CN118739838A - Charge Pump Device - Google Patents

Abstract

Embodiments of the present disclosure relate to charge pump devices. A device includes a charge pump, wherein each charge pump has an input for receiving an input voltage, another input for receiving a periodic control signal, and an output for delivering an output voltage. Each charge pump is selectively enabled or disabled. A first circuit delivers an error signal based on the difference between the output voltage and a reference voltage. A second circuit changes an operating parameter of the charge pump based on the error signal. A third circuit compares a current value of the operating parameter with two thresholds, and controls one of an increase in the number of enabled charge pumps, a decrease in the number of enabled charge pumps, and a maintenance of the number of enabled charge pumps based on the result of the threshold comparison.

Description

Charge Pump Device

Priority claim

This application claims the benefit of priority of French patent application No. 2303132 filed on March 30, 2023, the contents of which are incorporated herein by reference in their entirety to the maximum extent permitted by law.

Technical Field

The present disclosure relates generally to electronic circuits, such as integrated circuits, and more particularly to apparatus or circuits for providing a direct current (DC) supply voltage.

Background Art

Many known devices allow delivering a DC supply voltage. Switching mode power supplies (SMPS), charge pump devices, low dropout regulators (LDO) are examples of such devices.

A known charge pump arrangement comprises several charge pumps connected in parallel. Each charge pump of such an arrangement receives the same input voltage shared between all charge pumps and delivers an output voltage at a node connected to the outputs of all charge pumps.

However, these known arrangements comprising several charge pumps connected in parallel have several disadvantages, for example regarding their power consumption, such as their quiescent consumption associated with switching to the charge pumps.

There is a need to address all or some of the disadvantages of known charge pump arrangements, in particular known arrangements comprising several charge pumps connected in parallel and configured to deliver a DC output voltage of the arrangement.

Summary of the invention

One embodiment provides a device comprising: a charge pump, each charge pump having a first input, a second input, and an output, the first input being connected to a first node configured to receive an input voltage of the charge pump, the second input being configured to receive a periodic control signal for controlling switching of the charge pump, the output being connected to a second node, the second node being configured to deliver an output voltage of the device, each charge pump being configured to be selectively enabled or disabled; a first circuit configured to deliver a signal indicating an offset between an output voltage and a reference voltage; a second circuit configured to change an operating parameter of the charge pump based on the signal; and a third circuit configured to compare a current value of the parameter with a first threshold and a second threshold, and to control one of an increase in the number of enabled charge pumps, a decrease in the number of enabled charge pumps, and maintenance of the number of enabled charge pumps based on a result of the comparison.

According to one embodiment, the parameter belongs to the group comprising the frequency of the control signal, the input voltage, the threshold of a MOS transistor configured to implement the switching to the charge pump, and the gate-source voltage level of said transistor.

According to one embodiment, the third circuit is configured to control: when the result of the comparison indicates that the current value is on a first same side of the first threshold and the second threshold, the increase in the number of enabled charge pumps; if the result of the comparison indicates that the current value is included between the first threshold and the second threshold, the maintenance of the number of enabled charge pumps; and if the result of the comparison indicates that the current value is on a second same side of the first threshold and the second threshold, the decrease in the number of enabled charge pumps.

According to one embodiment, the third circuit includes a first comparator, a second comparator, and a processing circuit, wherein the first comparator is used to compare the current value of the parameter with the first threshold value, and the second comparator is used to compare the current value of the parameter with the second threshold value, and the processing circuit is configured to receive an output signal from each of the first comparator and the second comparator, and based on these output signals, deliver a signal that selects the state of each charge pump in the charge pump between an enabled state and a disabled state.

According to one embodiment, the parameters are selected among the frequency and input voltage of the control signal, and the third circuit is configured to control: if the result of the comparison indicates that the current value is greater than the first threshold and the second threshold, the number of enabled charge pumps is increased; if the result of the comparison indicates that the current value is included between the first threshold and the second threshold, the number of enabled charge pumps is maintained; if the result of the comparison indicates that the current value is less than the first threshold and the second threshold, the number of enabled charge pumps is reduced.

According to one embodiment, the parameter is the input voltage and the frequency of the control signal is preferably constant.

According to one embodiment, the second circuit is configured to increase the input voltage if the output voltage is lower than the reference voltage, and to decrease the input voltage if the output voltage is higher than the reference voltage.

According to one embodiment: the first circuit includes an operational amplifier having a non-inverting input, an inverting input, and an output, the non-inverting input being configured to receive an output voltage, the inverting input being configured to receive a reference voltage, and the output being configured to deliver a signal indicating an offset between the output voltage and the reference voltage; and the second circuit includes a P-channel MOS transistor connected between a first node and a node configured to receive a supply potential, the gate of the transistor being connected to the output of the operational amplifier of the first circuit.

