Automatically reconfigurable charging pump system

Abstract

The invention relates to a charge pump system (100) comprising: - a charge pump (1) comprising n pump stages (Si), each pump stage (Si) being configured to be activated or deactivated according to an activation signal transmitted to said pump stage (Si), the number of activated pump stages (Si) being between 0 and n, - a voltage regulator (LDO) connected to the charge pump (1) configured to generate a regulator output voltage (Vldo), - a prediction circuit (2) configured to generate a prediction voltage (Vcp+1) at the output of the prediction circuit (2) and to compare the prediction voltage (Vcp+1) to the regulator output voltage (Vldo). The invention further relates to a method for automatically configuring the number of activated pump stages. Figure 1

Description

Title of the invention: Automatically reconfigurable charge pump system. Technical field

[0001] The invention relates to energy conversion in integrated electronic circuits. In particular, the invention relates to a charge pump system comprising, among other things, a charge pump, a voltage regulator, and a prediction circuit. Prior art

[0002] A linear voltage regulator, or "Low Dropout Regulator" in Anglo-Saxon terminology, is an electronic device that maintains a constant output voltage despite variations in the input voltage. Unlike switching regulators, linear voltage regulators are valued for their simple design, low electrical noise, and rapid response to load changes, making them suitable for sensitive applications.

[0003] A charge pump is an electronic circuit that converts an input voltage to a higher or lower output voltage using switches and capacitors. The charge pump is often used to efficiently generate the required voltage in a system without the need for transformers or inductors.

[0004] A charge pump can be used to power a voltage regulator. The charge pump thus provides a supply voltage adjusted to the voltage regulator. The charge pump can increase or decrease the input voltage to bring it closer to the output voltage desired by the voltage regulator. This allows the voltage regulator to operate more efficiently, as the difference between the input and output voltages is reduced, thereby minimizing power losses and improving the overall efficiency of the system.

[0005] A linear voltage regulator receives an input voltage and regulates this input voltage to provide a stable output voltage. An internal or external reference to the linear voltage regulator, called the control voltage, determines the value of the output voltage. The linear voltage regulator compares the control voltage to the output voltage via a feedback network and adjusts the output voltage to minimize the error between the control voltage and the feedback voltage.

[0006] The operating mode of the linear voltage regulator, whether in regulation or linear mode, depends on the relationship between the supply voltage and the output voltage. When the supply voltage is sufficiently higher than the voltage At the output, the linear voltage regulator operates efficiently in regulation mode. If the supply voltage drops below a given threshold and approaches the output voltage, the linear voltage regulator may enter linear mode, where voltage regulation and noise rejection are degraded, more heat is generated, and the system efficiency decreases.

[0007] The control voltage of the linear regulator is essential for this dynamic. If the control voltage changes, for example, by decreasing due to a change in temperature in the surrounding environment, the linear voltage regulator must adjust the output voltage accordingly. If the linear voltage regulator fails to maintain the necessary difference between the supply voltage and the output voltage, the linear voltage regulator may operate in linear mode, thus degrading the system's performance.

[0008] It is known in the prior art to maintain the linear voltage regulator within its operating range by selecting a static input voltage that is satisfactory for the highest value of the output voltage to be addressed. However, in this case, the overall efficiency for low output voltages is suboptimal. Furthermore, this solution is not suitable when the input voltage itself varies over time.

[0009] The object of the present invention is to overcome the drawback described above and to allow the linear voltage regulator to operate in regulated mode without being influenced by variations in the control voltage or the input voltage. Summary of the invention

[0010] The present invention relates to a charging pump system comprising: - a charge pump connected between an input terminal and a reference terminal to an external input power supply to the charge pump system to receive an input supply voltage and to generate, depending on the input supply voltage, at the output of the charge pump between an output terminal and the reference terminal, a pump output voltage, the charge pump comprising a number Nmax of pump stages, and each pump stage being configured to be activated or deactivated, the number N of activated pump stages being between 0 and Nmax,

[0011] - a voltage regulator connected to the charging pump between the output terminal and the reference terminal, and configured to receive the pump output voltage at the input of said voltage regulator and to generate, based on the pump output voltage, a regulator output voltage, - a prediction circuit configured for: - generate a prediction voltage at the output of the prediction circuit that represents a change in the number of activated pump stages, - an activation device configured for: - compare the predicted voltage to the regulator output voltage to obtain a predicted result,

[0012] - modify or not the number of pump stages N activated depending on the result of prediction obtained, so as to modify or not the pump output voltage so that the difference between the pump output voltage and the regulator output voltage is within an operating voltage range.

[0013] Advantageously, supplying the voltage regulator with a step-down charge pump improves the efficiency of the charge pump system compared to supplying the voltage regulator directly from the power source that provides the input supply voltage.

[0014] Thanks to the arrangements according to the invention, an automatic reconfiguration circuit for the charge pump based on predictions is obtained. The charge pump system makes it possible to take into account variations in the input voltage or the reference voltage.

