Hair Treatment Device

Abstract

The hair treatment device has an IPL lamp driven by pulsed energy. A switch is in series with the IPL lamp and is switched at a frequency ranging from 50 kHz to 500 kHz to provide a pulsed current supply to the IPL lamp with pulses shorter than the duration of the entire IPL pulse. Current modulation is used to eliminate the initial current peak and the associated peak in light output. Modulation can be used during the entire IPL pulse or only during a portion of it. Alternatively, the duty cycle or frequency of modulation can be varied during the IPL pulse to optimize the light output. During the first portion of the energy pulse, a pulsed current supply is provided to the IPL lamp, and during the last portion of the energy pulse, a continuous current supply is provided.

Description

[Technical field]

[0001] The present invention relates to a hair treatment device, and more particularly to hair removal or hair growth inhibition by photoepilation. [Background technology]

[0002] Photoepilation for hair removal and hair growth inhibition is well known. Consumer devices for home use are available on the market, such as the Philips® Lumea®. Home devices typically use Intense Pulsed Light Technology (IPL), e.g. with xenon flash lamps, at a relatively low fluence (up to 6.5 J / cm2) compared to commercial devices for permanent photoepilation, which use fluences of more than 10 J / cm2.

[0003] IPL technology uses high-powered handheld flash lamps to deliver intense, visible, broad-spectrum light pulses, typically in the visible spectrum range of 400-1200 nm. Cut-off filters are used, for example, to selectively filter out shorter wavelengths, especially potentially harmful ultraviolet light. The resulting light has a spectral range that targets specific structures and chromophores, especially melanin pigments in hair. IPL shares some similarities with laser treatments, which both use light to heat and destroy targets. Unlike lasers, which generally use a single wavelength of light that matches only one chromophore and therefore treats only one condition, IPL uses a broad spectrum.

[0004] The light absorbed by the melanin contained in the hair and hair matrix cells generates heat, which damages the hair follicle. When the treatment is repeated at intervals of 2 to 4 weeks, long-lasting hair reduction results are obtained.

[0005] US 2012 / 0010684 A1 discloses a dermatological treatment device having a flashlamp, a pulse driver circuit that provides electrical energy to pulse the flashlamp, and a control circuit that selectively enables the transmission of electrical energy to the flashlamp based on a signal having a duty cycle that indicates when the AC line voltage exceeds a minimum operating voltage threshold. The circuit has a switch in series with the flashlamp that is controlled at a frequency of, for example, 50 kHz to 100 kHz.

[0006] FIG. 1a shows a known pulse generating circuit and FIG. 1b shows the IPL pulse (current versus time) achieved in the Lumea™ system.

[0007] The plasma is ignited by a plasma ignition unit 10. Energy is stored in a main storage capacitor 12 (e.g. 100 J of energy at 400 V). The electrical energy stored in the capacitor is discharged through a lamp 14, resulting in a pulsed operation of the lamp. The lamp is for example a gas-filled linear flash lamp.

[0008] The plasma ignition unit 10 creates a conductive plasma channel of ionized gas atoms or molecules between the lamp electrodes (inside the lamp tube). First, a high voltage (about 15 kV) is applied between the lamp electrodes. The high voltage is needed to create a dielectric breakdown of the gas in the lamp. However, the high voltage cannot provide the charge necessary to open a conductive plasma channel.

[0009] For this purpose, a boost capacitor can be used, which provides the necessary charge. It stores only a small amount of electrical energy, about 1-2% compared to the main capacitor, but its electrical voltage is about 800V.

[0010] The timing sequence of the high voltage boost capacitor discharge and the main capacitor discharge is very precise for the ramp discharge to occur, in particular the three steps overlap, the boost capacitor discharge starts while the gas breakdown is still present and the main capacitor discharge starts before the boost capacitor discharge is terminated.

