Pre-charging filters to reduce settling time

Various arrangements for determining a voltage of a voltage source using pre-charging are presented. Such arrangements may include a measurement module which includes an analog to digital converter, a driver, and an interface. The interface may be electrically coupled with the analog to digital converter and the driver. The driver may be configured to output current to charge a capacitor. After a first predefined period of time, the driver may stop outputting current to pre-charge the capacitor. After the driver has stopped pre-charging the capacitor and a second predefined period of time has elapsed, the analog to digital converter may be configured to measure a voltage of the capacitor. Such arrangements may include a capacitor, wherein the capacitor is electrically coupled with the interface of the measurement module.

BACKGROUND

In many situations, it is desirable to monitor the voltage of one or more voltage sources, such as batteries. To accurately measure a voltage of a battery, a significant amount of time and/or power may be used. For example, a remote control of a television may use a single AA battery for power. While it may be desirable to determine the voltage of the battery, it may also be desirable to conduct the measurement in a power-efficient manner to conserve the battery's power.

SUMMARY

Various arrangements for determining a voltage of a voltage source using pre-charging are presented. In some embodiments, a system for determining a voltage of a voltage source using pre-charging is present. The system may include a measurement module. The measurement module may include an analog to digital converter, a driver, and/or an interface. The interface may be electrically coupled with the analog to digital converter and the driver. The driver may be configured to output current to charge a capacitor. After a first predefined period of time, the driver may stop outputting current to pre-charge the capacitor. After the driver has stopped pre-charging the capacitor and a second predefined period of time has elapsed, the analog to digital converter is configured to measure a voltage of the capacitor. The system may include a capacitor, wherein the capacitor is electrically coupled with the interface of the measurement module. The system may include a switching module configured to electrically couple the interface of the measurement module and the capacitor with the voltage source at least while the driver is charging the capacitor and the analog to digital converter is measuring the voltage of the capacitor.

Embodiments of such a system may include one or more of the following: The measurement module may further comprise a processing module configured to determine the first predefined period of time using one or more previous measurements of the capacitor's voltage. During the second predefined period of time, the capacitor may be electrically coupled with the voltage source. The first predefined period of time may be selected to charge the capacitor to a median voltage. The system may further include a voltage divider circuit comprising a first resistor and a second resistor. The first resistor may be electrically coupled with the voltage source and the interface. The second resistor may be electrically coupled with the interface. The measurement module may be part of a microcontroller of a remote control. The voltage source may be at least one battery. The measurement module may further comprises a multiplexer. The driver and analog to digital converter may be electrically coupled with inputs of the multiplexer. An output of the multiplexer may be electrically coupled with the interface.

In some embodiments, a method for determining a voltage of a voltage source using pre-charging may be presented. The method may include pre-charging, a capacitor, using a driver, for a first period of time. The method may include after pre-charging, waiting a second period of time. During the second period of time, the capacitor may be electrically coupled with the voltage source. The method may include, after the second period of time, measuring a voltage of the capacitor.

Embodiments of such a method may include one or more of the following: The method may include determining the first period of time to pre-charge the capacitor for a second measurement of the voltage of the voltage source. The method may include coupling the capacitor to the voltage source prior to pre-charging the capacitor using the driver. The method may include uncoupling the capacitor from the voltage source after measuring the voltage of the capacitor. The method may include coupling the capacitor to the voltage source prior to the second period of time, but after substantially pre-charging the capacitor using the driver. The method may include uncoupling the capacitor from the voltage source after measuring the voltage of the capacitor. Determining the first period of time to pre-charge the capacitor for the second measurement of the voltage of the voltage source may comprise using the measured voltage of the capacitor. Pre-charging of the capacitor and measuring the voltage of the capacitor may be performed by a microcontroller unit. The voltage source may be electrically coupled with the capacitor via a voltage divider circuit comprising a first and second resistor. Charging of the capacitor may occur faster using the driver than the voltage source via the voltage divider circuit. The method may include calculating the voltage of the voltage source using the measured voltage of the capacitor and a ratio of the first and second resistors of the voltage divider circuit. The voltage source may be one or more batteries. The measured voltage may be used to provide a user with an indication of a charge level of the one or more batteries.

