Maximum power tracking algorithm circuit for piezoelectric micro energy harvesting power management

Abstract

The application discloses a maximum power tracking algorithm circuit for piezoelectric micro energy collection power management, which converts AC energy output by a piezoelectric power supply into DC energy through setting a rectifier; a peak value detection circuit is arranged to detect a peak point voltage, i.e. an open circuit voltage of the piezoelectric power supply, so that an MPPT control circuit can find a point to be tracked, i.e. a maximum power point; the MPPT control circuit adjusts a working frequency of a DC-DC converter according to the maximum power point, so that an equivalent impedance of the DC-DC converter is equal to an equivalent impedance of the piezoelectric power supply. Thus, the circuit realizes dynamic matching of the equivalent impedance of the DC-DC converter and the internal resistance of the piezoelectric power supply, realizes maximum power tracking, and guarantees that piezoelectric energy can be efficiently obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power management of piezoelectric vibration energy collection, and particularly relates to a maximum power tracking algorithm circuit for piezoelectric micro energy collection power management. BACKGROUND

[0002] With the advancement of power grid digitalization construction, the application scale of power sensors will increase sharply, and the traditional battery power supply method will cause great pressure on the operation and maintenance of power sensors, and there is also a problem of operation and maintenance in the high-voltage environment of sensors. Therefore, through environmental energy collection, realizing self-power supply of power sensors has become a hot research direction.

[0003] In the environmental energy collection technology, vibration energy collection based on piezoelectric materials is a main direction. For piezoelectric energy, since the output of the piezoelectric energy source has a maximum power point, how to make the energy source continuously output maximum power is a research hotspot of piezoelectric energy collection in recent years. However, the prior art still has deficiencies in the rapid response ability under the condition of adapting to the dynamic change of the energy source, thereby losing part of the energy and affecting the energy utilization efficiency. SUMMARY

[0004] Therefore, the embodiments of the present application provide a maximum power tracking algorithm circuit for piezoelectric micro energy collection power management, so as to solve the technical problem that the collection of the piezoelectric energy source cannot track the maximum power point in the prior art, and affect the energy utilization efficiency.

[0005] The technical scheme provided by the embodiments of the present application is as follows:

[0006] The first aspect of the embodiment of the present application provides a maximum power tracking algorithm circuit for piezoelectric micro energy collection power management, comprising a piezoelectric power source, a rectifier, a peak detection circuit, a DC-DC converter, an MPPT control circuit and an energy storage circuit; the input end of the rectifier is connected to the output end of the piezoelectric power source, the first output end of the rectifier is connected to the input end of the peak detection circuit, the second output end of the rectifier is connected to the first input end of the DC-DC converter, the output end of the peak detection circuit is connected to the first input end of the MPPT control circuit, the output end of the MPPT control circuit is connected to the second input end of the DC-DC converter, and the output end of the DC-DC converter is connected to the energy storage circuit; the peak detection circuit is used to detect the open circuit voltage of the piezoelectric power source when the connection between the rectifier and the DC-DC converter is disconnected; after the connection between the rectifier and the DC-DC converter, the rectifier is used to convert the alternating current output by the piezoelectric power source into direct current, the MPPT control circuit generates a voltage control signal according to the size of the direct current and the open circuit voltage of the piezoelectric power source, the DC-DC converter adjusts the equivalent impedance of the DC-DC converter according to the voltage control signal and generates a corresponding output voltage, and after the adjustment, the equivalent impedance of the DC-DC converter is equal to the internal resistance of the piezoelectric power source, and the energy storage circuit receives the output voltage of the DC-DC converter for storage and collection.

[0007] Optionally, the MPPT control circuit comprises a controller and a tracking circuit; the controller determines the current state as deviating from the maximum power point or being near the maximum power point according to the size of the direct current and the open circuit voltage of the piezoelectric power source and a preset period; when deviating from the maximum power point, the controller controls the tracking circuit to generate a voltage control signal in a binary variable step size manner, and when being near the maximum power point, the controller controls the tracking circuit to generate a voltage control signal in a fixed step size manner.

[0008] Optionally, the tracking circuit comprises a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first capacitor, a second capacitor, a third capacitor, a first current source and a second current source; one end of the first switch is connected to one end of the second switch and one end of the first capacitor, the other end of the second switch is connected to one end of the third switch, one end of the fourth switch, one end of the fifth switch, one end of the second capacitor and the second input end of the DC-DC converter, the other end of the first switch is connected to the output end of the peak detection circuit and one end of the first current source, the other end of the first current source is connected to the other end of the third switch, the other end of the fourth switch is connected to one end of the second current source, the other end of the fifth switch is connected to one end of the third capacitor, the sixth switch is connected across the third capacitor, the other end of the first capacitor is connected to the other end of the second current source, the other end of the third capacitor and the other end of the second capacitor and grounded.

[0009] Optionally, when the tracking circuit generates the voltage control signal in a binary variable step length manner, the first switch, the second switch, the fifth switch, the sixth switch, the first capacitor, the second capacitor and the third capacitor work.

[0010] Optionally, when the tracking circuit generates the voltage control signal in a fixed step length manner, the third switch, the fourth switch, the second capacitor, the first current source and the second current source work.

