Charge balancing control method and circuit for an electrical stimulation device

Abstract

The application relates to the field of integrated circuits and electric stimulation, and discloses a charge balance control method and circuit for an electric stimulation device. The method is characterized in that the energy storage inductor in the switching power converter is deeply multiplexed with the power switch group, the full-bridge power switch group and the recovery switch at the system level, the polarization energy at the electrode interface is sent back to the input voltage end through the energy storage and energy release of the inductor after the stimulation is completed, the residual charge monitoring circuit is combined to sample the two ends of the electrode and compare with the preset threshold value, a closed loop iterative active recovery is formed, and only when the residual charge deviation is less than the threshold value, the passive discharge switch is allowed to be closed to eliminate the residual potential, and the active recovery and the passive discharge are mutually exclusive. The method considers the recycling of the polarization energy and the controllable elimination of the residual charge under the premise of minimizing the hardware resources.

Description

Technical Field

[0001] This application relates to the fields of integrated circuits and electrical stimulation technology, and in particular to an electrode charge balance control method and circuit for an electrical stimulation device. Background Technology

[0002] Electrode stimulation technology is widely used in various scenarios requiring the application of controlled electrical signals to an external load. For example, in implantable neurostimulators, microelectrodes need to continuously output stimulation pulses over implantation cycles lasting several years to drive specific functional responses; in external rehabilitation training electrostimulators, electrodes need to repeatedly output stimulation signals of a wide range of intensities under load conditions with varying impedance characteristics, using constant current or constant voltage; in the stimulation front end of brain-computer interface systems, multi-channel electrodes need to perform high-frequency bidirectional stimulation and rapid charge balancing within limited chip area and power consumption budgets. A common technical requirement in these applications is that after each stimulation cycle, polarization charges inevitably accumulate at the interface between the electrode and the external load due to electrochemical or capacitive effects. If these polarization charges cannot be eliminated promptly and effectively, the interface polarization voltage will continuously shift, threatening the long-term safety of the external load and the electrochemical stability of the electrode itself.

[0003] Existing technologies primarily eliminate residual charge through passive short-circuit discharge or active compensation pulses. Passive short-circuit discharge directly short-circuits the electrodes after stimulation, relying on the interface's own impedance for natural discharge. However, this method cannot recover energy accumulated on the interface capacitance, and the transient current generated by the short circuit under large residual voltage can cause localized temperature rise and energy waste. While active compensation pulses offer higher balancing accuracy, they typically require additional battery power to generate the compensation signal, leading to a significant increase in system power consumption over wide current ranges or under heavy load stimulation conditions. Although inductor-based energy recovery schemes have been proposed, existing solutions often involve independent configurations of the power converter and the recovery path, resulting in hardware resource redundancy. Furthermore, existing technologies lack systematic solutions for handling residual deviations caused by device mismatch and non-ideal conversion efficiency after active recovery, and for coordinating the timing constraints between the active recovery path and the passive discharge path at the hardware level. Therefore, there is an urgent need for a charge balance control method and circuit that can achieve both the recovery and reuse of interface polarization energy and the controllable elimination of residual charge while minimizing hardware resources. Summary of the Invention

[0004] The purpose of this application is to provide a charge balance control method and circuit for an electrical stimulation device to solve the problems mentioned in the background art.

[0005] This application provides a charge balance control method for an electrical stimulation device, the electrical stimulation device including a switching power converter with an energy storage inductor, a full-bridge power switch group, a recovery circuit, a passive discharge switch connected across the electrodes, and a residual charge monitoring circuit; the electrodes are used to connect to an external load; the method includes: Stimulation steps: The switching power converter generates a supply voltage based on the input voltage via the energy storage inductor, controls the full-bridge power switch group to turn on to drive the electrode to output a stimulation signal, and generates polarization charge and stores polarization energy at the electrode interface; Active energy recovery step: After the stimulation signal output ends, the passive discharge switch remains open; some switches in the full-bridge power switch group are cross-multiplexed with the recovery circuit, and the energy storage inductor and some power switches in the switching power converter are also multiplexed to form an active energy recovery path. The polarization energy is converted into the magnetic energy of the energy storage inductor through the inductor energy storage sub-stage, and then the magnetic energy is sent back to the input voltage terminal through the inductor discharge sub-stage. In the stimulation step, the energy storage inductor undertakes the voltage conversion and energy storage function, and in the active energy recovery step, it undertakes the polarization energy conversion function. The switches in the full-bridge power switch group undertake the stimulation current path in the stimulation step and the recovery current path in the active energy recovery step. Residual charge monitoring step: The residual charge monitoring circuit samples the two ends of the electrode to obtain the residual charge deviation after the active energy recovery step, and compares the residual charge deviation with a preset threshold to generate a comparison result; Closed-loop iteration and conditional passive discharge steps: The comparison result is used to determine the subsequent charge balance path; if the comparison result indicates that the residual charge deviation is greater than or equal to the preset threshold, the active energy recovery step and the residual charge monitoring step are triggered to be executed again according to the comparison result, forming a closed-loop iteration; if the comparison result indicates that the residual charge deviation is less than the preset threshold, the passive discharge switch is closed to physically short-circuit the two ends of the electrode to perform passive discharge and eliminate the residual potential deviation; wherein, during the execution of the active energy recovery step, the passive discharge switch remains open and operates mutually exclusive with the active energy recovery path.

[0006] In a preferred embodiment, the full-bridge power switch group includes a first bridge arm upper arm switch (S5), a first bridge arm lower arm switch (S6), a second bridge arm upper arm switch (S7), and a second bridge arm lower arm switch (S8); the power switch group of the switching power converter includes a first power switch (S1), a second power switch (S2), a third power switch (S3), and a fourth power switch (S4); the recycling circuit includes a first recycling switch (S9) and a second recycling switch (S12); and the passive discharge switch is S10.

[0007] In a preferred embodiment, the stimulation step includes a positive stimulation mode in which: the second bridge arm upper arm switch (S7) and the first bridge arm lower arm switch (S6) are turned on, and current flows from the power supply voltage terminal through S7 to one end of the electrode, passes through the external load, and then flows through S6 to the reference ground, thus completing the output of the positive stimulation signal; The active energy recovery step corresponding to the positive stimulus includes the inductive energy storage sub-stage and the inductive energy release sub-stage: In the inductor energy storage sub-stage, the first recovery switch (S9), the second bridge arm upper arm switch (S7), and the third power switch (S3) are controlled to be turned on. The polarization voltage stored at the electrode interface drives the polarization current to flow through S7 and S3 into the energy storage inductor, converting the polarization energy into the magnetic energy of the energy storage inductor, forming a positive active energy recovery path. During the inductor energy release phase, the first power switch (S1) and the fourth power switch (S4) are turned on, and the energy storage inductor sends the magnetic energy back to the input voltage terminal via S1.

[0008] In a preferred embodiment, the stimulation step includes a reverse stimulation mode, in which: the first bridge arm upper arm switch (S5) and the second bridge arm lower arm switch (S8) are turned on, and current flows from the power supply voltage terminal through S5 to one end of the electrode, passes through the external load, and then flows through S8 to the reference ground, thus completing the reverse stimulation signal output; The active energy recovery step corresponding to the reverse stimulus includes the inductor energy storage sub-stage and the inductor energy release sub-stage: In the inductor energy storage sub-stage, the first bridge arm upper arm switch (S5), the third power switch (S3), and the second recovery switch (S12) are controlled to be turned on. The interface potential generated by reverse polarization drives the polarization current to flow through S5 and S3 into the energy storage inductor, converting the polarization energy into the magnetic energy of the energy storage inductor, forming the reverse active energy recovery path. During the inductor energy release phase, the first power switch (S1) and the fourth power switch (S4) are turned on, and the energy storage inductor sends the magnetic energy back to the input voltage terminal via S1.

[0009] In a preferred embodiment, the electrical stimulation device further includes a stimulation current source and a voltage stimulation switch (S11) and a current / voltage stimulation selection module; the method further includes a stimulation mode switching step: When the current / voltage stimulation selection module selects current stimulation, the voltage stimulation switch is turned off (S11) and the stimulation current source is enabled. The stimulation current source and the full-bridge power switch group output a current stimulation signal to the electrode. When the current / voltage stimulation selection module selects voltage stimulation, the stimulation current source is turned off and the voltage stimulation switch is turned on (S11), and the voltage stimulation signal is directly output to the electrode through the full-bridge power switch group using the power supply voltage. The conduction signal of the voltage stimulation switch (S11) and the enable signal of the stimulation current source are mutually exclusive, and the conduction state of the voltage stimulation switch (S11) and the enable state of the stimulation current source are not simultaneously established at any time.

[0010] In a preferred embodiment, the switching power converter is a buck-boost converter, which enables the energy storage inductor to cooperate with the power switch group to convert the input voltage to a supply voltage higher or lower than the input voltage in the stimulation step, and to return the polarization energy of the electrode interface to the input voltage terminal in the active energy recovery step.

[0011] This application provides an electrode charge balance circuit, including: A switching power converter includes an energy storage inductor and a power switch assembly. Its power input is connected to an external power source, and its power output is used to provide the supply voltage. A full-bridge power switch assembly is connected to the power output terminal of the switching power converter and is used to drive the electrodes to output stimulation signals based on the supply voltage, so that polarization charges are generated at the electrode interface and polarization energy is stored; the electrodes are used to connect to an external load. The energy recovery circuit includes a recovery switch, one end of which is connected to the electrode and the other end to the energy storage inductor. After the stimulation signal output ends, the recovery circuit is used to cross-multiplex with some switches in the full-bridge power switch group and some power switches in the switching power converter, using the energy storage inductor to form an active energy recovery path, thus returning the polarization energy to the external power supply terminal via inductor storage and inductor discharge. The energy storage inductor performs voltage conversion and energy storage functions during the power supply phase and polarization energy conversion functions during the recovery phase. The switches in the full-bridge power switch group serve as stimulation current paths during the stimulation phase and recovery current paths during the recovery phase. The residual charge monitoring circuit has its sampling input terminal connected to both ends of the electrode to sample and obtain the residual charge deviation and compare it with a preset threshold to generate a comparison result; its control output terminal is connected to the trigger terminal of the recovery circuit and the controlled terminal of the passive discharge switch respectively; when the comparison result indicates that the residual charge deviation is greater than or equal to the preset threshold, the control output terminal triggers the recovery circuit to continue to perform active energy recovery, forming a closed-loop iteration. A passive discharge switch is connected across the two ends of the electrode. The passive discharge switch is closed in control only when the comparison result indicates that the residual charge deviation is less than the preset threshold to physically short-circuit the two ends of the electrode for passive discharge and eliminate the residual potential deviation. During the operation of the active energy recovery path, the passive discharge switch remains open and operates mutually exclusive with the active energy recovery path.

