DC / DC power supply conversion circuit

Abstract

DC / DC Power Conversion Circuit This description relates to a power conversion circuit comprising: a first node configured to receive a first voltage referenced to a second node configured to be coupled to a reference potential; a first power converter coupling the first node to a third node; a second power converter coupling a fourth node to an output node; a first capacitor coupling the third node to the fourth node; a first switch connecting the output node to the first node; and an output switch configured to connect the output node to a load. Figure for the abstract: Fig. 3

Description

Title of the invention: DC / DC power conversion circuit Technical field

[0001] The present disclosure generally relates to power conversion circuits and associated methods. Prior art

[0002] A wide variety of power conversion circuits are widely known. The present disclosure relates more particularly to switched mode power supply circuits and, more specifically, to such conversion circuits using a reservoir capacitor to instantly increase the output power. Summary of the invention

[0003] There is a need in the art for improved power conversion circuitry and methods.

[0004] One embodiment overcomes all or part of the drawbacks of known power conversion devices.

[0005] One embodiment provides a power conversion circuit comprising: - a first node configured to receive a first voltage referenced to a second node configured to be coupled to a reference potential; - a first power converter coupling the first node to a third node; - a second power converter coupling a fourth node to an output node; - a first capacitor coupling the third node to the fourth node; - a first switch connecting the output node to the first node and - an output switch configured to connect the output node to a load.

[0006] One embodiment provides a method of converting power by a circuit, said circuit comprising: - a first knot; - a first power converter coupling the first node to a third node; - a second power converter coupling a fourth node to an output node; - a first capacitor coupling the third node to the fourth node; - a first switch connecting the output node to the first node; the said method comprising: the application, on the first node, of a first voltage referenced to a second node configured to be coupled to a reference potential and connecting, via an output switch, the output node to a load.

[0007] One embodiment provides a power conversion circuit comprising, - a first node configured to receive a first voltage referenced to a second node configured to be coupled to a reference potential; - a first power converter coupling the first node to a third node; - a second power converter coupling the third node to an output node and - a first capacitor coupling the third node to a voltage supply rail; the output node being configured to be coupled to a load via an output switch.

[0008] According to one embodiment, the second power converter comprises an inductive element having a first terminal connected to a midpoint of a third switch and a fourth switch, and a second terminal connected to the output node; the third switch coupling the fourth node to said first terminal and the fourth switch coupling said first terminal to the second node.

[0009] According to one embodiment, the first power converter comprises a further inductive element having a first terminal connected to a midpoint of a fifth and a sixth switch, and a second terminal connected to the third node; the fifth switch coupling the first node to said first terminal of said further inductive element, and the sixth switch coupling said first terminal of said further inductive element to the second node.

[0010] According to one embodiment, the first power converter comprises: - a fifth switch coupling the first node to the third node, - a sixth switch coupling the third node to the second node.

[0011] According to one embodiment, during a first phase of operation, the first switch is ACTIVE, the output switch is DEACTIVE, a first and second stage alternate at a first frequency and a third and a fourth stage alternate at a second frequency.

[0012] According to one embodiment, during a second operating phase, the third and fourth steps alternate at a third frequency, the first power converter being deactivated.

[0013] According to one embodiment, during a third phase of operation, the first switch is OFF, the output switch is ON, the first and second stages alternate at a fourth frequency and the third and fourth steps alternate at a fifth frequency.

[0014] According to one embodiment: - in the first phase of operation, the first power converter is configured to operate as a DC / DC step-down converter to regulate the voltage at the third node from the first voltage to 0 V and the second power converter is configured to operate as a DC / DC step-up converter to increase the voltage at the fourth node; - in the second phase of operation, the second power converter is configured to operate as a DC / DC boost converter to increase the voltage at the fourth node to a maximum voltage value while the voltage at the third node is maintained at the reference potential and - in the third phase of operation, the first power converter is configured to operate as a DC / DC step-down converter to regulate the voltage at the third node from 0 V to the first voltage and, simultaneously, the second power converter is configured to operate as a DC / DC step-down converter to discharge the fourth node.

[0015] According to one embodiment, during the first step, the fifth switch is OFF and the sixth switch is ON and, during the second step, the fifth switch is ON and the sixth switch is OFF.

[0016] According to one embodiment: in the third step, the third switch is OFF and the fourth switch is ON, and in the fourth step, the third switch is ON and the fourth switch is OFF.

[0017] According to one embodiment, a second capacitor couples the third node to the second node.

[0018] According to one embodiment, a third capacitor couples the fourth node to the second node.

[0019] According to one embodiment, a fourth capacitor couples the output node to the second node.

[0020] According to one embodiment, the first capacitor has a capacitance of between 10 pF and 500 pF.

[0021] According to one embodiment, the first capacitor is a ceramic capacitor.

[0022] One embodiment provides an electronic device comprising: - a power source configured to provide a first voltage; - a charge; - a power conversion circuit as described above; the power source being configured to apply the first voltage to the first node; the load being connected to the output node.

