FLASHLAMP DRIVE CIRCUIT

• US 20080033413A1
• Filed: 09/24/2007
• Published: 02/07/2008
• Est. Priority Date: 03/01/2001
• Status: Active Grant

• Current Assignee: Palomar Medical Technologies Incorporated (Hologic Incorporated)
• Original Assignee: Palomar Medical Technologies Incorporated (Hologic Incorporated)
• Inventors: Togatov, Vycheslav, Gnatyuk, Peter, Inochkin, Mikhail
• Granted Patent: US 7,531,967 B2
• Time in Patent Office: Days
• US Class Current: 606/11
• CPC Class Codes: A61B 2018/1807 using light other than laser radiation
• CPC Class Codes: H05B 41/30 in which the lamp is fed by pulses, e.g. flash lamp
• CPC Class Codes: H05B 41/34 to provide a sequence of flashes

Abstract

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.

Claims

1. A method for operating a lamp to treat skin, comprising:

applying electrical power to an electrical drive circuit including an energy storage device and connected to the lamp to cause the lamp to generate an optical radiation pulse,

measuring electrical power through the lamp, and

controlling discharge of energy from the energy storage device into the lamp in response to said measured electrical power so as to maintain a substantially constant ratio of power variation to an average power through the lamp during the optical pulse.

2. The method of claim 1, further comprising selecting said energy storage device to include a capacitor.

3. The method of claim 2, wherein said controlling step comprises enabling discharge of energy from the capacitor into the lamp in response to said measured electrical power reaching a selected low threshold and preventing said energy discharge in response to said measured electrical power reaching a high threshold.

4. The method of claim 3, wherein said controlling step comprises utilizing a semiconductor switch disposed between said capacitor and said lamp such that turning on said switch results in enabling discharge of energy from the capacitor to the lamp and turning off said switch results in preventing said energy discharge.

5. A drive circuit for a pulsed lamp, comprising:

a first closed loop current path comprising a capacitor and an inductor coupled in series with the lamp,

a second closed loop current path comprising the inductor coupled in series with the lamp,

a controller circuit for selectively activating one of said current paths based on a current flowing through the lamp so as to maintain current fluctuation through the lamp within a pre-selected range.

6. The circuit of claim 5, further comprising a semiconductor switch connected in series between said capacitor and said lamp to control discharge of energy stored in said capacitor into the lamp.

7. The circuit of claim 6, further comprising a current sensor coupled to said lamp for detecting the current flowing therethrough.

8. The circuit of claim 7, wherein said current sensor comprises a resistor connected at one end to a terminal of said lamp and at another end to ground such that the current flowing through said lamp induces a voltage across said resistor indicative of the current level.

9. The circuit of claim 6, wherein said second current path comprises a one-way current switching device for providing a one-way flow of current from the inductor to the lamp so as to maintain current flow through the lamp when the first current path is inactive.

10. The circuit of claim 9, wherein said one-way current switching device comprises a diode.

11. The circuit of claim 7, wherein said controller receives a signal from said current sensor indicative of the current flowing through the lamp.

12. The circuit of claim 8, wherein said controller comprises a comparator receiving at one input a reference voltage (V_ref) and at another input said voltage across the resistor, said comparator applying an output signal to said switch based on a difference between said input voltages to cause enabling or disabling of said switch.

13. 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.

14. The circuit of claim 13, wherein said weak discharge is characterized by a current of less than about 1 amp flowing through the lamp.

15. The circuit of claim 13, wherein the current flow from the capacitive device to said primary winding has duration of about one microsecond.

16. The circuit of claim 13, wherein said core exhibiting low losses at high frequency comprises linear ferrite.

17. The circuit of claim 13, wherein said non-saturating core comprises powdered iron.

18. The circuit of claim 13, 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.

19. The circuit of claim 18, wherein said control circuit comprises a comparator applying an enable/disable signal to said semiconductor switch.

20. The circuit of claim 13, wherein a ratio of a number of turns of the secondary winding to the primary winding is 10:

1.

21. A drive circuit for a lamp, comprising

an energy storage device connected in series with the lamp to provide the lamp with sufficient energy for generating an optical radiation pulse,

a switch coupled to the storage device and the lamp so as to permit discharge of energy stored in the device into the lamp when enabled and to block the discharge when disabled, and

a control circuit for selectively enabling or disabling said switch in response to power dissipated by said lamp so as to maintain a substantially constant ratio of power variation to an average power through the lamp during said pulse.

22. The circuit of claim 21, wherein said switch comprises a high speed semiconductor switch.

23. The circuit of claim 21, wherein said energy storage device comprises a capacitor.

24. The circuit of claim 23, further comprising an inductor connected in series with said capacitor and said lamp.

25. The circuit of claim 24, further comprising a diode disposed in a closed current path with said inductor and said lamp to provide a one-way current path from the inductor to the lamp for maintaining a current through the lamp when the switch is disabled.

26. The circuit of claim 25, further comprising a saturable inductor connected in series with said diode to inhibit current flow from the switch to the diode while the switch is transitioning from a disabled state to an enabled state or from an enabled state to a disabled state.

27. The circuit of claim 26, further comprising another saturable inductor connected in series with said switch to inhibit current flow through the switch during a transition period in which the diode is turning on and the switch is turning off.

28. A method of operating a lamp to treat skin, comprising:

applying power from an energy storage device to the lamp to cause the lamp to generate an optical pulse,

measuring power through the lamp during at least a portion of the pulse, and

controlling the flow of energy from the storage device to the lamp in response to said measured power so as to ensure power through the lamp during said pulse remains within a range defined by pre-selected low and high thresholds.

29. The method of claim 28, further comprising selecting said energy storage device to be a capacitor.