[0012] In a preferred embodiment, the full-bridge power switch group includes a first bridge arm upper arm switch (S5), a first bridge arm lower arm switch (S6), a second bridge arm upper arm switch (S7), and a second bridge arm lower arm switch (S8); the power switch group of the switching power converter includes a first power switch (S1), a second power switch (S2), a third power switch (S3), and a fourth power switch (S4); the recycling circuit includes a first recycling switch (S9) and a second recycling switch (S12); and the passive discharge switch is S10. The active energy recovery path after positive stimulation is formed by the first recovery switch (S9), the second bridge arm upper arm switch (S7), the third power switch (S3), and the energy storage inductor; the active energy recovery path after reverse stimulation is formed by the second recovery switch (S12), the first bridge arm upper arm switch (S5), the third power switch (S3), and the energy storage inductor; the two recovery paths share the third power switch (S3) and the energy storage inductor, and during the inductor energy release stage, they share the first power switch (S1) and the fourth power switch (S4) to send the magnetic energy back to the external power supply.

[0013] In a preferred embodiment, the device further includes a stimulation current source, a voltage stimulation switch (S11), and a current / voltage stimulation selection module; the stimulation current source is connected in series between the full-bridge power switch group and the reference ground; the voltage stimulation switch (S11) is connected in parallel with the stimulation current source; the control output terminal of the current / voltage stimulation selection module is connected to the voltage stimulation switch (S11) and the stimulation current source for switching between current stimulation mode and voltage stimulation mode; wherein, the conduction signal of the voltage stimulation switch (S11) and the enable signal of the stimulation current source are mutually exclusive.

[0014] This application provides an electrical stimulation system, including the aforementioned electrode charge balancing circuit and an external load connected to the electrodes of the electrode charge balancing circuit; the electrical stimulation system recovers and reuses interface polarization energy by performing closed-loop iterative active energy recovery and mutually exclusive conditional passive discharge, thereby reducing system power consumption and eliminating residual voltage accumulation during long-term operation.

[0015] The charge balance control method and electrode charge balance circuit provided in this disclosure, through the synergistic cooperation among various technical features at the levels of topology, control timing and function allocation, can produce the following technical effects in solving technical problems such as energy waste, residual potential deviation and hardware resource redundancy caused by polarization charge accumulation at the electrode interface.

[0016] At the overall scheme level, this disclosure cross-multiplexes the energy storage inductor L and power switch group in the switching power converter (100), which originally only served the conversion between input voltage and supply voltage, with the full-bridge power switch group (S5~S8) and the recycling switches (S9, S12) to form an active energy recovery path. This allows the polarization energy of the electrode interface to be fed back to the input voltage end through two sub-stages: "inductor energy storage → inductor energy release", thereby realizing the recovery and reuse of interface polarization energy. At the same time, the residual charge monitoring circuit (300) samples the two ends of the electrode and compares them with a preset threshold to determine the subsequent charge balance path. When the deviation is greater than or equal to the threshold, it triggers the return to continue active recovery to form a closed loop iteration. When the deviation is less than the threshold, it allows the passive discharge switch S10 connected across the two ends of the electrode to be closed for passive discharge. During the operation of the active energy recovery path, the passive discharge switch S10 remains open and operates mutually exclusive with it. The tight coupling of the three reusable topologies, closed-loop threshold iteration, and active-passive mutual exclusion latches allows inductive recovery to first reduce the main part of the interface polarization voltage, thereby suppressing transient current during passive discharge. Meanwhile, the fallback effect of passive discharge allows inductive recovery to exit earlier with fewer iterations, thereby reducing switching losses. The two form a mutually dependent synergistic relationship, which is conducive to reducing the overall power consumption of the system while minimizing hardware resources, and also helps to control residual charge or residual polarization voltage within a preset safety range.

[0017] At the level of specific switching states and functional allocation, when this disclosure further defines the specific numbers and corresponding relationships of each switch (S5-S8) in the full-bridge power switch group, each switch (S1-S4) in the converter power switch group, the recovery switches (S9, S12), and the passive discharge switch S10, the active energy recovery path after positive stimulation is formed by S9, S7, S3 and the energy storage inductor L, and the active energy recovery path after reverse stimulation is formed by S12, S5, S3 and the energy storage inductor L. The two recovery paths share S3 and the energy storage inductor L and share S1 and S4 in the energy release stage to form a symmetrical structure. Thus, regardless of the direction of stimulation, the same set of core power paths can be reused to complete energy recovery, which is beneficial to simplifying the control logic and reducing the number of dedicated recovery switches.

[0018] At the level of the complete switching state sequence for positive stimulation, further defining the complete state machine for the positive stimulation phase (S7 and S6 are on), the inductor energy storage sub-phases (S9, S7, and S3 are on), the inductor energy release sub-phases (S1 and S4 are on), and the passive discharge phase (S10 is on) ensures a deterministic switching sequence between each working stage, which helps avoid power path conflicts caused by ambiguous switching states. Similarly, the symmetrical switching state sequence for reverse stimulation provides deterministic switching logic for each working stage after reverse stimulation, and the symmetrical structure of bidirectional recovery further demonstrates the compatibility of the same hardware resources with bidirectional stimulation.

[0019] At the symmetrical structure level of the forward and reverse recovery paths, when the two recovery paths share S3 and the energy storage inductor L, and the energy release stage shares S1 and S4, the symmetrical design ensures that the system does not need to configure independent recovery hardware for different stimulation directions, regardless of the direction of stimulation experienced by the electrodes, which is beneficial to improving the utilization rate of hardware resources.

[0020] At the level of redistributing the electrical function roles of power switches, when the third power switch S3 is further defined as participating in voltage conversion as a power switch on the output side of the converter during the power supply phase, and then redistributed as a return current path switch guiding the polarization current in reverse into the energy storage inductor L during the recycling phase, the same power switch is given distinctly different electrical function roles in different operating phases. This facilitates the system-level integration of the power supply converter and the recycling path without adding independent recycling switches. Similarly, when S7 is further defined as serving as the stimulation current path during positive stimulation and being redistributed as the recycling current path during positive recycling, and S5 as serving as the stimulation current path during reverse stimulation and being redistributed as the recycling current path during reverse recycling, the number of dedicated recycling switches required outside the full-bridge power switch group is further reduced.

[0021] At the stimulation mode switching level, by further limiting the conduction signal of the voltage stimulation switch S11 and the enable signal of the stimulation current source to be mutually exclusive and not simultaneously established at any time, the same hardware platform can be compatible with both constant current and constant voltage stimulation modes without changing the core power stage topology, which is beneficial for adapting to different electrode impedances and application protocols. Furthermore, the mutual exclusion configuration can prevent direct competition between the current source output and the direct output of the supply voltage, which is beneficial for maintaining the safety of the stimulation circuit during mode switching.

[0022] At the specific control level of passive discharge, when the closing of the passive discharge switch S10 is further limited to the single control of the comparison result—closing is only allowed when the residual charge deviation is less than the preset threshold, and closing is prohibited when the deviation is greater than or equal to the threshold—indiscriminate short-circuit discharge is avoided when the residual voltage at the interface is still high, which is beneficial to suppress transient current spikes and the resulting energy waste.

[0023] At the specific implementation level of residual charge monitoring, when the residual charge monitoring circuit is further limited to obtaining the residual charge deviation by differentially sampling the voltage across the electrode terminals, the sampling process can directly reflect the actual residual polarization state of the electrode interface.

[0024] At the converter topology selection level, when the switching power supply converter is further limited to a buck-boost converter, the energy storage inductor L performs three functions in a time-sharing manner during the power supply phase, the forward energy recovery phase, and the reverse energy recovery phase: voltage conversion and energy storage, forward polarization energy conversion, and reverse polarization energy conversion. During the active energy recovery process, the polarization energy at the electrode interface is first converted into the magnetic energy of the energy storage inductor L through the inductor energy storage sub-stage, and then fed back to the input voltage terminal through the inductor energy release sub-stage relying on the freewheeling characteristic of the energy storage inductor L. This energy feedback is achieved by the inductor freewheeling and does not depend on the polarization voltage. With input voltage The relationship between the magnitudes of the polarization voltage and the input voltage ensures that the system can maintain effective energy return capability regardless of whether the polarization voltage is higher, equal to, or lower than the input voltage, which is beneficial for expanding the system's adaptability to different electrode impedances and polarization voltage ranges.

[0025] At the device level, the electrode charge balancing circuit provided in this disclosure, through the coordinated cooperation of the above-mentioned components in terms of connection relationship and functional allocation, can produce technical effects corresponding to the steps of the aforementioned method. Specifically, the control output terminal of the residual charge monitoring circuit (300) is connected to the trigger terminal of the recovery circuit and the controlled terminal of the passive discharge switch, respectively. This bidirectional control architecture allows the residual charge monitoring circuit to switch between two paths, "continue active recovery" and "start passive discharge," based on the sampling results, forming a closed-loop control. The specific configuration of the passive discharge switch, which is connected across the two ends of the electrode and whose closure is triggered by the comparison result of the residual charge deviation and the threshold, ensures that passive discharge only occurs after the active recovery has reduced the interface residual voltage to a small range, thus suppressing transient current spikes. At the system level, the electrostimulation system provided in this disclosure, through the execution of closed-loop iterative active energy recovery and mutually exclusive conditional passive discharge, recovers and reuses interface polarization energy, which helps reduce system power consumption and control the accumulation of residual voltage during long-term operation within a preset safe range.

[0026] In summary, the aforementioned technical features do not produce their own effects independently, but rather work together in a tightly coupled framework of "triple reuse topology + closed-loop threshold iteration + active-passive mutual exclusion latch": triple reuse minimizes hardware resources, closed-loop iteration makes recycling accuracy controllable, and mutual exclusion latch makes the two power paths work in an orderly manner. Together, these three features achieve the technical effect of reducing system power consumption while controlling the residual charge deviation at the electrode interface within a preset safety range.

[0027] The specification of this application contains numerous technical features distributed across various technical solutions. Listing all possible combinations of these technical features (i.e., technical solutions) would make the specification excessively lengthy. To avoid this problem, the various technical features disclosed in the above-described invention, the various technical features disclosed in the following embodiments and examples, and the various technical features disclosed in the accompanying drawings can be freely combined to form various new technical solutions (all of which are considered to have been described in this specification), unless such a combination of technical features is technically infeasible. For example, one example discloses feature A+B+C, and another example discloses feature A+B+D+E. Features C and D are equivalent technical means that serve the same function, and technically only one needs to be used; they cannot be used simultaneously. Feature E can technically be combined with feature C. Therefore, the solution A+B+C+D should not be considered as described because it is technically infeasible, while the solution A+B+C+E should be considered as described. Attached Figure Description

[0028] Figure 1 This is an overall architecture block diagram of the electrode charge balance circuit according to an embodiment of this application.

