Environment energy self-sufficiency DC-DC converter for expanding load of rectification circuit

Abstract

The invention discloses an environment energy self-sufficiency DC-DC converter for expanding the load of a rectifying circuit, which is applied to the field of environment energy collection and aims to solve the problems that the existing structure for improving the output load resistance of the rectifying circuit through a DC-DC circuit needs to depend on an external power supply (such as a lithium battery and the like) to supply power; the development of a full-passive wide-load rectifying circuit is greatly hindered; according to the environment energy self-sufficient DC-DC converter, solar energy, heat energy and vibration energy in the environment are used for supplying power, a lithium battery and other power sources in a traditional DC-DC converter are removed, the applicability of a wide-load rectifying circuit is improved, the service life of a wireless sensing node powered by RF energy is prolonged, and the cost of the wireless sensing node powered by the RF energy is reduced. Meanwhile, the two stages of OPAs are adopted to form the oscillating circuit, so that the power consumption of the existing oscillating circuit is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of environmental energy collection, and in particular relates to an energy self-sufficient DC-DC converter. Background Art

[0002] Ambient energy harvesting refers to obtaining and storing energy from the environment, such as solar energy, thermal energy, mechanical energy, and electromagnetic energy. Different ambient energies require different conversion mechanisms. Ambient energy harvesting technology can provide a continuous power supply solution for low-power devices, allowing the target to actively or passively obtain energy from the environment to power itself. It is expected to replace batteries to improve energy efficiency and the service life of low-power devices. Ambient electromagnetic energy has the characteristics of all-weather, all-round, and all-time. It is the "ideal power source" for the Internet of Things (IoT) system and has been widely studied by universities and research institutions.

[0003] The environmental electromagnetic energy harvesting system consists of a receiving antenna / array, a rectifier circuit unit / rectifier circuit array and a power management unit. The rectifier circuit in the environmental electromagnetic energy harvesting system converts the environmental electromagnetic energy into DC power and is a key component of the environmental electromagnetic energy harvesting system. The classic rectifier circuit structure consists of an input matching circuit / input filter circuit, a rectifier device (usually a transistor or a rectifier diode, etc.), a DC filter circuit and a load resistor. Due to the nonlinear characteristics of the rectifier diode, the output load resistor of the traditional rectifier circuit is usually a fixed value, which greatly limits the application range of the rectifier circuit.

[0004] In order to improve the applicability of the rectifier circuit, impedance compression networks, wide load impedance matching networks and DC-DC circuits are applied to the rectifier circuit to increase the output load resistance range of the rectifier circuit. Impedance compression and impedance matching networks usually compress the large impedance variation range of the rectifier circuit into a small variation range to increase the output load resistance variation range of the rectifier circuit, but impedance compression and wide load impedance matching networks have limited expansion range of the load resistance of the rectifier circuit, and changes in input power and operating frequency will reduce the output load resistance range of the rectifier circuit. The DC-DC circuit can effectively expand the output load resistance range of the rectifier circuit by using its stable control of output voltage and current and adjustment of output impedance, and is not affected by the operating frequency. However, the currently widely used structures that aim to increase the output load resistance of the rectifier circuit through the DC-DC circuit all rely on external power supplies (such as lithium batteries, etc.) for power supply, which greatly hinders the development of fully passive wide load rectifier circuits. In addition, the efficiency and effective working time of the rectifier circuit are limited by the battery capacity. The energy harvesting circuit used in the wireless sensing node often fails due to the difficulty in replacing the battery in time, resulting in the failure of the wireless sensor network.

[0005] The existing impedance compression can achieve impedance compression by connecting two branches in parallel with a microstrip line with a sum of lengths of 180° and an electrical length difference of 2θ (0°<θ<90°), so that the imaginary parts of the input impedances of the two branches can be offset and the real parts tend to be stable. The impedance compression network is as follows: Figure 1 In the traditional rectifier circuit, the change of the optimal load resistance of the rectifier circuit will change the input impedance of the rectifier circuit, thereby reducing the matching performance and rectification efficiency of the rectifier circuit. In order to reduce the influence of the change of the load resistance of the rectifier circuit on the input impedance of the rectifier circuit, an impedance compression network is introduced into the rectifier circuit, as shown in FIG. Figure 1 As shown in (b), the load resistance variation range of the rectifier circuit can be expanded to a certain extent.

