WO2023105181A1

WO2023105181A1 - Haircare appliance

Info

Publication number: WO2023105181A1
Application number: PCT/GB2022/052605
Authority: WO
Inventors: Li NIU; Zhiyang PAN; Xinyi Li
Original assignee: Dyson Technology Limited
Priority date: 2021-12-08
Filing date: 2022-10-13
Publication date: 2023-06-15
Also published as: GB2613598A; GB202117712D0

Abstract

A haircare appliance comprising drive circuitry, a controller in communication with the drive circuitry for controlling a drive current output by the drive circuitry, and a temperature sensor for supplying a temperature signal to the controller. The temperature signal is indicative of a temperature of an electronic circuit within the haircare appliance. The controller is configured to estimate an ambient temperature at least partly based on the temperature signal, and to prevent the drive circuitry from outputting the drive current when the estimated ambient temperature is lower than an ambient temperature threshold.

Description

HAIRCARE APPLIANCE

FIELD OF INVENTION

The present invention relates to a haircare appliance.

BACKGROUND

Haircare appliances may be used to treat or style hair. Some haircare appliances may treat or style hair using heat and/or airflow. Such haircare appliances are typically held by a user and moved relative to the hair to obtain desired treatment or styling.

SUMMARY OF INVENTION

According to a first aspect, there is provided a haircare appliance comprising: drive circuitry; a controller in communication with the drive circuitry, for controlling a drive current output by the drive circuitry; and a temperature sensor for supplying a temperature signal to the controller, the temperature signal being indicative of a temperature of an electronic circuit within the haircare appliance; the controller being configured to estimate an ambient temperature at least partly based on the temperature signal, and to prevent the drive circuitry from outputting the drive current when the estimated ambient temperature is lower than an ambient temperature threshold.

Estimating and using ambient temperature in this indirect manner may provide an improved or at least alternative way of protecting a haircare appliance.

The electronic circuit may comprise a processor, and the temperature sensor may be configured to sense the processor temperature. Processor temperature may provide a useful, or at least alternative, basis for estimating an ambient temperature.

The temperature sensor may be integrated with the processor. A processor-integrated temperature sensor may provide a compact and/or cost effective way of estimating ambient temperature.

The processor may form part of the controller. The controller may be configured to estimate the ambient temperature at least partly based on the drive current or a power related to the drive current. This may offer improved accuracy and/or responsiveness.

The drive circuitry may comprise a motor driver, and the haircare appliance may comprise an electric motor configured to be driven by drive current from the motor driver.

The drive circuitry may comprise a heater driver, and the haircare appliance may comprise a heating element configured to be driven by drive current from the heater driver.

The controller may be configured to estimate the ambient temperature based at least partly on multiple temperature signal values. Using multiple temperature signals may offer a more accurate or responsive ambient temperature estimate.

The controller may be configured to estimate the ambient temperature based at least partly on differential temperature values calculated based on changes in the temperature signal values overtime. Using differential temperature values in this manner may allow the controller to better account for thermal lag.

The haircare appliance may comprise a first housing within which is disposed at least one heating element, and a second housing connected to the first housing, wherein the temperature sensor is disposed within the second housing.

The first housing may be connected to the second housing by a power and/or communications cable.

The first housing may comprise the electric motor and the second housing may comprise the motor driver.

The controller may be configured to estimate the ambient temperature at least partly based on the drive current output by the motor driver, or a power related to the drive current output by the motor driver.

According to a second aspect, there is provided a method of controlling a haircare appliance, the method comprising: repeatedly sensing a temperature of an electronic circuit within the haircare appliance; estimating an ambient temperature at least partly based on the sensed temperature; and preventing drive circuitry of the haircare appliance from outputting a drive current when the estimated ambient temperature is lower than an ambient temperature threshold.

The electronic circuit may comprise a processor, and sensing the temperature may comprise sensing the processor temperature.

The temperature sensor may be integrated with the processor, and sensing the processor temperature may comprise reading a temperature value from a memory within, or associated with, the processor.

