Self-excited charge pump system with inductive coupling

Abstract

A self-excited inductive charge pump system that employs inductive coupling to convert a low voltage in a range of tens of millivolts into a useful voltage higher than 1.2 volts and employs an ultra-low power source of several microwatts to tens of microwatts. Energy from the energy source is transmitted to the direct current receiver through the direct current source and the self-excited DC / DC converter. The DC source has at an input a self-excited generator connected to an output rectifier. The self-excited generator includes a first capacitor between the input terminals, a lower terminal of the first capacitor being connected to a system ground, and an upper terminal of the first capacitor being simultaneously connected to a primary winding and a secondary winding of the transformer. An output terminal of a secondary winding of the transformer is connected to an output terminal of the self-excited generator through a fourth capacitor, and an output terminal of a primary winding of the transformer is connected to a system ground through an N-JFET transistor and simultaneously to the system ground through an N-MOSFET transistor.

Description

Technical Field

[0001] The subject matter of the present invention is a self-excited charge pump system with inductive coupling, which is designed to convert a low voltage in the range of several tens of millivolts into a useful voltage, i.e., higher than 1.2 volts, using an ultra-low power source in the range of a few microwatts to several tens of microwatts. Background Art

[0002] The self-excited charge pump circuit known from Chinese Patent Application No. CN108667287 includes a boost power supply circuit for providing stable power supply, a pull-up circuit for processing input signals, and a pull-down circuit for processing input signals. According to the present invention, the charge pump can achieve self-excitation without the need for an external inductive element. Due to the absence of an inductive element, problems associated with inductive-based power sources are overcome, and electromagnetic interference is minimized. The circuit is not only highly efficient, has a simple circuit structure, occupies a small area, and has low power consumption, but also can operate efficiently under low voltage conditions.

[0003] The self-excited charge pump circuit known from Chinese Patent Application No. CN103607116 includes a switch unit and a control unit. The switch unit is appropriately connected to the nodes inside the auxiliary unit and is responsible for controlling the charging and discharging of the auxiliary unit. The control unit is used to control the switch unit to perform the required on / off operations based on the feedback voltage from the output terminal. This circuit eliminates the clock controller required by traditional charge pump circuits, does not require loop compensation, and can minimize the number of external components. In addition, the circuit also reduces the EMI noise of specific frequency components generated when the external clock controller operates, optimizing the circuit design. Electromagnetic interference is suppressed, making this self-excited charge pump circuit suitable for medical devices that are highly sensitive to noise, overcoming the deficiencies of the prior art.

[0004] Due to the very low "cold start" voltage of low-power energy sources, only in the range of several tens of millivolts to several hundreds of millivolts, standard circuits usually cannot wake up and operate within this voltage range. This limitation hinders the effective utilization of energy harvesting in microelectronics and low-voltage systems with micro-integrated energy harvesters. Examples of such applications include micro photovoltaic panels, low-voltage thermocouple utilization, vibration energy, and most importantly, radio wave energy. Summary of the Invention

[0005] The essence of the system according to the present invention lies in that the energy from the energy source is transmitted to the DC receiver through a DC source and a self-excited DC / DC converter. The DC source has a self-excited generator at the input end connected to an output rectifier. The self-excited generator includes a first capacitor between the input terminals, the lower terminal of the first capacitor is connected to the system ground, and the upper terminal of the first capacitor is simultaneously connected to the primary winding and the secondary winding of the transformer. The output terminals of the secondary winding of the transformer are connected to the output terminals of the self-excited generator through a fourth capacitor, and the output terminals of the primary winding of the transformer are connected to the system ground through an N-JFET transistor and simultaneously connected to the system ground through an N-MOSFET transistor. The gate of the N-JFET transistor is connected to the fourth capacitor via a second capacitor and a first resistor connected in parallel. The gate of the N-MOSFET transistor is connected to the fourth capacitor via a third capacitor, and the third capacitor is also connected to the point connecting the secondary winding of the transformer and the fourth capacitor. The output rectifier includes a second diode between the input terminals, and the second diode is connected to the output terminals of the output rectifier through a first diode. In addition, a fifth capacitor and a Zener diode are connected between the output terminals of the output rectifier and are in parallel with the first diode and the second diode. It is beneficial that both the first diode and the second diode are Schottky diodes.

