Device for measuring battery voltage

1. Technical Field

Embodiments of the present disclosure relate to a device for measuring an output voltage of a battery in an electronic device.

2. Description of Related Art

Batteries, especially rechargeable batteries, such as nickel-hydrogen storage batteries, lithium-ion batteries, etc., are widely used as power sources for various electronic devices. When the output voltage of a battery used by an electronic device is too small to drive the electronic device, the electronic device cannot work. Therefore, it is required to timely measure and indicate the output voltage across the battery terminals. Many electronic devices use a main/central processing unit chip, such as a microcontroller (MCU), to monitor and measure the output voltage of the battery. This function needs one or two dedicated ports of the MCU. Thus less ports are free and the MCU is not as efficient.

Therefore, an independent device for measuring the output voltage of a battery is needed.

Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a block diagram of a device for measuring an output voltage of a battery in accordance with one embodiment of the present disclosure.

FIG. 2 is a schematic circuit diagram of the device of FIG. 1 .

Referring to FIG. 1 , a device 200 is used to measure an output voltage of a battery 100 and displaying the voltage level on a display panel 300 . The battery 100 is used to power an electronic device (not shown). The device 200 and the display panel 300 are components of the electronic device. The electronic device may be a mobile phone, a laptop computer, or a media player.

The device 200 includes a detecting unit 201 , an encoding unit 202 , a control unit 203 , and a processing unit 204 . The detecting unit 201 is configured to detect the output voltage of the battery 100 , and generate a first signal, a second signal, and a third signal accordingly. In the embodiment, the first, second, and third signals are voltages which are in proportion to the output voltage of the battery 100 . The first signal is always greater than the second signal. The third signal is always greater than the first signal.

The encoding unit 202 is configured to generate a first code and a second code according to the first signal and the second signal. In the embodiment, the first code is logic “0” when the first signal is greater than a reference voltage, and is logic “1” when the first signal is lower than the reference voltage. The second code is logic “0” when the second signal is greater than the reference voltage, and is logic “1” when the second signal is lower than the reference voltage.

The control unit 203 is configured to modify the second code when the third signal indicates that the output voltage of the battery 100 is lower than a third preset value. In the embodiment, when the output voltage is lower than the third preset value, the first and second signals are both lower than the reference voltage, and the control unit 203 sets the second code to logic “0”.

The processing unit 204 is configured to generate and output display control signals according to the first and second codes. The display control signals are used to control the display panel 300 to display the voltage level of the battery 100 . In the embodiment, the processing unit 204 includes a digital signal processing integrated circuit (DSP IC).

Referring to FIG. 2 , in one embodiment, the detecting unit 201 includes a first resistor R 1 , a second resistor R 2 , a third resistor R 3 , a fourth resistor R 4 , a fifth resistor R 5 , a sixth resistor R 6 , a first output terminal 11 for outputting the first signal, a second output terminal 12 for outputting the second signal, and a third output terminal 13 for outputting the third signal. The first and second resistors R 1 , R 2 are connected in series between the positive pole of the battery 100 and ground. The third and fourth resistors R 3 , R 4 are connected in series between the positive pole of the battery 100 and ground. The fifth resistor R 5 and the sixth resistor R 6 are connected in series between the positive pole of the battery 100 and ground. The first output terminal 11 is connected to a first node between the first and second resistors R 1 , R 2 . The second output terminal 12 is connected to a second node between the third and fourth resistors R 3 , R 4 . The third output terminal 13 is connected to a third node between the fifth and sixth resistors R 5 , R 6 . The value of R 6 /(R 5 +R 6 ) is greater than the value of R 2 /(R 1 +R 2 ). The value of R 2 /(R 1 +R 2 ) is greater than the value of R 4 /(R 3 +R 4 ).

