Abstract:
A protection circuit for electronic ballasts which use charge pump power factor correction includes a switch (160) with an overvoltage sensor (150), a resistor (170) and a diode (70). In the event of a fault condition, the switch (160) disables the charge pump power factor correction, while the resistor (170) and diode (70) prevent the switch (160) dissipating unduly large amounts of energy.
Abstract:
A circuit with a transistor common to both the inverter (113) and the boost converter (118) powers a gas discharge lamp (144). In a half-bridge inverter, a boost inductor (108) is coupled between the rectifier (104) and the junction (112) between two switching circuits (114, 116).
Abstract:
An integrated EMI/RFI filter magnetic (200) has differential and common mode inductors wound about an I-core (210). The I-core is juxtaposed with an E-core (202), with the end surfaces (222, 224, 226) of the E-core legs (204, 206, 208) facing the I-core. The magnetic has a substantially closed magnetic path of the differential inductors (300, 302) and the common mode inductors (304, 306).
Abstract:
A power supply circuit (100) for use in driving fluorescent lamps (102, 104, 106) has a current mode control voltage boost IC (144) which produces a boosted voltage and has a power control input (pin 3) and a frequency control input (pin 4). The lamps are driven by a self oscillating inverter (178, 180, 196, 198) which is powered from the voltage boost IC and which operates at a frequency independent therefrom. In order to dim the lamps a D.C. bias voltage is applied to the power control input. At the same time a commensurate D.C. bias voltage is applied to the frequency control input so as to provide power factor correction in dependence on the power produced by the voltage boost IC. The circuit thus provides a substantially constant, optimum power factor at both full and dimmed light levels.
Abstract:
A control circuit (C) for controlling fluorescent lamps (102, 104 and 106) from a switch (S) having 'open' and 'closed' positions. The circuit senses whether the switch is (i) open, (ii) closed within less than approximately 0.5 seconds of last being opened, or (iii) closed for the first time or after a time greater than approximately 0.5 seconds after last being opened, and produces one of three output signals respectively dependent thereon. The control circuit uses only a conventional two-position switch and conventional wiring and avoids the need for additional switches and additional wiring.
Abstract:
An arrangement for securing a power transistor (4, 6, 8) or like component which is inserted into a printed circuit board (2) in a vertically downward direction. The printed circuit board is housed in a housing (20, 60) whose lower part (20) has upstanding walls (24, 26) with pairs of vertical slots (4A and 4B, 6A and 6B, 8A and 8B). Spring clips (52) are inserted vertically downwardly so that their legs (52A, 52B) engage in the slots and their center portions (54) urge the transistors toward the upstanding walls so that the housing acts as a heat sink for the transistors, obviating the need for additional components. Also, since all insertion is performed vertically from above, assembly can be performed straightforwardly by an automatic insertion machine, resulting in more rapid assembly and increased reliability.
Abstract:
A voltge boost power supply, for use in a fluorescent lamp ballast (100), having: an inductance (170) coupled between an alternating supply voltage input (108, 110) and an output (134, 136), a switch (128) for controlling the current carried by the inductance, and a current-mode control IC (144) for producing a PWM control signal to control the switch so as to control the current carried by the inductance and thereby control the voltage across the inductance. The current-mode control IC is coupled (138) to the input so that the frequency of the control signal is modulated in accordance with the alternating supply voltage whereby the frequency of the control signal has a maximum value when the magnitude of the alternating supply voltage is a maximum. The power supply thus exhibits reduced harmonic distortion and increased power factor.
Abstract:
An electronic ballast (10) includes a dual function power transistor (16) that supports both power factor correction and inverter functionality. To assist in controlling voltages across this transistor (16) during all phases of operation, two dual function diodes (21, 19) are provided. A boost inductor (14) is coupled to both the dual function power transistor (16) and the bulk energy storage capacitor (22) so that when the dual function power transistor (16) opens, energy from the boost inductor is transferred to the bulk energy storage capacitor (22).
Abstract:
A power factor corrected electronic ballast circuit uses two transformer components (130, 230). An inductively coupled charge pump technique is used for power factor correction (130) while the gates of the transistor switches (20, 30) are driven directly from a resonant inductor (40).
Abstract:
A ballast for operating gas discharge lamps has a voltage boost (10), a half-bridge inverter (14) and a parallel resonant circuit (16). An inverter control (12) inhibits operation of the inverter when power is initially applied to the ballast.