In some embodiments, a system for determining a voltage of a battery of a remote control using pre-charging is presented. The system may include a transmitter configured to transmit data to a set top receiver. The system may include the set top receiver configured to receive data from the transmitter and store battery charge information. The system may include the remote control. The remote control may include a capacitor, a microcontroller unit (MCU). The MCU may include an analog to digital converter (ADC); and a driver. The driver and the ADC may be electrically coupled with the capacitor. The driver of the MCU may be configured to output current to pre-charge the capacitor. After a first predefined period of time, the MCU may be configured to stop outputting current via the driver to pre-charge the capacitor. After the driver of the MCU has stopped pre-charging the capacitor and a second predefined period of time has elapsed, the ADC of the MCU may be configured to measure a voltage of the capacitor. A switch may be present that is configured to electrically couple the battery with the ADC and the driver of the MCU at least while the driver is charging the capacitor and the analog to digital converter is measuring the voltage of the capacitor. The MCU may be further configured to output an indication of the voltage of the capacitor to the transmitter. The set top receiver may be configured to present battery charge information via a display based on the voltage of the capacitor.

DETAILED DESCRIPTION

In order to measure the voltage of a voltage source, such as a battery, an analog to digital converter may be used to measure an analog voltage and create a digital representation of the voltage. This digital representation of the voltage may be used for purposes such as providing a user an indication of when the battery should be recharged or replaced. While measuring the voltage of such a voltage source may be useful, conducting such a measurement may consume power. As such, it may be desirable to perform such a measurement in a manner that consumes a small amount of power. It may also be desirable to measure voltages of sources that are above the maximum useful range of an analog to digital converter (ADC). Measurements of voltages below the minimum useful range of the analog to digital converter may also be desired, and can be achieved with complementary circuitry. For example, by using a resistive voltage divider with the divider input at the voltage to be measured, the divider common point at the ADC's high reference, and the divider output at the ADC input, voltages below the ADC's low reference can be used as inputs while keeping the ADC input between the high and low references so that meaningful measurements can be taken. The input voltage can then be calculated using the known resister divider ratio. Further, it may be desirable to measure signals at intervals and disable interface circuitry and the ADC between measurements to reduce power consumption when measurements are not being taken.

If the ADC interface is connected for only a short period of time, each sample may be considered individually such that the quantity of charge per sample is the principal determinant of impedance rather than quiescent current. It is in the charge per sample sense that “current” is used in the remainder of the document rather than continuous current. In instances where long term voltages or currents are referenced (in comparison to per-sample quantities), the term quiescent is used.

By using a voltage divider circuit, such as one comprising two high-resistance resistors coupled between the voltage source and ground, a voltage tap can be accessed with only a small amount of power dissipated by the divider. However, in order to measure the voltage using an analog to digital converter (ADC), the ADC may need to draw at least a minimum amount of current. As such, if the effective impedance of the voltage divider circuit is great enough, the voltage determined by the ADC may be inaccurate or a measurement may not be able to be completed by the ADC due to the low level of current supplied by the voltage divider circuit within a sample period.

In order to increase the amount of available current that can be supplied by a high-resistance voltage divider circuit (without decreasing the resistance of the resistors), a capacitor may be added to the voltage divider circuit across the output and common point of the divider. When coupled with the voltage source via the voltage divider circuit, the capacitor, over time, may become charged to the quiescent voltage of the voltage divider circuit. When the ADC is triggered to measure the voltage, both the capacitor and voltage divider. As such, during a voltage measurement, the capacitor may serve as an additional source of current for the ADC to draw from, thus providing sufficient current to the ADC for an accurate voltage measurement. While the capacitor may permit an increased resistance voltage divider circuit to be used, the greater the resistance of the voltage divider circuit, the longer the capacitor may take to charge through the voltage divider circuit. Further, in order for the voltage measurement by the ADC to be accurate, the capacitor needs to be charged to nearly the quiescent voltage divider output, such that the voltage of the capacitor can be used to determine the voltage of the voltage source. As such, time and/or power may be wasted while waiting for the capacitor to be charged by the voltage source through the voltage divider circuit. Voltage measurements using a partially charged capacitor may be used if appropriate processing is applied to the measurement, and if the initial voltage of the capacitor is known, however the accuracy, resolution, and calculation overhead suffer.

