Four-mode Boost / Buck reconfigurable energy recovery circuit

Abstract

A four-mode Boost / Buck reconfigurable energy recovery circuit includes multiple switch tubes, power inductors, thermoelectric generators, oscillators, charge pumps, storage capacitors, maximum power point tracking circuits, zero current detection circuits, first voltage detectors, second voltage detectors, multiple comparators, RS triggers, and mode control modules. The present invention switches between four modes when an asynchronous signal triggers; when the energy source has sufficient energy, the supply mode is converted to the storage mode to increase the overall transmission power; when the energy source is insufficient, the circuit is configured to be in the extraction mode, and the storage capacitor supplies power to the load voltage. Even when the energy is insufficient, the thermoelectric generator TEG is combined with the storage capacitor to supply power to the load, thereby ensuring the stability of the load voltage and improving the overall energy extraction efficiency, achieving stable supply of the load, and improving the maximum power point tracking accuracy, achieving full energy collection.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, and in particular relates to a Boost / Buck reconfigurable energy recovery circuit with four modes: storage, supply, extraction and circulation. Background Art

[0002] Thermal energy harvester (TEG) uses the temperature difference between the skin surface and the environment to generate electricity, so it is very suitable for providing continuous, environmental and stable supplementary power for flexible biosensors. Its main feature is that the thermal energy harvester is proportional to the temperature difference, with a coefficient of 25mV / ℃. Therefore, the thermal energy recovery circuit should be able to start and work at ultra-low voltage, and convert tens of millivolts into a voltage source of about 1V to provide power for the sensor core circuit. However, the temperature difference changes with the environment, causing the TEG output voltage to change slowly and continuously, seriously affecting the conversion efficiency of the thermal energy recovery circuit.

[0003] Most traditional thermal energy recovery circuits are based on the situation that the power provided by TEG is "just enough". At this time, maximum power point tracking (MPPT) and zero current switching (ZCS) are effective technologies to improve conversion efficiency. However, in fact, the power of TEG changes with the real-time temperature. When the power provided by TEG is lower than or higher than the demand, it is not enough to use MPPT and ZCS alone. When the energy is sufficient, the excess energy needs to be extracted and stored. When the energy is insufficient, the stored energy needs to be supplemented in time to ensure the normal operation of the load. In order to achieve this goal, domestic and foreign scholars have also conducted further research on energy recovery and management circuits. YK Ramadass et al. (YK Ramadass and A.P. Chandrakasan, "A battery-less thermoelectric energy harvesting interface circuit with 35mV startup voltage," IEEE J. Solid-State Circuits, vol. 46, no. 1, pp. 333–341, Jan. 2011) adopted a cascade structure, in which the first stage uses a Boost circuit to boost the voltage to 2.4V and store the energy in the energy storage unit, and the second stage uses a Buck step-down circuit to adjust the output voltage. This structure increases the number of off-chip components and limits the overall efficiency to a low level. P.Cao et al. (P.Cao, Y.Qian, P.Xue, D.Lu, J.He, and Z.Hong, "Abipolar-inputthermoelectric energy-harvesting interface with boost / flyback hybridconverter and on-chip cold starter," IEEE J.Solid-State Circuits, vol.54, no.12, pp.3362–3374, Dec.2019) proposed a single-mode dual-output (SIDO) structure in which the output is divided into a storage voltage and a load voltage. However, when the input power P IN Less than the output power P OUTWhen the storage capacitor is directly connected to the load voltage, the load voltage will be out of control. D. El-Damak et al. (D. El-Damak and A.P. Chandrakasan, "A 10nW–1μW Power Management IC With Integrated Battery Management and Self-Startup for Energy Harvesting Applications," in IEEE Journal of Solid-State Circuits, vol. 51, no. 4, pp. 943-954, April 2016) proposed a Buck / Boost structure. When the input power P IN Greater than P OUT Boost mode works, but manual control is required to select whether to charge the battery or the load. IN <P OUT When P is 0, the Buck mode works, but it stops collecting energy from the energy source, which will lead to a decrease in energy extraction efficiency. Most of the current energy recovery circuits use Buck / Boost structure to increase the maximum power of energy recovery, but when P IN <P OUT When the power is off, the Buck mode works, but the energy collection from the energy source stops at this time, which still leads to insufficient energy recovery and reduced energy extraction efficiency. In addition, circuits with such structures usually require additional power to power the drive circuit, and cannot achieve true self-powering. Summary of the invention

