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US 6,310,790 B1Granted
High frequency DC-DC down converter with power feedback for improved power factor
AssigneeU.S. Philips Corporation
InventorsMachiel A. M. Hendrix, Darko Antic
Life of this patent
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Abstract
In a downconverter for supplying a DC current to a lamp, power feedback is achieved by adding a high frequency-operated switch and a capacitor to the topology. The power factor is improved thereby.
Claims25
A circuit arrangement for supplying a direct current or a low-frequency commutated direct current to a lamp, comprising:
- supply input terminals for connection to the poles of a supply voltage source supplying an alternating current,
- rectifier means coupled to the supply input terminals to rectify the alternating current and provided with a first output terminal and a second output terminal,
- a buffer capacitance coupled to the output terminals of the rectifier means,
- a DC-DC converter of the downconverter type coupled to the buffer capacitance and provided with
- a first chain coupled to the output terminals and comprises a series-arrangement of a first circuit element and a first unidirectional element,
- a first control circuit coupled to the first circuit element to render the first circuit element high-frequency conducting and non-conducting at a frequency f1,
- a second chain coupled across the first unidirectional element and comprises a series arrangement of a first inductive element and a first capacitance, characterized in that the circuit arrangement is also provided with
- a third chain which comprises a second circuit element and which shunts the first unidirectional element,
- a second control circuit which is coupled to a control electrode of the second circuit element and which serves to render the second circuit element high-frequency conducting and non-conducting at a frequency f1,
- a fourth chain which shunts the first circuit element and which comprises a series arrangement of a second capacitance and a second unidirectional element, a junction point of the second capacitance and a first terminal of the second unidirectional element being coupled to the first output terminal of the rectifier means wherein a second terminal of the second unidirectional element is coupled to the first chain, and the circuit arrangement includes
- a lamp connection terminal connected so that a direct current is made to flow through a lamp when connected to said lamp connection terminal.
8 more elements
A circuit for supplying a direct current to a discharge lamp comprising:
- input terminals for connection to a low frequency AC supply voltage source,
- rectifier means coupled to the input terminals and having first and second DC output terminals,
- a buffer capacitance coupled to the first and second DC output terminals,
- a DC-DC down converter coupled to the first and second DC output terminals and the buffer capacitance, the DC-DC down converter comprising;
- a first series circuit coupled to the first and second DC output terminals and which includes first and second controlled switching elements,
- a second series circuit coupled to the first and second DC output terminals and which includes the first controlled switching element and a first unidirectional element,
- a third series circuit coupled across the first unidirectional element and comprises a first inductive element and a first capacitance,
- a fourth series circuit which shunts the first controlled switching element and which comprises a second capacitance and a second unidirectional element and with a circuit point between the second capacitance and a first terminal of the second unidirectional element coupled to the first DC output terminal wherein a second terminal of the second undirectional element is coupled to the first chain, and
- control circuit means coupled to respective control electrodes of the first and second controlled switching elements for switching same alternately on and off at a high frequency f1 so that a direct current will flow through a lamp when connected to the supply circuit.
6 more elements
Dependencies are inferred from the claim text.