BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows schematic of a conventional lithium-ion battery protection device.
FIG. 2 shows schematic of the series-parallel module of a lithium-ion battery protection device according to a preferred embodiment of the present invention;
FIG. 3 shows schematic of the series-parallel module of a lithium-ion battery protection device connected in parallel with battery according to a preferred embodiment of the present invention;
FIG. 4 shows schematic of multiple serially connected lithium-ion batteries of a lithium-ion battery protection device according to a preferred embodiment of the present invention;
FIG. 5 shows schematic of multiple serially connected lithium-ion batteries of a lithium-ion battery protection device according to another preferred embodiment of the present invention;
FIG. 6 shows schematic of an externally connected circuit with multiple serially connected lithium-ion batteries of a lithium-ion battery protection device according to a preferred embodiment of the present invention;
FIG. 7 shows illustration of a lithium-ion battery protection device according to still another preferred embodiment of the present invention;
FIG. 8 shows illustration of a lithium-ion battery protection device according to yet another preferred embodiment of the present invention; and
FIG. 9 shows flow diagram of a method of lithium-ion battery protection according to a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 and FIG. 3 respectively show schematic of the parallelly connected module of the lithium-ion battery protection device and schematic of the parallelly connected module of the lithium-ion battery protection device connected in parallel with a battery according to a preferred embodiment of the invention. In the present invention, protection device 1 includes abnormality detection circuit 2 and light-coupling circuit 3.
Abnormality detection circuit 2 is to detect the voltage of rechargeable battery 4, and output a detection signal to light-coupling circuit 3.
Light coupling circuit 3 adjusts an impedance of the light coupling circuit 3 based on the detection signal so as to either break the connection between the protection device 11 and the externally connected circuit, or cause the rechargeable battery 4 to charge or discharge.
Preferably, light coupling circuit 3 includes an LED 31 (Light Emitting Diode) and a transistor 32. LED 31 is electrically coupled to the abnormality detection circuit 2, for turning on (to emit light) or off based on the voltage of the rechargeable battery 4. Transistor 32 is electrically coupled to the externally connected circuit. The impedance of the transistor is determined based on whether the LED is emitting light. The transistor 32 is connected to or disconnected from the externally connected circuit based on its own impedance variation.
In this embodiment, when battery 4 is operating normally, abnormality detection circuit 3 outputs the detection signal of the voltage of the rechargeable batteries 4 to LED 31 of light-coupling circuit 3. The LED 31 starts to emit light after receiving the detection signal to cast light on the opposing transistor 32 such that the impedance across two ends of the transistor 32 is very low.
If battery 4 is experiencing abnormality, abnormality detection circuit 2 stops outputting signals to LED 31. Hence, LED 31 is turned off and stops to emit light, thus no light is being cast on the opposing transistor 32. The impedances across two ends of transistor 32 become so high to the extent of almost an open circuit.
Since the two ends of light-coupling circuit 3 communicate by the illumination of light, there is no need for any electrical contact. Thus, a very good electrical insulation exists between these two ends. Taking advantage of such characteristic, as seen from FIG. 4, by serially connecting many lithium-ion batteries 4, which are parallelly connected with the battery protection module, the two ends of transistor 32 of each module are also serially connected, and the two ends of the entire array of transistors 32 are completely electrically insulated from the two ends of the entire array of lithium-ion batteries 4.
In FIG. 4, if any one of the array of battery 4 is experiencing abnormality, as mentioned above, the abnormality detection circuit 2 corresponding to said particular battery outputs a detection signal to stop the corresponding LED 32 from emitting light. Thus, the transistor 32 opposing said LED 32 does not receive any light illumination; hence, the impedance across the two ends of that transistor 32 becomes very high to the extent of nearly an open circuit. Since the array of transistors 32 are serially connected, the impedance across the two ends of the entire array of transistors 32 also becomes very high, to the extent of nearly an open circuit.
Conversely, if all the lithium-ion batteries are operating normally, the impedance across two ends of the entire array of transistors 32, namely ends A and B, becomes very low. When any one of the array of lithium-ion batteries 4 is experiencing abnormality, the impedance across points A and B becomes very high, to the extent of nearly an open circuit.
Then, taking in consideration of the impedance variation of transistors 32 across points A and B, another lithium-ion battery protection device of having multiple serially connected lithium-ion batteries can be designed, and the schematic of which is as shown in FIG. 5.