The method may comprise estimating the ambient temperature at least partly based on a drive current output by the drive circuitry.

The drive circuitry may comprise a motor driver, the haircare appliance may comprise an electric motor configured to be driven by the motor driver, and the method may comprise estimating the ambient temperature at least partly based on the drive current output by the motor driver.

The method may comprise estimating the ambient temperature based at least partly on multiple temperature signal values.

The method may comprise estimating the ambient temperature based at least partly on differential temperature values calculated based on changes in the temperature signal over time.

The haircare appliance may comprise: a first housing within which is disposed at least one heating element or an electric motor; a second housing connected to the first housing, the first temperature sensor being disposed in the second housing.

The electric motor may be disposed within the first housing, the drive circuitry may comprise a motor driver disposed within the second housing, and the motor driver may be configured to provide a drive current to drive the electric motor. Optional features of aspects of the present invention may be equally applied to other aspects of the present invention, where appropriate.

BRIEF DESCRIPTION OF DRAWINGS

Aspects, implementations and alternatives will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic longitudinal section through a haircare appliance in the form of a hair straightener;

Figure 2 is the schematic longitudinal section of Figure 1, showing airflow when the hair straightener is operating;

Figure 3 is a schematic longitudinal section of an alternative haircare appliance in the form of a hair straightener;

Figure 4 is schematic longitudinal section an alternative haircare appliance in the form of a hairdryer; and

Figure 5 is a flowchart showing a method of controlling a haircare appliance.

DETAILED DESCRIPTION

Referring to the drawings, and Figure 1 in particular, there is shown a haircare appliance in the form of a hair straightener 100. Hair straightener 100 has a housing 102 within which is disposed an airflow generator in the form of an axial impeller 104 that is driven by an electric motor 106.

Hair straightener 100 includes a first arm 120 and a second arm 122. First and second arms 120 and 122 are pivotably connected to each other via a hinge mechanism (not shown), allowing hair to be captured between them when hair straightener 100 is in use.

First arm 120 includes a plenum 124, within which is disposed a resistive heating element 108. Heating element 108 extends axially through first arm 120, parallel to an axial slot 126 formed in first arm 120. Second arm 122 includes a plenum 128, a heating element 130, and a slot 142 arranged in a similar fashion to the corresponding components of first arm 120. First and second plenums 124 and 128 are located downstream of impeller 104.

Motor 106 is electrically connected to, and driven by, a first drive circuit in the form of a motor driver 110. Heating element 108 is electrically connected to, and driven by, a second drive circuit in the form of a heater driver 112. Although not shown in Figure 1 for clarity, motor driver 110 and heater drive 112 are both supplied with power from an AC power supply (such as mains power, not shown). In other implementations, a DC power supply (such as a battery or an AC to DC converter) may power motor driver 110 and/or heater driver 112.

Motor driver 110 and heater driver 112 are connected to, and controlled by, a controller 114. Controller 114 may take the form of a microcontroller 116 comprising a processor, memory, and I/O circuitry, as will be understood by the skilled person.

Controller 114 also comprises a temperature sensor 118. In the example illustrated in Figure 1, temperature sensor 118 is integrated with microcontroller 116, in a manner known to those skilled in the art. Temperature sensor 118 outputs a temperature signal that is indicative of a temperature of microcontroller 116. Depending upon the type of temperature sensor, the temperature signal can take the form of, for example, a voltage that varies with temperature. The voltage may be converted to a temperature value using, for example, an analog -to-digital converter (not shown). The temperature value may be stored in a register (not shown), for example.

The skilled person will appreciate that the temperature sensor can take any suitable form. For example, rather than outputting a voltage that is converted to a temperature, the temperature sensor can directly output an actual (i.e., numerical) temperature that can be accessed by microcontroller 116. In addition, the temperature sensor need not be part of microcontroller 116, or even part of controller 114. Depending upon the requirements of any particular implementation, the temperature sensor can be positioned and configured to sense a temperature of any electronic circuit within the haircare appliance . In this context, “electronic circuit" means a circuit or circuit component other than a heating element designed to heat a user’s hair, either directly via one or more plates or other elements, or indirectly via heating air that is intended to be blown onto a user’s hair. Such circuits and circuit components can include circuits that are not directly heated by any heating element within the haircare appliance. In at least some implementations (and as described in more detail below), the “electronic circuit” means a circuit or circuit component in a housing separate to a housing within which a motor and/or a heating element of the haircare appliance are disposed.

