|CAP-XX Brite Flash Power Architecture for Camphones|
Mark Peters : March 11th 2006 - 17:40 CET
CAP-XX Brite Flash Power Architecture for Camera phones CAP-XX announced its BriteFlash power architecture to provide LED flash camera phones with enough light to produce high-resolution images. Some phone manufacturers have experimented with long flash exposure times to compensate for low-light problems, which then result in blurry digital photographs. CAP-XX's BriteFlash architecture provides enough flash power to eliminate both dark and blurry digital photos using high-capacitance (0.4 to 1 farad), low equivalent-series-resistance (less than 100 milliohms), thin (1 to 3 millimeters) prismatic supercapacitors to support a battery and deliver the pulse power to drive an LED to full light intensity. |
High-intensity flash for better photos|
CAP-XX also developed the power architecture that optimizes a super-capacitor to power flash LEDs. "Greater than two megapixel camera phones require a high-intensity flash in medium to low light conditions to ensure good pictures," said Anthony Kongats, CEO of CAP-XX. "Some solutions are available but lack adequate power to produce quality photos in all light conditions. Our BriteFlash power architecture completes the equation with the power to drive today's LEDs."
CAP-XX Brite Flash Power
Today's high-power white LEDs require a higher voltage than a Li-ion battery can supply, so power integrated circuit (IC) suppliers have developed special-purpose DC/DC and charge pump ICs to drive these LEDs. However, these new LEDs need up to 400% more power than a battery can provide to achieve full light intensity. CAP-XX supercapacitors can deliver this pulse power. CAP-XX has developed reference designs using flash drivers that offer multiple design options.
Digital camera Xenon flash solution
The CAP-XX BriteFlash power architecture is similar to a Xenon flash solution used in digital cameras today, where a low-current charge pump (boost converter) charges the supercapacitor to 5.5 volts then the supercapacitor drives the LED at very high current for the flash pulse. CAP-XX's supercapacitor-based solution, however, delivers more light energy (flash power x flash duration) and has a much thinner form factor than the Xenon one. Designers are forced to choose thinner, hence reduced-capacitance 330-volt cylindrical electrolytic storage capacitors necessary in Xenon designs to fit them in space-constrained camera phones. These reduced-capacitance electrolytic capacitors, which are still bulky at 6 to 10 mm, reduce the light energy the flash can provide.
BriteFlash solutions - Technical Specifications
Two BriteFlash solutions described here allow tradeoffs between the flash distances needed to take high-resolution photos, and the cost to implement them. Solution 2 yields an effective flash up to 1.5 meters versus the 3 meters achieved with the maximum power in Solution 1.
BriteFlash Solution 1 : Offers maximum power and supports a flash photo up to 3 meters, compared to 1 meter or less for camera phones without a supercapacitor in low lighting. A dual-cell supercapacitor such as a 0.55-farad, 50-milliohm CAP-XX GS206 delivers over 25 watts to the LEDs versus 2 to 4 watts without a supercapacitor. A supercapacitor also eliminates the need to shut down the rest of the phone because the battery isn't needed to supply any current during the flash, leaving it free to supply other power needs such as OLED display or RF transmission. The battery only needs to provide a low-charging current of 250 mA to the supercapacitor to support a recovery time between flashes of approximately 2 seconds. This is less time than the LED needs for thermal recovery between flashes. The low-charging current allows designers to use lower-cost, smaller boost converters or charge pumps because the supercapacitor supplies the peak current. Without a supercapacitor, the boost converter has to be sized for peak flash current. The CAP-XX BriteFlash reference designs show how to optimize the power subsystem with a supercapacitor.
BriteFlash Solution 2 : Supports a flash photo up to 1.5 meters using a single-cell, lower-cost supercapacitor such as a CAP-XX GW101, which is half the volume of the GS206 device. This solution increases the LED current by approximately 40%, which allows the 50% increase in flash distance. The supercapacitor is pre-charged prior to a flash pulse and the battery only needs to provide a relatively low-charging current of a few 100mA allowing an even smaller and lower-cost charge pump than Solution 1.
CAP-XX Feasibility Experiment
To demonstrate the increased flash power and ease of design-in, CAP-XX engineers retrofitted several models of industry-leading camera phones with the BriteFlash solution. In one example, CAP-XX placed a dual-cell supercapacitor, replaced existing LEDs with 4 high-powered LEDs that can each handle a peak pulse current of 1A, then put the phone together again with no change in external appearance. The original phone delivered 1 watt of flash power for 160 milliseconds while the CAP-XX-modified phone delivered 15 watts for the same amount of time.
CAP-XX BriteFlash - Price and Availability
The total cost of the CAP-XX BriteFlash solution is US $4 to $5 including the LEDs, supercapacitors and circuitry. The supercapacitor alone costs $1.50 for the single-cell solution and $2.50 for the dual-cell one in quantities of 10,000 or more. CAP-XX is working with flash/LED driver suppliers to develop supercapacitor-optimized charge pump LED drivers to further increase camera phone power subsystem integration and reduce costs.
CAP-XX Inc. develops and manufactures supercapacitors. Supercapacitors can bridge the gap between capacitors and batteries, delivering higher power bursts than batteries and storing more energy than traditional capacitors. CAP-XX has been recognized for its nanotechnology process for producing high capacitance, low equivalent-series-resistance supercapacitors that deliver the industry's highest energy and power densities in the smallest packages. These energy-storage devices enable manufacturers to make smaller, thinner, longer-running portable electronics such as cell phones, PDAs, medical devices, AMRs, and notebooks. The private company is based in Sydney, Australia, has additional production facilities in Malaysia, and sales offices in South Carolina and Texas, USA & Taipei, Taiwan.