[0015] According to one embodiment, the operating voltage range or predetermined voltage range is between a low threshold and a high threshold.

[0016] According to one embodiment, each pump stage is configured to receive an intermediate input voltage and to generate, at the output of said pump stage, based on the intermediate input voltage, an intermediate output voltage. The prediction circuit is configured to take a plurality of intermediate input or output voltages, and the prediction circuit comprises: - a multiplexer configured to select an intermediate input voltage from among the sampled intermediate input voltages, - at least one modification stage configured to generate a prediction voltage based on the selected intermediate voltage.

[0017] Advantageously, the prediction circuit comprising a multiplexer allows a plurality of intermediate output voltages to be taken from different nodes of the charge pump, thus allowing the input voltage of the prediction circuit to be varied.

[0018] According to one possibility, the intermediate input voltage of a pump stage of rank i+1 corresponds to the intermediate output voltage of a pump stage of rank i, rank i being between 1 and Nmax.

[0019] According to one embodiment, the selection made by the multiplexer is controlled by the activation device and corresponds to the number of activated stages N.

[0020] According to one embodiment, at least one modification stage is configured to have a structure similar to a pump stage of the charging pump

[0021] Thus, the modification stage simulates the behavior of a pump stage because it has a similar or identical structure comprising the same components.

[0022] According to one embodiment, the modification stage receives the same activation commands as a pump stage of the charging pump that it simulates.

[0023] According to one embodiment, in which each pump stage is configured to receive an intermediate input voltage and to generate an intermediate output voltage from said pump stage based on the intermediate input voltage, the prediction circuit comprising: - a resistive voltage divider bridge connected between a first terminal chosen between the output terminal and the input terminal and a second terminal corresponding to the reference terminal, the resistive voltage divider bridge comprising a plurality of resistive components, each resistive component being configured such that the voltage across each resistive component corresponds to the intermediate input voltage or the intermediate output voltage of the corresponding pump stage, - a multiplexer connected to the terminals of at least one resistive component of the plurality of resistive components and configured to select a voltage from among the voltages across the resistive components, the selected voltage corresponding to the prediction voltage.

[0024] Advantageously, the charge pump system including the resistive voltage divider bridge reduces the footprint by 20% compared to the charge pump system with capacitive division.

[0025] According to one embodiment, the selection made by the multiplexer is controlled by the activation device and corresponds to the number of activated stages N.

[0026] According to one embodiment, each resistive component has between the terminals of said resistive component a resistance value defined according to the number of pump stage(s) activated.

[0027] Advantageously, it is possible to act on the number of pump stages activated to modify the value of the resistance of the resistive component.

[0028] According to one embodiment, each pump stage of rank i comprises a capacitive component including a first electrode connected on one side to an input of the pump stage, and on the other side connected by a first switch to the input of the pump stage of rank i+1 or the output voltage; and a second electrode connected on one side by a second switch to the output terminal and on the other side by a third switch to the reference terminal.

[0029] Advantageously, the use of switches allows the configuration of the charging pump to be changed in a simple and programmed manner in order to modify the pump output voltage.

[0030] According to one embodiment, the charging pump is a Dickson charging pump.

[0031] Advantageously, the use of a Dickson charge pump allows the pump output voltage to be modified relative to the input supply voltage of the charge pump system using a reduced number of active components, thereby improving the efficiency and compactness of the charge pump system.

[0032] According to one embodiment, the system further comprises a microelectromechanical system connected at the output of the voltage regulator between the reference terminal and an output terminal of the regulator.

[0033] Advantageously, the charge pump system allows the microelectromechanical system to be supplied with a stable voltage, enabling the microelectromechanical system to operate reliably while reducing the risks of malfunctions or failures of the microelectromechanical system due to voltage fluctuations.

[0034] According to one embodiment, the number n of pump stages is between 3 and 10, for example four pump stages.

[0035] Advantageously, the number of pump stages can be chosen according to the desired pump output voltage value.

[0036] The present invention also relates to a method for configuring a number of activated pump stages for a previously defined charging pump system, comprising the following steps: - measurement of the voltage difference between the pump output voltage and the regulator output voltage, - if said difference is less than a low threshold, modify the number of activated pump stages by reducing said number of activated pump stages N, - if said difference is greater than the upper threshold, generate a prediction voltage, and compare the prediction voltage to the regulator output voltage to obtain a prediction result, and, if the prediction result is greater than the lower threshold, modify the number of activated pump stages by increasing said number of activated pump stages, - if said difference is between the lower threshold and the upper threshold, maintain unchanged the number of activated pump stages N. Brief description of the figures

[0037] The invention will be described with reference to the following figures, which are given for illustrative purposes only and are not reproduced to scale. In these figures, the same reference numerals designate the same elements.

[0038] [Fig-1] [Fig.1] presents a block diagram of a charging pump system according to the invention.

[0039] [Fig.2] [Fig.2] presents an example of a charging pump in a first phase of operation.

[0040] [Fig. 3] [Fig. 3] presents an example of a charging pump in a second phase of operation.