Controller 114 is connected with a user interface 132. User interface 132 can include, for example, user input controls, such as one or more buttons, sliders, or touchscreens, and user feedback elements, such as one or more display screens or LEDs. Using user interface 132, a user can, for example, turn hair straightener 100 on or off, change modes, and adjust settings such as temperature and airflow speed.

As shown in Figure 2, when hair straightener 100 is turned on by way of a user interacting with user interface 132, controller 114 controls motor driver 110 to in turn control a drive current to motor 106, and controls heater drive 112 to control a drive current to heating elements 108 and 130, in accordance with a mode and other settings selected by a user. As shown by arrows 136, air is drawn into hair straightener 100 by impeller 104, pushed into plenums 124 and 128, heated by heating elements 108 and 130, and output via slots 126 and 140. By pinching a tress of hair in the gap between first 120 and second arm 122 and then drawing the tress through the gap, hair may be straightened or otherwise styled.

Microcontroller 116 is configured to estimate an ambient temperature at least partly based on the temperature signal. This may be achieved in any suitable manner. For example, the ambient temperature may be estimated by applying a proportional correction factor, and/or a constant offset, to account for the fact that the electronic circuit for which the temperature is sensed may be warmer than associated with a typical ambient temperature.

For example, an offset of, say, 10°C may be applied to the current temperature of the microcontroller. That is, if the microcontroller temperature is 35°C, the 10°C offset would result in an ambient temperature estimate of 25°C (= 35°C - 10°C).

Alternatively, using a proportional correction factor of, say, 0.75, then if the microcontroller temperature is 35 °C, the proportional correction factor would result in an ambient temperature estimate of 26.25°C (= 0.75 * 35°C).

These and other factors can be used in combination with each other, as will be understood by the skilled person.

Optionally, the controller may filter the temperature signal (or one or more values derived from the temperature signal) as part of estimating the ambient temperature. For example, the temperature signal may be repeatedly sampled, and the samples low-pass filtered to remove the impact of short-term fluctuations. For example, a moving average, such as a simple moving average or a weighted moving average, may be applied to the samples. The number of samples to be averaged and the averaging method may be selected based on empirical testing and/or modelling. A scaling factor may optionally be applied to the result of the fdtering, similarly based on empirical testing and/or modelling. The result may then be used as part of estimating the ambient temperature.

Optionally, the controller may use one or more differential terms based on the temperature signal (or one or more values derived from the temperature signal) as part of estimating the ambient temperature. For example, the temperature signal may be repeatedly sampled. A differential term may then be determined based on a difference between nearby or adjacent samples. A scaling factor may optionally be applied to the differential term, based on empirical testing and/or modelling. The result may then be used as part of estimating the ambient temperature.

Optionally, the controller may be configured to estimate the ambient temperature at least partly based on a drive current or power output. For example, controller 114 controls motor driver 110 and heater driver 112, based on a combination of user-selected mode and settings, and feedback from other sensors (not shown) within hair straightener 100.

For example, a change in current/power supplied by motor driver 110 and/or heater driver 112 may cause a corresponding change in temperature in the circuitry of motor driver 110 and/or heater driver 112. When motor driver 110 and/or heater driver 112 are located near temperature sensor 118, the accuracy with which the temperature is sensed may be affected. Controller 114 can therefore estimate the ambient temperature by at least partly taking into account the drive current, or a power related to the drive current.

For example, the average or instantaneous current or power being supplied to fan motor 106 and/or heater elements 108 and 130 (by motor driver 110 and/or heater driver 112) can be determined. A scaling factor may optionally be applied to the average or instantaneous current or power, based on empirical testing and/or modelling. The result may then be used as a correction factor when estimating the ambient temperature, to take into account the heat produced in motor driver 110 and/or heater driver 112.

