CN112910412B - Frequency modulation circuit of ring oscillator - Google Patents
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Abstract
The invention discloses a frequency modulation circuit of a ring oscillator, which comprises: the coarse tuning frequency module is used for receiving a first counting signal and a second counting signal output by a counter in the maximum power point tracking circuit and outputting corresponding coarse tuning frequency signals; 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; and the ring oscillator frequency generation module is used for receiving the coarse adjustment frequency signal and the fine adjustment frequency signal and generating corresponding oscillation frequency, and the oscillation frequency is input to the maximum power point tracking circuit for frequency modulation. The invention can generate stable oscillation frequency corresponding to the counting signal, thereby tracking the maximum power point; the invention has the advantages of small integration area, low power consumption, accurate frequency modulation, high stability and the like. The invention can be widely applied to the field of integrated circuits.
Description
Technical Field
The invention relates to the field of integrated circuits, in particular to a frequency modulation circuit of a ring oscillator.
Background
With the continuous development of energy harvesting technology, the harvesting and utilization of micro-power energy sources has begun to come into the field of view of people in recent years. The technology converts energy collected from the environment and wasted in the forms of light, heat, vibration and the like into electric energy through an energy converter, stores the electric energy and provides energy for the wireless sensor node. Therefore, a maximum power point tracking circuit is required in the circuit design to maximize the energy output power. Under the requirement, a frequency modulation scheme for a maximum power point tracking circuit (MPPT) is proposed, the frequency modulation is a modulation mode for maximum power point tracking in a thermoelectric energy acquisition circuit, and the technology dynamically adjusts the switching frequency of a system by detecting the internal resistance of an external energy source and the equivalent input impedance of a booster circuit, so as to ensure that the two impedances are equal, namely the input voltage is half of the open-circuit voltage of the energy source when the system works, thereby ensuring the tracking of the maximum power point, and enabling the energy source to output energy to a load at the maximum power all the time.
The frequency modulation of the traditional MPPT circuit needs to know the energy source and the internal resistance exactly, the internal resistance of the energy source is greatly influenced by the environment, so that the traditional MPPT circuit cannot be matched with flexible and various voltage sources in practical application, and the traditional scheme has the defects of large power consumption, large integration area and the like.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a frequency modulation circuit of a ring oscillator.
The technical scheme adopted by the invention is as follows:
the embodiment of the invention comprises a frequency modulation circuit of a ring oscillator, which is used for the frequency modulation of a maximum power point tracking circuit in thermoelectric energy collection and comprises the following steps:
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;
and the ring oscillator frequency generation module is used for receiving the coarse adjustment frequency signal and the fine adjustment frequency signal and generating corresponding oscillation frequency, and the oscillation frequency is input to the maximum power point tracking circuit for frequency modulation.
Further, the first counting signal is the highest-order signal in four-order counting signals output by 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 signal of four-bit counting signals output by a counter in the maximum power point tracking circuit.
Further, 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 inverting and then performing phase inversion on the first counting signal and the second counting signal respectively;
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.
Further, 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;
the eighth control signal is obtained by taking the sum of the sixth result and the seventh result.
Further, the ring oscillator frequency generation module comprises 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 a 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.
Further, an output end of the third inverter is connected to the first control signal, an output end of the fifth inverter is connected to the second control signal, an output end of the seventh inverter is connected to the third control signal, and an output end of the ninth inverter is connected to the fourth control signal.
Further, 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.
Further, the fifth switch is controlled by a first control signal output by the coarse frequency adjusting module, the sixth switch is controlled by a second control signal output by the coarse frequency adjusting module, the seventh switch is controlled by a third control signal output by the coarse frequency adjusting module, and the eighth switch is controlled by a fourth control signal output by the coarse frequency adjusting module.
Further, 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 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.
Furthermore, after the oscillation frequency is input to the maximum power point tracking circuit, three control signals are obtained through a frequency division module, the three control signals act on a counter in the maximum power point tracking circuit, and the counter is controlled by the three control signals to output four-bit corresponding counting signals.
The invention has the beneficial effects that:
the ring oscillator frequency modulation circuit comprises a coarse adjustment frequency module, a fine adjustment frequency module and a ring oscillator frequency generation module, wherein the ring oscillator frequency generation module receives a coarse adjustment frequency signal output by the coarse adjustment frequency module and a fine adjustment frequency signal output by the fine adjustment frequency module and can generate stable oscillation frequency corresponding to a counting signal, so that the maximum power point is tracked; the invention has the advantages of small integration area, low power consumption, accurate frequency modulation, high stability and the like.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a circuit diagram of a ring oscillator frequency modulation according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating a coarse tuning frequency 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 invention;
fig. 4 is a circuit diagram of maximum power point tracking according to an embodiment of the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.
The embodiments of the present application will be further explained with reference to the drawings.
Referring to fig. 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 collection, including:
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;
and the ring oscillator frequency generation module is used for receiving the coarse adjustment frequency signal and the fine adjustment frequency signal and generating corresponding oscillation frequency, and the oscillation frequency is input to the maximum power point tracking circuit for frequency modulation.