According to one embodiment, the parameter is the frequency of the control signal and the input voltage is preferably constant.

According to one embodiment, the second circuit is configured to increase the frequency if the output voltage is lower than the reference voltage, and to decrease the frequency if the output voltage is higher than the reference voltage.

According to one embodiment, the third circuit is configured to start the first delay when the result of the comparison corresponds to an increase in the number of enabled charge pumps and to control the increase at the end of the first delay only if the result of the comparison is the same as at the beginning of the first delay.

According to one embodiment, the third circuit is configured to start the second delay when the result of the comparison corresponds to a reduction in the number of enabled charge pumps and to control the reduction at the end of the second delay only if the result of the comparison is the same as at the beginning of the second delay.

Another embodiment provides a time-of-flight sensor comprising the device as described above and an array of pixels, each pixel comprising a single-photon avalanche diode, the device being configured to supply an output voltage of the device to the pixel array.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned features and advantages and other features and advantages will be described in detail in the following description of specific embodiments given by way of example and not limitation with reference to the accompanying drawings, in which:

FIG1 illustrates, partly schematically in block form, an example of a charge pump arrangement;

FIG. 2 illustrates, partially schematically in block form, an example embodiment of a charge pump arrangement; and

FIG. 3 illustrates, partly schematically in block form, another example embodiment of a charge pump arrangement.

DETAILED DESCRIPTION

Similar features are designated by similar reference numerals in the various drawings. Specifically, common structural and/or functional features between various embodiments may have the same reference numerals and may have the same structure, dimensions, and material properties.

For the sake of clarity, only operations and elements useful for understanding the embodiments described herein are illustrated and described in detail. Specifically, various known electronic devices (e.g., integrated circuits) and various known systems or applications in which charge pump devices can be provided to deliver DC supply voltages are not described in detail, and the embodiments and alternative embodiments of the charge pump devices described herein are compatible with these known circuits, systems, and applications.

Unless otherwise stated, when reference is made to two elements being connected together, this means a direct connection without any intervening elements other than conductors, and when reference is made to two elements being coupled together, this means the two elements may be connected or they may be coupled via one or more other elements.

In the following disclosure, unless otherwise stated, when referring to absolute position qualifiers such as terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers such as terms "above", "below", "higher", "lower", etc., or orientation qualifiers such as "horizontal", "vertical", etc., reference is made to the orientation shown in the figure.

Unless otherwise indicated, the expressions "about," "approximately," "substantially," and "on the order of" mean within 10%, and preferably within 5%.

Fig. 1 partly schematically illustrates in block form an example of a charge pump arrangement 1. The arrangement 1 is configured to deliver a DC voltage Vout.

The device 1 comprises N charge pumps CPi, where N is an integer greater than or equal to 2, preferably greater than or equal to 3, and i is an integer index from 1 to N. In the example of FIG. 1 , N is equal to 6 (the device comprises charge pumps CP1, CP2, CP3, CP4, CP5, CP6), provided that the number N may actually be different from 6, for example greater than 6.

Each charge pump CPi includes an input 100, which is configured to receive an input voltage Vin of the charge pump CPi. Each charge pump CPi is a switched capacitor charge pump. Therefore, each charge pump CPi includes an input 102, which is configured to receive a clock signal clk. The signal clk is a periodic signal for controlling the charge pump CPi, and more specifically, for controlling the switching to each charge pump CPi. The signal clk is the same for all charge pumps CPi. Each charge pump CPi includes an output 104, which is configured to deliver the output voltage of the charge pump.

In other words, all charge pumps CPi have their input 100 connected to the same node 106 configured to receive the input voltage Vin of the charge pumps CPi, and all charge pumps have their output 104 connected to the same node 108 configured to deliver the voltage Vout of the device 1 .

Each charge pump CPi is configured to deliver an output voltage Vout of a value equal to K times the value of its input voltage Vin. Preferably, the charge pumps CPi are identical to one another.

The device 1 further comprises a circuit 110. The circuit 110 is configured to deliver a signal Err, e.g. a voltage, indicating the value of an offset between the value of the voltage Vout and the value of the reference voltage Vref. The circuit 110, for example, receives the voltage Vout or a signal indicating the value of the voltage Vout, and the voltage Vref or a signal indicating the value of the voltage Vref.