[0006] Preferably, the self-excited DC / DC converter is connected to the self-excited generator through a voltage limiting circuit of the transistor, and the voltage limiting circuit is connected to the output rectifier.

[0007] Preferably, the voltage limiting circuit on the transistor is a low-pass AC filter or a high-pass AC filter. Advantageously, there is at least one thermocouple as the DC source. Advantageously, there is at least one semiconductor Peltier cell as the DC source. Advantageously, there is at least one photovoltaic cell as the DC source.

[0008] Preferably, there is at least one radio frequency energy harvesting circuit as the DC source, and the radio frequency energy harvesting circuit has an antenna, and the antenna is connected to a rectifier at the input end through an antenna impedance matching circuit, and the rectifier serves as the DC source for the harvested radio frequency energy.

[0009] Preferably, the rectifier is a half-wave rectifier or a full-wave rectifier.

[0010] The self-excited inductive charge pump circuit is characterized by extremely low start-up energy for the converter, and its energy harvesting comes from radio waves, photovoltaic cells, Peltier cells, and thermocouples. The start-up power of the converter is 3 μW at 50 mV, and no external battery is required for additional power supply. After start-up, the minimum power of the converter circuit is at least 1 μW. The converter circuit design is very simple, using a J-FET transistor based on an NMOSFET transistor as the converter driver, a transformer, four capacitors, a resistor, a Zener diode, and a dual Schottky diode. This makes the construction cost of the converter low. Despite the relatively low complexity, the circuit exhibits high efficiency, with an efficiency of up to 63% at a power level below 20 μW. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The subject matter of the present invention in the exemplary embodiments is depicted in the drawings as follows:

[0012] Figure 1 A self-excited inductive charge pump circuit is shown.

[0013] Figure 2 A self-excited inductive charge pump circuit equipped with a voltage limiting circuit is depicted.

[0014] Figure 3 A DC source in the form of a thermocouple is depicted.

[0015] Figure 4 A DC source in the form of a photovoltaic cell is depicted.

[0016] Figure 5 A radio frequency energy harvesting circuit is depicted.

[0017] Figure 6 A self-excited generator is depicted. Figure 7 An output rectifier is depicted. DETAILED DESCRIPTION

[0018] Example 1

[0019] The self-excited inductive charge pump circuit includes an energy source ES, and energy is transmitted from the energy source ES to a DC receiver DC via a DC source DCS and a self-excited DC / DC converter SE. The DC source DCS includes a self-excited generator SEG connected to an output rectifier OR at an input end. The self-excited generator SEG includes a first capacitor C1 between input terminals, the lower terminal of the first capacitor C1 is connected to a system ground, and the upper terminal of the first capacitor C1 is simultaneously connected to the primary winding and the secondary winding of a transformer Tr. The output terminal of the secondary winding of the transformer Tr is connected to the output terminal of the self-excited generator SEG through a fourth capacitor C4. In addition, the output terminal of the primary winding of the transformer Tr is connected to the system ground through an N-JFET transistor Q1 and is also connected to the system ground through another N-MOSFET transistor Q2. The gate of the N-JFET transistor Q1 is connected to the fourth capacitor C4 via a second capacitor C2 and a first resistor R1 connected in parallel. The gate of the N-MOSFET transistor Q2 is connected to the fourth capacitor C4 through a third capacitor C3, and the third capacitor C3 is also connected to a point connecting the secondary winding of the transformer Tr and the fourth capacitor C4. The output rectifier OR includes a second diode D2 between input terminals, and the second diode D2 is connected to the output terminal of the output rectifier OR through a first diode D1. In addition, a fifth capacitor C5 and a Zener diode DZ are connected between the output terminals of the output rectifier OR and are in parallel with the first diode and the second diode. In this solution, the energy source ES generates heat, and the DC source DCS is a thermocouple T. The self-excited inductive charge pump circuit utilizes the energy source in the form of a temperature difference generated at the thermocouple connection point. This temperature difference generates a potential difference and a direct current flow, which are then input to the protected converter to convert a voltage from 20 mV to 60 mV into a useful 2.5 V for powering low-power electronic circuits or charging a supercapacitor or a battery.