[0011] Optionally, the rectifier comprises a first PMOS transistor, a second PMOS transistor, a first NMOS transistor, a second NMOS transistor, a first diode, a second diode, a first comparator and a second comparator; the drain of the first PMOS transistor is connected to the gate of the second PMOS transistor, the drain of the first NMOS transistor, the negative electrode of the first diode, the negative input end of the first comparator and one end of the output end of the voltage source, the drain of the second PMOS transistor is connected to the gate of the first PMOS transistor, the drain of the second NMOS transistor, the negative electrode of the second diode, the negative input end of the second comparator and the other end of the output end of the voltage source, the source of the first PMOS transistor is connected to the source of the second PMOS transistor, the input end of the peak detection circuit and the first input end of the DC-DC converter, the source of the first NMOS transistor is connected to the source of the second NMOS transistor, the positive electrode of the first diode, the positive electrode of the second diode, the positive input end of the first comparator and the positive input end of the second comparator are all connected to ground.

[0012] Optionally, the peak detection circuit comprises a fourth capacitor, a third PMOS tube, a fourth PMOS tube, a fifth PMOS tube, a sixth PMOS tube, a third NMOS tube, a fourth NMOS tube, a fifth NMOS tube, a sixth NMOS tube, a seventh NMOS tube, an eighth NMOS tube, a ninth NMOS tube, and a single pulse generation circuit; one end of the fourth capacitor is connected to the first output end of the rectifier, the other end of the fourth capacitor is connected to the drain of the third NMOS tube, the drain and gate of the fourth NMOS tube, and the gate of the fifth NMOS tube, the drain of the fifth NMOS tube is connected to the drain and gate of the third PMOS tube, the gate of the fourth PMOS tube, and the gate of the fifth PMOS tube, the drain of the third PMOS tube is connected to the drain of the sixth NMOS tube, the gate of the sixth NMOS tube is connected to the drain of the fifth PMOS tube, the gate and drain of the seventh NMOS tube, the gate of the eighth NMOS tube, the gate of the ninth NMOS tube, and the gate of the sixth PMOS tube, the drain of the sixth PMOS tube is connected to the drain of the ninth NMOS tube and the input end of the single pulse generation circuit, the output end of the single pulse generation circuit is connected to the input end of the MPPT control circuit and the gate of the third NMOS tube, the drain of the eighth NMOS tube receives a bias current, the source of the third PMOS tube is connected to the source of the fourth PMOS tube, the source of the fifth PMOS tube, and the source of the sixth PMOS tube, and the source of the third NMOS tube is connected to the source of the fourth NMOS tube, the source of the fifth NMOS tube, the source of the sixth NMOS tube, the source of the seventh NMOS tube, the source of the eighth NMOS tube, and the source of the ninth NMOS tube, all of which are connected to ground.

[0013] Optionally, the DC-DC converter comprises a seventh PMOS tube, an eighth PMOS tube, a tenth NMOS tube, an eleventh NMOS tube, an inductor, a hysteretic comparator, a ring oscillator, a PFM controller, a driving stage, a fifth capacitor, a first resistor, a second resistor and a third resistor; the source of the seventh PMOS tube is connected to the second output end of the rectifier, the drain of the seventh PMOS tube is connected to one end of the inductor and the drain of the tenth NMOS tube, the other end of the inductor is connected to the drain of the eighth PMOS tube and the drain of the eleventh NMOS tube, the source of the eighth PMOS tube is connected to one end of the fifth capacitor, one end of the first resistor and one end of the second resistor, the other end of the fifth capacitor is connected to the other end of the first resistor, one end of the third resistor and the ground, the other end of the second resistor is connected to the other end of the third resistor and the negative input end of the hysteretic comparator, the output end of the hysteretic comparator is connected to the first input end of the ring oscillator, the second input end of the ring oscillator is connected to the output end of the MPPT control circuit, the output end of the ring oscillator is connected to the input end of the PFM controller, the output end of the PFM controller is connected to the input end of the driving stage, and the output end of the driving stage is connected to the gates of the seventh PMOS tube, the eighth PMOS tube, the tenth NMOS tube and the eleventh NMOS tube.

[0014] Optionally, the maximum power tracking algorithm circuit for piezoelectric micro energy harvesting power management further comprises a sixth capacitor, a seventh capacitor and a seventh switch; the seventh switch is connected between the second output end of the rectifier and the first input end of the DC-DC converter, one end of the sixth capacitor is connected to one end of the seventh switch and the second output end of the rectifier, one end of the seventh capacitor is connected to the first input end of the DC-DC converter, and the other end of the sixth capacitor and the other end of the seventh capacitor are grounded.

[0015] Optionally, the DC-DC converter is further configured to receive the direct current output by the rectifier, compare the direct current with a reference voltage signal, and stop outputting the voltage when the direct current is greater than the reference voltage signal.

[0016] The technical scheme has the following advantages:

[0017] The maximum power tracking algorithm circuit for piezoelectric micro energy collection power management provided by the embodiment of the present application converts the alternating current energy output by the piezoelectric power supply into direct current energy through the rectifier; the peak value detection circuit can detect the peak point voltage, i.e. the open circuit voltage of the piezoelectric power supply, so that the MPPT control circuit can find the point to be tracked, i.e. the maximum power point, and the MPPT control circuit adjusts the working frequency of the DC-DC converter according to the maximum power point, so that the equivalent impedance of the DC-DC converter is equal to the equivalent impedance of the piezoelectric power supply. Thus, the dynamic matching of the equivalent impedance of the DC-DC converter and the internal resistance of the piezoelectric power supply is realized through the circuit, the maximum power tracking is realized, and the piezoelectric energy can be efficiently obtained.