In this embodiment, circuit switch 5 and switch control circuit 6 are implemented in addition to the protection device. Switch control circuit 6 is electrically coupled to the last light-coupling circuit 3 of the array, for outputting a control signal based on the impedance of light-coupling circuit 3. Circuit switch 5 is electrically coupled to switch control circuit 6, for determining whether to charge or discharge current based on the control signal.
Thus, when the impedance across points A and B is low, circuit switch 5 is switched on to permit current flow. On the other hand, when the impedance across points A and B is high, circuit switch 5 is switched off to terminate the charging or discharging of current.
FIG. 6 shows schematic of multiple serially connected lithium-ion batteries and an externally connected circuit of the lithium-ion battery protection device according to a preferred embodiment of the invention. Points A and B are electrically coupled to the electrically connected circuit 7, which can for instance be a system or a battery charger.
In FIG. 6, abnormality detection circuit 2 informs the externally connected circuit 7 based on the impedance variation across points A and B. That is, when externally connected circuit 7 detects that the impedance across points A and B is very low, externally connected circuit 7 operates normally. However, when externally connected circuit 7 detects that the impedance across points A and B is very high, externally connected circuit 7 ceases to operate so as to terminate battery from charging or discharging.
FIG. 7 shows illustration of a lithium-ion battery protection device according to another preferred embodiment of the invention. In this embodiment, a recognition circuit 8 is additionally added, which is electrically connected to light coupling circuit 3 of protection device 1. Preferably, recognition circuit 8 is an impedance value Rx. Light-coupling circuit 3 adjusts an impedance of light-coupling circuit 3 based on the detection signal, for breaking the connection between rechargeable battery 4 and externally connected circuit 7. At the same time, recognition circuit 8 outputs a signal (impedance value) to inform the externally connected circuit of which one in the battery 4 array is experiencing abnormality. For instance, using FIG. 4 for illustration, each light-coupling circuit 3 of protection device 1 is electrically connected to a recognition circuit 8. Each recognition circuit 8 is configured an impedance value, such as 5K, 10K, 15K, 20K Ohms etc. When light-coupling circuit 3 of the second protection device 1 in the array is open-circuited, the corresponding externally connected circuit 8 thus sees, for instance, the 10K Ohm impedance value and readily knows that the second battery is experiencing abnormality.
FIG. 8 shows illustration of a lithium-ion battery protection device according to still another preferred embodiment of the invention. In addition to electrically connecting a recognition circuit 8 to light-coupling circuit 3 of protection device 1, abnormality detection circuit 2 is also electrically connected to a balancing circuit 9. When battery 4 is overcharged, abnormality detection circuit 2 outputs a detection signal to balancing circuit 9. Balancing circuit 9 can therefore control battery 4 to initiate discharging in order to prevent damages to the batteries from overcharging.
FIG. 9 shows flow diagram of a method of lithium-ion battery protection according to a preferred embodiment of the invention. First, during battery 4 charging and discharging process, a step is performed to determine whether battery 4 is charging or discharging (step 10). If the battery 4 is determined to be charging, then the method proceeds to step 10a so as to check whether the average voltage of the battery 4 is greater than Vhigh (the maximum charge voltage of a signal battery is such as 4.2V) or less than Vhigh. If greater than Vhigh, method proceeds to step 10b and charging loop is open and no charging action is taken. If the average voltage battery 4 is determined to be less than Vhigh, then step 10C is performed to check whether the output signal of the lithium-ion battery protection device is normal. If abnormal, step 10d is performed to charge battery 4 with low current levels (ilow). If signal is normal, step 10e is performed to charge battery 4 normally.
If battery 4 is determined to be discharging, then the method proceeds to step 10f to check the average voltage of the battery 4. If the average voltage is less than Vlow (minimum discharge voltage of a single battery), step 10g is performed and the discharging loop is open and no discharging action is taken. If the average voltage is greater than Vlow, then step 10h is performed to discharge for a few seconds, then step 10i is performed to check whether the output signal of the lithium-ion battery protection device is normal. If normal, step 10j is performed to continue the discharging. If abnormal, step 10k is performed to terminate the discharging.
The characteristics and the technical contents of the present invention will be explained with reference to the detailed description and the accompanying drawings. However, it should be understood that the drawings are illustrative but not used to limit the scope of the present invention.
Patent Application
20070285062