[0020] Embodiment 2

[0021] The structure of the self-excited inductive charge pump circuit is the same as that of the first embodiment, except that the self-excited DC / DC converter SEI includes the following self-excited generator SEG, and the self-excited generator SEG is connected to the output rectifier OR through a voltage limiting circuit on a transistor OVP. In addition, the voltage limiting circuit on the transistor OVP is a high-pass AC filter. This circuit utilizes the temperature difference generated at the joints of five thermocouples T to generate a potential difference and a direct current flow. This current is then input to the self-excited DC / DC converter SEI to convert a voltage from 120 mV to 250 mV into a useful 3.7 V voltage for powering low-power electronic circuits or charging a supercapacitor or a battery. In this solution, the thermocouples T are connected in series, and both the first diode D1 and the second diode D2 are Schottky diodes.

[0022] Embodiment 3

[0023] The structure of the self-excited inductive charge pump circuit is the same as that of the second embodiment, except that it utilizes the temperature difference generated at the junctions of eight thermocouples T connected in parallel. In this circuit, the supercapacitor or battery is charged at a power level in the range of 100 μW to 3 mW.

[0024] Embodiment 4

[0025] The structure of the self-excited inductive charge pump circuit is the same as that of the first to third embodiments, except that the semiconductor Peltier cell replaces the thermocouple T. The supercapacitor or battery is charged at a power level in the range of 10 μW to 1 mW.

[0026] Embodiment 5

[0027] The structure of the self-excited inductive charge pump circuit is the same as that of the first embodiment, except that the energy source ES emits light and the DC source DCS is a photovoltaic cell PV. The photovoltaic cell PV generates direct current when exposed to the light source, which is then input into the self-excited DC / DC converter SEI. The voltage is converted from 120 mV to 350 mV to a useful 3.3 V for powering low-power electronic circuits or charging a supercapacitor or battery.

[0028] Embodiment 6

[0029] The structure of the self-excited inductive charge pump circuit is the same as that of the first and fifth embodiments, except that the energy source ES emits light and the DC source DCS includes four photovoltaic cells PV connected in series. In addition, the self-excited DC / DC converter SEI includes the following self-excited generator SEG, which is connected to the output rectifier OR through a voltage limiting circuit on the transistor OVP. The voltage limiting circuit on the transistor OVP is a low-pass AC filter. This circuit uses a single photovoltaic cell PV as the energy source, which generates direct current when exposed to light. This current is then input into the self-excited DC / DC converter SEI, which converts the voltage from 400 mV to 1.2 V to an available 5 V voltage for powering low-power electronic circuits or charging a supercapacitor.

[0030] Embodiment 7

[0031] The structure of the self-excited inductive charge pump circuit is the same as that of the sixth embodiment, except that the energy source ES emits light and the DC source DCS includes nine photovoltaic cells PV connected in parallel.

[0032] Embodiment 8

[0033] The structure of the self-excited inductive charge pump circuit is the same as that of the first embodiment, except that the energy source ES emits radio frequency energy, and the DC source DCS is a radio frequency energy harvesting circuit. The circuit includes an antenna ANT, which is connected to an RC rectifier through an impedance matching circuit IM with an input impedance of Z. The RC rectifier serves as a DC source for the harvested radio frequency energy. The RC rectifier is a single-diode rectifier. The circuit utilizes radio waves in the frequency range of 27 MHz to 60 GHz. To absorb energy or radio waves, the circuit requires an additional radio wave harvesting circuit, which includes an antenna ANT tuned to the frequency of the radio frequency energy source, an impedance matching circuit IM, and an RC rectifier for converting radio frequency current into direct current. The rectified current is then input into a self-excited DC / DC converter SEI, which converts the voltage from 20 mV to 140 mV into a useful 2.5 V for powering low-power electronic circuits or charging a supercapacitor or a battery.

[0034] Embodiment 9

[0035] The structure of the self-excited inductive charge pump circuit is the same as that of the first and eighth embodiments, except that the rectifier RC is a full-wave rectifier. In addition, the self-excited DC / DC converter SEI includes the following self-excited generator SEG, which is connected to an output rectifier OR through a voltage limiting circuit on a transistor OVP. The voltage limiting circuit on the transistor OVP is a high-pass AC filter. This solution is equipped with three radio frequency energy harvesting circuits. The self-excited inductive charge pump circuit can utilize radio waves in the frequency range of 27 MHz to 60 GHz to harvest energy. To absorb the energy of radio waves, the circuit requires an additional radio wave harvesting circuit, which consists of an antenna ANT tuned to the frequency of the radio frequency energy source, an antenna impedance matching circuit IM, and an RC rectifier for converting radio frequency alternating current into direct current. The rectified current is then input into a self-excited DC / DC converter SEI, which converts the voltage from 20 mV to 140 mV into a useful 2.5 V for powering low-power electronic circuits or charging a supercapacitor or a battery.

