Reference voltage source control circuit and control method suitable for micro energy harvesting system

Abstract

The present invention provides a reference voltage source control circuit and control method suitable for a micro-energy harvesting system. The control circuit includes a reference voltage source, a low-leakage sample-and-hold switch, and a reusable logic unit. Based on the operating characteristics of the micro-energy harvesting system in normal operating mode and standby mode, different control strategies are adopted for the voltage reference source to achieve low power consumption. Specifically, in normal operating mode, the operating time of the reference voltage source is controlled based on control signals from the lower and upper side transistors in the main circuit BOOST. In standby mode, the reference voltage source is controlled by reusing the MPPT clock, thereby significantly reducing the average power consumption of the reference voltage source and improving the efficiency of the micro-energy harvesting system. Furthermore, the present invention achieves low power consumption and good temperature characteristics of the reference voltage source without using large resistors, thus saving chip area.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, and in particular relates to a reference voltage source control circuit and a control method thereof suitable for a micro energy harvesting system. Background Art

[0002] The Internet of Things (IoT) era has brought about an explosion of big data and sensors. How to power a large number of IoT sensing nodes is a huge challenge. Energy harvesting, which converts micro-energy in the environment into electrical energy to achieve self-powering of sensing nodes, has become a feasible and effective solution.

[0003] Achieving self-powered energy through solar energy harvesting systems has become a mature solution. This system converts ambient light energy into electrical energy through solar panels, photovoltaic cells and other solar energy harvesting sensors to power sensing nodes. The architecture of the micro energy harvesting system is as follows: Figure 1 As shown in the figure, since the output voltage of the photovoltaic cell is low and is a DC voltage, the main circuit in the system adopts the Boost converter topology, in which the upper tube M P and lower side tube M N is the power tube, S N and S P The system periodically drives the power tube to step up the input voltage to obtain the desired output voltage to power the load, and at the same time, uses the maximum power point tracking (MPPT) circuit to collect energy from the input source with maximum efficiency. In micro-energy harvesting systems, due to the low input power of the system, strict requirements are placed on the power consumption of the circuit. As a working circuit module required in all modes of the system, the reference voltage source is particularly important for achieving low power consumption of its circuit. The reference voltage source can provide a reference voltage for the output feedback circuit and convert the output feedback voltage V FB The reference voltage V REF_HS and V REF_LS Compare and set the system working mode according to the results, such as Figure 2 As shown, the working mode is divided into normal working mode and standby mode. In normal working mode, the system module works normally and generates a driving signal S N and S P The Boost circuit works so that the energy from the input source can be transferred to the output terminal, and the output capacitor voltage rises until V REF_HS In standby mode, only some modules are working, and the output capacitor discharges to the load until its voltage drops to V REF_LS .

[0004] In order to achieve low power consumption of the reference voltage source, there are two main technical solutions: (1) using large resistors in the bandgap reference voltage source, see the literature [Wang L, Zhan C, Lin J, et al. "A 0.9-V22.7-ppm / ℃ Sub-Bandgap Voltage Reference with Single BJT and Two Resistors." IEEE International Symposium on Circuits and Systems IEEE, 2021]; (2) using a reference source based on a MOS tube structure working in the subthreshold region, see the literature [Zhang H, Liu X, Zhang J, et al. "A Nano-WattMOS-Only Voltage Reference With High-Slope PTAT Voltage Generators." IEEE Transactions on Circuits and Systems II: Express Briefs (2017): 1-5]. For technical solution (1), a large resistor is used in the process of achieving low power consumption, and the large resistor will occupy a large part of the chip area, greatly increasing the cost of the chip; for technical solution (2), a MOS tube working in the subthreshold region is used instead of a triode when generating the reference voltage. Since it works in the subthreshold region, its current is small, but the temperature characteristics and voltage accuracy performance of the reference voltage generated by it are reduced. Summary of the Invention

[0005] In view of the above, the present invention provides a reference voltage source control circuit and a control method thereof suitable for a micro energy harvesting system, which can greatly reduce the average power consumption of the reference voltage source.

[0006] A reference voltage source control circuit suitable for a micro-energy harvesting system includes a reference voltage source, two inverters INV1 and INV2, an AND gate AND1, two switches S1 and S2, and a capacitor C1. The input end of INV1 is connected to the drive signal of the lower tube in the micro-energy harvesting system, the output end of INV1 is connected to the first input end of AND1, the second input end of AND1 is connected to the input end of INV2 and is connected to the drive signal of the upper tube in the micro-energy harvesting system, the output end of AND1 generates a signal EN for controlling the on and off of S1, one end of S1 is connected to the power supply voltage, the other end of S1 is connected to the power supply end of the reference voltage source, the enable end of the reference voltage source is connected to the signal EN, the output end of INV2 generates a signal for controlling the on and off of S2, the output end of the reference voltage source is connected to one end of S2 and generates a high reference voltage V REF_HS, the other end of S2 is connected to one end of C1 and outputs the reference voltage V REF , the other end of C1 is grounded.