[0004] In view of the problems of insufficient energy extraction and low energy transfer efficiency of the above-mentioned traditional thermal energy collection and management circuits, the present invention adopts a startup scheme based on an LC oscillator to achieve self-starting. IN >P OUT When a single mode dual output (SIDO) structure is used, the output is divided into a storage voltage V STORE and load voltage V LOAD , and realize autonomous control Boost so that the storage voltage V STORE and load voltage V LOAD The voltage increases, and at the same time, the P IN <P OUT When using Buck mode, use the storage capacitor C store While supplying power, it continues to collect energy from the energy source to improve the energy extraction efficiency. Only when the thermoelectric power generation sheet can no longer output power will it stop collecting energy from the thermoelectric power generation sheet, thereby improving the problem of insufficient energy recovery when the output power of the thermoelectric power generation sheet is insufficient.

[0005] The specific working logic of the four modes proposed by the present invention is as follows:

[0006] After the startup phase is completed, when the power provided by the thermoelectric generator TEG is "just enough", the load voltage V LOAD In the target range [V L ,V H ], the system is configured as a Boost converter and works in supply mode; as the ambient temperature gradually increases, the temperature difference on the surface of the thermoelectric generator increases, and the power P provided by the TEG IN >P OUT , if V LOAD >V H , the system switches to storage mode and the Boost converter gives C store Charging causes the storage voltage to increase continuously, and the storage mode continues until V LOAD <V M If the ambient temperature drops, the temperature difference on the surface of the thermoelectric generator decreases, and the power P of the TEG system IN <P OUT , detect V LOAD <V L After that, it is configured as a Buck converter. If V OTEG <V OL In recovery mode, only the storage capacitor C is used. store is the load voltage V LOAD Power supply, if the open circuit voltage of the thermoelectric generator is V OTEG >V OL It works in the extraction mode. At this time, the thermoelectric generator TEG and the storage capacitor are combined to power the load. This not only ensures the stability of the load voltage, but also improves the overall energy extraction efficiency, achieves stable supply of the load, and improves the maximum power point tracking accuracy to achieve full energy collection.

[0007] The present invention adopts the following technical solutions:

[0008] A Boost / Buck reconfigurable energy recovery circuit with four modes of storage, supply, extraction and circulation, which is characterized in that it includes switch tubes M1, M2, M3, M4, M5, M6, M7, M8, M9 and S1, power inductor, Copitts oscillator, Dickson charge pump, storage capacitor C store , maximum power point tracking circuit MPPT, oscillator OSC, zero current detection circuit ZCS, first voltage detector, second voltage detector, first comparator, second comparator, third comparator, fourth comparator, RS trigger, mode control module.

[0009] One end of the first switch tube is connected to one end of the power inductor, one end of the second switch tube, one end of the third power tube and one end of the seventh switch tube, and the other end is connected to the load voltage; the other end of the first switch tube is grounded; the other end of the third switch tube is connected to the storage voltage V STORE , storage capacitor C store one end of the fourth switch tube; the other end of the fourth switch tube is connected to the other end of the power inductor, the sixth switch tube and one end of the fifth switch tube; the other end of the fifth switch tube is grounded; the other end of the sixth switch tube is connected to the output of the temperature difference power generation sheet and one end of the eighth switch tube; the other end of the seventh switch tube is connected to the output of the Dickson charge pump; the other end of the eighth switch tube is connected to the storage capacitor C store The other end of the switch tube S1 is connected to the load voltage, and the other end is grounded.

[0010] The other end output of the Copitts oscillator is connected to the input of the Dickson charge pump, and together they serve as a startup circuit of the overall circuit to provide a startup voltage for the system.