[0029] Figure 2 This is a schematic diagram of a charge balance method after positive electrode stimulation according to an embodiment of the present application, wherein: (a) is a schematic diagram of the circuit state during the positive electrode stimulation stage; (b) is a schematic diagram of the circuit state during the inductive energy storage sub-stage of active energy recovery; (c) is a schematic diagram of the circuit state during the inductive energy release sub-stage of active energy recovery; and (d) is a schematic diagram of the circuit state during the passive discharge stage.

[0030] Figure 3 This is a schematic diagram of a charge balancing method after reverse electrode stimulation according to an embodiment of this application, wherein: (a) is a schematic diagram of the circuit state during the reverse electrode stimulation stage; (b) is a schematic diagram of the circuit state during the inductive energy storage sub-stage of active energy recovery; (c) is a schematic diagram of the circuit state during the inductive energy release sub-stage of active energy recovery; and (d) is a schematic diagram of the circuit state during the passive discharge stage.

[0031] Figure 4 This is a flowchart of a charge balance control method according to an embodiment of this application. Detailed Implementation

[0032] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0033] Explanation of some concepts: A switching power supply converter refers to a power conversion circuit that includes an energy storage inductor and a power switch group, and generates a controlled supply voltage based on the input voltage through the periodic on and off of the power switch and the energy storage and release function of the energy storage inductor. In this disclosure, a buck-boost converter topology or other topologies with energy storage inductors may be adopted.

[0034] An energy storage inductor is an inductive element used in the power stage of a switching power converter to store electrical energy in the form of a magnetic field during the power switch's on-time and release that electrical energy during the power switch's off-time. In this disclosure, the same energy storage inductor is time-division multiplexed between the power conversion phase and the active energy recovery phase.

[0035] A full-bridge power switch group refers to a full-bridge (H-bridge) circuit structure consisting of four power switches, used to selectively output stimulation signals to electrodes in a positive or negative direction. It includes the first bridge arm upper arm switch (S5), the first bridge arm lower arm switch (S6), the second bridge arm upper arm switch (S7), and the second bridge arm lower arm switch (S8).

[0036] Polarization charge refers to the net charge that accumulates at the interface between the electrode and the external load due to the electrochemical or capacitive effects during the output of stimulation signals by the electrode. This net charge forms a polarization voltage and stores polarization energy on the equivalent capacitance of the interface.

[0037] Polarization energy refers to the electrical energy stored in the equivalent capacitance of the interface between the electrode and the external load due to the accumulation of polarization charge. Its magnitude is related to the interface polarization voltage and the equivalent capacitance.

[0038] Active energy recovery refers to the process of transferring the polarization energy stored at the electrode interface back to the input voltage terminal via the magnetic energy of the energy storage inductor after the stimulation signal output ends, by controlling the power switch. It includes the inductor energy storage sub-stage and the inductor energy release sub-stage.

[0039] Passive discharge refers to the process of physically short-circuiting the two ends of the electrode by closing a passive discharge switch connected across the two ends of the electrode, thereby allowing the residual potential deviation at the electrode interface to dissipate naturally through the short circuit.

[0040] Residual charge deviation refers to the deviation amplitude of the polarization charge or residual polarization voltage that remains on the interface between the electrode and the external load after the active energy recovery step. It can be characterized by the absolute value of the residual polarization voltage or the absolute value of the residual charge obtained by equivalent capacitance.

[0041] Closed-loop iteration refers to the repeated cyclical process in which the residual charge monitoring circuit samples the two ends of the electrode and compares the residual charge deviation with a preset threshold. If the deviation is greater than or equal to the preset threshold, it triggers a return to continue executing the active energy recovery step and the residual charge monitoring step.

[0042] Mutually exclusive operation refers to a timing constraint relationship in which the passive discharge switch remains open during the operation of the active energy recovery path, and the two power paths cannot be in a conducting state at the same time.

[0043] The redistribution of electrical function roles refers to the change in the circuit function undertaken by the same power switch in different operating stages. For example, some switches in the full-bridge power switch group take on the stimulation current path in the stimulation step and the recovery current path in the active energy recovery step; another example is the third power switch (S3), which acts as the power switch on the output side of the converter in the power supply stage and as the return current path switch that guides the polarization current to enter the energy storage inductor in the recovery stage.

[0044] The following is a brief summary of some of the innovative aspects of this application: In summary, the technical solution of this application is not a simple series combination of known inductive energy recovery methods and known passive short-circuit discharge methods at the functional level. Its core lies in the fact that, when faced with the interrelated yet mutually restrictive technical contradiction of energy waste and residual potential deviation caused by polarization charge accumulation at the electrode and external load interface, the inventor creatively combined the energy storage inductor L and power switches S1 to S4, which were originally only used for input voltage to supply voltage conversion in the switching power converter (100), with the full-bridge power switch group (S5 to S8) and recovery switches S9 and S12 in a topological manner. Deep cross-coupling at the connection level allows the same energy storage inductor L to perform voltage conversion and energy storage functions during the stimulation phase, while being reused as a magnetic transfer carrier for polarization energy during the active recovery phase after stimulation. Simultaneously, some switches in the full-bridge power switch group that originally only served as stimulation current paths (S7 in forward recovery and S5 in reverse recovery) and the converter output power switch S3 are reassigned distinct electrical functional roles during the recovery phase, transforming into components of the return current path that guides the polarization current from the electrodes back into the energy storage inductor L via the recovery path. This redistribution of functional roles, rather than simple switch multiplexing, allows the forward recovery path (S9—S7—S3—L) and the reverse recovery path (S12—S5—S3—L) to form a symmetrical structure sharing S3 and the energy storage inductor L. Furthermore, during the inductor energy release phase, they share S1 and S4 to return magnetic energy to the input voltage terminal, thus achieving deep system-level integration of the power supply converter and the recovery path without the need for a separate recovery inductor. Furthermore, this application introduces a closed-loop iterative control driven by a residual charge monitoring circuit (300) and an active-passive mutual exclusion timing constraint on the basis of the above triple reusable topology: when the residual charge deviation is greater than or equal to a preset threshold, it triggers a return to continue active recycling; the passive discharge switch S10 is only allowed to close when the deviation drops below the threshold; and during the entire active energy recovery path, the passive discharge switch S10 remains open and operates mutually exclusive with the active recycling path. The above triple reusable topology, closed-loop threshold iteration, and active-passive mutual exclusion latch form an inseparable tight coupling dependency: inductive recycling first lowers the main part of the interface polarization voltage, so that the transient current spike when the passive discharge switch S10 is closed is suppressed; and the backstop effect of passive discharge, in turn, allows inductive recycling to exit the closed-loop iteration earlier with a more relaxed precision and reduce unnecessary switching losses—the two are interdependent rather than independent. If the active recycling path is not constructed through the aforementioned specific triple reuse topology, the passive discharge will have to short-circuit when the residual pressure at the interface is still high. The resulting energy waste and local temperature rise are precisely the core technical problems that this application aims to solve. If closed-loop threshold judgment and mutual exclusion latch are not introduced, the triggering time of the passive discharge will lack a basis, which may destroy the integrity of the active recycling process.Therefore, the overall technical effect produced by the synergistic combination of the above technical features—while minimizing hardware resources, simultaneously taking into account the orderly recovery and reuse of interface polarization energy and the controllable elimination of residual charge—is not a simple addition of the effects of each component, but rather stems from the organic unity of the three at the topology, timing, and control logic levels.

[0045] Furthermore, through long-term and in-depth research on the charge balance control problem in electrode electrical stimulation systems, the inventors of this application have discovered that the technical dilemma faced by existing technologies in this field is not merely a single issue of "whether residual charge can be eliminated," but rather a systemic problem in which four dimensions of technical contradictions—"energy recovery efficiency," "residual charge elimination accuracy," "hardware resource overhead," and "timing safety between power paths"—are intertwined and mutually restrictive.

[0046] After conducting an in-depth analysis of existing inductor-based energy recovery schemes, the inventors discovered that in these schemes, the power converter and the energy recovery path are usually constructed independently at the circuit topology level. That is, the power converter has its own energy storage inductor and power switch group, while the energy recovery path has a separate recovery inductor or dedicated recovery switch. Although this discrete architecture is functionally feasible, it leads to the duplication of hardware resources. More importantly, the inventors realized that in this kind of discrete architecture, even if inductive energy recovery is introduced, due to the objective existence of non-ideal factors such as the on-resistance of the power switch, the DC resistance of the inductor, and the switching loss, active recovery has an inherent limit in terms of accuracy, and will always leave a certain amount of residual polarization charge deviation at the electrode interface. After further analysis, the inventors discovered that if they tried to bring the residual deviation close to zero by simply increasing the number of iterations of inductive recycling, the marginal recycling amount brought by each iteration would decrease, while the proportion of switching losses in the total energy consumption would increase. This would eventually lead to a dilemma between "recycling accuracy" and "recycling power consumption" in the system, which is precisely one of the fundamental contradictions that existing technologies have failed to systematically solve.

[0047] Through in-depth observation of the actual working state of the passive short-circuit discharge scheme, the inventors discovered that when the short-circuit switch is directly closed under conditions of large residual polarization voltage, the unrecovered polarization energy is instantaneously released across the electrode internal resistance. The resulting large transient current spike and the resulting local temperature rise and electrochemical shock are precisely the inherent technical defects of this method in the absence of pre-active energy recovery. However, if a passive short-circuit switch is simply added in series after the inductive energy recovery scheme without designing mutual exclusion timing constraints and closed-loop triggering mechanisms between the active recovery path and the passive short-circuit branch at the hardware level, the accidental conduction of the passive short-circuit branch before the active recovery is completed will disrupt the integrity of the energy recovery process, and may even lead to two power paths conducting simultaneously, causing more serious circuit safety problems. Based on the above in-depth research, the inventors of this application propose a technical solution that deeply reuses the energy storage inductor and power switch group of the switching power converter with the full-bridge power switch group and the recovery switch at the system level, and achieves orderly energy recovery and controllable charge elimination through closed-loop threshold iteration and active-passive mutual exclusion latching. The implementation process of this disclosure will be described in detail below through specific embodiments.

[0048] The technical solutions in the embodiments of this disclosure will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0049] It should be noted that, in the description of this disclosure, "electrode" refers to a component used for coupling with an external load to output a stimulation signal, and "external load" encompasses the electrical interface formed between the electrode and the object it contacts, as well as its equivalent impedance. The following embodiments use the electrode-tissue interface formed by the electrode in contact with biological tissue as a typical external load for illustration, but the charge balance control method and circuit architecture of this disclosure are not limited to this specific application scenario. Furthermore, the power switches described in the embodiments of this disclosure can be implemented using MOSFETs, IGBTs, or other suitable semiconductor power devices, and this disclosure does not limit their implementation.

