Driver Circuits, Page 3
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Last Updated on: Wednesday, May 11, 2011 04:59 PM
Circuits Designed by Dave Johnson, P.E. :
  • Constant Current LED Driver
    Bob Pease from National Semiconductor came up with this circuit and I have used it many times.  It maintains a constant current through one or more LEDs.  A single resistor controls the desired current.
  • Constant Current LED Driver 5
    LEDs are current driven devices.  The light they produce is proportional to the current flowing though them.  One way to maintain a fairly steady light output is to keep the current through the LED fixed, even as the supply voltage may change.  A classic way to do this is shown below.  This works fairly well but it has two weaknesses.  It requires a 0.6v voltage drop across the current shunt resistor and due to the base-emitter voltage temperature sensitivity, the current increases with temperature.    ....
Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:
Backlight CCFL Direct Drive Design Reference AN-13 -  Application Note 13 from Microsem.....[App Note]
Balanced Audio Input Circuit -  (design circuit added 8/02)
Balanced Line Driver & Receiver -  Use these to eliminate hum for long signal leads (schematic / Circuit design added 9/02)
Balanced Line Inputs/Outputs for Silicon Graphics workstations -  AS075 Jenson Transformer Application Note  (app note 7/02)
Bi-Polar LED Driver -  Some 2-leaded LEDs produce red and green. These are called Bi-polar LEDs.  This circuit alternately flashes a red/green bi-polar LED
Bridge Circuit Drives Apex-AN03 -  Apex App Note.....
Brush Type DC Motor Drive Apex-AN24 -  Apex App Note.....
Brush-Dc Servomotor Implementation using PIC17C756a -  Microchip Application Note Published 12-Oct-99.....[App Note]
Buck Configuration High-Power LED Driver -  Microchip Application Note Published 4-Jan-06.....[App Note]

Buck/Boost-Based LED Drivers using the HV9910 -  Supertex Semiconductors (app note added 6/06)
Build your own LED cube -  This month's featured Gadget Freak is provided by an old favourite of the blog, Peter Griffiths. He shares all the details necessary to build your own 5 x 5 LED cube…
Calculating Power Dissipation for Differential Line Drivers -  National Semiconductor Application Note.....[App Note]
Cascaded converter boosts LED drive capability -  16-Aug-07 Issue of EDN  A two-stage boost converter can drive a string of 20 to 30 LEDs..... [Design Idea by Grant Smith, National Semiconductor, Phoenix, AZ]
Cheap PWM IC makes synchronous gate driver -  02/04/99 Issue of EDN  A system with a µP, memory, and peripherals usually requires several power-supply voltages. Designers typically use local switching regulators to produce the desired voltage rails. One of the most common topologies, the synchronous buck regulator, converts a 5 or 12V bus to some other, lower voltage.  This approach has gained vast acceptance, thanks to its relative simplicity.....Page includes several designs.  Scroll to find this one..... [Design Idea by Dimitry Goder, Switch Power Inc, Campbell, CA]
Chipiplexing efficiently drives multiple LEDs using few microcontroller ports -  27-Nov-08 Issue of EDN  "Chipiplexing" approach simultaneously drives two LEDs..... [Design Idea by Guillermo Jaquenod, La Plata, Argentina]
Circuit Adapts Differential Input to Drive Coax -  05/08/97 EDN-Design Ideas.....Uses an HFA1100 or HFA1105 to convert a balanced input signal to a single-ended output signal, uses positive feedback to characteristic-impedance matching while increasing the available output swing, as compared with using a simple series termination resistor..... [Design Idea by Donald Whitney Jr, Harris Semiconductor, Melbourne, FL]
Circuit delivers dimming control for white LED driver -  28-Oct-04 Issue of EDN  The demand for power in color cell-phone handsets is constantly increasing. New applications steadily emerge, making it imperative to reduce power consumption in the design. Examination of usage data shows thatthan 50% of the power consumed is in providing backlighting for the color screen. People use the phones for playing games and MP-3s and a multitude of other heavy-duty, multimedia f..... [Design Idea by Wallace Ly, National Semiconductor, Santa Clara, CA]
Circuit Drives 9 Volt Solenoids from 3 Volt Battery -  08/17/95 EDN-Design Ideas..... EDN is migrating links. This link is not verified.  Search the "title" EDN for new link.
Circuit Drives Latching Relays -  02/01/96 EDN-Design Ideas.....Figure 1 shows a low-parts-count circuit that can drive one- or two-coil latching relays. Latching relays are useful in sensitive analog designs. The 74ACT174 hex flip-flop has ample capability to drive the Aromat TQ2E series of latching relays. Both windings for the TQ2E-L2-5V two-coil relay are on the same magnetic element, so the windings' fields add. You..... [Design Idea by Roy McCammon, 3M Austin, TX]
Circuit drives mixed types and quantities of LEDs -  3-Oct-02 Issue of EDN  Portable systems often use LEDs of different colors and in varying quantities of each color. Some examples are white for the display backlight, green for keypad illumination, and red for power. Typically, the LEDs derive power from at least two power supplies  one for "standard" LEDs (red and green] and one for white LEDs..... [Design Idea by Mark Pearson, Maxim Integrated Products, Sunnyvale, CA]

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