The ring oscillator frequency generation module comprises a ring oscillator unit, a control output frequency unit and a capacitor 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.
Optionally, the first count signal is a highest-order signal in four-order count signals output by 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 signal of four-bit counting signals output by a counter in the maximum power point tracking circuit.
In this embodiment, the ring oscillator frequency modulation circuit structure is implemented by a standard CMOS process, the coarse tuning frequency module can implement a coarse tuning mechanism for adjusting a wide range of frequencies from 4kHz to 15kHz, and the coarse tuning frequency module receives a highest-order bit signal Y of four-bit counting signals output from a counter in the maximum power point tracking circuit3And the second highest signal Y2(ii) a The fine frequency regulation module receives a second lower signal Y in four-bit counting signals output by a counter in the maximum power point tracking circuit1And the least significant bit signal Y0。
Optionally, the coarse 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 and then performing phase inversion on the first counting signal and the second counting signal respectively;
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.
Referring to FIG. 2, in this embodiment, the coarse tuning frequency module receives the most significant bit signal Y3And the second highest signal Y2And outputs four-bit control signals, which are the first control signals H0A second control signal H1A third control signal H2And a fourth control signal H3The four bit controlThe signal is based on the most significant signal Y received3And the second highest signal Y2The result is obtained; in particular, H0、H1、H2And H3Respectively obtaining the following steps:
first control signal H0：Y3Taking the inverse to obtain Y3′，Y2Taking the inverse to obtain Y2′，Y3' and Y2' phase reaction to give H0；
Second control signal H1：Y3' and phase Y2And with obtaining H1；
Third control signal H2：Y3And' Y2And are reacted to give H2；
Fourth control signal H3：Y3And Y2And are reacted to give H3。
Optionally, the fine frequency adjustment signal includes 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;
the eighth control signal is obtained by taking the sum of the sixth result and the seventh result.
Referring to fig. 3, in the present embodiment, the fine frequency adjustment module receives the sub-low signal Y1And the least significant bit signal Y0And outputs four-bit control signals, which are respectively fifth control signals L0A sixth control signal L1A seventh control signal L2And an eighth control signal L3(ii) a The four-bit control signal is based on the received next lower signal Y1And the least significant bit signal Y0And the four-bit control signal output by the coarse frequency adjusting module is generated; specifically, L0、L1、L2And L3Respectively obtaining the following steps:
fifth control signal L0：Y1Taking the inverse to obtain Y1′，Y1' and Y0And are reacted to obtain X0，Y1And Y0And are reacted to obtain X1，X0And X1Phase or result in Z0H0 with H1 or to obtain Z1，Z0And Z1And taking phase to obtain L0；
Sixth control signal L1：Y0Taking the inverse to obtain Y0′，Y0' and Y1And taking phase to obtain X2，X2And X1Is in phase or gives Z2，Z2And Z1And are reacted to give L1；
Seventh control signal L2：H2And H3Phase or result in Z3，Z0And Z3And are reacted to give L2；
Eighth control signal L3：Z2And Z3And are reacted to give L3。
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, the output end of the seventh inverter is connected to the third control signal, and 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, 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.
In the present embodiment, the first and second electrodes are,
optionally, the fifth switch is controlled by a first control signal output by the coarse tuning frequency module, the sixth switch is controlled by a second control signal output by the coarse tuning frequency module, the seventh switch is controlled by a third control signal output by the coarse tuning frequency module, and the eighth switch is controlled by a fourth control signal output by the coarse tuning frequency module.
Optionally, 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.
In this embodiment, the number of stages of the access inverter in the ring oscillator unit is controlled by the high two-bit control signal output by the counter in the maximum power point tracking circuit, and the frequency formulas corresponding to different stages are as follows:
H0＝(～Y3)&(～Y2) → three-level ring oscillation → f ═ 15 KHz;
H1＝(～Y3)&(Y2) → five-stage ring oscillation → f ═ 10 KHz;
H2＝(Y3)&(～Y2) → seven-level ring oscillation → f ═ 7 KHz;
H3＝(Y3)&(Y2) → nine-stage ring oscillation → f ═ 4 KHz;
as can be seen, the frequency coarse adjustment range is 4KHz-15 KHz; it is composed ofIn (H)0、H1、H2And H3Four output signals output by the coarse frequency adjusting module respectively control the output of three-stage, five-stage, seven-stage and nine-stage ring oscillation; the counter outputs a high two-bit control signal Y3And Y2When the frequency is 00, 01, 10 and 11, three-stage, five-stage, seven-stage and nine-stage ring oscillation are respectively switched in, and the frequency is roughly adjusted. If the circuit needs to be accessed according to the maximum frequency point tracking circuit, the three-stage or five-stage ring oscillation is adopted, and the lower two bits of counting signals Y output by the counter1And Y0When the frequency of the input signal is 01, 10 and 11, the fine tuning frequency capacitance is C0，C1，C0、C1(ii) a If seven-stage or nine-stage ring oscillation is connected, the counter control signal Y with two lower bits1And Y0When the frequency of the input signal is 01, 10 and 11, the fine tuning frequency capacitance is C2，C3，C2、C3。
