Boost converter circuit

Abstract

A boost converter circuit is disclosed, comprising: an input arranged to receive an input voltage from a battery; an output arranged to generate a higher output voltage to power another circuit portion; and a switching device arranged to control the generation of the output voltage. The boost converter circuit compares an input voltage to a first reference input voltage and controls the switching device to limit an output current of the boost converter circuit based on the comparison of the input voltage to the first reference input voltage. The boost converter circuit monitors a parameter indicative of a battery condition, determines a lower second reference input voltage in response to the monitored parameter, compares the input voltage to the second reference input voltage, and controls the switching device to limit an output current of the boost converter circuit based on the comparison of the input voltage to the second reference input voltage.

Description

Background of the Invention

[0001] The present invention relates to boost converter circuits and related circuits.

[0002] Electronic devices are often powered using a direct current (DC) power source, such as a battery. In many cases, the no-load (also called nominal) voltage of the power source does not match one or more voltage requirements of the electronic device and can also vary depending on the age of the power source, its state of charge, and / or environmental conditions, such as temperature. For example, a particular single-cell battery may generate a no-load voltage between 1.5 V and 1.7 V when it is fully charged, and between 0.9 V and 1.1 V when it is almost fully discharged. Many electronic devices often require higher voltages to operate, such as 3 V or 5 V.

[0003] Some devices utilize a boost converter (also known as a step-up converter) to boost the input voltage (e.g., from a low-voltage battery) to a higher output voltage suitable for operating the device, while correspondingly reducing the input current to a lower output current. Conservation of energy dictates that the input and output voltages and currents of a boost converter are related according to the following equation:

[0004]

[0005] Among them I in ,I out 、V in and V out are the input and output current and voltage, and K is the efficiency of the boost converter.

[0006] The current demands of a device can vary over time (for example, as the device performs different functions or enters different power modes). Therefore, the boost converter must be able to provide different amounts of output current at different times.

[0007] Typically, a boost converter is controlled to maintain a target output voltage. For example, if the current demand of a device powered by the boost converter increases, the output voltage will momentarily drop, which can be detected and compensated for (i.e., by drawing a greater input current from the input source via the boost converter). However, this approach may not be optimal for power sources with relatively low current capabilities (e.g., low capacity batteries) because simply drawing more current from these sources may cause the input voltage to drop (e.g., due to a voltage drop across a non-zero internal resistance), which can actually cause the output current to drop (see equation (1) above). Furthermore, for devices seeking to minimize energy usage (e.g., battery-powered devices seeking to maximize battery life), the losses in internal resistance are undesirable.

[0008] An improved boost converter control method may be needed. Summary of the invention

[0009] According to a first aspect of the present invention, there is provided a boost converter circuit, comprising: an input terminal configured to receive an input voltage from a battery; an output terminal configured to generate a higher output voltage to power another circuit portion; and a switching device configured to control generation of an output voltage; The boost converter circuit is configured as: comparing the input voltage to a first reference input voltage; controlling the switching device to limit an output current of the boost converter circuit based on a comparison of the input voltage with a first reference input voltage; monitoring parameters indicative of battery condition; determining a second, lower reference input voltage in response to the monitored parameter; comparing the input voltage to a second reference input voltage; and Based on a comparison of the input voltage with a second reference input voltage, the switching device is controlled to limit an output current of the boost converter circuit.

[0010] Therefore, it will be appreciated by those skilled in the art that the operation of the boost converter circuit can be made more reliable and optimized by controlling its switch device in response to the input voltage. In addition, the boost converter circuit is able to use the energy stored in the battery more optimally because the way the switch device is controlled takes into account the condition of the battery (via the second reference input voltage).

[0011] As described above, the input and output voltages and currents of the boost converter circuit are related according to equation (1). The voltage V provided by the power supply in and current I in , its no-load operating voltage V unl Its internal resistance R int According to the following equation:

[0012]

[0013]

[0014] Combining equations (1) and (3), this means that the output current I out can be expressed as:

[0015] Therefore, it can be seen that for a constant output voltage V out , no-load voltage V unl and internal resistance R int, output current I out is the input voltage V in is a nonlinear function of . Therefore, controlling the boost converter circuit based on the input voltage can allow for more optimal control of the output current than conventional methods. For example, if no mitigation measures are taken, the input voltage of a battery (e.g., a low-capacity battery) will depend on the current drawn and the internal resistance (e.g., as I in The increase of V in The output current may be reduced (which may be reduced) and drop significantly from the no-load value. Controlling the boost converter circuit based on the input voltage may allow this effect to be monitored and taken into account. For example, this may allow the boost converter circuit to be controlled to generate an output current optimized for long battery life.