[0006] When the terminal load resistance of the traditional rectifier circuit deviates from the optimal load resistance, the rectification efficiency will drop sharply, which greatly reduces the DC output power of the rectifier circuit and also reduces the application scope of the rectifier circuit. For this reason, DC impedance matching circuits are applied to rectifier circuits. Common DC impedance matching circuits include boost, buck, and buck-boost DC-DC converters, which can effectively expand the output load resistance of the rectifier circuit and keep the rectification efficiency of the rectifier circuit above 60%. DC-DC converters are usually composed of inductors, switching elements, diodes and capacitors. Boost DC-DC converters such as Figure 2 (a) is shown. The wide load range rectifier circuit composed of a DC-DC converter is shown in Figure 2 As shown in (b), the DC-DC converter requires active devices to generate control signals to adjust the input / output resistance change relationship, so an external DC power supply is required, which greatly reduces the applicability of the rectifier circuit. The output voltage of the rectifier circuit is used as a DC power supply, but because the DC output voltage of the rectifier circuit is unstable and will change with changes in input power, etc., in order to provide a stable DC power supply for the DC-DC converter, an additional voltage stabilizing circuit must be introduced. The voltage stabilizing circuit will reduce the efficiency of the rectifier circuit. At the same time, the DC-DC oscillation circuit is Figure 2 As shown in (c), the oscillation circuit is mainly composed of an OPA (Operational Amplifier) ​​and an LTC6906 high-frequency oscillator and its peripheral circuits. The power consumption of integrated high-frequency oscillation chips such as LTC6906 is usually high, reaching 50uW. Since the ambient RF energy harvesting circuit is usually low-power, the solution of combining OPA with a high-frequency oscillation chip to generate a control signal is difficult to apply to the ambient energy harvesting circuit.

[0007] The wide load rectifier circuit based on the impedance compression network has a small load resistance expansion range and is affected by the input signal frequency and power. The DC-DC converter can greatly expand the output load resistance range of the rectifier circuit, but a signal with a certain duty cycle is required to control the on and off of the DC-DC conversion switch to achieve DC impedance matching. The control signal generation method includes an oscillation circuit composed of a low-power microcontroller or OPA combined with a high-frequency oscillation chip. They are all active devices and require a DC power supply to work. Existing DC power supplies are usually lithium batteries. The effective working time of the wide load rectifier circuit is limited by the battery capacity, which greatly limits the applicability of the rectifier circuit, and waste batteries will pollute the environment. At the same time, the oscillator composed of OPA and high-frequency oscillation chips such as LTC6906 in the oscillation circuit has high power consumption.

[0008] In summary, impedance compression technology, wide load output resistance impedance matching technology and DC-DC converters have expanded the output load resistance range of the rectifier circuit to a certain extent, but the above technologies all have certain limitations. Impedance compression technology and wide load output resistance impedance matching technology are affected by the operating frequency and input power of the rectifier circuit, and the DC-DC converter requires an external power supply. Therefore, in order to expand the output load resistance range of the rectifier circuit and improve the applicability of the rectifier circuit, it is of great significance to propose an environmental energy self-sufficient DC-DC converter. Summary of the invention

[0009] In view of the problems that the load range of the impedance compression network is small, the DC-DC conversion requires an external power supply, and the existing oscillation circuit has high power consumption, the present invention proposes an environmental energy self-sufficient DC-DC converter that expands the load of the rectifier circuit. The device does not require battery power, and uses environmental energy such as temperature difference and solar energy to power the DC-DC converter, which greatly improves the applicability and service life of the rectifier circuit. At the same time, the present invention uses a two-stage low-power operational amplifier to form an oscillation circuit, which greatly reduces the system power consumption and improves the system efficiency. The environmental energy self-sufficient DC-DC converter for expanding the load of the rectifier circuit proposed in the present invention does not require an external battery power supply, reduces the manual interference caused by power supply, reduces maintenance costs, and has the characteristics of being green, clean and pollution-free. At the same time, a two-stage OPA is used to form an oscillation circuit, which reduces the power consumption of the oscillation circuit.