[0050] I. Overall Architecture of Electrode Charge Balance Circuit Please see Figure 1The overall architecture of the electrode charge balancing circuit provided in this embodiment includes: a switching power converter 100, an electrode stimulation module 200, a residual charge monitoring circuit 300, an electrode energy recovery module 400, a passive discharge switch 500, and a current / voltage stimulation selection module 600. When the electrode is coupled to an external load (e.g., biological tissue 700), the above modules work together to achieve the recovery and reuse of interface polarization energy and the controllable elimination of residual charge while completing the electrode stimulation signal output.

[0051] Specifically, the power input terminal of the switching power converter 100 is electrically connected to an external power source, and its power output terminal is connected to the system power supply axis. It is used to generate a controlled supply voltage based on the input voltage and to provide a drive level for the electrode stimulation module 200. In this embodiment, the switching power converter 100 adopts a buck-boost topology. Its power stages include a first power switch S1, a second power switch S2, a third power switch S3, a fourth power switch S4, an energy storage inductor L, and corresponding input and output capacitors. The input capacitor is connected between the external power source and the reference ground for filtering and voltage regulation, while the output capacitor is connected between the supply voltage axis and the reference ground to maintain the stability of the supply voltage. The control loop inside the converter adjusts the conduction sequence of power switches S1 to S4 according to the feedback signal to output the required supply voltage amplitude. The technical significance of using a buck-boost topology is that, during the power supply phase, this topology allows the supply voltage to be either higher or lower than the input voltage to adapt to different electrode impedances and stimulation intensity requirements. During the active energy recovery phase, the polarization energy at the electrode interface is first converted into the magnetic energy of the energy storage inductor L via the inductor energy storage sub-stage, and then fed back to the input voltage terminal via the inductor energy release sub-stage relying on the freewheeling characteristic of the energy storage inductor L. This energy recovery process is achieved by the inductor freewheeling and does not depend on the polarization voltage at the electrode interface. With input voltage The magnitude relationship between the polarization voltage and the input voltage allows for the return of polarization energy to the input voltage terminal regardless of whether the polarization voltage is higher, equal to, or lower than the input voltage. This gives the system broad adaptability to different electrode impedances and different polarization voltage ranges, rather than being limited to energy conversion in only one direction. It should be noted that in other alternative embodiments, the switching power supply converter 100 can also adopt other topologies with energy storage inductors, such as a Ćuk converter or a SEPIC converter, as long as the converter can achieve forward conversion from the input voltage to the supply voltage and reverse return of polarization energy from the electrode side to the input voltage terminal.

[0052] The control output of the current / voltage stimulation selection module 600 is connected to the selection input of the electrode stimulation module 200 to switch between constant current stimulation mode and constant voltage stimulation mode. The load output of the electrode stimulation module 200 is connected to an external load via electrodes to form a stimulation circuit.

[0053] The sampling input terminal of the residual charge monitoring circuit 300 is electrically connected to both ends of the electrode, and is used to sample the residual charge state of the electrode interface in real time after stimulation. The control output terminal of the residual charge monitoring circuit 300 is a bidirectional control output, connected to the trigger terminal of the electrode energy recovery module 400 and the controlled terminal of the passive discharge switch 500, respectively. This bidirectional control architecture allows the residual charge monitoring circuit 300 to switch between two paths, "continue active recovery" and "start passive discharge", based on the sampling results. In an optional implementation, the residual charge monitoring circuit 300 includes a differential sampling circuit and a comparison circuit. The differential sampling circuit differentially samples the voltage across the electrode to obtain a residual polarization voltage signal. The comparison circuit compares the residual polarization voltage signal with a preset threshold to generate a comparison result, which is then output to the trigger terminal of the recovery circuit 400 or the controlled terminal of the passive discharge switch 500 via the control output terminal.

[0054] The power feedback terminal of the electrode energy recovery module 400 is connected to the auxiliary energy storage node of the switching power converter 100, allowing the polarization energy at the electrode interface to be pumped back to the input voltage terminal (e.g., a lithium battery or energy storage capacitor) through the recovery circuit and the multiplexed energy storage inductor path. In this embodiment, the electrode energy recovery module 400 includes a first recovery switch S9 and a second recovery switch S12. One end of the first recovery switch S9 is connected to one side of the electrode, and the other end is connected to the energy storage inductor L; one end of the second recovery switch S12 is connected to the other side of the electrode, and the other end is also connected to the power path where the energy storage inductor L is located.

[0055] The passive discharge switch 500 is connected across the load output terminals of the electrode stimulation module 200, that is, physically connected between the two terminals of the electrode. In this embodiment, the passive discharge switch 500 is switch S10. The passive discharge switch S10 is used to perform controlled conduction after the active energy recovery is completed, reducing the residual potential deviation to within a preset safe range by physically shorting the two terminals of the electrode.

[0056] II. Detailed Circuit Structure of the Electrode Stimulation Module Please continue reading. Figure 2 and Figure 3The circuit topology shown integrates a full-bridge power switch group, a stimulation current source, and a voltage stimulation switch S11 within the electrode stimulation module 200. The full-bridge power switch group (also known as an H-bridge or full-bridge power switch group) comprises four power switches: the upper arm switch S5 of the first bridge arm, the lower arm switch S6 of the first bridge arm, the upper arm switch S7 of the second bridge arm, and the lower arm switch S8 of the second bridge arm. The input terminal of the full-bridge power switch group is connected to the power output terminal (i.e., the supply voltage axis) of the switching power converter 100, and its output terminal is connected to the two terminals of the electrode, selectively outputting stimulation signals to the electrode to achieve bidirectional (positive and negative) stimulation. Specifically, during positive stimulation, the upper arm switch S7 of the second bridge arm and the lower arm switch S6 of the first bridge arm form a diagonal conducting pair; during negative stimulation, the upper arm switch S5 of the first bridge arm and the lower arm switch S8 of the second bridge arm form another diagonal conducting pair, with the current direction reversed.

[0057] A stimulation current source is connected in series between the full-bridge power switch group and the reference ground to provide a controlled, constant stimulation current in current stimulation mode. A voltage stimulation switch S11 is connected in parallel with the stimulation current source. Specifically, the on signal of the voltage stimulation switch S11 and the enable signal of the stimulation current source are configured to be mutually exclusive: at any given time, the on state of the voltage stimulation switch S11 and the enable state of the stimulation current source cannot be simultaneously established. The technical significance of this mutually exclusive configuration is to prevent shoot-through competition between the current source output and the direct output of the supply voltage, avoiding uncontrolled large current surges caused by the simultaneous application of two power sources to the load circuit, thereby contributing to the safety and determinism of the stimulation circuit during maintenance mode switching.

[0058] When the current / voltage stimulation selection module 600 selects the current stimulation mode, the voltage stimulation switch S11 is turned off, and the stimulation current source is enabled. Through the coordinated action of the stimulation current source and the full-bridge power switch group, a bidirectional current pulse with a preset pulse width and intensity is generated and applied to the electrodes. When the current / voltage stimulation selection module 600 selects the voltage stimulation mode, the stimulation current source is turned off, and the voltage stimulation switch S11 is turned on. At this time, the controlled supply voltage output by the switching power converter 100 directly provides constant voltage stimulation to the electrodes through the full-bridge power switch group. In this way, the same hardware platform can be compatible with both constant current and constant voltage stimulation modes without changing the core power stage topology, adapting to different electrode impedances and application protocol requirements.

[0059] III. System-level Deep Reuse of Energy Storage Inductors and Power Switches One of the core technical features of this embodiment is that the energy storage inductor L and power switch group in the switching power converter 100 do not only serve a single voltage conversion function, but are deeply reused at the system level throughout the entire working cycle to undertake three different functional roles.

[0060] Furthermore, in the stimulation step, the energy storage inductor L undertakes the core voltage conversion and energy storage function of the switching power converter, that is, it participates in the energy conversion process of converting the input voltage into the supply voltage. In the active energy recovery step, the same energy storage inductor L is reused as the conversion medium for polarization energy, first converting the capacitive polarization energy at the electrode interface into the magnetic energy of the inductor (inductor energy storage sub-stage), and then feeding this magnetic energy back to the input voltage terminal (inductor energy release sub-stage). Furthermore, some switches in the full-bridge power switch group (specifically, the upper arm switch S7 of the second bridge arm in forward recovery and the upper arm switch S5 of the first bridge arm in reverse recovery) function as the stimulation current path in the stimulation step, while in the active energy recovery step, their electrical functional roles are redistributed, transforming them into components of the recovery current path. This means that the aforementioned switches are given completely different electrical functional positions in different operating stages; it is a redistribution of functional roles rather than a simple switch multiplexing.

[0061] More specifically, the role redistribution of the third power switch S3 in the switching power converter 100 is particularly typical: In the power supply phase corresponding to the stimulation step, the third power switch S3, as one of the output-side power switches of the switching power converter, participates in the conversion process of the input voltage to the supply voltage. Under the command of the converter control loop, it periodically turns on and off, cooperating with the energy storage inductor L and other power switches to complete the voltage conversion and energy storage function. In the inductor energy storage sub-phase of the active energy recovery step, the third power switch S3 is redistributed as the return current path switch that guides the polarization current flowing out of the full-bridge power switch group back into the energy storage inductor L. At this time, the current direction, operating timing, and circuit function performed by S3 are completely different from those in the power supply phase. This role redistribution eliminates the need for a separate energy recovery inductor, achieving system-level deep integration of the power converter and the recovery path while minimizing hardware resources.

[0062] Please see Figure 2 (b) and Figure 3 (b) The active energy recovery path after positive stimulation is formed by the first recovery switch S9, the upper arm switch of the second bridge arm S7, the third power switch S3, and the energy storage inductor L; the active energy recovery path after reverse stimulation is formed by the second recovery switch S12, the upper arm switch of the first bridge arm S5, the third power switch S3, and the energy storage inductor L. The two recovery paths share the third power switch S3 and the energy storage inductor L, forming a symmetrical structure. During the inductor energy release stage, they share the first power switch S1 and the fourth power switch S4 to return the magnetic energy to the input voltage terminal. This symmetrical design allows the same core power path to be reused to complete energy recovery regardless of the stimulation direction, and the symmetry simplifies the design of the control logic.