[0041] [Fig.4] [Fig.4] presents a first embodiment of a prediction circuit for a charging pump system according to the invention.

[0042] [Fig. 5] [Fig. 5] presents a second embodiment of a prediction circuit for a charging pump system according to the invention.

[0043] [Fig.6] [Fig.6] is a flowchart that presents the steps of a process of configuration of the number of pump stages activated for a charging pump system.

[0044] [Fig.7] Fig.7 represents the evolution of the LDO control voltage in temperature function

[0045] [Fig.8] Fig.8 represents the reference voltage Vref on the abscissa and the efficiency as a percentage on the ordinate for an embodiment of a charge pump system according to the invention and a charge pump performing a division by 2.

[0046] [Fig.9] Figure [Fig.9] represents the evolution of the output voltage Vout and the voltage reference Vref as a function of time for a charging pump system.

[0047] Other advantages and technical characteristics may emerge from the following description, which is made with reference to the figures shown above. Detailed description Charging pump system

[0048] Fig. 1 presents a block diagram of the charging pump system 100.

[0049] Figure 1 shows in particular the main elements of the pump system charge 100: a charge pump 1, a prediction circuit 2, and an activation device 4. A linear voltage regulator LDO is arranged at the output of the charge pump.

[0050] The charge pump 1 provides an output voltage Vcp which is the input voltage of the linear voltage regulator LDO.

[0051] If the difference between the input voltage Vcp of the linear voltage regulator LDO and its output voltage Vldo is within an operating voltage range between a high voltage threshold Th and a low voltage threshold Tl, the The LDO linear voltage regulator can operate within a regulated operating range; in other words, the LDO linear voltage regulator can perform as desired. The high and low voltage thresholds can be defined based on the intrinsic characteristics of the LDO linear voltage regulator. For example, the low threshold could be 150mV and the high threshold 200mV.

[0052] The charge pump system 1 allows the output voltage Vcp to be adapted to remain within the desired operating range of the LDO, or of another load at the output of the charge pump.

[0053] The charge pump 1 is a multi-stage reconfigurable or programmable-rank charge pump, meaning that the charge pump 1 can have different operating configurations in which the number of activated pump stages N can vary. It can be seen from [Fig. 1] that the charge pump 1 takes the supply voltage Vin and reduces the supply voltage Vin through the different pump stages to produce the pump output voltage Vcp, the value of which corresponds to the voltage across a capacitor Ctank connected between the output of the charge pump 1 and a reference terminal GND.

[0054] The pump output voltage Vcp depends on the number of activated stages N.

[0055] Thus, the activation device 4 is configured to adjust the switching sequences of the charging pump 1 switches and modify the configuration of the charging pump 1, in particular the number of pump stages activated to maintain the desired pump output voltage Vcp.

[0056] In particular, the activation device 4 is configured to modify or not, according to a prediction result, the number N of pump stages Si activated so as to modify or not the pump output voltage Vcp so that the difference between the pump output voltage Vcp and the regulator output voltage Vldo is within the predetermined operating voltage range.

[0057] The activation device can use comparisons between the pump output voltage Vcp, a prediction voltage Vcp+1, the voltage Vldo, and the high and low reference thresholds Th and Tl.

[0058] The prediction circuit 2 aims to generate the prediction voltage Vcp+1 to anticipate the effect of a change in the number of activated stages.

[0059] The process implemented by the activation device 4 and embodiments of the prediction circuit are detailed later.

[0060] The linear voltage regulator (LDO) uses the voltage Vcp to produce the regulator output voltage Vldo. The linear voltage regulator (LDO) ensures that the regulator output voltage Vldo remains stable despite variations in the supply voltage Vin.

[0061] One objective of the linear voltage regulator (LDO) is to provide a stable output voltage Vldo from a pump output voltage Vcp (which is also the input voltage of the LDO). It is desirable that the difference between the two voltages Vcp and Vldo be as small as possible while keeping the LDO within its optimal operating range.

[0062] As can be seen in [Fig. 1], the linear voltage regulator LDO includes an Mpass transistor, controlled by an operational amplifier A4. The linear voltage regulator LDO can adjust the regulator output voltage Vldo by modulating a gate voltage Vg of the Mpass transistor to maintain the regulator output voltage Vldo at the desired value.

[0063] Operational amplifier A4 can compare a reference voltage Vref with a fraction of the regulator output voltage Vldo obtained by the resistive bridge Ra, Rb. The reference voltage Vref can be generated by a voltage source external to the charge pump system 100, and can vary, in particular due to temperature variations.

[0064] Operational amplifier A4 can then adjust the gate voltage Vg to stabilize the regulator output voltage Vldo. If the regulator output voltage Vldo decreases, operational amplifier A4 increases the gate voltage Vg to allow more current to flow through transistor Mpass, thus increasing the regulator output voltage Vldo. If the regulator output voltage Vldo increases, operational amplifier A4 decreases the gate voltage Vg to reduce the current, lowering the regulator output voltage Vldo. The feedback circuit, comprising the resistive bridge Ra, Rb, and operational amplifier A4, is designed to maintain a constant regulator output voltage Vldo despite variations in the pump output voltage Vcp.

