Adaptive sampling open-circuit voltage MPPT method and system suitable for piezoelectric energy acquisition

Abstract

The invention discloses a self-adaptive sampling open-circuit voltage MPPT method and system suitable for piezoelectric energy acquisition, the method is applied to an MPPT control circuit, and the circuit comprises a duty ratio monitoring circuit, a sampling signal generation circuit and a sampling hold circuit; the method comprises the following steps: monitoring the duty ratio of a comparison signal generated by a rectifier in real time by using a duty ratio monitoring circuit, and generating a monitoring signal; generating a sampling signal according to the monitoring signal by using a sampling signal generating circuit; the sampling and holding circuit is used for sampling the open-circuit voltage of the piezoelectric power supply to determine the maximum power point voltage, and the MPPT power level in the piezoelectric energy acquisition circuit is controlled to track the maximum power point according to the maximum power point voltage. The MPPT control circuit is optimized, and when the system has high tracking precision, open-circuit voltage sampling and MPPT do not need to be carried out, so that energy waste caused by open-circuit sampling and power consumption of the MPPT circuit are reduced, and the energy collection efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of maximum power point tracking, and in particular relates to an adaptive sampling open circuit voltage MPPT method and system suitable for piezoelectric energy acquisition. Background Art

[0002] Piezoelectric energy harvesting technology has the characteristics of high power density, small size, and relatively simple structure, and is very suitable for powering portable electronic devices. In order to enable the piezoelectric energy harvesting device to always output at maximum power, it is necessary to use MPPT (Maximum Power Point Tracking) technology for the piezoelectric energy harvesting device. The working efficiency of the MPPT circuit is related to the duty cycle of the comparison signal generated by the rectifier in the piezoelectric energy harvesting circuit. When the duty cycle is 50%, the theoretical tracking efficiency of the MPPT circuit is 100%. The greater the degree to which the duty cycle deviates from 50%, the lower the tracking efficiency of the MPPT circuit. At this time, it is necessary to re-sample the open circuit voltage and perform MPPT tracking.

[0003] The traditional FOCV MPPT method performs MPPT at a fixed period (e.g., 128 piezoelectric vibration cycles), activating the process even in a steady state where MPPT is not required. Unnecessary open-circuit sampling leads to energy collection interruption and causes excessive energy loss in the MPPT circuit, resulting in reduced energy collection efficiency. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides an adaptive sampling open circuit voltage MPPT method and system suitable for piezoelectric energy acquisition. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides an adaptive sampling open circuit voltage MPPT method suitable for piezoelectric energy acquisition, the method comprising:

[0006] The duty cycle monitoring circuit in the MPPT control circuit is used to monitor in real time the comparison signal V generated by the rectifier in the piezoelectric energy acquisition circuit in each monitoring cycle. COMP , generating a characterizing comparison signal V COMP The monitoring signal comprises: a first monitoring signal V DET and the second monitoring signal V DET , the first monitoring signal V DET Compare with signal V COMP The conduction pulse width corresponds to the second monitoring signal V DET Compare with signal V COMP The turn-off pulse width corresponds to;

[0007] The sampling signal generating circuit in the MPPT control circuit is used to compare the first monitoring signal V DET and the second monitoring signal V DET , select the first monitoring signal V DET and the second monitoring signal V DET The larger value is used as the first output signal V DET_Max , select the first monitoring signal V DET and the second monitoring signal V DET The smaller value is used as the second output signal V DET_Min , according to the first output signal V DET_Max and the second output signal V DET_Min Output comparison signal V MPP_COMP , the comparison signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of the sampling signal V SAMPLE ;

[0008] If the sampling signal V SAMPLE , using the sampling and holding circuit in the MPPT control circuit, the open circuit voltage V of the piezoelectric power source in the piezoelectric energy acquisition circuit P Sampling is performed to determine the maximum power point voltage V MPPT , controlling the MPPT power level in the piezoelectric energy harvesting circuit according to the maximum power point voltage V MPPT Works to achieve maximum power point tracking.

[0009] In one embodiment of the present invention, a duty cycle monitoring circuit comprises:

[0010] The monitoring control signal generating circuit and the capacitor charging and discharging circuit are connected in sequence.

[0011] In one embodiment of the present invention, the duty cycle monitoring circuit in the MPPT control circuit is used to monitor in real time the comparison signal V generated by the rectifier in the piezoelectric energy harvesting circuit in each monitoring cycle. COMP , generating a characterizing comparison signal V COMP The duty cycle monitoring signal includes:

[0012] The monitoring control signal generating circuit generates an enable signal E N_MPPT Under the control of , according to the comparison signal V generated by the rectifier in the piezoelectric energy harvesting circuit within a monitoring cycle COMP , generate monitoring control signal;

[0013] The capacitor charging and discharging circuit generates a comparison signal V according to the monitoring control signal. COMPThe first monitoring signal V of the duty cycle DET and the second monitoring signal V DET .

[0014] In one embodiment of the present invention, the first monitoring signal V DET and the comparison signal V generated by the rectifier COMP is proportional to the on-pulse width.

[0015] In one embodiment of the present invention, the second monitoring signal V DET and the comparison signal V generated by the rectifier COMP is proportional to the turn-off pulse width.

[0016] In one embodiment of the present invention, a sampling signal generating circuit includes:

[0017] The voltage selection circuit, voltage dividing circuit, comparison circuit and low pulse generating circuit are connected in sequence.

