Abstract: 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.

Abstract: A lamp driving circuit (10) for operating a discharge lamp has a series arrangement of a first and a second switching device (Q1, Q2) connecting supply voltage input terminals. An inverter resonant circuit (20, 30) shunts one of the switching devices and has an inverter inductance (L1), an inverter capacitance (C1), and lamp connection terminals (O1, O2). A control circuit (40) controls the switching devices to generate a lamp current (IL) 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.

Abstract: 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.

Abstract: In an application of a gas discharge lamp (La) arranged at a relatively large distance from its driving lamp driver circuit, parasitic capacitances (CGR,1, CGR,2) between the wiring (W1, W2) and ground may result in a current flowing to other parts of the lamp driver circuit, which may result in incorrect operation of the lamp driver circuit. In particular, if the gas discharge lamp is ignited using a resonant circuit for generating a relatively high ignition voltage such incorrect operation may result. In accordance with the present invention, a first alternating voltage is generated at a first lamp terminal (O1) and a second alternating voltage is generated at a second lamp terminal (O2), such that the voltage across the lamp terminals is equal to the sum of the first and the second alternating voltages. Thereto, a resonant inductance of the resonant circuit is embodied as a first and a second inductor (L1a, L1b), each coupled to a respective lamp terminal of the gas discharge lamp.

Abstract: A lamp driving circuit (110) for driving a gas discharge lamp (11) is described, comprising current generating means (M1, M2, D1, D2, L, C, C1, C2) for generating a lamp current in discontinuous mode or critical discontinuous mode, and a controller (12) for controlling the operation of the current generating means. In an embodiment, the current generating means have HBCF topology. A zero-crossings detector (120) detects zero-crossings of the lamp current, and generates a detection pulse for each detected zero-crossing. A signal processor (130) monitors the detection pulses from the zero-crossings detector (120), and generates a lamp current inhibit signal if the detection pulses are absent during at least a predetermined time interval. The controller, in response to the lamp current inhibit signal, switches off the lamp current generating means.

Abstract: A method is described for detecting defective operation of a discharge lamp (7). The method comprises the steps of 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. The lamp current is varied and the lamp voltage variation in response to the lamp current variation is analyzed to determine the lamp impedance. In a specific embodiment, the lamp current is set at a first magnitude (I(tM1)) at a first measuring moment (tM1) and a first lamp voltage (V(tM1)) occurring at said first measuring moment is measured, while at a second measuring moment (tM2) the lamp current is set at a second magnitude (I(tM2)) different from the first magnitude and a second lamp voltage (V(tM2)) occurring at said second measuring moment is measured, and the relationship between said two lamp voltages is analyzed.

Abstract: 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.

Abstract: 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.

Abstract: In an up-converter feed forward control of the output current is effected by rendering the conduction time of the switching element proportional to Vout/Vin2. This control is fast and avoids interference and loss of efficiency.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: In an up-converter feed forward control of the output current is effected by rendering the conduction time of the switching element proportional to Vout/Vin2. This control is fast and avoids interference and loss of efficiency.