A linear regression model may be used to estimate the ambient temperature based on whichever inputs are being employed. For example, if the inputs include a temperature (TCPU) of microcontroller 116 (based on the temperature signal generated by temperature sensor 118), a differential term (Tcpu diff) based on two temperature values of microcontroller 116, and a power (Pmotor being output by motor 106, then an example of a regression model for estimating ambient temperature is: y = a +b * TCPU + c * Tcpu dtff + d * Pmotor where: y = estimated ambient temperature

TCPU = temperature of microcontroller 116

Tcpu_diff = differential term Tcpu+dijj(k) = T_Cpu(k) - T_Cpu(k-l)) Pmotor = power being output by motor a, b, c, and d = constants derived by modelling and/or testing.

As explained above, T PU can be calculated as a moving average, which may reduce the impact of noise . For example, a moving average may be calculated with a window size of 4096 samples, although any suitable window size may be used.

The thermal mass of microcontroller 106, and other components and structure around it, means that the temperature of microcontroller 106 will not respond immediately to changes in operating mode, as well as to ambient temperature changes. The TCPU iff term can be used to at least partly compensate for this lag in response. Although TCPU _^is described in terms of adjacent pairs of temperature samples, the skilled person will appreciate that other samples within a sequence of temperature samples may be the subject of a differential term.

Depending upon the haircare appliance, Pmotor can be based on a current power value, which in turn may be based on the current or power being supplied to motor 106, or may be inferred from the mode in which the device is being used. In terms of the regression model, Pmotor takes into consideration the abrupt change that may take place when there is a transition between different operating modes involving different motor speeds/power.

Parameters a, b, c, and d can be derived in any suitable manner, including modelling and/or testing. For example, parameters may be generated by training data during operation of the haircare appliance in a variety of test scenarios. For example, in one test scenario, the haircare appliance is operated in a high airflow, high heat mode, with environmental ambient temperature changing from -10°C to 20°C then back to -10°C. The ambient temperature changes when CPU temperature saturates and reaches steady state. A second test scenario may involve the same sequence of ambient temperature changes, but with the haircare appliance not running throughout.

A third test scenario may involve maintaining ambient temperature at a constant -5°C. The mode of the haircare appliance is initially set to low speed airflow without heat, and then the haircare appliance is turned off. Then a high speed airflow without heat mode is selected, and then the haircare appliance is turned off. Each change of mode (or turn on/off) takes place when the temperature of temperature sensor 118 saturates and reaches steady state.

The skilled person will appreciate that model parameters (such as a, b, c, and d in the described implementation) can be determined using any other suitable training regime.

Returning to hair straightener 100, at mode transition (that is, when the user selects a mode having a significant change in motor speed, and therefore drive current), the corresponding spike in P_motor can cause a sharp increase in the estimated ambient temperature y based on the equation above . To mitigate the effect of such an increase, a “blanking time” may be implemented upon a change of mode. For example, the value of v at the time of a mode change may be frozen for several seconds. Optionally, the blanking time may equate to the period of time over which any moving average is applied to TCPU. In an example, the length of the moving average window, and of the blanking time, is 15 seconds, although the skilled person will appreciate that any other suitable window length and/or blanking period may be employed depending upon the implementation.

The skilled person will appreciate that the equation above is only one example of a potential model for estimating an ambient temperature y.

Once an ambient temperature has been estimated, controller 114 determines whether the estimated ambient temperature is lower than an ambient temperature threshold. The ambient temperature threshold may be a hard-coded temperature value. For example, the ambient temperature threshold may be a temperature value representing a point below which an estimated ambient temperature raises a condensation risk to an unacceptable level, or increases the risk of thermal damage to one or more components, such as the heater, to an unacceptable level.

For example, it may be determined that a condensation risk exists for an actual ambient temperature below, say, about 5°C. The ambient temperature threshold may therefore be set at 5°C. In an alternative example, the risk of crack damage to a ceramic substrate of a heater at turn-on may increase to an unacceptable level for an actual ambient temperature below, say, about 2°. The ambient temperature threshold may therefore be set at 2°C. Where multiple thresholds are involved, the most conservative threshold may be applied.