[0016] Additionally, as the battery ages and / or discharges, its internal characteristics (e.g., internal resistance and / or no-load voltage) change. The condition of the battery may represent an assessment of one or more of these internal characteristics. As the battery ages and discharges, the condition of the battery generally deteriorates. Determining the second reference input voltage in response to a parameter indicative of the condition of the battery allows these changes to be taken into account when controlling the operation of the switching device. In other words, this may allow the operation of the boost converter circuit to be optimized even if the condition of the battery changes. For example, the switching device may operate in response to a comparison of the input voltage to the second reference input voltage in such a manner that a desired output voltage and current are maintained even if the condition of the battery changes. This may allow more energy to be usefully extracted from the battery over the useful life and / or charging cycle of the battery compared to previous methods that do not take into account parameters indicative of the condition of the battery.

[0017] The boost converter circuit may be configured to control the switch device to limit the output current of the boost converter circuit if the input voltage is equal to (or approximately equal to) or less than the first and / or second reference input voltage. In other words, the switch device may be operated to maintain the input voltage at or above the first and / or second reference input voltage. The switch device may be configured to suspend the operation of the boost converter circuit if the input voltage is equal to or less than the first and / or second reference input voltage.

[0018] The boost converter circuit may include an input comparator arranged to compare the input voltage with the first and / or second reference input voltage.For example, the input comparator may be arranged to receive the input voltage and the first and / or second reference input voltage as input.

[0019] The boost converter may include a separate input comparator for each reference input voltage. However, in one set of embodiments, a single input comparator is used to compare the input voltage with the first reference input voltage and the second reference input voltage. For example, the boost converter circuit may be configured to change the input of the input comparator from the first reference input voltage to the second reference input voltage. The boost converter circuit may include a multiplexer configured to output the first or second reference input voltage in response to a monitored parameter (e.g., in response to the output voltage). The output of the multiplexer may be connected to the input of the input comparator.

[0020] The second reference input voltage can be determined in response to a degradation in the battery condition indicated by the monitored parameter. This can allow more useful energy to be extracted from the battery when the battery condition deteriorates. For example, equation (4) can be rearranged to yield:

[0021]

[0022] As the battery condition deteriorates (e.g., as the battery ages and / or discharges), its internal resistance R int will increase. If the input voltage is maintained at or above a constant reference level during this degradation period, equation (6) shows that the increase in internal resistance will require a corresponding reduction in output current and / or a reduction in output voltage. Neither of these situations is ideal for maintaining normal operation of another circuit portion. However, when the monitored parameter indicates that the battery condition is deteriorating, the desired output current and output voltage can be maintained by using a lower second reference input voltage. In other words, it is allowed to increase during the internal resistance R int When the input voltage increases, I out and V out Stays on longer.

[0023] Parameters indicative of battery condition may include a state of health (SOH) indicator or a state of charge (SOC) indicator. The parameter may include the internal resistance or no-load voltage of the battery.

[0024] However, in one set of embodiments, the parameter indicative of the battery condition is the output voltage. The boost converter circuit can be configured to measure the output voltage. As shown in equation (5) above, the output voltage can indicate the condition of the battery because, if not mitigated, the output voltage will decrease as the internal resistance increases. Monitoring the output voltage can be relatively easy to implement. In addition, controlling the boost converter circuit in response to the output voltage rather than another parameter indicative of the battery condition can be particularly advantageous because regulating the output voltage is often important (e.g., keeping it above the minimum operating voltage of another circuit portion). Controlling the boost converter circuit in response to the output voltage can allow undesirable changes in the output voltage to be corrected more quickly than control based on another indicator of the battery condition.

[0025] Monitoring a parameter may include comparing the parameter to a threshold value. For example, the boost converter circuit may be configured to compare the input voltage to a first reference input voltage or a second reference input voltage in response to the monitored parameter crossing a threshold value. For example, the boost converter circuit may be configured to compare the input voltage to a first reference input voltage when the monitored parameter is above a threshold value, and to compare the input voltage to a second reference input voltage when the monitored parameter is below a threshold value (e.g., when the parameter indicates that the battery condition has deteriorated to a certain level). The threshold value may be selected based on known characteristics of the battery and / or another circuit portion. In one set of embodiments, the threshold value is a threshold output voltage that is equal to or slightly higher (e.g., 1%, 5%, 10%, or 20% higher, or 0.1 V, 0.2 V, or 0.5 V higher) than the minimum operating power supply voltage of another circuit.