[0065] In [Fig.1], the regulator output voltage Vldo is supplied to a microelectromechanical system Rmems included in the charge pump system 100 and connected to the output of the voltage regulator LDO between the reference terminal GND and an output terminal of the regulator X.

[0066] The Rmems electromechanical microsystem can be replaced by any type of electrical load, and in particular a resistive load.

[0067] Advantageously, for a variation of the reference voltage Vref from 100mV to 500mV, the use of a prediction circuit 2 for the charge pump system 100 can allow the operation of the linear voltage regulator LDO in the regulation area, and can increase the power efficiency of the charge pump system 100 by about 9%.

[0068] The charge pump system 100 can be fully implemented in CMOS technology.

[0069] Activation device and method for configuring the number of charging pump stages

[0070] The method for controlling the configuration of a number N of pump stages implemented by the activation device 4 is now described with reference to Figures 1 and 2.

[0071] The device includes a 4-1 state machine that stores in memory a number N of activated stages and is configured to modify this number, as well as a set of comparators A1, A2, A3. The state machine is implemented, for example, by a dedicated digital circuit. In particular, the digital circuit can be implemented with logic gates integrated alongside the charge pump on the same integrated circuit.

[0072] The method for configuring the number of activated pump stages includes the following steps.

[0073] A measurement step E1 of a voltage difference between the pump output voltage Vcp and the regulator output voltage Vldo is performed. If said difference is less than the lower threshold Tl, for example 150mV, the number of activated pump stages N is modified in a step E2 by reducing said number of activated pump stages, for example by one activated pump stage, i.e. N=N-1.

[0074] The comparison of the difference between Vcp and Vldo with the lower threshold can be performed by a first comparator A1 which receives Vcp, Vldo, and the lower threshold Tl as inputs. For example, a differential difference amplifier (DDA) can be used as a comparator. In this case, the equation giving the output voltage VCMP1, if the four inputs are respectively at voltages Vcp, 2T1, Vldo, and Tl, is as follows:

[0075] VCMP1=Al[(Vcp-2*Tl)-(Vldo-Tl)]

[0076] We deduce from this:

[0077] VCMPl=Al[(Vcp-Vldo-Tl)]

[0078] Consider a measurement of Vcp-Vldo with respect to Tl, with Al the comparator gain.

[0079] If said difference between Vcp and Vldo is greater than the upper threshold Th, for example at 200mV, in a step E3 we compare the prediction voltage Vcp+1 to the regulator output voltage Vldo so as to obtain a prediction result which corresponds to a difference between the prediction voltage Vcp+1 and the voltage Vldo.

[0080] If the difference between Vcp+1 and Vldo is greater than the lower threshold Tl, for example 150mV, the activation device 4 modifies in a step E4 the number of activated pump stages N by increasing said number of activated pump stages, for example by one activated pump stage, i.e. N=N+1.

[0081] The comparison of the difference between Vcp and Vldo with the upper threshold Th can be performed by a second comparator A2 which receives as input Vcp, Vldo as well as The upper threshold Th. As an example, a differential difference amplifier (DDA) can be used as a comparator. In this case, the equation giving the output voltage VCMP2, if the four inputs are respectively at voltages Vcp, 2Th, Vldo, and Th:

[0082] VCMP2=A2[(Vcp-2*Th)-(Vldo-Th)]

[0083] We deduce from this:

[0084] VCMP2=A2[(Vcp-Vldo-Th)]

[0085] Consider a measurement of Vcp-Vldo with respect to Th, with A2 being the comparator gain.

[0086] The comparison of the difference between Vcp+1 and Vldo with the lower threshold Tl can be This is achieved by a third comparator A3, which receives Vcp+1, Vldo, and the low threshold Tl as inputs. As an example, a differential difference amplifier (DDA) can be used as a comparator. In this case, the equation giving the output voltage VCMP3, if the four inputs are respectively at voltages Vcp+1, 2T1, Vldo, and Tl:

[0087] VCMP3= A3[(Vcp+1 - 2*Tl)-(Vldo-Tl)]

[0088] We deduce from this:

[0089] VCMP3=A3 [(Vcp+1 - Vldo-Tl)]

[0090] Consider a measurement of Vcp+1-Vldo with respect to Tl, with A3 the comparator gain.

[0091] In the case where said difference between Vcp and Vldo is between the lower threshold Tl and the upper threshold Th, the number of activated pump stages N remains unchanged. In this case, the charging pump 1 retains its current pump configuration.

[0092] The output voltages of comparators VCMP1, VCMP2, VCMP3 can be considered as a binary signal, respectively CMP1, CMP2, CMP3, taking a value of 1 if the voltage value is positive, 0 if the value is negative, which allows the process described above to be implemented in a simple way.

