A Method of Charging a Battery and a System Having a Dental Light Irradiation Device and a Battery Charging Device

Abstract

A method of charging a battery of a dental light irradiation device has the steps of powering the battery at a first charging current and measuring a first terminal voltage of the battery; powering the battery at a different second charging current and measuring a second terminal voltage of the battery; calculating a battery source voltage; and powering off the battery as soon as the battery source voltage reaches or exceeds the threshold voltage.

Claims

1. A method of charging a battery of a dental light irradiation device, comprising the steps of: (a) powering the battery at a first charging current I.sub.1 and simultaneously at least temporarily measuring a first terminal voltage U.sub.1 of the battery; (b) powering the battery at a different second charging current I.sub.2 and simultaneously at least temporarily measuring a second terminal voltage U.sub.2 of the battery; (c) calculating a battery source voltage U.sub.BAT based on the formula: $U_{BAT}=\frac{U_1.Math.I_2-U_2.Math.I_1}{I_2-I_1}$ and (d) repeating steps (a) to (c) while the battery source voltage U.sub.BAT is below a predetermined threshold voltage, and powering off the battery as soon as the battery source voltage U.sub.BAT reaches or exceeds the threshold voltage.

2. The method of claim 1, wherein the steps (a) and (b) are performed alternately.

3. The method of claim 1, wherein the steps (a) and (b) are performed for a duration of at least 1 second.

4. The method of claim 1, wherein the steps (a) and (b) comprise limiting the first charging current I.sub.1 to a maximum first charging current I.sub.1max and limiting the second charging current I.sub.2 to a different maximum second charging current I.sub.2max.

5. The method of claim 4, wherein the battery is based on one Lithium-ion cell with the maximum first and second charging current I.sub.1max, I.sub.2max being each within a range of 500 mA to 2000 mA.

6. The method of claim 5, wherein the battery is based on one Lithium-ion cell and wherein the threshold voltage is within a range of 4.15 V and 4.25 V.

7. A system comprising a battery charging device being configured for performing the method of claim 1, and a dental light irradiation device, the system comprising a battery for powering the dental light irradiation device, wherein the dental light irradiation device comprises a polymerization light source for emitting visible blue light.

8. The system of claim 7, wherein the battery charging device comprises a constant current source for powering the battery at a first charging current I.sub.1 or, alternatively, at a different second charging current I.sub.2.

9. The system of claim 8, wherein the constant current source is electrically switchable between the first charging current I.sub.1 and the second charging current I.sub.2.

10. The system of claim 7, further comprising a voltage measurement circuit for measuring a terminal voltage of the battery.

11. The system of claim 7, wherein the battery charging device is integrated within the dental light irradiation device.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0027] FIG. 1 is a circuit diagram of an electric circuit according to an embodiment of the invention;

[0028] FIG. 2 is a circuit diagram of a further electric circuit according to an embodiment of the invention; and

[0029] FIG. 3 is perspective view of a dental light irradiation device according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0030] FIG. 1 shows an exemplary wiring diagram of an electric circuit 1 as it may be implemented to put the method of the invention into practice. It is noted that the example represents one possibility of implementing the method of the invention and that the person skilled in the art will recognize alternative electric circuits, including for example integrated circuits and/or programmable circuits, which likewise or identically provide the features of the method of the invention.

[0031] The electric circuit 1 has a battery 10 and a power supply 20. In the example the battery 10 and the power supply 20 are electrically connected to each other. However, generally, the power supply 20 may be disconnectably connectable with the battery 10.

[0032] The battery 10 may for example be part of a dental device (as described in more detail below) and may be permanently or replaceably arranged in the device. The battery 10 comprises a single lithium-ion cell providing a nominal voltage of 3.7 V. An internal resistor 12 is illustrated for explanation. The skilled person will recognize that the internal resistor 12 is typically not provided in the form of a discrete additional electronic component but results from the configuration of the battery as such. The battery 10 may comprise further electric components, for example temperature monitoring circuitry and/or protective circuitry against overcurrent and/or overvoltage.

[0033] The power supply 20 comprises a first and an alternative second loop for selectively powering the battery via the first or second loop, respectively. The first and second loop have a common first loop terminal 21. Further, the first loop has a second loop terminal 22 and the second loop has a third loop terminal 23. A changeover switch 24 is provided for switching between the second and the third loop terminal 22, 23, and thus between the first and second loop respectively. An on-off switch 25 is provided for switching the charging of the battery 10 on or off. The on-off switch 25 in the example is connected to a first battery terminal 13 such that the first battery terminal 13 can be electrically connected to or, alternatively, disconnected from the first loop terminal 21 by means of the on-off switch 25. The changeover switch 24 is connected to a second battery terminal 14 such that the second battery terminal 14 can be electrically connected to the second loop terminal 22 or, alternatively, to the third loop terminal 23 by means of the changeover switch 24.

[0034] The electric circuit 1 is thus configured to perform a method of charging the battery 10. In particular, the battery 10 can be charged at a first charging current I.sub.1. With the changeover switch 24 being set to connect the first loop and the battery 10 with each other (via the first and second battery terminals 13, 14) a first constant current source 26 powers the battery 10 at the first charging current I.sub.1. The first constant current source 26 limits the first charging current I.sub.1 to a maximum first charging current I.sub.1max. While the battery 10 is powered at the first charging current I.sub.1 a first terminal voltage U.sub.1 of the battery 10 is measured between the first and second battery terminals 13, 14. The person skilled in the art will recognize that the actual relevant voltage in the charging of a battery typically is the source voltage. However, according to the invention a first terminal voltage U.sub.1 (that likely differs from the source voltage) is measured during the battery 10 is powered.

