CN112910412B - A ring oscillator frequency modulation circuit - Google Patents

Abstract

The invention discloses a ring oscillator frequency modulation circuit, comprising: a coarse adjustment frequency module, which is used for receiving a first count signal and a second count signal output by a counter in a maximum power point tracking circuit, and outputs the corresponding coarse adjustment frequency signal; the fine tuning frequency module is used to receive the third count signal and the fourth count signal output by the counter in the maximum power point tracking circuit, and output the corresponding fine tuning frequency signal; the ring oscillator frequency generation module is used to receive the coarse tuning signal. The frequency modulation signal and the fine modulation frequency signal are generated, and the corresponding oscillation frequency is generated, and the oscillation frequency is input to the maximum power point tracking circuit for frequency modulation. The invention can generate a stable oscillation frequency corresponding to the counting signal, so as to track the maximum power point; the invention has the advantages of small integration area, low power consumption, accurate frequency modulation and high stability. The present invention can be widely used in the field of integrated circuits.

Description

A ring oscillator frequency modulation circuit

technical field

The invention relates to the field of integrated circuits, in particular to a ring oscillator frequency modulation circuit.

Background technique

With the continuous development of energy harvesting technology, the collection and utilization of micro-power energy has begun to come into people's field of vision in recent years. This technology converts the energy wasted in the form of light, heat, vibration, etc. collected from the environment into electrical energy through energy converters and stores them to provide energy for wireless sensor nodes. Therefore, a maximum power point tracking circuit is required in circuit design to maximize the energy output power. Under this requirement, the frequency modulation scheme of maximum power point tracking circuit (MPPT) is proposed. Frequency modulation is a modulation mode used for maximum power point tracking in thermoelectric energy harvesting circuits. It can dynamically adjust the switching frequency of the system to ensure that the two impedances are equal, that is, the input voltage is half of the open-circuit voltage of the energy source during operation, so as to ensure the tracking of the maximum power point, so that the energy source is always at the maximum Power outputs energy to the load.

The frequency modulation of the traditional MPPT circuit needs to know exactly the energy source and internal resistance, and the internal resistance of the energy source is greatly affected by the environment, so it cannot match the flexible and diverse voltage sources in practical applications, and the traditional scheme has disadvantages such as high power consumption and large integration area.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a ring oscillator frequency modulation circuit.

The technical scheme adopted by the present invention is:

The embodiment of the present invention includes a ring oscillator frequency modulation circuit, which is used for frequency modulation of a maximum power point tracking circuit in thermoelectric energy acquisition, including:

a coarse frequency adjustment module, configured to receive the first count signal and the second count signal output by the counter in the maximum power point tracking circuit, and output the corresponding coarse adjustment frequency signal;

a fine-tune frequency module, configured to receive the third count signal and the fourth count signal output by the counter in the maximum power point tracking circuit, and output the corresponding fine-tune frequency signal;

The ring oscillator frequency generating module is configured to receive the coarse adjustment frequency signal and the fine adjustment frequency signal, and generate a corresponding oscillation frequency, and the oscillation frequency is input to the maximum power point tracking circuit for frequency modulation.

Further, the first count signal is the highest bit signal in the four-bit count signal output by the counter in the maximum power point tracking circuit; the second count signal is the output of the counter in the maximum power point tracking circuit The next highest signal in the four-bit count signal; the third count signal is the lowest signal of the four-bit count signal output by the counter in the maximum power point tracking circuit; the fourth count signal is the maximum The second low-order signal of the four-bit count signal output by the counter in the power point tracking circuit.

Further, the coarse adjustment frequency signal includes a first control signal, a second control signal, a third control signal and a fourth control signal;

The first control signal is obtained by inverting the first counting signal and the second counting signal respectively and then summing them;

The second control signal is obtained by taking the inversion of the first count signal and the addition of the second count signal;

The third control signal is obtained by inverting the second counting signal and adding the first counting signal;

The fourth control signal is obtained by adding the first count signal and the second count signal.