[0093] Thus, if the comparison signals CMP1, CMP2, and CMP3 all have the value 1, then the number of activated pump stages is increased by one. If the comparison signals CMP1, CMP2, and CMP3 all have the value 0, then the number of activated pump stages is decreased by one. In all other cases, the number N of activated pump stages remains unchanged. Charging pump

[0094] An example of a charge pump 1 will now be described with reference to Figures 3 and 4. The charge pump 1 is connected between an input terminal IN and a reference terminal GND to an external input power supply to the charge pump system 100 to receive an input supply voltage Vin. The supply voltage Vin can vary over time periodically or non-periodically. By way of example, such a variation can be a function of parameters not predictable by a component providing the input voltage, such as an ASIC, or coming from battery operation.

[0095] The charge pump 1 can generate, depending on the input supply voltage Vin, at the output of the charge pump 1 between an output terminal OUT and the reference terminal GND, a pump output voltage Vcp.

[0096] The charging pump 1 can be step-down, that is to say that the pump output voltage Vcp is less than the input supply voltage Vin, which is the configuration shown in Figures 5 there.

[0097] The charging pump 1 may include an input switch Int-in and an assembly comprising n pump stages Si. In the example of Figures 2 and 3, the number n of stages is four, and the supply voltage Vin can be divided by a factor of up to five. In other words, the pump output voltage Vcp can be up to five times lower than the supply voltage Vin.

[0098] Each pump stage has a rank i, the rank i evolving in an increasing manner from the supply source at the input of the charging pump 1 and going towards the pump outlet.

[0099] The pump stages SI, S2, S3, S4 are shown in figures 2 and 3.

[0100] Each pump stage Si includes a transfer capacitor Cfly. A first electrode, which is the high electrode in Figures 1 and 2, of the capacitor Cfly is connected on one side to the input of the stage Si, and on the other side by a first switch Intl-i to the input of the next stage Si+1 (or the output voltage for the last stage).

[0101] A second electrode, which is the lower electrode in Figures 2 and 3, is connected on the one hand by a second switch Int2-i to the output voltage VOUT and on the other hand by a third switch Int3-i to a reference terminal GND.

[0102] The switches and transfer capacitors can be implemented using CMOS technology. Each switch can switch between an ON state (in which the switch is closed) and an OFF state (in which the switch is open). If the intl-i switch of the pump stage Si is in an ON state, the corresponding pump stage Si is activated. If the intl-i switch of the pump stage Si is in an OFF state, the corresponding pump stage Si is deactivated.

[0103] The charging pump 1 is reconfigurable or programmable rank, meaning that said charging pump 1 can have different operating configurations in which the number of activated pump stages N can vary. In the example of [Fig. 3], the charging pump 1 has four pump stages S1, S2, S3, S4, and the number of activated pump stages N can vary between 0 and four depending on the priming and blocking of intl-i switches. For example, among the pump stages SI to S4 only the pump stages SI and S2 can be activated.

[0104] Each pump stage Si is configured to be activated or deactivated according to an activation signal transmitted to said pump stage Si by the activation device which determines the number of activated stages N. The number of activated pump stages N of Si is between 0 and Nmax, the number Nmax of pump stages can be between 3 and 10, for example four pump stages Si.

[0105] Each pump stage Si is configured to receive as input an intermediate input voltage Vfi and to generate at output of said pump stage, on the basis of the intermediate input voltage Vfi, an intermediate output voltage Vsi, the intermediate input voltage Vfi+1 of a pump stage of rank i+1 corresponding to the intermediate output voltage Vsi of a pump stage of rank i, rank i being between 1 and Nmax.

[0106] The charging pump has two operating phases which alternate periodically, these two phases being shown respectively in figures 2 and 3.

[0107] We present these two configuration phases initially assuming that all pump stages Si are activated

[0108] In a first phase represented in [Fig.2], the input switch Intin is closed.

[0109] The first stage SI has the first switch Intl-1 open, the second switch Int2-1 closed and the third switch Int3-1 open.

[0110] The second stage S2 has the first switch Int 1-2 closed, the second switch Int2-2 open and the third switch Int3-2 closed.

[0111] The other odd-ranking floors (on [Fig.2], S3) have the same configuration switches that SI, the other even rank stages (on [Fig.3], S4) have the same switch configuration as S2.

[0112] In a second phase represented in [Fig.3], the input switch Intin is open.

[0113] The first stage SI has the first switch Intl-1 closed, the second switch Int2-1 open and the third switch Int3-1 closed.

[0114] The second stage S2 has the first switch Int 1-2 open, the second switch Int2-2 closed and the third switch Int3-2 open.

[0115] The other odd-rank stages (on [Fig.3], S3) have the same switch configuration as SI, the other even-rank stages (on [Fig.3], S4) have the same switch configuration as S2.

[0116] By alternating the first and second phases, the charging and discharging of the capacitors, it is possible to obtain a voltage division effect.