[0026] Additionally or alternatively, monitoring the parameter may include measuring the parameter.The second reference input voltage may be determined using the measured parameter, for example, the second reference input voltage may be a function of the measured parameter.

[0027] The boost converter circuit can be configured to generate an alarm in response to the monitored parameter. For example, the boost converter circuit can be configured to generate an alarm if the parameter (e.g., the output voltage) exceeds a threshold that triggers determination of the second reference input voltage. The alarm can include an indication of the battery condition. For example, the alarm can include a low battery warning or a suggestion to replace and / or charge the battery. The boost converter circuit can be configured to send the alarm to another circuit portion (e.g., to trigger a low battery mode or a sleep mode).

[0028] For example, controlling the boost converter circuit based on the input voltage can allow the current output by the boost converter to be maximized. This may be ideal for applications that require large currents from a small battery. For example, the first or second reference input voltage can be selected so that the switching device limits the output current of the boost converter circuit when the input voltage indicates that the output current is near or at a maximum value. In other words, when the input voltage has dropped to a value indicating that the output current is at its maximum possible level, the boost converter circuit can be prevented from attempting to deliver a higher current.

[0029] when When , the maximum value of equation (5) occurs. In other words, the theoretical maximum output current of the boost converter occurs when the input voltage drops to half of its no-load value. Therefore, the first and / or second reference input voltage may be equal to half or approximately half of the no-load battery voltage (e.g., between 35% and 65% of the no-load battery voltage or between 45% and 55% of the no-load battery voltage). Preferably, the first and / or second reference input voltage is not less than half of the no-load battery voltage.

[0030] However, in many battery powered devices, it may be desirable to maximize the available energy extracted from the battery, e.g., to maximize battery life. In such applications, controlling the boost converter to extract the maximum current from the battery may not be optimal, as this may result in inefficiencies, such as large resistive losses across the internal resistance of the battery. Therefore, in one set of embodiments, the first and / or second reference input voltages may be selected such that the output current of the boost converter circuit is limited to a level below the maximum possible output current of the boost converter circuit. For example, the first and / or second reference input voltages may be equal to more than half of the no-load battery voltage (e.g., more than 51% of the no-load battery voltage, more than 60% of the no-load battery voltage, or more than 70% of the no-load battery voltage). As can be seen from equation (5), setting the first and / or second reference input voltages equal to more than half of the no-load battery voltage and controlling the switch device to limit the output current so that the input voltage does not drop below the reference input voltage means that the output current is artificially limited to a level below the maximum possible output current. This may allow more energy to be extracted from the battery, as less energy is lost to resistive losses across the internal resistance of the battery.

[0031] In some embodiments, the boost converter circuit includes one or more input capacitors connected in parallel with the input terminal. In some embodiments, the boost converter circuit includes one or more output capacitors connected in parallel with the output terminal. The input and output capacitors can act as charge reservoirs for moments of high current demand. For example, providing one or more output capacitors can allow the current required by another circuit portion to be met for a short period of time, even if the maximum allowed output current of the boost converter circuit is less than the instantaneous current required by the other circuit portion. This can help to extract more useful energy from the battery because a lower current (with lower associated resistive losses) can be drawn from the battery over a longer period of time, the capacitors make up for any current shortfall at moments of high demand, and then charge with a lower current.

[0032] As described above, switching from a first reference input voltage to a second reference input voltage may allow more energy to be extracted from the battery as the battery ages and discharges. In some embodiments, switching to a third reference input voltage may be useful as the battery condition further degrades. Therefore, in one set of embodiments, the boost converter circuit is configured to: determine a third reference input voltage in response to a monitored parameter, compare the input voltage to the third reference input voltage; and control the switch device to limit the output current of the boost converter circuit in response to the comparison of the input voltage to the third reference input voltage.

[0033] The third reference input voltage may be lower than the second reference input voltage, ie to allow more energy to be extracted from the battery. In some embodiments, a lower reference input voltage may be used in a similar manner.

[0034] It will be appreciated that the no-load battery voltage refers to the terminal voltage output by the battery when it is not subjected to any load. The no-load battery voltage may also vary over time, for example depending on the age of the battery, its state of charge and / or environmental conditions (e.g., temperature). Therefore, while the no-load battery voltage (at least in some cases) may be a useful indicator for selecting the first and / or second reference input voltages in order to adjust the current output, in practice the boost converter circuit may not know the no-load battery voltage. For example, the boost converter circuit may be designed to work with several different batteries having different no-load battery voltages, and the no-load battery voltage itself may vary depending on local environmental conditions, its state of charge, its age and / or other operating parameters.