[0011] The first voltage detector is connected to the output of the Dickson charge pump, and the output signal is connected to the input of the Copitts oscillator. The Dickson charge pump only uses the single clock signal generated by the Copitts oscillator to make the output V DD The potential rises, when V DD When the potential reaches 1.1V, the first voltage detector generates an enable signal OFF_OSC, the Copitts oscillator stops working, and the Boost / Buck reconfigurable energy recovery circuit with four modes of storage, supply, extraction and circulation starts working. At this time, the charge pump outputs V DD The control module is powered. The input of the second detector is connected to the load voltage, and the output control is connected to the gate of the switch tube S1.

[0012] The input of the maximum power point tracking circuit MPPT is connected to the output of the thermoelectric generator, and the output is connected to the input of the oscillator OSC; the oscillator OSC provides a clock signal at the operating frequency of the converter system according to the output control signal of the MPPT.

[0013] Preferably, the maximum power point tracking circuit MPPT can achieve that the output voltage of the thermoelectric generator is always half of the open circuit voltage of the thermoelectric generator, and the equivalent resistance R of the converter is EQ The equivalent internal resistance R of the thermoelectric generator T Keep equal, at this time the power output of the thermoelectric generator satisfies:

[0014]

[0015] Where V OTEG is the open circuit voltage of the thermoelectric generator, R T is the equivalent output resistance of the thermoelectric generator.

[0016] The zero current detection circuit ZCS input is connected to the load voltage V LOAD , storage voltage V STORE The voltage on both sides of the inductor is used to detect whether the inductor current is reversed.

[0017] Preferably, the zero current detection circuit ZCS monitors the relationship between the voltage on one side of the inductor and the target voltage in real time in each cycle according to the system clock generated by the OSC module to adjust the discharge time of the power inductor and ultimately control the duty cycle of the converter to prevent the inductor current from reversing.

[0018] One end of the first comparator is connected to the load voltage and the off-chip reference voltage, and outputs a control buck-boost mode switching signal; one end of the second comparator is connected to the load voltage and the second off-chip reference voltage, and one end of the third comparator is connected to the load voltage and the third off-chip reference voltage, and the outputs are connected to the reset end and the set end of the RS trigger respectively. One end of the fourth comparator is connected to the open circuit voltage of the thermoelectric power generation chip and compared with the fourth off-chip reference voltage, and outputs the control signal of the extraction and circulation mode in the buck mode.

[0019] The mode control module generates clock signals CLK1, CLK2, CLK3, CLK4, CLK5, CLK6, CLK7, CLK8 and CLK9 for driving the gates of the switch tubes according to the mode control signal.

[0020] Preferably, the four working modes include a supply mode in which the energy source supplies power to the load voltage and works in a Boost mode; a storage mode in which the energy source supplies power to the load voltage and works in a Boost mode; an extraction mode in which the storage capacitor supplies power to the load voltage and works in a Buck mode; and a circulation mode in which the temperature difference power generation points are stacked under the storage capacitor and supply power to the load voltage together and work in a Buck mode.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] There are four working modes: supply mode, storage mode, extraction mode, and circulation mode. They switch between different modes under the trigger of asynchronous signals. When the energy source has sufficient energy, the system switches from supply mode to storage mode to increase the overall transmission power. When the energy source is insufficient, the system is configured to extraction mode, and the storage capacitor supplies power to the load voltage. Even when the energy is insufficient, the thermoelectric generator TEG is combined with the storage capacitor to supply power to the load. This not only ensures the stability of the load voltage, but also improves the overall energy extraction efficiency, realizes stable supply of the load, and improves the maximum power point tracking accuracy to achieve full energy collection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The circuit diagram of the four-mode Boost / Buck reconfigurable energy recovery circuit of the present invention is shown in FIG.

[0024] Figure 2 This is a circuit diagram of the four modes of supply, storage, circulation and extraction proposed by the present invention.

[0025] Figure 3 This is a schematic diagram of a self-starting circuit proposed by the present invention for the low output voltage of a thermoelectric generator.