[0018] In one embodiment of the present invention, the sampling signal generating circuit in the MPPT control circuit is used to compare the first monitoring signal V DET and the second monitoring signal V DET , select the first monitoring signal V DET and the second monitoring signal V DET The larger value is used as the first output signal V DET_Max , select the first monitoring signal V DET and the second monitoring signal V DET The smaller value is used as the second output signal V DET_Min , according to the first output signal V DET_Max and the second output signal V DET_Min Output comparison signal V MPP_COMP , the comparison signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of the sampling signal V SAMPLE ,include:

[0019] The voltage selection circuit selects the first monitoring signal V DET and the second monitoring signal V DET Perform detection and select the first monitoring signal V DET and the second monitoring signal V DET The larger value is used as the first output signal V DET_Max And output to the voltage divider circuit, select the first monitoring signal V DET and the second monitoring signal V DET The smaller value is used as the second output signal V DET_Min and output to the comparison circuit;

[0020] The voltage divider circuit outputs the first signal V DET_Max Perform voltage division processing and output the divided voltage V Div_Max ;

[0021] The comparison circuit outputs the second signal V DET_Min And the divided voltage V Div_Max Compare and output comparison signal V MPP_COMP ;

[0022] The low pulse generating circuit compares the signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of the sampling signal V SAMPLE .

[0023] In a second aspect, the present invention provides an adaptive sampling open circuit voltage MPPT system suitable for piezoelectric energy acquisition, the system comprising:

[0024] Duty cycle monitoring circuit, sampling signal generating circuit and sampling and holding circuit; wherein,

[0025] The duty cycle monitoring circuit is used to monitor in real time the comparison signal V generated by the rectifier in the piezoelectric energy acquisition circuit in each monitoring cycle. COMP , generating a characterizing comparison signal V COMP The monitoring signal comprises: a first monitoring signal V DET and the second monitoring signal V DET , the first monitoring signal V DET Compare with signal V COMP The conduction pulse width corresponds to the second monitoring signal V DET is the comparison signal V COMP The turn-off pulse width corresponds to;

[0026] The sampling signal generating circuit is used to compare the first monitoring signal V DET and the second monitoring signal V DET , select the first monitoring signal V DET and the second monitoring signal V DET The larger value is used as the first output signal V DET_Max , select the first monitoring signal V DET and the second monitoring signal V DET The smaller value is used as the second output signal V DET_Min , according to the first output signal V DET_Max and the second output signal V DET_Min Output comparison signal V MPP_COMP , the comparison signal V MPP_COMPPerform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of the sampling signal V SAMPLE ;

[0027] The sample-and-hold circuit is used to generate a sampling signal V SAMPLE , the open circuit voltage V of the piezoelectric source in the piezoelectric energy harvesting circuit P Sampling is performed to determine the maximum power point voltage V MPPT , controlling the MPPT power level in the piezoelectric energy harvesting circuit according to the maximum power point voltage V MPPT Works to achieve maximum power point tracking.

[0028] In one embodiment of the present invention, a duty cycle monitoring circuit comprises:

[0029] A monitoring control signal generating circuit and a capacitor charging and discharging circuit connected in sequence; wherein,

[0030] The monitoring control signal generating circuit comprises: a frequency divider and a frequency division control circuit; wherein,

[0031] The input end of the frequency divider is connected to the first input end of the frequency division control circuit and is connected to the comparison signal V generated by the rectifier. COMP , an output end is connected to a second input end of the frequency division control circuit;

[0032] The third input terminal of the frequency division control circuit is connected to the enable signal E N_MPPT ;

[0033] The capacitor charging and discharging circuit includes: a first current source I, a second current source I, a first PMOS transistor Q, a second PMOS transistor Q, a first NMOS transistor Q, a second NMOS transistor Q, a first charging capacitor C and a second charging capacitor C; wherein,

[0034] The input end of the first current source I is connected to the power supply voltage, and the output end is connected to the source of the first PMOS tube Q;

[0035] The input end of the second current source I is connected to the power supply voltage, and the output end is connected to the source of the second PMOS tube Q;

[0036] The gate of the first PMOS tube Q is connected to the first output end of the frequency division control circuit, and the drain is connected to the first end of the first charging capacitor C;

[0037] The gate of the second PMOS tube Q is connected to the second output end of the frequency division control circuit, and the drain is connected to the first end of the second charging capacitor C;

[0038] The source of the first NMOS transistor Q is grounded, the gate is connected to the third output terminal of the frequency division control circuit, and the drain is connected to the drain of the first PMOS transistor Q;

[0039] The source of the second NMOS transistor Q is grounded, the gate is connected to the third output terminal of the frequency division control circuit, and the drain is connected to the drain of the second PMOS transistor Q;

[0040] The second end of the first charging capacitor C is connected to the source of the first NMOS transistor Q; the voltage on the first charging capacitor C is used as the first monitoring signal V DET ;

[0041] The second end of the second charging capacitor C is connected to the source of the second NMOS transistor Q; the voltage on the second charging capacitor C is used as the second monitoring signal V DET .

[0042] In one embodiment of the present invention, a sampling signal generating circuit includes:

[0043] Voltage selection circuit, voltage dividing circuit, comparison circuit and low pulse generating circuit; wherein,

[0044] The first input terminal of the voltage selection circuit is connected to the first monitoring signal V DET The second input terminal is connected to the second monitoring signal V DET , a first output terminal is connected to the input terminal of the voltage divider circuit, and a second output terminal is connected to the inverting input terminal of the comparison circuit;

[0045] The output end of the voltage divider circuit is connected to the non-inverting input end of the comparison circuit;

[0046] The output end of the comparison circuit is connected to the input end of the low pulse generating circuit;

[0047] The output end of the low pulse generating circuit serves as the output end of the sampling signal generating circuit.