As an example, circuit 110 includes an operational amplifier 112 having a first input (e.g., an inverting input (-) in FIG. 1 ) configured to receive a voltage Vref, a second input (e.g., a non-inverting input (+) in FIG. 1 ) connected to node 108 to receive a voltage Vout, and an output configured to deliver a signal Err.

As an alternative example, the circuit 110 includes an operational amplifier 112 , but a first input of which receives a signal indicating the value of the reference voltage Vref and a second input of which receives a signal indicating the value of the voltage Vout.

Based on the signal Err, the device 1 controls the operating parameters of the charge pump CPi so as to maintain the voltage Vout equal to the voltage Vref. To this end, the device 1 comprises a circuit 120 configured to change (or adjust or regulate) the operating parameters according to the signal Err.

In the example of Fig. 1, this parameter is the value of the voltage Vin. Preferably, the frequency of the signal clk as a further operating parameter of the charge pump CPi is then constant or at least not dependent on the signal Err.

Circuit 120 is then configured to increase voltage Vin if voltage Vout is less than voltage Vref, and to decrease voltage Vin if voltage Vout is greater than voltage Vref. For example, circuit 120 receives signal Err at input 122 of circuit 120 and delivers voltage Vin at output 124 of circuit 120, which is connected to node 106. In other words, circuit 120 delivers voltage Vin in this example.

As an example, circuit 120 includes a P-channel MOS (“metal oxide semiconductor”) transistor or PMOS transistor 126. Transistor 126 is connected between a node 128 configured to receive a supply voltage VDD and an output 124 of circuit 120 (which is node 106 in this example). Transistor 126 is controlled, for example, by signal Err based on signal Err. For example, transistor 126 has its source connected to node 108, its drain connected to output 124, and its gate connected to input 122 of circuit 120.

Each charge pump CPi has an output impedance which limits the maximum amount of current that the charge pump CPi can deliver at the node 108 to maintain the voltage Vout at the same value as the voltage Vref. Providing several charge pumps in parallel allows the maximum amount of current that the device 1 can deliver at the node 108 to be increased compared to a device 1 comprising only a single charge pump CPi. Therefore, the number N of charge pumps CPi is determined by the maximum consumption of the load connected to the node 108 and supplied with the voltage Vout, for example under the worst PVT (“Process Voltage Temperature”) conditions.

However, increasing the number N of charge pumps CPi of device 1 to ensure that device 1 will be able to supply power to the load under worst PVT conditions has the disadvantage of increasing the consumption of device 1, for example because it increases the static consumption of device 1 related to power losses or leakages in the charge pumps CPi.

When the load powered by the device 1 is configured to operate according to at least two power supply modes (e.g. a low power mode and a nominal consumption mode), in other, not illustrated examples of the device 1, provision is made for disabling one or more charge pumps only according to the power supply mode the load is in. In particular, in a power supply mode in which the load is considered to be of maximum consumption (e.g. the nominal consumption mode), all charge pumps CPi are enabled, although in this power supply mode the load is not continuously at its maximum consumption under the worst PVT conditions. In fact, the knowledge of the power supply mode of the load only gives an indication of the range of consumption values in which the current value of the load consumption lies, without giving the current value of the load consumption.

Therefore, although the above describes adjusting the number of enabled charge pumps in the device 1 according to the power supply mode of the load, the number of enabled charge pumps is most of the time greater than the number of charge pumps required to meet the current consumption of the load.

One proposal of the present invention is to adjust the number of enabled charge pumps CPi in a device having charge pumps of the type described with respect to FIG. 1 not based on knowledge of the power supply mode of the loads powered by the device, but based on the current consumption of the loads. To this end, it is provided to compare the current value of an operating parameter of the charge pump, which is adjusted according to the signal Err and is an image (or representation) of the current (or instantaneous) consumption of the loads, with two threshold values, and to adjust the number of enabled charge pumps according to the result of such comparison.

An example embodiment of such an apparatus will now be described with reference to FIGS. 2 and 3 .

FIG. 2 illustrates, partly schematically in block form, an example embodiment of an apparatus 2 having a charge pump.

The device 2 is similar to the previously described device 1 and only the differences between the two devices 1 and 2 are highlighted here. Therefore, everything indicated for the device 1 applies to the device 2 unless otherwise stated.

Compared to device 1, the charge pumps CPi of device 2 are configured to be selectively enabled or disabled, respectively. For example, compared to the charge pumps CPi of device 1, the charge pumps CPi of device 2 each include another input 200 configured to receive a signal EN, which indicates to the charge pump whether it should be enabled or disabled. As an example, the signal EN is a multi-bit digital signal common to all charge pumps CPi, and different combinations of the states of the bits of the signal EN indicate or control which of the N charge pumps CPi of device 2 are enabled and which are disabled. For example, the signal EN includes N bits, each bit corresponds to a charge pump CPi, and when the bit is in a first binary state and a second binary state, respectively, the enabled state and the disabled state of the charge pump are controlled.