[0026] Figure 4 Schematic diagram of the key signal for transitioning from low-voltage startup of the circuit to normal power supply proposed by the present invention

[0027] Figure 5 Schematic diagram of key signals for switching from supply mode to storage mode proposed by the present invention

[0028] Figure 6 Schematic diagram of key signals for switching from circulation mode to supply mode proposed by the present invention

[0029] Figure 7 Schematic diagram of the key signal for switching from the circulation mode to the extraction mode proposed by the present invention

[0030] Figure 8 This is a schematic diagram of the maximum end-to-end efficiency achieved by the system in different modes and the proportion of energy consumption under different voltages in the extraction mode proposed by the present invention. DETAILED DESCRIPTION

[0031] The technology of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but this should not limit the protection scope of the present invention.

[0032] See also Figure 1 , Figure 1The circuit diagram of the four-mode Boost / Buck reconfigurable energy recovery circuit of the present invention is shown in the figure. As shown in the figure, it includes switch tubes M1, M2, M3, M4, M5, M6, M7, M8, M9 and S1, power inductor L, Copitts oscillator, Dickson charge pump, off-chip RF choke L RFC , maximum power point tracking circuit MPPT, oscillator OSC, zero current detection circuit ZCS, first voltage detector, second voltage detector, first comparator, second comparator, third comparator, fourth comparator, RS trigger, mode control module;

[0033] R LOAD is the load resistance of the converter, C load is the output capacitance of the converter, C store is the storage capacitor, L RFC This is an off-chip RF choke used as a bias current source in the Copitts oscillator of the startup module. dd is the output capacitor of the Dickon charge pump, used as the power supply during the transition from the startup phase to the supply mode. OTEG is the open circuit voltage of the thermoelectric generator, V IN It is the output voltage of the converter when it is working normally. Among them, Copitts and Dickon constitute a startup module, which is used to start at an ultra-low voltage and output a power supply voltage for the control module to work. Among them, the first voltage detector and the second voltage detector are voltage detectors that can detect voltage without a voltage reference.

[0034] The maximum power point tracking circuit MPPT is based on the maximum power transfer theory. When the internal impedance of the energy source is the same as the equivalent impedance, the load power can be maximized. The formula is as follows:

[0035]

[0036] Because R EQ Proportional to the switching frequency fs of the converter:

[0037]

[0038] L is the power inductor value, Ton is the ON-Time of the pulse signal for inductor charging, R T is the internal resistance of the thermoelectric generator TEG. In order to reduce the variables, Ton is fixed to half of the switching cycle, and we can get:

[0039]

[0040] Then, by adaptively controlling fs, R can be intuitively controlled. EQ .

[0041] The zero current detection circuit ZCS is mainly based on the principle of volt-second balance, and adopts two modes, fast adjustment and slow adjustment, so that the circuit can be adjusted to the optimal conduction time more quickly, further improving the overall efficiency. If the inductor discharge switch is turned off too quickly, the inductor current has not dropped to 0, and the remaining inductor current flows through the parasitic diode, which will force the voltage on the side where the switch tube is connected to the inductor to increase. On the other hand, if the switch tube is turned off too late, the inductor current will reverse, which will cause the inductor current to flow in the reverse direction, and it is very likely that the load voltage will drop below zero. The zero current detection circuit ZCS circuit detects the voltage on one side of the inductor and compares it with the reference voltage in different modes to detect whether the inductor current is reversed, so that the inductor discharge time can always be kept at the optimal conduction time, improving the energy transmission efficiency.