[0048] Beneficial effects of the present invention:

[0049] In the solution provided by the present invention, the duty cycle of the comparison signal generated by the rectifier is monitored in real time by using a duty cycle monitoring circuit, and the monitoring signal is judged in combination with a sampling signal generating circuit to determine whether to generate a sampling signal to adjust the MPPT control circuit, thereby improving the efficiency of the piezoelectric energy acquisition circuit. When the duty cycle is 50%, the theoretical tracking efficiency of the MPPT circuit is 100%. The greater the degree to which the duty cycle deviates from 50%, the lower the tracking efficiency of the MPPT circuit. At this time, the circuit is kept to re-sample the open circuit voltage of the piezoelectric power source to determine the maximum power point voltage and perform maximum power point tracking. The above method can be used to adjust the open circuit sampling and MPPT control circuits as needed according to the duty cycle signal generated by the rectifier, thereby realizing adaptive control of open circuit sampling and MPPT. When the duty cycle is close to 50%, the relevant circuits for open circuit voltage sampling are turned off, which saves the loss of the piezoelectric energy acquisition device, reduces energy waste, and improves energy collection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A schematic flow chart of an adaptive sampling open circuit voltage MPPT method for piezoelectric energy acquisition provided by an embodiment of the present invention;

[0051] Figure 2 A schematic diagram of the structure of the MPPT control circuit provided by an embodiment of the present invention;

[0052] Figure 3 is a circuit diagram of a duty cycle monitoring circuit provided by an embodiment of the present invention;

[0053] Figure 4 is a circuit diagram of a monitoring control signal generating circuit provided by an embodiment of the present invention;

[0054] Figure 5 is a circuit diagram of a capacitor charging and discharging circuit provided by an embodiment of the present invention;

[0055] Figure 6 is a structural schematic diagram of a sampling signal generating circuit provided by an embodiment of the present invention;

[0056] Figure 7 It is a connection diagram of the MPPT control circuit and the piezoelectric energy acquisition circuit provided by an embodiment of the present invention;

[0057] Figure 8 Schematic diagram of relevant waveforms of an adaptive sampling open circuit voltage MPPT method suitable for piezoelectric energy acquisition provided by an embodiment of the present invention;

[0058] Fig. 9 It is a schematic diagram of simulation waveforms of an adaptive sampling open-circuit voltage MPPT method suitable for piezoelectric energy acquisition provided in an embodiment of the present invention.

[0059] Reference numerals

[0060] 10-duty cycle monitoring circuit, 101-monitoring control signal generating circuit, 102-capacitor charging and discharging circuit, 20-sampling signal generating circuit, 201-voltage selection circuit, 202-voltage divider circuit, 203-comparison circuit, 204-low pulse generating circuit, 30-sampling and holding circuit. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0062] The embodiment of the present invention provides an adaptive sampling open circuit voltage MPPT method and system suitable for piezoelectric energy acquisition.

[0063] Below, firstly, an adaptive sampling open circuit voltage MPPT method suitable for piezoelectric energy acquisition provided by an embodiment of the present invention is introduced.

[0064] First, as Figure 1 As shown, an adaptive sampling open circuit voltage MPPT method suitable for piezoelectric energy acquisition provided by an embodiment of the present invention is applied to an MPPT control circuit. A structural schematic diagram of the MPPT control circuit can be seen in FIG. Figure 2 The MPPT control circuit may include: a duty cycle monitoring circuit 10, a sampling signal generating circuit 20 and a sampling and holding circuit 30 connected in sequence; the adaptive sampling open circuit voltage MPPT method suitable for piezoelectric energy acquisition may include the following steps:

[0065] S1, using the duty cycle monitoring circuit 10 in the MPPT control circuit, real-time monitoring of the comparison signal V generated by the rectifier in the piezoelectric energy harvesting circuit in each monitoring cycle COMP , generating a characterizing comparison signal V COMP The monitoring signal includes: a first monitoring signal V DET1 and the second monitoring signal V DET2 , the first monitoring signal V DET1 Compare with signal V COMP The conduction pulse width corresponds to the second monitoring signal V DET2 Compare with signal V COMP The turn-off pulse width corresponds to.

[0066] For S1, the following may be included:

[0067] S11, monitoring the control signal generating circuit 101 when the enable signal E N_MPPT Under the control of the comparison signal V generated by the rectifier in the piezoelectric energy harvesting circuit within a monitoring cycle,COMP , generate monitoring control signal;

[0068] S12, the capacitor charging and discharging circuit 102 generates a comparison signal V according to the monitoring control signal. COMP The first monitoring signal V of the duty cycle DET1 and the second monitoring signal V DET2 .

[0069] Specifically, the duty cycle monitoring circuit 10, such as Figure 3 As shown, this may include:

[0070] The monitoring control signal generating circuit 101 and the capacitor charging and discharging circuit 102 are connected in sequence.

[0071] Monitoring control signal generating circuit 101, such as Figure 4 As shown, it may include: a frequency divider and a frequency division control circuit; wherein,

[0072] The input end of the frequency divider is connected to the first input end of the frequency division control circuit and is connected to the comparison signal V generated by the rectifier. COMP , the output end is connected to the second input end of the frequency division control circuit;

[0073] The third input terminal of the frequency division control circuit is connected to the enable signal E N_MPPT .

[0074] Optionally, the frequency divider generates a comparison signal V generated by the rectifier in each monitoring cycle. COMP The frequency division control circuit is triggered by a DIV signal generated every 128 piezoelectric vibration cycles. COMP and DIV signal to generate control signal V 1 、V 2 and V N , and by the enable signal E N_MPPT Enable control. Specifically, V 1 By V COMP Take the inversion and we get, V 2 That is V COMP , V N It is always low level, and generates a high level pulse signal every 128 piezoelectric vibration cycles, which will DET1 and V DET2 Pull low to prepare for the next monitoring cycle.

