Using Solid-State Over-Voltage Protection Devices for High Intensity Discharge Lamps Ignition
J. García-García, M. Rico-Secades, E. L. Corominas, J. M. Alonso, J. Ribas, J. Cardesín, A. J. Calleja Universidad de Oviedo G.E.I., Grupo de Electrónica Industrial Gijón, Spain
[email protected] Abstract—In this paper, a new igniter for HID lamps based on solid-state over-voltage protection devices (sidacs) is proposed. A complete analysis of the proposed igniter, as well as a design method and some implementation considerations, are discused.
reactive elements, but circuitry complexity increases. Besides, the use of relays decreases circuit reliability.
The proposed Igniter has been implemented in two different HID ballast inverters: resonant and square wave one. When the voltage in the lamp reaches a threshold value, the protection device generates a pulse that is transferred to the lamp by a small transformer in series with the lamp. If the circuit is designed properly, the pulse has enough energy as to ionize the gas in the discharge tube, thus starting the lamp.
The proposed circuit provides ignition capability with a small number of components wich are passive components (resistors, capacitors and a small transformer), and solid state devices (diodes, sidacs). There are no components such as relays in this starter.
If the inverter of the lamp ballast is a non resonant one, an auxiliar igniter is needed.
In section II the solid state protection device is outlined. In section III, an analysis of the operation of the HID lamp igniter is done. After this analysis, a design method of the parameters of the igniter is made in section IV. In section V and VI, some considerations are shown when it comes to implement the igniter in several high frequency inverters. Finally, in section VII, the experimental results are shown.
Several prototypes for different HID lamps and different High Frequency Inverters have been built and tested. Keywords—HID Lamps, electronic ballast, resonant inverters, square wave inverters, lamp igniters, electronic protection devices.
II.
THE SOLID-STATE OVER-VOLTAGE PROTECTION DEVICES The devices used as single high voltage pulse generators are sidacs. In this section there is an outline of the operating characteristics of those protection devices.
I. INTRODUCTION One of the major problems in lighting electronics is the starting of the lamp. High Intensity Discharge (HID) Lamps need a starting voltage of sufficient amplitude and appropiate rise and width time in order to start properly [1,2]. Some electronic inverters, as resonant ones, have ignition capability if they are designed properly. But if the inverter has no capability of providing this starting voltage, an external igniter must be used during the starting of the lamp.
A. The Sidac The symbol of this solid state device is shown in figure 1, while its electronic behaviour is shown in figure 2.
The proposed igniter is very easily adaptable to different operating modes for ignition and steady-state. If the inverter of the lamp ballast is a resonant tank, 2 basic solutions are found for starting the lamp. First solution would be using a single resonant tank, changing the operating frequency in order to provide proper operation during start-up and steady state. Other possibility would be using a relay to switch between two different resonant tanks, one for start-up and another for steady-state operation [3,6]. The main drawback of the first approach are the high stresses in reactive elements during start-up, leading to higher ballast cost and volume. The second approach allows a better optimization of
Figure 1. Symbols of Sidac
In the stand-by mode, sidac exhibits a high off-state impedance, appearing transparent to the circuit they're attached to. Upon application of a voltage exceeding the switching voltage (VS), sidacs breakout, providing a short circuit condition until the current flowing through the device is either interrupted or drops bellow the sidac's holding current
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D1 charges the capacitor C1. The resistor R1 in figure 2 is a high value resistor, so the voltage in steady state acros C1 doesn't reach a dangerous value. It means R1 can be modeled as an open circuit in the starting operation of the circuit. The sidac is actually an open circuit when VSID