[0018] The maximum power tracking algorithm circuit for piezoelectric micro energy collection power management provided by the embodiment of the present application can be designed by using the standard 0.18 μm CMOS process, and does not need special process and equipment, so the cost is reduced. The rectifier converts the AC energy of the piezoelectric power supply into DC energy, the rectifier can be self-started, and at the same time, the system efficiency in the energy transmission stage is not affected. The peak voltage detection circuit can detect the open circuit voltage of the piezoelectric power supply, the MPPT control logic can control and adjust the working frequency of the DC-DC converter, so that the equivalent input impedance of the DC-DC converter is equal to the internal resistance of the piezoelectric power supply, and the tracking method of variable step size plus fixed step size can quickly and accurately track the maximum power point. The tracking accuracy of the maximum power point can be maintained above 90%, and the maximum energy conversion efficiency is 80%. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0020] Figure 1 The structural block diagram of the maximum power tracking algorithm circuit for piezoelectric micro energy collection power management in the embodiment of the present application is shown in the figure;

[0021] Figure 2 The structural schematic diagram of the rectifier in the embodiment of the present application is shown in the figure;

[0022] Figure 3 The structural schematic diagram of the peak value detection circuit in the embodiment of the present application is shown in the figure;

[0023] Figure 4 The control timing diagram of the controller in the embodiment of the present application is shown in the figure;

[0024] Figure 5A structure schematic diagram of the MPPT control circuit in the embodiment of the present application is shown in Fig. 1.

[0025] Figure 6 A control flow schematic diagram of the MPPT control circuit in the embodiment of the present application is shown in Fig. 2.

[0026] Figure 7 A structure schematic diagram of the DC-DC converter in the embodiment of the present application is shown in Fig. 3. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0028] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0029] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the internal communication of two elements, it can be wireless connection, or wired connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0030] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0031] The embodiment of the present application provides a maximum power tracking algorithm circuit for piezoelectric micro energy collection power management, which comprises a piezoelectric power source 6, a rectifier 1, a peak detection circuit 2, a DC-DC converter 3, an MPPT control circuit 4 and an energy storage circuit 5; the input end of the rectifier 1 is connected with the output end of the piezoelectric power source 6, the first output end of the rectifier 1 is connected with the input end of the peak detection circuit 2, the second output end of the rectifier 1 is connected with the first input end of the DC-DC converter 3, the output end of the peak detection circuit 2 is connected with the first input end of the MPPT control circuit 4, the output end of the MPPT control circuit 4 is connected with the second input end of the DC-DC converter 3, and the output end of the DC-DC converter 3 is connected with the energy storage circuit 5; the peak detection circuit 2 is used for detecting the open circuit voltage of the piezoelectric power source 6 when the connection between the rectifier 1 and the DC-DC converter 3 is disconnected; after the connection between the rectifier 1 and the DC-DC converter 3, the rectifier 1 is used for converting the alternating current output by the piezoelectric power source 6 into direct current, the MPPT control circuit 4 generates a voltage control signal according to the size of the direct current and the open circuit voltage of the piezoelectric power source 6, the DC-DC converter 3 adjusts the equivalent impedance of the DC-DC converter 3 and generates a corresponding output voltage according to the voltage control signal, after the adjustment, the equivalent impedance of the DC-DC converter 3 is equal to the internal resistance of the piezoelectric power source 6, and the energy storage circuit 5 receives the output voltage of the DC-DC converter 3 for storage collection. The energy storage circuit 5 is a battery or a battery with a capacity greater than a threshold value.

[0032] The maximum power tracking algorithm circuit for piezoelectric micro energy collection power management provided by the embodiment of the present application converts the alternating current energy output by the piezoelectric power source into direct current energy through the rectifier; the peak detection circuit can detect the peak voltage, so that the MPPT control circuit can find the point to be tracked, that is, the maximum power point, the MPPT control circuit adjusts the working frequency of the DC-DC converter according to the maximum power point, so that the equivalent impedance of the DC-DC converter is equal to the equivalent impedance of the piezoelectric power source. Therefore, the dynamic matching of the equivalent impedance of the DC-DC converter and the internal resistance of the piezoelectric power source is realized through the circuit, the maximum power tracking is realized, and the piezoelectric energy can be efficiently obtained.

[0033] In an embodiment, as shown in Figure 2 the rectifier comprises a first PMOS tube M P1 , a second PMOS tube M P2 , a first NMOS tube M N1 , a second NMOS tube M N2 , a first diode D1, a second diode D2, a first comparator CMP1 and a second comparator CMP2; the first PMOS tube M P1The drain of the second PMOS transistor M P2 The gate of the first NMOS transistor M N1 The drain of the first diode D1, the negative input terminal of the first comparator CMP1, and one end of the output terminal of the voltage power supply are connected together. The second PMOS transistor M P2 The drain of the first PMOS transistor M P1 The gate of the second NMOS transistor M N2 The drain of the first PMOS transistor, the cathode of the second diode D2, the negative input terminal of the second comparator CMP2, and the other end of the output terminal of the voltage power supply are connected together. P1 The source of the second PMOS transistor M P2 The source of the first NMOS transistor is connected to the input terminal of the peak detection circuit and the first input terminal of the DC-DC converter. N1 The source of the second NMOS transistor M N2 The source of the first diode, the positive terminal of the first diode D1, the positive terminal of the second diode D2, the positive input terminal of the first comparator CMP1, and the positive input terminal of the second comparator CMP2 are all connected to ground.

[0034] In one implementation, such as Figure 1 and Figure 2 As shown, the maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management also includes: a sixth capacitor C. S and the seventh capacitor C R The sixth capacitor C S One end of the capacitor is connected to the second output terminal of the rectifier, and the seventh capacitor C R One end of the capacitor is connected to the first input terminal of the DC-DC converter, and the sixth capacitor C S The other end and the seventh capacitor C R The other end is grounded. Specifically, the sixth capacitor C S and the seventh capacitor C R Together they form the filter capacitor C in the rectifier. REC Used to reduce the rectifier output voltage V REC The ripples.