[0075] Capacitor charging and discharging circuit 102, such as Figure 5 As shown, it may include: a first current source I 1 , the second current source I 2 、The first PMOS tube Q 1 , the second PMOS tube Q2 , the first NMOS tube Q 3 , the second NMOS tube Q 4 , the first charging capacitor C 1 and the second charging capacitor C 2 ;in,

[0076] The first current source I 1 The input end is connected to the power supply voltage, and the output end is connected to the first PMOS tube Q 1 The source connection of

[0077] The second current source I 2 The input end is connected to the power supply voltage, and the output end is connected to the second PMOS tube Q 2 The source connection of

[0078] The first PMOS tube Q 1 The gate is connected to the first output terminal of the frequency division control circuit, and the drain is connected to the first charging capacitor C 1 A first end is connected;

[0079] The second PMOS tube Q 2 The gate is connected to the second output terminal of the frequency division control circuit, and the drain is connected to the second charging capacitor C 2 A first end is connected;

[0080] The first NMOS tube Q 3 The source is grounded, the gate is connected to the third output terminal of the frequency division control circuit, and the drain is connected to the first PMOS tube Q 1 The drain connection of

[0081] The second NMOS tube Q 4 The source is grounded, the gate is connected to the third output terminal of the frequency division control circuit, and the drain is connected to the second PMOS tube Q 2 The drain connection of

[0082] The first charging capacitor C 1 The second end of the first NMOS tube Q 3 The source of the first charging capacitor C 1 The voltage on the DET1 ;

[0083] The second charging capacitor C 2 The second end of the second NMOS tube Q 4 The source of the second charging capacitor C 2 The voltage on the DET2 .

[0084] Specifically, the first charging capacitor C 1 And the first NMOS tube Q 3 In parallel, the second charging capacitor C2 And the second NMOS tube Q 4 The first PMOS tube Q 1 The comparison signal V generated by the rectifier COMP When turned on, it turns on and charges the first capacitor C 1 Charging, the comparison signal V generated by the rectifier COMP The second PMOS tube Q is closed when turned off; 2 The comparison signal V generated by the rectifier COMP When turned off, it turns on and charges the second capacitor C 2 Charging, the comparison signal V generated by the rectifier COMP When one cycle is over, the first charging capacitor C 1 The voltage on the DET1 is sent to the sampling signal generating circuit 20, the second charging capacitor C 2 The voltage on the DET2 is sent to the sampling signal generating circuit 20. After 128 piezoelectric vibration cycles, V N A high level pulse appears, turning on the first NMOS tube Q 3 And the second NMOS tube Q 4 , release C 1 and C 2 The charge on the DET1 and V DET2 All jump to low level.

[0085] It can be understood that the duty cycle monitoring circuit 10 generates a comparison signal V COMP The on and off pulse widths are monitored and a monitoring signal is generated. The monitoring signal includes a first monitoring signal V DET1 and the second monitoring signal V DET2 , the first monitoring signal V DET1 and the second monitoring signal V DET2 Respectively with V COMP The on-pulse width and the off-pulse width correspond and are proportional. Optionally, the first monitoring signal V DET1 is the monitoring signal corresponding to the comparison signal generated by the rectifier when it is turned on. The first monitoring signal V DET1 and the comparison signal V generated by the rectifier COMP The second monitoring signal V DET2 is the monitoring signal corresponding to when the comparison signal generated by the rectifier is turned off, and the second monitoring signal V DET2 and the comparison signal V generated by the rectifier COMPIn the embodiment of the present invention, the capacitor charging and discharging circuit 102 monitors the V generated by the control signal generating circuit 101. 1 、V 2 and V N The signal is activated to complete the comparison signal V generated by the rectifier. COMP Optionally, E N_MPPT The signal is an enable signal. When E N_MPPT When the signal is high, the duty cycle monitoring circuit starts working.

[0086] S2, using the sampling signal generating circuit 20 in the MPPT control circuit to compare the first monitoring signal V DET1 and the second monitoring signal V DET2 , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The larger value is used as the first output signal V DET_Max , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The smaller value is used as the second output signal V DET_Min , according to the first output signal V DET_Max and the second output signal V DET_Min Output comparison signal V MPP_COMP , the comparison signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of the sampling signal V SAMPLE .

[0087] Specifically, the sampling signal generating circuit 20, such as Figure 6 As shown, this may include:

[0088] The voltage selection circuit 201, the voltage dividing circuit 202, the comparison circuit 203 and the low pulse generating circuit 204 are connected in sequence; wherein,

[0089] The first input terminal of the voltage selection circuit 201 is connected to the first monitoring signal V DET1 , the second input terminal is connected to the second monitoring signal V DET2 , the first output terminal is connected to the input terminal of the voltage divider circuit 202, and the second output terminal is connected to the inverting input terminal of the comparison circuit 203;

[0090] The output terminal of the voltage divider circuit 202 is connected to the non-inverting input terminal of the comparison circuit 203;

[0091] The output terminal of the comparison circuit 203 is connected to the input terminal of the low pulse generating circuit 204;

[0092] The output terminal of the low pulse generating circuit 204 serves as the output terminal of the sampling signal generating circuit 20 .

[0093] For S2, this may include:

[0094] S21, the voltage selection circuit 201 selects the first monitoring signal V DET1 and the second monitoring signal V DET2 Perform detection and select the first monitoring signal V DET1 and the second monitoring signal V DET2 The larger value is used as the first output signal V DET_Max Output to the voltage divider circuit 202, select the first monitoring signal V DET1 and the second monitoring signal V DET2 The smaller value is used as the second output signal V DET_Min Output to the comparison circuit 203;

[0095] S22, the voltage divider circuit 202 generates a first output signal V DET_Max Perform voltage division processing and output the divided voltage V Div_Max ;

[0096] S23, the comparison circuit 203 compares the second output signal V DET_Min And the divided voltage V Div_Max Compare and output comparison signal V MPP_COMP ;

[0097] S24, the low pulse generating circuit 204 compares the signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of V generates a low level pulse as the sampling signal SAMPLE .