Compared with the device 1 , the device 2 further includes a circuit 202 .

The circuit 202 is configured to compare the current value of the operating parameter of the charge pump CPi (which is adjusted according to the signal Err as described above) with the first threshold Vth1 and the second threshold Vth2. For example, the circuit 202 receives a signal indicating the current value of the parameter.

The circuit 202 is also configured to control one of an increase in the number of enabled charge pumps CPi, a decrease in the number of enabled charge pumps CPi, and a maintenance of the number of enabled charge pumps CPi based on the result of the comparison. Therefore, the circuit 202 delivers a signal EN on the output 204 of the circuit 202. In other words, according to the result of the comparison, the circuit 202 implements a decrease in the number of enabled charge pumps CPi, or an increase in the number of enabled charge pumps CPi, or no change in the number of enabled charge pumps CPi. In other words, the circuit 202 is configured to adjust the number of enabled charge pumps CPi according to the comparison result of the current value of the operating parameter of the charge pump CPi with the thresholds Vth1 and Vth2.

More specifically, the two threshold values Vth1 and Vth2 define three value ranges, i.e., a first range of values, all values of which are less than both the threshold value Vth1 and the threshold value Vth2, a second range of values, all values of which are included between the threshold value Vth1 and the threshold value Vth2, and a third range of values, all values of which are higher than both the threshold value Vth1 and the threshold value Vth2. The result of the comparison of the current value of the operating parameter of the charge pump CPi with the two threshold values Vth1 and Vth2 allows the circuit 202 to determine whether the current value is within the second range, then the circuit 202 does not change the number of enabled charge pumps CPi, if the current value is within one of the first range and the third range of values, then the circuit 202 increases the number of enabled charge pumps CPi, or if the current value is within the other of the first range and the third range of values, then the circuit 202 reduces the number of enabled charge pumps CPi.

In other words, circuit 202 is configured to control: when the result of the comparison indicates that the current value of the parameter is on the same first side of the threshold values Vth1 and Vth2, for example, when the current value is higher or lower than both the threshold values Vth1 and Vth2, respectively, the increase in the number of enabled charge pumps CPi; if the result of the comparison indicates that the current value is included between the two threshold values Vth1 and Vth2, the maintenance of the number of enabled charge pumps CPi; and if the result of the comparison indicates that the current value of the parameter is on the same second side of the threshold values Vth1 and Vth2, for example, when the current value is lower or higher than both the threshold values Vth1 and Vth2, respectively, the reduction in the number of enabled charge pumps CPi.

In the example of FIG. 2 , the operating parameter of the charge pump CPi (which is adjusted according to the signal Err and whose current value is compared with the thresholds Vth1 and Vth2 to adjust the number of enabled charge pumps CPi) is the voltage Vin at the output node 124 of the circuit 120 .

In this example, if the load powered by the device 2 consumes too much considering the number of enabled charge pumps CPi of the device 2, the voltage Vout will drop below the voltage Vref, which causes the value of the voltage Vin to increase. Conversely, if the load powered by the device 2 consumes insufficiently considering the number of enabled charge pumps CPi, the voltage Vout will rise above the voltage Vref, which causes the value of the voltage Vin to decrease.

Therefore, in this example, if the constant value of the voltage Vin is higher than the thresholds Vth1 and Vth2, this means that the load consumes too much for the number of enabled charge pumps CPi, and the circuit 202 then controls the number of enabled charge pumps CPi to increase. On the contrary, if the constant value of the voltage Vin is lower than the thresholds Vth1 and Vth2, this means that the device 2 delivers too much power to the load compared to the consumption of the load, and the circuit 202 then controls the number of enabled charge pumps CPi to decrease. In the case where the number of enabled charge pumps is adapted to the consumption of the load, the voltage Vout varies little compared to the voltage Vref, resulting in the current value of the voltage Vin being relatively stable and remaining included between the thresholds Vth1 and Vth2, and the circuit 202 then does not change the number of enabled charge pumps CPi.

As an example, when the circuit 202 has to increase or decrease the number of enabled charge pumps CPi, the circuit 202 updates its signal EN accordingly.