[0010] The technical solution adopted by the present invention is: an environmental energy self-sufficient DC-DC converter for expanding the load of a rectifier circuit, comprising: an energy collection circuit, an oscillation circuit, a MOS tube, a diode, a first capacitor C 0 、Load R L , the second capacitor C in ,inductance;

[0011] The energy collection circuit is used to convert environmental energy into direct current power; the oscillation circuit converts direct current power into a high-frequency signal, the high-frequency signal is input into the gate of the MOS tube, the source of the MOS tube is grounded, the drain of the MOS tube is connected to the anode of the diode, the cathode of the diode is connected to the first capacitor C 0 The first end is connected to the first capacitor C 0 The second end is grounded and the load R L The first end is connected to the cathode of the diode, and the load R L The second end is grounded, the first end of the inductor is connected to the second capacitor C in The first end is connected to the second capacitor C in The second end is grounded; the second capacitor C in The first terminal input voltage V in Positive electrode, second capacitor C in The second terminal input voltage V in negative electrode.

[0012] The oscillation circuit adopts a two-stage op amp structure. The first stage op amp generates a low-frequency signal which is then input into the second stage op amp. The second stage op amp converts the low-frequency signal into a high-frequency signal.

[0013] According to the actual application scenario, the operating frequency, input power and rectifier circuit structure of the rectifier circuit are selected, and ADS is used to optimize the design of a single-frequency high-efficiency rectifier circuit and determine the optimal load R L .

[0014] According to the optimal load R L , determine the frequency and duty cycle of the oscillation circuit.

[0015] According to the DC-DC converter operating voltage V DC , the output voltage of the designed ambient energy harvesting circuit is V DC .

[0016] Beneficial effects of the present invention: The environmental energy self-sufficient DC-DC converter of the present invention utilizes solar energy, thermal energy and vibration energy in the environment to supply power, removes power sources such as lithium batteries in traditional DC-DC converters, improves the applicability of wide-load rectifier circuits, extends the service life of wireless sensor nodes powered by RF energy, and reduces the cost of wireless sensor nodes powered by RF energy. At the same time, a two-stage OPA is used to form an oscillation circuit, which greatly reduces the power consumption of existing oscillation circuits. The present invention aims to study a set of wide-load passive rectifier circuits to improve the applicability of rectifier circuits, which is beneficial to promoting the development of environmental wireless energy collection, microwave energy transmission and other technologies, and promoting the practical application of a new generation of low-carbon green energy and information systems such as environmental wireless energy collection self-powered sensors and networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Impedance networks and their applications;

[0018] Among them, (a) is an impedance compression network, and (b) is a wide load rectifier circuit composed of an impedance compression network;

[0019] Figure 2 DC-DC converters and their applications;

[0020] Among them, (a) is the circuit diagram of the DC-DC converter, (b) is the wide load rectification circuit composed of the DC-DC converter, and (c) is the principle diagram of the oscillation circuit;

[0021] Figure 3 Block diagram of an environmental energy self-sufficient DC-DC converter for expanding the load of the rectifier circuit;

[0022] Figure 4 This is the schematic diagram of the environmental energy self-sufficient DC-DC converter;

[0023] Figure 5 is the TEG open circuit voltage V G Relationship with temperature difference △T;

[0024] Figure 6 This is a curve showing how the efficiency of the rectifier circuit changes with load resistance. DETAILED DESCRIPTION

[0025] To facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further explained below with reference to the accompanying drawings.

[0026] The present invention proposes a circuit block diagram of an environmental energy self-sufficient DC-DC converter with an expanded rectifier circuit load. Figure 3 As shown, it is composed of a radio frequency source, a rectifier circuit, a DC-DC converter, a load resistor, an oscillation circuit, and an ambient energy collection circuit.

[0027] The environmental energy harvesting circuit converts solar energy, thermal energy, vibration energy, etc. into DC power, which is then converted into the operating voltage of the DC-DC converter after passing through the DC synthesis network and DC storage / control network, continuously powering the DC-DC circuit.

[0028] The design process of the environmental energy self-sufficient DC-DC converter with extended rectifier circuit load proposed by the present invention is as follows:

[0029] 1) Design a single-frequency high-efficiency rectifier circuit. According to the operating frequency, input power and rectifier circuit structure of the rectifier circuit, use ADS simulation software to optimize the optimal load resistance value R opt ,like Figure 2 As shown;

[0030] 2) According to the optimal load resistance value R opt, determine the frequency, duty cycle and related parameters of the oscillation circuit, so that the DC-DC converter input resistance R in =R opt ;

[0031] 3) Determine the DC-DC converter operating voltage V DC , design an ambient energy harvesting circuit and set its DC output voltage to V DC ;

[0032] 4) Jointly optimize the wide load rectifier circuit and the energy self-sufficient DC-DC converter so that the input resistance of the DC-DC converter satisfies equation (1). From equation (1), it can be seen that R in The change is only related to the control signal parameters and inductance parameters, and is not related to the load resistance R L The load variation range of the rectifier circuit is effectively expanded.

