Current type electric shock weeding device, control method and weeding system

Abstract

The invention discloses a current type electric shock weeding device, a control method and a weeding system. The device comprises a battery side voltage source; the primary side full-bridge inverter circuit is connected with the battery side voltage source; the voltage doubling circuit is used for generating high-voltage direct current output; the primary side of the transformer winding is connected with the midpoint of the primary side full-bridge inverter circuit, and the secondary side of the transformer winding is connected with the voltage doubling circuit; and the phase shift control module is configured to change the phase shift duty ratio phi = theta / pi by adjusting the phase shift angle theta and control the output current. The embodiment of the invention aims to provide a DC-DC converter which is free of ripples, has a constant-current characteristic and is simple to control for the field of electric shock weeding.

Description

Technical Field

[0001] The present application relates to a current-type electric shock weeding device, a control method and a weeding system, and belongs to the field of electric shock weeding. Background Art

[0002] Electric shock weeding, as an energy-saving, efficient and quick-result method, is particularly suitable for vegetatively propagated weeds. Compared with other physical weeding methods, electric shock weeding has obvious advantages, can specifically damage the roots and reproductive organs of weeds, and effectively prevent their regeneration. Its principle is to destroy the plant cell membrane through an electric signal, resulting in the loss and death of cell contents.

[0003] Currently, most of the common electric shock weeding devices on the market are voltage-type. If the voltage is set too high, although the weeds can be killed, the operating cost will increase and carbon emissions will increase due to energy redundancy; on the contrary, if the voltage is too low, the roots cannot be completely damaged due to insufficient current penetration, resulting in incomplete weeding and increased repeated operation costs. Summary of the Invention

[0004] In view of this, the present application provides a current-type electric shock weeding device, a control method and a weeding system. The embodiments of the present application aim to provide a DC-DC converter with ripple-free, constant current characteristics and simple control for the field of electric shock weeding.

[0005] In a first aspect of the embodiments of the present application, a current-type electric shock weeding device is disclosed, and the device includes:

[0006] A battery-side voltage source;

[0007] A primary full-bridge inverter circuit connected to the battery-side voltage source;

[0008] A voltage doubling circuit for generating a high-voltage DC output;

[0009] A transformer winding, the primary side of which is connected to the midpoint of the primary full-bridge inverter circuit, and the secondary side of which is connected to the voltage doubling circuit;

[0010] A phase-shift control module configured to:

[0011] Apply complementary preset duty cycle PWM drive signals to the first switch pair and the second switch pair of the primary full-bridge inverter circuit, wherein the drive signal of the second switch pair lags the drive signal of the first switch pair by a preset phase;

[0012] Apply complementary preset duty cycle PWM drive signals to the third switch pair and the fourth switch pair of the voltage doubling circuit, wherein the drive signal of the fourth switch pair lags the drive signal of the third switch pair by a preset phase, and the drive signal of the third switch pair lags the drive signal of the first switch pair by a phase-shift angle θ;

[0013] The output current is controlled by adjusting the phase-shift angle θ to change the phase-shift duty cycle φ = θ / π.

[0014] Further, the first switch pair is composed of the first and fourth switches connected diagonally, and the second switch pair is composed of the second and third switches connected diagonally; the third switch pair is composed of the fifth and seventh switches, and the fourth switch pair is composed of the sixth and eighth switches. Among them, the fifth and sixth switches are located on the left bridge arm, and the seventh and eighth switches are located on the right bridge arm.

[0015] Further, the primary full-bridge inverter circuit includes a first switch, a second switch, a third switch, a fourth switch, and a leakage inductance;

[0016] The positive pole of the battery-side voltage source is connected to the drains of the first switch and the second switch, and the negative pole of the battery-side voltage source is connected to the sources of the third switch and the fourth switch;

[0017] The source of the first switch is commonly connected to the drain of the third switch and the first end of the leakage inductance. The second end of the leakage inductance is connected to the same-name end of the primary winding, and the source of the second switch is commonly connected to the drain of the fourth switch and the opposite-name end of the primary winding.

