Flashlamp drive circuit
View Patent ↗The invention provides a power supply or drive circuit for a pulsed flashlamp which utilizes a two-core component having common windings as both an inductor for arc mode drive and for breakdown triggering of the lamp. Discharge of a capacitor through the inductor and lamp is controlled by a high-speed semiconductor switch which is turned on and off by a suitable control, current flowing from the inductor through a one-way path including the lamp when the switch is off. The control maintains the ratio of the power variation through the lamp to the average power through the lamp substantially constant. The controls may also be utilized to control output pulse shape. Novel protective features are also provided for circuit components during turn on periods for the switch.
1. A circuit for activating a lamp, comprising
an inductor comprising a primary winding and a secondary winding wound on a pair of adjacent cores, one of said cores exhibiting low losses at high frequency and the other being non-saturating during steady state operation of said lamp, said secondary winding being coupled in series with said lamp,
a capacitor coupled across said primary winding,
a trigger switch coupled to said capacitor, wherein activation of said switch causes flow of a current from the capacitor to the primary winding so as to induce a voltage across the secondary winding sufficient to establish a weak discharge in the lamp, and
a source for providing a DC simmer current to the lamp so as to maintain said weak discharge.
2. The circuit of claim 1 , wherein said weak discharge is characterized by a current of less than about 1 amp flowing through the lamp.
3. The circuit of claim 1 , wherein the current flow from the capacitive device to said primary winding has duration of about one microsecond.
4. The circuit of claim 1 , wherein said core exhibiting low losses at high frequency comprises linear ferrite.
5. The circuit of claim 1 , wherein said non-saturating core comprises powdered iron.
6. The circuit of claim 1 , wherein a ratio of a number of turns of the secondary winding to the primary winding is 10:1.
7. The circuit of claim 1 , further comprising:
another capacitor coupled in series with said lamp,
a semiconductor switch coupled in series between said another capacitor and said lamp, and
a control circuit for enabling said semiconductor switch in response to detection of a simmer current to cause discharge of energy stored in said another capacitor into the lamp so as to cause operation of the lamp in an arc mode.
8. The circuit of claim 7 , wherein said control circuit comprises a comparator applying an enable/disable signal to said semiconductor switch.