As an example, in order to compare the thresholds Vth1 and Vth2 with the current values of the operating parameters of the charge pump CPi adjusted based on the signal Err, the circuit 202 includes two comparators. The first comparator of the two comparators compares the current value of the parameter (Vin in the example of FIG. 2) with the threshold value Vth1, and the second comparator of the two comparators compares the current value of the parameter (Vin in the example of FIG. 2) with the threshold value Vth2. Each of the two comparators outputs an output signal indicating the result of the comparison achieved. Still as an example, the circuit 202 also includes a processing circuit, which receives the output signals of the two comparators and delivers a signal EN based on these signals, which indicates to each charge pump CPi whether it should be enabled. In other words, the signal EN selects the state of each charge pump CPi from an enabled state and a disabled state.

As an example, the charge pumps CPi of the device 2 are organized into groups (or slices), for example, into at least two groups, preferably into at least three groups. In this case, each charge pump CPi belongs to only one of these groups. For example, in FIG. 2 , N=6 charge pumps CPi are organized into three groups, each with two charge pumps CPi, for example, the first group includes charge pumps CP1 and CP2, the second group includes charge pumps CP3 and CP4, and the third group includes charge pumps CP5 and CP6.

According to an embodiment in which the charge pumps CPi are organized into groups, when the number of charge pumps CPi enabled by the circuit 202 is increased, the circuit 202 controls the simultaneous enabling of all charge pumps of at least one group (e.g., a single group) in addition to the already enabled charge pumps CPi. Conversely, when the number of charge pumps CPi enabled by the circuit 202 is decreased, the circuit 202 controls the simultaneous disabling of all charge pumps CPi of at least one group (e.g., a single group) in addition to the already disabled charge pumps CPi.

As an alternative, at each increase in the number of charge pumps CPi enabled by circuit 202, circuit 202 controls the enabling of a single charge pump CPi in addition to controlling the charge pumps CPi that are already enabled, and conversely, at each decrease in the number of charge pumps CPi enabled by circuit 202, circuit 202 controls the disabling of a single charge pump CPi in addition to controlling the charge pumps CPi that are already disabled.

As another alternative, the number of additional charge pumps CPi enabled at each increase in the number of charge pumps CPi enabled by circuit 202 may be different from the number of additional charge pumps CPi disabled at each decrease in the number of charge pumps CPi enabled by circuit 202 .

According to one embodiment, when the result of comparing the current value of the operating parameter of the charge pump CPi with the thresholds Vth1 and Vth2 indicates to the circuit 202 that the number of enabled charge pumps CPi should be increased, that is, when the result of the comparison corresponds to an increase in the number of enabled charge pumps CPi, the circuit 202 is configured to start the delay Temp1, and to implement (i.e., control) the increase in the number of enabled charge pumps CPi at the end of the delay Temp1 only if the result of the comparison at the end of the delay Temp1 is unchanged compared to the result of the comparison at the beginning of the delay Temp1.

Alternatively, when the result of comparing the current value of the operating parameter of the charge pump CPi with the thresholds Vth1 and Vth2 indicates to the circuit 202 that the number of enabled charge pumps CPi should be increased, the circuit 202 immediately controls the increase in the number of enabled charge pumps CPi without delay Temp1.

According to one embodiment, when the result of comparing the current value of the operating parameter of the charge pump CPi with the thresholds Vth1 and Vth2 indicates to the circuit 202 that the number of enabled charge pumps CPi should be reduced, that is, when the result of the comparison corresponds to a reduction in the number of enabled charge pumps CPi, the circuit 202 is configured to start the delay Temp2, and to implement (i.e., control) the reduction in the number of enabled charge pumps CPi at the end of the delay Temp2 only if the result of the comparison at the end of the delay Temp2 is unchanged compared to the result of the comparison at the start of the delay Temp2.

Alternatively, when the result of comparing the current value of the operating parameter of the charge pump CPi with the thresholds Vth1 and Vth2 indicates to the circuit 202 that the number of enabled charge pumps CPi should be reduced, the circuit 202 immediately controls the reduction of the number of enabled charge pumps CPi without delay Temp2.

In some embodiments, circuit 202 implements both delays Temp1 and Temp2. In other embodiments, circuit 202 does not implement either of delays Temp1 and Temp2. In some further embodiments, circuit 202 implements only one of the two delays Temp1 and Temp2.

In a particular embodiment, the circuit 202 implements only the delay Temp2. The absence of the delay Temp1 allows the device 2 to react immediately to an increase in the consumption of the load, which allows the voltage Vout to drop too much. In this case, providing the delay Temp2 allows avoiding instabilities of the device 2, even if the number of enabled charge pumps CPi alternates between successive close increases and decreases.