[0023] According to one embodiment, the power source comprises a battery and the load is a light-emitting source. Brief description of the drawings

[0024] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0025] [Fig.l] represents a schematic view of an example of an electronic device to which the described embodiments apply;

[0026] [Fig.2] represents a schematic view of an example of a power conversion circuit;

[0027] [Fig.3] represents a schematic view of a different implementation of a power conversion circuit according to an embodiment of the present description;

[0028] [Fig.4] represents a schematic view of a different implementation of a power conversion circuit according to another embodiment of the present description;

[0029] [Fig.5] represents a timing diagram illustrating the operating steps of [Fig.3];

[0030] [Fig.6] represents another timing diagram illustrating the operating steps of [Fig.3] and

[0031] [Fig.7] represents a timing diagram illustrating the operating steps of [Fig.4], Description of the embodiments

[0032] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0033] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed.

[0034] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0035] In the following description, when referring to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0036] Unless otherwise specified, the expressions “approximately”, “approximately”, "substantially" and "in the order of" mean within 10%, preferably within 5%.

[0037] [Fig.l] represents a schematic view of an example of an electronic device to which the described embodiments apply.

[0038] The electronic device of [Fig.l] comprises a power source 102 (POWER SOURCE) configured to provide a first voltage VBAT to a power conversion circuit 104 (POWER CONVERSION CIRCUIT). The power conversion circuit 104 is coupled to a load 106 (LOAD) and is configured to provide the load 106 with an output or power signal OUT.

[0039] Depending on the applications, the electronic circuit comprises other components and elements not shown, which can also be powered from the power source 102 and / or the power conversion circuit 104.

[0040] The instantaneous voltage or current (power) of the output signal is, for example, greater than the first instantaneous current or voltage (power) provided by the power source 102.

[0041] According to the described embodiments, the power conversion circuit is a switched-mode power supply (SMPS) or a plurality of DC / DC converters coupled, or preferably connected, to a reservoir capacitor. The DC / DC converters are for example controlled by a duty cycle D.

[0042] According to an exemplary application, the load is composed of one or more laser sources, such as a vertical cavity surface emitting laser (VCSEL). In such an application, the output signal OUT consists of voltage or current pulses. Typically, the instantaneous supply voltage, current, or power of the laser source is greater than the voltage, current, or power that can be instantaneously supplied by the power source 102, and the duration of the supply pulse is in the order of magnitude of a microsecond, generally several microseconds or tens of microseconds.

[0043] The energy drawn by the load from the power conversion circuit during the power pulses is therefore very high. Depending on the power capacity of the power source, this energy requirement may cause the power source to sag. In particular, in applications where the power source 102 includes a battery, the power conversion circuit may be unable to provide the high power required by the load without sag the battery voltage. In addition, the power pulse sequence of the laser source does not allow long intervals between two pulses, which requires, for the conversion circuit power, to quickly recover additional energy from the power source, in order to power the next laser pulse. Typically, the duty cycle of the power pulse of a laser source is between 5 and 90%.

[0044] According to the described embodiments, the power conversion circuit comprises a reservoir capacitor. It is common to provide a power conversion circuit with a large input battery decoupling capacitor (greater than several tenths of a pF). However, the reservoir capacitor of the described embodiments is coupled, or preferably connected, between at least two DC / DC converters, or within a configurable DC / DC converter. More particularly, the utilization of the energy stored in the reservoir capacitor is increased.

[0045] In the described embodiments, the reservoir capacitor helps to achieve a power level (voltage and / or current) at the output OUTPUT, which may be greater than the instantaneous power, (voltage and / or current) for example the nominal power level (voltage and / or current) VBAT, provided by the power source 102, which is typically a battery.

[0046] In the described embodiments, in the case where the reservoir capacitor has a non-linear CV characteristic like ceramic multilayer capacitors, the impact of under-stressing of the reservoir capacitor on its energy storage capacity is reduced, which leads to improved utilization of the energy stored in the reservoir capacitor.

[0047] [Fig.2] represents a schematic view of an example of a power conversion circuit 104.

[0048] In the example shown, the power conversion circuit 104 comprises a first node (NVBAT) configured to receive a first voltage VBAT supplied by the power source 102 and referenced to a second node (GND) and configured to be coupled to a reference potential, for example a ground potential.

[0049] The power conversion circuit 104 comprises first and second power converters 202, 204 in series. The first converter 202 couples the first node NVBAT to a third node NVTANK(L). The second power converter 204 couples the third node NVTANK(L) to a fifth node (NVOUT).

[0050] The first power converter 202 includes an inductance element 220, for example a coil, having a first terminal 222 coupled, or preferably connected, to a common terminal of a switch 232 and another switch 230. The switch 232 has another terminal coupled, or preferably connected, to the NVBAT node and the switch 230 has another terminal coupled, or preferably connected, to the second GND node. A second terminal 226 of the coil 220 is coupled, or preferably connected, to a common terminal of switches 240 and 242. Switch 242 has another terminal coupled, or preferably connected, to node NVTANK(L), and switch 240 has another terminal coupled, or preferably connected, to the second node GND.