[0011] The lamp is mounted, for example, in a head of a hair treatment device with a radiation exit opening. During operation, the lamp generates light pulses with a relatively high energy density, which propagate towards the radiation exit opening and irradiate the human skin present in front of the radiation exit opening. Part of the light is absorbed by hair roots and hair follicles present in the skin, which are significantly heated as a result of the relatively high energy density of the light. As a result, the hair roots and hair follicles are damaged or even destroyed, so that hair growth is prevented for a significant period of time or even permanently. Summary of the Invention [Problem to be solved by the invention]

[0012] As the IPL pulse shape shows, the current rises quickly to a maximum value and then decays exponentially as the energy in the capacitor is dissipated and the light pulse is produced. This type of discharge is an exponentially decaying pulse because the current (and the light intensity output of the IPL lamp) follows an exponential decay shape during the IPL flash. In the example shown, the current is stopped after 8 ms by the power transistor.

[0013] This method has the advantage of being easy to implement, because it is cost-effective and the components used occupy a minimal physical volume. However, the high light output intensity at the beginning of the pulse (caused by the initial lamp current peak) can be uncomfortable for the user. Some users describe the IPL flash as painful, others as a sharp, unpleasant tingling.

[0014] It is recognised that it would be desirable to make the light output during an IPL pulse more uniform, ideally with a so-called block pulse, particularly by adapting the lamp current so that the light output is more constant over the duration of the IPL pulse, rather than having a high initial peak, as shown in Figure 1b.

[0015] Fig. 2a shows additional control electronics 20 between the energy storage capacitor 12 and the lamp 14, and Fig. 2b shows the desired block pulse 22. A more uniform lamp current during an IPL pulse is beneficial for user comfort. It also paves the way for benefits regarding treatment personalization and treatment efficiency, as evidenced in commercial IPL devices.

[0016] However, known or contemplated implementations of block pulse discharge to generate an IPL flash are less cost effective and the elements take up more space within the device than do free discharge implementations.

[0017] FIG. 3 shows a first possible realization concept of a block pulse discharge for an IPL flash using a coil 30 and current modulation.

[0018] A storage capacitor 12 is coupled in series with the lamp and coil by a first switch 16, and a second switch 18 is coupled in parallel with the lamp and coil combination. The operation of the two switches 16, 18 is coordinated such that one is open when the other is closed and vice versa. Thus, the coil is used as a current smoothing circuit, which is alternately loaded with energy and then releases energy to the IPL lamp.

[0019] 4 shows a second possible implementation concept of a block pulse discharge for an IPL flash using a coil 30, a power diode 40, and a controller 42 (microprocessor). The controller uses a current feedback signal CS provided by a current sensor to control a current modulation scheme using a switch 19 in series with the IPL lamp.

[0020] Both of these approaches make use of a large physical coil 30 that forms part of the current regulation circuit. The main drawbacks are the large physical space required in the device and the high cost of the solution. A magnetic core coil cannot be used because it may face saturation problems due to high currents and / or high switching frequencies. Therefore, an air core coil is needed because it does not saturate. However, due to its low inductance, it requires a large space.

[0021] Therefore, there is a need for a cost-effective and space-efficient solution to the above-mentioned user discomfort caused by IPL exponential decay pulses. [Means for solving the problem]

[0022] The invention is defined by the claims.

[0023] According to an example embodiment of the present invention, there is provided a skin treatment device comprising: Intense Pulsed Light IPL lamp and a drive circuit for driving the IPL lamp with an energy pulse of a first duration, the drive circuit including an ignition unit and a main storage capacitor; A switch in series with the IPL lamp; and a controller that controls the switch at a frequency in the range of 50 kHz to 300 kHz to provide a pulsed current supply to the IPL lamp with a current supply pulse of a second duration that is shorter than the first duration during at least a portion of the energy pulse.

[0024] This device provides high frequency modulation of the IPL lamp current, particularly in the range of 50 kHz to 500 kHz, which is used to eliminate initial current peaks and associated light output peaks.

