Abstract: A circuit for powering a fluorescent lamp has a direct current power supply (10). An inverter (12) is coupled to the direct current power supply (10) and provides a lamp current to the fluorescent lamp load (14). The inverter(12) is connected to an inverter control circuit (18). A protection circuit (16) for detecting lamp current is coupled to the inverter control circuit (18) such that the inverter control circuit (18) turns off the inverter (12) whenever the protection circuit detects the absence of lamp current.

Abstract: A capacitor (16) coupled in series with series coupled gas discharge lamps (11 and 12) will effectively block direct current from flowing through the capacitor (16). A detector circuit including a high impedance resistor (17) and transistor (18) provide an alternate path for a small direct current flow, thereby enabling a direct current voltage across the capacitor (16) to be detected. The presence or absence of this direct current voltage provides a reliable indicia of the existence or absence of a gas discharge fault.

Abstract: A ballast for providing a dimmable fluorescent lamp (42) has a potentiometer (46) connected to AC power source (10). The potentiometer (46) is connected to a dimming circuit (44). In response to changes in the resistance of the potentiometer (46), dimming circuit (44) causes the duty cycle of a pulse width modulator (18) to change, thereby dimming the fluorescent lamp (42). A dimming disable circuit (60) disables the dimming circuit (44) when power is initially applied to the ballast (6) so that the lamp (42) will ignite.

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: An electronic ballast 10 includes a single 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 and 19 are provided.

Abstract: A circuit with a transistor common to both the inverter and the boost converter powers a gas discharge lamp. In a half-bridge inverter, a boost inductor is coupled between the rectifier and the junction between two switching circuits.

Abstract: A circuit for powering gas discharge lamps includes a power factor correction inductor coupled to a source of rectified, pulsating AC power. An energy storage circuit is connected to the power factor correction inductor, and a switch is coupled to a junction between the power factor correction inductor and the energy storage circuit. A resonant circuit couples the energy storage circuit to the gas discharge lamps.

Abstract: A circuit for powering a gas discharge lamp from a source of a first frequency AC power has a a first rectifier for converting the first frequency AC power into a first DC power, a capacitor and driver for converting the DC power to a second frequency AC power. A second rectifier is used to increase the power factor for the circuit. A control is provided to disable the second rectifier if the lamp is removed from the circuit.

Abstract: A circuit (100) for powering fluorescent lamps (102, 104 & 106) includes a switch (50) having "open" and "closed" positions. When power is initially applied to the circuit, the lamps are powered at full power to enable them to "strike". After a short period, the power is reduced to the lamp. A control circuit (300) thereafter senses if the switch has been "toggled". If toggled, the power to the lamps is increased, and the lamps brighten. The circuit uses a conventional two-position switch and conventional wiring and avoids the need for additional switches and additional wiring.

Abstract: A control circuit (C) for controlling fluorescent lamps (102, 104 & 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 timne 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: A driver circuit for one or more gas discharge lamps (102, 104, 106) includes: a self-oscillating, series-resonant oscillator (196, 198, 178, 180) for producing a constant-frequency, high-frequency output voltage for application to the lamps; an inductive voltage boost IC (144) for causing the oscillator to produce a temporary excessive boosted output voltage (300 V) when the voltage boost IC is initially activated and a steady-state boosted output voltage (250 V) thereafter, ensuring striking of the lamps and prolonging their life.

Abstract: A circuit for driving one or more gas discharge lamps (102, 104, 106) from a nominal-level voltage supply includes: a voltage boost IC (144); a self-oscillating, series-resonant oscillator (196, 198, 178, 180) for producing a high-frequency output voltage for application to the lamps via an output-coupling transformer (212); and a voltage clamp (215A, 215B) coupling the transformer to the oscillator input (174, 176). The voltage boost IC is arranged to regulate the power drawn by the circuit to a constant level if the supply voltage is greater than 95% of its nominal value. If the supply voltage falls to less than 95% of its nominal value, regulation is lost and the circuit draws less power in proportion to the fall in the supply voltage. If the supply voltage falls to less than 90% of its nominal value the clamp operates to reduce the power drawn by the circuit at a rate greater than that of the fall in the supply voltage.

