Method and device for protecting an electrical converter circuit against overload

Claim 2

Method for protecting against overload an electrical converter circuit supplied with a pulsed current having a duty factor, comprising the steps of: calculating a mean value of said pulsed current; producing a first voltage having a value proportional to said mean value; producing a second voltage having a value proportional to a maximum wanted output power of the converter and to said duty factor; comparing the values of said first and second voltages; and limiting an output power of the converter if the first voltage becomes greater than the second.

Claim 3

Method according to claim 1 wherein the duty factor of the pulsed current is varied to maintain the converter output voltage constant.

Claim 4

Method for protecting against overload an electrical converter circuit of the forward conversion type having an output voltage and supplied with a pulsed current having a duty factor and comprising a transformer having a transformer ratio, said method comprising the steps of: calculating a mean value of said pulsed current; producing a first voltage having a value proportional to said mean value; producing a second voltage having a value representative of a maximum wanted output power multiplied by the duty factor and by said transformer ratio and divided by a value of a converter output voltage and by a converter efficiency; comparing the values of said first and second voltages; and limiting of an output power of the converter if the first voltage becomes greater than the second.

Claim 5

Method for protecting against overload an electrical converter circuit of the forward conversion type having an output voltage and supplied with a pulsed current having a duty factor and comprising a transformer having a transformer ratio, said method comprising the steps of: calculating a mean value of said pulsed current; producing a first voltage having a value proportional to said mean value; producing a second voltage having a value representative of a maximum wanted output power multiplied by the duty factor and by said transformer ratio and divided by a value of a converter output voltage and by a converter efficiency; comparing the values of said first and second voltages; and limiting of an output power of the converter if the first voltage becomes greater than the second.

Claim 6

Method for protecting against overload an electrical converter circuit of the flyback type comprising a transformer having a transformer ratio and an inductor that is never demagnetized, said converter having an output voltage and being supplied by a primary source with a pulsed current having a duty factor, said method comprising the step of: calculating a mean value of said pulsed current; producing a first voltage having a value proportional to said mean value multiplied by a duty factor of interruptions of said current; producing a second voltage representative of a value of a maximum wanted output power multiplied by the transformer ratio and by the duty factor and divided by a value of the converter output voltage and by a converter efficiency; comparing the values of said first and second voltages; and limiting the output power of the converter if the first voltage becomes greater than the second.

Claim 7

Method for protecting against overload an electrical converter circuit of the flyback type comprising a transformer having a transformer ratio and an inductor that is never demagnetized, said converter having an output voltage and being supplied by a primary source with a pulsed current having a duty factor, said method comprising the step of: calculating a mean value of said pulsed current; producing a first voltage having a value proportional to said mean value multiplied by a duty factor of interruptions of said current; producing a second voltage representative of a value of a maximum wanted output power multiplied by the transformer ratio and by the duty factor and divided by a value of the converter output voltage and by a converter efficiency; comparing the values of said first and second voltages; and limiting the output power of the converter if the first voltage becomes greater than the second.

Claim 8

Method for protecting against overload an electrical converter circuit of the flyback type comprising a transformer having a transformer ratio and a periodically demagnetized inductor, said converter being supplied with a pulsed current having a duty factor, said method comprising the step of: calculating a mean value of said pulsed current; producing a first voltage having a value representative of: IPm×(toff-tm)/T in which IPm is said mean value, toff represents a value of a time interval between the pulses of the pulsed current, tm represents a value of a time period during which a voltage across the inductor is cancelled out and T represents a value of a period of the pulsed current; producing a second voltage representative of a maximum wanted output power multiplied by the transformer ratio and by the duty factor and divided by a value of a converter output voltage and by a converter efficiency; comparing the values of said first and second voltages; and limiting the output power of the converter if the first voltage becomes greater than the second.

Claim 9

Method for protecting against overload an electrical converter circuit of the flyback type comprising a transformer having a transformer ratio and a periodically demagnetized inductor, said converter being supplied with a pulsed current having a duty factor, said method comprising the step of: calculating a mean value of said pulsed current; producing a first voltage having a value representative of: IPm×(toff-tm)/T in which IPm is said mean value, toff represents a value of a time interval between the pulses of the pulsed current, tm represents a value of a time period during which a voltage across the inductor is cancelled out and T represents a value of a period of the pulsed current; producing a second voltage representative of a maximum wanted output power multiplied by the transformer ratio and by the duty factor and divided by a value of a converter output voltage and by a converter efficiency; comparing the values of said first and second voltages; and limiting the output power of the converter if the first voltage becomes greater than the second.