[0007] Furthermore, the switch S2 is a low leakage switch.

[0008] Furthermore, the above-mentioned reference voltage source control circuit is suitable for normal working mode of the micro energy harvesting system.

[0009] The control method of the reference voltage source control circuit is to control switches S1 and S2 according to the on-time of the lower and upper tubes in each switching cycle, thereby controlling the working time of the reference voltage source. When the lower tube is turned on, switch S1 is turned on and the reference voltage source starts to work; when the lower tube is turned off and the upper tube is turned on, switches S1 and S2 are turned on at the same time and the generated reference voltage V REF Perform sampling and holding; when the upper tube is disconnected, the reference voltage source stops working.

[0010] A reference voltage source control circuit suitable for a micro energy harvesting system includes a reference voltage source, a delay unit, an AND gate AND2, two switches S3 and S4, and a capacitor C2, wherein the first input end of AND2 is connected to the input end of the delay unit and is connected to the MPPT clock signal in the micro energy harvesting system, the output end of the delay unit is connected to the second input end of AND2, one end of S3 is connected to the power supply voltage, the other end of S3 is connected to the power supply end of the reference voltage source, the enable end of the reference voltage source is connected to the MPPT clock signal, and the on and off of S3 is also controlled by the MPPT clock signal, the output end of AND2 generates a signal Sample for controlling the on and off of S4, the output end of the reference voltage source is connected to one end of S4 and generates a low reference voltage V REF_LS , the other end of S4 is connected to one end of C2 and outputs the reference voltage V REF , the other end of C2 is grounded.

[0011] Furthermore, the switch S4 is a low leakage switch.

[0012] Furthermore, the above-mentioned reference voltage source control circuit is suitable for the standby mode of the micro energy harvesting system.

[0013] The control method of the reference voltage source control circuit uses the MPPT clock signal to control the working time of the reference voltage source. When the MPPT clock signal is high, the reference voltage source works and generates a signal Sample according to the MPPT clock signal to generate a reference voltage V REF Perform sampling and holding; when the MPPT clock signal is low, the reference voltage source stops working.

[0014] Unlike existing solutions, this invention eliminates the need for large resistors, saving chip area, while still achieving low power consumption and good temperature characteristics for the reference voltage source. Furthermore, based on the characteristics of the micro-energy harvesting system's normal operating mode and standby mode, the invention employs different control strategies without requiring additional control circuitry. While maintaining the basic functionality of the reference voltage source, the invention further reduces its average power consumption by rationally adjusting its operating and sleep times, thereby improving the efficiency of the micro-energy harvesting system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the overall architecture of the micro energy harvesting system.

[0016] Figure 2 Schematic diagram of the working mode switching of the micro energy harvesting system.

[0017] Figure 3 This is a schematic diagram of the control circuit structure of the reference voltage source in the normal working mode of the micro energy harvesting system in Example 1 of the present invention.

[0018] Figure 4 This is a schematic diagram of the control signal timing of the reference voltage source in the normal working mode of the micro energy harvesting system.

[0019] Figure 5 This is a schematic diagram of the control circuit structure of the reference voltage source in the standby mode of the micro energy harvesting system in Example 2 of the present invention.

[0020] Figure 6 This is a schematic diagram of the control signal timing of the reference voltage source in the standby mode of the micro energy harvesting system.

[0021] Figure 7 Schematic diagram of the simulated waveform of the reference voltage output by the reference voltage source control circuit of the present invention at different temperatures. DETAILED DESCRIPTION

[0022] In order to describe the present invention more specifically, the technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] like Figure 3 As shown, this embodiment provides a control circuit for a voltage reference source in a normal working mode of a micro energy harvesting system, including a reference voltage source, two inverters INV1 and INV2, an AND gate AND1, a switch S1, a low leakage switch S2, and a capacitor C1. Among them: the input of the inverter INV1 is the drive signal S N , the output is connected to the input of AND gate AND1, and the other input of AND1 is connected to the driving signal SP Connection, switch S1 is controlled by the output of the AND gate, and the input of INV2 is S P , an output of the reference voltage source V REF_HS Connected to the left side of the low leakage switch S2, switch S2 is controlled by the output of INV2, one end of the capacitor C1 is connected to the right side of the switch S2 as the output, and also serves as the output reference voltage V REF Its control strategy mainly controls switches S1 and S2 according to the on-time of the Boost lower-side tube and upper-side tube in each switching cycle, thereby controlling the working time of the reference voltage source. When the lower-side tube is turned on, switch S1 is turned on and the reference voltage source starts working; when the lower-side tube is turned off and the upper-side tube is turned on, switches S1 and S2 are turned on at the same time, and the generated reference voltage is sampled and held. When the upper-side tube is turned off, the reference voltage source stops working.

