Step down circuit for an LED flashlight

• US 20040124782A1
• Filed: 12/31/2002
• Published: 07/01/2004
• Est. Priority Date: 12/31/2002
• Status: Active Grant

• Current Assignee: Sun Yu
• Original Assignee: Sun Yu
• Inventors: Yu, Sun
• Granted Patent: US 6,987,366 B2
• Time in Patent Office: Days
• US Class Current: 315/200A
• CPC Class Codes: F21L 4/005 the device being a pocket lamp F21L4/022, F21L4/045, F21L4/085 take precedence
• CPC Class Codes: F21V 23/0414 specially adapted to be used with portable lighting devices
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/375 using buck topology

Abstract

The present invention relates to a voltage reducing circuit for use with an LED flashlight. The LED flashlight according to the invention comprises a battery, a solid state light source having an on voltage less than the voltage of the battery, and a voltage reducing circuit in electrical communication with the battery and the solid state light source. The voltage reducing circuit is operative to reduce the voltage from the battery to a level that is slightly above the on-voltage threshold of the solid state light source. In this manner, power expended from the battery by the solid state light source is minimized such that the need for battery replacement is prolonged.

Claims

1. A flashlight comprising:

a battery having a voltage;

a light emitting device having an on-voltage less than the voltage of said battery;

a voltage reducing circuit in electrical communication with said battery and said light emitting device, said voltage reducing circuit operative to reduce the voltage from said battery to greater than or equal to said on-voltage of said light emitting device; and

a housing wherein said battery, said light emitting device, and said voltage reducing circuit are supported such that said light emitting device emits light from said housing upon receiving said on-voltage.

2. The flashlight of claim 1 further comprising a switch for connecting said battery to said voltage reducing circuit.

3. The flashlight of claim 1 further comprising a switching circuit operative to switch said light emitting device on and off at a rate that causes the light to appear steady state.

4. The flashlight of claim 1 wherein the flashlight is a miniature flashlight.

5. The flashlight of claim 1 wherein the voltage step reducing circuit is transformerless.

6. The flashlight of claim 3 wherein said switching circuit is an astable multi-vibrator circuit.

7. The flashlight of claim 1 wherein said voltage reducing circuit comprises a DC/DC converter.

8. The flashlight of claim 1 wherein said voltage reducing circuit comprises a voltage regulator.

9. The flashlight of claim 1 wherein said voltage reducing circuit comprises a Zener diode.

10. The flashlight of claim 1 wherein the light emitting device is a solid state device.

11. The flashlight of claim 10 wherein the solid state device is a light emitting diode.

12. The flashlight of claim 10 wherein the solid state device is a laser diode.