Rather than using only the voltage source to charge the capacitor through the voltage divider circuit, another circuit may be used to pre-charge the capacitor. Once pre-charged, the capacitor may be coupled only with the voltage source through the voltage divider circuit (e.g., not coupled with the pre-charging circuit) for a period of time. As such, following the period of time, the voltage of the capacitor may substantially reflect the voltage of the voltage source within the voltage divider circuit (and not the voltage of the circuit used to pre-charge the capacitor). However, since at least some of the charging of the capacitor was conducted using another circuit (which may be configured to charge the capacitor faster by supplying more current and/or by using a higher voltage), the voltage measurement may be conducted sooner and/or with less overall power being consumed than if only the voltage source (through the voltage divider circuit) had been used to charge the capacitor.

Pre-charging of the capacitor may be dynamic. If an approximate voltage of the signal-of-interest is known, the capacitor may be pre-charged to the corresponding voltage. If the pre-charge voltage is fixed, this may be accomplished by adjusting the duration the pre-charge circuitry is enabled. This may decrease the amount of time that the capacitor needs to be coupled with only the signal-of-interest via the voltage divider circuit for the capacitor to accurately reflect the voltage of the signal-of-interest. As such, less power and/or time may be necessary in order to conduct the voltage measurement. The voltage that the capacitor is charged to may be based on a previously conducted voltage measurement. Also, based on a previously measured voltage of the capacitor, the amount of time that the capacitor is coupled with the pre-charge circuit may be adjusted. Charging of the capacitor from a completely discharged state may be necessary for each measurement because the capacitor may be disconnected from the voltage source in order to save power between voltage measurements. For example, voltage measurements may only occur once every few minutes, hours, days, or weeks.

FIG. 1illustrates a block diagram of an embodiment of a system100for determining a voltage of a voltage source using pre-charging. System100includes: voltage source110, switching module120, measurement module130, and capacitor140. Voltage source110, which also may be referred to as a signal-of-interest, supplies power to the other components of system100. Voltage source110is the voltage source that is to have its voltage measured. As such, the voltage output by voltage source110may vary. For example, voltage source110may include one or more batteries (which may be single-use or rechargeable). Over time, the battery may deplete, thus the output voltage may decrease.

Switching module120may serve to alternatively couple and uncouple voltage source110from measurement module130and capacitor140. When voltage source110is uncoupled from measurement module130and capacitor140, measurement module130and/or capacitor140may either consume no power or may consume less power. Switching module120may be various types of switches, such as: a transistor, a MOSFET, or a mechanical switch. Whether the switch couples voltage source110with measurement module130and capacitor140or uncouples voltage source110from measurement module130and capacitor140may be based on an input (not illustrated) to switching module120. The input may receive a trigger signal that controls which state switching module120is in.

Measurement module130measures the voltage of capacitor140. Measurement module130may include a voltage divider circuit. A voltage divider circuit may include two resistors, in series between voltage source110(via switching module120) and a common voltage (such as ground) with the voltage being measured between the two resistors in series and the common voltage. Based on the value of the resistors, the voltage of voltage source110may be calculated. The higher the resistance of the resistors, the less current that will be drawn by the resistors from voltage source110and thus less power is consumed while the divider is enabled. However, in order for measurement module130to conduct an accurate voltage reading, a minimum amount of current may be required to be drawn by measurement module130. Measurement module130may be configured to: 1) measure a voltage; and 2) charge capacitor140. While such functions are illustrated inFIG. 1as being performed by a single measurement module130, separate modules may be used to perform each function.

Measurement module130may comprise a driver that charges capacitor140for a period of time. This driver of measurement module130may be uncoupled from capacitor140for a second period of time. For example, one or more components of measurement module130, such as a driver, may enter a high-impedance mode. While in such a mode, capacitor140may remain connected with voltage source110via switching module120and the voltage divider circuit. As such, during this second period of time, the charge of capacitor140may charge to the voltage of voltage source110. The following example is provided for illustration purposes only. Voltage source110may be 4 V and measurement module130includes a voltage divider circuit having two 100 kilo-ohm resistors. Measurement module130(possibly in conjunction with voltage source110) may be used to quickly charge capacitor140for a first period of time (which may result in the capacitor being charged to, for example, 1.5 V). The driver of measurement module130may be uncoupled from capacitor140for a second period of time. During this second period of time, the capacitor may continue to be charged, by voltage source110, to 2 V. After this second period of time, a voltage measurement circuit of measurement module130may measure the capacitor's voltage as 2 V. Based on this measurement (and knowing at least the ratio of resistance of the two resistors of the voltage divider circuit), the voltage of voltage source110may be calculated to be 4 V. The capacitor may have been charged for a measurement faster and/or with less power loss through the voltage divider circuit than if only voltage source110through the voltage divider circuit was used for charging the capacitor without pre-charging by a driver. Though the capacitor's voltage asymptotically approaches the Thevenin voltage of the voltage supply, once the voltage is within a measurement resolution, the calculated voltage is sufficiently close to 4 V.

