Reference voltage source control circuit suitable for micro-energy acquisition system and control method of reference voltage source control circuit

Abstract

The invention provides a reference voltage source control circuit suitable for a micro-energy acquisition system and a control method of the reference voltage source control circuit, the control circuit comprises a reference voltage source, a low-leakage sampling and holding switch and a reusable logic unit, according to the working characteristics of the micro-energy acquisition system in a normal working mode and a standby mode, different control strategies are adopted for the voltage reference source, so that low power consumption of the voltage reference source is realized, that is, the working time of the reference voltage source is controlled according to control signals of a lower side tube and an upper side tube in a main circuit BOOST in a normal working mode; in the standby mode, the reference voltage source is controlled by multiplexing the MPPT clock, so that the average power consumption of the reference voltage source can be greatly reduced, and the efficiency of the micro energy acquisition system is improved. In addition, under the conditions that a large resistor is not adopted and the chip area is saved, the low power consumption and the good temperature characteristic of the reference voltage source are still achieved.

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 suitable for a micro energy collection system and a control method thereof. Background Art

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

[0003] Self-powering through solar energy harvesting system has become a mature solution. The system converts the light energy in the environment into electrical energy through solar panels, photovoltaic cells and other solar energy harvesting sensors to power the sensing nodes. 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 the lower tube M N is the power tube, S N and S P The system periodically drives the power tube to work and boosts the input voltage to obtain the desired output voltage to power the load. At the same time, the maximum power point tracking (MPPT) circuit is used to collect energy from the input source with maximum efficiency. In the micro-energy harvesting system, due to the low input power of the system, strict requirements are placed on the power consumption of the circuit. The reference voltage source is a working circuit module required in all modes of the system, so it is particularly important to achieve low power consumption of the 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 a normal working mode and a standby mode. In the 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 end, and the output capacitor voltage rises until V REF_HS In standby mode, only some modules work, 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 existing 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 a 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 comprises a reference voltage source, two inverters INV1 and INV2, an AND gate AND1, and two switches S 1 and S 2 And the capacitor C 1 The input end of INV1 is connected to the driving 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 connected to the driving signal of the upper tube in the micro energy harvesting system, and the output end of AND1 generates a signal EN to control S 1 The on-off, S 1 One end is connected to the power supply voltage, S 1The other end of INV2 is connected to the power supply end of the reference voltage source, the enable terminal of the reference voltage source is connected to the signal EN, and the output end of INV2 generates a signal to control S 2 The output of the reference voltage source is connected to S 2 One end is connected to generate a high reference voltage V REF_HS , S 2 The other end of the 1 One end is connected to the reference voltage V REF , C 1 The other end is grounded.

[0007] Furthermore, the switch S 2 Use low leakage switches.

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

[0009] The control method of the reference voltage source control circuit is to control the switch S according to the turn-on time of the lower tube and the upper tube in each switching cycle. 1 and S 2 , thereby controlling the working time of the reference voltage source. When the lower tube is turned on, the switch S 1 When the lower tube is turned off and the upper tube is turned on, the switch S 1 and S 2 At the same time, the 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 collection system comprises a reference voltage source, a delay unit, an AND gate AND2, and two switches S 3 and S 4 And the capacitor C 2 , wherein the first input end of AND2 is connected to the input end of the delay unit and connected to the MPPT clock signal in the micro energy harvesting system, and the output end of the delay unit is connected to the second input end of AND2, S 3 One end is connected to the power supply voltage, S 3 The other end is connected to the power supply end of the reference voltage source, and the enable end of the reference voltage source is connected to the MPPT clock signal. 3 The on / off of the switch is also controlled by the MPPT clock signal. The output of AND2 generates a signal Sample to control S 4 The output of the reference voltage source is connected to S 4 One end is connected to generate a low reference voltage V REF_LS , S 4 The other end of the 2 One end is connected to the reference voltage VREF , C 2 The other end is grounded.

[0011] Furthermore, the switch S 4 Use low leakage switches.

[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 is to use the MPPT clock signal to control the working time of the reference voltage source. When the MPPT clock signal is at a high level, 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 at a low level, the reference voltage source stops working.

[0014] Different from the prior art solutions, the present invention does not use large resistors and saves chip area, while still achieving low power consumption and good temperature characteristics of the reference voltage source. At the same time, according to the characteristics of the normal working mode and the standby mode in the micro energy harvesting system, the present invention selects different control strategies without generating additional control circuits, while realizing the basic functions of the reference voltage source, and further reduces the average power consumption of the reference voltage source by reasonably adjusting its working and sleep time, 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 working mode switching of micro energy harvesting system.

[0017] Figure 3 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 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 7The figure is a schematic diagram of a simulation waveform of a 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 in conjunction with the accompanying drawings and specific implementation methods.

