TASKLED - Smart LED drivers
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Discontinued Product, use h6Flex instead
hipFlex:
25 Jan 2010: New UI-UNI2 firmware released. Instruction manual is here hipflex V2 manual.
Mechanical drawing for V1.1 and V1.1A PCB is here (pdf).
NOTE: hipFlex drivers shipped prior to 19 Mar 2009 have a firmware bug that limits voltage sensing to 16.2V. Do not enter a value larger than 16.2V into the menu system, otherwise the entry will not function correctly. This only effects voltage monitoring for battery packs >16.2V.
The picture below shows the bottom view of hipFlex. The exposed silvery areas on the bottom of the PCB is a direct thermal interface to the bottom of the power devices (on the component side of the PCB). If the power dissipation of the hipFlex board exceeds about 1W it is recommended to affix a heatsink or copper tab to a heatsink to the exposed areas using the supplied thermal pad material. The exposed areas are at various potentials and must NOT be electrically shorted or connected to the heatsink.
Two mounting holes are provided to enable the driver to be clamped down to a heatsink. The supplied thermal pad material is nominally 1mm thick and will conform to the heatsink and PCB surfaces to provide an excellent thermal path.
The thermal pad material (TGF120K) specifications can be found in the datasheet a copy of which is available here. The TGF120K material is more than adequate to handle the heat transfer from the hipFlex to the heatsink and much more cost effective than the higher rated materials in the datasheet.
Hookup information:
The circuitry (all surface mount) fits neatly on a 1.40" diameter PCB on the top side. The maximum board+component thickness of the driver is 0.35" where the inductor (L1) is situated. Note, the thermal pad material is nominally 0.039" thick, so total thickness would be 0.35" + 0.039" = 0.389".
The IN+ hole (bottom right corner) and IN- (middle right) are the input power connections to hipFlex. 24V MAXIMUM input voltage.
Input operating voltage range is 7V to 21V. 4 li-ion maximum, 5 li-ion when fully charged will damage the hipflex.
hipFlex is capable (but not guaranteed) of running as low as 4.5V IF the LED current is configured to <= 1.4A.
The LED+ hole (top left) and LED- (middle right) are the output power connections from hipFlex to the LED load. LED- is NOT electrically the same as IN-.
The STAT pin can be wired the the cathode of a status LED. The anode of the LED should be wired to a current limiting resistor and then to IN+. It is the user's responsibility to calculate the necessary resistor value to limit the current to the LED. The resistor value can be calculated using the following equation.
Resistor_value = (VIN - STAT_LED_Vf) / STAT_LED_CURRENT
As an example, for 10mA to a Red LED with Vf of 2.5V and running from 16V battery:
Resistor_value = (16 - 2.5) / 0.010 = 1350 ohms.
The SWA hole is one side of an external momentary action switch. The other side of the switch must be wired to SWB (which is electrically the same as IN-). The switch only switches a control signal and carries at most 350microamps.
Note: it is recommended to keep the maximum wire length between the switch and hipFlex less than around 8 " (20cm). Having wire leads that are too long can cause the wires to act as an antenna and cause hipFlex to respond irregularly or turn on/off by itself.
Note, hipFlex is a Buck regulator (step down), so input voltage must be greater than the output voltage to ensure hipFlex remains in regulation. If the input voltage drops within 0.5V of the LED Vf (at the specified current) hipFlex will no longer regulate and the output voltage will drop and output current will also drop.
Some Efficiency Measurements:
Below are some example measurements with 1, 2 and 3 P7 LEDs wired in series.
As can be seen in the above curves, efficiency drops as the difference between input voltage and total Vf increases. Also, efficiency drops with lower output voltage.
Adequate heatsinking is essential when running at high output power.
To determine the heat being dissipated on the hipFlex driver, calculate the output power. Use the chart above to approximate the efficiency that the driver will be running at.
Lets assume 3 LEDs running at a nominal 2.8A from a 14.4V li-ion battery pack. From above we have the following:
Output_power = 3 x 3.5V x 2.8A= 29.4 Watts.
Efficiency is 93%, so losses in hipFlex are 7%.
Power dissipated as heat in hipFlex is 29.4 x 0.07 = 2.1Watts
This will require heatsinking via the thermal interface pad on the bottom of hipFlex.
As power being dissipated increases beyond 1W the thermal path to the heatsink becomes critical to reliable operation. Most of the heat being dissipated in the driver is from the power FET, Q2 and the inductor, L1. The thermal interface (silver area on the bottom of the PCB) is tied directly to the bottom of Q2 and L1 using thermal vias. Mounting an adequate heatsink with the supplied thermal pad material is recommended and will allow hipFlex to be run at high power reliably.
Tests performed with 5 Seoul P7 LEDs driven at 2.8A via hipFlex show that the hipFLEX PCB temperature will be at most 15C hotter than the heatsink when used with the provided thermal pad material. These results were with hipFlex just resting against the thermal pad material (no pressure applied), so good performance without extra clamping force.
Potting Warning:
Areas of the circuitry on hipFlex utilize high impedance paths and if potting (not required) is to be utilized, the user must ensure than the compound is non-conductive and non-capacitive (e.g. Arctic Alumina - NOT Arctic Silver) otherwise correct operation may be compromised. The same consideration is present if using thermal epoxy is used to mount the hipFlex driver to a heatsink.
Rather than potting, it is recommended to use the thermal interface pad on hipFlex to connect to a heatsink using the supplied thermal pad material. NOTE, the thermal interface area on hipFlex is NOT at ground potential.
Soldering to the thermal interface pad is NOT recommended.
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