Capacitor140may represent one or more capacitors. Capacitor140may be coupled with measurement module130. Capacitor140may be coupled with ground (not illustrated).

FIG. 2illustrates another block diagram of an embodiment of a system200for determining a voltage of a voltage source using pre-charging. System200may represent a more detailed embodiment of system100, or may represent a separate system. Voltage source110, switching module120, and capacitor140may be as described in relation to system100ofFIG. 1. Measurement module130may comprise subcomponents: driver module210, analog to digital converter (ADC)220, and interface230.

Driver module210may be used to pre-charge capacitor140to accelerate charging performed by voltage source110via interface230. When active and coupled with capacitor140, driver module210may provide more current to charge capacitor140than voltage source110via interface230alone. When driver module210is charging capacitor140, voltage source110, via interface230, may also be charging capacitor140, or, in some embodiments, only driver module210may be used to charge capacitor140. Driver module210may be a digital driver configured to output a voltage similar to voltage source110. Indeed, power for driver module210may be supplied by voltage source110, as such, the maximum voltage supplied by driver module210may be the voltage of voltage source110. The voltage supplied by driver module210to capacitor140may be greater than the voltage supplied to capacitor140by voltage source110via the voltage divider circuit.

ADC220may be used to measure the voltage of capacitor140. ADC220may be required to draw a minimum amount of current in order to perform an accurate voltage measurement. ADC220may receive, as an input, a voltage from capacitor140via interface230. ADC220may create a digital representation of the magnitude of this voltage. The digital representation may be output to another component. The digital representation may be used to calculate the voltage of voltage source110and/or may be output to some other device, such as for presentation to a user or to an administrative service that monitors a voltage (such as a battery voltage) in multiple devices. Such an administrative service may performed locally or remotely from the device that has the voltage being monitored.

Interface230may serve to couple driver module210and ADC220to capacitor140(and, possibly, voltage source110via switching module120). Interface230may include a voltage divider circuit. Interface230may permanently connect driver module210, ADC220, and capacitor140with each other (e.g., interface230comprises a trace or wire connecting the three components). Interface230may be configured to alternatively couple and uncouple driver module210and ADC220with capacitor140. For example, while driver module210is connected with capacitor140, ADC220may not be coupled with capacitor140; while ADC220is coupled with capacitor140via interface230, driver module210may be uncoupled from capacitor140.

FIG. 3illustrates a circuit diagram of an embodiment of a system300for determining a voltage of a voltage source using pre-charging. System300may represent a more detailed embodiment of system100and/or system200, ofFIGS. 1 and 2, respectively. System300may also represent a separate system. System300may include: voltage source110, switch310, trigger input320, voltage divider circuit330, multiplexer340, ADC220, driver module350, and capacitor140.

Voltage source110may be coupled with switch310. Switch310may represent switching module120ofFIGS. 1 and 2, or some component thereof. Switch310may be a transistor, such as a bipolar junction transistor (BJT), as illustrated in system300. Switch310, as illustrated, may be an NPN BJT. As such, when a sufficiently great enough voltage is applied to trigger input320(which is connected to the gate of the BJT), voltage source110is coupled with voltage divider circuit330. If a sufficiently low enough voltage is applied to trigger input320or no voltage is applied, voltage source110may not be coupled with voltage divider circuit330. For example, when a measurement of the voltage of voltage source110does not need to be performed, voltage source110may remain uncoupled from voltage divider circuit330, thus reducing power consumption. In other embodiments, a PNP BJT may be used. In such embodiments, a sufficiently low enough voltage may be applied to trigger input320to couple voltage source110to voltage divider circuit330. A sufficient high enough voltage applied to trigger input320may uncouple voltage source110from voltage divider circuit330.

