US 6,188,184 B1 · Electronic ballast with reduced operating frequency after lamp ignition

Abstract

A ballast circuit for a compact fluorescent lamp includes a down-converter for operating the lamp with a DC current during stationary operation. First and second input terminals provide a DC supply voltage and first and second output terminals connect to the lamp. The down-converter has a first switch and a diode serially connected to the input terminals and an inductor coupled to the first switch and to one output terminal. A second switch is coupled to the output terminal. A control circuit operates the first switch at a high frequency. During the preheating and ignition phase, the down-converter is operated in the continuous mode and during stationary operation in the discontinuous mode by control of the switching frequency of the first switch.

Claims22

Dependent claims

A circuit arrangement for igniting and supplying a lamp with a DC current, comprising:

input terminals for connection to terminals of a DC power supply voltage source,
a DC-DC converter coupled to the input terminals and provided with
an inductive element,
a unidirectional element,
a first switching element,
a control circuit coupled to a control electrode of the first switching element for rendering the first switching element conducting and non-conducting at a frequency f,
output terminals for connecting the lamp, and
a first circuit which connects the output terminals during operation and comprises a second switching element rendered alternately conducting and non-conducting,
characterized in that the control circuit includes a circuit section I for decreasing the frequency f after ignition of the lamp.

6 more elements

A power supply circuit for operating a discharge lamp comprising:

first and second input terminals for connection to a source of DC supply voltage,
first and second output terminals for connection to the discharge lamp,
a DC/DC converter coupled to the input terminals and to the output terminals, the DC/DC converter comprising;
a first switching element and a diode coupled to the input terminals and an inductive element coupled to the first switching element and to a first one of the output terminals,
a control circuit coupled to a control electrode of the first switching element for alternately driving the first switching element into conduction and non-conduction at a frequency (f) high enough to operate the DC/DC converter in a continuous conduction mode before ignition of a connected discharge lamp,
a second switching element coupled to the output terminals, and
means for controlling the switching frequency of the first switching element so as to reduce the switching frequency (f) after ignition of the connected discharge lamp.

4 more elements

Dependencies are inferred from the claim text.

Electronic ballast with reduced operating frequency after lamp ignition

Life of this patent

Electronic ballast with reduced operating frequency after lamp ignition

Life of this patent

Abstract

Claims22