Further, the fine adjustment frequency signal includes a fifth control signal, a sixth control signal, a seventh control signal and an eighth control signal;

After the inversion of the fourth counting signal, it is combined with the third counting signal to obtain a first result, the third counting signal is ANDed with the fourth counting signal to obtain a second result, and the first result is the same as the result. The second result phase or the third result is obtained, the first control signal and the second control signal phase or the fourth result is obtained;

the fifth control signal is obtained by adding the third result and the fourth result;

After the inversion of the third count signal and the fourth count signal to obtain a fifth result, the fifth result and the second result or to obtain a sixth result;

The sixth control signal is obtained by adding the sixth result and the fourth result;

The third control signal is phased with the fourth control signal to obtain a seventh result;

the seventh control signal is obtained by adding the seventh result and the third result;

The eighth control signal is obtained by adding the sixth result and the seventh result.

Further, the ring oscillator frequency generating module includes a ring oscillator unit, a control output frequency unit and a capacitor unit;

The ring oscillator unit includes a first inverter, a second inverter, a third inverter, a fourth inverter, a fifth inverter, a sixth inverter, a seventh inverter, a third inverter The eight inverters and the ninth inverter have a total of nine inverters, and the nine inverters are connected in series; the output end of the second inverter outputs the first signal, and the output end of the third inverter outputs the second signal, the output terminal of the fourth inverter outputs the third signal, and the output terminal of the fifth inverter outputs the fourth signal;

The capacitor unit includes a first capacitor, a second capacitor, a third capacitor and a fourth capacitor, a first switch, a second switch, a third switch, and a fourth switch, and the capacitors are connected in parallel with each other. One end is connected to the first signal, the second end of the first switch is connected to the first end of the first capacitor, the second end of the first capacitor is grounded; the first end of the second switch is connected to the ground; The terminal is connected to the second signal, the second terminal of the second switch is connected to the first terminal of the second capacitor, the second terminal of the second capacitor is grounded; the first terminal of the third switch The third signal is connected, the second end of the third switch is connected to the first end of the third capacitor, the second end of the third capacitor is grounded; the first end of the fourth switch is connected inputting the fourth signal, the second end of the fourth switch is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is grounded;

The control output frequency unit includes a fifth switch, a sixth switch, a seventh switch and an eighth switch, all switches are connected in parallel with each other, one end of the fifth switch is connected to the first signal, and the other end of the fifth switch is connected to the first signal. One end of the sixth switch is connected to the power supply voltage; one end of the sixth switch is connected to the second signal, and the other end of the sixth switch is connected to the power supply voltage; one end of the seventh switch is connected to the third signal, the first The other end of the seven switches is connected to the power supply voltage; one end of the eighth switch is connected to the fourth signal, and the other end of the eighth switch is connected to the power supply voltage.

Further, the output end of the third inverter is connected to the first control signal, the output end of the fifth inverter is connected to the second control signal, and the output end of the seventh inverter is connected to the second control signal. The third control signal is connected to the terminal, and the fourth control signal is connected to the output terminal of the ninth inverter.

Further, the first switch is controlled by the fifth control signal output by the fine frequency adjustment module, the second switch is controlled by the sixth control signal output by the fine frequency adjustment module, and the third switch is controlled by the The fourth switch is controlled by the eighth control signal output by the fine frequency adjustment module.

Further, the fifth switch is controlled by the first control signal output by the coarse frequency adjustment module, the sixth switch is controlled by the second control signal output by the coarse frequency adjustment module, and the seventh switch is controlled by the The eighth switch is controlled by a fourth control signal output by the coarse frequency adjustment module.

Further, an eighth result is obtained by adding the first signal and the first control signal, a ninth result is obtained by adding the second signal and the second control signal, and the eighth result and the The ninth result is phased or the tenth result is obtained; the eleventh result is obtained by adding the third signal and the third control signal, and the twelfth result is obtained by the addition of the fourth signal and the fourth control signal. The eleventh result and the twelfth result OR the thirteenth result; the tenth result and the thirteenth result OR the oscillation frequency and output.

Further, after the oscillation frequency is input to the maximum power point tracking circuit, three control signals are obtained through the frequency division module, and the three control signals act on the counter in the maximum power point tracking circuit, and the counter receives three control signals. Each of the control signals controls and then outputs a four-bit corresponding count signal.