The encoding unit 202 includes an integrated circuit (IC) 21 and a seventh resistor R 7 . The IC 21 is integrated with a first operational amplifier (op-amp) 211 and a second op-amp 212 . The IC 21 also includes eight pins 21 a - 21 h . Pin 21 a is connected to the inverting input terminal of the first op-amp 211 , and is configured to receive the first signal. Pin 21 b is connected to the inverting input terminal of the second op-amp 212 , and is configured to receive the second signal. Pin 21 c is connected to the output terminal of the first op-amp 211 to output the first code. Pin 21 d is connected to the output terminal of the second op-amp 212 to output the second code. Pin 21 e is connected to the non-inverting input terminal of the first op-amp 211 and a power supply 22 via the seventh resistor R 7 . Pin 21 f is connected to the non-inverting input terminal of the second op-amp 212 and the power supply 22 . Pin 21 g is connected to the negative power terminal of the first and second op-amps 211 , 212 , and is also grounded. Pin 21 h is connected to the positive power terminal of the first and second op-amps 211 , 212 and is also coupled to the power supply 22 . A Zener diode is connected between pin 21 f and pin 21 g . Thus, when the power supply 22 supplies an operation voltage to pin 21 f , a voltage at pin 21 f (the non-inverting input terminal of the second op-amp 212 ) is wired to the Zener voltage of the Zener diode, that is, the reference voltage as described above.

The control unit 203 includes a first switching component Q 1 , a second switching component Q 2 , a eighth resistor R 8 , and a ninth resistor R 9 . In the embodiment, the first and second switching components Q 1 , Q 2 are both NPN type bipolar junction transistors. In other embodiments, the first and second switching components Q 1 , Q 2 may be field effect transistors (FET), insulated gate bipolar transistors (IGBT), or other transistors.

The collector of the first switching component Q 1 is connected to the power supply 22 to receive the operation voltage. The emitter of the first switching component Q 1 is grounded via the ninth resistor R 9 . The base of the first switching component Q 1 is connected to the third output terminal 13 of the detecting unit 201 to receive the third signal. The collector of the second switching component Q 2 is connected to pin 21 d and the encoding unit to modify the second code. The emitter of the second switching component Q 2 is grounded. The base of the second switching component Q 2 is connected to the emitter of the first switching component Q 1 via the eighth resistor R 8 .

In operation, assuming the maximum output voltage of the battery 100 is QC. When the output voltage is greater than a first preset value, the first and second signals are both greater than the reference voltage, and the third signal is a high level voltage. Therefore, the first code and the second code are logic “0”. The processing unit 204 may control the display panel 300 to display an image of a battery including four black blocks representing or indicating the level of the output voltage of the battery. In this embodiment, when the battery is more than three-fourths charged, the four blocks fill the battery image.

When the output voltage is greater than a second preset value and lower than the first preset value, the first signal is greater than the reference voltage, the second signal is lower than the reference voltage, and the third signal is also considered as a high level voltage. Therefore, the first code is logic “0”, and the second code is logic “1”. The processing unit 204 may control the display panel 300 to display an image of the battery including three black blocks.

When the output voltage is greater than the third preset value and lower than the second preset value, the first and second signals are both lower than the reference voltage, and the third signal is also considered as a high level voltage. Therefore, the first code and the second code are both logic “1”. The processing unit 204 may control the display panel 300 to display an image of the battery including two black blocks to indicate that the battery voltage is low.

When the output voltage is lower than the third preset value, the first and second signals are both lower than the reference voltage, and the third signal becomes a low level voltage. Therefore, the first code is logic “1”, the first switching component Q 1 is turned on to apply the operation voltage to the base of the second switching component Q 2 . Thus the second switching component Q 2 is turned on to ground pin 21 d . As a result, the second code is changed to logic “0”. The processing unit 204 may control the display panel 300 to display an image of the battery including one black block to indicate that the battery voltage is severely low and the battery 100 should be charged or replaced.

It is to be understood, however, that even though numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of the disclosure, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.