[0018] Further, the voltage-doubling circuit includes:

[0019] A high-voltage-side load, with its first end connected to the first end of the third capacitor and its second end connected to the second end of the fifth capacitor;

[0020] A fifth switch, with its drain connected to the first end of the third capacitor and its source connected to the drain of the sixth switch and the first end of the second capacitor;

[0021] A sixth switch, with its source connected to the second end of the third capacitor;

[0022] A seventh switch, with its drain connected to the first end of the fifth capacitor and its source connected to the drain of the eighth switch;

[0023] An eighth switch, with its source connected to the second end of the fifth capacitor and its drain connected to the second end of the fourth capacitor;

[0024] The first end of the fifth capacitor is commonly connected to the second end of the third capacitor and the same-name end of the secondary winding. The second end of the second capacitor is commonly connected to the first end of the fourth capacitor and the opposite-name end of the secondary winding. The secondary winding is connected in parallel with the excitation inductance.

[0025] Further, the output current is as follows:

[0026]

[0027] where V L$V_{in}$ is the input voltage, $n$ is the transformer turns ratio, $f$ is the switching frequency, and $L$ is the leakage inductance value. $\varphi$ is the phase-shifted duty cycle.

[0028] Furthermore, the operating cycle of the device includes six consecutive stages:

[0029] Stage 1: The primary current freewheels through the body diodes of the first switch pair, and the secondary current freewheels through the body diodes of the fourth switch pair.

[0030] Stage 2: The primary current switches to the conduction path of the first switch pair, and the secondary current switches to the conduction path of the fourth switch pair.

[0031] Stage 3: The secondary current switches to freewheel through the body diode of the third switch pair.

[0032] Stage 4: The primary current switches to freewheel through the body diode of the second switch pair.

[0033] Stage 5: The primary current switches to the conduction path of the second switch pair, and the secondary current switches to the conduction path of the third switch pair.

[0034] Stage 6: The secondary current switches to freewheel through the body diode of the fourth switch pair.

[0035] Furthermore, the maximum transmission power is achieved when the phase-shifted duty cycle $\varphi = 50\%$.

[0036] The second aspect of the embodiments of the present application discloses a control method, which includes:

[0037] The processing unit detects the change of the high-voltage side load impedance in real time and dynamically adjusts the phase-shifted angle $\theta$ to keep the output current stable at a set value, where the set value is the breakdown current threshold preset according to the weed type.

[0038] The third aspect of the embodiments of the present application discloses an electric shock weeding system, which includes:

[0039] A current-mode electric shock weeding device;

[0040] A high-voltage electrode assembly, connected to the output end of the voltage multiplier circuit of the electric shock weeding device, including metal probes with adjustable spacing;

[0041] An impedance detection module, which calculates the load impedance by measuring the high-voltage side voltage and current and maps the impedance value to the adjustment amount of the phase-shifted angle $\theta$ to achieve closed-loop constant current control.

[0042] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0043] 1. The output voltage is proportional to the load resistance. That is, the larger the load resistance, the higher the output voltage, while the output current remains constant. As long as the input power is sufficient, a high-current output can be maintained regardless of the changes in weed species and growth stages.

[0044] 2. By adjusting the phase-shift duty cycle, precise control of the current magnitude is achieved, thus adapting to weeds at different growth stages and of different species, effectively enhancing the targeting and efficiency of electric shock weed control. This significantly reduces the energy consumption during the electric shock weed control process and provides strong technical support for environmental protection and energy conservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0046] Figure 1 It is a circuit diagram of a current-type electric shock weed control device provided by an embodiment of the present application.

[0047] Figure 2 It is a circuit diagram of a working mode 1 provided by an embodiment of the present application.

[0048] Figure 3 It is a circuit diagram of a working mode 2 provided by an embodiment of the present application.

[0049] Figure 4 It is a circuit diagram of a working mode 3 provided by an embodiment of the present application.

[0050] Figure 5 It is a circuit diagram of a working mode 4 provided by an embodiment of the present application.

[0051] Figure 6 It is a circuit diagram of a working mode 5 provided by an embodiment of the present application.

[0052] Figure 7 It is a circuit diagram of a working mode 6 provided by an embodiment of the present application.