Optionally, the ambient temperature threshold may be selected to take into account any expected errors in estimated ambient temp just. For example, if the estimated ambient temperature is expected to have an error of +/-2°C, and the actual threshold is 5 °C, the ambient temperature threshold may be set at 7°C, to account for the fact that the estimated ambient temperature may be in error by up to 2°C.

Optionally, the ambient temperature threshold may be based at least in part on the humidity of the environment within which the haircare appliance is located. For example, in a relatively high humidity environment, a higher temperature threshold may be used, due to the increased condensation risk. Humidity may be estimated by a humidity sensor (not shown).

If the estimated temperature is below the threshold, then either or both of the drive circuits are prevented from outputting the drive current. For example, controller 114 may be programmed and configured such that it will only provide drive control signals to heater driver 112 if the estimated temperate exceeds the threshold. This prevents heating elements 108 and 130 from being operated in the event that the ambient temperature is too low, which may involved an increased risk of condensation. Optionally, other components may also be prevented from operating if the estimated temperature is below the threshold. For example, controller 114 may be programmed and configured such that it will only provide drive control signals to motor driver 110 if the estimated temperate exceeds the threshold.

Alternatively, if the estimated temperature is below the threshold, then the drive circuits may be prevented from outputting drive current by shutting down the haircare appliance, or placing it into a standby mode. This may be done by, for example, shutting down controller 114 or placing it into a standby mode. The shut-down or standby may be timed, to prevent a user from attempting to turn the haircare appliance on again too quickly following a determination that the estimated temperature is below the threshold.

Optionally, the haircare appliance may provide information to the user by way of user interface 132, indicating that the ambient temperature is too low. This information may be provided by way of relatively simple feedback, such as flashing LEDs or indicators on a display, or an audible beep or other sound. Alternatively, an explanatory message may be displayed on a display screen if available, and/or audibly played by a loudspeaker.

The skilled person will appreciate that the drive circuitry may be prevented from outputting the drive current in other ways. For example, a relay or other form of switch (not shown) may be placed in series between heater driver 112 and heating elements 108 and 130, the switch only being closed to allow the heating elements 108 and 130 to be heated when the estimated ambient temperature is higher than an ambient temperature threshold. A relay or other form of switch (not shown) may be placed to control the supply of power to heater driver 112, or to any other circuit or circuit component that must be powered in order for drive current to be supplied by either or both drive circuits.

Turning to Figure 3, there is shown a further haircare appliance in the form of a hair straightener 200. Hair straightener 200 shares many features and components with hair straightener 100 of Figures 1 and 2, and the same reference signs are used to indicate corresponding features in hair straightener 100 and hair straightener 200.

One difference between hair straightener 200 and hair straightener 100 is that hair straightener 200 includes a second housing in the form of a control box 134. Control box 134 includes controller 114, including microcontroller 116 and temperature sensor 118. A power cord 138 is connected to control box 134 to provide AC power, which is converted to DC by a power supply (not shown) to power components such as controller 114.

Control box 134 is connected to housing 102 by way of a flexible cable 140. Cable 140 includes one or more wires or connectors for passing control signals from controller 114 to components within housing 102, such as heater driver 112, as well as one or more wires or connectors for passing signals between user interface 132 and controller 114. Cable 140 may also include one or more wires for passing AC and/or DC power from control box 134 to components within housing 102. Although described as having a power cord 138 connectable to an AC power supply, the skilled person will appreciate that hair straightener 200 may alternatively be battery-powered.

Hair straightener 200 operates in substantially the same manner as hair straightener 100. However, temperature sensor 118 is in the same box (i.e., control box 134) as motor driver 112, separate from housing 102. In this case, it may be particularly useful to use the instantaneous or filtered motor drive current or power as part of the equation used to calculate the ambient temperature, due to the proximity of the motor driver 112 to temperature sensor 118. This may more particularly be the case when control box 134 is unvented, which reduces the influence of ambient air on the temperature sensed by temperature sensor 118.

