Electronic cigarettes are becoming a popular alternative to tobacco smoking because of the many advantages that they offer. The advantages of electronic cigarettes may include the absence of tar, odor, ash, pollution, and combustion by-products as compared, to traditional tobacco smoking,
However, there are still several factors holding users back from fully embracing this promising device. The addiction to smoking is not simply an addiction to nicotine; it is a habit that has many facets, including physiological, psychological, social, tactile, etc. Therefore, a large part of creating an ideal electronic cigarette is to provide a positive user experience which is increasingly similar to tobacco smoking. This means that the electronic cigarette has to require minimal priming, produce consistent “smoke” volume, and always be available with reliable and extended battery life.
An electronic cigarette typically comprises a battery, an atomizer, a container having smoke juice, and a power control circuit. The battery is used to power the circuit and the atomizer, where the atomizer heats the smoke juice to create smoke to vapor, which is inhaled by a user. “Smoke” volume is dependent on the power output of the device, which is a function of voltage squared, divided by the resistance. Accordingly, in the usual arrangement, battery output voltage is directly proportional to “smoke” volume.
Earlier versions of electronic cigarettes often failed to provide positive user experience. Most electronic cigarettes have unregulated lithium-polymer battery cells that start off with a high voltage of about 4.2 volts, and drops gradually to about 3.0 volts as the cell's charge is depleted. This arrangement relies on the battery's natural power degradation to regulate the production of smoke. Thus, as the battery cell is depleted, voltage in the battery naturally decreases and the “smoke” volume noticeably drops, making for an inconsistent smoking experience.
Another disadvantage with these unregulated electronic cigarettes is that the power supplied during power-up or priming” are very high, tending to produce excessive heat. After priming, the battery continues operating at its maximum output (minus any power loss due to the priming stage) and the excessive heat produced does not have enough time to dissipate, resulting in high internal and external temperatures on the housing of the cartridge. It often happens that after a dozen or so puffs, the smoke juice and materials surrounding the heating element start to overheat and acquire an unpleasant burning smell. More concerning, the atomizer housing becomes so hot that it can burn the fingers and/or lips of the user.
Newer versions of electronic cigarettes often incorporate a circuit to reduce output power at specific points during operation by regulating the output voltage of the battery at all times during operation. The purpose of regulation is to limit the output voltage of the battery throughout the smoking cycle to the same voltage level that the battery will have at its depleted state (i.e., at approximately 3 volts), thereby maintaining a uniform lower output voltage. This is supposed to ensure that the user has a uniform experience from the first puff to the last, with no degradation in “smoke” volume as the battery discharges, while conserving energy and extending battery life.
Unfortunately, there is a downside to this approach. In order for an atomizer to produce enough “smoke” volume, it needs to be sufficiently warmed up, which is hard to achieve in a short period of time when the battery output voltage is initially limited by the regulating circuit. A regulated voltage arrangement therefore requires more time during the priming stage in order to warm up the atomizer, and, if the user takes a puff before the atomizer is completely primed, it leads to less smoke/vapor production at the beginning, thereby impairing user experience because the initial puffs are not satisfying. Moreover, these initial user puffs essentially act as the “priming” for the device. For a first-time user of the electronic cigarette, the first few weak puffs—with little “smoke” volume—could be a disappointing experience, causing him to reject the product. It simply is not desirable for the user to be responsible for priming the device, as it can be a nuisance. Therefore, neither the unregulated system, nor the fully regulated system is a sufficient solution to ensure an optimal smoking experience and long battery life. Accordingly, there is a need in the art for a more dynamic or variable power control program that can provide a better smoking experience for the user.