Patent ID: 6392366
Filing Date: 2002-05-21
Classification: H05B,Y10S

Abstract:
A ballast circuit for an electrodeless lamp designed to use a phase dimmer signal to control output of the electrodeless lamp, the dimming ballast circuit comprising:(a) a rectifier circuit for rectifying an input voltage from a phase dimmer source having a dimmer voltage node and a dimmer reference node, including: (i) a plurality of rectifier diodes connected in a bridge rectifier arrangement having a pair of input nodes connected to said dimmer voltage node and said dimmer reference node as input; (ii) an output d.c. bus node; and (iii) an output ballast reference node; (b) a converter control circuit coupled to said rectifier circuit for inducing an r.f. a.c. load current, said converter comprising: (i) first and second converter switches serially connected between said bus node and said reference node, being connected together at a common node through which said r.f. a.c. load current flows, and each switch having a control node connected to a common control node, the voltage between said control node and said common node determining the conduction state of each of said switches; (ii) a first resistor connected between said bus node and said control node; (iii) a second resistor connected between said reference node and said control node; and (iv) a driving inductor connected at one end to said common node and operatively connected at the remaining end to said control node; and (c) a load circuit including: (i) a resonant inductor connected at one end to said common node, said resonant inductor being mutually coupled to said driving inductor for sensing a voltage across said resonant inductor; (ii) an r.f. inductor connected at one end to the remaining end of said resonant inductor for generating an r.f. field for powering said electrodeless lamp; (iii) a resonant capacitor serially connected to the remaining end of said r.f. inductor, said resonant capacitor connected at the remaining end to an intermediate node, wherein said resonant capacitor is a non-electrolytic capacitor; and (iv) first and second d.c. blocking capacitors connected between said bus node and said reference node, said blocking capacitors being joined with said resonant capacitor at said intermediate node, wherein said blocking capacitors are non-electrolytic capacitors.