[0025] High frequency modulation of the lamp current can be used over the entire duration of the energy pulse or for only a part of the energy pulse, for example the first part (e.g. half) of the energy pulse has a current modulation, while the last part (e.g. half) of the energy pulse has no current modulation after the initial current peak has been removed, i.e. a continuous supply of current and thus a free decay.

[0026] The reduction in current peaks can be achieved without extra inductive or capacitive elements, so that small capacitors and inductors can be used if desired for circuit optimization. The modulation provided by the switch can be used during the entire IPL pulse (i.e., initial duration) or only a portion of it.

[0027] The lower value, 50 kHz, indicates the switching frequency below which the light intensity is seen to follow an exponential (but pulsating) decay. The initial light intensity is nevertheless high. The upper limit of 500 kHz limits the switching losses and the thermal load, as well as the impact on the lifetime of the circuit elements (which worsens at higher frequencies).

[0028] Preferred frequencies are in the range of 100 kHz to 300 kHz, for example 100 kHz to 250 kHz, or 150 kHz to 300 kHz, or 150 kHz to 250 kHz.

[0029] The first duration is, for example, in the range of 5 ms to 10 ms, e.g., 8 ms. The IPL pulse is therefore much longer than the switch control pulse, i.e. the second duration as defined above (for example, 100 kHz corresponds to a pulse period of 10 μs, and therefore a pulse duration of 5 μs at a duty cycle of 50%).

[0030] The duty cycle and frequency of the pulsed supply of current may be fixed, or they may be adjusted to compensate for lamp aging, for example using analysis of past flashes.

[0031] The controller may be configured to adjust the frequency over time during the pulse of energy. The controller may, for example, alternatively or additionally be configured to adjust a duty cycle of control of the switch over time during the pulse of energy.

[0032] These measures allow the light output characteristics over the duration of the IPL pulse to be optimized.

[0033] For example, the controller may be configured to increase the duty cycle over time during the pulse of energy from a first value in the range of 20% to 40% to a second value in the range of 40% to 70%, which has been found to allow a flatter light intensity profile to be produced.

[0034] The apparatus may further include a diode electrically in parallel with the IPL lamp, with the anode of the diode connected to the low voltage terminal of the IPL lamp and the cathode of the diode connected to the high voltage terminal of the IPL lamp, the diode providing a conduction path (against the lamp current) that allows the apparatus to utilize any residual inductance that the lamp may have during modulation.

[0035] The device may further include a secondary capacitor in parallel with the IPL lamp, which may be charged while the main capacitor output is on and discharged onto the lamp while the main capacitor is off, thus providing an additional smoothing function.

[0036] For example, the secondary capacitor has a capacitance of less than 1% of the capacitance of the main capacitor, so it does not occupy a large amount of space or introduce large costs.

[0037] In another example, the device further includes a diode and a secondary capacitor connected in series with each other and both electrically connected in parallel with the IPL lamp, and an inductor between the high voltage terminal of the IPL lamp and the junction between the diode and the secondary capacitor.

[0038] Preferably, the secondary capacitors have a capacitance less than 1% of the capacitance of the main capacitor, and the inductors have an inductance in the range of 1mH to 100mH, so that they do not occupy a large amount of space or introduce large costs.

[0039] The IPL lamp for example has a flash lamp with a fluence of 6.5 J / cm2 or less, making the device suitable as a consumer device for home use.

[0040] The device may further comprise a current sensor or a light intensity sensor to provide a feedback signal to the controller, so that the feedback can be used to adjust the drive current or light output.

[0041] The controller can be configured to operate the device in, for example, a first and a second mode, the first mode involving the current supply pulses between the pulses of energy, and the second mode involving the supply of continuous current between the pulses of energy. The first mode can be, for example, particularly suited to sensitive skin areas (e.g., underarms), while the second mode can be used for less sensitive skin areas (e.g., legs). Switching between modes can be manually controlled by a user of the device, or it can be automatic based on sensed input.

