[Techno-Frontier] TI Halves Laptop AC Adapter Size with New IC

Apr 16, 2009
Katsumi Yamashita, Nikkei Electronics
A 90W AC adapter for a notebook PC. It measures 85 x 60 x 11mm.
A 90W AC adapter for a notebook PC. It measures 85 x 60 x 11mm.
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The overview of the "ICC" control method. It stabilizes output voltage by providing many pulse signals under heavy load and few pulse signals under light load.
The overview of the "ICC" control method. It stabilizes output voltage by providing many pulse signals under heavy load and few pulse signals under light load.
[Click to enlarge image]
When the output is 88W, the conversion efficiency is 92.36%. The efficiency increases up to 93.1%.
When the output is 88W, the conversion efficiency is 92.36%. The efficiency increases up to 93.1%.
[Click to enlarge image]
The voltage waveform at the time of switching. By controlling cycles, a perfect zero voltage switching can be realized, according to TI.
The voltage waveform at the time of switching. By controlling cycles, a perfect zero voltage switching can be realized, according to TI.
[Click to enlarge image]

Texas Instruments Inc (TI) developed the power supply control IC "UCC29xx," which can reduce the volumes of AC adapters for notebook PCs to less than half those of existing AC adapters.

The company exhibited a prototype small AC adapter equipped with the new IC at Techno-Frontier 2009, which is taking place in Makuhari Messe, Chiba Prefecture, Japan, from April 15 to 17, 2009. The prototype measures 85 x 60 x 11mm and has a power output of 90W.

Moreover, equipped with a power-factor correction (PFC) circuit, the AC adapter has a power factor of 0.96. Its maximum power conversion efficiency is 93.1% when the the PFC circuit and the power conversion circuit are combined. TI has already begun volume production.

"We are currently shipping the IC only to a few companies in China," said an employee of Texas Instruments Japan Ltd. "We have not yet determined when we will release the product in Japan."

TI drastically reduced the size of the AC adapter by fully renewing the control method employed for the power supply control IC. The new method is neither PWM (pulse width modulation) nor PFM (pulse frequency modulation).

"We adopted a new control method called ICC," the employee said. "We cannot reveal the details because its patent is pending. But it is a control method focusing on cycles at the time of switching. By controlling each cycle, we realized a perfect zero voltage switching (ZVS) and enhanced the power conversion efficiency."

Furthermore, TI improved the PFC circuit, too. Normally, PFC circuits have a boost converter. With this method, it is possible to have a power factor infinitely close to 1. However, it decreases a power conversion efficiency and requires a high voltage (e.g. 600V) switching device in a later process.

Therefore, TI employed a step-down converter to prevent the conversion efficiency from decreasing and to use a low-voltage (200V or less) switching device.

"The cost of a 200V switching device is much lower than that of a 600V device, contributing to lowering the cost of an AC adapter," the employee said.

So far, step-down converters have not been mainstream because, with them, the power factor can be increased only to about 0.85. Though the details were not disclosed, TI claimed that it succeeded in enhancing the power factor to 0.96 by improving the circuit structure.

The prototype power supply control IC was developed n TI's research institute in Ireland.

"When it comes to power supply control ICs, they have always been PWM and PFM for the past two decades," the employee said. "To change this situation, our research institute in Ireland has been developing new control methods. The ICC control method is merely one of the first series of developments. We are engaged in developing other control methods and will announce a method that can further improve the power supply performance in the near future."