Electric lamp and discharge devices: systems – Surge generator or inductance in the supply circuit – Circuit interrupter in the inductance circuit
Reexamination Certificate
2001-10-30
2003-11-04
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Surge generator or inductance in the supply circuit
Circuit interrupter in the inductance circuit
C315S289000, C315S246000, C315S360000, C315S274000, C315S2090SC
Reexamination Certificate
active
06642673
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to a disable circuit that stops the ignitor function of a high intensity discharge (HID) lamp ignition circuit. More particularly, the invention relates to an apparatus and method to control the timing and triggering of the disable function of the igniter circuit.
BACKGROUND OF THE INVENTION
High intensity discharge (HID) lamps such as metal halide (MH) and high pressure sodium (HPS) lamps have increasingly gained acceptance over incandescent and fluorescent lamps for commercial and industrial applications. HID lamps are more efficient and more cost effective than incandescent and fluorescent lamps for illuminating large open spaces such as construction sites, stadiums, parking lots, warehouses, and so on, as well as for illumination along roadways. An HID lamp comprises at least an arc-tube containing two electrodes, chemical compounds and a fill gas. The fill gas can comprise one or more gases. To initiate operation of the lamp, the fill gas is ionized to facilitate the conduction of electricity between the electrodes.
HID lamps can be difficult to start. An HID lamp such as a conventional HPS lamp uses a 2500 to 4000 volt pulse at least once per half-cycle and at selected times during the cycle in order to start, as set forth in a number of standards such as ANSI C78.1350 on HPS lamps, for example. An ignitor is used to provide the necessary pulses to start the conventional HID lamp. If the lamp is extinguished after lamp operation has elevated lamp temperature, the lamp cannot be restarted until after the lamp cools down and the fill gas can be ionized again. For many types of HID lamps, this lamp cooling period can be between approximately 40 seconds and 2.5 minutes, which can be considered unacceptable in situations where, for example, emergency lighting is desired.
A number of circuits have been developed to start or hot restrike HID lamps. These ignitors generally include resistors, pulse transformers and other components, in addition to a conventional ballast. These devices can reduce system efficiencies and substantially increase system cost.
An exemplary ignitor
100
is depicted in FIG.
1
. Terminals
102
and
104
of a lighting unit are connected to an AC power source
106
, as well as to a ballast
108
and a lamp
110
. The ballast
108
comprises a tap
112
and two winding portions
114
and
116
. The ignitor
100
has terminals which are connected to terminals
102
,
112
and
110
. A charging circuit for hot restarting a high pressure xenon HPS lamp or other HID lamp having similar hot restart requirements is provided which comprises a semiconductor switch
118
such as a silicon-controlled rectifier (SCR) or the like is connected so that one end of its switchable conductive path is connected to the end of the first portion
116
of the ballast. The other end of the conductive path of the SCR
118
is connected to the tap
112
via a storage capacitor
120
. A number of sidacs
122
or other breakdown devices are connected between the gate and the anode of the SCR
118
. A current-limiting resistor
126
is provided in series with the sidacs
122
and
124
. If the voltage on the capacitor
120
increases to a level which reaches or exceeds the threshold voltage of the breakdown devices
122
and
124
, the sidacs
122
and
124
become conductive, placing the SCR
118
in a conductive state. Accordingly, the capacitor
120
discharges through the portion
18
of the ballast. Because the winding portions
114
and
116
of the ballast are electromagnetically coupled, the portion
116
of the ballast operates as the primary of a transformer in that a voltage is induced in the winding portion
114
. The high voltage generated in the winding portion
114
of the ballast
108
is imposed on the lamp
110
. The relationship of the winding portions
114
and
116
is selected to create a voltage using the SCR
118
and the sidacs
122
and
124
which is sufficiently high to ionize the material within the arc tube of the lamp
110
.
With further reference to
FIG. 1
, a charging circuit
144
for the capacitor
120
is connected between the tap
112
and the terminal
102
at the other side of the AC power source
106
. This charging circuit preferably comprises two diodes
128
and
130
, a pumping capacitor
132
and two radio frequency chokes
134
and
136
connected in series between the tap
112
and the terminal
102
. Two diodes
138
and
140
are connected between the capacitors
120
and
132
and are poled in the opposite direction from the diodes
128
and
130
.
The charging circuit
144
depicted in
FIG. 1
provides for the controlled, step-charging of the storage capacitor
120
. During one half cycle of the AC power source
106
, a current flows through the chokes
134
and
136
, the capacitor
132
and the diodes
128
and
130
to charge the capacitor
132
. The capacitor
132
is selected to be relatively smaller than the capacitor
120
(e.g., 0.047 microfarads (&mgr;F) versus 5 &mgr;F). On the next half cycle of the AC power source
106
, the capacitor
120
is charged and the voltage across the capacitor
132
increases the incoming half wave from the AC power source
106
so as to provide energy on the order of 2.7 microjoules to the storage capacitor
120
. Since the capacitor
120
requires more energy due to its relative size, the capacitor
120
can be provided with energy from both the incoming AC signal and the capacitor
132
in one cycle. On the next half cycle, the capacitor is charged again and delivers energy to the capacitor
120
again on the subsequent half cycle. Thus, the charge on the capacitor
120
is increased with each alternate half cycle using a pumping action.
When the capacitor
120
reaches the breakdown voltage of the sidacs
122
and
124
, the sidacs become conductive and therefore render the SCR
118
conductive. The capacitor
120
therefore discharges through the portion
116
of the ballast
108
to generate a high voltage in the portion
114
of the ballast. The large magnitude of the capacitor
120
discharges significantly more energy into the magnetic field of the ballast
108
as compared with a conventional HID lamp ignitor and therefore excites the ballast
108
to a relatively high degree. The highly excited ballast
108
, with its corresponding collapsing magnetic field, pushes the lamp into a discharge state and therefore a low impedance state so that the discharge state can be maintained by the normal AC power source
106
. The discharging capacitor
120
produces current flow which is in the same direction as the continued current flow produced by the collapsing field, and which is provided through the lamp as the SCR
118
is turned off by the instantaneous back voltage bias placed on the capacitor
120
by the same collapsing field energy. The resistor
152
can be connected in series with the SCR
118
to cause the peak of the high voltage pulse to be lower and the base (i.e., width) of the pulse to be longer. The resistor
152
limits the high voltage and therefore reduces dielectric stress to allow the use of lower cost magnetic components.
The ignitor
100
depicted in
FIG. 1
further comprises an HPS lamp starting circuit comprising a capacitor
146
connected in series with a resistor
148
and a sidac
150
or similar breakdown device. The resistor
148
is connected to the junction between the inductors
134
and
136
and the capacitor
132
. The ignitor
100
comprises a current-limiting resistor
152
in series with the parallel combination of the SCR
118
and the sidacs
122
and
124
.
The above-mentioned HID lamps should be provided with a disabling circuit such that, if the lamp fails to start, the disabling circuit would discontinue the hot or cold strike used to initiate the HID lamp. This feature is useful in prolonging the life expectancy of the ignitor, helps protect the ballast system, and provides the ability to apply HID ignitors to harsh and hazardous environments.
Accordingly, a need exists for a reliable m
Flory, IV Isaac Lynnwood
Hudson Christopher Allen
'Hubbell Incorporated
Goodman Alfred N.
Kendall Peter L.
Longanecker Stacey
Vo Tuyet T.
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