Claim 10

Method according to claim 1 wherein the multiplication of a value of a voltage by a duty factor is provided by alternately routing said voltage and a reference potential to an RC filter at the timing rate of the pulsed current pulses during time lapses corresponding to said duty factor.

Claim 11

Device for protecting against overloads an electrical converter circuit supplied with a pulsed current by a primary source, said device comprising: a first filter to which is applied a voltage representing the pulsed current applied to the converter, said filter being designed to supply an output voltage representing the average value of said current; a first integrator whose input is adapted to be connected alternately by a first switch to the output of the first filter and to a reference potential, said first integrator supplying at its output a voltage representing the product of said output voltage and a duty factor; a second integrator whose input is adapted to be alternately connected by a second switch to a reference voltage source and to a reference potential, said second integrator supplying at its output a voltage representing the product of the reference voltage and a second duty factor; an a comparator having two inputs connected to respective outputs of the two integrators, said comparator supplying a fault signal adapted to control limitation of the output power of the converter if the voltage supplied by the first integrator reaches or exceeds the voltage supplied by the second integrator.

Claim 12

Device for protecting against overloads an electrical converter circuit supplied with a pulsed current by a primary source, said device comprising: a first filter to which is applied a voltage representing the pulsed current applied to the converter, said filter being designed to supply an output voltage representing the average value of said current; a first integrator whose input is adapted to be connected alternately by a first switch to the output of the first filter and to a reference potential, said first integrator supplying at its output a voltage representing the product of said output voltage and a duty factor; a second integrator whose input is adapted to be alternately connected by a second switch to a reference voltage source and to a reference potential, said second integrator supplying at its output a voltage representing the product of the reference voltage and a second duty factor; an a comparator having two inputs connected to respective outputs of the two integrators, said comparator supplying a fault signal adapted to control limitation of the output power of the converter if the voltage supplied by the first integrator reaches or exceeds the voltage supplied by the second integrator.

Claim 13

Device according to claim 7 for use in a forward type converter wherein said first switch is controlled so as to apply continuously to the input of the first integrator the voltage representing the mean pulsed current and the second switch is controlled in such a way as to transmit the reference voltage to the second integrator during time periods representing pulses of the pulsed current and a null voltage during time periods representing gaps between the pulses of said pulsed current.

Claim 14

Device according to claim 7 for use in a flyback partial demagnetization type converter wherein the first switch is controlled in such a way as to apply to the input of the first integrator the voltage representing the mean pulsed primary current during time periods representing gaps between the pulses of the pulsed current and a null voltage during time periods representing said pulses and the second switch is controlled in such a way as to apply the reference voltage to the input of the second integrator during the time periods representing said pulses and a null voltage during the time periods representing the gaps between said pulses.

Claim 15

Device according to claim 7 for use in a flyback full demagnetization type converter wherein the first switch is controlled in such a way as to apply to the input of the first integrator the voltage representing the mean pulsed primary current during time intervals of the period of the pulsed current equal to the interval between the pulses of the pulsed current less the time period during which the voltage across the converter inductor is cancelled out and the second switch is controlled in such a way as to apply the reference voltage to the second integrator during time periods representing said pulses and a null voltage during time periods representing the gaps between said pulses.

Claim 16

Device according to claim 7 wherein said first filter comprises a circuit comprising a resistor in series with a grounded capacitor and the voltage at the common point of said resistor and said capacitor is applied to the input of a variable gain operational amplifier.

Claim 17

Device according to claim 7 wherein said first switch is controlled by a signal at the collector of a transistor whose base is biased by a voltage divider bridge connected in series in a circuit comprising a secondary winding of the inductor and a diode.

Claim 18

Method for protecting against overload an electrical converter circuit supplied with a pulsed current having a duty factor, comprising the steps of: calculating a mean value of said pulsed current; producing a first voltage having a value proportional to said mean value; producing a second voltage having a value proportional to a maximum wanted output power of the converter and to a function of said duty factor; comparing the values of said first and second voltages; and limiting an output power of the converter if the first voltage becomes greater than the second.

Claim 19

Method for protecting against overload an electrical converter circuit supplied with a pulsed current having a duty factor, comprising the steps of: calculating a mean value of said pulsed current; producing a first voltage having a value proportional to said mean value; producing a second voltage having a value proportional to a maximum wanted output power of the converter and to a function of said duty factor; comparing the values of said first and second voltages; and limiting an output power of the converter if the first voltage becomes greater than the second.