[0042] like Figure 1 As shown, one end of the first switch tube M1 is connected to one end of the power inductor L, one end of the second switch tube M2, one end of the third power tube M3 and one end of the seventh switch tube M7, and the other end is connected to the load voltage; the other end of the second switch tube M2 is grounded; the other end of the third switch tube M3 is connected to the storage voltage V STORE , storage capacitor C store one end of the fourth switch tube M3; the other end of the fourth switch tube M3 is connected to the other end of the power inductor L, the sixth switch tube M6 and one end of the fifth switch tube M5; the other end of the fifth switch tube M5 is grounded; the other end of the sixth switch tube M6 is connected to the output of the thermoelectric power generation sheet TEG and one end of the eighth switch tube M8; the other end of the seventh switch tube M7 is connected to the output of the Dickson charge pump 13; the other end of the eighth switch tube M8 is connected to the storage capacitor C store and one end of the ninth switch tube M9; the other end of the ninth switch tube M9 is grounded. One end of the switch tube S1 is connected to the load voltage, and the other end is grounded. The other end output of the Copitts oscillator 12 is connected to the input of the Dickson charge pump. The first voltage detector is connected to the output of the Dickson charge pump, and the output signal is connected to the input of the Copitts oscillator. The first voltage detector outputs an enable signal OFF_OSC, which connects the Copitts oscillator to stop working. The input of the second detector is connected to the load voltage, and the output control is connected to the gate of the switch tube S1. The maximum power point tracking circuit MPPT input is connected to the output of the thermoelectric generator, and the output is connected to the input of the oscillator OSC; the oscillator OSC provides a clock signal at the operating frequency of the converter system according to the output control signal of the MPPT. The zero current detection circuit ZCS input is connected to the load voltage V LOAD , storage voltage V STOREThe voltage on both sides of the inductor is used to detect whether the inductor current is reversed. One end of the first comparator COMP1 is connected to the load voltage and the off-chip reference voltage, and the output is a control buck-boost mode switching signal; one end of the second comparator COMP2 is connected to the load voltage and the second off-chip reference voltage, and one end of the third comparator COMP3 is connected to the load voltage and the third off-chip reference voltage, and the output is connected to the reset end and the set end of the RS trigger respectively. One end of the fourth comparator COMP4 is connected to the open circuit voltage of the thermoelectric power generation chip and the fourth off-chip reference voltage for comparison, and the control signal of the extraction and circulation mode in the buck mode is output. The mode control module generates clock signals CLK1, CLK2, CLK3, CLK4, CLK5CLK6, CLK7, CLK8, CLK9 to drive the gate of the switch tube according to the mode control signal.

[0043] The circuits of the four modes of supply, storage, circulation and extraction proposed by the present invention are as follows: Figure 2 In general, if V LOAD In the target range [V L ,V H ], the converter is in supply mode. The converter works in PFM modulation mode, modulating the frequency of the OSC module through the maximum power point tracking circuit MPPT to extract as much power as possible from the thermoelectric generator TEG. Therefore, the higher the temperature difference of the TEG, the lower the frequency to obtain a lower equivalent resistance R of the converter. EQ , and vice versa. LOAD In [V L ,V H ] range, the converter is configured in supply mode to extract maximum power while providing a relatively stable supply voltage for the core circuit.

[0044] As the temperature difference increases further, the power extracted by the core circuit will be higher than the required power, resulting in V LOAD >V H Therefore, if the power of the thermoelectric generator is still in the same state, the remaining energy will be wasted. At this time, the converter is configured in storage mode, and the Boost converter injects current into C in a time-multiplexed manner. store or C load In the charging path, Figure 2 (a) and Figure 2 (b) Switch between. If V LOAD <V H , it is configured as supply mode, resulting in the system being in V H The mode switches frequently near the value and causes loss. Therefore, an intermediate value needs to be set. LOAD >V H , adjust to storage mode until V LOAD <V MThen switch to supply mode.

[0045] As the temperature difference decreases, the extracted power is not enough for the core circuit, V LOAD will drop to V L To provide a stable load voltage, C store The stored energy is used as the power supply. Under this condition, the converter is configured as a Buck converter. If the open circuit voltage of the thermoelectric generator TEG, V OTEG Less than V OL , that is, the power that can be extracted from the thermoelectric generator TEG is even less than the power consumed by the extraction circuit, then V LOAD Directly from C via Buck converter store Extracted from Figure 2 (c) shows the cycling mode. If power can still be extracted from the TEG to the core circuit, the TEG is connected to C store Connect in series and use them as a common power supply to V LOAD Power supply, then work in extraction mode such as Figure 2 (d) In addition, after setting as a Buck converter, due to the uncertainty of the TEG voltage state, the MPPT circuit is turned off at this time, S1_EN becomes high, and the OSC is controlled by the S1_EN signal to generate a fixed frequency clock signal as the switching frequency of the Buck converter.