[0035] In some embodiments, the boost converter circuit may be configured to estimate and / or directly measure the no-load battery voltage. In such embodiments, the no-load battery voltage may include a parameter indicating the battery state. However, the additional circuitry required for this may be prohibitive. Therefore, in some embodiments, additionally or alternatively, the first and / or second reference input voltage (and / or other reference input voltage) has a predetermined value. The predetermined value may be selected based on the expected characteristics of the battery. Although the use of a fixed reference input voltage may not always be strictly optimal, the applicant has recognized that it can provide good performance for a wide range of battery voltages while being easier to implement than actively measuring the no-load battery voltage.

[0036] The present invention extends to a circuit system comprising: a battery configured to generate an input voltage; and A boost converter circuit as disclosed herein, wherein the input terminal is connected to an input voltage generated by a battery.

[0037] The present invention may be particularly applicable to low capacity batteries, i.e. batteries for which minimizing energy loss may be important. The battery may include a low capacity battery, such as a battery having a nominal capacity of less than 2000 mWh, less than 1000 mWh, less than 500 mWh, or less than 250 mWh. The battery may include a button cell or coin cell, such as a CR2032 battery.

[0038] The circuit system may include another circuit portion (e.g., a system on a chip) connected to the output terminal. The other circuit portion may have a minimum operating voltage. The second reference input voltage may be determined in response to the monitored parameter to keep the output voltage above the minimum operating voltage.

[0039] Features of any aspect or embodiment described herein may be applied to any other aspect or embodiment described herein where appropriate.When different embodiments are mentioned, it should be understood that these embodiments are not necessarily different, but may overlap. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a circuit system according to an embodiment of the present invention; Figure 2 and Figure 3 It is shown Figure 1 A timing diagram of the operation of the circuit portion in FIG. Figure 4 is a schematic diagram of a circuit system according to another embodiment of the present invention; and Figure 5 It is shown Figure 4 A timing diagram of the operation of the circuit portion. DETAILED DESCRIPTION

[0041] Figure 1 A circuit system 100 is shown, which includes a battery 102, a boost converter circuit 104, and a system on a chip (SoC) 108. The battery 102 and the boost converter 104 together power the SoC 108. As will be explained in more detail below, the boost converter circuit 104 receives an input voltage V DDL , and provides a higher output voltage V to SoC 108 DD SoC 108 requires a minimum operating voltage V of 1.7V DDRESET .

[0042] SoC 108 requires a voltage between 1.8V and 3.6V to operate. To allow for a small margin of error, SoC 108 specifies a minimum voltage V of 2V. DDMIN The battery 102 has a non-zero internal resistance R int and no-load voltage V unl . R int and V unl Varies depending on the state of charge of the battery 102 and the age of the battery 102. unl Usually between 1.1V and 1.7V. Internal resistance R int Usually around 20Ω.

[0043] SoC 108 is connected in parallel with first decoupling capacitor 110 and second decoupling capacitor 112 to output voltage V DDThe second decoupling capacitor 112 has a larger capacitance than the first decoupling capacitor 110. During normal operation, the decoupling capacitors 110, 112 "decouple" the SoC 108 from any noise in the power supply provided by the boost converter circuit 104, and also provide a charge reservoir to meet the momentary higher current demands of the SoC 108. Similarly, the boost converter circuit 104 itself is connected to the battery 102 in parallel with a battery decoupling capacitor 114. The battery decoupling capacitor 114 also acts to smooth noise and acts as a charge reservoir for the boost converter circuit 104.

[0044] The boost converter circuit 104 includes a voltage source connected to an input voltage V DDL The inductor 116, the switching device 118, the boost control circuit part 120 and the input voltage control part 121 are provided.

[0045] The boost control circuit portion 120 controls the operation of the switch device 118. The switch device 118 includes a first switch 122 operable to connect the inductor 116 to ground and a second switch 124 operable to connect the inductor 116 to the output terminal of the boost converter 104.

[0046] The boost control circuit section 120 receives inputs from a first comparator 126 and a second comparator 128. The first comparator 126 converts the input voltage V DDL It is compared with the reference input voltage provided by the input voltage control part 121.