In the example of FIG. 2 , the operating parameter of the charge pump CPi (which is adjusted based on the signal Err and whose current value is compared with the thresholds Vth1 and Vth2) is the voltage Vin. Therefore, the circuit 202 receives a signal representing (or indicating) the value of the voltage Vin. For example, as illustrated in FIG. 2 , the circuit 202 directly receives the voltage Vin. As an alternative embodiment, the circuit 202 receives a signal, such as a voltage, whose value is determined by the value of the voltage Vin (e.g., the output voltage of the voltage divider bridge powered by the voltage Vout).

Although the example in FIG. 2 illustrates the case where the operating parameter of the charge pump CPi (which is adjusted based on the signal Err and whose current value is compared with the thresholds Vth1 and Vth2) is the voltage Vin, in other cases, the parameter may be the frequency of the signal clk for controlling the switching to the charge pump CPi, the thresholds of the MOS transistors that implement the switching to the charge pump CPi, or even the values of the gate-source voltages corresponding to the cut-off state and the on-state of these MOS transistors. In fact, in other example embodiments, the circuit 120 is configured to adjust the values of the thresholds of the MOS transistors that implement the switching to the charge pump CPi, for example by adjusting the back-gate voltages of these transistors, for example so that when the voltage Vout is less than the voltage Vref and moves away from the voltage Vref, the value of the threshold decreases, and so that when the voltage Vout is higher than the voltage Vref and moves away from the voltage Vref, the value of the threshold increases. In this case, the signal indicating the current value of the thresholds of these MOS transistors is, for example, the back-gate voltage of these transistors that allows the thresholds of these transistors to be modulated. In yet another example embodiment, the circuit 120 is configured to adjust the value of the gate-source voltage corresponding to the off state of the MOS transistors implementing the switching to the charge pump CPi and/or the value of the gate-source voltage corresponding to the on state of these transistors, for example in order to increase or decrease the time required to charge and/or discharge the gate capacitance of the transistors in order to increase or decrease the maximum amount of current delivered by the device 2 to the load within one cycle of the signal clk.

More generally, the operating parameter of the charge pump CPi (which is adjusted based on the signal Err and whose current value is compared with the thresholds Vth1 and Vth2) is selected from the group consisting of the voltage Vin, the frequency of the signal clk, the thresholds of the MOS transistors that implement the switching to the charge pump CPi, and the level of the gate-source voltage of these transistors. In other words, the operating parameter of the charge pump CPi (which is adjusted based on the signal Err and whose current value is compared with the thresholds Vth1 and Vth2) is a parameter representing the current or instantaneous power consumption of the load connected to the node 108 of the device 2.

FIG. 3 partly schematically illustrates in block form another exemplary embodiment of a device 3 having a charge pump.

The device 3 is similar to the previously described device 2 and only the differences between the two devices 2 and 3 are highlighted here. Therefore, everything indicated for the device 2 applies to the device 3 unless otherwise stated.

Compared to device 2, in which the operating parameter of the charge pump CPi, whose current value is compared with thresholds Vth1 and Vth2, is the voltage Vin, in device 3 this parameter is the frequency of the signal clk for controlling the charge pump CPi. In this case, the voltage Vin is preferably constant.

Compared to device 2, circuit 120 of device 3 is therefore not configured to increase or decrease voltage Vin when voltage Vout becomes lower than voltage Vref or higher than voltage Vref, respectively. In device 3, circuit 120 is configured to increase or decrease the frequency of signal clk when voltage Vout becomes lower than voltage Vref or higher than voltage Vref, respectively.

Thus, in the device 3, the output 124 of the circuit 120 is not connected to the node 106 and does not deliver the voltage Vin. In fact, the output 124 then controls the frequency of the signal clk. For example, the output 124 of the circuit 120 delivers the signal clk, as illustrated in FIG3 . As an alternative example, the output 124 of the circuit 120 delivers a control signal indicating a target value of the frequency of the signal clk, which is received by a circuit for generating the signal clk, which circuit is configured so that the value of the frequency of the signal clk it delivers is equal to the target value indicated by the control signal.

Furthermore, compared to the circuit 202 of the device 2, the circuit 202 of the device 3 is configured to receive a signal indicating the same current value of the frequency of the signal clk. For example, the circuit 202 of the device 3 receives the signal clk and is configured to determine the value of the frequency of the received signal clk. As an alternative example, the circuit 202 receives a signal indicating the current value of the frequency of the signal clk, such as a control signal delivered by the circuit 120 of the device 3 to the circuit for generating the signal clk, and indicates the value of the frequency of the signal clk that the generating circuit must deliver. As another alternative example, the circuit 120 delivers the signal clk directly, and also delivers a signal indicating the current value of the frequency of the signal clk to the circuit 202.