[0063] The above triple reuse relationship can be understood from the perspective of energy conversion. In the stimulation step, the current flowing through the energy storage inductor L carries electrical energy transferred from the input voltage terminal to the supply voltage terminal; while in the recovery step, the direction of the current flowing through the energy storage inductor L and the source of the energy it carries both change—the current comes from the release of polarization charges at the electrode interface, and the energy is ultimately returned to the energy storage element (such as a lithium battery or input capacitor) at the input voltage terminal. From the perspective of the electrode interface, this process is essentially the process of converting the polarization energy accumulated on the equivalent capacitance of the electrode-tissue interface into energy. First, the magnetic energy is converted into that of an inductor. The energy is then pumped back to the input terminal via an inductor discharge stage. The polarization energy stored at the electrode interface can be expressed as: in, This represents the equivalent capacitance at the interface between the electrode and the external load. This represents the interface polarization voltage. After the inductor energy storage sub-stage is completed, the magnetic energy stored in the inductor can be expressed as: in, The inductance of the energy storage inductor. This represents the inductor current at the end of the inductor energy storage sub-stage. It also represents the energy actually returned to the input voltage terminal after the inductor energy release sub-stage ends. With the original polarization energy The ratio is the recovery efficiency: The recovery efficiency is affected by factors such as the on-resistance of the power switch, the DC resistance of the inductor, and switching losses, making it difficult to achieve an ideal value in actual circuits. Because active inductive recovery has accuracy limitations, this embodiment introduces conditional passive discharge as a backup measure after active recovery; the two are functionally interdependent rather than simply parallel.

[0064] IV. Specific Workflow of Charge Balance Control Method Please see Figure 4 The complete workflow of the charge balance control method provided in this disclosure is as follows. In each stimulation cycle, the method sequentially undergoes a stimulation step, an active energy recovery step, a residual charge monitoring step, and a closed-loop iteration and conditional passive discharge step.

[0065] Step 100: Stimulation Step During the stimulation step, the switching power converter 100 generates a supply voltage based on the input voltage via the energy storage inductor L and outputs it to the full-bridge power switch group. The system enters the corresponding operating mode according to the instructions of the current / voltage stimulation selection module 600.

[0066] Step 110: Current Stimulation Mode. Turn off the voltage stimulation switch S11 and enable the stimulation current source. The stimulation current source, in conjunction with the full-bridge power switch group, outputs a current stimulation signal to the electrodes. In this mode, the stimulation current source provides a controlled constant current, the current amplitude and pulse width of which are determined by the system according to a preset stimulation protocol.

[0067] Step 120: Voltage Stimulation Mode. Turn off the stimulation current source and turn on the voltage stimulation switch S11. The supply voltage output from the switching power converter 100 is directly applied to the electrodes via the full-bridge power switch assembly to output a voltage stimulation signal. In this mode, the stimulation voltage across the electrodes is determined by the supply voltage.

[0068] It should be noted that in steps 110 and 120, the on state of the voltage stimulation switch S11 and the enabled state of the stimulation current source are not simultaneously established at any time, so as to maintain the hardware-level mutual exclusion between the two stimulation modes.

[0069] Step 130: Positive Stimulation Pattern. See also... Figure 2 (a) In the positive stimulation mode, the upper arm switch S7 of the second bridge arm and the lower arm switch S6 of the first bridge arm are turned on, while the remaining full-bridge power switches (S5, S8) are turned off. The first recovery switch S9, the second recovery switch S12, and the passive discharge switch S10 are all kept off. If the current / voltage stimulation selection module 600 selects voltage stimulation, the voltage stimulation switch S11 is turned on simultaneously, and the stimulation current source is turned off; if current stimulation is selected, the voltage stimulation switch S11 is turned off, and the stimulation current source is enabled. The current flows from the supply voltage axis, through the upper arm switch S7 of the second bridge arm to one end of the electrode, passes through the external load, and flows back from the other end of the electrode, then through the lower arm switch S6 of the first bridge arm to the reference ground, completing the positive stimulation signal output. During this process, polarization charge accumulates and polarization energy is stored at the interface between the electrode and the external load.

[0070] Step 140: Reverse Stimulation Mode. See also... Figure 3 (a) In the reverse stimulation mode, the upper arm switch S5 of the first bridge arm and the lower arm switch S8 of the second bridge arm are turned on, while the remaining full-bridge power switches (S6, S7) are turned off. The first recovery switch S9, the second recovery switch S12, and the passive discharge switch S10 are all kept off, and the stimulation current source or voltage stimulation switch S11 is controlled accordingly based on the stimulation mode. The current starts from the supply voltage axis, flows through the upper arm switch S5 of the first bridge arm to one end of the electrode, passes through the external load to form a stimulation current in the opposite direction to the forward stimulation, and then flows from the other end of the electrode through the lower arm switch S8 of the second bridge arm to the reference ground. At this time, the interface between the electrode and the external load also accumulates polarization charge and stores polarization energy, but the polarity is opposite to that of the forward stimulation.

[0071] It should be noted that the choice between positive and negative stimuli depends on the specific application protocol requirements. In a complete stimulation sequence, only one type of stimulation can be performed, or positive and negative stimuli can be performed alternately. Regardless of the stimulation direction chosen, the subsequent active energy recovery and passive discharge steps can be adapted and executed.

[0072] Step 200: Active Energy Recovery Steps After the stimulation signal output ends, the system automatically enters the active energy recovery step. During the entire active energy recovery step, the passive discharge switch S10 remains open, operating mutually exclusively with the active energy recovery path. This mutual exclusion timing constraint is an important technical feature of this embodiment: if the passive discharge switch S10 is directly closed for short-circuit discharge when there is still a large residual polarization voltage at the electrode interface, the unrecovered polarization energy will be released as heat dissipation on the electrode internal resistance, generating a large transient current spike and local temperature rise; however, by actively inductively recovering the main part of the interface polarization energy and sending it back to the input end, the transient current during subsequent passive discharge is significantly suppressed, thereby achieving orderly recovery of electrode energy and controllable elimination of residual charge.

[0073] The active energy recovery process comprises two sub-stages: an inductive energy storage sub-stage and an inductive energy release sub-stage. The specific switching actions of these two sub-stages differ depending on the direction of the stimulus, but they form a symmetrical structure.

[0074] Step 210: Inductor energy storage sub-stage after positive stimulation. Referring to Figure 2(b), after the positive stimulation ends, switches S6 and S11 (or the stimulation current source) in the stimulation circuit are turned off. The first recovery switch S9 is turned on, the second bridge arm upper switch S7 remains on, and the third power switch S3 is turned on. The passive discharge switch S10 remains off. At this time, the polarization voltage stored at the electrode interface serves as energy, driving the polarization current to flow out from the positive terminal of the electrode. This current flows sequentially through the second bridge arm upper switch S7 and the third power switch S3 into the energy storage inductor L, and then flows back to the negative terminal of the electrode through the first recovery switch S9, forming a recovery current loop. This process converts the capacitive charge energy on the equivalent capacitance of the electrode interface into magnetic energy in the energy storage inductor L. In this sub-stage, the electrical function of the second bridge arm upper arm switch S7 is reassigned from "positive stimulation current path" in the stimulation step to "component of positive recovery current path," and the electrical function of the third power switch S3 is reassigned from "converter output side power switch" in the power supply stage to "reverse flow path switch that guides polarization current into the energy storage inductor." The function of the first recovery switch S9 is to close the recovery current loop between the energy storage inductor and the electrode in the recovery stage. The above switches and the energy storage inductor L together form a positive active energy recovery path.

[0075] Step 220: The inductive discharge phase following positive stimulation. (See also...) Figure 2 (c) After the inductor has completed energy storage, switches S7, S3, and S9 are turned off, and the first power switch S1 and the fourth power switch S4 are turned on. The energy storage inductor L sends (pumps back) the stored magnetic energy to the energy storage element at the input voltage terminal via the first power switch S1. This process realizes the recovery and reuse of residual energy at the interface.

[0076] Step 230: Inductor Energy Storage Sub-stage after Reverse Stimulation. Referring to Figure 3(b), after the reverse stimulation ends, the switches in the stimulation circuit are turned off, controlling the conduction of the first bridge arm upper arm switch S5, the third power switch S3, and the second recovery switch S12, while the passive discharge switch S10 remains open. Using the interface potential generated by reverse polarization as energy, the polarization current flows through the first bridge arm upper arm switch S5 and the third power switch S3 into the energy storage inductor L, and then flows back to the other polarity end of the electrode through the second recovery switch S12, effectively converting the reverse-accumulated interface polarization energy into the magnetic energy of the energy storage inductor. In this sub-stage, the electrical function of the first bridge arm upper arm switch S5 is reassigned from "reverse stimulation current path" in the stimulation step to "component of the reverse recovery current path," forming a reverse active energy recovery path.

[0077] Step 240: Inductive discharge phase following reverse stimulation. (See also...) Figure 3 (c) When the inductor has finished storing energy, the first power switch S1 is kept on and the fourth power switch S4 is turned on. The energy storage inductor L sends the stored magnetic energy back to the input voltage terminal through the first power switch S1.

[0078] As can be seen from steps 210 to 240 above, the active energy recovery path after positive stimulation is formed by the first recovery switch S9, the second bridge arm upper arm switch S7, the third power switch S3, and the energy storage inductor L; the active energy recovery path after reverse stimulation is formed by the second recovery switch S12, the first bridge arm upper arm switch S5, the third power switch S3, and the energy storage inductor L. These two recovery paths constitute a symmetrical structure, sharing the third power switch S3 and the energy storage inductor L, and in the inductor energy release stage, the magnetic energy is returned to the input voltage terminal via the first power switch S1 and the fourth power switch S4. This symmetrical design allows the same core power path to be reused to complete energy recovery regardless of the stimulation direction, further demonstrating the advantages of system-level hardware reuse.

[0079] Step 300: Residual Charge Monitoring Step After the active energy recovery step is completed, the residual charge monitoring circuit 300 samples the two ends of the electrode to obtain the residual charge deviation after the active energy recovery step. In this embodiment, the residual charge monitoring circuit 300 obtains the residual polarization voltage signal by differentially sampling the voltage across the two ends of the electrode, and compares the residual polarization voltage signal (or the residual charge amount converted from it) with a preset threshold to generate a comparison result. The preset threshold corresponds to the upper limit of the residual charge deviation when the electrode interface is in a safe state.

[0080] Step 400: Closed-loop iteration and conditional passive release steps This step uses the comparison results generated in step 300 to determine the subsequent charge balance path, thus forming a closed-loop control.

[0081] Step 410: If the comparison result indicates that the residual charge deviation is greater than or equal to the preset threshold, it means that a considerable amount of polarization charge remains at the electrode interface after one active energy recovery. At this time, the system triggers a return to execute steps 200 (active energy recovery step) and 300 (residual charge monitoring step) based on the comparison result, forming a closed-loop iteration. This closed-loop iteration mechanism ensures that active recovery is not only executed once, but can be repeatedly executed according to the actual state of the residual charge until the residual charge deviation is reduced to below the preset threshold. Compared with the open-loop "sampling-comparison-single trigger" mode, closed-loop iteration can more effectively utilize the energy advantage of inductive recovery and maintain high recovery accuracy under conditions such as device mismatch or load changes.