Abstract: A driving circuit for one or more gas discharge lamps (102, 104, 106) having heatable filaments (102A&B, 104A&B, 106A&B) includes: a self-oscillating, series-resonant oscillator (196, 198, 178, 180) for producing a high-frequency output voltage for application to the lamps via an output-coupling transformer (212); a resistive-capacitive divider (190, 192) for starting-up the oscillator after a first delay; a voltage boost IC (144) for causing the oscillator to produce a boosted output voltage when the voltage boost IC is activated and an unboosted output voltage when the voltage boost IC is unactivated; and a resistive-capacitive divider (170, 172) for starting-up the voltage boost IC after a second delay.

Abstract: A flyback type power supply has a nominal 12 volt secondary winding that is connected to a rectifier through the primary winding of a saturable transformer. The secondary winding of the saturable transformer is connected in series with the DC load current supplied by the rectifier. A filter capacitor completes the circuit. Under no load conditions, the impedance presented by the primary of the saturable transformer is high and the output voltage developed across the filter capacitor is maintained at about 12.25 volts. Under full load conditions, the impedance presented is negligible.

Abstract: An automatic input switching circuit for a power supply includes a transformer with two primary windings, normally connected in series and connectible in parallel by relay contacts for operation in a doubler mode. The secondary winding supplies a rectifier for developing a DC output voltage and a voltage doubler for developing a higher voltage than the output voltage. The voltage doubler charges a capacitor that stores energy for operating the relay when a transistor switch is closed. The transistor switch is normally held in a nonconductive state by an inhibit transistor driven from a comparator that switches states when the voltage across the capacitor reached a predetermined level. A voltage sensing arrangement compares the rectifier output voltage with a reference voltage and when it reaches a certain level, another comparator switches states to activate a disable transistor.

Abstract: A fluorescent lamp supply includes a self-resonant converter for developing high voltage AC for application to the fluorescent lamp. The on-time of the converter is controlled by a pulse width modulator circuit comprising dual comparators, with one comparator being operated as a low frequency oscillator and the other comparator being used to disable the converter by operating a gate transistor. A reference potential is applied to a potentiometer for controlling the output comparator conduction threshold and for varying the width of the pulses of the pulse width modulator. Variation of the reference potential changes the brightness of the fluorescent lamp. The pulse width modulator duty cycle is inversely proportional to changes in the DC source voltage for maintaining constant lamp brightness with changes in the DC source voltage.

Abstract: A protection circuit for a switched mode power supply has a reference voltage applied through a resistor to a first input terminal of a comparator. The second input terminal of the comparator is supplied with an indicating voltage that is a function of the magnitude of input current to the supply. A capacitor precludes rapid changes in the voltage applied to the second input terminal. When a trip level is reached, the comparator operates a latch for disabling the pulse width modulator of the supply. A diode is coupled between the high capacity voltage output of the supply and the first input terminal of the comparator for rapidly changing the voltage applied to the first input terminal to operate the latch, in response to a significant decrease in voltage at the high capacity output.

Abstract: A circuit locater includes a passive signal device adapted to be plugged into a power outlet to draw a large amplitude current pulse of very short duration (identification signal) from the power source supplying the outlet. A receiver has a pickup coil that senses the magnetic field generated by the identification signal current. A sensitivity control reduces the sensitivity of the pickup coil until an output signal is produced only when the receiving coil is adjacent to the circuit breaker of the electrical control panel that is supplying power to the passive signal device.

Abstract: A constant current battery charger includes a bucking regulator comprising a power switch transistor, a diode, an inductor and a voltage sensitive switch with adjustable delay for controlling the power switch transistor. The hysteresis or delay is obtained with a Schmitt trigger and the effect is a stable pulse width modulator in which the duty cycle of the power switch transistor is varied. A current foldback circuit includes a zener diode coupled to the battery for changing the sensitivity of the switch to substantially reduce charging current when a battery voltage corresponding to a fully charged state is reached.

Abstract: A constant current battery charger includes a bucking regulator comprising a power switch transistor, a diode, an inductor and a voltage sensitive switch with adjustable delay for controlling the power switch transistor. The hysteresis or delay is obtained with a Schmitt trigger and the effect is a stable pulse width modulator in which the duty cycle of the power switch transistor is varied. A temperature sensor adds resistance to change the sensitivity of the switch and reduce charging current when a predetermined battery temperature is reached. A speed up circuit consisting of a shorting transistor is connected across the base-emitter of the switch transistor.