Current surge limiting circuit
AssigneeSTMicroelectronics S.r.l.
InventorsLuc Wuidart, Michel Bardouillet
Life of this patent
Estimating the term…
Abstract
The present invention relates to a surge current limiting circuit of a filament lamp, meant to be connected in series between the filament and a switch that supplies an a.c. voltage, including at least one controllable active element, for limiting the current to a predetermined threshold value.
Claims25
A circuit for limiting the surge current of a filament lamp, connected in series between the filament and a switch that can supply an a.c. voltage, and including at least one controllable active element, for limiting the current to a predetermined threshold value, and a biasing resistor connected between one of the power terminals of this element and its control terminal;
- wherein the threshold value is set by a resistor that is used to measure the current through the lamp;
- including at least one limiting element in series with the measurement resistor, a control terminal of the limiting element being connected to a control means for detecting the voltage across the measurement resistor;
- and
- wherein the means is formed of a bipolar transistor, between a base and an emitter of which is connected the measurement resistor, the limiting element being controlled in linear mode.
A circuit for limiting the surge current of a filament lamp, connected in series between the filament and a switch that can supply an a.c. voltage, and including at least one controllable active element, for limiting the current to a predetermined threshold value, and a biasing resistor connected between one of the power terminals of this element and its control terminal;
- wherein the threshold value is set by a measurement resistor that is used to measure the current through the lamp;
- including at least one limiting element in series with the measurement resistor, a control terminal of the limiting element being connected to a control means for detecting the voltage across the measurement resistor;
- and
- wherein the means is formed of a comparator that compares the voltage across the measurement resistor with respect to a predetermined reference value, the limiting element being controlled in switched mode.
A circuit for limiting the surge current of a filament lamp, connected in series between the filament and a switch that can supply an a.c. voltage, and including at least one controllable active element, for limiting the current to a predetermined threshold value, and a biasing resistor connected between one of the power terminals of this element and its control terminal;
- including two limiting elements, to limit the current in the lamp to the predetermined threshold value, each element being connected as a unidirectional limiter;
- and
- including two field effect MOS transistors, connected in series between the switch and the filament, a measurement resistor being interposed between the two transistors and the current path including, upon each halfwave of the supply voltage, a parasitic diode of one of the two field effect transistors.
A circuit for limiting the current to a filament lamp and in which the circuit is coupled in series between the filament lamp and a switch that supplies an a.c. voltage at a single a.c. voltage terminal, said circuit comprising:
- at least one controllable active element having a pair of main terminals and a control terminal;
- said main terminals of said active element disposed between the filament lamp and the switch;
- and at least one biasing resistor connected between one of the main terminals of the active element and the control terminal of the active element;
- said active element and biasing resistor for limiting the current to the filament lamp to a predetermined threshold value;
- further including a measuring resistor to set said threshold value;
- wherein said measuring resistor is connected in series with one of said main terminals of said active element.
Dependencies are inferred from the claim text.