Interface230ofFIG. 2may be represented inFIG. 3by voltage divider circuit330and multiplexer340. Voltage divider circuit330may comprise two resistors. Resistors with a high resistance may be used to decrease power consumption. For example, 100 k ohm resistors may be used. The resistance of each resistor (or a known ratio between the resistance of the resistors) may be used to calculate the voltage of voltage source110using a voltage measured between the two resistors of voltage divider circuit330. As those with skill in the art will recognize, a voltage divider circuit may be constructed using various numbers of resistors.

Multiplexer340may serve to connect ADC220and driver350(which may represent driver module210or some component thereof) to voltage divider circuit330. An input to multiplexer340(not illustrated) may select whether ADC220or driver350is connected with voltage divider circuit330. In some embodiments, only one of ADC220or driver350is connected with voltage divider circuit330at a particular time. Multiplexer340may be used to connect driver350to voltage divider circuit330for a period of time. While driver350is connected to voltage divider circuit330, driver350may be used to charge capacitor140. While driver350is charging capacitor140, capacitor140may also be being charged by voltage source110via switch310and voltage divider circuit330. After a period of time, driver350may stop charging capacitor140and/or multiplexer340may disconnect driver350from voltage divider circuit330and capacitor140. Multiplexer340may disconnect driver350and couple ADC220to voltage divider circuit330and capacitor140. After a second period of time, ADC220may measure the voltage of capacitor140.

In system300, ADC220, driver350, and multiplexer340may be discrete components. In some embodiments, one or more of these components may be combined. For example, a microcontroller unit (MCU) may contain driver350and ADC220.

FIG. 4illustrates another circuit diagram of an embodiment of a system400for determining a voltage of a voltage source using pre-charging. System400may represent a more detailed embodiment of system100, system200, and/or system300ofFIGS. 1,2, and3, respectively. System400may also represent a system separate from systems100through300.

In system400, MCU410may include ADC220and driver350. Rather than using a multiplexer, interface230of system400comprises electrical coupling (e.g., wiring) ADC220and driver350together. For example, this may include connecting two pins of MCU410together. When driver350is not charging capacitor140, driver350may be in a high impedance state such as not to affect operation of ADC220. Likewise, when not in use, ADC220may remain in a high impedance state as to not affect driver350. MCU410may control when driver350and ADC220are active. In some embodiments, trigger input320may be generated by MCU410. MCU410may be configured with an amount of time which capacitor140should be charged and a second period of time in which capacitor140should remain coupled with voltage source110before ADC220is used to measure the voltage of capacitor140. MCU410may also be configured to calculate the voltage of voltage source110using one or more measurements by ADC220. The amount of time which driver350charges capacitor140may be varied by MCU410based on one or more previous voltage measurements performed by ADC220.

The remainder of system400, including voltage source110, switch310, trigger input320, voltage divider circuit330, and capacitor140may remain unchanged from system300ofFIG. 3. MCU410may be configured to perform other functions in addition to those of driver350and ADC220.

FIG. 5illustrates yet another circuit diagram of an embodiment of a system500for determining a voltage of a voltage source using pre-charging. In system500, an embodiment of system400is implemented within remote control530. Remote control530may be used to control some other device, such as a television or a set top box. Onboard remote control530, battery540serves as the voltage source. As such, the voltage of battery540may be monitored, at least periodically, to determine whether battery540should be replaced or recharged. In addition to components of system400, MCU410may be coupled with transmitter550. The transmitter may be collocated with the MCU, for example on the same circuit board, within the same package, or even on the same chip die.

Coupling of ADC220and driver350may occur onboard MCU410. As such, interface230may comprise a single pin of MCU410. Depending on whether ADC220or driver350is active, the other component may be in a high impedance state. Control of which component is active at a given time may be controlled by MCU410.

Transmitter550may be configured to transmit data to receiver510. Receiver510may be part of a television or a set top box. Transmitter550may be configured to transmit data such as an indication that the channel should be changed or the volume should be adjusted to receiver510. Transmitter550may also be configured to transmit data related to the voltage of battery540. This data may be received by receiver510, processed, and presented to a user via display520. For example, when the voltage of battery540decreases to below a threshold voltage, a warning indicator may be presented to the user via display520that indicates the battery (or batteries) needs replacing or recharging.

