given instant is approximated as being substantially proportional to an integration of the duty cycle (integ[Dut cycl]) as a function of time, the reverse current either being calculated as a function of an estimated counter-electromotive force (cemf) or a reversal of a current criterion being established.
Specification