[0035] The battery 10 is powered at the first charging current I.sub.1 for a duration or time period that may be pre-determined or that may be user-determinable. Upon lapse of the time period the changeover switch 24 is set to connect the second loop and the battery 10 with each other (via the first and second battery terminals 13, 14). Setting the changeover switch 24 to connect the second loop and the battery 10 with each other causes the first loop and the battery 10 to be disconnected and setting the changeover switch 24 to connect the first loop and the battery 10 with each other causes the second loop and the battery 10 to be disconnected. At that stage a second constant current source 27 powers the battery 10 at a second charging current I.sub.2 that is different from the first charging current I.sub.1. Also, the second constant current source 27 limits the second charging current I.sub.2 to a maximum second charging current I.sub.2max. While the battery 10 is powered at the second charging current I.sub.2 a second terminal voltage U.sub.2 of the battery 10 is measured between the first and second battery terminals 13, 14.

[0036] The first and second terminal voltage U.sub.1, U.sub.2 may be each measured once while the battery 10 is powered, or the first and second terminal voltage U.sub.1, U.sub.2 may be each monitored over at least a part of the time period over which the battery 10 is powered and an average or maximum voltage may be assumed as the first and second terminal voltage U.sub.1, U.sub.2.

[0037] The steps of powering the battery 10 at the first charging current I.sub.1 and powering the battery 10 at the second charging current I.sub.2 are repeated until the battery 10 has been charged to the desired charge condition. To determine the charge condition a battery source voltage U.sub.BAT is calculated based on the measured first and second terminal voltage U.sub.1, U.sub.2 and the first and second charging current I.sub.1, I.sub.2. The battery source voltage U.sub.BAT is calculated based on the formula:

[00002]$U_{BAT}=\frac{U_1.Math.I_2-U_2.Math.I_1}{I_2-I_1}$

[0038] Once the battery source voltage U.sub.BAT has reached (or exceeded) a predetermined threshold voltage the battery is powered off. This means that once the battery source voltage U.sub.BAT has reached (or exceeded) the predetermined threshold voltage the on-off switch 25 is set to disconnect the common first loop terminal 12 from the first battery terminal 13. This causes the first and second loop to disconnect from the battery 10.

[0039] Although the electric circuit 1 is illustrated with discrete switches, resistors and other elements the method of the invention may be implemented on alternative hardware and/or software. In particular, desirably the electric circuit 1 is configured to automatically perform the method of the invention.

[0040] FIG. 2 outlines an electric circuit 1 that is based on a (preferably programmed and/or programmable) micro-controller 120. The micro-controller 120 is powered by a power source 130. Further, the micro-controller 120 has connectors 13a, 14a for powering the battery (not shown) and connectors 13b, 14b for measuring the first and second terminal voltage U.sub.1, U.sub.2 of the battery. The electric circuit 1 is configured to automatically perform the steps of alternately powering the battery at the first and second charging current I.sub.1, I.sub.2 until the battery 10 has been charged to the desired charge condition. The time period for which the battery is powered at the first or second charging current is preferably about 1 second or more, for example within a range of 1 second to 30 seconds. Thus, the powering at the first and second charging current I.sub.1, I.sub.2 is alternated at a low frequency. This helps minimizing the charging time because it takes some time for the battery to absorb energy after a charging power is applied so that less changes between the charging currents help increasing the charging speed.

[0041] FIG. 3 shows a dental light polymerization device 200. The dental light polymerization device 200 has a polymerization light source 202 (not visible in detail) for emitting blue light. The polymerization light source 202 comprises one or more blue LEDs (Light Emitting Diodes).

[0042] In the example, the polymerization light source 202 is accommodated within the dental light polymerization device 200. A light guide 203 is arranged at the dental light polymerization device 200 for guiding light emitted from the light source 202 toward a light output 204. Other configurations are possible. For example, the light source may be arranged directly or at a short distance behind the light output, or may form the light output.

[0043] The light polymerization device 1 in the example has a polymerization light button 205 and a timer setting button 206 integrated in one rocker switch. The polymerization light button 205 enables a user to activate the polymerization light source (for example for a duration which can be preset via the timer setting button 206) or to deactivate the polymerization light source.

[0044] The dental light polymerization device 200 in the example is an overall wireless device. The light polymerization device 200 contains a rechargeable battery (not visible). Further, a rechargeable spare battery 10 is optionally arranged within a battery charging device 210. The spare battery 10 may be used for replacing the battery contained within the dental light polymerization device 200. For replacing the battery, the dental light polymerization device 200 has a removable closure 201. The closure 201 is configured for hermetically sealing a receptacle in which the battery can be received. In the example the closure 201 can be retained at the dental light polymerization device 200 by a screw or bayonet connection.

[0045] The battery charging device 210 in the example is configured for charging the spare battery 10 received within the battery charging device 210. Further, the battery charging device 210 may be configured for charging the battery contained within the dental light polymerization device 200 via a wireless charging interface (not shown). The wireless charging interface may comprise a coil for receiving electric energy by induction. An electronic circuit may convert this energy into a charging power. The electronic circuit may be additionally be configured as described in FIGS. 1 and 2, and thus may be configured for charging the battery contained within the dental light polymerization device 200 according to the method of the invention.

[0046] For charging the battery within the light polymerization device 200 the battery charging device 210 may be further connected or connectable by a contact-based electric connection.