[0025] When the system is in normal working mode, the Boost converter works in DCM (discontinuous conduction mode). Compared with the working cycle T of the micro energy harvesting system, SYS , power tube M N The working time t in each cycle N and M P Working time t P In this mode, the driving signal S N and S P Drive the switch tubes S1 and S2 to control the working state of the reference voltage source, and at the same time generate the reference voltage V REF_HS The voltage is sampled and stored in capacitor C1. The control signal is as follows: Figure 4 As shown, the specific work flow is: when S N When the power level is high, the power tube M N The reference voltage source starts to work and enters the startup phase first. N Disconnect, M P When conducting, S1 and S2 are closed at the same time, and the V generated by the reference voltage source REF_HS Sampling is performed; when M N Disconnect, M P When disconnected, S1 and S2 are disconnected, and the reference voltage source stops working. At this time, the voltage across capacitor C1 is V REF_HS , the output feedback voltage V FB The voltage is compared with this voltage to determine whether the system enters standby mode. Assume that the quiescent current of the reference voltage source is I Q , the average current under this control strategy can be expressed as:

[0026]

[0027] In this mode, the average current of the reference voltage source is mainly determined by the duty cycle of the power tube working time in the system switching cycle.

[0028] Example 2

[0029] like Figure 5 As shown, this embodiment provides a voltage reference source control circuit in the standby mode of a micro energy harvesting system, including a reference voltage source, an MPPT clock circuit, a delay unit, an AND gate AND2, a switch S3, a low leakage switch S4 and a capacitor C2, wherein: the clock signal CLK generated by the MPPT clock circuit MPPT The inputs of control switches S3 and AND2 are respectively signals CLK MPPT and CLK MPPT Delay t d The low leakage switch S4 is controlled by AND gate AND2. The left side of the S4 switch is connected to an output signal generated by the reference voltage source, and the right side is connected to capacitor C2. Its control strategy uses the MPPT clock in the system to control the working time of the reference voltage source. When CLK MPPT When the signal is high, the reference voltage source works and the reference voltage source works according to the CLK MPPT Generate Sample signal, sample and hold the generated reference voltage. MPPT When it is low, the reference voltage source stops working.

[0030] This embodiment reuses the MPPT clock in standby mode without adding any additional control circuits. When the system is in standby mode, the CLK generated by the MPPT clock MPPT The signal controls the working state of the reference voltage source, and the Sample signal controls the reference voltage V generated by the sample-and-hold switch. REF_LS The sample is sampled and held in capacitor C2, and its control signal is as follows Figure 6 As shown, the specific work flow is as follows: When CLK MPPT When it is high, S3 is closed and the reference voltage source enters a period of time t d After the startup phase, the signal Sample becomes high level, and S3 and S4 are closed at the same time, which generates V REF_LS The sampling and holding is performed until the sampling signal Sample becomes low, S3 and S4 are disconnected, and the reference voltage source stops working. At this time, the voltage across the capacitor C2 is V REF_LS , the output feedback voltage V FB The voltage is compared with the control voltage to determine whether the system has entered the normal operating mode. The average current under this control strategy can be expressed as:

[0031]

[0032] Where: t DUTY It is the high level time in one cycle.

[0033] To keep the sampling capacitor on V REF To improve the accuracy, it is necessary to control the ΔV between each two samples. Therefore, the values ​​of the sampling capacitors C1 and C2 in the two control circuits are also crucial, which is mainly related to the sampling period. The sampling period T in standby mode MPPT In the normal working mode, the sampling period is T SYS The time duration is in the microsecond range, so the size of C2 is several thousand times that of C1. In the specific circuit implementation, in order to reduce the leakage of the sampling capacitor, the sample-hold switches S3 and S4 are low-leakage switches.

[0034] Figure 7 The reference voltage waveform generated by the reference voltage source control circuit of the present invention at -40°C to 125°C is simulated. Calculation shows that the temperature coefficient of the circuit is 14.6ppm, which is significantly improved compared to the existing solution (2) described in the background art. The static power consumption of the reference voltage source under this control strategy is also simulated. First, under normal working conditions, as shown in Table 1:

[0035] Table 1

[0036] <![CDATA[I Q ]]> <![CDATA[t N ]]> <![CDATA[t P ]]> <![CDATA[T SYS ]]> Duty cycle <![CDATA[I AVG ]]> 110nA 302ns 60ns 3.5μs 10.3％ 11.3nA

[0037] Assume that the static power consumption of a reference voltage source is 110nA, and the working cycle of the micro energy harvesting system is T SYS 3.5μs, power tube M N The on-time t N 302ns, power tube M P The on-time t P The reference voltage source has an operating duty cycle of only 10.3% during one system operating cycle, and its final average power consumption is calculated to be 11.3 nA, which greatly reduces power consumption.