[0042] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief description of the drawings]

[0043] [Figure 1]FIG. 1 illustrates a known pulse generating circuit and an IPL pulse (current versus time). [Diagram 2] FIG. 13 shows additional control electronics between the energy storage capacitor and the lamp and illustrates a desired block pulse. [Diagram 3] FIG. 1 shows a first possible implementation concept of block pulse discharge for IPL flash using coils and current modulation. [Figure 4] FIG. 13 shows a second possible implementation concept of block pulse discharge for IPL flash using a coil, a power diode and a controller. [Diagram 5] FIG. 1 shows a first example of a circuit using the approach of the present invention. [Figure 6] FIG. 6 shows a first realization of the circuit of FIG. [Figure 7] FIG. 6 shows a second implementation of the circuit of FIG. [Figure 8] FIG. 1 shows lamp current and light intensity (i.e. light output) during an unmodulated free decay discharge of an IPL device. [Figure 9] FIG. 6 shows lamp current and light intensity when 1 kHz, 50% duty cycle modulation is introduced using the configuration shown in FIG. 5. [Figure 10] FIG. 1 shows current and light output for 5 kHz, 50% duty cycle over long time scales. [Figure 11] FIG. 1 shows current and light output for 5 kHz, 50% duty cycle over short time scales. [Figure 12] FIG. 1 shows current and light output for 10 kHz, 50% duty cycle over long time scales. [Figure 13] FIG. 1 shows current and light output for 10 kHz, 50% duty cycle over short time scales. [Figure 14] FIG. 1 shows current and light output for 20 kHz, 50% duty cycle over long time scales. [Figure 15]FIG. 1 shows current and light output for 20 kHz, 50% duty cycle over short time scales. [Figure 16] FIG. 1 shows current and light output for 50 kHz, 50% duty cycle over long time scales. [Figure 17] FIG. 1 shows current and light output for 50 kHz, 50% duty cycle over short time scales. [Figure 18] FIG. 1 shows current and light output for 100 kHz, 50% duty cycle over long time scales. [Figure 19] FIG. 1 shows current and light output for 100 kHz, 50% duty cycle over short time scales. [Figure 20] FIG. 1 shows current and light output for 150 kHz, 50% duty cycle over long time scales. [Figure 21] FIG. 1 shows current and light output for 150 kHz, 50% duty cycle over a short time scale. [Figure 22] FIG. 1 shows current and light output for 200 kHz, 50% duty cycle over long time scales. [Figure 23] FIG. 1 shows current and light output for 200 kHz, 50% duty cycle over a short time scale. [Figure 24] FIG. 1 shows current and light output for 200 kHz, 30% duty cycle over long time scales. [Diagram 25] FIG. 1 shows the current and light output during a 200 kHz, 30% duty cycle modulated free decay discharge of an IPL device over a short time scale. [Figure 26] FIG. 1 shows current and light output during 200 kHz modulation with variable duty cycle over long time scales. [Figure 27] FIG. 1 shows the current and light output during 200 kHz modulation with variable duty cycle, illustrating the start of an 8 ms pulse with low duty cycle (30%). [Figure 28]FIG. 1 shows the current and light output during 200 kHz modulation with variable duty cycle, illustrating the end of an 8 ms pulse with a large duty cycle (50%). [Figure 29] FIG. 13 shows the light intensity output without modulation and with 200 kHz modulation at various duty cycles. [Diagram 30] FIG. 8 shows a modification to the basic configuration of FIG. 7, comprising an additional diode in parallel with the lamp. [Diagram 31] FIG. 13 shows a modification in which a secondary capacitor in parallel with the lamp is added. [Diagram 32] FIG. 32 illustrates the controller of FIG. 31 adjusting modulation based on current sensor input. [Diagram 33] FIG. 32 illustrates the controller of FIG. 31 adjusting modulation based on light intensity sensor input. [Diagram 34] FIG. 13 shows a modification including a secondary capacitor, a power diode and an inductor. [Diagram 35] FIG. 35 illustrates the controller of FIG. 34 adjusting modulation based on light intensity sensor input. [Diagram 36] FIG. 35 illustrates the controller of FIG. 34 adjusting modulation based on current sensor input. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] For a better understanding of the present invention, and in order to more clearly show how it may be carried into effect, reference will now be made to the accompanying drawings, which are given by way of example only, in which:

[0045] The present invention will now be described with reference to the figures.