The beneficial effects of the present invention are:

The ring oscillator frequency modulation circuit of the present invention includes a coarse adjustment frequency module, a fine adjustment frequency module and a ring oscillator frequency generation module. The ring oscillator frequency generation module receives the coarse adjustment frequency signal output by the coarse adjustment frequency module and the fine adjustment frequency module. The output fine-tuned frequency signal can generate a stable oscillation frequency corresponding to the counting signal, so as to track the maximum power point; the invention has the advantages of small integration area, low power consumption, accurate frequency modulation, and high stability.

Additional aspects and advantages of the present invention will be set forth, in part, from the following description, and in part will be apparent from the following description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

1 is a circuit diagram of a ring oscillator frequency modulation circuit according to an embodiment of the present invention;

2 is a schematic diagram of a coarse frequency adjustment module according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a fine-tuning frequency module according to an embodiment of the present invention;

FIG. 4 is a circuit diagram of a maximum power point tracking according to an embodiment of the present invention.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present invention, and should not be construed as a limitation of the present invention.

In the description of the present invention, it should be understood that the azimuth description, such as the azimuth or position relationship indicated by up, down, front, rear, left, right, etc., is based on the azimuth or position relationship shown in the drawings, only In order to facilitate the description of the present invention and simplify the description, it is not indicated or implied that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention.

In the description of the present invention, the meaning of several is one or more, the meaning of multiple is two or more, greater than, less than, exceeding, etc. are understood as not including this number, above, below, within, etc. are understood as including this number. If it is described that the first and the second are only for the purpose of distinguishing technical features, it cannot be understood as indicating or implying relative importance, or indicating the number of the indicated technical features or the order of the indicated technical features. relation.

In the description of the present invention, unless otherwise clearly defined, words such as setting, installation, connection should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meaning of the above words in the present invention in combination with the specific content of the technical solution.

The embodiments of the present application will be further described below with reference to the accompanying drawings.

1, an embodiment of the present invention includes a ring oscillator frequency modulation circuit for frequency modulation of a maximum power point tracking circuit in thermoelectric energy harvesting, including:

a coarse frequency adjustment module, configured to receive the first count signal and the second count signal output by the counter in the maximum power point tracking circuit, and output the corresponding coarse adjustment frequency signal;

a fine-tune frequency module, configured to receive the third count signal and the fourth count signal output by the counter in the maximum power point tracking circuit, and output the corresponding fine-tune frequency signal;

The ring oscillator frequency generating module is configured to receive the coarse adjustment frequency signal and the fine adjustment frequency signal, and generate a corresponding oscillation frequency, and the oscillation frequency is input to the maximum power point tracking circuit for frequency modulation.

Wherein, the ring oscillator frequency generating module includes a ring oscillator unit, a control output frequency unit and a capacitor unit;

The ring oscillator unit includes a first inverter, a second inverter, a third inverter, a fourth inverter, a fifth inverter, a sixth inverter, a seventh inverter, a third inverter The eight inverters and the ninth inverter have a total of nine inverters, and the nine inverters are connected in series; the output end of the second inverter outputs the first signal, and the output end of the third inverter outputs the second signal, the output terminal of the fourth inverter outputs the third signal, and the output terminal of the fifth inverter outputs the fourth signal;

The capacitor unit includes a first capacitor, a second capacitor, a third capacitor and a fourth capacitor, a first switch, a second switch, a third switch, and a fourth switch, and the capacitors are connected in parallel with each other. One end is connected to the first signal, the second end of the first switch is connected to the first end of the first capacitor, the second end of the first capacitor is grounded; the first end of the second switch is connected to the ground; The terminal is connected to the second signal, the second terminal of the second switch is connected to the first terminal of the second capacitor, the second terminal of the second capacitor is grounded; the first terminal of the third switch The third signal is connected, the second end of the third switch is connected to the first end of the third capacitor, the second end of the third capacitor is grounded; the first end of the fourth switch is connected inputting the fourth signal, the second end of the fourth switch is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is grounded;

The control output frequency unit includes a fifth switch, a sixth switch, a seventh switch and an eighth switch, all switches are connected in parallel with each other, one end of the fifth switch is connected to the first signal, and the other end of the fifth switch is connected to the first signal. One end of the sixth switch is connected to the power supply voltage; one end of the sixth switch is connected to the second signal, and the other end of the sixth switch is connected to the power supply voltage; one end of the seventh switch is connected to the third signal, the first The other end of the seven switches is connected to the power supply voltage; one end of the eighth switch is connected to the fourth signal, and the other end of the eighth switch is connected to the power supply voltage.