[0038] When the system is in standby mode, as shown in Table 2:

[0039] Table 2

[0040] <![CDATA[I Q ]]> <![CDATA[t DUTY ]]> <![CDATA[T MPPT ]]> Duty cycle <![CDATA[I AVG ]]> 110nA 15μs 60ms 0.25％ 0.275nA

[0041] Similarly, the static power consumption of a reference voltage source is 110nA. The high-level time of the MPPT clock in standby mode is 15μs, and its sampling period is 60ms. The duty cycle of the reference voltage source in one sampling period is only 0.25%. After calculation, the final average current is only 0.275nA, which greatly reduces power consumption.

[0042] Table 3 shows the comparison results of the average current of the reference voltage source in two working modes under the control strategy of the present invention and the static current of the existing scheme (1) and scheme (2) in the background technology.

[0043] Table 3

[0044] Solution (1) Solution (2) The present invention 73nA 23nA 11.3nA / 0.275nA

[0045] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It is apparent that those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without requiring creative effort. Therefore, the present invention is not limited to the above embodiments. Any improvements or modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. A reference voltage source control circuit suitable for a micro energy harvesting system, characterized in that: The system includes a reference voltage source, two inverters INV1 and INV2, an AND gate AND1, two switches S1 and S2, and a capacitor C1, wherein the input end of INV1 is connected to the drive signal of the lower tube in the micro energy harvesting system, the output end of INV1 is connected to the first input end of AND1, the second input end of AND1 is connected to the input end of INV2 and is connected to the drive signal of the upper tube in the micro energy harvesting system, the output end of AND1 generates a signal EN to control the on and off of S1, one end of S1 is connected to the power supply voltage, the other end of S1 is connected to the power supply end of the reference voltage source, the enable end of the reference voltage source is connected to the signal EN, the output end of INV2 generates a signal to control the on and off of S2, the output end of the reference voltage source is connected to one end of S2 and generates a high reference voltage V REF_HS , the other end of S2 is connected to one end of C1 and outputs the reference voltage V REF , the other end of C1 is grounded.

2. The reference voltage source control circuit according to claim 1, wherein: The switch S2 is a low leakage switch.

3. The reference voltage source control circuit according to claim 1, wherein: The reference voltage source control circuit is suitable for the normal working mode of the micro energy harvesting system.

4. The control method of the reference voltage source control circuit according to any one of claims 1 to 3, wherein: According to the on-time of the lower and upper tubes in each switching cycle, switches S1 and S2 are controlled to control the working time of the reference voltage source. When the lower tube is turned on, switch S1 is turned on and the reference voltage source starts to work; when the lower tube is turned off and the upper tube is turned on, switches S1 and S2 are turned on at the same time and the generated reference voltage V REF Perform sampling and holding; when the upper tube is disconnected, the reference voltage source stops working.

5. A reference voltage source control circuit suitable for a micro energy harvesting system, characterized in that: The system includes a reference voltage source, a delay unit, an AND gate AND2, two switches S3 and S4, and a capacitor C2. The first input end of AND2 is connected to the input end of the delay unit and is connected to the MPPT clock signal in the micro energy harvesting system. The output end of the delay unit is connected to the second input end of AND2. One end of S3 is connected to the power supply voltage, and the other end of S3 is connected to the power supply end of the reference voltage source. The enable end of the reference voltage source is connected to the MPPT clock signal. At the same time, the on and off of S3 is also controlled by the MPPT clock signal. The output end of AND2 generates a signal Sample to control the on and off of S4. The output end of the reference voltage source is connected to one end of S4 and generates a low reference voltage V REF_LS , the other end of S4 is connected to one end of C2 and outputs the reference voltage V REF , the other end of C2 is grounded.

6. The reference voltage source control circuit according to claim 5, wherein: The switch S4 is a low leakage switch.

7. The reference voltage source control circuit according to claim 5, wherein: The reference voltage source control circuit is suitable for the standby mode of a micro energy harvesting system.

8. The control method of the reference voltage source control circuit according to any one of claims 5 to 7, wherein: The MPPT clock signal is used to control the working time of the reference voltage source. When the MPPT clock signal is high, the reference voltage source works and generates a signal Sample according to the MPPT clock signal to generate a reference voltage V REF Perform sampling and holding; when the MPPT clock signal is low, the reference voltage source stops working.

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