[0046] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems and methods, are for purposes of illustration only and are not intended as limiting the scope of the invention. These and other features, aspects and advantages of the devices, systems and methods of the present invention will become better understood from the following description, appended claims and accompanying drawings. It should be understood that the figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

[0047] The present invention provides a hair treatment device having an IPL lamp driven by pulsed energy. A switch is in series with the IPL lamp and is switched at a frequency ranging from 50kHz to 500kHz to provide a pulsed supply of current to the IPL lamp with pulses shorter than the entire IPL pulse duration. Current modulation is used to eliminate the initial current peak and the associated peak in light output. Modulation can be used during the entire IPL pulse or only during a part of it (especially the first part where the initial current peak is reduced). Alternatively, the duty cycle or frequency of modulation can be varied during the IPL pulse to optimize the light output.

[0048] FIG. 5 shows a first example of the inventive approach.

[0049] A switch 50 is provided in the circuit between the main capacitor 12 and the lamp 14. The switch is in series with the lamp and allows or prevents current from flowing through the lamp. The switch allows for fast modulation of the IPL lamp current. The switch can comprise, for example, a power transistor capable of modulating large currents (which can exceed 100A) or any electric or electronic device that allows the IPL lamp current to be modulated.

[0050] FIG. 6 shows an example where the switch is between the high voltage side of the capacitor and the lamp, while FIG. 7 shows the switch between the low voltage, ground side of the capacitor and the lamp.

[0051] The driving circuits, e.g. the plasma ignition unit and booster capacitors used to initiate the discharge, are omitted in Figures 5 to 7 for simplicity. However, they may be entirely standard, e.g. as described above. In these examples, no extra inductive (coil) or capacitive elements are used.

[0052] FIG. 8 shows the lamp current and light intensity (ie, light output) during an unmodulated free decay discharge of an IPL device.

[0053] There is no pulse modulation, just a single square wave input representing the time the switch is on. The opening of the switch (e.g. an IGBT transistor) marks the start of the discharge and the current peaks to a maximum value within a few microseconds (~45 µs). Approximately 130 µs after the IGBT transistor opens, the maximum of the light output is achieved. The exact value at which the current and light output peak depends on the capacitor charging voltage, the type of transistor, and will show deviations between devices. However, the important point is that with this type of free decay discharge IPL pulse, the light intensity peak always follows the current peak.

[0054] After an initial current peak, the current value decays in an exponential manner governed by the decrease in the charge stored in the capacitor. The light intensity follows the same trend, with the intensity decaying.

[0055] Figure 9 shows the corresponding behavior of the device when a 1 kHz, 50% duty cycle modulation is introduced, using the configuration shown in Figure 5. The IPL lamp current follows the modulation fairly accurately due to its fast response time, and the light output follows suit, with some inertia. However, because the modulation frequency is 1 kHz, there is enough time for the current and light output to reach near zero during the off portion of the modulation. The overall envelope of the current and light intensity follows the form of a free decay that is interrupted and resumed.

[0056] When the frequency of the modulation is increased, the current of the IPL lamp can keep up with the modulation, but the light output can no longer keep up with the modulation.

[0057] Various modulation frequencies and several different duty cycles are shown in Figures 10 to 25. The current modulation pulses are much shorter (second duration, e.g. in the order of μs) than the duration of the energy pulses delivered by the IPL lamp by the driving circuit (first duration, e.g. 8 ms).