[0098] It can be understood that in the embodiment of the present invention, the two input terminals of the voltage selection circuit 201 are connected to the two output terminals of the duty cycle monitoring circuit 10, the first output terminal of the voltage selection circuit 201 is connected to the input terminal of the voltage divider circuit 202, the output terminal of the voltage divider circuit 202 is connected to the inverting input terminal of the comparison circuit 203, the second output terminal of the voltage selection circuit 201 is connected to the non-inverting input terminal of the comparison circuit 203, and the output terminal of the comparison circuit 203 is connected to the input terminal of the low pulse generating circuit 204. Specifically, the first output terminal of the voltage selection circuit 201 converts the first monitoring signal V DET1 and the second monitoring signal V DET2 The larger value V DET_Max The second output terminal of the voltage selection circuit 201 converts the first monitoring signal V DET1 and the second monitoring signal V DET2 The smaller value V DET_MinThe voltage divider circuit 202 outputs the larger voltage V Div_Max Output to the non-inverting input terminal of the comparison circuit 203. The voltage divider circuit 202 may include a buffer, a first resistor and a second resistor; wherein the positive input terminal of the buffer serves as the input terminal of the voltage divider circuit 202, the output terminal of the buffer is connected to the negative input terminal of the buffer, and the negative input terminal of the buffer is connected to the first terminal of the first resistor; the second terminal of the first resistor is connected to the second terminal of the second resistor and serves as the output terminal of the voltage divider circuit 202, and the second terminal of the second resistor is grounded. The comparison circuit 203 converts V DET_Min and V Div_Max Perform numerical comparison. If V DET_Min Greater than V Div_Max , then the comparison signal V MPP_COMP is high level, if V DET_Min Less than V Div_Max , then the comparison signal V MPP_COMP The low level pulse generating circuit 204 detects the comparison signal V MPP_COMP A low level pulse V is generated at the falling edge of SAMPLE The comparison circuit 203 may be formed of a comparator.

[0099] The embodiment of the present invention utilizes the duty cycle monitoring circuit 10 to monitor the duty cycle of the comparison signal generated by the rectifier, and combines the sampling signal generating circuit 20 to judge the monitoring signal to determine whether to generate a sampling signal; to adjust the MPPT control circuit, thereby achieving the efficiency improvement of the piezoelectric energy acquisition circuit. When the duty cycle is 50%, the theoretical tracking efficiency of the MPPT circuit is 100%. The greater the degree to which the duty cycle deviates from 50%, the lower the tracking efficiency of the MPPT circuit. At this time, a sampling signal is generated, so that the sampling and holding circuit 30 re-samples the open circuit voltage of the piezoelectric power source to determine the maximum power point voltage, and performs maximum power point tracking.

[0100] S3, if the sampling signal V SAMPLE , using the sampling and holding circuit 30 in the MPPT control circuit, the open circuit voltage V of the piezoelectric power source in the piezoelectric energy acquisition circuit is P Sampling is performed to determine the maximum power point voltage V MPPT , controls the MPPT power level in the piezoelectric energy harvesting circuit according to the maximum power point voltage V MPPT Works to achieve maximum power point tracking.

[0101] Specifically, when the sampling signal V SAMPLE When the sampling and holding circuit 30 is at a low level, the open circuit voltage V P Sampling is performed to determine the maximum power point voltage signal V MPPT, and controls the MPPT circuit to start MPPT operation. For a connection diagram of the MPPT control circuit and the piezoelectric energy acquisition circuit provided in an embodiment of the present invention, see Figure 7 .from Figure 7 It can be seen that the piezoelectric power source in the piezoelectric energy harvesting circuit is an AC source. The piezoelectric energy harvesting circuit also includes a rectifier, and the rectifier includes: a first-stage negative voltage converter and a second-stage active diode, and the second-stage active diode includes a comparator COMP and a transistor M1. Among them, the first input terminal of the first-stage negative voltage converter is connected to the piezoelectric power source, and the second input terminal is connected to the ground, the first output terminal of the first-stage negative voltage converter is connected to the source terminal of the transistor M1 included in the second-stage active diode, and the second output terminal is connected to the ground; the negative input terminal of the comparator in the second-stage active diode is connected to the source terminal of M1, the positive input terminal is connected to the drain terminal of M1, and the output terminal of the comparator is connected to the gate terminal of M1. Optionally, M1 is a PMOS tube. In an embodiment of the present invention, the duty cycle monitoring circuit monitors the comparison signal generated by the rectifier as the comparison signal V generated by the comparator in the second-stage active diode included in the rectifier. COMP .

[0102] Continue to see Figure 7 The piezoelectric energy harvesting circuit also includes a capacitor C REC , C REC One end is connected to the drain end of the transistor M1 and the other end is grounded.

[0103] Specifically, the voltage signal V generated by the rectifier to the voltage source P Plastic surgery, including:

[0104] The first-stage negative voltage converter converts the negative half-cycle signal of the voltage signal into a positive half-cycle signal, and sends the positive half-cycle signal to the second-stage active diode.

[0105] The second-stage active diode converts the positive half-cycle signal into a DC voltage signal V REC and the comparator output signal V COMP Sent to the monitoring input of the duty cycle monitoring circuit.

[0106] Capacitor C REC The function of the DC voltage signal V REC Perform filtering.

[0107] It can be understood that the MPPT power level in the piezoelectric energy harvesting circuit is the post-stage load of the rectifier, and the MPPT power level in the piezoelectric energy harvesting circuit is controlled according to the maximum power point voltage V MPPT The operation is performed so that the input impedance of the subsequent load of the piezoelectric rectifier reaches the optimal load impedance to achieve maximum power point tracking.

