Aerosol generating device with air flow detection

1. A handheld electrical smoking device configured for user inhalation of a generated aerosol, the handheld electrical smoking device comprising:

a heater element configured to heat an aerosol-forming substrate over a period containing a plurality of user puffs on a mouthpiece;

a power source connected to the heater element; and

a controller connected to the heater element and to the power source, wherein the controller is configured to:

control power supplied to the heater element from the power source to raise a temperature of the heater element to a target temperature and subsequently to reduce power supplied to the heater element to maintain the heater element at the target temperature,

after the temperature of the heater element has reached the target temperature, monitor changes in the temperature of the heater element, or changes in the power supplied to the heater element, that are caused by cooling of the heater element by air flow from each puff of the plurality of puffs on the mouthpiece to detect a change in the air flow past the heater element indicative of the user inhalation during a respective puff, and

reduce the target temperature when the change in airflow past the heater is detected.

2. The handheld electrical smoking device according to claim 1 , wherein the controller is configured to monitor a difference between the temperature of the heater element and the target temperature to detect the change in air flow past the heater element indicative of the user inhalation.

3. The handheld electrical smoking device according to claim 2 , wherein the controller is configured to monitor if the difference between the temperature of the heater element and the target temperature exceeds a threshold to detect the change in air flow past the heater element indicative of the user inhalation.

4. The handheld electrical smoking device according to claim 3 , wherein the controller is configured to monitor whether the difference between the temperature of the heater element and the target temperature exceeds the threshold for a predetermined time period or for a predetermined number of measurement cycles to detect the change in air flow past the heater element indicative of the user inhalation.

5. The handheld electrical smoking device according to claim 1 , wherein the controller is configured to monitor a difference between the power supplied to the heater element and an expected power level.

6. The handheld electrical smoking device according to claim 1 , wherein the controller is configured to compare a rate of change of the temperature or a rate of change of the power supplied with a threshold level.

7. The handheld electrical smoking device according to claim 1 , wherein the controller is configured to adjust the power supplied to the heater element when the change in airflow past the heater element is detected.

8. The handheld electrical smoking device according to claim 1 , wherein the controller is configured to monitor the temperature of the heater element based on a measure of an electrical resistance of the heater element.

9. The handheld electrical smoking device according to claim 1 , wherein

the device includes a data output means, and

the controller is configured to provide a record of each detected change in air flow past the heater element indicative of the user inhalation to the data output means.

10. The handheld electrical smoking device according to claim 1 , wherein

the aerosol-forming substrate is contained in a smoking article, and

during operation, the smoking article is completely contained within the electrical smoking device.

11. The handheld electrical smoking device according to claim 1 , wherein the electrical smoking device is a handheld device.

12. A method for detecting a user inhalation through a handheld electrically heated smoking device, the device comprising a heater element configured to heat an aerosol-forming substrate over a period containing a plurality of user puffs on a mouthpiece, and a power supply for supplying power to the heater element, the method comprising:

controlling power supplied to the heater element from the power source to raise a temperature of the heater element to a target temperature and subsequently reducing power supplied to the heater element to maintain the temperature of the heater element at the target temperature;

after the temperature of the heater element has reached the target temperature, monitoring changes in the temperature of the heater element, or changes in the power supplied to the heater element, that are caused by cooling of the heater element by air flow from each puff of the plurality of puffs on the mouthpiece to detect a change in the air flow past the heater element indicative of the user inhalation during a respective puff, and

reducing the target temperature when the change in airflow past the heater is detected.

13. The method according to claim 12 , wherein the step of monitoring comprises monitoring a difference between the temperature of the heater element and the target temperature to detect the change in air flow past the heater element indicative of the user inhalation.

14. The method according to claim 12 , wherein the aerosol-forming substrate is contained in a smoking article.

15. The method according to claim 14 , wherein the smoking article is completely contained within the electrical smoking device.

16. The method according to claim 12 , wherein the aerosol-forming substrate is a solid aerosol-forming substrate.