Lamp with integral voltage converter having phase-controlled dimming circuit containing a voltage controlled resistor
View Patent ↗An incandescent lamp includes a lamp voltage conversion circuit within the lamp and connected to a lamp terminal, where the voltage conversion circuit converts a first line voltage at the lamp terminal to a second RMS load voltage usable by a light emitting element of the lamp. The voltage conversion circuit includes a triac phase-controlled dimming circuit, which in turn includes a voltage controlled resistor (VCR) that varies a resistance in the phase-controlled dimming circuit as the first voltage varies so as to maintain the second voltage substantially constant. The VCR may be a junction field effect transistor VCR. The voltage conversion circuit may be an integrated circuit that is in the lamp base and connected between the lamp terminal and the light emitting element.
1. A lamp comprising:
a light emitting element;
a lamp terminal adapted for connecting to a line voltage; and
a lamp voltage conversion circuit within the lamp and connected in series between the light emitting element and the lamp terminal, the voltage conversion circuit including a phase-controlled dimming circuit having a triac and a voltage controlled resistor connected to said triac, the voltage controller resistor having a resistance that varies in response to variation of the line voltage at the lamp terminal, wherein variation of the line voltage occurs when the root mean square (RMS) magnitude of the line voltage over a first period of time differs from the RMS magnitude of the line voltage over a second period of time, such that the variation of the resistance of the voltage controlled resistor in response to the variation in line voltage results in the phase-controlled dimming circuit providing, to the light emitting element, a time-varying voltage having a substantially constant magnitude.
2. The lamp of claim 1 , wherein the phase-controlled dimming circuit further includes a capacitor and a diac, wherein the triac is triggered by the diac.
3. The lamp of claim 1 , further comprising a base and a light-transmitting envelope, and wherein the voltage conversion circuit is within the base and the light-transmitting envelope houses the light emitting element.
4. The lamp of claim 1 , wherein the voltage controlled resistor (VCR) is a junction field effect transistor VCR.
5. The lamp of claim 1 , wherein the voltage conversion circuit is an integrated circuit.
6. The lamp of claim 5 , further comprising a base and a light-transmitting envelope, and wherein the integrated circuit is within the base and the light-transmitting envelope houses the light emitting element.
7. The lamp of claim 1 , wherein the voltage controlled resistor is a two-terminal device.
8. The lamp of claim 1 , wherein variation of the line voltage occurs when the lamp is moved from a first location having a first line voltage to a second location having a second line voltage, wherein the root mean square (RMS) magnitude of the first line voltage is different from the RMS magnitude of the second line voltage.
9. The lamp of claim 1 , wherein the resistance of the voltage controlled resistor determines when the triac is triggered.
10. The lamp of claim 9 , wherein the RMS magnitude of the line voltage over the second period of time is greater than the RMS magnitude of the line voltage over the first period of time, and in response, the voltage controlled resistor increases resistance to delay triggering the triac.
11. The lamp of claim 9 , wherein the RMS magnitude of the line voltage over the second period of time is less than the RMS magnitude of the line voltage over the first period of time, and in response, the voltage controlled resistor decreases resistance to advance triggering the triac.
12. The lamp of claim 1 , wherein the light emitting element is an incandescent filament, and wherein the lamp voltage conversion circuit provides, to the incandescent filament, a time-varying voltage having a substantially constant RMS magnitude, wherein the time-varying voltage is a lamp operating voltage lower than the line voltage.