[0035] Specifically, since the operating voltage of the two comparators in the rectifier is determined by the rectifier output voltage V... REC Control, and simultaneously due to the setting of the sixth and seventh capacitors, V RECThere is a large capacitor on the rectifier. During the initial startup phase, due to the presence of this capacitor, the voltage rises slowly, resulting in a low voltage period. During this time, the operating voltage of the two comparators is low, and they cannot function properly. At this point, the body diodes of the two NMOS transistors and the two PMOS transistors form a passive cross-coupled rectifier. The power loss of the diodes reduces the rectifier's efficiency. However, the DC-DC converter's operating voltage can be preset to be higher than the operating voltages of the two comparators in the rectifier. When the two comparators are not operating, the DC-DC converter does not start working, and there is no energy transfer in the circuit. The rectifier's efficiency does not affect the overall energy transfer efficiency. This design eliminates the need for additional auxiliary circuitry, allowing the rectifier to self-start without affecting the system efficiency during the energy transfer phase.

[0036] In one implementation, such as Figure 3 As shown, the peak detection circuit includes: a fourth capacitor C PD The circuit consists of a third PMOS transistor MP3, a fourth PMOS transistor MP4, a fifth PMOS transistor MP5, a sixth PMOS transistor MP6, a third NMOS transistor MN3, a fourth NMOS transistor MN4, a fifth NMOS transistor MN5, a sixth NMOS transistor MN6, a seventh NMOS transistor MN7, an eighth NMOS transistor MN8, a ninth NMOS transistor MN9, and a single-pulse generation circuit OSP; the fourth capacitor C. PD One end of the fourth capacitor C is connected to the first output terminal of the rectifier. PDThe other end of the fourth NMOS transistor MN4 is connected with the drain of the third NMOS transistor MN3, the drain and the gate of the fourth NMOS transistor MN4, and the gate of the fifth NMOS transistor MN5, the drain of the fifth NMOS transistor MN5 is connected with the drain and the gate of the third PMOS transistor MP3, the gate of the fourth PMOS transistor MP4, and the gate of the fifth PMOS transistor MP5, the drain of the third PMOS transistor MP3 is connected with the drain of the sixth NMOS transistor MN6, the gate of the sixth NMOS transistor MN6 is connected with the drain of the fifth PMOS transistor MP5, the gate and the drain of the seventh NMOS transistor MN7, the gate of the eighth NMOS transistor MN8, the gate of the ninth NMOS transistor MN9, and the gate of the sixth PMOS transistor MP6, the drain of the sixth PMOS transistor MP6 is connected with the drain of the ninth NMOS transistor MN9 and the input of the single pulse generating circuit OSP, the output of the single pulse generating circuit OSP is connected with the input of the MPPT control circuit and the gate of the third NMOS transistor MN3, the drain of the eighth NMOS transistor MN8 receives a bias current, the source of the third PMOS transistor MP3 is connected with the source of the fourth PMOS transistor MP4, the source of the fifth PMOS transistor MP5, and the source of the sixth PMOS transistor MP6, the source of the third NMOS transistor MN3 is connected with the source of the fourth NMOS transistor MN4, the source of the fifth NMOS transistor MN5, the source of the sixth NMOS transistor MN6, the source of the seventh NMOS transistor MN7, the source of the eighth NMOS transistor MN8, and the source of the ninth NMOS transistor MN9, all of which are connected to the ground.

[0037] Specifically, when the peak detection circuit detects the open circuit voltage, the current and the voltage differential relationship of the capacitor is used for detection, when the voltage across the fourth capacitor reaches the peak, the rate of change of the voltage is 0, at this time the current flowing through the fourth capacitor is 0, the current flowing through the fourth capacitor is mirrored to the fifth NMOS transistor through the fourth NMOS transistor, and then mirrored to the fourth PMOS transistor through the third PMOS transistor, a fixed current I BIAS After being mirrored through the eighth NMOS transistor and the sixth NMOS transistor, it is compared with the current flowing through the fourth capacitor, and the comparison result is output. The comparison result generates a short pulse through the single pulse generating circuit, and the fourth capacitor C PD The charge is released, and the next detection begins.

[0038] In the peak detection circuit, when the voltage across the fourth capacitor reaches the peak, it means that the open circuit voltage of the piezoelectric power supply is detected, at this time the rate of change of the voltage in the peak detection circuit is minimum, and the sixth PMOS transistor and the ninth NMOS transistor constitute an inverting amplifier circuit, when the current flowing through the fourth capacitor is less than the current I BIASAt this time, the comparison result of the two is realized by the signal flip through the inverting amplifier circuit.

[0039] As shown in Figure 1 The piezoelectric micro energy collection power management maximum power tracking algorithm circuit further comprises a seventh switch S1, the seventh switch S1 is connected between the second output end of the rectifier and the first input end of the DC-DC converter, and one end of the sixth capacitor is connected with one end of the seventh switch S1 and the second output end of the rectifier. Specifically, the seventh switch S1 is controlled by the MPPT control circuit, when it is needed to detect the open circuit voltage of the piezoelectric power supply, the seventh switch S1 is opened, that is, the connection between the rectifier and the DC-DC converter is disconnected; when the maximum power tracking is performed, the seventh switch S1 is closed. In addition, it should be noted that because the load capacitor is required to be small during the open circuit voltage detection, the sixth capacitor C S is much smaller than the seventh capacitor C R , and the sixth capacitor C S is much smaller than the eighth capacitor C P in the piezoelectric power supply, so as to reduce the error of the open circuit voltage.