Optionally, the first count signal is the highest bit signal in the four-bit count signal output by the counter in the maximum power point tracking circuit; the second count signal is the counter in the maximum power point tracking circuit. The second highest-order signal in the output four-bit count signal; the third count signal is the lowest-order signal in the four-bit count signal output by the counter in the maximum power point tracking circuit; the fourth count signal is the The second-lowest signal of the four-bit count signal output by the counter in the maximum power point tracking circuit.

In this embodiment, the structure of the ring oscillator frequency modulation circuit is realized by a standard CMOS process, and the coarse adjustment frequency module can realize a coarse adjustment mechanism of frequency adjustment in a wide range from 4kHz to 15kHz. The coarse adjustment frequency module receives the signal from the maximum power point tracking circuit. Among the four-bit counting signals output by the counter, the highest-order signal Y ₃ and the next _- highest-order signal Y ₂ Y ₀ .

Optionally, the coarse adjustment frequency signal includes a first control signal, a second control signal, a third control signal and a fourth control signal;

The first control signal is obtained by inverting the first counting signal and the second counting signal respectively and then summing them;

The second control signal is obtained by taking the inversion of the first count signal and the addition of the second count signal;

The third control signal is obtained by inverting the second counting signal and adding the first counting signal;

The fourth control signal is obtained by adding the first count signal and the second count signal.

Referring to FIG. 2 , in this embodiment, the coarse frequency adjustment module receives the highest-order signal Y ₃ and the second highest-order signal Y ₂ and outputs four-bit control signals, which are the first control signal H ₀ , the second control signal H ₁ , and the third control signal H 1 , respectively. Control signal H ₂ and fourth control signal H ₃ , the four-bit control signal is generated according to the received highest-order signal Y ₃ and the second highest-order signal Y ₂ ; specifically, H ₀ , H ₁ , H ₂ and H ₃ Obtained in the following ways:

The first control signal H ₀ : Y ₃ is inverted to obtain Y ₃ ′, Y ₂ is inverted to obtain Y ₂ ′, and Y ₃ ′ is summed with Y ₂ ′ to obtain H ₀ ;

The second control signal H ₁ : Y ₃ ′ is combined with the phase Y ₂ to obtain H ₁ ;

The third control signal H ₂ : Y ₃ is combined with 'Y ₂ to obtain H ₂ ;

Fourth control signal H ₃ : Y ₃ and Y ₂ are summed to obtain H ₃ .

Optionally, the fine-tuned frequency signal includes a fifth control signal, a sixth control signal, a seventh control signal, and an eighth control signal;

After the inversion of the fourth counting signal, it is combined with the third counting signal to obtain a first result, the third counting signal is ANDed with the fourth counting signal to obtain a second result, and the first result is the same as the result. The second result phase or the third result is obtained, the first control signal and the second control signal phase or the fourth result is obtained;

the fifth control signal is obtained by adding the third result and the fourth result;

After the inversion of the third count signal and the fourth count signal to obtain a fifth result, the fifth result and the second result or to obtain a sixth result;

The sixth control signal is obtained by adding the sixth result and the fourth result;

The third control signal is phased with the fourth control signal to obtain a seventh result;

the seventh control signal is obtained by adding the seventh result and the third result;

The eighth control signal is obtained by ANDing the sixth result and the seventh result.