As described above, the temperature in the circuitry of motor driver 110 is a function of the current/power it is supplying. Heat from motor driver 110 may therefore affect the temperature sensed by temperature sensor 118. Controller 114 can therefore estimate the ambient temperature by at least partly taking into account the drive current, or a power related to the drive current, of motor driver 110.

Temperature sensor 118 can also sense the temperature of one or more other circuits, or one or more components of such circuits. In particular, such other circuit(s) can include circuits that are not directly heated by any heating element.

Although hair straighteners 100 and 200 are described as including an impeller driven by motor 106, in alternative implementations, a hair straightener is provided in which heating elements directly heat one or more styling plates disposed on inner surfaces of first and second arms. In that case, the ambient temperature is estimated based on factors other than power supplied to a motor. For example, the other factors described above may be used in estimating the ambient temperature, optionally including the amount of current or power being used by heater driver 112 to drive heating element(s). Optionally, heater driver 112 may be disposed in a separate control box (similar to control box 134) with temperature sensor 118, and the potential effects of the heater drive current or power output used to correct an ambient temperature estimate, in a similar manner as described in relation to motor driver 110 in control box 134 above.

Turning to Figure 4, there is shown a haircare appliance in the form of a hairdryer 300. Although hairdryer 300 operates slightly differently compared to hair straightener 100 and hair straightener 200, it still shares many features and components with hair straightener 100 and hair straightener 200, and the same reference signs are used to indicate corresponding features.

Hairdryer 300 includes an air path 144 within a barrel 146. Motor 106, impeller 104, and a heating element 148 are disposed within their path 144. Hairdryer 300 also includes a handle 150, within which are disposed motor driver 110, heater driver 112, and user interface 132. In use, impeller 104 is driven by motor 106 to drive air, indicated by arrow 152, through barrel 146 and past heating element 148. The heated air exits barrel 146 to dry hair under control of the user.

Although hairdryer 300 includes a separate control box 134 similar to that of hair straightener 200, the skilled person will appreciate that a separate control box 134 is not necessary. Hairdryer may, for example, incorporate controller 114 within handle 150 or barrel 146.

Turning to Figure 5, there is shown a method 400 of controlling a haircare appliance. The haircare appliance may be a hair straightener, hairdryer, or any other haircare appliance that styles, straightens, dries, or otherwise treats hair with heat and/or moving air.

Method 400 comprises repeatedly sensing 402 a temperature of an electronic circuit within the haircare appliance. The electronic circuit can take any suitable form, and is defined in the same manner as above. For example, the electronic circuit may comprise one or more processors, and sensing the temperature may comprise sensing the temperature of the one or more processors. Optionally, the temperature sensor is integrated within the processor, and sensing the processor temperature comprises reading a temperature value from a memory within, or associated with, the processor.

Ambient temperature is then estimated 404 at least partly based on the sensed temperature. Optionally, the ambient temperature may be estimated using any of the methods, procedures and/or hardware described above. For example, the ambient temperature may be estimated 404 at least partly based on a drive current output by the drive circuitry. Optionally, the ambient temperature may be estimated 404 based at least partly on multiple temperature signal values (such as values spaced apart in time), and/or based at least partly on differential temperature values calculated based on changes in the temperature signal over time.

Drive circuitry of the haircare appliance is prevented 406 from outputting a drive current when the estimated ambient temperature is lower than an ambient temperature threshold.

In the case of both hair straightener 100 and hair straightener 200, controller 114 may be enclosed within an unventilated part of housing 102 or control box 134. This lack of exposure to ambient air creates additional challenges for sensing the ambient temperature, which may be at least partly addressed by the above-described hair appliances. Hair appliances, in general, may be operated in relatively damp environments, such as bathrooms, and with damp hair. They may also regularly be moved between environments at significantly different temperatures, such as a bathrooms and bedrooms. As such, managing the potential for condensation risks is particularly important in haircare appliances relative to appliances that may be used more statically and in more consistent environments.