In some embodiments, a user may provide input triggering a battery voltage measurement. Such input may trigger a voltage measurement. In some embodiments, the user may be presented with data from the most recent previous voltage measurement. In other embodiments, the receiver510may trigger a voltage measurement by transmitting an indication to the remote.

Systems100through500ofFIGS. 1-5, respectively, may be used to perform various methods.FIG. 6illustrates an embodiment of a method600for determining a voltage of a voltage source using pre-charging. Method600may be performed by each of systems100though500. Alternatively, method600may be performed by some other system for measuring a voltage of a voltage source using pre-charging.

At step610, a voltage source may be coupled with a capacitor. The voltage source may be the voltage source that is desired to be measured. The capacitor may be used to provide sufficient current to the component conducting the voltage measurement to allow for an accurate measurement. Referring to system400, the voltage source may be voltage source110and the capacitor may be capacitor140. Electrically coupling a voltage source110to capacitor140may include closing a switch, such as switch310to allow current from voltage source110to charge capacitor140. Voltage source110may be coupled with capacitor140via one or more other circuits, such as voltage divider circuit330.

At step620, the capacitor may be charged using a driver. This charging, because it refers to charging occurring before only the capacitor and the voltage source are coupled, may be referred to as pre-charging. The driver may provide more current and/or a higher voltage than the voltage source thus charging the capacitor quicker than only the voltage source via the voltage divider circuit. Referring again to system400ofFIG. 4, driver350may be used to at least partially charge capacitor140. Driver350may charge capacitor140faster then voltage source110. This may be due to the increased resistance between voltage source110and capacitor140and/or because driver350may be configured to apply a greater voltage to capacitor140, thus increasing the voltage of capacitor140faster. While driver350is charging capacitor140, voltage source110may also be coupled with capacitor140. Having both voltage source110and driver350coupled with capacitor140may further decrease the charge time of capacitor140. In some embodiments, only driver350(and not voltage source110) may be coupled with capacitor140for charging. The amount of time the driver is used to charge the capacitor may be based on a median amount of time that is expected to be needed to charge the capacitor to the voltage expected in the voltage divider circuit. For example, if the voltage source is expected to typically be in the range of 2 V to 4 V as measured in the voltage divider circuit, the driver may be used to charge the capacitor to 3 V. After the pre-charge period of step620, the driver is disconnected or otherwise disabled, and the voltage source alone is connected to the capacitor for a sufficient settling time at step625(based on required measurement resolution and other system parameters).

At step630, the voltage of the capacitor may be measured. An accurate measurement may be conducted after a shorter charging time because the driver was used to at least partially charge the capacitor rather than only using the voltage source via a voltage divider circuit. If only the voltage source was used to charge the capacitor via the voltage divider circuit, a greater amount of time and/or power (due to system overhead) may be consumed during the charging process. When the voltage of the capacitor is measured, the capacitor may have reached, at least approximately, a steady-state voltage that is representative of the voltage of the voltage source. As such, by being representative of the voltage of the voltage source, the voltage of the capacitor may be used to calculate the voltage of the voltage source. For example, since the capacitor may be coupled with a voltage divider circuit, the voltage of the capacitor in conjunction with a ratio of the resistance of the resistors of the voltage divider circuit may be used to calculate the voltage of the voltage source. In some embodiments, no calculation of the voltage of the voltage source may be necessary, rather, the voltage of the capacitor may be used directly to determine whether the voltage source is in need of recharging or replacing. Referring to system400, the measurement may be conducted by an analog to digital converter, such as ADC220. Such an ADC may require more current than is available via voltage divider circuit330. As such, capacitor140allows an increased amount of current to be drawn by ADC220to permit an accurate voltage measurement to be conducted.

At step640, the voltage source may be uncoupled from the capacitor. As such, the capacitor may discharge through the voltage divider circuit to ground and the capacitor may become completely discharged. Once the voltage source has been uncoupled from the capacitor and the remainder of the circuit, no or little power may be consumed until another voltage measurement is to be conducted. Referring to system400, voltage source110may be uncoupled from voltage divider circuit330, capacitor140, ADC220, and driver350by opening switch310. The state of switch310may be controlled by trigger input320.

FIG. 7illustrates another embodiment of a method700for determining a voltage of a voltage source using pre-charging. Method700may be performed by each of systems100though500ofFIGS. 1-5, respectively. Alternatively, method700may be performed by some other system for measuring a voltage of a voltage source using pre-charging. At step710, input may be received that triggers a voltage measurement. This input may be received from the user (e.g., by pressing a button on a remote control) or may be generated periodically such as by an MCU (e.g., a voltage measurement may be conducted once per day).