[0051] The second power converter 204 includes an inductance element 230, for example a coil, having a first terminal 270 coupled, or preferably connected, to a common terminal of a switch 252 and another switch 250. The switch 252 has another terminal coupled, or preferably connected, to the node NVTANK(L) and the switch 250 has another terminal coupled, or preferably connected, to the second node GND. A second terminal 272 of the coil 230 is coupled, or preferably connected, to a common terminal of the switches 260 and 262. The switch 262 has another terminal coupled, or preferably connected, to the node NVOUT, and the switch 260 has another terminal coupled, or preferably connected, to the second node GND.

[0052] In one example, the ratio of the conduction times of switches 232 and 230, or the ratio of the conduction times of switches 242 and 240, or the ratio of the conduction times of switches 262 and 260, or the ratio of the conduction times of switches 250 and 252 is a duty cycle D controlled by a pulse width modulation signal generated by a control unit 280.

[0053] The power conversion circuit 104 further comprises a first capacitor 206 (CTANK) coupling the third node NVTANK(L) to ground GND, or to a voltage supply rail VDD. The first capacitor is a reservoir capacitor, for example a ceramic capacitor with a capacitance between 10 pF and 500 pF. In one example, the power conversion circuit 104 further comprises, or is coupled to, a switch configured to connect the fifth node NVOUT to a load. In one example, this switch is switch 262 or another unillustrated switch SW_OUT.

[0054] In one example, a decoupling capacitor 212 (COUT) couples the fifth node NVOUT to the second node GND. Capacitor 212 acts, for example, as a filter.

[0055] The operation of the circuit of [Fig.2] alternates between pre-charging phases of the CTANK capacitor charging the CTANK capacitor from the power source and discharging phases (otherwise known as output current generation phases, TON power phases or power phases) generating an output current or voltage (energy) from the fifth node NVOUT, for example to the load 106. In one example, both the pre-charging and discharging phases may be active simultaneously.

[0056] In operation, in a precharge phase, the load is disconnected. This disconnection can be achieved by switching the output switch SW_OUT, or the switch 262, or a switch present in the load, to OFF, i.e. by putting it in a non-conducting state. The first power converter 202 operates as a DC / DC step-down converter until the voltage at NVTANK(L) reaches VBAT. It then operates as a step-up converter until the voltage at NVTANK(L) reaches a maximum value V TANK(max) > VBAT. The second power converter 204 remains OFF.

[0057] Once the reservoir capacitor is charged, the precharge phase is completed and high impedance voltage regulation, or pulse skip keying (PSK), is performed by the first power converter 202, with the second power converter 204 remaining disabled.

[0058] In a discharge phase (TON), the second power converter 204 operates as a DC / DC step-down converter if the voltage NVTANK(L)>VBAT and as a DC / DC step-up converter if NVTANK(L) <VBAT. Il permet de générer une forme d'onde de courant de sortie à partir du condensateur réservoir 206. La tension VTANK aux bornes du condensateur réservoir est ainsi déchargée et active le premier convertisseur de puissance 202 qui fonctionne alors en convertisseur élévateur DC / DC. Pendant le fonctionnement du convertisseur élévateur 204, le courant de sortie est discontinu et peut ainsi générer une grande ondulation du courant de sortie qui peut être indésirable. De même, lors de l'opération d’augmentation, les performances dynamiques du convertisseur élévateur modifient les performances dynamiques souhaitées, par exemple la vitesse de la régulation.As a result, the step-up operation of converter 204 is not desired, but necessary for the efficient use of the energy available in reservoir capacitor 206.

[0059] During the discharge phase, the first converter 202 may operate to provide a portion of the battery power to the reservoir capacitor 206 CTANK, to equalize the input current drawn from the battery and possibly decrease the value of the reservoir capacitor CTANK. In another example, the first converter 202 may also be disabled.

[0060] According to the example of [Fig.2], the potential energy Edischarge stored in the capacitor CTANK and available for discharge can be formulated according to the following equation 1:

[0061] Edischarge ~^TANk{ T AN K{max)~^ T AN K(min)}

[0062] where Ctank corresponds to the capacitance of the capacitor 206 CTANK, VTANK(max) corresponds to the VTank voltage between the node NVTANK(L) and the second node GND at the beginning of the discharge phase, and VTANK(mm) corresponds to the voltage between the node