[0047] The second comparator 128 converts the divided voltage V DD / α (where α is determined by a pair of voltage-dividing resistors 134) and the reference output voltage V REF，OUT Select the reference output voltage V REF,OUT Make αV REF,OUT is equal to the target output voltage. In this case, the target voltage is 3V. The reference output voltage V REF,OUT Can be programmable to correspond to different target voltages, for example for powering different SoCs.

[0048] The input voltage control section 121 includes an output voltage comparator 130 and a multiplexer 132. The output voltage comparator 130 receives the divided voltage V of the output voltage at its inverting input terminal. DD / α, receiving the output voltage threshold V at its non-inverting input DDMIN The multiplexer 132 includes two inputs, a first reference input voltage V DDLLMINH and a lower second reference input voltage V DDLLMINLThe output of the multiplexer 132 is the reference input voltage provided to the first comparator 126. When the output of the output voltage comparator 130 is high (ie, when the divided voltage V DD / α is higher than the output voltage threshold V DDMIN ), the multiplexer 132 outputs the first reference input voltage V DDLLMINH When the output of the comparator 130 is low (ie, when the divided voltage V DD / α is lower than the output voltage threshold V DDMIN ), the multiplexer 132 outputs the second reference input voltage V DDDDLMINL .

[0049] In use, the boost converter circuit 104 converts the first voltage V from the battery 102 to a voltage V by repeatedly switching the first switch 122 and the second switch 124 on and off. DDL Boost to output voltage V DD Each cycle of boost converter operation involves the following steps:

[0050] 1. The first switch 122 is closed (the second switch 124 is open) and connects the right end of the inductor 116 to ground (0V). The current flowing through the inductor 116 gradually increases over time, as does the magnetic field generated by the inductor 116. The length of time that the first switch 122 is closed (and the resulting current established in the inductor 116) is controlled by the boost control circuit portion 120 according to the output current requirement of the boost converter circuit 104.

[0051] 2. The first switch 122 is opened and the second switch 124 is closed. Now, the right end of the inductor 116 is connected to the output of the boost converter circuit 104. The magnetic field in the inductor 116 will force the current to continue to flow in the same direction as before, toward the output of the boost converter circuit 104. A voltage equal to the input voltage V is set on the inductor 116. DDL voltage (emf) in series to produce a higher output voltage V DD .

[0052] 3. When the current through the inductor 116 becomes zero, the second switch 124 is turned on. Both switches 122, 124 now remain open until the next boost cycle begins. Alternatively, in a different boost mode, switches 122, 124 remain open until the output voltage V DD drops below the reference output voltage V REF，OUT .

[0053] In other words, in boost converter operation, switches 122, 124 are controlled to repeatedly store energy in the magnetic field of inductor 116 and then release that energy to produce a boosted output voltage V DDAs long as sufficient current is provided from the battery 102, this process will increase the output voltage V at the output of the boost converter circuit 104 to DD Maintain at the predetermined target voltage.

[0054] Figure 2 2 shows a timing diagram 200 illustrating the operation of the boost converter circuit 104 with a new and fully charged battery 102. At an initial time t0, the SoC 108 causes no or little load 202. The boost converter circuit 104 provides a regulated output voltage V DD 3.0V, input voltage V DDL is 1.1V. Output voltage V DD Higher than V DDMIN , so the multiplexer 132 provides the first reference input voltage V to the first comparator 126 DDLMINH .

[0055] However, the current required by SoC 108 varies. For example, operations such as programming, transmitting, and receiving may require relatively large currents, while other operations require very small currents. At time t1, SoC 108 begins to see an increased load 202 (e.g., because a transmission cycle begins). First, boost converter circuit 104 simply reacts by using the charge provided by battery decoupling capacitor 114 to provide the necessary increased current to prevent V DD As the charge on the battery decoupling capacitor 114 is depleted, the increased current demand on the battery 102 causes V DDL drop (due to internal resistance R int The voltage drop across the

[0056] At t2, V DDL drops to the first reference input voltage V DDLMINH This causes the first comparator 126 to output a low signal to the control circuit portion 120. In response, the control circuit portion 120 stops the boost converter operation and stops delivering current to the output terminal of the boost converter circuit 104.

[0057] When the boost converter operation stops, the current demand at the output is delivered by the first decoupling capacitor 110 and the second decoupling capacitor 112, and the output voltage V DD It slowly decreases as the decoupling capacitors 110 , 112 discharge.

[0058] After a while, when V DDL Recover to a value slightly higher than the reference input voltage V DDLMINHWhen the voltage of the first comparator 126 reaches 100V (to account for the hysteresis of the first comparator 126), the first comparator 126 outputs a high signal to the control circuit portion 120 and the boost converter operation begins again. This process repeats as the current demand remains high, with the effect of increasing the input voltage V DDL Stable at the reference input voltage V DDLMINH , and limits the current output of the boost converter circuit 104 .