[0023] Example 1

[0024] like Figure 3 As shown, this embodiment provides a control circuit of 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, and a switch S 1 , a low leakage switch S 2 And a capacitor C 1 Among them: the input of inverter INV1 is the driving 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 S P Connection, switch S 1 Controlled by the output of the AND gate, the input of INV2 is S P , an output of the reference voltage source V REF_HS With low leakage switch S 2 The left side connection, switch S 2 Controlled by the output of INV2, capacitor C 1 One end is used as output and the switch S 2 The right side is connected and serves as the output reference voltage V REF The control strategy mainly controls the switch S according to the opening time of the Boost lower and upper tubes in each switching cycle. 1 and switch S 2 This controls the working time of the reference voltage source. When the lower tube is turned on, the switch S 1 When the lower tube is turned off and the upper tube is turned on, the switch S 1 , S 2 They are turned on at the same time and the generated reference voltage is sampled and held. When the upper tube is disconnected, 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 in each cycle is t N and M P Working time P In this mode, the driving signal SN and S P Driving switch tube S 1 and S 2 To control the working state of the reference voltage source, and at the same time to generate the reference voltage V REF_HS The voltage is sampled and stored in capacitor C 1 The control signal is as follows: Figure 4 As shown, the specific workflow is: when S N When the power tube M is high, N The switch tube S 1 Closed, the reference voltage source starts to work and first enters the startup phase; and when M N Disconnect, M P When conducting, S 1 and S 2 At the same time, the reference voltage source V REF_HS Sampling is performed; when M N Disconnect, M P When disconnected, S 1 and S 2 Disconnect, the reference voltage source stops working. At this time, the capacitor C 1 The voltage across the terminals is V REF_HS , the output feedback voltage V FB The voltage is compared with the reference 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 the micro energy harvesting system, including a reference voltage source, an MPPT clock circuit, a delay unit, an AND gate AND2, and a switch S 3 , a low leakage switch S 4 And a capacitor C 2 , where: the clock signal CLK generated by the MPPT clock circuit MPPT Control switch S 3 , AND2's inputs are the signal CLK MPPT And CLK MPPT Delay t d After the signal, the low leakage switch S 4Controlled by AND gate AND2, S 4 The left side of the switch is connected to an output signal generated by a reference voltage source, and the right side is connected to a capacitor C 2 Its control strategy uses the MPPT clock in the system to control the working time of the reference voltage source. MPPT When the signal is high, the reference voltage source works and according to CLK MPPT Generate a Sample signal to sample and hold the generated reference voltage. MPPT When it is low, the reference voltage source stops working.

[0030] In this embodiment, the MPPT clock is reused in standby mode without adding other 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 stored in the capacitor C 2 The control signal is as follows: Figure 6 As shown, the specific working process is as follows: When CLK MPPT When it is high, S 3 Closed, the reference voltage source enters a period of time t d After the startup phase, the signal Sample becomes high level. 3 and S 4 At the same time, the generated V REF_LS The sampling and holding is performed until the sampling signal Sample becomes low level, S 3 and S 4 Disconnect, the reference voltage source stops working, and the capacitor C 2 The voltage across the terminals is V REF_LS , the output feedback voltage V FB The voltage is compared 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, we need to control the ΔV between each two samples. Therefore, the sampling capacitor C in the two control circuits 1 and C 2 The value of is also very important, which is mainly related to the sampling period. The sampling period T in standby mode MPPTIn normal working mode, the sampling period is T SYS is in microseconds, so C 2 The size is about C 1 In the specific circuit implementation, in order to reduce the leakage of the sampling capacitor, the sampling and holding switch S 3 and S 4 A low leakage switch was selected.

[0034] Figure 7 The reference voltage simulation waveform generated by the reference voltage source control circuit of the present invention at -40°C to 125°C is shown in Table 1. The temperature coefficient of the circuit is 14.6ppm, which is significantly improved compared with the existing solution (2) described in the background technology. The static power consumption of the reference voltage source under the control strategy is 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 a 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 the 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 a sampling period is only 0.25%. After calculation, the final average current is only 0.275nA, which greatly reduces power consumption.

[0042] Table 3 is a comparison result 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 to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art to the present invention based on the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A reference voltage source control circuit suitable for a micro energy harvesting system, characterized in that: The invention comprises 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 driving signal of the lower tube in the micro energy collection 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 connected to the driving signal of the upper tube in the micro energy collection 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, characterized in that: The switch S2 is a low leakage switch.

3. The reference voltage source control circuit according to claim 1, characterized in that: 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, characterized in that: According to the turn-on time of the lower tube and the upper tube 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 comprises 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 connected to the MPPT clock signal in the micro energy collection 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-off of S3 is also controlled by the MPPT clock signal, the output end of AND2 generates a signal Sample to control the on-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, characterized in that: The switch S4 is a low leakage switch.

7. The reference voltage source control circuit according to claim 5, characterized in that: The reference voltage source control circuit is suitable for the standby mode of the micro energy collection system.

8. The control method of the reference voltage source control circuit according to any one of claims 5 to 7, characterized in that: The MPPT clock signal is used to control the working time of the reference voltage source. When the MPPT clock signal is at a high level, 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 at a low level, the reference voltage source stops working.

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