[0033] Compared with the traditional impedance compression network, the structure proposed in the present invention has a larger load range. At the same time, the DC-DC conversion circuit removes the traditional high-frequency oscillator LTC6909 and the like, and adopts a low-power OPA to form an oscillator, which greatly reduces the power consumption of the system. In addition, compared with the rectifier circuit composed of a traditional DC-DC converter, the present invention adopts ambient energy for power supply and does not require an external power supply, which effectively improves the applicability of the rectifier circuit.

[0034] Environmental energy self-sufficient DC-DC converters such as Figure 4 As shown, it is composed of an inductor, a diode, a MOS tube, a capacitor, an oscillator, and an energy collection circuit. Figure 4 In the case of V in <<V O , the DC-DC converter operates in discontinuous conduction mode, and its input impedance R in The expression is as follows:

[0035]

[0036] Among them, V in Represents the input voltage of the DC-DC converter, V O represents the output voltage of the DC-DC converter, L is the inductance value, D h and T h are the duty cycle and period of the high frequency oscillator, D l is the duty cycle of the low-frequency oscillator. Based on the analysis and simulation of the DC-DC converter efficiency, L and D are adjusted. h 、T h , D l The value of the DC-DC converter input impedance R in . From the DC-DC input impedance Rin It can be seen from the expression that R in With input power, load resistance R L The value of is irrelevant, so adjust the relevant parameters to make R in =R opt A wide load impedance rectifier circuit can be realized.

[0037] Figure 4 In the embodiment, the oscillation circuit is composed of two-stage op amps. The first stage op amp generates a low-frequency signal and then inputs it into the second stage. The second stage converts the low-frequency signal into a high-frequency signal, thereby controlling the DC-DC switching frequency. According to measurements, the output frequency of the oscillation circuit can be changed by changing the peripheral circuit of the two-stage OPA; and the power consumption of the oscillation circuit of the two-stage op amp structure used in this embodiment is 28uW, which is 50% lower than that of the existing oscillation circuit.

[0038] Taking the thermoelectric generator as an example, the energy collection current is tested and the relationship between the open circuit voltage and temperature difference of the thermoelectric generator TEG1-241-6.0-4 is shown in the following test data: Figure 5 As shown by Figure 5 The output power of the thermoelectric generator under a small temperature difference can be calculated by the internal resistance of the thermoelectric generator (TEG1-241-6.0-4 is 5.8-6.4Ω at room temperature). The energy collection chip in the energy collection circuit can use the MCRY07-125Q chip, which has a starting voltage of 23mV and an energy conversion efficiency of about 70%. When the temperature difference is 1°C, it can provide energy for the DC-DC converter.

[0039] Figure 6 The wide load rectifier circuit of the present invention is tested. in =10dBm, frequency f 0 =1.8GHz, load resistance R opt =1kΩ, the efficiency of the rectifier circuit is 55%. Compared with the rectifier circuit without a DC-DC converter, the efficiency of the rectifier circuit drops sharply as the load resistance increases. The rectifier circuit with a DC-DC converter of the present invention has a load range of 1kΩ-50kΩ, and as the load resistance increases, the overall efficiency of the rectifier circuit considering the loss of the DC-DC converter has almost no change, and compared with the rectifier circuit without considering the loss of the DC-DC converter, the overall efficiency decrease is not obvious. It can be seen that the technical solution of the present invention effectively expands the load resistance range of the rectifier circuit while ensuring a certain rectifier circuit efficiency. At the same time, the present invention only verifies the energy of the environmental energy self-sufficient DC-DC converter to expand the load impedance. In order to improve the system efficiency, the efficiency of the rectifier circuit can be further improved.