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] NVTANK(L) and the second node GND at the end of the discharge phase. It can be seen that the available energy Edischarge increases with the square of VTANK(max)* The increase in energy storage or similarly the decrease in the CTAnk value and therefore the volume of the capacitor CTAnk is obtained by increasing VTANK(max)* The energy delivered by the CTANK capacitor during a discharge phase can be formulated according to the following equation 2: ^OUT — OUT^OUTTON (2) where VOUT is the voltage supplied to the fifth node NVOUT during the discharge phase, I0Ut is the current drawn from the fifth node NVOUT by the load during the discharge phase, and T0N is the duration of the discharge phase. Ideally, Edischarge — EOUT, This leads to the following equation 3 and equation 4 which are valid for VTANK(min) > VOut: y __ 1 ^TANKi^fANKimoxf^TANKiend'l) (3) fi _ ^ON^OUT^OUT (4) ^TANK~ 1 7 ANKimaxj ' TANKimin)) An advantage of the described embodiments is that, with a tank capacitor on the input side of the power conversion circuit, higher voltage variations are allowed across the TANK capacitor compared to the voltage variations of the capacitor used as an input decoupling capacitor at the battery terminal. A higher voltage variation across the TANK capacitor electrodes means that the capacitor absorbs and delivers a larger amount of energy between the charging and discharging phases. A higher voltage variation across CTAnk therefore leads to a better utilization of the capacitor volume, i.e., a better capacitor-volume efficiency, compared to capacitors with a small voltage variation (ripple) used to decouple the input, e.g., the battery voltage. An advantage of the circuit of [Fig.2] is that it allows the reservoir capacitor to be discharged below the load voltage 106. This means that more energy is obtained from the capacitor and therefore the necessary value of the capacitor (volume and cost) is reduced (e.g. by 50%). A disadvantage of the circuit in [Fig.2] is that alternating between the "buck" and "boost" configurations is complicated and the efficiency is low since the number of switches involved is large. High input / output current ripples are also created at the switching frequency due to the discontinuous current during the boost mode, and simultaneously the dynamic performance, i.e. the regulation speed, is reduced. The various embodiments propose a power conversion circuit comprising a first node configured to receive a first voltage, for example from a power source, referenced to a second node configured to be coupled to a reference potential; a first power converter coupling the first node to a third node; a second power converter coupling a fourth node to a fifth node; a first capacitor coupling the third node to the fourth node; a first switch connecting the fifth node to the first node and a second switch configured to connect the fifth node to the load 106.

[0072] The proposed power conversion circuits allow for improved utilization of the energy stored in the reservoir capacitor, with fewer switches than the example in [Fig.2], which improves overall efficiency. This also allows the reservoir capacitor to be discharged below the load voltage.

[0073] The proposed power conversion devices avoid using first and second converters in both buck / boost mode during the TON discharge phase. This reduces output ripple and allows for high transient regulation speed because the output converter is in buck mode during discharge.

[0074] [Fig. 3] represents a schematic view of a different implementation of a power conversion circuit 104 according to an embodiment of the present description.

[0075] In the example shown, the power conversion circuit 104 comprises a first power converter 302 connected in series to a first reservoir capacitor 306 (CTANK) itself connected in series to a second power converter 304.

[0076] In one example, the first capacitor (CTANK) has a capacitance of between 10 pF and 500 pF and is, for example, a ceramic capacitor.

[0077] The power conversion circuit 104 comprises a first node (NVBAT) configured to receive the first voltage (VBAT) referenced to a second node configured to be coupled to a reference potential (GND).

[0078] The first power converter 302 couples the first node NVBAT to a third node NVTANK(L) which is coupled, or preferably connected, to a first electrode of the tank capacitor CTANK. The first power converter 302 is configured to operate continuously as a buck converter, i.e., the voltage at the third node NVTANK(L) is lower than the voltage at the NVBAT node.

[0079] The second power converter 304 couples a fifth node (NVOUT), which is the output of the power conversion device, to a fourth node (NVTANK(R)), which is coupled, or preferably connected, to a second electrode of the reservoir capacitor 306, CTANK. The second power converter 304 operates as a buck converter during discharge and as a boost converter during precharge.

[0080] The first capacitor 306 couples the third node NVTANK(L) to the fourth node NVTANK(R). In other words, the capacitor 306 is connected in series between the first and second power converters 302, 304.

[0081] In the example shown, the power conversion circuit 104 further comprises a first switch 336 (SW_PRECHARGE) connecting the fifth node NVOUT to the first node NVBAT.

[0082] In the example shown, the power conversion circuit 104 further comprises a second switch 346 (SW_OUT) configured to connect the fifth node NVOUT to the load 106. The two switches 336 and 346 are static switches, that is to say they switch at low frequency, corresponding to the change of the precharge and discharge phases, relative to the switching frequency of the switches of the first and second power converters 302, 304.

[0083] In the example shown, the second power converter 304 comprises an inductive element 330 (LR) having a first terminal connected to a midpoint (NM2) of a third and a fourth switch (SW_BBH, SW_BBL), and a second terminal coupled, or preferably connected, to the fifth node NVOUT.

[0084] The third switch SW_BBH couples the fourth node NVTANK(R) to the first terminal of the LR coil, i.e., to the midpoint NM2, and the fourth switch SW_BBL couples the first terminal of the LR coil to the second node GND.

[0085] The first power converter 302 comprises an inductive element 320 (LL) having a first terminal coupled, or preferably connected, to a midpoint (NM1) of a fifth and a sixth switch (SW_BH, SW_BL). A second terminal of the inductive element is coupled, or preferably connected, to the third node NVTANK(L). In other words, the inductive element 320 couples the node NVTANK(L) to the midpoint NM1.

[0086] The fifth switch SW_BH couples the first node NVBAT to the first terminal of the inductive element LL, i.e. to the midpoint NM1. The sixth switch SW_BL couples the first terminal of the inductive element LL to the second node GND.