[0046] The self-starting circuit proposed by the present invention for the low output voltage of the thermoelectric generator is as follows Figure 3 When the thermoelectric generator TEG is powered on, the system only has a very low voltage from the thermoelectric generator TEG, which directly powers the startup circuit. The self-starting circuit consists of an enhanced Copitts oscillator and a Dickon charge pump to gradually increase the startup voltage V DD ,like Figure 3 (a). Once V DD reaches 1.1V, Figure 3 The start-up circuit shown in (a) stops working and the control module of the converter starts working, such as Figure 1 As shown in (f), the system is configured as a Boost converter, V LOAD The voltage continues to increase. When V LOAD After exceeding 1.1V, the voltage detector detects and then outputs S1_EN, turning on S1 and switching C load and C dd Short circuit, at this time Figure 3 The stage shown in (b) ends.

[0047] The key signal waveforms of the Boost / Buck reconfigurable energy recovery circuit with four modes of storage, supply, extraction and circulation in the present invention when the circuit is started at low voltage and then transitioned to normal power supply are as follows: Figure 4 As shown. Where V DD is the output voltage of the Dickon charge pump, V LOAD is the load voltage, V CLK is the oscillation clock output by the Copitts oscillator. TEG Greater than the minimum startup voltage (7mV), the startup phase of the oscillator begins. The Copitts oscillation output is a sine wave with an amplitude of 1.17V V CLK , and use it as the clock signal for the charge pump. DD 10nF C dd The capacitor charges until V DD reaches 1.1V. When V DD When the voltage is greater than 1.1V, the OFF_OSC signal becomes high, turning off the oscillator and starting the module. The control logic starts to work and outputs gate voltage control signals CLK2, CLK1, and CLK6. At the same time, in order to maintain V DD In the 1.1V-1.2V range, V DD When VDD drops to 1.1V, it starts to output CLK7 signal and time-division multiplexing with CLK1. When VDD reaches 1.2V, M7 is turned off, and only V LOAD The above is based on the start-up transition phase of the converter. LOAD When it is greater than 1.1V, S1_EN becomes low, S1 is turned on, and V LOAD With V DD Short circuit, the startup phase is completely over. At this time, due to V LOAD Greater than V L (1.1V), the system enters the supply mode, and the Boost converter mainly works through the CLK2, CLK1, and CLK6 control signals, so that V LOAD Rise further.

[0048] The key signal waveform of the conversion from the supply mode to the storage mode proposed by the present invention is as follows: Figure 5 As shown. When the temperature difference on the surface of the thermoelectric generator TEG is large, the TEG output power is greater than the load power. The system controls the converter to work alternately in supply mode and storage mode. This not only keeps the load within the normal power supply range, but also stores excess energy in time. The boost converter mainly controls the boost converter charging signal through the state of S2_EN. When V LOAD When it is higher than 1.3V, S2_EN is low, and the mode is adjusted to storage mode. The inductor is discharged through CLK3, and V STORE Charging. When V LOADWhen it drops from 1.3V to 1.2V, the storage mode is turned off and the supply mode is turned on. CLK1 is used to pass M1 to V LOAD Charging makes it rise. When the temperature difference on the surface of TEG is large and the output power is less than the output power of TEG, this process will continue to cycle.

[0049] The key signal waveform proposed by the present invention for switching from the circulation mode to the supply mode is as follows: Figure 6 shown. Figure 6 The figure shows the state change of the system in the process of TEG output power changing from small to large. When the VTEG voltage is 0, in order to maintain the normal operation of the load, S2_EN becomes high, the circulation mode is turned on, and the storage capacitor C is used. store As a power supply, the converter is configured as a Buck converter, which outputs V by controlling CLK4, CLK5, and CLK1. LOAD Charging. The energy stored when the energy is sufficient will be discharged when the energy is insufficient, avoiding energy waste and realizing self-circulation of energy. LOAD After charging from below 1.1V to 1.2V, S2_EN becomes low, M4 and M5 are turned off, and the system returns to the supply mode. As the temperature difference increases, the TEG output voltage gradually increases, and the Boost converter controls CLK1, CLK2, and CLK6 to increase V LOAD Boost.

