BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings facilitate understanding of the various embodiments of this invention. In such drawings:
FIG. 1 is a block diagram of a conventional ballast according to the prior art;
FIG. 2 is a block diagram of a power-saving and stabilizing ballast according to the present invention;
FIG. 3 is a circuit diagram of an electromagnetic compatibility (EMC) filter circuit of the present invention;
FIG. 4 is a circuit diagram of an active power factor correction (APFC) circuit of the present invention;
FIG. 5 is a circuit diagram of an abnormal state protection circuit of the present invention;
FIG. 6 is a circuit diagram of an over-voltage protection circuit of the present invention;
FIG. 7 is a circuit diagram of an over-current protection circuit of the present invention;
FIG. 8 is a circuit diagram of a first embodiment of a pre-heating start-up circuit of the present invention;
FIG. 9 is a circuit diagram of a second embodiment of a pre-heating start-up circuit of the present invention;
FIG. 10 is a circuit diagram of a third embodiment of a pre-heating start-up circuit of the present invention;
FIG. 11 is a circuit diagram of a first embodiment of a multi-loads working circuit of the present invention; and
FIG. 12 is a circuit diagram of a second embodiment of a multi-loads working circuit of the present invention.
DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS
Various preferred embodiments of the instant invention will now be described with reference to the figures, wherein like reference numerals designate similar parts throughout the various views.
Referring to FIG. 2, a power-saving and stabilizing ballast of the present invention includes a bridge rectifier circuit 21, an electrolytic capacitive filter circuit 22, a half bridge inverter circuit 23, an LC output circuit 24, all of which are sequentially and electrically connected. The power-saving and stabilizing ballast further includes an electromagnetic compatibility (EMC) filter circuit 25 electrically connected between a voltage input port 20 and the bridge rectifier circuit 21 for restraining high frequency currents from damaging electric power; a power factor correction circuit 26 electrically connected between the bridge rectifier circuit 21 and the electrolytic capacitive filter circuit 22 for enhancing power factor, reducing harmonic and achieving a constant power output; and an abnormal state protection circuit 27 electrically connected to the half bridge inverter circuit 23 for protecting the ballast against damage from abnormal states.
Referring to FIG. 3, a circuit diagram of the EMC filter circuit 25 is shown. The EMC filter circuit 25 consists of resistors and capacitors.
Referring to FIG. 4, the power factor correction circuit 26 in the present embodiment is preferably an active power factor correction (APFC) circuit composed of a special integrated circuit, a transistor and some peripheral electronic components. Relating to active components, so the power factor correction circuit 26 is named APFC circuit.
Referring to FIG. 5, a circuit diagram of the abnormal state protection circuit 27 is shown. As is shown, the capacitor 271 is arranged a secondary winding. Thus, in the normal work state, the voltage induced on the capacitor 271 is only 20-25V (or lower). Such low voltage cannot turn on the bidirectional diode 272, so the diode 273 and the dynatron 274 cannot get enough base currents and trigger currents, and therefore the diode 273 and the dynatron 274 are in cut-off and short state. In such condition, the abnormal state protection circuit 27 does not work. Once an abnormal state happens, the voltage induced on the capacitance 271 immediately exceeds to the trigger voltage needed to trigger the bidirectional diode 272. This voltage makes the bidirectional diode 272 turn on and, in turn, turns on the diode 273 and the dynatron 274 with the result that the half bridge inverter circuit 23 stops working and does not turn on again until the abnormal state is eliminated.
Referring to FIG. 6, the present invention provides an over-voltage protection circuit 28. The over-voltage protection circuit 28 has a zinc oxide voltage dependent element or resistor 29 connected in Parallel to the EMC filter circuit 25, which clips transient spikes or limits amplitude of over-voltages, thereby reduces the voltage of the ballast to prevent transient spikes or over voltages from damaging the ballast.
Referring to FIG. 7, the present invention also provides an over-current protection circuit 30. The over-current protection circuit 30 has a current limiting resistor or negative temperature coefficient (NTC) resistor 31 connected therein in series. The resistance of the NTC resistor 31 is quite big in the room temperature, thereby suppresses effectively the surge current.
The present invention also provides a pre-heating start-up circuit 32 connected to the LC output circuit 24 for providing a cathode of the lamp a pre-heating current and a predetermined pre-heating time to heat the cathode (glowers) to a desired temperature needed to turn on the cathode. However, before the cathode generates enough electron-fog and reaches excited state, the voltage put on the lamp should be low enough to prevent glow discharge, thereby protecting the cathode from damage.
FIG. 8 is a circuit diagram of a first embodiment of the pre-heating start-up circuit 32 of the present invention. An LC resonant circuit composed of a first capacitor 321 and an inductance 322 has a fluorescent lamp 320 connected therein in series. A second capacitor 323 and a thermosensitive element such as a positive temperature coefficient (PTC) resistor 324 connect respectively in parallel to the fluorescent lamp 320. When the pre-heating start-up circuit starting, the resistance of the PTC resistor 324 is low, thereby to limit the voltage of the fluorescent lamp 320, which prevents the cathode of the lamp from glow discharge. The temperature and the resistance of the PTC resistor 324 increase with time. After 0.4 s to 1.5 s, the voltage of the second capacitor 323 increases rapidly to breakdown and enkindle the cathode of the lamp 320.
FIG. 9 is a circuit diagram of a second embodiment of the pre-heating start-up circuit 32 of the present invention which is similar with that shown in the first embodiment of FIG. 8 except that the PTC resistor 324 has a third capacitor 325connected thereto in series, therefore a detailed description of which is omitted here from.
FIG. 10 is a circuit diagram of a third embodiment of a pre-heating start-up circuit 32 of the present invention which is similar with that shown in the second embodiment of FIG. 9 except that the PTC resistor 324 has a fourth capacitor 326 connected thereto in parallel, therefore a detailed description of which is also omitted here from.
A multi-loads working circuit 33 is provided to connect to the LC output circuit 24. The multi-loads working circuit 33 is easy to install, reliable and power saving. As shown in FIG. 11, the multi-loads working circuit 33 is an LC lamps series resonant circuit for making four fluorescent lamps work simultaneity. Because the LC lamps series resonant circuit of the present invention is well known to persons ordinarily skilled in the art, a detailed description of such structure is omitted here from.
FIG. 12 shows a second embodiment of a multi-loads working circuit 33′ of the present invention. The multi-loads working circuit 33′ is a current push-pull lamps output circuit for making four fluorescent lamps work simultaneity. Because the current push-pull lamps output circuit of the present invention is well known to persons ordinarily skilled in the art, a detailed description of such structure is omitted here from.
While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention.
Patent Application
20070267981