[0058] To illustrate the overall performance, Figure 10 shows the current and light output during a 5 kHz, 50% duty cycle modulated free decay discharge of the IPL device over a long time scale, which corresponds to a current pulse duration (second duration) of 100 μs.

[0059] FIG. 11 shows the current and light output during a 5 kHz, 50% duty cycle modulated free decay discharge of the IPL device over a short time scale to demonstrate performance at the level of individual pulses.

[0060] Figure 12 shows the current and light output during a 10 kHz, 50% duty cycle modulated free decay discharge of an IPL device over a long time scale, which corresponds to a current pulse duration (second duration) of 50 μs.

[0061] FIG. 13 shows the current and light output during a 10 kHz, 50% duty cycle modulated free decay discharge of the IPL device over a short time scale.

[0062] Figure 14 shows the current and light output during a 20 kHz, 50% duty cycle modulated free decay discharge of an IPL device over a long time scale, which corresponds to a current pulse duration (second duration) of 25 μs.

[0063] FIG. 15 shows the current and light output during a 20 kHz, 50% duty cycle modulated free decay discharge of the IPL device over a short time scale.

[0064] Figure 16 shows the current and light output during a 50 kHz, 50% duty cycle modulated free decay discharge of an IPL device over a long time scale, which corresponds to a current pulse duration (second duration) of 10 μs.

[0065] FIG. 17 shows the current and light output during a 50 kHz, 50% duty cycle modulated free decay discharge of the IPL device over a short time scale.

[0066] Figure 18 shows the current and light output during a 100 kHz, 50% duty cycle modulated free decay discharge of an IPL device over a long time scale, which corresponds to a current pulse duration (second duration) of 5 μs.

[0067] FIG. 19 shows the current and light output during a 100 kHz, 50% duty cycle modulated free decay discharge of the IPL device over a short time scale.

[0068] Figure 20 shows the current and light output during a 150 kHz, 50% duty cycle modulated free decay discharge of the IPL device over a long time scale, which corresponds to a current pulse duration (second duration) of 3.3 μs.

[0069] FIG. 21 shows the current and light output during a 150 kHz, 50% duty cycle modulated free decay discharge of the IPL device over a short time scale.

[0070] Figure 22 shows the current and light output during a 200 kHz, 50% duty cycle modulated free decay discharge of an IPL device over a long time scale, which corresponds to a current pulse duration (second duration) of 2.5 μs.

[0071] FIG. 23 shows the current and light output during a 200 kHz, 50% duty cycle modulated free decay discharge of the IPL device over a short time scale.

[0072] Figure 24 shows the current and light output during a 200 kHz, 30% duty cycle modulated free decay discharge of an IPL device over a long time scale, which corresponds to a current pulse duration (second duration) of 1.5 μs.

[0073] FIG. 25 shows the current and light output during a 200 kHz, 30% duty cycle modulated free decay discharge of the IPL device over a short time scale.

[0074] The figure shows that in the range of 1-30 kHz, the light output shows good modulation with low and high values ​​corresponding to on and off states of modulation. However, above 50 kHz, the modulation of the light output becomes minimal because the light no longer has time to follow the modulation of the current. The overall envelope of the light output has almost no modulation and, importantly, it no longer features a large initial peak that is uncomfortable for the user. The light intensity increases slowly towards a maximum value, after which it starts to decay slowly.

[0075] FIG. 26 shows the current and light output during 200 kHz modulation with a variable duty cycle modulated free decay discharge of an IPL device over a long time scale.

[0076] FIG. 27 shows the current and light output during variable duty cycle 200 kHz modulation, showing the start of an 8 ms pulse with low duty cycle (30%).

