Discharge state indicator
View Patent ↗A circuit for displaying the state of a battery that is almost discharged features a battery, an inductive load, and a controllable switch connected in series. The circuit also includes a display element connected in series with the inductive load and the battery. The controllable switch is opened when a voltage of the battery is lower than a first threshold level and is only closed again when the voltage of the battery is greater than a second threshold level. The circuit may also include a control circuit having a comparator which compares the voltage of the battery with the first threshold level and the second threshold level and triggers the controllable switch accordingly.
1. A battery-operated shaver comprising:
a discharge state indicator circuit comprising:
a battery,
an inductive load connected to the battery,
a controllable switch connected in series with the inductive load and the battery, and
a display element connected in series with the inductive load and the battery, wherein when a voltage of the battery is lower than a first threshold level the controllable switch opens to change a state of the display element and a voltage that is induced in the inductive load is added to the voltage of the battery sufficient for operating the display device.
2. The battery-operated shaver of claim 1 , wherein the controllable switch prevents operation of the inductive load when the voltage of the battery is lower than a second threshold level.
3. The battery-operated shaver of claim 1 , wherein the second threshold level is greater than the first threshold level.
4. The battery-operated shaver of claim 1 , wherein the inductive load has a higher electric power consumption than the display element.
5. The battery-operated shaver of claim 1 , wherein the inductive load comprises an electric motor.
6. The battery-operated shaver of claim 5 , wherein the controllable switch prevents operation of the electric motor when the voltage of the battery is lower than a second threshold level.
7. The battery-operated shaver of claim 6 , wherein the second threshold level is greater than the first threshold level.
8. The battery-operated shaver of claim 6 , further comprising a mechanical switch connected in series with the controllable switch, the inductive load, and the battery.
9. The battery-operated shaver of claim 8 , wherein the electric motor is prevented from operation even when the mechanical switch is closed.
10. The battery-operated shaver of claim 1 , wherein the display element comprises a light-emitting diode.
11. The battery-operated shaver of claim 10 , wherein the light-emitting diode flashes indicating a nearly discharged state of the battery.
12. The battery-operated shaver of claim 1 , wherein the controllable switch comprises a transistor.
13. The battery-operated shaver of claim 12 , wherein a collector-emitter segment of the transistor is connected in series with the inductive load and the battery.
14. The battery-operated shaver of claim 12 , further comprising a control circuit having an input terminal connected to the battery and an output terminal connected to a base terminal of the transistor, wherein the control circuit is configured to control the transistor based on the voltage of the battery.
15. The battery-operated shaver of claim 12 , wherein the display element is connected in parallel with a collector-emitter segment of the transistor.