[0108] Figure 81 is a schematic diagram of the waveforms of the adaptive sampling open circuit voltage MPPT method for piezoelectric energy acquisition provided in the embodiment of the present invention. N_MPPT is the start signal of the MPPT module, V COMP is the comparison signal generated by the rectifier, V 1 The signal is V COMP The signal tracks the signal during the on period, V 2 The signal is V COMP The signal tracks the signal during the off period. Figure 4 , at t 0 Moment, V N A high pulse will be generated, making the first NMOS tube Q 3 And the second NMOS tube Q 4 conduction, respectively, to V DET1 and V DET2 Voltage is released, V DET1 and V DET2 The value is restored to 0. Please continue to see Figure 8 , the first charging capacitor C 1 From 0 At the beginning of the moment, after a short pulse V N After the signal is reset to zero, at V 1 The first charging capacitor C 1 The voltage value V DET1 is the first monitoring signal, and its value is 1 Always maintain; the second charging capacitor C 2 In t 0 The moment also passes through a short pulse V N The signal is reset to zero and then 1 The moment begins, at V 2 The signal is charged during the period of low level, and the second charging capacitor C 2 The voltage value V DET2 is the second monitoring signal, whose value is at t 2 Always maintain, their sizes are respectively V COMP The duty cycle of on and off is positively correlated. Then, the sampling signal generation circuit generates V DET1 and V DET2 The signal is selected, divided and compared. The voltage division ratio of the voltage division circuit constrains the degree of deviation of the duty cycle from 50%. Optionally, taking the voltage division ratio of 0.8 as an example, the deviation of ±5.5% is constrained, that is, when the duty cycle is greater than 55.5% and less than 44.5%, the comparison result should be V DET1 Greater than 0.8*V DET2 , at this time, the low pulse generating circuit generates V SAMPLE The signal is valid at low level. Figure 1 and Figure 2 The sample-and-hold circuit starts to measure the open-circuit voltage V P Sampling is performed to determine the maximum power point voltage signal V MPPT , and controls the MPPT power level in the piezoelectric energy harvesting circuit according to the maximum power point voltage V MPPT Perform maximum power point tracking. N_MPPT It takes 1.5 cycles from the time the signal is valid at a high level to the time the system obtains the sampling signal.

[0109] Similarly, if V obtained in the above process DET1 The value is less than 0.8*V DET2 , then the low pulse generating circuit generates V SAMPLE The signal is high level, then the duty cycle of the comparison signal generated by the rectifier is large, and the working efficiency of the MPPT circuit is high. At this time, open circuit sampling and MPPT operation are not performed. Figure 1 and Figure 2 , the sample and hold circuit does not operate.

[0110] It can be understood that the adaptive sampling open-circuit voltage MPPT method for piezoelectric energy acquisition provided in the embodiment of the present invention can also be applied to the adaptive sampling open-circuit voltage for thermoelectric energy acquisition. Specifically, in the PWM (pulse width modulation) control mode with a fixed pulse frequency adopted by the thermoelectric energy acquisition circuit, the duty cycle monitoring circuit 10 in the MPPT control circuit is used to monitor the driving signal of the main power switch tube in the MPPT power stage in real time, and generate a monitoring signal representing the duty cycle of the main power switch tube driving signal; the monitoring signal includes a first monitoring signal V DET1 and the second monitoring signal V DET2 , the first monitoring signal V DET1 Corresponding to the conduction pulse width of the main power switch tube drive signal, the second monitoring signal V DET2 Corresponding to the off pulse width of the main power switch tube drive signal; using the sampling signal generating circuit 20 in the MPPT control circuit to compare the first monitoring signal V DET1 and the second monitoring signal V DET2 , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The larger value is used as the first output signal V DET_Max , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The smaller value is used as the second output signal V DET_Min , according to the first output signal V DET_Max and the second output signal V DET_Min Output comparison signal V MPP_COMP, for the comparison signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of V generates a low level pulse as the sampling signal SAMPLE ; If the sampling signal V is generated SAMPLE , using the sampling and holding circuit 30 in the MPPT control circuit, the open circuit voltage V of the pressure source in the thermoelectric energy acquisition circuit is P Sampling is performed to determine the maximum power point voltage V MPPT , controls the MPPT power level in the thermoelectric energy harvesting circuit according to the maximum power point voltage V MPPT Works to achieve maximum power point tracking.

[0111] Fig. 9 1 is a schematic diagram of the simulation waveforms of the adaptive sampling open circuit voltage MPPT method for piezoelectric energy acquisition provided by the embodiment of the present invention. Fig. 9 As shown, every 128 piezoelectric vibration cycles, V COMP The duty cycle of the first monitoring action is monitored once, and the need for MPPT operation is determined based on the monitoring results. As shown in the dotted line frame in the figure, the simulation waveform related to the first monitoring action is enlarged. N_MPPT The signal is an enable signal. When E N_MPPT When the signal is high, the V COMP The duty cycle of the V N Generates a high level pulse to V DET1 and V DET2 The residual voltage is released. Then, V 1 and V 2 Start tracking V COMP The signal is turned on and off, V DET1 and V DET2 The signals start to charge respectively. Then the sampling signal generation circuit selects, divides and compares them. COMP The duty cycle is set to 44%, the voltage divider ratio is set to 0.8, and the comparison circuit is set to V DET1 and 0.8*V DET2 The comparison result is V DET1 Greater than 0.8*V DET2 Therefore, in the second piezoelectric vibration cycle, V SAMPLE The signal is valid at low level. Finally, if Figure 1 and Figure 2 As shown, the sample-and-hold circuit starts to measure the open-circuit voltage V P Sampling is performed to determine the maximum power point voltage signal V MPPT , and controls the MPPT power level in the piezoelectric energy harvesting circuit according to the maximum power point voltage VMPPT Perform maximum power point tracking.