[0036] The working principle of this circuit is to connect the drains and sources of the N-JFET Q1 and NMOSFET Q2 transistors between the primary winding of the transformer Tr and the ground. This configuration allows the primary winding to be connected to the ground, enabling current to flow through the primary winding. As the voltage on the primary winding increases, the voltage on the secondary winding of the transformer Tr also begins to rise, but the winding direction of the secondary winding is opposite to that of the primary winding. When the primary winding is connected to the ground, an induced current with the opposite direction and a voltage amplification factor equal to the turn ratio of the secondary winding to the primary winding is generated on the secondary winding. The induced current on the secondary winding flows through the second capacitor C2 and the third capacitor C3, causing the N-JFET Q1 and N-MOSFET Q2 transistors to "turn off". Therefore, the magnetically "charged" transformer Tr can only discharge through the fourth capacitor C4, whose capacitance is adjusted according to the operating frequency of the self-excited generator SEG, so that more than 90% of the energy accumulated on the secondary winding can be further transmitted to the output rectifier circuit OR equipped with the dual Schottky diodes D1 and D2. At the same time, a part of the charge accumulated on the secondary winding by the capacitors C2 and C3 enters the bases of the N-JFET Q1 and N-MOSFET Q2 transistors, connecting the primary winding to the ground again and repeating the described self-induction process. The circuit includes a resistor R1, which acts as a charge leakage point for the gate of the N-JFET Q1 transistor. When the energy input from the source is too high, this resistor will enter the saturation state and self-block. A key aspect of this circuit is that the N-JFET Q1 and N-MOSFET Q2 transistors are connected in parallel in a connection manner similar to that of a known DC converter through the second capacitor C2, the resistor R1, and the fourth capacitor C4. The difference is that the N-JFET Q1 transistor is used as the trigger of the converter because the minimum voltage required to start the operation in this configuration is 50 mV, and the power required for the start-up circuit is 3 uW. After the start-up operation, the N-MOSFET Q2 transistor will be responsible for switching the voltage on the secondary winding, which enables the converter to achieve an efficiency of approximately 65% when powered by a power of approximately 20 uW and a voltage of 30 mV. The minimum operating threshold of the converter is a power of 1 uW and a voltage of 20 mV. If there is no N-JFET Q1 transistor in the circuit, the minimum operating threshold will be 400 mV, and the power required to start the self-excitation process is approximately 50 uW. Additionally, during the operation of the self-excited inductive converter, it is necessary to control the voltage on the secondary winding of the transformer Tr, which is achieved by implementing a voltage limiting circuit in the form of an AC filter on the transistor OVP to prevent the gate voltages of the N-JFET Q1 and N-MOSFET Q2 transistors from exceeding the allowable values.

[0037] The self-excited inductive charge pump circuit is equipped with a DC source DCS, which is a thermocouple (T), and alternatively a Peltier cell, a photovoltaic cell, or a circuit for collecting radio frequency energy. The DC source DCS in the form of a thermocouple (T) and alternatively a Peltier cell is particularly suitable for wireless seismic sensors or strain gauge sensors in mines for detecting collapses or deformations (signaling danger), and wireless explosive gas sensors in mines for detecting the concentration of dangerous gases. The DC source DCS in the form of a photovoltaic cell can be installed in a remote control unit of a television, a wireless thermometer, a wireless strain gauge sensor for monitoring structural deformations, an electronic price display in a store, or a portable positioning system (such as AirTags and similar devices). The DC source DCS in the form of a radio frequency energy harvesting system for absorbing (collecting) radio waves in at least one radio frequency range from 50 Hz to 100 GHz, which is equipped with an antenna ANT, an antenna impedance matching circuit IM, and an RC rectifier, can be installed in the following: a wireless strain gauge sensor for monitoring the deformation of wind turbine rotor blades, an ultra-low power wireless headset, walls, tables, and other low-power time control devices, very low-power or ultra-low-power IoT devices, small wireless computer peripherals (such as computer mice, computer keyboards, touchpads, or electronic pens with very low or ultra-low power consumption), wireless tags for pallets / crates to determine their location in a warehouse, wireless tags for pallets / crates to determine their location in a warehouse, wireless sensors for industrial ICS / SCADA infrastructures and supporting industrial automation processes and security, remote control devices for automatic doors, smart door locks (including central locks in the automotive industry), blinds, light-shielding curtains, and other home and office automation components, remote control keys and smart key systems, control and measurement devices for large, medium, and small power warehouses, personal medical diagnostic devices using self-excited charge pump circuits, anywhere for internal battery / supercapacitor charging, and many other applications.