At step720, the voltage source may be coupled with a capacitor. The voltage source may be the voltage source that is desired to be measured. The capacitor may be used to provide sufficient current to the component conducting the voltage measurement to allow for an accurate measurement. In some embodiments, more than one capacitor may be used. For example, multiple capacitors may be placed in parallel to increase the overall capacitance. Referring to system400, the voltage source may be voltage source110and the capacitor may be capacitor140. Voltage source110may represent one or more batteries. Coupling voltage source110to capacitor140may include closing a switch, such as switch310, to allow current from voltage source110to charge capacitor140. Closing switch310may include holding trigger input320high while voltage source110is to be electrically coupled with capacitor140. Voltage source110may be electrically coupled with capacitor140via one or more other circuits, such as voltage divider circuit330. The amount of current flowing from voltage source110to capacitor140and/or the voltage at capacitor140may be affected by other components of the circuit, such as voltage divider circuit330and/or switch310. For example, the current and voltage available to charge capacitor140may be affected by the resistance of the resistors of voltage divider circuit330.

At step730, a driver may be used to at least partially charge the capacitor. At least while the capacitor is being charged, the ADC may be uncoupled from the capacitor and/or placed in a high-impendence state. The driver may provide more current and/or a higher voltage than the voltage source via the switch and voltage divider circuit. Referring again to system400ofFIG. 4, driver350may be used to at least partially charge capacitor140. Driver350may charge capacitor140faster than voltage source110alone. This may be due to the increased resistance between voltage source110and capacitor140and/or because driver350may be configured to apply a greater voltage to capacitor140, thus increasing the voltage of capacitor140faster. While driver350is charging capacitor140, voltage source110may also be coupled with capacitor140. Having both voltage source110and driver350coupled with capacitor140may decrease the charge time of capacitor140. In some embodiments, only driver350(and not voltage source110via the voltage divider circuit) may be coupled with capacitor140for charging.

The amount of time which the driver is used to charge the capacitor may be predefined. For example, the first predefined period of time may be an amount of time that is expected to charge the capacitor to a minimum threshold voltage. If the voltage at the capacitor is below the minimum threshold voltage, it may be expected that a circuit, such as an MCU, may not be able to operate using the voltage source for power. As such, if a voltage measurement is to occur, the voltage at the capacitor may be reasonably expected to always be at least the minimum threshold voltage. In some embodiments, the first predefined period of time used to charge the capacitor may be based on one or more previous voltage measurements of the capacitor. The driver may be used to charge the capacitor to the voltage of the previous measurement. In some embodiments, the driver may be used to charge the capacitor to a voltage based on the previous measurement, such as 95% of the previous measurement. While the driver is charging the capacitor, the voltage source may also be coupled with the capacitor via a switch and the voltage divider circuit. Having the voltage source also coupled with the capacitor may speed charging of the capacitor.

After the capacitor has been at least partially charged using the driver at step730, a second predefined period of time without the driver charging the capacitor may elapse at step740. During the second predefined period of time, the capacitor may remain coupled with the voltage source via a voltage divider circuit and the switch. During this second period of time, the voltage of the capacitor will charge or discharge from the voltage the capacitor was charged to using the driver to the voltage created by the voltage source through the voltage divider circuit. The amount of time for the voltage of the capacitor to at least approximately represent the voltage of the voltage source (as affected by the voltage divider circuit) may be decreased due to the capacitor being at least partially charged by the driver circuit. For example, if the driver circuit charged the capacitor to 2.2 V, and the voltage created by the voltage source on the voltage divider circuit (between the resistors) is 2.5 V, it may take a shorter period of time to charge from 2.2 V to 2.5 V, than from 0 V to 2.5 V (which may have occurred if no driver circuit was used to pre-charge the capacitor. As such, by using the driver to pre-charge the capacitor, the amount of time for the capacitor to accurately reflect the voltage of the voltage source via the voltage divider circuit and/or the total power consumed to perform the measurement may be decreased. The second predefined period of time may be a stored, predefined period of time. For example, a certain number of milliseconds may always be waited after the driver has stopped charging the capacitor before the voltage of the capacitor is measured to allow the capacitor to accurately reflect the voltage of the voltage source via the voltage divider circuit. This second predefined period of time may be stored by a module, such as an MCU. Referring to system400ofFIG. 4, MCU410may pre-charge capacitor140using driver350. Driver350may then enter a high impedance state. Before ADC220is used to conduct a measurement of the voltage of capacitor140, the second predefined period of time may be waited by MCU410.