[0077] FIG. 28 shows the current and light output during a 200 kHz modulation of the variable duty cycle, showing the end of an 8 ms pulse with a large duty cycle (50%). Thus, in the examples of FIG. 27 and FIG. 28, the duty cycle is ramped up over time from 30% to 50%. More generally, the duty cycle is ramped or stepped up from a low value (where elimination of current peaks is most effective) to a high value. The high value can be 100%, so that there is a pulsed supply of current to the IPL lamp during the first part of the pulse of energy and a continuous supply of current during the last part of the pulse of energy. In such a case, modulation can be used not only for the entire duration of the pulse, but also for a part of the pulse.

[0078] Figure 29 shows examples of the light intensity output of a free discharge without modulation and with 200kHz modulation and various duty cycles, i.e. 30%, 50% and ramping from 30% to 50%. The sharp initial peak in the light output of the free decay is not present in the modulated curves, indicating that fast modulation can alleviate the discomfort associated with the initial peak of a free decay pulse.

[0079] Figure 30 shows an additional example as a modification to the basic configuration of Figure 7. To take advantage of any residual inductance that the lamp may have during modulation, an additional power diode 70 is provided in parallel with the lamp.

[0080] Figure 31 shows a further modification in which a secondary capacitor 72 is added in parallel with the lamp. The secondary capacitor is allowed to charge while the main capacitor output is on, and discharge onto the lamp while the main capacitor output is off.

[0081] Also shown is a controller 74 (microprocessor) for adjusting the modulation frequency and / or duty cycle based on input from a current sensor or a light intensity sensor.

[0082] FIG. 32 shows a controller that adjusts the modulation based on a current sensor input CS, and FIG. 33 shows a controller that adjusts the modulation based on a light intensity sensor input LS.

[0083] The above examples avoid the need for an inductive element to perform the primary current smoothing function. However, circuit optimization can result in the use of a small inductor. Figures 34 to 36 show example circuits that include the additional use of an inductor.

[0084] Figure 34 shows a secondary capacitor 72 and a power diode 70 in series with each other and both in parallel with the lamp. An inductor 80 is connected between the high voltage terminal of the lamp and a node between the secondary capacitor and the power diode. Again, the secondary capacitor can be charged while the main capacitor output is on and discharged over the lamp while the main capacitor is off.

[0085] As explained above, the main capacitor output is modulated in the 50 kHz to 300 kHz range to eliminate the initial current peak and associated light output peak. Modulation can be used during the entire IPL pulse, or only during a portion of it, while the duty cycle or frequency of the modulation can be varied during the IPL pulse to optimize the light output.

[0086] The secondary capacitor is smaller than the main capacitor, i.e. the capacitance is less than 1% of the capacitance of the main capacitor. If the secondary capacitor is too large, the reduction in the initial current peak will not be optimal. The inductor has a small inductance (on the order of mH).

[0087] FIG. 35 shows an additional controller and light intensity sensor (similar to FIG. 33), and FIG. 36 shows an additional controller and current sensor (similar to FIG. 32).

[0088] As an example, the primary capacitor has a capacitance in the order of millifarads, for example 0.5mF ​​to 10mF, for example 1.4mF. The secondary capacitor has a capacitance in the order of microfarads, for example 10μF to 1mF, for example 22μF.

[0089] The added inductor has, for example, an inductance on the order of milliH, for example 0.5 mH to 10 mH, for example 5 mH.

[0090] The duty cycle and frequency for the pulsed delivery of current are selected based on the lamp details and circuit elements (such as main capacitors). The differences between devices are small, so that different devices are tuned to the same parameters. Over the life of the device, the parameter changes are generally larger than the device-to-device changes because the light output of the lamp degrades over time. These aging changes can optionally be at least partially compensated for by having a controllable duty cycle and / or frequency, controlled using a feedback system that monitors lamp performance over time.

[0091] The above embodiment utilizes current modulation to eliminate the initial current peak and associated light output peak, thereby reducing discomfort to the user. This may only be required for sensitive areas of the skin (e.g. underarms), while less sensitive areas (e.g. legs) do not require current modulation, instead allowing for more rapid energy delivery. Thus, the device can have different operating modes: a (first) modulated current mode and a (second) normal mode without current modulation. This second mode corresponds to the conventional operating mode.