[0050] The key waveform signal for switching from the circulation mode to the extraction mode proposed by the present invention is as follows: Figure 7 As shown. At the beginning V IN >0mV, in order to extract as much energy as possible from TEG, S4_EN becomes high, M8 is turned on, and the thermoelectric generator TEG is stacked under the storage capacitor, which serves as the input source of the Buck converter. By controlling the switch tubes M4 and M5 to V LOAD power supply to increase the energy extraction efficiency of TEG. OTEG When set to 0V, in order to prevent the Peltier effect of TEG from reducing efficiency, S4_EN is low, the switch tube M8 is turned off, and the circuit enters the circulation mode, in which the load current I L Purely from C store The storage capacitor C store Connected to ground through M9, only the storage capacitor is used as the power supply, and the load voltage is powered by controlling the switch tubes M4 and M5.

[0051] The circuit-level simulation of this example adopts the GF22FDX 22nm process and is simulated using Cadence's Spectre in the ADE (Analog Integrated Circuit Design Automation Simulation Software) environment. The maximum end-to-end efficiency achieved by the system at different voltages in different modes and the energy consumption of the system at different voltages in the extraction mode are as follows: Figure 6 As shown. Due to the use of MPPT and ZCS circuits, the end-to-end conversion efficiency peaks are 86.1% in both supply mode and storage mode, and 75.3% in recovery mode and extraction mode. In addition, in the extraction mode, even if the energy of the thermoelectric power generation sheet is insufficient, up to 27% of additional power can be extracted from the thermoelectric power generation sheet, which avoids the traditional energy collection system in P IN <P OUT When the energy is not collected, the energy recovery is insufficient, which increases the maximum power of energy recovery and improves the energy recovery efficiency.

[0052] A person skilled in the art may make various other specific modifications and combinations based on the technical inspirations disclosed in the present invention without departing from the essence of the present invention, and these modifications and combinations are still within the protection scope of the present invention.

Claims

1. A four-mode Boost / Buck reconfigurable energy recovery circuit, characterized in that: include: Switch tube S1, first switch tube M1, second switch tube M2, third switch tube M3, fourth switch tube M4, fifth switch tube M5, sixth switch tube M6, seventh switch tube M7, eighth switch tube M8, ninth switch tube M9, power inductor, temperature difference power generation sheet, Copitts oscillator, Dickson charge pump, storage capacitor C store , a maximum power point tracking circuit MPPT, an oscillator OSC, a zero current detection circuit ZCS, a first voltage detector, a second voltage detector, a first comparator, a second comparator, a third comparator, a fourth comparator, an RS trigger and a mode control module; One end of the first switch tube is connected to one end of the power inductor, one end of the second switch tube, one end of the third power tube and one end of the seventh switch tube, and the other end is connected to the load voltage; the other end of the first switch tube is grounded; the other end of the third switch tube is connected to the storage voltage V STORE , storage capacitor C store one end of the fourth switch tube; the other end of the fourth switch tube is connected to the other end of the power inductor, the sixth switch tube and one end of the fifth switch tube; the other end of the fifth switch tube is grounded; the other end of the sixth switch tube is connected to the output of the temperature difference power generation sheet and one end of the eighth switch tube; the other end of the seventh switch tube is connected to the output of the Dickson charge pump; the other end of the eighth switch tube is connected to the storage capacitor C store The other end of the ninth switch tube is connected to the load voltage, and the other end of the ninth switch tube is grounded; one end of the switch tube S1 is connected to the load voltage, and the other end is grounded; The other end output of the Copitts oscillator is connected to the input of the Dickson charge pump, and together they serve as the startup circuit of the overall circuit to provide a startup voltage for the system; The first voltage detector is connected to the output of the Dickson charge pump, and the output signal is connected to the input of the Copitts oscillator. The Dickson charge pump only uses the single clock signal generated by the Copitts oscillator to make the output V DD The potential rises, when V DD When the potential reaches 1.1V, the first voltage detector generates an enable signal OFF_OSC, the Copitts oscillator stops working, and the four-mode Boost / Buck reconfigurable energy recovery circuit starts working, and the charge pump outputs V DD Power is supplied to the control module, the input of the second voltage detector is connected to the load voltage, and the output control is connected to the gate of the switch tube S1; The input of the maximum power point tracking circuit MPPT is connected to the output of the thermoelectric generator, and the output is connected to the input of the oscillator OSC; the oscillator OSC provides a clock signal at the operating frequency of the converter system according to the output control signal of the MPPT.