At step750the voltage of the capacitor may be measured. At least during step750, the driver may be uncoupled from the capacitor and/or placed in a high impedance state. When the voltage of the capacitor is measured at step750, the voltage of the capacitor may accurately represent the voltage of the voltage source as affected by the voltage divider circuit. As such, by measuring the voltage of the capacitor, the voltage of the voltage source may be calculated. The measurement of the voltage may be conducted sooner since the driver was used to at least partially charge the capacitor. If only the voltage source was used to charge the capacitor via the voltage divider circuit, a greater amount of time and/or power may be consumed during the charging process. Referring to system400, the measurement may be conducted by ADC220. ADC220may require more current than can be drawn via voltage divider circuit330. As such, capacitor140allows an increased amount of current to be drawn by ADC220while allowing an accurate voltage measurement to be conducted.

At step760, the voltage source may be uncoupled from the capacitor. As such, the capacitor may discharge through the voltage divider circuit to ground so that the capacitor completely discharges. Once the voltage source has been uncoupled from the capacitor and the remainder of the circuit, no or little power may be consumed until another voltage measurement is to be conducted. Referring to system400, voltage source110may be uncoupled from voltage divider circuit330, capacitor140, ADC220, and driver350by opening switch310. The state of switch310may be controlled by trigger input320, which may be coupled with MCU410or some other controller circuit.

At step770, since the capacitor may have been coupled with a voltage divider circuit, the previously measured voltage of the capacitor in conjunction with a ratio of the resistance of the resistors of the voltage divider circuit may be used to calculate the voltage of the voltage source. In some embodiments, no calculation of the voltage of the voltage source may be necessary, rather, the previously measured voltage of the capacitor may be used directly to determine whether the voltage source is in need of recharging or replacing. The measurement conducted by ADC220may be used by MCU410to compute the voltage of voltage source110(MCU410may store a ratio of the resistance of the resistors or a ratio of the resistance of the resistors of the voltage divider circuit). The computed voltage, or the raw measurement by ADC220, may be transferred to one or more other components.

At step780, the first predefined period of time that is used to charge the capacitor using the driver for the next measurement may be determined based on the previously measured voltage of the capacitor, or upon the computed voltage. The computed voltage or the raw measurement by ADC220may be stored by MCU410. This computed voltage or the raw measurement may be used to determine the amount of time driver350should be used to charge capacitor140for the next voltage measurement. As such, MCU410may store an amount of time to be used for pre-charging by the driver of the capacitor for the next measurement. Following step780, at some point in the future, another voltage measurement may be conducted. In this next measurement, the determined first period of time may be used to charge the capacitor by the driver.

FIG. 8illustrates yet another embodiment of a method for determining a voltage of a voltage source using pre-charging. Method800may be performed by each of systems100though500. Alternatively, method800may be performed by some other system for measuring a voltage of a voltage source using pre-charging. Steps810and820correspond to steps710and720of method700ofFIG. 7.

At step830, a driver may be used to at least partially charge the capacitor. The driver may provide more current and/or a higher voltage than the voltage source via the switch and voltage divider circuit. Referring again to system400ofFIG. 4, driver350may be used to at least partially charge capacitor140. Charging may occur similarly to charging in step730of method700. The voltage the driver is used to charge the capacitor to may be predefined. This voltage may be defined based on one or more previous measurements. The voltage the capacitor is to be charged to may be used to calculate a period of time which the driver should charge the capacitor. For example, an MCU may be able to calculate or may access a look-up table to determine an amount of time that the capacitor should be pre-charged by the driver in order to obtain the predefined voltage.

Steps840through870correspond to steps740through770of method700ofFIG. 7. At step880, the predefined voltage for charging the capacitor may be determined and stored for the next voltage measurement. The voltage may be the voltage measured by the ADC at step850. In some embodiments, some percentage of the measured voltage is used, such as 95%. This voltage may be stored and used for charging the capacitor for a future voltage measurement.