Referring to FIG. 3 , in this embodiment, the fine-tuning frequency module receives the second-lowest-order signal Y ₁ and the lowest-order signal Y ₀ and outputs four-bit control signals, which are the fifth control signal L ₀ , the sixth control signal L ₁ , and the seventh control signal L 1 , respectively. control signal L ₂ and eighth control signal L ₃ ; the four-bit control signal is generated according to the received second-lowest-order signal Y ₁ and lowest-order signal Y ₀ and the four-bit control signal output by the coarse frequency adjustment module; specifically, L ₀ , L ₁ , L ₂ and L ₃ are obtained in the following ways:

Fifth control signal L ₀ : Y ₁ is inverted to obtain Y ₁ ′, Y ₁ ′ and Y ₀ are summed to obtain X ₀ , Y ₁ and Y ₀ are summed to obtain X ₁ , X ₀ and X ₁ are summed or Z ₀ is obtained, H0 and H1 phase or get Z ₁ , Z ₀ and Z ₁ phase and get L ₀ ;

Sixth control signal L ₁ : Y ₀ is inverted to obtain Y ₀ ′, Y ₀ ′ is summed with Y ₁ to obtain X ₂ , X ₂ is summed with X ₁ or Z ₂ is obtained, and Z ₂ is summed with Z ₁ to obtain L ₁ ;

Seventh control signal L ₂ : H ₂ and H ₃ phase or obtain Z ₃ , Z ₀ and Z ₃ phase and obtain L ₂ ;

Eighth control signal L ₃ : Z ₂ and Z ₃ are summed to obtain L ₃ .

The output end of the third inverter is connected to the first control signal, the output end of the fifth inverter is connected to the second control signal, and the output end of the seventh inverter is connected to For the third control signal, the output end of the ninth inverter is connected to the fourth control signal.

Optionally, the first switch is controlled by a fifth control signal output by the fine frequency adjustment module, the second switch is controlled by a sixth control signal output by the fine frequency adjustment module, and the third switch is controlled by The seventh control signal output by the fine frequency adjustment module is controlled, and the fourth switch is controlled by the eighth control signal output by the fine frequency adjustment module.

In this embodiment,

Optionally, the fifth switch is controlled by a first control signal output by the coarse frequency adjustment module, the sixth switch is controlled by a second control signal output by the coarse frequency adjustment module, and the seventh switch is controlled by The third control signal output from the coarse frequency adjustment module is controlled, and the eighth switch is controlled by the fourth control signal output from the coarse frequency adjustment module.

Optionally, the first signal and the first control signal are ANDed to obtain an eighth result, the second signal and the second control signal are ANDed to obtain a ninth result, and the eighth result and the The ninth result is ORed to obtain the tenth result; the third signal is ANDed with the third control signal to obtain the eleventh result, and the fourth signal is ANDed with the fourth control signal to obtain the twelfth result, The eleventh result and the twelfth result are ORed to obtain the thirteenth result; the tenth result is ORed with the thirteenth result to obtain the oscillation frequency and output.

In this embodiment, the upper two bits of the control signal output by the counter in the maximum power point tracking circuit are used to control the number of stages connected to the inverters in the ring oscillator unit. The frequency formulas corresponding to different stages are as follows:

H ₀ =(～Y ₃ )&(～Y ₂ )→three-stage ring oscillation→f=15KHz;

H ₁ =(～Y ₃ )&(Y ₂ )→five-order ring oscillation→f=10KHz;

H ₂ =(Y ₃ )&(～Y ₂ )→seven-order ring oscillation→f=7KHz;

H ₃ =(Y ₃ )&(Y ₂ )→nine-order ring oscillation→f=4KHz;

It can be seen that the frequency coarse adjustment range is 4KHz-15KHz; among them, H ₀ , H ₁ , H ₂ and H ₃ are the four output signals output by the coarse adjustment frequency module, which control the three-level, fifth-level, seventh-level, and nine-level ring rings respectively. Oscillation output; when the upper two control signals Y ₃ and Y ₂ of the counter output are 00, 01, 10, and 11, they are connected to the third, fifth, seventh, and ninth ring oscillations respectively, and the frequency is roughly adjusted at this time. If the tracking circuit according to the maximum frequency point needs to be connected to a three-stage or five-stage ring oscillation, when the count signals Y ₁ and Y ₀ of the lower two bits output by the counter are 01, 10, and 11, the fine-tuning frequency respectively connected Capacitors are C ₀ , C ₁ , C ₀ , C ₁ ; if a seven-level or nine-level ring oscillation is connected, the counter control signals Y ₁ and Y ₀ of the lower two bits are 01, 10, and 11, respectively connected to The fine tuning frequency capacitors are C ₂ , C ₃ , C ₂ , and C ₃ .