[0087] In the example shown, a second decoupling capacitor 356 (COUT1) couples the third node NVTANK(L) to the second node GND. An optional third capacitor 358 (C'TANK) further couples the fourth node NVTANK(R) to the second node (GND). A fourth decoupling capacitor 364 (C0UT2) further couples the fifth node to the second GND node.

[0088] The inductive elements 320, 330 are, for example, coils.

[0089] In operation, during a first precharge operation phase (PRECHARGE 1), the switch SW_PRECHARGE is ON and the second switch SW_OUT is OFF. The DC / DC converter 302 operates in step-down mode and decreases the voltage VTANK(L) at the node NVTANK(L) from VTANK(L)_max (e.g. VBAT) to VTANK(L)_min, e.g. 0V. During this phase, the converter 304 operates in boost mode, maintaining or increasing VTANK(R) to a level higher than VBAT. The voltage of the capacitor CTANK therefore increases.

[0090] During a second precharge operation phase (PRECHARGE2), the first power converter 320 is preferably disabled and maintains VTANK(L)= 0V with the switch SW_BH OFF and SW_BL ON, or it regulates the output voltage to VTANK(L)_min. During this phase, the converter 304 operates as a booster, increasing VTANK(R) to the level VTANK(R)_max. The voltage of the reservoir capacitor 206 therefore increases.

[0091] During a third operating phase (TON), also called the power-up phase, the first switch SW_PRECHARGE is OFF, the second switch SW_OUT is ON. Both power converters 302 and 304 operate in step-down modes. The first converter 302 provides an increase in the voltage VTANK(L), while the second converter 304 discharges the voltage VTANK(R) to the load. During this phase, the voltage across the reservoir capacitor VTANK is decreased. While the majority of the output power is provided by the reservoir capacitor 206, a portion of the power is also provided by the power source VBAT. In the case where the power source is a battery, the current can be approximately written as Ibat = I0Ut * D320 * D304 , where Dx indicates for the duty cycle of the respective converter x = 302,304.The VTANK(R) voltage can be discharged down to VDD to allow the converter to then operate in boost mode during the precharge phase.

[0092] After the feeding phase, a new first precharge phase is carried out to be able to carry out a new feeding phase etc. In reality, many precharge and feeding phases are alternated.

[0093] During the first precharge phase PRECHARGE 1, a first and a second switching step alternate at a first frequency and a third and a fourth switching step alternate at a second frequency. In one example, during the first step, the fifth switch SW_BH is OFF and the sixth switch SW_BL is ON, and during the second step, the fifth switch SW_BH is ON and the sixth switch SW_BL is OFF. In another example, in the third step, the third switch SW_BBH is OFF and the fourth switch SW_BBL is ON, and in the fourth step, the third switch SW_BBH is ON and the fourth switch SW_BBL is OFF.

[0094] During the second phase of precharge operation PRECHARGE!, the third and fourth switching stages alternate at a third frequency.

[0095] During the third TON operating phase, the first and second switching stages alternate at a fourth frequency and the third and fourth switching stages alternate at a fifth frequency.

[0096] With respect to the alternation frequency of the precharge and supply phases, the switching steps alternate at a high switching frequency. As an exemplary embodiment, the switching of the first, second, third, fourth and fifth alternation frequencies is greater than one kilohertz, for example at a fixed value between a few kilohertz and one megahertz. In one example, the ratio of the conduction times of the switches SW_BH and SW_BL, or the conduction times of the switches SW_BBH and SW_BBL are defined by a duty cycle. The duty cycle is controlled by a signal, for example in pulse width modulation mode, generated by a control unit for example similar to the control unit 280.

[0097] First, second, third, fourth and fifth frequencies are adjusted for example to be similar or different or for some of them to be similar.

[0098] The peak current drawn from the power source is for example limited by the use of the optional capacitor 358 C'TANK referenced to ground.

[0099] [Fig.4] represents a schematic view of a different implementation of a power conversion circuit 104 according to another embodiment of the present description.

[0100] The power conversion circuit of [Fig.4] is similar to the power conversion circuit of [Fig.3] except that the inductive element 320 of the first power converter 302 is not present. In other words, the node NVTANK(L) is directly connected to the midpoint NM1.

[0101] The operation of the circuit of [Fig.4] is similar to the operation of the example of [Fig.3] except that, during the precharge phases, the switches SW_BH and SW_BL are in a static configuration. Their switching allows VTANK(L) to be abruptly brought back to the reference potential GND. Another difference is that, during the power supply phase TON, the switches SW_BH and SW_BL are in a static configuration. Their switching allows VTANK(L) abruptly from the GND reference potential to VBAT.

[0102] An additional advantage of the example of [Fig.4] is that the circuit is simpler and the energy density is increased since only one coil is used.

[0103] This makes it possible to produce the circuit of [Fig.3] with a single inductive element, and a single power stage switching at high frequency.

[0104] As a result, the circuit of [Fig.4] is simpler because it contains only one power converter switching at a high switching frequency, and the energy density is increased since only one coil is used. However, the abrupt switching of SW_BH and SW_BL may generate an unwanted peak at the output, which may disturb the accuracy of the output power.