[0082] Step 420: If the comparison result indicates that the residual charge deviation is less than the preset threshold, it means that the active inductive recovery has reduced the interface polarization voltage to a smaller range. At this point, the marginal benefit of continuing inductive recovery decreases, while the proportion of switching losses increases. Under this condition, the passive discharge switch S10 is closed to physically short-circuit the two ends of the electrode for passive discharge, eliminating the last residual potential deviation at the electrode interface. The closing of the passive discharge switch S10 is solely controlled by the comparison result—the passive discharge switch S10 is only allowed to close when the comparison result of the residual charge monitoring circuit 300 indicates that the residual charge deviation is less than the preset threshold; when the comparison result indicates that the residual charge deviation is greater than or equal to the preset threshold, the passive discharge switch S10 is prohibited from closing. Since the interface residual voltage has been actively reduced to a smaller level at this time, the transient current spike when S10 closes is effectively suppressed.

[0083] Step 430: After passive discharge is completed, the residual charge deviation at the electrode interface is reduced to within the preset safe range. The passive discharge switch S10 is disconnected, the current stimulation cycle ends, and preparations are made to enter the next working cycle.

[0084] V. The complete charge balance process after positive stimulation Please see Figure 2 The following description, using positive stimulation as an example and combining specific switching states, describes the stages of the charge balance process in a complete stimulation cycle.

[0085] like Figure 2 As shown in (a), during the positive electrode stimulation phase, the switching power converter 100 has converted the input voltage into the supply voltage. The system determines the stimulation mode according to the instructions of the current / voltage stimulation selection module 600. If it is voltage stimulation, the voltage stimulation switch S11 is turned on and the stimulation current source is turned off; if it is current stimulation, S11 is turned off and the stimulation current source is enabled. Subsequently, the upper arm switch S7 of the second bridge arm and the lower arm switch S6 of the first bridge arm are turned on, and the remaining full-bridge switches (S5, S8) are turned off. The first recovery switch S9, the second recovery switch S12, and the passive discharge switch S10 are all kept off. The current starts from the supply voltage terminal, flows through S7 to the anode of the electrode, passes through the external load, and flows through S6 to the reference ground, completing the positive stimulation signal output. At this time, polarization charge accumulates and polarization energy is stored at the interface between the electrode and the external load.

[0086] like Figure 2 As shown in (b), after stimulation, the active energy recovery inductor energy storage sub-stage begins. At this time, S6 and S11 (or the stimulation current source) in the stimulation circuit are turned off, the first recovery switch S9 is turned on, the second bridge arm upper switch S7 remains on, and the third power switch S3 is turned on. The passive discharge switch S10 remains off. Using the polarization voltage stored at the electrode interface as a driving source, the polarization current flows out from the positive terminal of the electrode, sequentially through the second bridge arm upper switch S7 and the third power switch S3 into the energy storage inductor L, and then flows back to the negative terminal of the electrode through the first recovery switch S9, converting the polarization energy into the magnetic energy of the energy storage inductor L. In this stage, S7 changes from a stimulation current path to a recovery current path, and S3 changes from a power switch on the converter output side to a return current path switch.

[0087] like Figure 2 As shown in (c), after the inductor completes energy storage, it enters the inductor energy release stage. At this time, the first power switch S1 and the fourth power switch S4 are turned on, while S7, S3, and S9 are turned off. The magnetic energy stored in the energy storage inductor L is pumped back to the input voltage terminal via the S1 path, realizing the recovery and reuse of residual energy at the interface.

[0088] After completing one cycle of "inductor energy storage → inductor energy release", the residual charge monitoring circuit 300 samples the two ends of the electrode. If the residual charge deviation is still greater than or equal to the preset threshold, the system returns to execute the inductor energy storage sub-stage and the inductor energy release sub-stage, forming a closed-loop iteration. If the residual charge deviation has dropped below the preset threshold, the system enters the passive discharge stage.

[0089] like Figure 2As shown in (d), during the passive discharge phase, the passive discharge switch S10 is closed in a controlled manner. At this time, the two ends of the electrode are physically short-circuited, forcing the last trace residual potential deviation at the electrode interface to dissipate naturally through the short-circuit path. After the residual charge or residual polarization voltage is reduced to within the preset safe range, S10 is disconnected, and the current stimulation cycle ends.

[0090] VI. The complete charge balance process after reverse stimulation Please see Figure 3 The following description of the complete charge balance process uses reverse stimulation as an example.

[0091] like Figure 3 As shown in (a), during the reverse electrode stimulation phase, the upper arm switch S5 of the first bridge arm and the lower arm switch S8 of the second bridge arm are turned on, while the remaining full-bridge switches (S6, S7) are turned off. The first recovery switch S9, the second recovery switch S12, and the passive discharge switch S10 are all kept off. Current flows from the supply voltage terminal through S5 to one end of the electrode, passes through the external load to form a reverse stimulation current, and then flows back from the other end of the electrode, through S8 to the reference ground, completing the reverse stimulation signal output. At this time, polarization charges in opposite directions accumulate at the interface between the electrode and the external load.

[0092] As shown in Figure 3(b), after the reverse stimulation ends, the active energy recovery inductive energy storage sub-stage begins. At this time, the relevant switches in the stimulation circuit are turned off, while the upper arm switch S5 of the first bridge arm, the third power switch S3, and the second recovery switch S12 are turned on. The passive discharge switch S10 remains open. The interface potential generated by reverse polarization drives the polarization current through S5 and S3 into the energy storage inductor L, and then flows back to the other end of the electrode through the second recovery switch S12, converting the reverse-accumulated interface polarization energy into inductive magnetic energy. In this stage, S5 transitions from a reverse stimulation current path to a reverse recovery current path.

[0093] It is important to note the symmetry of the forward and reverse energy recovery paths: the forward energy recovery path is formed by S9, S7, S3 and the energy storage inductor L; the reverse energy recovery path is formed by S12, S5, S3 and the energy storage inductor L. Both paths share the third power switch S3 and the energy storage inductor L, forming a symmetrical structure. This symmetrical design allows the system to recover energy using the same set of energy storage inductors and shared power switches, regardless of whether the electrodes experience forward or reverse stimulation, eliminating the need for separate energy recovery hardware for different stimulation directions.

[0094] like Figure 3As shown in (c), after the inductor completes energy storage, it enters the inductor energy release sub-stage. The first power switch S1 and the fourth power switch S4 are turned on, and the energy storage inductor L pumps the stored energy back to the input voltage terminal via path S1. This energy release path is exactly the same as the forward recovery path, demonstrating path multiplexing in the energy release stage.

[0095] Subsequently, the residual charge monitoring circuit 300 samples and makes a judgment. For example... Figure 3 As shown in (d), if the residual charge deviation has decreased to below the preset threshold, the passive discharge switch S10 is closed under control, and the two ends of the electrode are physically shorted to eliminate the last residual potential deviation. Otherwise, the process returns to continue iteratively executing active recycling.

[0096] VII. Synergistic Relationship between Active Energy Recovery and Passive Energy Dissipation It should be further explained that, in this embodiment, active energy recovery and conditional passive energy release are not independent and parallel functions, but rather have a synergistic relationship of mutual dependence.

[0097] From one perspective, inductive energy recovery first returns most of the polarization energy at the electrode interface to the input terminal through inductive energy storage and release, significantly reducing the residual polarization voltage at the interface before passive discharge is initiated. This means that when the passive discharge switch S10 closes for short-circuit discharge, the potential difference across the electrode is already small, resulting in a significantly suppressed transient short-circuit current compared to the current value when short-circuit discharge occurs immediately after stimulation. The suppression of current spikes directly reduces the thermal stress and electrochemical shock on the electrode and interface.

[0098] From another perspective, the existence of passive discharge as a fallback mechanism allows inductive recycling to exit the closed-loop iteration earlier with more lenient accuracy requirements. If the system requires inductive recycling to completely eliminate residual charge to zero, extremely high recycling accuracy and a large number of iterations are needed, with each iteration incurring switching losses. With the introduction of passive discharge as a fallback, inductive recycling only needs to reduce the residual charge below a preset threshold to exit, and the remaining minute deviation is cleared by passive discharge with extremely low power consumption and current, thereby reducing unnecessary iterations and corresponding switching energy losses.

[0099] The overall effect of the two working together is that, without increasing additional hardware overhead, the system not only achieves the recovery and reuse of most of the polarization energy to reduce overall power consumption, but also helps to control the residual charge at the electrode interface within a preset safe range to maintain long-term operational safety.

[0100] 8. Comparison of Active-Passive Mutually Exclusive Operation and Indiscriminate Short Circuit This embodiment emphasizes that the passive discharge switch S10 remains open throughout the active energy recovery path, with the two operating mutually exclusively. The necessity of this timing constraint can be understood from the following perspective: if no mutual exclusion constraint is set, and the passive discharge switch S10 is closed before active recovery is complete, the short-circuit path at both ends of the electrode will exist simultaneously with the active recovery path. The polarization current will be diverted to the passive discharge branch instead of being converted through the energy storage inductor, resulting in energy not being effectively recovered and being dissipated as heat. Furthermore, if active recovery is not performed at all, and the passive discharge switch S10 is closed directly after stimulation for indiscriminate short-circuiting, all the polarization energy at the electrode interface will be converted into heat dissipation through the electrode's internal resistance at the moment of short-circuiting, not only wasting energy but also causing local temperature rise and current surge. Therefore, the combination of active-passive mutual exclusion timing and conditional triggering mechanism is a key technical means to achieve ordered energy recovery and controllable charge elimination.

[0101] It should be further pointed out that the above analysis also implies that simply adding a passive short-circuit switch to an existing inductive energy recovery scheme (such as the existing single-inductor bidirectional multiplexing-based recovery scheme) will not achieve the technical effect of this scheme. This is because, without designing mutual exclusion timing constraints between the active recovery path and the passive short-circuit branch at the hardware level, the accidental conduction of the passive short-circuit branch during the active recovery phase will disrupt the integrity of the energy recovery process; and without introducing closed-loop control for residual charge threshold judgment, the triggering timing of passive discharge will lack a basis, and short-circuit discharge may occur when the residual voltage at the interface is still high, thus causing the energy waste and local temperature rise problems mentioned in the above analysis. This embodiment solves this contradiction through a tight coupling design of "triple reuse topology + closed-loop threshold iteration + active-passive mutual exclusion latch".

