Koninklijke Philips Corporation N.v.

Lumileds Lighting U.s., LLC

Jozef Petrus Emanuel De Krijger

Marcel Johannes Maria Bucks

Engbert Bernard Gerard Nijhof

Armand Boudewijn Perduijn

Johannes Matheus Theodorus Lambertus Claessens

Jozef Alma Lodewijk Maria Ghijselen

Engbert Nijhof

Cong Khanh Pham

Johannes Mathcus Theodorus Lambertus Claessens

In a lamp driving circuit for operating a high intensity discharge lamp, an a commutation circuit comprises at least two switching devices. The switching devices are alternately switched active at a commutation frequency. The active switching device switches at a switching frequency. During an ignition mode, the switching frequency and the commutation frequency are substantially equal. A resulting commutation voltage is supplied to an inverter resonant circuit for generating a supply current. At a node of the inverter resonant circuit, a clamping circuit limits the generated voltage to a predetermined maximum voltage. The voltage at said node of the inverter resonant circuit is applied to an output resonant circuit. The output resonant circuit operates in the ignition mode as a resonator for generating a high ignition voltage; in a steady state operation mode, the output resonant circuit operates as a low-pass filter for reducing a high frequency current component in a lamp current.

Lamp driving circuit

A lamp driving circuit () for operating a discharge lamp has a series arrangement of a first and a second switching device (Q, Q) connecting supply voltage input terminals. An inverter resonant circuit () shunts one of the switching devices and has an inverter inductance (L), an inverter capacitance (C), and lamp connection terminals (O, O). A control circuit () controls the switching devices to generate a lamp current (I) commutating at a commutation frequency. During a first interval of a commutation period, the control circuit renders the first switching device alternately conducting during a first time period and non-conducting during a second time period at a high frequency being higher than the commutation frequency, and during a second interval of the commutation period, the control circuit renders the second switching device alternately conducting during a third time period and non-conducting during a fourth time period at a high frequency being higher than the commutation frequency. At the start of the first and second intervals of the commutation period, the first time period and the third time period, respectively, are extended for realizing an increased speed of commutation of the lamp current. Alternatively, at the end of the first and second intervals of the commutation period, the second time period and the fourth time period, respectively, are extended for realizing an increased speed of commutation of the lamp current.

A method for detecting defective operation of a discharge lamp includes determining the lamp impedance and establishing that the lamp is operating in an incandescent mode if it is found that the lamp has a positive impedance.

Method and system for operating a discharge lamp such as to detect defective operation of the lamp

In a lighting arrangement comprising a LED array and a DC-DC-converter for supplying the LED array, the DC-DC-converter is an up-converter and the LED array is coupled between an input terminal and an output terminal. The up-converter generates a very low voltage over the LED array without making use of a transformer.

Lighting arrangement

In an up-converter feed forward control of the output current is effected by rendering the conduction time of the switching element proportional to V/V. This control is fast and avoids interference and loss of efficiency.

Circuit arrangement

In a circuit arrangement for driving a LED array comprising red, green and blue LEDs, a control loop is added for limiting the duty cycles of the control signals for driving the red, green and blue LEDs. In case one of the duty cycles reaches the limit value, the reference signals for the red, green and blue light are decreased with the same relative amount. The color point of the light is thereby maintained, even when the efficiency of part of the LEDs decreases.

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Eindhoven, Netherlands

Jozef Petrus Emanuel De Krijger