[0105] [Fig.5] represents a timing diagram illustrating the operating steps of [Fig.3].

[0106] More particularly, the diagram of [Fig.5] illustrates the voltage at nodes NVTANK(L) and NVTANK(R) and the resulting voltage across the reservoir capacitor (voltage across CTANK) as a function of time.

[0107] At the end of a previous power supply phase TON, the voltage of the reservoir capacitor VTANK(R)_min - VTANK(L)_max is low and must be recharged. Preferably, the voltage VTANK(L)_max is close to VDD, and VTANK(R)_min is slightly higher than VDD in order to allow the converter 304 to operate in boost mode during the next precharge phase. The charge phase comprises two precharge phases: PRECHARGE 1 and PRECHARGE!.

[0108] During the first phase of operation PRECHARGEl, the first power converter 302 operates as a DC / DC buck converter (i.e. VBAT>VTANK(L)) to regulate the voltage VTANK(L) at the third node NVTANK(L) from VTANK(L)_max, e.g. VBAT (e.g. 2.5V) to VTANK(L)_min, e.g. VTANK(L)_min= 0V (ground level). Meanwhile, NLOAD = VBAT and the second power converter 304 operates as a DC / DC boost converter to raise the voltage VTANK(R) at the fourth node NVTANK(R) from the voltage close to VLOAD of the load to an intermediate value VTANK(R)_maxl. The resulting voltage across the reservoir capacitor 306 VTANK(R)_maxl increases to about 5 to 8V for example.

[0109] During the second operating phase PRECHARGE2, the second power converter 304 is configured to operate as a DC / DC boost converter to increase the voltage VTANK(R) at the fourth node NVTANK(R) up to a maximum voltage value VTANK(MAX) (e.g. from the intermediate value up to 10V or up to 14V) while the voltage at the third node NVTANK(L) is maintained at the reference potential VTANK(L)_min, GND, OV, by the first power converter 302. The resulting voltage across the reservoir capacitor 306 increases during the first and second operating phases PRECHARGE 1 and PRECHARGE! from the initial value at the end of a previous discharge phase TON (Vtank(R)_min-Vtank(L)_max) to (VTANK(R)_max - VTANK(L)_min). The voltage across the reservoir capacitor 306 then reaches approximately 10V or up to 14V for example. This means that the variation of the voltage across the reservoir capacitor can be increased.

[0110] During the third TON operation phase, the first power converter 302 operates as a DC / DC buck converter to regulate and increase the voltage VTANK(L) at the third node NVTANK(L) from 0V to the first voltage VBAT (approximately 2.5V for example), and simultaneously the second power converter 304 operates as a DC / DC buck converter and regulates the output voltage from VTANK(R) to VLOAD, with VTANK(R) being assumed to be greater than VLOAD, in order to discharge the fourth node NVTANK(R) down to for example 6V. This increases the time during which VTANK(R)_max approaches VBAT, i.e. the amount of energy that can be extracted from the capacitor CTANK 306 is increased.In other words, the voltage at the node NVTANK(L) is continuously increased by the first power converter 302 which operates as a DC / DC buck converter, while the node NVTANK(R) is continuously discharged by the second power converter 304 which operates as a DC / DC buck converter to provide the output power. The reservoir capacitor is therefore apparently charged by the first power converter during the supply phase. In other words, during this supply phase Ton, a part of the energy is also transferred from the power source 102. This is convenient because it allows a reasonable power sharing between the power delivered by the reservoir capacitor CTANK and the power delivered by the power source 102. .

[0111] The operating example of [Fig.3] shows that the first power converter 302 is only used as a DC / DC buck converter, which implies fewer switches, a high transient regulation speed and a low output ripple. The second power converter 304 operates in a buck mode during the TON supply phase which is essential to maintain a high regulation speed and a low ripple current injected at the output node.

[0112] Another advantage of the example of [Fig.3] is that a high discharge of the reservoir capacitor 306 is achieved with a discharge of VTANK(MAX) (e.g. 10-14V) down to the load voltage (e.g. 6V) minus the first voltage VBAT (e.g. 2.5V). In contrast, existing solutions would provide a discharge of the reservoir capacitor 306 only from VTANK(MAX) (e.g. 10-14V) to the load voltage (e.g. 6V). More energy is therefore extracted from the reservoir capacitor 306.

[0113] [Fig.6] represents another timing diagram illustrating the operating steps of [Fig.3].

[0114] More precisely, the voltage VTANK(R) present at the node NVTANK(R), the charging current (ILOAD), the voltage VTANK(L) present at the node NVTANK(L) and the current drawn from the power source (IB AT) are represented for a sequence comprising the first precharge phases and the power supply phase. The first precharge phase PRECHARGE 1 is represented between a time t2 and a time t3. The second precharge phase PRECHARGE! is represented between a time t3 and a time t4. The power supply phase TON is represented between a time t5, after t4, and a time t6. Due to the representation window, the power supply phase TON continues after t6 until a time t1 and the cycle can repeat itself.