[0102] IX. Adaptability Description of Buck-Boost Converter Topology In the above embodiments, the switching power converter 100 is preferably a buck-boost converter. A further technical significance of using a buck-boost converter topology is that, in practical applications, the polarization voltage at the electrode interface... Depending on the stimulation parameters and electrode impedance characteristics, its value may be higher than, equal to, or lower than the system input voltage. During the power supply phase, the buck-boost topology allows the supply voltage to be either higher or lower than the input voltage to accommodate different electrode impedances and stimulation intensity requirements. In the active energy recovery phase, the polarization energy at the electrode interface is first converted into magnetic energy in the storage inductor L via an inductor energy storage sub-stage, and then fed back to the input voltage terminal via an inductor energy release sub-stage relying on the freewheeling characteristics of the storage inductor L. This energy recovery process is achieved through inductor freewheeling and does not depend on the polarization voltage. With input voltage The relationship between the magnitudes of the polarization voltage and the input voltage ensures that energy recovery can be completed regardless of whether the polarization voltage is higher, equal to, or lower than the input voltage, avoiding interruptions in the recovery process due to changes in voltage relationship. Therefore, the energy storage inductor L performs three functions in a time-sharing manner during the power supply phase, the forward energy recovery phase, and the reverse energy recovery phase: voltage conversion and energy storage, forward polarization energy conversion, and reverse polarization energy conversion.

[0103] Therefore, this circuit can achieve energy recovery under various operating conditions where the polarization voltage and input voltage have different magnitudes. This wide range adaptability is a significant advantage of this circuit compared to a buck topology scheme.

[0104] 10. Technical Effects Description This embodiment achieves deep system-level multiplexing of the energy storage inductor and power switches in the switching power converter. This allows the same energy storage inductor and the same set of power switches to perform three functional roles in power conversion, forward / reverse polarization energy recovery, eliminating the need for a separate energy recovery inductor, reducing the number of dedicated recovery switches, and thus lowering circuit area and system cost. The cross-multiplexing of some switches and recovery switches in the full-bridge power switch group, along with the redistribution of electrical functions, creates a symmetrical structure where the energy recovery paths after forward and reverse stimulation share a third power switch and energy storage inductor, further improving hardware resource utilization.

[0105] The synergistic cooperation between closed-loop iterative active energy recovery and conditional passive discharge allows inductive recovery to first recover the majority of interface polarization energy to the input, followed by passive discharge to eliminate the remaining trace deviation. The two are interdependent and work together: inductive recovery reduces the transient current during passive discharge, while the fallback effect of passive discharge allows inductive recovery to exit earlier with fewer iterations. The active-passive mutual exclusion timing constraint helps avoid simultaneous operation of the two power paths, reducing the risk of energy waste and localized temperature rise caused by direct short circuits under high residual voltage.

[0106] The use of a buck-boost converter topology allows the system's supply voltage to be higher or lower than the input voltage. During active energy recovery, polarization energy is fed back to the input voltage terminal via the freewheeling characteristic of the energy storage inductor. This ensures effective energy return capability under various operating conditions where the polarization voltage and input voltage have different magnitudes, and even when the polarization voltage dynamically decreases during recovery, thus improving adaptability to different electrode impedances and polarization voltage ranges. The mutually exclusive configuration of the voltage stimulation switch and the stimulation current source on the same hardware platform enables compatible switching between constant current and constant voltage dual-mode stimulation.

[0107] In summary, the synergistic effect of the above-mentioned technical features enables the charge balance circuit and its control method disclosed herein to achieve both the recovery and reuse of interface polarization energy and the controllable elimination of residual charge while minimizing hardware resources. This is beneficial for reducing the overall power consumption of the system, suppressing ineffective temperature rise, and helping to control the residual voltage at the electrode-external load interface during long-term operation within a preset safe range.

[0108] The embodiments of this application are further explained below by way of example.

[0109] In one exemplary implementation, the residual charge monitoring circuit 300 includes a differential sampling circuit and a hysteresis comparator. The differential sampling circuit differentially samples the voltage across the electrode to obtain a residual polarization voltage signal. The hysteresis comparator compares this residual polarization voltage signal with a preset threshold voltage. When the absolute value of the residual polarization voltage signal is greater than or equal to the threshold voltage, it outputs a first-level signal, triggering the system to continue active energy recovery; when the absolute value of the residual polarization voltage signal is less than the threshold voltage, it outputs a second-level signal, allowing the passive discharge switch S10 to close. The hysteresis characteristic of the hysteresis comparator avoids frequent false switching due to noise interference near the threshold. In another exemplary implementation, the residual charge monitoring circuit 300 includes an integrator charge quantization circuit and an analog-to-digital converter (ADC). The integrator performs time integration on the residual current at the electrode interface to obtain a digitally quantized value of the residual charge. Then, the numerical comparison logic will... With preset threshold The comparison is then used to generate control commands. Compared to differential voltage sampling, integral quantization directly measures the residual charge rather than indirectly calculating it through voltage, which may result in higher charge estimation accuracy in scenarios where the electrode interface impedance changes significantly over time.

[0110] Taking the charge balance process after positive current stimulation as an example, the switching states of each stage are shown in the table below ("1" indicates conduction, "0" indicates deactivation, and "-" indicates that the switching state does not affect the function of the current stage): It should be noted that the S1 to S4 states in the power supply stage (when the switching power supply converter is working normally) in the table above depend on the specific modulation strategy of the buck-boost converter, and are omitted here to avoid limiting the protection range.

[0111] In one exemplary embodiment, the inductance of the energy storage inductor L can be selected from, for example, the nanohenry to tens of microhenry levels, with the specific value determined based on the input voltage range, supply voltage requirements, and switching frequency. The stimulation current range can cover the microampere to milliampere levels, and the stimulation frequency can cover the range of several hertz to several kilohertz to adapt to different application protocols. The preset threshold can be set according to the electrode type and external load characteristics, for example, set to a fraction of the upper limit of the safe polarization voltage window. The closing duration of the passive discharge switch S10 is dynamically adjusted according to the residual charge, with a typical duration being a fraction of the duration of a single stimulation cycle. The residual charge monitoring circuit samples at least once after each active recovery iteration.

[0112] In one exemplary embodiment, to avoid short circuits caused by direct connection of switches in the upper and lower arms of the same bridge arm, a dead-time window is introduced for each complementary switch pair during state switching. Specifically, the currently active switch is first turned off, and a preset dead-time is waited before the complementary switch is turned on. Specifically, when S7 switches from the stimulation path to the recovery path, S6 is first turned off, and the dead-time is waited before S3 and S9 are turned on; when switching from the inductor energy storage sub-stage to the inductor energy release sub-stage, S7, S3, and S9 are first turned off, and the dead-time is waited before S1 and S4 are turned on. This dead-time is guaranteed by the hardware logic of the drive circuit, and its specific duration is set according to the turn-off delay characteristics of the power switches. Similarly, when switching from the active energy recovery stage to the passive discharge stage, the passive discharge switch S10 is allowed to close only after all relevant switches in the active recovery path are turned off, to avoid the simultaneous conduction of two power paths.

[0113] Optionally, at the switching moment between the inductor energy storage sub-stage and the inductor energy release sub-stage, the system control logic detects the current on the energy storage inductor L. ,when The switching of the operating phase is completed when the voltage crosses zero in the reverse direction or drops to near zero, so as to reduce the voltage and current overlap loss during switching. Zero-crossing detection can be achieved by connecting a miniature sensing resistor and a comparator in series in the inductor circuit, with the threshold of the comparator set to a reference voltage close to zero.

[0114] Optionally, a preset threshold is used. The system can adaptively adjust based on its operating status. For example, the system records the actual residual voltage at the end of each stimulation cycle. The feedback information is then used to adjust the threshold for the next cycle. The adjustment relationship can be expressed as: in, For the first The threshold of the period, For the first The measured residual voltage after the periodic passive discharge ends. This is a correction factor. Through adaptive threshold adjustment, the system can maintain a suitable active recovery-passive discharge switching point under different electrode impedances and operating conditions.

[0115] Optionally, the residual charge monitoring circuit 300 can be configured with multiple threshold levels. For example, a first threshold can be set. Second threshold ,in When residual charge deviation At this time, the system continues to actively recover energy by executing the inductor energy storage-discharge cycle; when Residual charge deviation When the residual charge deviates, the system triggers the passive discharge switch S10 to discharge; When the preset safety range is reached, the system determines that the current cycle has ended. Multi-level thresholds refine the charge balance process into more precise multi-level state control.

[0116] To prevent infinite loop iterations due to circuit faults or extreme operating conditions, the system can set an upper limit on the number of iterations. When the number of iterations for active energy recovery reaches the preset upper limit and the residual charge deviation has not yet decreased below a preset threshold, the system keeps the passive discharge switch S10 open and enters an abnormal protection state. The abnormal protection state includes at least one of pausing the entry into the next stimulation cycle, reducing the intensity of subsequent stimulation, outputting a fault warning signal, or waiting for external control commands. Thus, the upper limit on the number of iterations is used to limit the maximum duration of the active energy recovery process without changing the condition under which the passive discharge switch S10 is controlled by the residual charge deviation threshold. The specific value of the upper limit on the number of iterations can be determined based on the maximum time allowed to be allocated to the charge balance process within a single stimulation cycle and the typical duration of each recovery cycle.

[0117] After the passive discharge switch S10 is closed, the system can continuously monitor the potential difference across the electrodes through the residual charge monitoring circuit 300. When the absolute value of the residual polarization voltage across the electrodes decreases to a preset safe voltage range (i.e., ,in When the voltage reaches the preset safe voltage value, the passive discharge switch S10 is disconnected, ending the charge balance process of the current stimulation cycle. Optionally, a fixed discharge duration can be preset, which is determined based on the typical RC time constant of the electrode interface, and S10 is automatically disconnected after the discharge time is reached. Simultaneously, an upper limit can be set on the number of times S10 can be closed. To prevent repeated releases under abnormal circumstances.

[0118] Under a set of exemplary simulation conditions, the recovery efficiency of this scheme is... A high level of performance can be achieved. Compared with the pure passive short-circuit scheme, since most of the polarization energy is recovered and reused instead of being dissipated as heat, the system power consumption of this scheme is relatively reduced, and the peak transient current during the passive discharge stage is also correspondingly smaller than that of the pure passive short-circuit scheme. Compared with the pure inductive recovery scheme (without passive discharge as a fallback), this scheme reduces the number of iterations of inductive recovery through the auxiliary zeroing of passive discharge, and has an advantage in terms of balancing time. The above results show that the synergistic combination of active recovery and passive discharge is superior to any single scheme in terms of power consumption, accuracy, and temperature rise, verifying the existence of the synergistic effect.

[0119] In an exemplary waveform, the inductor current During the power supply phase, the charging and discharging waveform exhibits a sawtooth shape; during the active recovery inductor energy storage phase, Gradually rising from zero, polarization energy is converted into magnetic energy; in the inductor energy release stage, The voltage gradually decreases until it returns to near zero, corresponding to the energy pump returning to the input terminal. The voltage across the electrodes... During the stimulation phase, a voltage waveform corresponding to the stimulation pulse is presented. During the active recovery phase, the voltage gradually decreases, and during the passive discharge phase, it rapidly returns to zero via a short circuit. The residual charge monitoring circuit samples the voltage at the end of each inductor discharge phase and determines whether to proceed to the next iteration or trigger passive discharge based on the sampling results.

