摘要:
A starter circuit for a fluorescent tube lamp is connected between the cathode heaters of the tube to provide an intial heating current and then changes to a high impedance to ignite the tube. The circuit is fed by raw rectified a.c. and has a main thyristor requiring a high holding current to maintain the initial conduction. The current through the main thyristor sets up a voltage across a series diode which triggers a second thyristor to reduce the gate voltage of the main thyristor. The main thyristor ceases conduction when the current falls below the holding value and the inductive ballast impedance then produces a high energy striking pulse for the tube. The pulse voltage is limited to increase its duration. One embodiment generates a single pulse only each time the circuit is switched on and another embodiment produces pulses for a period of time before becoming quiescent. The main thyristor and the voltage limiting means are embodied in a monolithic semiconductor structure.
摘要:
A starter circuit for a fluorescent tube lamp is connected between the cathode heaters of the tube to provide an intial heating current and then changes to a high impedance to ignite the tube. The circuit is fed by raw rectified a.c. and has a main thyristor requiring a high holding current to maintain the initial conduction. The current through the main thyristor sets up a voltage across a series diode which triggers a second thyristor to reduce the gate voltage of the main thyristor. The main thyristor ceases conduction when the current falls below the holding value and the inductive ballast impedance then produces a high energy striking pulse for the tube. The pulse voltage is limited to increase its duration. One embodiment generates a single pulse only each time the circuit is switched on and another embodiment produces pulses for a period of time before becoming quiescent. The main thyristor and the voltage limiting means are embodied in a monolithic semiconductor structure.
摘要:
A semiconductor switch device suitable for a.c. power control includesthree4-layer switch components in parallel in a single body of semiconductor material. First and second components are of the same polarity and of opposite polarity to the third component. One end connection of the second component is taken out as a secondary gate connection separate from the corresponding connections of the first and third components. In a preferred mode of use, the secondary gate connection is maintained at a d.c. potential relative to the corresponding connections of the first and third components so as to enable the second component to be conducting during the zero crossings of the a.c. supply and able to maintain the internal voltages required for conduction of either or both of the other components. Circuits are given for integrated circuits embodying the device to permit zero voltage switching power controllers to be made with few external components, and for a proportional controller providing a variable mark-to-space ratio in dependence upon a variable resistor.