In this embodiment, the four-bit control signals H ₀ , H ₁ , H ₂ and H ₃ output by the coarse frequency adjustment module are respectively associated with the outputs of the three-level oscillation, five-level oscillation, seven-level oscillation and nine-level oscillation of the ring oscillator unit. connected; the output signals of the second-level oscillation, the third-level oscillation, the fourth-level oscillation and the fifth-level oscillation of the ring oscillator unit are respectively S ₀ , S ₁ , S ₂ and S ₃ ; The control signals L ₀ , L ₁ , L ₂ and L ₃ control four switches, namely the first switch, the second switch, the third switch and the fourth switch, wherein one end of the first switch is connected to S ₀ , and the other end of the first switch is connected to S 0 . One end is connected to one end of the first capacitor C ₀ of the capacitor unit, and the other end of the first capacitor C ₀ is connected to the ground; one end of the second switch is connected to S ₁ , and the other end of the second switch is connected to the second capacitor C ₁ of the capacitor unit. one end, the other end of the second capacitor C ₁ is connected to the ground; one end of the third switch is connected to S ₂ , the other end of the third switch is connected to one end of the third capacitor C ₂ of the capacitor unit, and the other end of the third capacitor C ₂ is connected to One end of the fourth switch is connected to S ₃ , the other end of the fourth switch is connected to one end of the fourth capacitor C ₃ of the capacitor unit, and the other end of the fourth capacitor C ₃ is connected to the ground; the control output frequency unit includes four The switches controlled by H ₀ , H ₁ , H ₂ and H ₃ are respectively the fifth switch, the sixth switch, the seventh switch and the eighth switch, one end of the fifth switch is connected to S ₀ , and the other end is connected to the power supply voltage; One end of the sixth switch is connected to S ₁ , and the other end is connected to the power supply voltage; one end of the seventh switch is connected to S ₂ , and the other end is connected to the power supply voltage; one end of the eighth switch is connected to S ₃ , and the other end is connected to the power supply voltage; S ₀ , H ₀ The result of the phase and the result of the phase and the phase of S ₁ , H ₁ is phase-or, the result of the phase-and phase of S ₂ , H ₂ is phase-or the result of the phase-and phase of S ₃ , H ₃ , and the result of the phase-or phase above is re- phase-or The output frequency f of the whole ring oscillator frequency generation module, f is input to the maximum power point tracking circuit for frequency modulation. The ring oscillator frequency generation module receives each four-bit control signal from the coarse frequency adjustment module and the fine adjustment frequency module, and applies the control signal to the inverters and fine adjustment capacitor switches with different access stages, and different counting signals. Corresponding to different frequencies, it meets the frequency requirements of the maximum power point tracking in the maximum power point tracking circuit.

4, in this embodiment, the oscillation frequency generated by the ring oscillator frequency generation module is input to the maximum power point tracking circuit for frequency modulation; wherein the overall work flow of the maximum power point tracking circuit is as follows: VT is the output voltage of the energy source , VSamp is half of the open-loop voltage of the energy source; when the maximum power point tracking circuit starts to work, the initial count of the counter COUNTER is 0000, and the output frequency of the ring oscillator frequency generation module is 20kHz. After the frequency division module, we get Three control signals CLK1, CLK2, CLK3 with slower frequency and less high-level effective time, when the CLK1 signal is high, the circuit sampling signal is valid at this time, the sampling phase is turned on, and the circuit is in the open-loop phase. At the same time, the two switches are closed under the action of the signal, and half of the open-loop voltage is stored into the capacitor under the action of the sampling resistor. The input voltage at this time is compared with the sampled half voltage, and the circuit inputs the comparison result into the counter to obtain the corresponding counting signal. When CLK3 is at high level, the counting signal of the circuit is valid, the counting signal is turned on, the circuit will receive the comparison signal from the comparator at this time, and output the corresponding counting signal to control the coarse adjustment frequency module and fine adjustment in the frequency modulation circuit. Modulate the frequency module to generate matching frequencies.