[0112] In the second aspect, corresponding to the above method embodiment, the embodiment of the present invention also provides an adaptive sampling open circuit voltage MPPT system suitable for piezoelectric energy acquisition, such as Figure 2 As shown, this may include:

[0113] Duty cycle monitoring circuit 10, sampling signal generating circuit 20 and sampling and holding circuit 30; wherein,

[0114] The duty cycle monitoring circuit 10 is used to monitor in real time the comparison signal V generated by the rectifier in the piezoelectric energy acquisition circuit in each monitoring cycle. COMP , generating a characterizing comparison signal V COMP The monitoring signal includes: a first monitoring signal V DET1 and the second monitoring signal V DET2 , the first monitoring signal V DET1 Compare with signal V COMP The conduction pulse width corresponds to the second monitoring signal V DET2 is the comparison signal V COMP The turn-off pulse width corresponds to;

[0115] The sampling signal generating circuit 20 is used to compare the first monitoring signal V DET1 and the second monitoring signal V DET2 , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The larger value is used as the first output signal V DET_Max , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The smaller value is used as the second output signal V DET_Min , according to the first output signal V DET_Max and the second output signal V DET_Min Output comparison signal V MPP_COMP , for the comparison signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of V generates a low level pulse as the sampling signal SAMPLE ;

[0116] The sample-and-hold circuit 30 is used to generate a sampling signal V SAMPLE , the open circuit voltage V of the piezoelectric source in the piezoelectric energy harvesting circuit P Sampling is performed to determine the maximum power point voltage V MPPT , controls the MPPT power level in the piezoelectric energy harvesting circuit according to the maximum power point voltage V MPPT Works to achieve maximum power point tracking.

[0117] It can be understood that the detailed working principle of the duty cycle monitoring circuit 10 can refer to the working process corresponding to S1 in the method embodiment provided in the first aspect, the detailed working principle of the sampling signal generating circuit 20 can refer to the working process corresponding to S2 in the method embodiment provided in the first aspect, and the detailed working principle of the sampling and holding circuit 30 can refer to the working process corresponding to S3 in the method embodiment provided in the first aspect, and no further details will be given here.

[0118] The embodiment of the present invention utilizes a duty cycle monitoring circuit to monitor the duty cycle of the comparison signal generated by the rectifier, and combines the sampling signal generating circuit to judge the monitoring signal to determine whether to generate a sampling signal, so as to adjust the MPPT control circuit, thereby improving the efficiency of the piezoelectric energy acquisition circuit. When the duty cycle is 50%, the theoretical tracking efficiency of the MPPT circuit is 100%. The greater the degree to which the duty cycle deviates from 50%, the lower the tracking efficiency of the MPPT circuit. At this time, the circuit is kept to re-sample the open circuit voltage of the piezoelectric power source to determine the maximum power point voltage and perform maximum power point tracking. Through the above method, the open circuit sampling and MPPT control circuits can be adjusted as needed according to the duty cycle signal generated by the rectifier, thereby realizing adaptive control of open circuit sampling and MPPT. When the duty cycle is close to 50%, the relevant circuits for open circuit voltage sampling are turned off, which saves the loss of the piezoelectric energy acquisition device, reduces energy waste, and improves energy collection efficiency.

[0119] It should be noted that in the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0120] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. An adaptive sampling open circuit voltage MPPT method suitable for piezoelectric energy acquisition, applied to MPPT control circuit, characterized in that: include: The duty cycle monitoring circuit (10) in the MPPT control circuit is used to monitor in real time the comparison signal V generated by the rectifier in the piezoelectric energy acquisition circuit in each monitoring cycle. COMP , generating a characterizing comparison signal V COMP The monitoring signal comprises: a first monitoring signal V DET1 and the second monitoring signal V DET2 , the first monitoring signal V DET1 Compare with signal V COMP The conduction pulse width corresponds to the second monitoring signal V DET2 Compare with signal V COMP The turn-off pulse width corresponds to; The sampling signal generating circuit (20) in the MPPT control circuit is used to compare the first monitoring signal V DET1 and the second monitoring signal V DET2 , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The larger value is used as the first output signal V DET_Max , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The smaller value is used as the second output signal V DET_Min , according to the first output signal V DET_Max and the second output signal V DET_Min Output comparison signal V MPP_COMP , the comparison signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of the sampling signal V SAMPLE ; If the sampling signal V SAMPLE , using the sampling and holding circuit (30) in the MPPT control circuit, the open circuit voltage V of the piezoelectric power source in the piezoelectric energy acquisition circuit P Sampling is performed to determine the maximum power point voltage V MPPT , controlling the MPPT power level in the piezoelectric energy harvesting circuit according to the maximum power point voltage V MPPT Works to achieve maximum power point tracking.

2. The method of adaptively sampling open circuit voltage MPPT for piezoelectric energy acquisition according to claim 1, characterized in that: The duty cycle monitoring circuit (10) comprises: A monitoring control signal generating circuit (101) and a capacitor charging and discharging circuit (102) are connected in sequence.

3. The adaptive sampling open circuit voltage MPPT method suitable for piezoelectric energy acquisition according to claim 2, characterized in that: The duty cycle monitoring circuit (10) in the MPPT control circuit is used to monitor in real time the comparison signal V generated by the rectifier in the piezoelectric energy acquisition circuit in each monitoring cycle. COMP , generating a characterizing comparison signal V COMP The duty cycle monitoring signal includes: The monitoring control signal generating circuit (101) generates an enable signal E N_MPPT Under the control of , according to the comparison signal V generated by the rectifier in the piezoelectric energy harvesting circuit within a monitoring cycle COMP , generate monitoring control signal; The capacitor charging and discharging circuit (102) generates a comparison signal V according to the monitoring control signal. COMP The first monitoring signal V of the duty cycle DET1 and the second monitoring signal V DET2 .

4. The adaptive sampling open circuit voltage MPPT method for piezoelectric energy acquisition according to claim 1, characterized in that: The first monitoring signal V DET1 and the comparison signal V generated by the rectifier COMP is proportional to the on-pulse width.

5. The adaptive sampling open circuit voltage MPPT method for piezoelectric energy acquisition according to claim 1, characterized in that: The second monitoring signal V DET2 and the comparison signal V generated by the rectifier COMP is proportional to the turn-off pulse width.

6. The adaptive sampling open circuit voltage MPPT method for piezoelectric energy acquisition according to claim 1, characterized in that: The sampling signal generating circuit (20) comprises: A voltage selection circuit (201), a voltage dividing circuit (202), a comparison circuit (203) and a low pulse generating circuit (204) are connected in sequence.