[0040] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. An environmental energy self-sufficient DC-DC converter for expanding the load of a rectifier circuit, characterized in that: include: Energy collection circuit, oscillation circuit, MOS tube, first diode, first capacitor C0, load R L , the second capacitor C in ,inductance; The energy collection circuit is used to convert environmental energy into direct current power; the oscillation circuit converts direct current power into a high-frequency signal, the high-frequency signal is input into the gate of the MOS tube, the source of the MOS tube is grounded, the drain of the MOS tube is connected to the positive electrode of the first diode, the negative electrode of the first diode is connected to the first end of the first capacitor C0, the second end of the first capacitor C0 is grounded, and the load R L The first end is connected to the cathode of the first diode, and the load R L The second end is grounded, the first end of the inductor is connected to the second capacitor C in The first end is connected to the second capacitor C in The second end is grounded; the second capacitor C in The first terminal input voltage V in Positive electrode, second capacitor C in The second terminal input voltage V in negative electrode.

2. The environmental energy self-sufficient DC-DC converter for expanding the load of the rectifier circuit according to claim 1, characterized in that: The oscillation circuit includes a high-frequency oscillator and a low-frequency oscillator; The low frequency oscillator generates a low frequency signal according to the DC power output by the energy collection circuit, and the high frequency oscillator converts the low frequency signal into a high frequency signal.

3. The environmental energy self-sufficient DC-DC converter for expanding the load of the rectifier circuit according to claim 2, characterized in that: When V in <<V O , the DC-DC converter operates in discontinuous conduction mode, and its input impedance R in The expression is as follows: Among them, << is the much less than symbol, V O represents the output voltage, L is the inductance value, D h and T h are the duty cycle and period of the high frequency oscillator, D l is the duty cycle of the low frequency oscillator.

4. The environmental energy self-sufficient DC-DC converter for expanding the load of the rectifier circuit according to claim 3, characterized in that: Also includes: RF source, rectifier circuit; the rectifier circuit converts the RF signal generated by the RF source into a DC voltage as the input voltage V in ; Optimal load resistance value R for rectifier circuit opt Equal to the input impedance R in .

5. The environmental energy self-sufficient DC-DC converter for expanding the load of the rectifier circuit according to claim 4, characterized in that: The low-frequency oscillator is implemented by an operational amplifier, which is referred to as a first operational amplifier. The peripheral circuit of the first operational amplifier includes: a first resistor R1, a second resistor R2, a first resistor R3, a second resistor R4, a fifth resistor R5, a third capacitor C1, and a second diode; the first end of the first resistor R1 is connected to the DC power supply output by the energy collection circuit, the second end of the first resistor R1 is connected to the first end of the second resistor R2, the second end of the second resistor R2 is grounded, the first end of the second resistor R2 is connected to the positive input end of the first operational amplifier, the first end of the third resistor R3 is connected to the positive input end of the first operational amplifier, the second end of the third resistor R3 is connected to the output end of the first operational amplifier, the negative input end of the first operational amplifier is grounded through the third capacitor C1, the first end of the fourth resistor R4 is connected to the negative input end of the first operational amplifier, the second end of the fourth resistor R4 is connected to the output end of the first operational amplifier, the first end of the fifth resistor R5 is connected to the negative input end of the first operational amplifier, the second end of the fifth resistor R5 is connected to the cathode of the second diode, and the anode of the second diode is connected to the output end of the first operational amplifier.

6. The environmental energy self-sufficient DC-DC converter for expanding the load of the rectifier circuit according to claim 5, characterized in that: The high-frequency oscillator is implemented by an operational amplifier, which is referred to as a second operational amplifier. The peripheral circuit of the second operational amplifier includes: a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, and a third capacitor C2; a first end of the sixth resistor R6 is connected to the output end of the first operational amplifier, a second end of the sixth resistor R6 is connected to the positive input end of the second operational amplifier, a first end of the seventh resistor R7 is connected to the second end of the sixth resistor R6, a second end of the seventh resistor R7 is grounded, a first end of the eighth resistor R8 is connected to the positive input end of the second operational amplifier, a second end of the eighth resistor R8 is connected to the output end of the second operational amplifier, a first end of the ninth resistor R9 is connected to the negative input end of the second operational amplifier, a second end of the ninth resistor R9 is connected to the output end of the second operational amplifier, the negative input end of the second operational amplifier is grounded through the third capacitor C2, and the output end of the second operational amplifier is connected to the gate of the MOS tube.

Images