[0040] In an embodiment, the MPPT control circuit comprises a controller and a tracking circuit; the controller determines the current state as deviating from the maximum power point or being near the maximum power point according to the size of the direct current and the open circuit voltage of the piezoelectric power supply and a preset period; when deviating from the maximum power point, the controller controls the tracking circuit to generate a voltage control signal in a binary variable step size manner, and when being near the maximum power point, the controller controls the tracking circuit to generate a voltage control signal in a fixed step size manner.

[0041] Specifically, when the maximum power tracking is performed, it is needed to measure the deviation of the working point of the maximum tracking algorithm circuit from the maximum power point, so as to realize the dynamic tracking of the maximum power point. Therefore, the input voltage V IN of the DC-DC converter is compared with half of the open circuit voltage V OC / 2 of the piezoelectric power supply (when the equivalent impedance of the DC-DC converter is equal to the internal resistance of the piezoelectric power supply, the input voltage V IN of the DC-DC converter is equal to half of the open circuit voltage V OC / 2 of the piezoelectric power supply, which can ensure the maximum power tracking), if the input voltage V IN of the DC-DC converter is less than half of the open circuit voltage V OC / 2 of the piezoelectric power supply, it indicates that the equivalent impedance of the DC-DC converter is greater than the internal resistance of the piezoelectric power supply, and thus the working frequency of the DC-DC converter needs to be increased, if the input voltage V IN of the DC-DC converter is greater than half of the open circuit voltage V OC / 2 indicates that the equivalent impedance of the DC-DC converter is less than the internal resistance of the power supply, thus requiring a reduction in the operating frequency of the DC-DC converter. It should be noted that the input voltage V of the DC-DC converter... IN Data can be obtained through data interaction between the controller and the DC-DC converter.

[0042] When generating voltage control signals to regulate the DC-DC converter, regulation can be performed once for each received pulse signal; that is, a voltage comparison can be performed once for each received pulse signal. For example... Figure 4 The diagram shown is the control timing diagram of the controller, where IS represents the clock signal; CMP_P high level indicates V IN <V OC / 2, CMP_N high level indicates V IN >V OC / 2. If CMP_P appears high twice or more consecutively, then UP_L is high; if CMP_N appears high twice or more consecutively, then DW_L is high. When UP_L or DW_L is high, it is considered that the current operating state deviates from the maximum power point, and a binary variable step size method is needed to re-track the maximum power point. When CMP_P and CMP_N alternate in adjacent cycles, the maximum power tracking algorithm circuit operates near the maximum power point, and a fixed step size method is needed to track it to maintain the maximum power tracking accuracy.

[0043] In one implementation, such as Figure 5 As shown, the tracking circuit includes: a first switch S IS Second switch S INS Third switch S INS_S Fourth switch S DEC_S Fifth switch S DEC Sixth switch S IIS First capacitor C V Second capacitor C I Third capacitor C D First current source I BIAS1 and the second current source I BIAS2 The first switch S IS One end is connected to the second switch S INS one end and the first capacitor C V One end, the second switch S INS The other end is connected to the third switch S INS_S One end, the fourth switch S DEC_S One end, the fifth switch S DEC One end, the second capacitor C I One end of the first switch S and the second input terminal of the DC-DC converter.IS The other end is connected to the output terminal of the peak detection circuit and the first current source I. BIAS1 At one end, the first current source I BIAS1 The other end is connected to the third switch S INS_S At the other end, the fourth switch S DEC_S The other end is connected to the second current source I BIAS2 At one end, the fifth switch S DEC The other end is connected to the third capacitor C D One end of the sixth switch S IIS Connected to the third capacitor C D At both ends, the first capacitor C V The other end is connected to the second current source I BIAS2 The other end, the third capacitor C D The other end and the second capacitor C I The other end is grounded.

[0044] Specifically, when the tracking circuit generates a voltage control signal in a binary variable step size manner, the first switch, the second switch, the fifth switch, the sixth switch, the first capacitor, the second capacitor, and the third capacitor operate. When the tracking circuit generates a voltage control signal in a fixed step size manner, the third switch, the fourth switch, the second capacitor, the first current source, and the second current source operate.

[0045] Specifically, the binary variable step size control method is as follows: Initial voltage control signal V CTRL =0, first switch S IS and the sixth switch S IIS Closed, first capacitor C V Charge to the operating voltage V of the MPPT control circuit DD V DD The DC voltage output by the rectifier is V REC The third capacitor C D Discharge to 0, first switch S IS Disconnect; if V needs to be increased CTRL Second switch S INS Closed, first capacitor C V With the second capacitor C I Charge sharing, V CTRL =V DD / 2, Second switch S INS Disconnect; first capacitor C V Recharge to V DD The third capacitor C D Discharge to 0; if further increase V is required CTRL, the second switch S INS is closed, V CTRL = 3V DD / 4; if V CTRL needs to be reduced, the fifth switch S DEC is closed, the sixth switch S IIS is opened, the first capacitor C V and the third capacitor C D share the charge, V CTRL = V DD / 4. In this way, when the first switch S IS and the sixth switch S IIS are closed, the first capacitor C V is charged to V DD , the third capacitor C D is discharged to zero, then the first switch S IS is opened, when V CTRL needs to be increased, the second switch S INS is closed, the first capacitor C V and the second capacitor C I share the charge, V CTRL is increased, when V CTRL needs to be reduced, the fifth switch S DEC is closed, V CTRL is reduced to half of the original. Through the charge sharing of the first capacitor C V , the second capacitor C I , and the third capacitor C D , the control voltage control signal V CTRL is forced to approach the maximum power point in a binary search manner.