In device 3, as for the voltage Vin in device 2, when the value of the frequency of the signal clk increases, this indicates that the consumption of the load powered by the voltage Vout is too high for the number of enabled charge pumps CPi, and conversely, when the value of the frequency of the signal clk decreases, this indicates that the consumption of the load powered by the voltage Vout is insufficient for the number of enabled charge pumps CPi.

Therefore, in the device 3, if the current value of the frequency of the signal clk is higher than the thresholds Vth1 and Vth2, this means that the load consumes too much for the number of enabled charge pumps CPi, and the circuit 202 then controls the number of enabled charge pumps CPi to increase. On the contrary, if the current value of the frequency of the signal clk is less than the thresholds Vth1 and Vth2, this means that the device 3 delivers too much power to the load compared to the consumption of the load, and the circuit 202 then controls the number of enabled charge pumps CPi to decrease. In the case where the number of enabled charge pumps is adapted to the consumption of the load, the voltage Vout varies little compared to the voltage Vref, resulting in the current value of the voltage Vin being relatively constant and remaining included between the thresholds Vth1 and Vth2, and the number of enabled charge pumps CPi is not changed.

In the examples of Figures 2 and 3 described above, circuit 120 is configured to increase the value of an operating parameter of the charge pump (voltage Vin in Figure 2, frequency of signal Clk in Figure 3) when voltage Vout is less than voltage Vref and moves away from voltage Vref, and to decrease the value of the parameter when voltage Vout is higher than voltage Vref and moves away from voltage Vref.

However, according to the operating parameter that the circuit 120 adjusts based on the signal Err, the circuit 120 is configured to: reduce the value of the parameter when the voltage Vout is less than the voltage Vref and moves away from the voltage Vref, and increase the value of the parameter when the voltage Vout is higher than the voltage Vref and moves away from the voltage Vref. In this case: if the current value of the parameter is less than the thresholds Vth1 and Vth2, this means that the load consumes too much for the number of enabled charge pumps CPi, and the circuit 202 then controls the number of enabled charge pumps CPi to increase; if the current value of the parameter is higher than the thresholds Vth1 and Vth2, this means that the enabled charge pumps CPi deliver too much power to the load compared to the consumption of the load, and the circuit 202 then controls the number of enabled charge pumps CPi to decrease; and if the current value of the parameter is included between the thresholds Vth1 and Vth2, this means that the number of enabled charge pumps is adapted to the consumption of the load, and the circuit 202 then does not change the number of enabled charge pumps CPi.

In the above-described example embodiments and example alternatives with charge pumps, although never indicated, because this is obvious to a person skilled in the art, when the result of the comparison of the threshold values Vth1 and Vth2 with the current values of the operating parameters of the charge pumps CPi indicates to the circuit 202 that it should increase the number of enabled charge pumps, this increase in the number of enabled charge pumps is possible to be achieved by the circuit 202 only if the circuit 202 keeps at least one disabled charge pump CPi of the N charge pumps CPi. Symmetrically, although never indicated, because this is obvious to a person skilled in the art, when the result of the comparison of the threshold values Vth1 and Vth2 with the current values of the operating parameters of the charge pumps CPi indicates to the circuit 202 that it should reduce the number of enabled charge pumps, this reduction in the number of enabled charge pumps is possible to be achieved by the circuit 202 only if the circuit 202 keeps at least one enabled charge pump CPi of the N charge pumps CPi once the reduction in the number of enabled charge pumps is achieved.

However, in practice, if the number N is chosen to ensure that the load connected to the node 108 is conveniently powered regardless of PVT conditions, there will be no situation where the number of enabled charge pumps should be increased when N charge pumps CPi are already enabled.

According to one embodiment, a charge pump device of the type previously described in conjunction with FIGS. 2 and 3 is implemented into a light sensor (e.g., a time-of-flight sensor). The sensor includes an array of pixels, each pixel having a single-photon avalanche photodiode (SPAD). The device is then configured to power the array of pixels (e.g., each pixel of the array, e.g., each SPAD of the sensor).

Various embodiments and variations have been described. Those skilled in the art will appreciate that the specific features of these embodiments may be combined, and those skilled in the art will readily conceive of other variations.

Finally, based on the functional description provided above, the actual implementation of the embodiments and variations described herein is within the capabilities of those skilled in the art. Specifically, those skilled in the art are capable of implementing circuits 110, 120, and 202 based on the above functional disclosure.

