Clocked power supply

Details Clocked power supply Clocked power supply

1995-08-10

1997-04-29

Pascal, Robert

Electric lamp and discharge devices: systems

Special application

Vehicle

315 77, 315209R, 315208, 315291, 315308, 315DIG7, B60Q 102

Patent

active

056252587

DESCRIPTION:

BRIEF SUMMARY
PRIOR ART

The invention is based on a clocked power supply of the type, having a voltage converter which is clocked by a switching signal and contains a line in which the alternating operating current of the clocked voltage converter flows, with the frequency of the alternating operating current being equal to the frequency of the switching signal, and having a fault current detection circuit which evaluates a voltage drop occurring at an ohmic measuring resistor and which emits a switch-off signal to the voltage converter. DE-A 41 17 589 corresponding to U.S. Pat. No. 5,241,242 discloses such a clocked power supply, which is constructed as an electronic ballast for operating highpressure gas discharge lamps. The electronic ballast contains a voltage converter which is operated in a clocked fashion by means of a switching signal and which initially converts the energy removed from a motor vehicle battery into a direct voltage. A power inverter which produces an alternating voltage of suitable frequency to supply energy to the gas discharge lamp is connected to the direct voltage output of the clocked voltage transformer. The frequency of the switching signal, which frequency corresponds to the operating frequency of the clocked voltage converter, is preferably in the kilohertz range, for example in the range between 10 kHz up to several hundred kHz, while the frequency of the operating voltage emitted to the lamp by the power inverter is preferably in the range of several hundred Hz.
The known clocked power supply contains a fault current detection means which evaluates a voltage drop occurring at an ohmic measuring resistor and which, if appropriate, emits a switch-off signal to the clocked voltage converter. The fault current detection means protects persons who inadvertently touch live parts of the ballast, in particular the connection lines of the gas discharge lamp. The ohmic measuring resistor connects a given terminal at the output of the clocked voltage converter to the electric ground of the vehicle. A fault current which can be evaluated can only occur with the previously known electronic ballast if there is an electrical isolation provided between the output of the clocked voltage converter and the electric ground of the vehicle which is electrically connected to the input of the clocked voltage converter via the battery of the motor vehicle. For electrical isolation, a power transformer which is arranged in the clocked voltage converter and has electrically isolated primary and secondary windings is arranged.
DE-PS 41 41 804 also discloses an electronic ballast for operating gas discharge lamps, which ballast contains a clocked voltage converter to whose output a power inverter is connected in order to provide a suitable alternating voltage for supplying energy to the gas discharge lamp. The potentials across the gas discharge lamp are fixed such that, at least when averaged over time, the gas discharge lamp always has negative potential in relation to the components surrounding it, for example the light or the body of the motor vehicle. This measure prevents a diffusion of ions into the lamp body which damages the gas discharge lamp. The clocked voltage converter is constructed as a simple constant-current step-up transformer which, in addition to the inductor, has as essential components a switching element, a rectifier diode and an output capacitor. Measures which ensure protection of persons against accidental contact with live components are not described.
In an IEEE Report "IAS Annual Meeting", 2-6 Oct. 1977, Los Angeles, p. 1113, a clocked voltage converter is described which has a high degree of efficiency. The clocked voltage converter contains a transformer core which has two separate windings. The connection to a capacitor which is arranged at the output and across which the output direct voltage occurs is made via a capacitor and a separate inductor. The transmission of power to the output can only take place capacitively. The previously known voltage converter can serve as a basis

REFERENCES:
patent: 4507698 (1985-03-01), Nilsson
patent: 4914355 (1990-04-01), Mertens et al.
patent: 5113085 (1992-05-01), Schafer et al.
patent: 5140229 (1992-08-01), Yagi et al.
patent: 5198728 (1993-03-01), Bernitz et al.
patent: 5241242 (1993-08-01), Daub
"IAS Annual Meeting", IEEE Report, Oct. 2-6, 1977, Los Angeles, pp. 1110-1126.

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