In this embodiment, the four-bit control signal H outputted by the coarse tuning frequency module0、H1、H2And H3Respectively connected with the outputs of the three-stage oscillation, the five-stage oscillation, the seven-stage oscillation and the nine-stage oscillation of the ring oscillator unit; the output signals of the second-stage oscillation, the third-stage oscillation, the fourth-stage oscillation and the fifth-stage oscillation of the ring oscillator unit are respectively S0、S1、S2And S3(ii) a The four-bit control signal L output by the fine frequency adjustment module0、L1、L2And L3Controlling four switches, namely a first switch, a second switch, a third switch and a fourth switch, wherein one end of the first switch is connected with S0The other end of the first switch is connected with a first capacitor C of the capacitor unit0One terminal of (1), a first capacitor C0The other end of the connecting rod is connected with the ground; one end of the second switch is connected with S1The other end of the second switch is connected with a second capacitor C of the capacitor unit1One terminal of (C), a second capacitor C1The other end of the connecting rod is connected with the ground; one end of the third switch is connected with S2The other end of the third switch is connected with a third capacitor C of the capacitor unit2One terminal of (C), a third capacitor C2The other end of the connecting rod is connected with the ground; first, theOne end of the four switches is connected with S3The other end of the fourth switch is connected with a fourth capacitor C of the capacitor unit3One terminal of (C), a fourth capacitor C3The other end of the connecting rod is connected with the ground; the control output frequency unit comprises four frequency units H0、H1、H2And H3The controlled switches are respectively a fifth switch, a sixth switch, a seventh switch and an eighth switch, one end of the fifth switch is connected with the S0The other end of the power supply is connected with power supply voltage; one end of the sixth switch is connected with S1The other end of the power supply is connected with power supply voltage; one end of the seventh switch is connected with S2The other end of the power supply is connected with power supply voltage; one end of the eighth switch is connected with S3The other end of the power supply is connected with power supply voltage; s0、H0Result of phase inversion and S1、H1The result of phase addition or, S2、H2Result of phase inversion and S3、H3And the phase result or the two phase results are re-phased or the output frequency f, f of the whole ring oscillator frequency generation module is obtained and input to the maximum power point tracking circuit for frequency modulation. The ring oscillator frequency generation module receives four-bit control signals from the coarse frequency adjustment module and the fine frequency adjustment module, the control signals are applied to the phase inverters and the fine capacitance adjustment switches with different access levels, different counting signals correspond to different frequencies, and the frequency requirement of maximum power point tracking in the maximum power point tracking circuit is met.
Referring to fig. 4, in the present embodiment, the oscillation frequency generated by the ring oscillator frequency generation module is input to the maximum power point tracking circuit for frequency modulation; the overall working process of the maximum power point tracking circuit is as follows: VT is the output voltage of the energy source, and 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 is 0000, the frequency output by the frequency generation module of the ring oscillator is 20kHz, three control signals CLK1, CLK2 and CLK3 which are slow in frequency and short in high level effective time are obtained after passing through the frequency division module, when the CLK1 signal is high level, the sampling signal of the circuit is effective, the sampling stage is started, the circuit is in an open loop stage, meanwhile, the two switches are closed under the action of the signal, and half of open loop voltage is stored into the capacitor under the partial pressure action of the sampling resistor; when the CLK2 signal is at high level, the circuit compares the signal effectively, the comparison stage is started, the circuit compares the input voltage with half of the sampled voltage, and the circuit inputs the comparison result into the counter to obtain the corresponding count signal. When CLK3 is high, the circuit count signal is active and the count signal is on, the circuit will receive the compare signal from the comparator and output a corresponding count signal to control the coarse and fine frequency tuning blocks in the frequency modulation circuit to generate a matched frequency.
Specifically, the VT of the maximum power point tracking circuit is connected to the boost converter circuit; in energy collection application, the energy source is greatly influenced by the change of environmental conditions such as temperature, air pressure and the like, so that the change range of internal resistance is very large, and the internal resistance of the energy source is equal to the input impedance of the booster circuit, namely R to ensure that the circuit obtains the maximum powereqIn the energy-harvesting step-up converter circuit, the output voltage Vout is RT>>Vin, where the equivalent impedance of the boost circuit to satisfy the maximum power condition can be given by the following equation:
Req＝RT＝8Lf；
wherein, L is the inductance value of the booster circuit, and f is the frequency output by 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 the equivalent input impedance of the boost conversion circuit, and the tracking of the maximum power point is realized.
The ring oscillator frequency modulation circuit provided by the embodiment of the invention has the following technical effects:
the frequency modulation circuit comprises a coarse adjustment frequency module, a fine adjustment frequency module and a ring oscillator frequency generation module, wherein the ring oscillator frequency generation module receives a coarse adjustment frequency signal output by the coarse adjustment frequency module and a fine adjustment frequency signal output by the fine adjustment frequency module and can generate stable oscillation frequency corresponding to a counting signal, so that the maximum power point is tracked; the invention has the advantages of small integration area, low power consumption, accurate frequency modulation, high stability and the like.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist 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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