[0120] Optionally, in multi-electrode channel applications, multiple electrode channels can share the same energy storage inductor L. The system employs a channel scheduling controller to allocate time slices to each channel, sequentially completing the "stimulation—active energy recovery—residual charge monitoring—conditional passive discharge" process within each time slice. The scheduling between channels can employ a fixed polling method or a priority scheduling method based on residual charge deviation, meaning channels with larger residual charge deviations have priority in using the energy storage inductor. This scheduling strategy allows multiple electrode channels to share the same energy storage inductor and power switch group, further reducing hardware redundancy in multi-channel systems.

[0121] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, if a reference is made to performing an action based on an element, it means performing the action at least based on that element, including two cases: performing the action only based on that element, and performing the action based on that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0122] Furthermore, it should be understood that after reading the above disclosure of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A charge balance control method for an electrical stimulation device, characterized in that, The electrical stimulation device includes a switching power converter with an energy storage inductor, a full-bridge power switch group, a recovery circuit, a passive discharge switch connected across the electrodes, and a residual charge monitoring circuit. The electrode is used to connect to an external load; the method includes: Stimulation steps: The switching power converter generates a supply voltage based on the input voltage via the energy storage inductor, controls the full-bridge power switch group to turn on to drive the electrode to output a stimulation signal, and generates polarization charge and stores polarization energy at the electrode interface; Active energy recovery step: After the stimulation signal output ends, the passive discharge switch remains open; some switches in the full-bridge power switch group are cross-multiplexed with the recovery circuit, and the energy storage inductor and some power switches in the switching power converter are also multiplexed to form an active energy recovery path. The polarization energy is converted into the magnetic energy of the energy storage inductor through the inductor energy storage sub-stage, and then the magnetic energy is sent back to the input voltage terminal through the inductor discharge sub-stage. In the stimulation step, the energy storage inductor undertakes the voltage conversion and energy storage function, and in the active energy recovery step, it undertakes the polarization energy conversion function. The switches in the full-bridge power switch group undertake the stimulation current path in the stimulation step and the recovery current path in the active energy recovery step. Residual charge monitoring step: The residual charge monitoring circuit samples the two ends of the electrode to obtain the residual charge deviation after the active energy recovery step, and compares the residual charge deviation with a preset threshold to generate a comparison result; Closed-loop iteration and conditional passive discharge steps: The comparison result is used to determine the subsequent charge balance path; if the comparison result indicates that the residual charge deviation is greater than or equal to the preset threshold, the active energy recovery step and the residual charge monitoring step are triggered to be executed again according to the comparison result, forming a closed-loop iteration; if the comparison result indicates that the residual charge deviation is less than the preset threshold, the passive discharge switch is closed to physically short-circuit the two ends of the electrode to perform passive discharge and eliminate the residual potential deviation; wherein, during the execution of the active energy recovery step, the passive discharge switch remains open and operates mutually exclusive with the active energy recovery path.

2. The charge balance control method according to claim 1, characterized in that, The full-bridge power switch group includes a first bridge arm upper arm switch (S5), a first bridge arm lower arm switch (S6), a second bridge arm upper arm switch (S7), and a second bridge arm lower arm switch (S8); the power switch group of the switching power converter includes a first power switch (S1), a second power switch (S2), a third power switch (S3), and a fourth power switch (S4); the recycling circuit includes a first recycling switch (S9) and a second recycling switch (S12); the passive discharge switch is S10.

3. The charge balance control method according to claim 2, characterized in that, The stimulation steps include a positive stimulation mode, in which: the second bridge arm upper arm switch (S7) and the first bridge arm lower arm switch (S6) are turned on, and the current flows from the power supply voltage terminal through S7 to one end of the electrode, passes through the external load, and then flows through S6 to the reference ground, thus completing the positive stimulation signal output; The active energy recovery step corresponding to the positive stimulus includes the inductive energy storage sub-stage and the inductive energy release sub-stage: In the inductor energy storage sub-stage, the first recovery switch (S9), the second bridge arm upper arm switch (S7), and the third power switch (S3) are controlled to be turned on. The polarization voltage stored at the electrode interface drives the polarization current to flow through S7 and S3 into the energy storage inductor, converting the polarization energy into the magnetic energy of the energy storage inductor, forming a positive active energy recovery path. During the inductor energy release phase, the first power switch (S1) and the fourth power switch (S4) are turned on, and the energy storage inductor sends the magnetic energy back to the input voltage terminal via S1.

4. The charge balance control method according to claim 2, characterized in that, The stimulation steps include a reverse stimulation mode, in which: the first bridge arm upper arm switch (S5) and the second bridge arm lower arm switch (S8) are turned on, and the current flows from the power supply voltage terminal through S5 to one end of the electrode, passes through the external load, and then flows through S8 to the reference ground, thus completing the reverse stimulation signal output; The active energy recovery step corresponding to the reverse stimulus includes the inductor energy storage sub-stage and the inductor energy release sub-stage: In the inductor energy storage sub-stage, the first bridge arm upper arm switch (S5), the third power switch (S3), and the second recovery switch (S12) are controlled to be turned on. The interface potential generated by reverse polarization drives the polarization current to flow through S5 and S3 into the energy storage inductor, converting the polarization energy into the magnetic energy of the energy storage inductor, forming the reverse active energy recovery path. During the inductor energy release phase, the first power switch (S1) and the fourth power switch (S4) are turned on, and the energy storage inductor sends the magnetic energy back to the input voltage terminal via S1.

5. The charge balance control method according to claim 1, characterized in that, The electrical stimulation device further includes a stimulation current source and a voltage stimulation switch (S11) as well as a current / voltage stimulation selection module; the method further includes a stimulation mode switching step: When the current / voltage stimulation selection module selects current stimulation, the voltage stimulation switch is turned off (S11) and the stimulation current source is enabled. The stimulation current source and the full-bridge power switch group output a current stimulation signal to the electrode. When the current / voltage stimulation selection module selects voltage stimulation, the stimulation current source is turned off and the voltage stimulation switch is turned on (S11), and the voltage stimulation signal is directly output to the electrode through the full-bridge power switch group using the power supply voltage. The conduction signal of the voltage stimulation switch (S11) and the enable signal of the stimulation current source are mutually exclusive, and the conduction state of the voltage stimulation switch (S11) and the enable state of the stimulation current source are not simultaneously established at any time.

6. The charge balance control method according to claim 1, characterized in that, The switching power converter is a buck-boost converter, which enables the energy storage inductor to cooperate with the power switch group to convert the input voltage into a supply voltage that is higher or lower than the input voltage in the stimulation step, and to return the polarization energy of the electrode interface to the input voltage terminal in the active energy recovery step.

7. An electrode charge balancing circuit, characterized in that, include: A switching power converter includes an energy storage inductor and a power switch assembly. Its power input is connected to an external power source, and its power output is used to provide the supply voltage. A full-bridge power switch assembly is connected to the power output terminal of the switching power converter and is used to drive the electrodes to output stimulation signals based on the supply voltage, so that polarization charges are generated at the electrode interface and polarization energy is stored; the electrodes are used to connect to an external load. The energy recovery circuit includes a recovery switch, one end of which is connected to the electrode and the other end to the energy storage inductor. After the stimulation signal output ends, the recovery circuit is used to cross-multiplex with some switches in the full-bridge power switch group and some power switches in the switching power converter, using the energy storage inductor to form an active energy recovery path, thus returning the polarization energy to the external power supply terminal via inductor storage and inductor discharge. The energy storage inductor performs voltage conversion and energy storage functions during the power supply phase and polarization energy conversion functions during the recovery phase. The switches in the full-bridge power switch group serve as stimulation current paths during the stimulation phase and recovery current paths during the recovery phase. The residual charge monitoring circuit has its sampling input terminal connected to both ends of the electrode to sample and obtain the residual charge deviation and compare it with a preset threshold to generate a comparison result; its control output terminal is connected to the trigger terminal of the recovery circuit and the controlled terminal of the passive discharge switch respectively; when the comparison result indicates that the residual charge deviation is greater than or equal to the preset threshold, the control output terminal triggers the recovery circuit to continue to perform active energy recovery, forming a closed-loop iteration. A passive discharge switch is connected across the two ends of the electrode. The passive discharge switch is closed in control only when the comparison result indicates that the residual charge deviation is less than the preset threshold to physically short-circuit the two ends of the electrode for passive discharge and eliminate the residual potential deviation. During the operation of the active energy recovery path, the passive discharge switch remains open and operates mutually exclusive with the active energy recovery path.

8. The electrode charge balance circuit according to claim 7, characterized in that, The full-bridge power switch group includes a first bridge arm upper arm switch (S5), a first bridge arm lower arm switch (S6), a second bridge arm upper arm switch (S7), and a second bridge arm lower arm switch (S8); the power switch group of the switching power converter includes a first power switch (S1), a second power switch (S2), a third power switch (S3), and a fourth power switch (S4); the recycling circuit includes a first recycling switch (S9) and a second recycling switch (S12); the passive discharge switch is S10; The active energy recovery path after positive stimulation is formed by the first recovery switch (S9), the second bridge arm upper arm switch (S7), the third power switch (S3), and the energy storage inductor; the active energy recovery path after reverse stimulation is formed by the second recovery switch (S12), the first bridge arm upper arm switch (S5), the third power switch (S3), and the energy storage inductor; the two recovery paths share the third power switch (S3) and the energy storage inductor, and during the inductor energy release stage, they share the first power switch (S1) and the fourth power switch (S4) to send the magnetic energy back to the external power supply.

9. The electrode charge balance circuit according to claim 7, characterized in that, It also includes a stimulation current source, a voltage stimulation switch (S11), and a current / voltage stimulation selection module; the stimulation current source is connected in series between the full-bridge power switch group and the reference ground; the voltage stimulation switch (S11) is connected in parallel with the stimulation current source; the control output terminal of the current / voltage stimulation selection module is connected to the voltage stimulation switch (S11) and the stimulation current source, and is used to switch between current stimulation mode and voltage stimulation mode; wherein, the conduction signal of the voltage stimulation switch (S11) and the enable signal of the stimulation current source are mutually exclusive.

10. An electrical stimulation system, characterized in that, Includes an electrode charge balancing circuit as described in any one of claims 7 to 9, and an external load connected to the electrodes of the electrode charge balancing circuit; the electrostimulation system recovers and reuses interface polarization energy by performing closed-loop iterative active energy recovery and mutually exclusive conditional passive discharge, thereby reducing system power consumption and eliminating residual voltage accumulation during long-term operation.

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