[0046] The fixed-step tracking is controlled by two bias current sources IBIAS1 and IBIAS2, after switching to the fixed-step tracking, when V CTRL needs to be increased, the third switch S INS_S is closed for a fixed time, the first current source I BIAS1 charges the second capacitor C I , since the charging time is fixed, the rising amplitude of V CTRL is fixed; when V CTRL needs to be reduced, the fourth switch S DEC_S is closed for a fixed time, the second current source I BIAS2 discharges the second capacitor C I , since the discharging time is fixed, the reduction amplitude of V CTRL is fixed.

[0047] As Figure 3 , Figure 4 and Figure 6As shown, the control of the voltage control signal is implemented through the following process: First, it should be noted that EN=1 indicates that the circuit needs to re-acquire V. OC The rate of change of ambient energy is lower than the operating frequency of the circuit, therefore it is not necessary to refresh V with every clock cycle. OC At this time, the circuit refreshes V every 8 DC-DC duty cycles. OC However, after refreshing the maximum power point position once, V is adjusted once in each DC-DC cycle. CTRL Maintain tracking accuracy at maximum power.

[0048] After the open-circuit voltage is collected, compare V IN and V OC / 2, if V IN <V OC If / 2 and UP_L is high, then V needs to be increased using a binary variable step size. CTRL At this time, INC_L is high; if V IN <V OC If / 2, and UP_L is low, then V needs to be increased in fixed steps. CTRL At this time, INC_S is high; if V IN >V OC If / 2, and DW_L is high, then V needs to be reduced using a binary variable step size method. CTRL At this time, DEC_L is high; if V IN >V OC If / 2, and DW_L is low, then V needs to be decreased in fixed steps. CTRL At this time, DEC_S is at a high level.

[0049] In one implementation, such as Figure 7 As shown, the DC-DC converter includes: a seventh PMOS transistor M P7 The eighth PMOS transistor M P8 The tenth NMOS transistor M N10 11th NMOS transistor M N11 Inductor L, Hysteresis Comparator CMP, Ring Oscillator, PFM Controller, Driver Stage, Fifth Capacitor C L First resistor R L The second resistor R1 and the third resistor R2; the seventh PMOS transistor M P7 The source of the seventh PMOS transistor M is connected to the second output terminal of the rectifier. P7 The drain of the inductor L and one end of the tenth NMOS transistor M N10 The drain of the inductor L is connected to the drain of the inductor L, and the other end of the inductor L is connected to the eighth PMOS transistor M. P8the drain of the eleventh NMOS transistor M N11 the drain of the eighth PMOS transistor M P8 the source of the fifth capacitor C L one end of the first resistor R L one end of the second resistor R1, and one end of the fifth capacitor C L the other end of the fifth capacitor C L the other end of the first resistor R P7 one end of the third resistor R2, and the negative input terminal of the hysteresis comparator CMP, the other end of the second resistor R1, the other end of the third resistor R2, and the output terminal of the hysteresis comparator CMP are connected, the output terminal of the hysteresis comparator CMP is connected to the first input terminal of the ring oscillator Ring Oscillator, the second input terminal of the ring oscillator Ring Oscillator is connected to the output terminal of the MPPT control circuit, the output terminal of the ring oscillator Ring Oscillator is connected to the input terminal of the PFM controller, the output terminal of the PFM (Pulse Frequency Modulation) controller is connected to the input terminal of the driver stage Driver Stage, and the output terminal of the driver stage Driver Stage is connected to the gates of the seventh PMOS transistor M P7 , the eighth PMOS transistor M P8 , the tenth NMOS transistor M N10 , and the eleventh NMOS transistor M N11 .

[0050] Specifically, the positive input terminal of the hysteresis comparator receives an externally input reference voltage signal V REF , the hysteresis comparator compares the reference voltage signal V REF with the received input voltage V IN , controls the ring oscillator to work when the input voltage V IN is less than the reference voltage signal V REF , and controls the ring oscillator not to work when the input voltage V IN is greater than the reference voltage signal V REF ; thus, the maximum voltage value output by the maximum power tracking algorithm circuit can be controlled by setting the reference voltage signal V REF , and the load can be prevented from being damaged due to overshoot.

[0051] In addition, the second input terminal of the ring oscillator is connected to the output terminal of the MPPT control circuit to receive a voltage control signal V CTRLThe frequency of the converter is adjusted according to the magnitude of the voltage control signal, thereby changing the gate control signals input to the seventh, eighth, tenth, and eleventh NMOS transistors. The seventh, eighth, tenth, and eleventh NMOS transistors are connected to the inductor, controlling the charging and discharging of the inductor. Thus, the equivalent impedance of the DC-DC converter is adjusted by changing the magnitude of the input voltage control signal.

[0052] In one embodiment, the maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management operates as follows:

[0053] 1) Start-up phase: When the maximum power point tracking algorithm circuit is connected to the voltage power supply, the rectifier starts to work, converting AC energy into DC energy. At this time, other circuits in the maximum power point tracking algorithm circuit do not work until the output voltage of the rectifier reaches the start-up voltage.

[0054] 2) Open-circuit voltage detection stage: At this time, the downstream DC-DC converter is disconnected from the rectifier, and the peak detection circuit starts to work to detect the open-circuit voltage of the current under-voltage power supply output.

[0055] 3) Maximum Power Point Tracking (MPPT) Stage: When the peak detection circuit detects the open-circuit voltage of the power supply, the DC-DC converter and MPPT control circuit start to work. By changing the operating frequency of the DC-DC converter, the equivalent impedance is changed. When the internal resistance of the power supply is equal to the equivalent impedance of the DC-DC converter, the power supply outputs the maximum power.

