Aerosol generating device including vibrator and method of operating the same
According to an embodiment, an aerosol generating device includes a reservoir storing an aerosol generating material, a vibrator generating ultrasonic vibration to atomize the aerosol generating material into an aerosol, a drive circuit applying an alternating current (AC) voltage to the vibrator, a feedback circuit outputting a voltage proportional to a current supplied to the drive circuit, and a processor controlling a pulse width modulation (PWM) signal applied to the drive circuit, such that a value corresponding to the voltage is in a preset range defined by a first upper limit and a first lower limit.
1 . An aerosol generating device comprising:
a reservoir storing an aerosol generating material;
a vibrator configured to generate ultrasonic vibration to atomize the aerosol generating material into an aerosol;
a drive circuit configured to apply an alternating current (AC) voltage to the vibrator;
a feedback circuit configured to output a voltage proportional to a current supplied to the drive circuit; and
a processor configured to control a pulse width modulation (PWM) signal applied to the drive circuit, such that a value corresponding to the voltage is in a preset range defined by a first upper limit and a first lower limit,
wherein the feedback circuit comprises:
an operational amplifier comprising a non-inverting input terminal to which a drive voltage is applied, an inverting input terminal connected to an input terminal of the drive circuit, and an output terminal; and
a first resistor and a first capacitor which are connected in parallel between the non-inverting input terminal and the inverting input terminal, and
wherein the operational amplifier amplifies a voltage between the non-inverting input terminal and the inverting input terminal in a range acceptable by the processor and outputs the amplified voltage through the output terminal.
2 . The aerosol generating device of claim 1 , further comprising:
a sensor configured to detect a puff of a user,
wherein the processor applies the PWM signal to the drive circuit based on detection of a start of the puff and controls the PWM signal such that a time taken for the value corresponding to the voltage to reach the first upper limit is substantially constant for each puff of the user.
3 . The aerosol generating device of claim 1 , further comprising:
a cartridge including the reservoir and the vibrator; and
a main body including the drive circuit, the feedback circuit, and the processor, and detachably coupled to the cartridge,
wherein, based on the value corresponding to the voltage being less than a second lower limit that is lower than the first lower limit, the processor determines that the cartridge is not coupled to the main body.
4 . The aerosol generating device of claim 1 , wherein, based on the value corresponding to the voltage reaching a second upper limit greater than the first upper limit, the processor determines that the aerosol generating material is insufficient or that characteristics of the vibrator are changed.
5 . The aerosol generating device of claim 1 , wherein the first resistor has a resistance value small enough to transfer the drive voltage applied to the non-inverting input terminal to the input terminal of the drive circuit without a substantial voltage drop.
6 . The aerosol generating device of claim 1 , wherein the feedback circuit further comprises:
an RC filter including a second resistor and a second capacitor which are connected in series to the output terminal, and configured to provide an output voltage of the feedback circuit through the second capacitor.
7 . The aerosol generating device of claim 1 , wherein the processor acquires the value corresponding to the voltage by converting the voltage output from the feedback circuit into a digital value by using an analog-to-digital converter.
8 . The aerosol generating device of claim 1 , wherein the drive circuit comprises:
an input terminal to which a drive voltage is applied;
an inductor having a terminal connected to the input terminal;
a transistor connected to another terminal of the inductor and configured to perform switching such that a current flowing through the inductor flows to one of the vibrator and a ground; and
a power field-effect transistor (FET) configured to generate a switching voltage based on the PWM signal,
wherein the AC voltage is applied to the vibrator as the transistor performs the switching according to the switching voltage.