[0117] Assuming that the switching between the two phases is sufficiently rapid and that the voltages in the various capacitors only change marginally,

[0118] We obtain approximately:

[0119] In the first phase: 1. Vcp = Vin - VCflyl 2. Vcp=VCfly4

[0120] In the second phase: 1. Vcp=-VCfly4+VCfly3 2. Vcp = -VCly3 + VCfly2 3. Vcp = -VCfly2 + VCflyl

[0121] By adding (1) to (5), we deduce that Vcp=Vin / 5

[0122] If one of the first switches of a pump stage Si remains closed according to the activation signal provided by the activation device during the two phases of operation, the corresponding stage is deactivated and the division is modified.

[0123] Thus: - if the Intl-4 switch remains closed during both operating phases, a division by 4 is performed. - if the Intl-4 and Intl-3 switches remain closed during both operating phases, a division by 3 is performed. - if the Intl-4, Intl-3 and Intl-2 switches remain closed during the two operating phases, a division by 2 is performed. - if the Intl-4, Intl-3, Intl-2 and Int-1 switches remain closed during both phases of operation, no division is performed.

[0124] The charge pump 1 described is intended to be used in a charge pump system 100 in combination with a prediction circuit 2, two embodiments of which are shown in Figures 4 and 5. Prediction circuit First method of implementation

[0125] Fig. 4 presents a first embodiment of a prediction circuit.

[0126] Figure 4 shows part of the charge pump system 100 comprising the charge pump 1 as described above and a prediction circuit 2 connected to the charge pump 1. The operation of the charge pump 1 in Figure 5 is identical to that in Figures 3 and 4. A linear voltage regulator, or LDO voltage regulator, is also connected to the output of the charge pump 1. The LDO voltage regulator is connected to the charge pump 1 between the output terminal OUT and the reference terminal GND, and configured to receive the voltage of pump output Vcp into the input of said LDO voltage regulator and to generate, based on the pump output voltage Vcp, a regulator output voltage Vldo.

[0127] The prediction circuit 2 is configured to generate a prediction voltage Vcp + 1 at the output of the prediction circuit 2 representative of a change in the number of pump stages Si activated.

[0128] The prediction circuit 2 can take a plurality of intermediate input voltages Vfi, notably from different nodes of the charge pump 1, and is configured to generate a prediction voltage Vcp+1 based on the selected intermediate voltage Vfi

[0129] The prediction circuit 2 of [Fig. 4] includes a multiplexer MUX configured to select an intermediate input voltage Vfi from among the sampled intermediate input voltages Vfi. The multiplexer is thus connected to the inputs of each of the pump stages. The selection made by the multiplexer is controlled by the activation device 4 and corresponds to the number of activated stages N.

[0130] The prediction circuit 2 is configured to operate by capacitive division and includes at the output of the multiplexer at least one modification stage Mi of a structure similar to a pump stage Si of the charge pump 1. In the case of [Fig.4], the prediction circuit 2 includes two modification stages M1, M2.

[0131] Thus, assuming that N stages are activated, the prediction circuit is configured to take a voltage VfN from the input of stage N, the multiplexer being configured to select this voltage from among its different inputs, and to apply it to the input of the first modification stage which simulates stage N, the first modification stage is connected to the second modification stage which simulates stage N+1, the output of this stage corresponding to the voltage Vcp+1 which is established across a capacitance Ctank2, connected by an electrode to a reference terminal GND.

[0132] The voltage Vcp+1 allows us to predict the voltage that would be applied if an additional stage were activated.

[0133] In [Fig. 4], the charge pump 1 is in an operating phase corresponding to [Fig. 2], with stages 1 and 2 activated. Thus, the modification stages M1 and M2 simulate stages S2 and S3 to produce a prediction voltage Vcp+1 that would correspond to the activation of stage 3. The multiplexer is configured to take the voltage Vf2 from the input of stage S2.

[0134] The activation commands of the modification stage(s) received from the activation device are the same as those of the charging pump stage(s) they simulate.

[0135] Advantageously, the first embodiment of the charge pump system 100 allows an intermediate voltage Vfi to be taken at any pump stage Si.

[0136] Thus, the prediction circuit 2 makes it possible to generate a prediction voltage Vcp + 1 which makes it possible to determine precisely the number of pump stages Si which must be activated in order to keep the linear voltage regulator LDO in the regulated operating area. Second embodiment

[0137] Fig. 5 presents a second embodiment of the prediction circuit 2.

[0138] The operation of the charge pump 1 shown in [Fig.5] is identical to that of Figures 2 and 3. The pump output voltage Vcp is injected into the input of the linear voltage regulator LDO which generates a regulator output voltage Vldo.

[0139] The prediction circuit 2 shown in [Fig.5] is different from the prediction circuit 2 in Figure 4.

[0140] The prediction circuit 2 of [Fig.5] is configured to operate by resistive interpolation, i.e. the prediction circuit 2 comprises a resistive voltage divider bridge RI, R2, R3, R4, R5 connected between a first terminal chosen between the output terminal OUT and the input terminal IN and a second terminal corresponding to the reference terminal GND.