2. The four-mode Boost / Buck reconfigurable energy recovery circuit according to claim 1, characterized in that: When the thermoelectric generator provides a certain power, that is, the load voltage V LOAD In the target range [V L ,V H ], it is configured as a Boost converter and works in supply mode; When the power P provided by the thermoelectric generator IN >P OUT , that is, the load voltage V LOAD >V H , the operating mode is configured as storage mode, and the Boost converter supplies power to the storage capacitor C store Charging, load voltage V LOAD <V M Then set it to supply mode; When the power P provided by the thermoelectric generator IN <P OUT , that is, the load voltage V LOAD <V L After that, it is configured as a Buck converter. If V OTEG <V OL In recovery mode, only the storage capacitor C is used. store is the load voltage V LOAD Power supply, if the open circuit voltage of the thermoelectric generator is V OTEG >V OL It works in the extraction mode, and the thermoelectric generator TEG and the storage capacitor are combined to supply power to the load.

3. The four-mode Boost / Buck reconfigurable energy recovery circuit according to claim 1, characterized in that: The maximum power point tracking circuit MPPT realizes that the output voltage of the thermoelectric generator is always half of the open circuit voltage of the thermoelectric generator. The equivalent resistance R EQ The equivalent internal resistance R of the thermoelectric generator T Keep equal, that is, the power output of the thermoelectric generator meets the following conditions: Where V OTEG is the open circuit voltage of the thermoelectric generator, R T is the equivalent output resistance of the thermoelectric generator; The zero current detection circuit ZCS input is connected to the load voltage V LOAD , storage voltage V STORE The voltage on both sides of the inductor is used to detect whether the inductor current is reversed.

4. The four-mode Boost / Buck reconfigurable energy recovery circuit according to claim 1 or 2, characterized in that: The zero current detection circuit ZCS monitors the relationship between the voltage on one side of the inductor and the target voltage in real time in each cycle according to the system clock generated by the OSC module to adjust the discharge time of the power inductor and ultimately control the duty cycle of the converter to prevent the inductor current from reversing; One end of the first comparator is connected to the load voltage and the off-chip reference voltage, and outputs a control buck-boost mode switching signal; one end of the second comparator is connected to the load voltage and the second off-chip reference voltage, and one end of the third comparator is connected to the load voltage and the third off-chip reference voltage, and the outputs are respectively connected to the reset end and the set end of the RS trigger; one end of the fourth comparator is connected to the open-circuit voltage of the thermoelectric power generation chip and compared with the fourth off-chip reference voltage, and outputs the control signal of the extraction and circulation mode under the buck mode; The mode control module generates a clock signal for driving the gate of the switch tube according to the mode control signal.

5. The four-mode Boost / Buck reconfigurable energy recovery circuit according to claim 1, characterized in that: The mode control module includes a circulation mode module, an extraction mode module, a supply mode module and a storage mode module; The four operating modes include supply mode, where the energy source supplies power to the load voltage and operates in Boost mode; The storage mode energy source supplies power to the load voltage and works in Boost mode; The storage capacitor in the extraction mode supplies power to the load voltage and works in Buck mode; The cycle mode thermoelectric generator chips are stacked under the storage capacitor to supply power to the load voltage and work in Buck mode.

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