Claims (17)

1. A device comprising: a plurality of charge pumps, wherein each charge pump has a first input connected to a first node configured to receive an input voltage, a second input configured to receive a periodic control signal for controlling switching to the charge pump, and an output connected to a second node configured to deliver an output voltage, and wherein each charge pump is configured to be selectively enabled or disabled; a first circuit configured to deliver a signal indicative of an offset between the output voltage and a reference voltage; a second circuit configured to change an operating parameter of the charge pump based on the signal; and A third circuit is configured to compare the current value of the operating parameter with the first threshold and the second threshold, and based on the result of the comparison, control one of an increase in the number of enabled charge pumps, a decrease in the number of enabled charge pumps, and maintenance of the number of enabled charge pumps. 2 . The apparatus of claim 1 , wherein the operating parameter comprises a frequency of the control signal applied to all of the plurality of charge pumps. The apparatus of claim 1 , wherein the operating parameter comprises the input voltage. 4 . The apparatus of claim 1 , wherein the operating parameter comprises a threshold of a MOS transistor configured to enable switching in each of the charge pumps. 5 . The apparatus of claim 1 , wherein the operating parameter comprises a gate-source voltage level of a MOS transistor configured to implement switching in each of the charge pumps. 6. The apparatus of claim 1 , wherein the third circuit is configured to control: when the result of the comparison indicates that the current value is on a first same side of the first threshold and the second threshold, increasing the number of the charge pumps enabled; If the result of the comparison indicates that the current value is included between the first threshold and the second threshold, maintaining the number of the charge pumps enabled; and If the result of the comparison indicates that the current value is on a second same side of the first threshold and the second threshold, the number of the charge pumps enabled is reduced. 7. The apparatus of claim 6 , wherein the third circuit comprises a first comparator for comparing the current value of the operating parameter with the first threshold, a second comparator for comparing the current value of the operating parameter with the second threshold, and a processing circuit configured to receive an output signal of each of the first comparator and the second comparator and to deliver a signal for selecting a state of each of the charge pumps between an enabled state and a disabled state based on the output signals. 8. The apparatus of claim 1 , wherein the operating parameter is a frequency of the control signal, and the third circuit is configured to control: if the result of the comparison indicates that the current value is greater than the first threshold and the second threshold, increasing the number of the charge pumps enabled; If the result of the comparison indicates that the current value is included between the first threshold and the second threshold, maintaining the number of the charge pumps enabled; and If the result of the comparison indicates that the current value is less than the first threshold and the second threshold, the number of enabled charge pumps is reduced. 9. The apparatus of claim 1 , wherein the operating parameter is the input voltage, the third circuit being configured to control: if the result of the comparison indicates that the current value is greater than the first threshold and the second threshold, increasing the number of the charge pumps enabled; If the result of the comparison indicates that the current value is included between the first threshold and the second threshold, maintaining the number of the charge pumps enabled; and If the result of the comparison indicates that the current value is less than the first threshold and the second threshold, the number of enabled charge pumps is reduced. 10. The apparatus of claim 1, wherein the operating parameter is the input voltage, and the frequency of the control signal is constant and the same for all charge pumps. 11 . The apparatus of claim 10 , wherein the second circuit is configured to increase the input voltage if the output voltage is lower than the reference voltage, and to decrease the input voltage if the output voltage is higher than the reference voltage. 12. The device according to claim 10, wherein: the first circuit comprising an operational amplifier having a non-inverting input configured to receive the output voltage, an inverting input configured to receive the reference voltage, and an output configured to deliver the signal indicative of the offset between the output voltage and the reference voltage; and The second circuit includes a P-channel MOS transistor connected between the first node and a node configured to receive a power supply potential, a gate of the P-channel MOS transistor being connected to the output of the operational amplifier of the first circuit. 13. The apparatus of claim 1, wherein the operating parameter is the frequency of the control signal and the input voltage is constant and the same for all charge pumps. 14 . The apparatus of claim 13 , wherein the second circuit is configured to increase the frequency if the output voltage is lower than the reference voltage, and to decrease the frequency if the output voltage is higher than the reference voltage. 15. The apparatus of claim 1 , wherein the third circuit is configured to apply a first delay when the result of the comparison corresponds to an increase in the number of the enabled charge pumps, and to control the increase at the end of the first delay only if the result of the comparison is the same as at the beginning of the first delay. 16. The apparatus of claim 1 , wherein the third circuit is configured to apply a second delay when the result of the comparison corresponds to a reduction in the number of the enabled charge pumps, and to control the reduction at the end of the second delay only if the result of the comparison is the same as at the beginning of the second delay. 17. A time-of-flight sensor, comprising: The device according to claim 1; and an array of pixels, each of the pixels comprising a single photon avalanche diode; wherein the device is configured to supply the output voltage of the device to the pixel array.