[0115] During a period of time between times t1 and t2, the feeding phase is completed, ILOAD drops to 0.1TBAT current decreases by more than a factor of 2, VTANK(R) increases very slightly and VTANK(L) continues to increase slightly as IB AT decreases relatively slowly.

[0116] Between times t2 and t3, VTANK(R) is slightly increased to 7V, ILOAD is maintained at zero, VTANK(L) decreases almost linearly from 2.5V (VBAT) to approximately 0V, and IB AT is slightly increased linearly.

[0117] Between times t3 and t4, VTANK(R) increases linearly from 7V to 10V, ILOAD remains at 0, VTANK(L) remains stable and IB AT remains stable.

[0118] At time t4, charging is complete. The first power converter 302 maintains VTANK(L) at a low voltage, i.e., ground, while the second power converter 304 maintains the voltage VTANK(R) at VTANK(R)_max. This can be achieved by pulse skipping or hysteretic regulation of VTANK(R)_max. For a period of time between time t4 and time t5, VTANK(R), VTANK(L), and ILOAD remain stable.

[0119] During the TON supply phase, ILOAD remains stable at a high level, VTANK(R) decreases almost linearly to reach 7 V at tl, VTANK(L) increases linearly from 0 to 2.5 V (VBAT) and IB AT increases almost linearly to a maximum at tl.

[0120] [Fig.7] represents another timing diagram illustrating the operating steps of [Fig.4]. The example of [Fig.7] more specifically represents VTANK(R), ILOAD and a control signal (SWITCH_CONTROL) of one of the switches SW_BH or SW_BL during part of a supply phase followed by a precharge phase.

[0121] Between a time t4a, for example between times t4 and t5 of [Fig.6], and a time t5 similar to time t5 of [Fig.6], VTANK(R) is kept stable at 14V, ILOAD is at 0 and the switch control signal is kept at a low level. The period between t4a and time t5 corresponds to the end of a precharge phase.

[0122] To start a TON power supply phase, from time t5 to time t5a, VTANK(R) is discharged almost linearly by the second power converter 304 while ILOAD increases rapidly to be further kept stable by a feedback control loop, and the switches SW_BL and the control signals of the switches SW_BH are kept at a low level.

[0123] At time t5a, the switch control signal is raised to a high level which causes VTANK(L) to rise almost simultaneously from 0 to VBAT. As a result, VTANK(R) also rises instantaneously from about 8 V to about 11 V, which causes a small problem (circled in the diagram) on the output load supply. This operation, however, brings more energy from the reservoir capacitor allowing more power to be delivered to the output.

[0124] From time t5a to time t7, VTANK(R) decreases almost linearly to 8V, ILOAD remains stable and the switch control signal is maintained at a high level.

[0125] After time t7, ILOAD drops to 0, the switch control signal is held high, and VTANK(R) increases almost linearly to precharge reservoir capacitor 306 again. In an example not shown, the switch control signal also switches during precharging to bring voltage VTANK(L) to GND.

[0126] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, the switches may be implemented by transistors, the inductive elements may be implemented by coils.

[0127] Additionally, the operating sequences of the power converter 302 when operating as a DC / DC step-down converter can be arbitrarily modified to achieve the best performance.

[0128] Finally, the practical implementation of the described embodiments and variants is within the reach of the person skilled in the art from the functional indications given above. In particular, regarding the example of [Fig. 3], in which the inductive element 320 and the switch SW_BH can be exchanged so that the inductive element 320 couples the node NVBAT and the midpoint NM1, and the switch SW_BH couples the inductive element 320 to the node NVTANK(L). In this case, the capacitor tank is not connected in series between the first and second power converters 302, 304, but instead couples the NVTANK(L) node to the second GND node. Thus, the NVTANK(L) and NVTANK(R) nodes are merged into a single node. Furthermore, in this case, the SW_PRECHARGE switch no longer couples the NVBAT node but instead couples the midpoint NM1 to the NVOUT node. Furthermore, in this case, the inductive element 330 and the SW_BBH switch are swapped so that the inductive element 330 couples the NVTANK(L) node to the midpoint NM2 and the SW_BBH switch couples the midpoint NM2 to the NVOUT node.

Claims

Claims

1. A power conversion circuit comprising: - a first node (NVBAT) configured to receive a first voltage (VBAT) referenced to a second node configured to be coupled to a reference potential (GND); - a first power converter (302) coupling the first node (NVBAT) to a third node (NVTANK(L)); - a second power converter (304) coupling a fourth node (NVTANK(R)) to an output node (NVOUT); - a first capacitor (CTANK) coupling the third node (NVTANK(L)) to the fourth node (NVTANK(R)); - a first switch (SW_PRECHARGE) connecting the output node (NVOUT) to the first node (NVBAT) and - an output switch (SW_OUT) configured to connect the output node (NVOUT) to a load.

2. A power conversion circuit comprising, - a first node (NVBAT) configured to receive a first voltage (VBAT) referenced to a second node configured to be coupled to a reference potential (GND); - a first power converter (202) coupling the first node (NVBAT) to a third node (NVTANK(L)); - a second power converter (204) coupling the third node (NVTANK(L)) to an output node (NVOUT) and - a first capacitor (CTANK) coupling the third node (NVTANK(L)) to a voltage supply rail (VDD); the output node (NVOUT) being configured to be coupled to a load via an output switch.