[0059] Select the first reference input voltage V DDLMINH , so that the output current of the boost converter circuit 104 is limited to a level lower than the maximum possible output current. DDL The maximum output current can be delivered when V is equal to half the no-load battery voltage (see equation (5) above), so V DDLMINH to be greater than half the no-load battery voltage. In this example, the no-load battery voltage is 1.1 V, and V DDLMINH 1 V. Allowing the boost converter circuit 104 to draw less than the maximum possible current increases the amount of energy that can be extracted from the battery 102 because less energy is lost to the internal resistance of the battery 102. The size of the capacitors 110, 112 can be selected to ensure that sufficient current is still delivered to the SoC 108 during periods of high load. In other words, the boost converter circuit 104 can act to average the current drawn from the battery 102 to reduce energy losses associated with large current spikes.

[0060] After the current limit is activated at t2, the current required by the SoC 108 is higher than the maximum output current of the boost converter circuit 104. Therefore, as the charge in the decoupling capacitors 110, 112 is depleted, the output voltage V DD This decrease continues until t3, when the load 202 caused by the SoC 108 drops back to its initial low value. However, the decoupling capacitors 110, 112 (and the battery decoupling capacitor 114) still need to be recharged. Therefore, the decoupling capacitors 110, 112 continue to draw a large output current from the boost converter circuit 104 (the boost converter circuit 104 continues to pass the V DDL The boost converter circuit 104 turns the output current on and off to limit the output current) until they are fully charged at time t4. The current required by the boost converter circuit 104 then returns to a low level and the battery decoupling capacitor 114 recharges to 1.1 V. The system 100 is now ready for the next load pulse, such as the next transmission cycle.

[0061] Figure 3 A timing diagram 300 is shown, which shows the operation of the boost converter circuit 104 at a later time, when the battery 102 has been partially discharged. Due to the discharge, the internal resistance R intincreases, that is, the condition of the battery 102 deteriorates.

[0062] At time t5, SoC 108 causes no or little load 202. Despite the fact that the battery condition has deteriorated, load 202 is small and boost converter circuit 104 is still able to deliver a stable 3.0 V output voltage V DD , input voltage V DDL is 1.1 V. The output voltage V DD Higher than V DDMIN , so the multiplexer 132 provides the first reference input voltage V to the first comparator 126 DDLMINH .

[0063] At time t6, the load 202 caused by the SoC 108 increases (e.g., because a transmission cycle begins). As before, the boost converter circuit 104 initially reacts by using the charge provided by the battery decoupling capacitor 114 to provide the necessary increased current to prevent V DD As the charge on the battery decoupling capacitor 114 is depleted, the increased current demand on the battery 102 causes V DDL drop (due to the internal resistance R int The voltage drop across the

[0064] At t7, V DDL drops to the first reference input voltage V DDLMINH This causes the first comparator 126 to output a low signal to the control circuit portion 120. In response, the control circuit portion 120 stops the boost converter operation and stops delivering current to the output of the boost converter circuit 104. As before, the boost converter circuit 104 is switched on and off to limit the output current and to reduce the input voltage V DDL Stable at the first reference input voltage V DDLMINH However, due to the internal resistance R int As the input current provided by battery 102 increases, it is smaller than before, and boost converter circuit 104 must limit the output current to a correspondingly lower level to reduce V DDL Maintain at V DDLMINH This results in an output voltage V DD Therefore, the output voltage V DD Indicates the condition of the battery 102.

[0065] like Figure 3 As shown by the dotted line, if the output voltage V DD Continuing to decrease at this rate, it will reach the minimum operating voltage V of SoC 108 before the load pulse ends. DDRESET, and the SoC 108 will stop working. Therefore, the boost converter circuit 104 uses the output voltage comparator 130 to monitor the output voltage and take appropriate mitigation measures. At time t8, the output voltage V DD Reaching the output voltage threshold V DDMIN This causes the output of the output voltage comparator 130 to go low, and the multiplexer 132 outputs a lower second reference input voltage V DDLMINL When the output voltage V DD The output voltage threshold V of the boost converter circuit 104 is reached DDMIN When the output voltage comparator 132 outputs a low value, it is recognized by the output voltage V DD An alert of a degradation in battery condition indicated by a degradation in battery condition (eg, a “low battery” alert indicating that the battery may need to be replaced or recharged soon) is sent to SoC 108 .

