Web Page.

Introduction.

In this article, a design for a driver for a commercial Ultrafire DV-S9 diving light LED flashlight will be presented. Many clones of this flashlight can be found online at very affordable prices. It is a widely used flashlight in spearfishing. More detailed in: https://luicer.github.io/led%20flashlight/Flashlight-Driver-Lineal-eng/

Ultrafire DV-S9

Driver specifications.

The driver design has the following characteristics:

  • Linear type regulator.
  • Adjustable current up to 3A.
  • Input voltage from 3V to 4.2V.
  • Standby current of 4mA.

The block diagram of the proposed design is as follows:

The block diagram of the proposed design is as follows:

Block

Schematics.

The schematic used to implement the design is the following:

Schematic

PCB

A two-sided PCB has been designed to fit into the commercial flashlight casing and be easily replaceable. Considerations have been made for the permissible track currents and EMI control rules to ensure reliable current measurement with a small current measuring resistor.

The assembled PCB looks as follows:

Assembly

BOM.

The bill of required materials is as follows; includes the LCSC component codes.

BOM

Measurement of efficiency and operating voltage.

In order to obtain the driver efficiency, measurements have been taken by varying the input voltage between 2.9 V and 4.2 V, measuring both the input voltage and current, as well as the output voltage and current.

The current as a function of input voltage:

Intensidad

The efficiency as a function of input voltage:

Eficiencia

We can see that the flashlight is usable from 3 V with an intensity of 1 A and an efficiency of 98% up to 4.2 V with a minimum efficiency of 70%.

Design files and License.

All the documentation for the design, including the KiCad PCB project, manufacturing documents, schematic, and bill of materials, can be found in the following GitHub repository:

https://github.com/luicer/Linear-Flashlight-DV-S9-Driver

This design is open source hardware under the permissive CERN OHL-p V2 license.