7. The adaptive sampling open circuit voltage MPPT method for piezoelectric energy acquisition according to claim 6, characterized in that: The sampling signal generating circuit (20) in the MPPT control circuit is used to compare the first monitoring signal V DET1 and the second monitoring signal V DET2 , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The larger value is used as the first output signal V DET_Max , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The smaller value is used as the second output signal V DET_Min , according to the first output signal V DET_Max and the second output signal V DET_Min Output comparison signal V MPP_COMP , the comparison signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of the sampling signal V SAMPLE ,include: The voltage selection circuit (201) selects the first monitoring signal V DET1 and the second monitoring signal V DET2 Perform detection and select the first monitoring signal V DET1 and the second monitoring signal V DET2 The larger value is used as the first output signal V DET_Max and output to the voltage divider circuit (202), selecting the first monitoring signal V DET1 and the second monitoring signal V DET2 The smaller value is used as the second output signal V DET_Min and output to the comparison circuit (203); The voltage divider circuit (202) generates a first output signal V DET_Max Perform voltage division processing and output the divided voltage V Div_Max ; The comparison circuit (203) generates a second output signal V DET_Min And the divided voltage V Div_Max Compare and output comparison signal V MPP_COMP ; The low pulse generating circuit (204) generates a comparison signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of the sampling signal V SAMPLE .

8. An adaptive sampling open circuit voltage MPPT system suitable for piezoelectric energy acquisition, characterized in that: include: A duty cycle monitoring circuit (10), a sampling signal generating circuit (20) and a sampling and holding circuit (30); wherein, The duty cycle monitoring circuit (10) is used to monitor in real time the comparison signal V generated by the rectifier in the piezoelectric energy acquisition circuit in each monitoring cycle. COMP , generating a characterizing comparison signal V COMP The monitoring signal comprises: a first monitoring signal V DET1 and the second monitoring signal V DET2 , the first monitoring signal V DET1 Compare with signal V COMP The conduction pulse width corresponds to the second monitoring signal V DET2 is the comparison signal V COMP The turn-off pulse width corresponds to; The sampling signal generating circuit (20) is used to compare the first monitoring signal V DET1 and the second monitoring signal V DET2 , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The larger value is used as the first output signal V DET_Max , select the first monitoring signal V DET1 and the second monitoring signal V DET2 The smaller value is used as the second output signal V DET_Min , according to the first output signal V DET_Max and the second output signal V DET_Min Output comparison signal V MPP_COMP , the comparison signal V MPP_COMP Perform detection and judgment. When the comparison signal V is detected MPP_COMP The falling edge of the sampling signal V SAMPLE ; The sample-and-hold circuit (30) is used to generate a sampling signal V SAMPLE , the open circuit voltage V of the piezoelectric source in the piezoelectric energy harvesting circuit P Sampling is performed to determine the maximum power point voltage V MPPT , controlling the MPPT power level in the piezoelectric energy harvesting circuit according to the maximum power point voltage V MPPT Works to achieve maximum power point tracking.

9. The adaptive sampling open circuit voltage MPPT system suitable for piezoelectric energy acquisition according to claim 8, characterized in that: The duty cycle monitoring circuit (10) comprises: A monitoring control signal generating circuit (101) and a capacitor charging and discharging circuit (102) connected in sequence; wherein, The monitoring control signal generating circuit (101) comprises: a frequency divider and a frequency division control circuit; wherein, The input end of the frequency divider is connected to the first input end of the frequency division control circuit and is connected to the comparison signal V generated by the rectifier. COMP , an output end is connected to a second input end of the frequency division control circuit; The third input terminal of the frequency division control circuit is connected to the enable signal E N_MPPT ; The capacitor charging and discharging circuit (102) comprises: a first current source I1, a second current source I2, a first PMOS transistor Q1, a second PMOS transistor Q2, a first NMOS transistor Q3, a second NMOS transistor Q4, a first charging capacitor C1 and a second charging capacitor C2; wherein, The input end of the first current source I1 is connected to the power supply voltage, and the output end is connected to the source of the first PMOS tube Q1; The input end of the second current source I2 is connected to the power supply voltage, and the output end is connected to the source of the second PMOS tube Q2; The gate of the first PMOS transistor Q1 is connected to the first output terminal of the frequency division control circuit, and the drain is connected to the first terminal of the first charging capacitor C1; The gate of the second PMOS tube Q2 is connected to the second output end of the frequency division control circuit, and the drain is connected to the first end of the second charging capacitor C2; The source of the first NMOS transistor Q3 is grounded, the gate is connected to the third output terminal of the frequency division control circuit, and the drain is connected to the drain of the first PMOS transistor Q1; The source of the second NMOS transistor Q4 is grounded, the gate is connected to the third output terminal of the frequency division control circuit, and the drain is connected to the drain of the second PMOS transistor Q2; The second end of the first charging capacitor C1 is connected to the source of the first NMOS transistor Q3; the voltage on the first charging capacitor C1 is used as the first monitoring signal V DET1 ; The second end of the second charging capacitor C2 is connected to the source of the second NMOS transistor Q4; the voltage on the second charging capacitor C2 is used as the second monitoring signal V DET2 .

10. The adaptive sampling open circuit voltage MPPT system suitable for piezoelectric energy acquisition according to claim 8, characterized in that: The sampling signal generating circuit (20) comprises: A voltage selection circuit (201), a voltage dividing circuit (202), a comparison circuit (203) and a low pulse generating circuit (204); wherein, The first input terminal of the voltage selection circuit (201) is connected to the first monitoring signal V DET1 The second input terminal is connected to the second monitoring signal V DET2 , a first output end is connected to the input end of the voltage divider circuit (202), and a second output end is connected to the inverting input end of the comparison circuit (203); The output end of the voltage divider circuit (202) is connected to the non-inverting input end of the comparison circuit (203); The output end of the comparison circuit (203) is connected to the input end of the low pulse generating circuit (204); The output end of the low pulse generating circuit (204) serves as the output end of the sampling signal generating circuit (20).

Images