[0066] Also select the second reference input voltage V DDLMINL , so that the output current of the boost converter circuit 104 is limited to a level below the maximum possible output current.

[0067] Because the multiplexer 132 now outputs a lower second reference input voltage V DDLMINL At time t8, the boost converter circuit 104 allows the input voltage V DDL Drop to V DDLMINL . This compensates for R int increases, and allows the boost converter circuit 104 to increase the output voltage V DD Keep at the threshold V DDMIN or slightly above the threshold V DDMIN (See Equation (6)). In other words, by relaxing the input voltage requirement, the boost converter circuit 104 allows additional energy to be extracted from the battery 102. This allows the boost converter circuit 104 to increase the output voltage V to 100 during the entire load pulse. DD Keep at V DDRESET above.

[0068] When the load pulse ends at time t9, the decoupling capacitors 110 and 112 are recharged to 3.0 V, and at time t 10 , the battery decoupling capacitor 114 is recharged to 1.1 V. The output of the voltage comparator 130 goes high, and the multiplexer 132 outputs the first reference input voltage V DDLMINH .

[0069] Figure 4Another circuit portion 400 is shown, which includes a battery 102, a boost converter circuit 404, and a system on a chip (SoC) 108. The battery 102 and the boost converter 404 together power the SoC 108. The battery 102 and the SoC 108 are the same as described above. The boost converter circuit 404 is the same as the boost converter circuit described above, except for the input voltage control portion 421. As described above, the boost converter circuit 404 receives an input voltage V from the battery 102. DDL , and provides a higher output voltage V to SoC 108 DD .

[0070] Normal operation of the boost converter circuit 404 is similar to that described above with reference to Figure 1 and Figure 2 However, in this embodiment, the input voltage control part 421 includes a comparison part 430 and a multiplexer 432, and the multiplexer 432 has multiple input terminals to receive multiple reference input voltages V DDLMIN0 –V DDLMINX The comparison section 430 converts the divided voltage V DD / α with multiple reference output voltages V DDMIN0 –V DDMINX The multiplexer 423 is used to provide a suitable reference input voltage V to the first comparator 126. DDLMIN0 –V DDLMINX .

[0071] Figure 5 A timing diagram 500 illustrating the operation of the boost converter circuit 404 is shown.

[0072] At time t 11 , SoC 108 causes little or no load 202. Boost converter circuit 404 delivers a regulated output voltage V of 3.0 V. DD , input voltage V DDL is 1.1 V. The output voltage V DD Higher than V DDMIN0 , so the multiplexer 432 provides the first reference input voltage V to the first comparator 426 DDLMIN0 .

[0073] At time t 12 , SoC 108 begins to incur an increased load 202 (e.g., because a transmission cycle begins). As before, boost converter circuit 404 initially reacts by using the charge provided by battery decoupling capacitor 114 to provide the necessary increased current to prevent V DD As the charge on the battery decoupling capacitor 114 is depleted, the increased current demand on the battery 102 causes V DDLdrop (due to internal resistance R int The voltage drop across the

[0074] In t 13 , V DDL drops to the first reference input voltage V DDLMIN0 This causes the first comparator 126 to output a low signal to the control circuit portion 120. In response, the control circuit portion 120 stops the boost converter operation and stops delivering current to the output terminal of the boost converter circuit 104.

[0075] As before, the boost converter circuit 404 is switched on and off to limit the output current and to reduce the input voltage V DDL Stable at the first reference input voltage V DDLMIN0 Select the first reference input voltage V DDLMIN0 , so that the output current of the boost converter circuit 404 is limited to a level below the maximum possible output current. This allowed current is lower than the current required by the SoC 108. Therefore, as the charge on the capacitors 110, 112 is depleted, the output voltage V DD Continue to descend.

[0076] At time t 14 , output voltage V DD Reaching the first reference output voltage V DDMIN0 The comparison section 430 detects this and controls the multiplexer 423 to provide the second reference input voltage V to the first comparator 126. DDLMIN1 The comparison section 430 also sends a signal to the SoC 108 identifying the output voltage V DD DOWN indicates an alert that the battery condition is deteriorating.

[0077] Also select the second reference input voltage V DDLMIN1 , so that the output current of the boost converter circuit 104 is limited to a level lower than the maximum possible output current. This current is greater than the first reference input voltage V DDLMIN0 The available current is still insufficient to meet the current demand of SoC 108. The output voltage V DD Continue to descend.