[0056] The maximum power point tracking (MPPT) algorithm circuit for piezoelectric micro-energy harvesting power management described in this invention achieves MPPT by dynamically matching the equivalent impedance and internal resistance of a DC-DC converter in PFM control mode. Simultaneously, to quickly track a new maximum power point and stabilize near it, ensuring efficient piezoelectric energy harvesting, a variable-step-size plus fixed-step-size perturbation MPPT algorithm is used for DC-DC converter frequency control. When the DC-DC converter is far from the maximum power point or a new maximum power point appears, a larger adjustment step size is initially used to quickly approach the maximum power point. After reaching the vicinity of the maximum power point, a smaller step size is switched to achieve higher tracking accuracy. Assuming the operating frequency f of the DC-DC converter... BB and control voltage V CTRL To achieve a linear relationship, firstly, in order to quickly track the maximum power point, the system employs a binary search method, i.e., frequency-controlled voltage V. CTRL The adjustment method is: when V CTRL When it increases positively, it follows V DD / 2,3V DD / 4.7V DD(2n-1)V DD / 2n, where n is a non-zero positive integer; when V CTRL is decreased, the control voltage is changed in accordance with the law of (2n-1)V DD / 2n, (2n-1)V DD / 2n+1, (2n-1)V DD / 2n+1. Regardless of increase or decrease, the change of the control voltage is in a binary manner, thus this method is also called binary search method. When near the maximum power point, switch to the fixed-step tracking method. The detection method is to compare V IN and V OC / 2 by using a clock-controlled dynamic comparator, if the comparator jumps positive and negative in several adjacent clock periods, it indicates that the maximum power point is approached, and the fixed-step perturbation tracking method is started. Thus the tracking speed of the maximum power can be significantly improved while ensuring high tracking accuracy. According to the design, when using the fixed-step method to perturb near the maximum power point, the tracking accuracy can be ensured to be 91%.

[0057] The maximum power tracking algorithm circuit for piezoelectric micro energy collection power management provided by the embodiment of the application can be designed by using standard 0.18 μm CMOS process, and does not need special process and equipment, so that the cost is reduced. The rectifier converts the AC energy of the piezoelectric power into DC energy, the rectifier can be self-started, and meanwhile does not affect the system efficiency in the energy transmission stage. The peak voltage detection circuit can detect the open-circuit voltage of the piezoelectric power, the MPPT control logic can control the working frequency of the adjusting DC-DC converter, so that the equivalent input impedance of the DC-DC converter is equal to the internal resistance of the piezoelectric power, and the tracking method of variable step length plus fixed step length can quickly and accurately track the maximum power point. The tracking accuracy of the maximum power point can be kept above 90%, and the maximum energy conversion efficiency is 80%.

[0058] Although the example embodiments and their advantages have been described in detail, those skilled in the art can make various changes, replacements and modifications to the embodiments without departing from the spirit of the application and the protection scope defined by the appended claims, and such modifications and variations fall within the scope defined by the appended claims. For other examples, those skilled in the art should easily understand that the order of the process steps can be changed while keeping within the protection scope of the application.

[0059] Moreover, the scope of the application is not intended to be limited to particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. Accordingly, the application is not to be limited to particular embodiments described in the specification, as such can vary. The application is also not to be limited to applications specifically recited in the specification and / or claims.

Claims

1. A maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management, characterized in that, include: Voltage power supply, rectifier, peak detection circuit, DC-DC converter, MPPT control circuit and energy storage circuit; The input terminal of the rectifier is connected to the output terminal of the voltage power supply, the first output terminal of the rectifier is connected to the input terminal of the peak detection circuit, the second output terminal of the rectifier is connected to the first input terminal of the DC-DC converter, the output terminal of the peak detection circuit is connected to the first input terminal of the MPPT control circuit, the output terminal of the MPPT control circuit is connected to the second input terminal of the DC-DC converter, and the output terminal of the DC-DC converter is connected to the energy storage circuit. The peak detection circuit is used to detect the open-circuit voltage of the power supply when the connection between the rectifier and the DC-DC converter is disconnected. After the rectifier and the DC-DC converter are connected, the rectifier is used to convert the AC power output by the power supply into DC power. The MPPT control circuit generates a voltage control signal based on the magnitude of the DC power and the open-circuit voltage of the power supply. The DC-DC converter adjusts its equivalent impedance according to the voltage control signal and generates a corresponding output voltage. After adjustment, the equivalent impedance of the DC-DC converter is equal to the internal resistance of the power supply. The energy storage circuit receives the output voltage of the DC-DC converter for storage and collection. The MPPT control circuit includes: a controller and a tracking circuit; The controller determines whether the current state is deviating from or near the maximum power point based on the magnitude of the open-circuit voltage of the DC power supply and the voltage power supply, as well as a preset period. When deviating from the maximum power point, the controller controls the tracking circuit to generate a voltage control signal in a binary variable step size manner. When near the maximum power point, the controller controls the tracking circuit to generate a voltage control signal in a fixed step size manner. The tracking circuit includes: a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first capacitor, a second capacitor, a third capacitor, a first current source, and a second current source; One end of the first switch is connected to one end of the second switch and one end of the first capacitor. The other end of the second switch is connected to one end of the third switch, one end of the fourth switch, one end of the fifth switch, one end of the second capacitor, and the second input terminal of the DC-DC converter. The other end of the first switch is connected to the output terminal of the peak detection circuit and one end of the first current source. The other end of the first current source is connected to the other end of the third switch. The other end of the fourth switch is connected to one end of the second current source. The other end of the fifth switch is connected to one end of the third capacitor. The sixth switch is connected to both ends of the third capacitor. The other end of the first capacitor is connected to the other end of the second current source, the other end of the third capacitor, and the other end of the second capacitor and grounded.