[0141] The resistive voltage divider bridge RI, R2, R3, R4, R5 comprises a plurality of resistive components Ri, each resistive component Ri being configured such that the voltage across each resistive component Ri corresponds to the intermediate input voltage Vfi of the corresponding pump stage Si. For example, the voltage across resistor RI may correspond to the intermediate input voltage of the fourth pump stage SL

[0142] An example for calculating the value of one of the resistances (RI) of the resistive voltage divider bridge is given below.

[0143] The equation for the pump output voltage Vcp is as follows:

[0144] [Math.l] V — ^22. T *_____1_____ vcp— n 1 load 2*N*Cf*fCP

[0145] Vin is the input supply voltage, N the number of pump stages activated, Iload the charging current, Cf the capacitance of each transfer capacitor Cfly and fcp the switching frequency of the charge pump 1.

[0146] The equation expresses the pump output voltage Vcp taking into account the voltage drop due to the charging current and the characteristics of the charging pump 1.

[0147] The impedance of the charging pump ZOcp can be calculated according to the following equation:

[0148] [Math.2] 7 _____1____ ^Ocp— 2*N*CP*fPP

[0149] The impedance ZOcp is determined by the characteristics of the charge pump 1, in particular the number N of pump stages, the capacitance of the transfer capacitors Cfly, and the switching frequency fcp.

[0150] The prediction voltage Vcp+1 can be calculated according to the following equation:

[0151] [Math.3] t T __ Wine t ________1________ v cp+1 — 7V+1 ' hoad 2*N+l*Cf*fcp

[0152] The prediction voltage Vcp+1 corresponds to a division of the voltage Vcp by the resistive divider bridge RI, R', with R' corresponding to the sum of the resistances at the bottom of the divider bridge (R'=R2+R3+R4+R5) and is therefore calculated according to the following equation:

[0153] [Math.4] v — v * R' vcp+-l_ VCP Rl+R'

[0154] By substituting the previous equations to find RI as a function of R', the following equation can be obtained:

[0155] [Math.5] Wine r 1 __(Wine r 1 Yfr R' N+lUoad 2*CV+l)*Cf*fCP — [ N ~1load 2*N*Cf*fCP) Rl+R'

[0156] By expanding and simplifying, the following equation can be obtained:

[0157] [Math.6] t V i \ i A IV- 1 i IT *________±_______ | DI | DI — I «i T *______±______ km । [ N+l ~1load 2*(N+l)*Cf*fCP} N ~ 1load 2*N*Ct*fCP}

[0158] By isolating the resistance RI, we obtain:

[0159] [Math.7] Ti j Vin _____lload'Kl_____ __ ti il ​​Vjn _____Ijoad_____ Vjn ।__Iload_______i ' 2*(N+l)*Cf*fCP ~ ~ 2*N*C{*fCP ■ jV+1 2*(N+l)*C{*fCP]

[0160] Simplifying the previous equation, we obtain:

[0161] [Math. 8] DI _ hoad Va ■__hcad_____Vin t #_______1_______] -0-1 — [ jy - 2*N*Cc*fcp ' N+l 2*(N+l)*Cr*fcp / l\N+l '^ioad 2*(N+l)*Cr*fcp)

[0162] Neglecting ohmic losses, we obtain:

[0163] [Math.9] Rl = R' / N

[0164] The prediction circuit 2 also includes a multiplexer MUX connected to the terminals of at least one resistive component from the plurality of resistive components Ri and configured to select a voltage from among the voltages across the resistive components. The selected voltage corresponds to the prediction voltage Vcp+1. The selection made by the multiplexer is controlled by the activation device 4 and corresponds to the number of activated stages N.

[0165] At the pump output, the voltage divider bridge, which forms a resistive ladder, is connected to divide the pump output voltage Vcp into several voltage levels lower than the pump output voltage Vcp. The multiplexer MUX is then used to select the voltage closest to each division level on this resistive ladder. This allows different, precise output voltages to be provided by the prediction circuit 2, depending on the selected voltage.

[0166] Advantageously, the resistive interpolation charge pump system 100 reduces the footprint compared to the capacitive division charge pump system 100. For example, for a pump with 4 stages, i.e., a division ratio of 5, the footprint is reduced by 20%.

[0167] In Figures 1 to 4, charge pump 1 is a Dickson charge pump. However, charge pump 1 may be of another type, for example a diode charge pump or a capacitor-switching charge pump.

[0168] Fig. 7 represents the evolution of the LDO control voltage Vref as a function of temperature.

[0169] Fig. 8 represents the efficiency of the solution compared to a charge pump with a division by 2, with the reference voltage Vref on the abscissa and the efficiency as a percentage on the ordinate.

[0170] Figure 9 shows the evolution of the output voltage Vout of a charge pump system and the reference voltage Vref as a function of time. The figure shows that Vout is always at least 150 mV above Vref. The notches correspond to a change in the division rank, i.e., a change in the number of activated stages.

[0171] Alternatively, according to an embodiment not shown, the charging pump 1 can be a multiplier, that is to say, the pump output voltage Vcp is greater than the input supply voltage Vin.