Specifically, the VT of the maximum power point tracking circuit is connected to the boost conversion circuit; in energy harvesting applications, the energy source is greatly affected by changes in environmental conditions such as temperature and air pressure, so the range of internal resistance changes is very large, and it is necessary to ensure that the circuit obtains For maximum power, the internal resistance of the energy source should be equal to the input impedance of the boost circuit, that is, _Req = RT. In the boost conversion circuit of energy harvesting, the output voltage Vout>>Vin, at this time, in order to meet the maximum power condition, the boost The equivalent impedance of the circuit can be given by:

Req=RT= _8Lf ;

In the formula, L is the inductance value of the boost circuit, and f is the output frequency of the ring oscillator frequency generation module; when the internal resistance of the energy source changes, the frequency modulation module can dynamically adjust the frequency, so that the internal resistance of the energy source is equal to that of the boost conversion circuit. Equivalent input impedance for maximum power point tracking.

The ring oscillator frequency modulation circuit according to the embodiment of the present invention has the following technical effects:

The frequency modulation circuit according to the embodiment of the present invention includes a coarse frequency adjustment module, a fine frequency adjustment module and a ring oscillator frequency generation module. The ring oscillator frequency generation module receives the coarse adjustment frequency signal output by the coarse adjustment frequency module and the output of the fine frequency adjustment module. The fine-tuned frequency signal can generate a stable oscillation frequency corresponding to the counting signal, so as to track the maximum power point; the invention has the advantages of small integration area, low power consumption, accurate frequency modulation, and high stability.

The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned embodiments, and within the scope of knowledge possessed by those of ordinary skill in the technical field, various changes can also be made without departing from the purpose of the present invention. .

Claims (8)

1. A ring oscillator frequency modulation circuit for frequency modulation of a maximum power point tracking circuit in thermoelectric energy harvesting, comprising:

a coarse tuning frequency module, configured to receive a first counting signal and a second counting signal output by a counter in the maximum power point tracking circuit, and output a corresponding coarse tuning frequency signal;

the fine frequency adjusting module is used for receiving a third counting signal and a fourth counting signal output by a counter in the maximum power point tracking circuit and outputting corresponding fine frequency adjusting signals;

a ring oscillator frequency generation module, configured to receive the coarse frequency signal and the fine frequency signal, and generate a corresponding oscillation frequency, where the oscillation frequency is input to the maximum power point tracking circuit for frequency modulation;

the coarse frequency signal comprises a first control signal, a second control signal, a third control signal and a fourth control signal;

the first control signal is obtained by performing phase reversal on the first counting signal and the second counting signal respectively and then performing phase reversal;

the second control signal is obtained by taking the phase of the inverted first counting signal and the phase of the inverted second counting signal;

the third control signal is obtained by taking the phase of the inverted second counting signal and the phase of the first counting signal;

the fourth control signal is obtained by taking the phase of the first counting signal and the second counting signal;

the fine frequency adjustment signal comprises a fifth control signal, a sixth control signal, a seventh control signal and an eighth control signal;

after the fourth counting signal is negated, performing an AND operation with the third counting signal to obtain a first result, performing an AND operation with the third counting signal to obtain a second result, performing an AND operation with the second result to obtain a third result, and performing an AND operation with the first control signal to obtain a second result;

the fifth control signal is obtained by taking the third result and the fourth result together;

after the third counting signal is inverted, performing an AND operation with the fourth counting signal to obtain a fifth result, and performing an AND operation with the second result or obtaining a sixth result;

the sixth control signal is obtained by taking the sixth result and the fourth result together;

the third control signal is either in phase with the fourth control signal or a seventh result is obtained;

the seventh control signal is obtained by taking the seventh result and the third result together;

and the eighth control signal is obtained by taking the sixth result and the seventh result together.