[0092] The device is therefore capable of operating in these two different modes and allows the user to switch between the modes. The device can also automatically switch between modes based on detection of the part of the body to which the device is applied. This can be detected using motion / orientation sensing and / or camera image analysis.

[0093] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the figures, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0094] The functions performed by a processor may be performed by a single processor, or by multiple separate processing units which together may be considered to constitute a "processor". Such processing units may be remote from each other and may communicate with each other via wires or wirelessly.

[0095] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0096] The computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless communication systems.

[0097] It should be noted that when the term "adapted for" is used in the claims or specification, it is intended to be equivalent to the term "configured for." It should be noted that when the term "arrangement" is used in the claims or specification, it is intended to be equivalent to the term "system," and vice versa.

[0098] Any reference signs in the claims should not be construed as limiting the scope of the invention.

Claims

1. A hair treatment device comprising: an intense pulsed light (IPL) lamp; 1. A drive circuit for driving the IPL lamp with a pulse of energy of a first duration, comprising: A drive circuit, the drive circuit including an ignition unit and a main storage capacitor; a switch in series with the IPL lamp; A controller that controls the switch at a frequency in the range of 50 kHz to 500 kHz to provide a pulsed supply of current to the IPL lamp with a current supply pulse of a second duration shorter than the first duration during at least a portion of the pulse of energy, wherein the controller provides a pulsed supply of current to the IPL lamp during an initial portion of the pulse of energy and provides a continuous supply of current during a final portion of the pulse of energy.

2. 2. The hair treatment device of claim 1, wherein the controller controls the switch at a frequency in the range of 100 kHz to 300 kHz.

3. 3. A hair treatment device according to claim 1 or 2, wherein the first duration is in the range of 5 milliseconds to 10 milliseconds.

4. 4. A hair treatment device according to any preceding claim, wherein the controller adjusts the frequency of control of the switch over time during the pulse of energy.

5. 5. A hair treatment device according to any preceding claim, wherein the controller adjusts the duty cycle of control of the switch over time during the pulse of energy.

6. 6. A hair treatment device according to claim 1, wherein the controller increases the duty cycle over time during the pulse of energy from a first value in the range of 20% to 40% to a second value in the range of 40% to 70%.

7. 7. The hair treatment device of claim 1, further comprising a diode in parallel with the IPL lamp, the anode of the diode being connected to a low voltage terminal of the IPL lamp and the cathode of the diode being connected to a high voltage terminal of the IPL lamp.

8. 8. The hair treatment device of claim 7, further comprising a secondary capacitor in parallel with the IPL lamp.

9. 9. A hair treatment device according to claim 8, wherein the secondary capacitor has a capacitance of 1% or less of the capacitance of the main capacitor.

10. a diode and a secondary capacitor in series with each other and both in parallel with said IPL lamp; 7. A hair treatment device according to any one of claims 1 to 6, further comprising an inductor between a high voltage terminal of the IPL lamp and a junction of the diode and the secondary capacitor.

11. 11. The hair treatment device of claim 10, wherein the secondary capacitor has a capacitance less than 1% of a capacitance of the main capacitor, and the inductor has an inductance in the range of 1 mH to 100 mH.

12. 12. A hair treatment device according to any one of the preceding claims, wherein the IPL lamp comprises a flash lamp with a fluence of 6.5 J / cm2 or less.

13. A hair treatment device according to any one of the preceding claims, further comprising a current sensor and / or a light intensity sensor providing a feedback signal to the controller.

14. 14. A hair treatment device according to any one of claims 1 to 13, wherein the controller is configurable to operate the device in a first mode and a second mode, the first mode involving a pulse of current supply during the pulse of energy and the second mode involving a continuous current supply during the pulse of energy.

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