[0078] At time t 15 , output voltage V DD Reaching the second reference output voltage V DDMIN1 The comparison section 430 detects this and controls the multiplexer 423 to provide the third reference input voltage V to the first comparator 126. DDLMIN2 The comparison section 430 also sends a signal to the SoC 108 identifying the output voltage V DD has dropped to the second reference output voltage V DDMIN1The fact that the battery condition is deteriorating is an alarm.

[0079] A third reference input voltage V can also be selected DDLMIN2 , so that the output current of the boost converter circuit 104 is limited to a level lower than the maximum possible output current. This current is greater than the first reference input voltage V DDLMIN0 and the second reference input voltage V DDLMIN1 This is now sufficient to meet the current requirements of the SoC 108. The output voltage V DD Stable at V DDMIN1 However, later in the battery life, the reference input voltage may need to be further reduced to keep the output voltage at V DDRESET The above is to extract the maximum possible energy from the battery 102.

[0080] The load pulse at time t 16 Then, the decoupling capacitors 110 and 112 are recharged to 3.0 V and at time t 17 , the battery decoupling capacitor 114 is recharged to 1.1 V. The comparison section 430 detects this and controls the multiplexer 423 to provide the first reference input voltage V to the first comparator 126 again. DDLMIN02 .

[0081] Although the present invention has been described in detail in conjunction with only a limited number of embodiments, it should be readily understood that the present invention is not limited to these disclosed embodiments. On the contrary, the present invention may be modified to incorporate any number of variants, changes, substitutions, or equivalent arrangements that have not been described heretofore but are commensurate with the scope of the present invention. In addition, although various embodiments of the present invention have been described, it should be understood that various aspects of the present invention may include only some of the described embodiments. Therefore, the present invention should not be considered to be limited by the foregoing description, but only by the scope of the appended claims.

Claims

1. A boost converter circuit, comprising: an input terminal configured to receive an input voltage from a battery; an output terminal configured to generate a higher output voltage to power another circuit portion; as well as a switching device configured to control the generation of said output voltage; Wherein, the boost converter circuit is configured as follows: comparing the input voltage with a first reference input voltage; controlling the switching device to limit an output current of the boost converter circuit based on a comparison of the input voltage with the first reference input voltage; monitoring a parameter indicative of a condition of the battery; determining a second, lower reference input voltage in response to the monitored parameter; comparing the input voltage to the second reference input voltage; and The switching device is controlled to limit the output current of the boost converter circuit based on a comparison of the input voltage with the second reference input voltage.

2. The boost converter circuit according to claim 1, arranged to control the switching device to limit the output current of the boost converter circuit if the input voltage is equal to or less than the first and / or second reference input voltage.

3. A boost converter circuit according to claim 1 or 2, comprising an input comparator arranged to compare the input voltage with the first and / or second reference input voltage.

4. A boost converter circuit according to any preceding claim, arranged to: compare the input voltage with the first reference input voltage when the monitored parameter is above a threshold; and to compare the input voltage with the second reference input voltage when the monitored parameter is below the threshold.

5. A boost converter circuit according to any preceding claim, wherein: The parameter indicative of the battery condition is the output voltage.

6. A boost converter circuit as claimed in any preceding claim, arranged to generate an alarm in response to a monitored parameter.

7. A boost converter circuit according to any preceding claim, wherein: The first and / or second reference input voltage is selected such that the output current of the boost converter circuit is limited to a level below a maximum possible output current of the boost converter circuit.

8. A boost converter circuit according to any preceding claim, wherein: The first and / or second reference input voltage exceeds half of a no-load battery voltage of the battery.

9. A boost converter circuit according to any preceding claim, comprising one or more output capacitors connected in parallel with the output terminal.

10. A boost converter circuit according to any preceding claim, arranged to: determine a third reference input voltage in response to a monitored parameter; compare the input voltage with the third reference input voltage; and control the switching device to limit the output current of the boost converter circuit in response to the comparison of the input voltage with the third reference input voltage.

11. A circuit system comprising: a battery configured to generate an input voltage; as well as A boost converter circuit as claimed in any preceding claim, wherein the input terminal is connected to the input voltage generated by the battery.

12. The circuit system according to claim 11, wherein: The nominal capacity of the battery is less than 2000 mWh.

13. A circuit system as claimed in claim 10 or 11, comprising a further circuit part connected to the output terminal.

14. The circuit system according to claim 13, wherein: The other circuit portion has a minimum operating voltage, and the second reference input voltage is determined in response to the monitored parameter to maintain the output voltage above the minimum operating voltage.

Images