2. The maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management according to claim 1, characterized in that, When the tracking circuit generates a voltage control signal in a binary variable step size manner, the first switch, the second switch, the fifth switch, the sixth switch, the first capacitor, the second capacitor, and the third capacitor are activated.

3. The maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management according to claim 1, characterized in that, When the tracking circuit generates a voltage control signal in a fixed step manner, the third switch, the fourth switch, the second capacitor, the first current source, and the second current source operate.

4. The maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management according to claim 1, characterized in that, The rectifier includes: a first PMOS transistor, a second PMOS transistor, a first NMOS transistor, a second NMOS transistor, a first diode, a second diode, a first comparator, and a second comparator; The drain of the first PMOS transistor is connected to the gate of the second PMOS transistor, the drain of the first NMOS transistor, the cathode of the first diode, the negative input terminal of the first comparator, and one end of the output terminal of the voltage power supply. The drain of the second PMOS transistor is connected to the gate of the first PMOS transistor, the drain of the second NMOS transistor, the cathode of the second diode, the negative input terminal of the second comparator, and the other end of the output terminal of the voltage power supply. The source of the first PMOS transistor is connected to the source of the second PMOS transistor, the input terminal of the peak detection circuit, and the first input terminal of the DC-DC converter. The source of the first NMOS transistor is connected to the source of the second NMOS transistor, the anode of the first diode, the anode of the second diode, the positive input terminal of the first comparator, and the positive input terminal of the second comparator.

5. The maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management according to claim 1, characterized in that, The peak detection circuit includes: a fourth capacitor, a third PMOS transistor, a fourth PMOS transistor, a fifth PMOS transistor, a sixth PMOS transistor, a third NMOS transistor, a fourth NMOS transistor, a fifth NMOS transistor, a sixth NMOS transistor, a seventh NMOS transistor, an eighth NMOS transistor, a ninth NMOS transistor, and a single pulse generation circuit; One end of the fourth capacitor is connected to the first output terminal of the rectifier, and the other end of the fourth capacitor is connected to the drain of the third NMOS transistor, the drain and gate of the fourth NMOS transistor, and the gate of the fifth NMOS transistor. The drain of the fifth NMOS transistor is connected to the drain and gate of the third PMOS transistor, the gate of the fourth PMOS transistor, and the gate of the fifth PMOS transistor. The drain of the third PMOS transistor is connected to the drain of the sixth NMOS transistor, and the gate of the sixth NMOS transistor is connected to the drain of the fifth PMOS transistor, the gate and drain of the seventh NMOS transistor, the gate of the eighth NMOS transistor, the gate of the ninth NMOS transistor, and the gate of the sixth PMOS transistor. The drain of the sixth PMOS transistor is connected to the drain of the ninth NMOS transistor and the input terminal of the single pulse generation circuit. The output terminal of the single pulse generation circuit is connected to the input terminal of the MPPT control circuit and the gate of the third NMOS transistor. The drain of the eighth NMOS transistor receives the bias current. The source of the third PMOS transistor is connected to the source of the fourth PMOS transistor, the source of the fifth PMOS transistor, and the source of the sixth PMOS transistor. The source of the third NMOS transistor, the source of the fourth NMOS transistor, the source of the fifth NMOS transistor, the source of the sixth NMOS transistor, the source of the seventh NMOS transistor, the source of the eighth NMOS transistor, and the source of the ninth NMOS transistor are all connected to ground.

6. The maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management according to claim 1, characterized in that, The DC-DC converter includes: a seventh PMOS transistor, an eighth PMOS transistor, a tenth NMOS transistor, an eleventh NMOS transistor, an inductor, a hysteresis comparator, a ring oscillator, a PFM controller, a driver stage, a fifth capacitor, a first resistor, a second resistor, and a third resistor. The source of the seventh PMOS transistor is connected to the second output terminal of the rectifier. The drain of the seventh PMOS transistor is connected to one end of the inductor and the drain of the tenth NMOS transistor. The other end of the inductor is connected to the drain of the eighth PMOS transistor and the drain of the eleventh NMOS transistor. The source of the eighth PMOS transistor is connected to one end of the fifth capacitor, one end of the first resistor, and one end of the second resistor. The other end of the fifth capacitor is connected to the other end of the first resistor and one end of the third resistor and grounded. The other end of the second resistor is connected to the other end of the third resistor and the negative input terminal of the hysteresis comparator. The output terminal of the hysteresis comparator is connected to the first input terminal of the ring oscillator. The second input terminal of the ring oscillator is connected to the output terminal of the MPPT control circuit. The output terminal of the ring oscillator is connected to the input terminal of the PFM controller. The output terminal of the PFM controller is connected to the input terminal of the driver stage. The output terminal of the driver stage is connected to the gates of the seventh PMOS transistor, the eighth PMOS transistor, the tenth NMOS transistor, and the eleventh NMOS transistor.

7. The maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management according to claim 1, characterized in that, It also includes: the sixth capacitor, the seventh capacitor, and the seventh switch; The seventh switch is connected between the second output terminal of the rectifier and the first input terminal of the DC-DC converter. One end of the sixth capacitor is connected to one end of the seventh switch and the second output terminal of the rectifier. One end of the seventh capacitor is connected to the first input terminal of the DC-DC converter. The other ends of the sixth capacitor and the other ends of the seventh capacitor are grounded.

8. The maximum power point tracking algorithm circuit for piezoelectric micro-energy harvesting power management according to claim 1, characterized in that, The DC-DC converter is also used to receive the DC power output by the rectifier, compare the DC power with a reference voltage signal, and when the DC power is greater than the reference voltage signal, the DC-DC converter stops outputting voltage.

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