While various particular haircare appliances have been described, the skilled person will appreciate that the teachings discussed herein may be applied to other types of haircare appliance, such as hair curlers, curling wands, and the like, for example.

Claims

1. A haircare appliance comprising: drive circuitry; a controller in communication with the drive circuitry, for controlling a drive current output by the drive circuitry; and a temperature sensor for supplying a temperature signal to the controller, the temperature signal being indicative of a temperature of an electronic circuit within the haircare appliance; the controller being configured to estimate an ambient temperature at least partly based on the temperature signal, and to prevent the drive circuitry from outputting the drive current when the estimated ambient temperature is lower than an ambient temperature threshold.

2. The haircare appliance of claim 1, wherein the electronic circuit comprises a processor, and the temperature sensor is configured to sense the processor temperature.

3. The haircare appliance of claim 2, wherein the temperature sensor is integrated with the processor.

4. The haircare appliance of claim 2 or 3, wherein the processor forms part of the controller.

5. The haircare appliance of any preceding claim, wherein the controller is configured to estimate the ambient temperature at least partly based on the drive current or a power related to the drive current.

6. The haircare appliance of any preceding claim, wherein the drive circuitry comprises a motor driver, the haircare appliance comprising an electric motor configured to be driven by drive current from the motor driver.

7. The haircare appliance of any preceding claim, wherein the drive circuitry comprises a heater driver, the haircare appliance comprising a heating element configured to be driven by drive current from the heater driver.

8. The haircare appliance of any preceding claim, wherein the controller is configured to estimate the ambient temperature based at least partly on multiple temperature signal values.

9. The haircare appliance of claim 8, wherein the controller is configured to estimate the ambient temperature based at least partly on differential temperature values calculated based on changes in the temperature signal values over time.

10. The haircare appliance of any preceding claim, comprising a first housing within which is disposed at least one heating element, and a second housing connected to the first housing, wherein the temperature sensor is disposed within the second housing.

11. The haircare appliance of claim 10, wherein the first housing is connected to the second housing by a power and/or communications cable.

12. The haircare appliance of claim 10 or 11 when dependent upon claim 6, wherein the first housing comprises the electric motor and the second housing comprises the motor driver.

13. The haircare appliance of claim 12, wherein the controller is configured to estimate the ambient temperature at least partly based on the drive current output by the motor driver, or a power related to the drive current output by the motor driver.

14. A method of controlling a haircare appliance, the method comprising: repeatedly sensing a temperature of an electronic circuit within the haircare appliance; estimating an ambient temperature at least partly based on the sensed temperature; and preventing drive circuitry of the haircare appliance from outputting a drive current when the estimated ambient temperature is lower than an ambient temperature threshold.

15. The method of claim 14, wherein the electronic circuit comprises a processor, and sensing the temperature comprises sensing the processor temperature.

16. The haircare appliance of claim 15, wherein the temperature sensor is integrated with the processor, and sensing the processor temperature comprises reading a temperature value from a memory within, or associated with, the processor.

17. The method of any one of claims 14 to 16, comprising estimating the ambient temperature at least partly based on a drive current output by the drive circuitry. 17

18. The method of claim 17, wherein the drive circuitry comprises a motor driver, the haircare appliance comprising an electric motor configured to be driven by the motor driver, the method comprising estimating the ambient temperature at least partly based on the drive current output by the motor driver.

19. The method of any one of claims 14 to 18, comprising estimating the ambient temperature based at least partly on multiple temperature signal values.

20. The method of claim 17, comprising estimating the ambient temperature based at least partly on differential temperature values calculated based on changes in the temperature signal values over time.

21. The method of any one of claims 14 to 20, wherein the haircare appliance comprises: a first housing within which is disposed at least one heating element or an electric motor; and a second housing connected to the first housing, the first temperature sensor being disposed in the second housing.

22. The method of claim 21, wherein an electric motor is disposed within the first housing, and the drive circuitry comprises a motor driver disposed within the second housing, the motor driver being configured to provide a drive current to drive the electric motor.