[0038] List of reference signs in the drawings

[0039] ANT - Antenna,

[0040] C1 - First capacitor, C2 - Second capacitor, C3 - Third capacitor, C4 - Fourth capacitor, C5 - Fifth capacitor,

[0041] D1 - First diode, D2 - Second diode, DC - DC receiver, DZ - Zener diode, DCS - DC source, ES - Energy source, IM - Antenna impedance matching circuit, OR - Output rectifier, OVP - Voltage limiting circuit of transistor, PV - Photovoltaic cell, R1 - First resistor, RC - Rectifier, Q1 - N - JFET transistor, Q2 - N - MOSFET transistor, SEI - Self - excited DC / DC converter, SEG - Self - excited generator, T - Thermocouple, TR - Transformer, Z - Input impedance.

Claims

1. A self-excited charge pump system with inductive coupling, characterized in that Energy from an energy source (ES) is transmitted to a DC receiver (DC) through a DC source (DCS) and a self-excited DC / DC converter (SEI), wherein the DC source (DCS) has a self-excited generator (SEG) at an input end connected to an output rectifier (OR), wherein the self-excited generator (SEG) has a first capacitor (C1) connected between input terminals, a lower terminal of the first capacitor is connected to a system ground, and an upper terminal of the first capacitor is simultaneously connected to a primary winding and a secondary winding of a transformer (Tr), wherein output terminals of the secondary winding of the transformer (Tr) are connected to output terminals of the self-excited generator (SEG) through a fourth capacitor (C4), and output terminals of the primary winding of the transformer (Tr) are connected to the system ground through an N-JFET transistor (Q1) and simultaneously connected to the system ground through an N-MOSFET transistor (Q2), wherein a gate of the N-JFET transistor (Q1) is connected to a terminal connecting the secondary winding of the transformer (Tr) and the fourth capacitor (C4) through a second capacitor (C2) and a first resistor (R1) connected in parallel, and a gate of the N-MOSFET transistor (Q2) is connected to the terminal connecting the secondary winding of the transformer (Tr) and the fourth capacitor (C4) through a third capacitor (C3), the output rectifier (OR) is connected with a second diode (D2) at an input end, the second diode is connected to an output terminal of the output rectifier (OR) through a first diode (D1), in addition, a fifth capacitor (C5) and a Zener diode (DZ) are connected between the output terminals of the output rectifier (OR) and are in parallel with the first diode (D1) and the second diode (D2), wherein the first diode (D1) and the second diode (D2) are advantageously Schottky diodes.

2. The system according to claim 1, wherein The self-excited DC / DC converter (SEI) has the following self-excited generator (SEG), and the self-excited generator is connected to an output rectifier (OR) through an overvoltage protection circuit (OVP) of a transistor.

3. The system according to claim 2, wherein The overvoltage protection circuit (OVP) of the transistor is a low-pass AC filter.

4. The system according to claim 2, wherein The overvoltage protection circuit (OVP) of the transistor is a high-pass AC filter.

5. The system according to claim 1, wherein The DC source (DCS) is at least one thermocouple (T).

6. The system according to claim 1, wherein The DC source (DCS) is at least one semiconductor Peltier cell.

7. The system according to claim 1, wherein The DC source (DCS) is at least one photovoltaic cell (PV).

8. The system according to claim 1, wherein The DC source (DCS) is at least one radio frequency energy harvesting system, and the radio frequency energy harvesting system has an antenna (ANT), and the antenna is connected to a rectifier (RC) through an antenna impedance matching circuit (IM) at an input end, and the rectifier serves as a DC source for the harvested radio frequency energy.

9. The system according to claim 7, wherein The rectifier (RC) is a half-wave rectifier.

10. The system according to claim 7, wherein The rectifier (RC) is a full-wave rectifier.

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