Claims

Demands

1. Charge pump system (100) comprising: - a charge pump (1) connected between an input terminal (IN) and a reference terminal (GND) to an external input power supply to the charge pump system (100) to receive an input supply voltage (Vin) and to generate, depending on the input supply voltage (Vin), at the output of the charge pump (1) between an output terminal (OUT) and the reference terminal (GND), a pump output voltage (Vcp), the charge pump (1) comprising a number Nmax of pump stages (Si), and each pump stage (Si) being configured to be activated or deactivated, the number N of activated pump stages (Si) being between 0 and Nmax, - a voltage regulator (LDO) connected to the charge pump (1) between the output terminal (OUT) and the reference terminal (GND), and configured to receive the pump output voltage (Vcp) at the input of said voltage regulator (LDO) and to generate, based on the pump output voltage (Vcp), a regulator output voltage (Vldo), - a prediction circuit (2) configured for: - generate a prediction voltage (Vcp+1) at the output of the prediction circuit (2) representative of a change in the number of pump stages (Si) activated, - an activation device configured for: - compare the prediction voltage (Vcp+1) to the regulator output voltage (Vldo) to obtain a prediction result, - modify or not the number of pump stages N (Si) activated according to the prediction result obtained, so as to modify or not the pump output voltage (Vcp) so that the difference between the pump output voltage (Vcp) and the regulator output voltage (Vldo) is within an operating voltage range.

2. Charge pump system (100) according to claim 1 wherein each pump stage (Si) is configured to receive an intermediate input voltage (Vfi) at its input and to generate an intermediate output voltage (Vsi) at the output of said pump stage, based on the intermediate input voltage (Vfi), the prediction circuit (2) is configured to take a plurality of intermediate input (Vfi) or output (Vsi) voltages, and the prediction circuit (2) includes: - a multiplexer (MUX) configured to select an intermediate input voltage (Vfi) from among the intermediate input voltages (Vfi) taken, - at least one modification stage (Mi) configured to generate a prediction voltage (Vcp+1) on the basis of the selected intermediate voltage (Vfi).

3. Charge pump system (100) according to claim 2, wherein at least one modification stage (Mi) is configured to have a structure similar to a pump stage (Si) of the charge pump (1)

4. A charge pump system (100) according to claim 1, wherein each pump stage (Si) is configured to receive an intermediate input voltage (Vfi) and to generate an intermediate output voltage (Vsi) from said pump stage, based on the intermediate input voltage (Vfi), the prediction circuit (2) comprising: - a resistive voltage divider bridge connected between a first terminal chosen between the output terminal (OUT) and the input terminal (IN) and a second terminal corresponding to the reference terminal (GND), the resistive voltage divider bridge comprising a plurality of resistive components (Ri), each resistive component (Ri) being configured such that the voltage across each resistive component corresponds to the intermediate input voltage (Vfi) or the intermediate output voltage (Vfi) of the corresponding pump stage (Si),- a multiplexer (MUX) connected to the terminals of at least one resistive component from the plurality of resistive components (Ri) and configured to select a voltage from among the voltages across the resistive components, the selected voltage corresponding to the prediction voltage (Vcp+1).

5. Charge pump system (100) according to claim 4 in which each resistive component (Ri) has between the terminals of said resistive component (Ri) a resistance value defined according to the number of pump stage(s) activated.

6. Charge pump system (100) according to any one of the preceding claims wherein each pump stage (Si) of rank i comprises a capacitive component (Cfly) comprising a first electrode connected on one side to an input of the pump stage (Si), and on the other side connected by a first switch (Intl-i) to the input of the pump stage (Si+1) of rank i+1 or the output voltage; and a second electrode connected on one side by a second switch (Int2-i) to the output terminal (VOUT) and on the other side by a third switch Int3-i to the reference terminal (GND).

7. Charge pump system (100) according to any one of the preceding claims wherein the charge pump (1) is a Dickson charge pump.

8. Charge pump system (100) according to any one of the preceding claims further comprising a microelectromechanical system (Rmems) connected at the output of the voltage regulator (LDO) between the reference terminal (GND) and an output terminal of the regulator (X).

9. Charge pump system (100) according to any one of the preceding claims wherein the number n of pump stages is between 3 and 10, for example four pump stages (Si).

10. A method for configuring the number of activated pump stages for a charging pump system (100) according to any one of claims 1 to 9 comprising the following steps: - measuring (E1) a voltage difference between the pump output voltage (Vcp) and the regulator output voltage (Vldo), - if said difference is less than a lower threshold (T1), modifying (E2) the number of activated pump stages by reducing said number of activated pump stages N, - if said difference is greater than a higher threshold (Th), generating a prediction voltage (Vcp+1), and comparing (E3) the prediction voltage (Vcp+1) to the regulator output voltage (Vldo) so as to obtain a prediction result, and, if the prediction result is greater than the lower threshold (T1), modifying (E4) the number of activated pump stages by increasing said number of activated pump stages, - if said difference is between the lower threshold and the upper threshold,maintain the number of activated pump stages N. unchanged,

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