2. The ring oscillator frequency modulation circuit of claim 1, wherein the first count signal is a highest order signal of four-bit count signals output from a counter in the maximum power point tracking circuit; the second counting signal is a second highest signal in four-bit counting signals output by a counter in the maximum power point tracking circuit; the third counting signal is the lowest order signal in the four-order counting signals output by the counter in the maximum power point tracking circuit; the fourth counting signal is a second lowest order signal in the four-order counting signals output by the counter in the maximum power point tracking circuit.

3. The ring oscillator frequency modulation circuit according to claim 1, wherein the ring oscillator frequency generation module includes a ring oscillator unit, a control output frequency unit, and a capacitance unit;

the ring oscillator unit comprises nine inverters including a first inverter, a second inverter, a third inverter, a fourth inverter, a fifth inverter, a sixth inverter, a seventh inverter, an eighth inverter and a ninth inverter, and the nine inverters are connected in series; the output end of the second inverter outputs a first signal, the output end of the third inverter outputs a second signal, the output end of the fourth inverter outputs a third signal, and the output end of the fifth inverter outputs a fourth signal;

the capacitance unit comprises a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first switch, a second switch, a third switch and a fourth switch, all the capacitors are connected in parallel, the first end of the first switch is connected with the first signal, the second end of the first switch is connected with the first end of the first capacitor, and the second end of the first capacitor is grounded; a first end of the second switch is connected to the second signal, a second end of the second switch is connected with a first end of the second capacitor, and a second end of the second capacitor is grounded; a first end of the third switch is connected to the third signal, a second end of the third switch is connected to a first end of the third capacitor, and a second end of the third capacitor is grounded; a first end of the fourth switch is connected to the fourth signal, a second end of the fourth switch is connected to a first end of the fourth capacitor, and a second end of the fourth capacitor is grounded;

the control output frequency unit comprises a fifth switch, a sixth switch, a seventh switch and an eighth switch, the switches are connected in parallel, one end of the fifth switch is connected to the first signal, and the other end of the fifth switch is connected to the power supply voltage; one end of the sixth switch is connected to the second signal, and the other end of the sixth switch is connected to a power supply voltage; one end of the seventh switch is connected to the third signal, and the other end of the seventh switch is connected to a power supply voltage; one end of the eighth switch is connected to the fourth signal, and the other end of the eighth switch is connected to a power supply voltage.

4. The ring oscillator frequency modulation circuit according to claim 3, wherein an output terminal of the third inverter is connected to the first control signal, an output terminal of the fifth inverter is connected to the second control signal, an output terminal of the seventh inverter is connected to the third control signal, and an output terminal of the ninth inverter is connected to the fourth control signal.

5. The ring oscillator frequency modulation circuit of claim 3, wherein the first switch is controlled by a fifth control signal output by the fine frequency adjustment module, the second switch is controlled by a sixth control signal output by the fine frequency adjustment module, the third switch is controlled by a seventh control signal output by the fine frequency adjustment module, and the fourth switch is controlled by an eighth control signal output by the fine frequency adjustment module.

6. The ring oscillator frequency modulation circuit of claim 4, wherein the fifth switch is controlled by the first control signal output by the coarse frequency adjustment module, the sixth switch is controlled by the second control signal output by the coarse frequency adjustment module, the seventh switch is controlled by the third control signal output by the coarse frequency adjustment module, and the eighth switch is controlled by the fourth control signal output by the coarse frequency adjustment module.

7. The ring oscillator frequency modulation circuit of claim 4, wherein the first signal is anded with the first control signal to obtain an eighth result, the second signal is anded with the second control signal to obtain a ninth result, the eighth result is anded with the ninth result or a tenth result; the third signal is anded with the third control signal to obtain an eleventh result, the fourth signal is anded with the fourth control signal to obtain a twelfth result, the eleventh result is anded with the twelfth result or a thirteenth result; and the tenth result and the thirteenth result are combined or the oscillation frequency is obtained and output.

8. The frequency modulation circuit of claim 7, wherein the oscillation frequency is inputted to the MPPT circuit and then three control signals are obtained through a frequency division module, the three control signals act on a counter in the MPPT circuit, and the counter is controlled by the three control signals to output four-bit corresponding count signals.

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