3. A circuit according to claim 1 or 2, wherein the second power converter (304) comprises an inductive element (LR) having a first terminal connected to a midpoint (NM2) of a third and a fourth switch (SW_BBH, SW_BBL), and a second terminal connected to the output node (NVOUT); the third switch (SW_BBH) coupling the fourth node (NVTANK(R)) to said first terminal, and the fourth switch (SW_BBL) coupling said first terminal to the second node (GND).

4. A circuit according to any one of claims 1 to 3, wherein the first power converter (302) comprises a further element inductive (LL) having a first terminal connected to a midpoint (NM1) of a fifth and a sixth switch (SW_BH, SW_BL), and a second terminal connected to the third node (NVTANK(L)); the fifth switch (SW_BH) coupling the first node (NVBAT) to said first terminal (NLR) of said other inductive element (LL), and the sixth switch (SW_BL) coupling said first terminal of said other inductive element (LL) to the second node (GND).

5. Circuit according to any one of claims 1 to 4, wherein the first power converter (302) comprises: - a fifth switch (SW_BH) coupling the first node (NVBAT) to the third node (NVTANK(L)), - a sixth switch (SW_BL) coupling the third node (NVTANK(L)) to the second node (GND).

6. A circuit according to any one of claims 1 to 5 in their dependence on claim 1, wherein during a first operating phase (PRECHARGE1), the first switch (SW_PRECHARGE) is ON, the output switch (SW_OUT) is OFF, a first and a second switching stage of the fifth and sixth switches alternate at a first frequency and a third and a fourth switching stage of the third and fourth switches alternate at a second frequency.

7. A circuit according to claim 6 in its dependency on claim 1, wherein during a second operating phase (PRECHARGE!), the third and fourth stages alternate at a third frequency, the first power converter being deactivated.

8. A circuit according to claim 6 or 7, wherein during a third operating phase (TON), the first switch (SW_PRECHARGE) is OFF, the output switch (SW_OUT) is ON, the first and second stages alternate at a fourth frequency and the third and fourth stages alternate at a fifth frequency.

9. Circuit according to claim 8 in its dependency on claim 7, in which: - in the first operating phase (PRECHARGE 1), the first power converter is configured to operate as a DC / DC step-down converter to regulate the voltage at the third node (NVTANK(L) from the first voltage (VBAT) to 0 V and the second power converter is configured to operate as a DC / DC step-up converter to increase the voltage at the fourth node (NVTANK(R));- in the second operating phase (PRECHARGE!), the second power converter is configured to operate as a DC / DC boost converter to increase the voltage at the fourth node (NVTANK(R)) to a maximum voltage value (VTANK(MAX)) while the voltage at the third node (NVTANK(L)) is maintained at the reference potential (GND) and - in the third operating phase (TON), the first power converter is configured to operate as a DC / DC buck converter to regulate the voltage at the third node (NVTANK(L)) from 0 V to the first voltage (VBAT), and simultaneously the second power converter is configured to operate as a DC / DC buck converter to discharge the fourth node (NVTANK(R)).;

10. A circuit according to any one of claims 6 to 9, wherein during the first step, the fifth switch (SW_BH) is OFF and the sixth switch (SW_BL) is ON, and during the second step, the fifth switch (SW_BH) is ON and the sixth switch (SW_BL) is OFF.

11. A circuit according to any one of claims 6, or 7 to 10 as dependent on claim 6, wherein: during the third step, the third switch (SW_BBH) is OFF and the fourth switch (SW_BBL) is ON, and during the fourth step, the third switch (SW_BBH) is ON and the fourth switch (SW_BBL) is OFF.

12. A circuit according to any one of claims 1 to 11, wherein a second capacitor (COUT1) couples the third node (NVTANK(L)) to the second node (GND).

13. A circuit according to any one of claims 1 to 12 as dependent on claim 1, wherein a third capacitor (C'TANK) couples the fourth node (NVTANK(R)) to the second node (GND).

14. A circuit according to any one of claims 1 to 13, wherein a fourth capacitor (COUT2) couples the output node to the second node (GND).

15. A circuit according to any one of claims 1 to 14, wherein the first capacitor (CTANK) has a capacitance of between 10 pF and 500 pF.

16. A circuit according to any one of claims 1 to 15, wherein the first capacitor (CTANK) is a ceramic capacitor.

17. Electronic device comprising: - a power source configured to provide a first voltage (VBAT); - a load; - a power conversion circuit according to any one of claims 1 to 16; the power source being configured to apply the first voltage to the first node (NVBAT); the load being connected to the output node (NVOUT).

18. An electronic device according to claim 17, wherein the power source comprises a battery and the load is a light emitting source.

19. A method of converting power by a circuit according to any one of claims 1 to 16, said method comprising: applying, on the first node (NVBAT), a first voltage referenced to a second node (GND) configured to be coupled to a reference potential and connecting, via an output switch (SW_OUT), the output node to a load.

Images