[0053] Figure 8 It is a schematic diagram of a modulation waveform provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0055] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0056] In order to further improve the performance of the current-type electric shock weeding device, an innovative DC-DC converter design is proposed in this embodiment. The converter has characteristics such as high voltage conversion ratio (VCR), ripple-free, constant current output, and simple control. Its transmission power depends not only on circuit parameters such as equivalent inductance, switching frequency, and transformer turns ratio, but also is closely related to operating conditions such as input and output voltages and phase-shifted duty cycle. When the phase-shifted duty cycle is 50%, the converter reaches the maximum transmission power. The output voltage is proportional to the load resistance, and the output current remains constant. As long as the input power is sufficient, regardless of the type or growth stage of the weeds, the output current can remain constant, thus ensuring stable and reliable weeding effect. The specific implementation scheme is as follows:

[0057] Figure 1 A circuit diagram of a current-type electric shock weeding device provided in an embodiment of the present application. The current-type electric shock weeding device includes: a battery-side voltage source; a primary full-bridge inverter circuit connected to the battery-side voltage source; a voltage multiplier circuit for generating a high-voltage DC output; a transformer winding L 1k, the primary side is connected to the midpoint of the primary full-bridge inverter circuit, and the secondary side is connected to the voltage-doubling circuit; the phase-shift control module is configured to: apply complementary preset duty-cycle PWM drive signals to the first switch pair and the second switch pair of the primary full-bridge inverter circuit, where the drive signal of the second switch pair lags the drive signal of the first switch pair by a preset phase; apply complementary preset duty-cycle PWM drive signals to the third switch pair and the fourth switch pair of the voltage-doubling circuit, where the drive signal of the fourth switch pair lags the drive signal of the third switch pair by a preset phase, and the drive signal of the third switch pair lags the drive signal of the first switch pair by a phase-shift angle θ; change the phase-shift duty cycle by adjusting the phase-shift angle θ Control the output current.

[0058] In one embodiment, the first switch pair is composed of the first and fourth switches S1 and S4 connected diagonally, and the second switch pair is composed of the second and third switches S2 and S3 connected diagonally; the third switch pair is composed of the fifth and seventh switches Q1 and Q3, and the fourth switch pair is composed of the sixth and eighth switches Q2 and Q4. Among them, the fifth and sixth switches Q1 and Q2 are located on the left bridge arm, and the seventh and eighth switches Q3 and Q4 are located on the right bridge arm.

[0059] In this embodiment, the preset duty cycle is 0.5 duty cycle, and the preset phase is 180° phase.

[0060] In one embodiment, the primary full-bridge inverter circuit includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, and a leakage inductance L r ; the positive pole of the battery-side voltage source V L is connected to the drains of the first switch S1 and the second switch S2, and the negative pole of the battery-side voltage source V L is connected to the sources of the third switch S3 and the fourth switch S4; the source of the first switch S1, the drain of the third switch S3, and the first end of the leakage inductance L r are commonly connected, the second end of the leakage inductance L r is connected to the same-name end of the primary winding, and the source of the second switch S2, the drain of the fourth switch S4, and the different-name end of the primary winding are commonly connected.

[0061] In one embodiment, the voltage-doubling circuit includes: a high-voltage side load V H , the first end is connected to the first end of the third capacitor C b3 , and the second end is connected to the second end of the fifth capacitor C b4 ; a fifth switch Q1, the drain is connected to the first end of the third capacitor C b3 , the source is connected to the drain of the sixth switch Q2 and the second capacitor C b1The first end; the sixth switching transistor Q2, the source is connected to the third capacitor C b3 The second end; the seventh switching transistor Q3, the drain is connected to the fifth capacitor C b4 The first end, the source is connected to the eighth switching transistor C b4 The drain of; the eighth switching transistor Q4, the source is connected to the fifth capacitor C b4 The second end, the drain is connected to the fourth capacitor C b2 The second end; the fifth capacitor C b4 The first end of and the third capacitor C b3 The second end and the common terminal of the same name of the secondary winding are connected together, the second capacitor C b1 The second end of and the fourth capacitor C b2 The first end and the common terminal of the different name of the secondary winding are connected together, the secondary winding is in parallel with the exciting inductor L m In parallel.

[0062] In one embodiment, the output current is as follows:

[0063]

[0064] Wherein, V L Is the input voltage, n is the transformer turns ratio, f is the switching frequency, L is the leakage inductance value, Is the phase-shifted duty cycle.

[0065] It should be noted that by adjusting the phase-shifted duty cycle, the magnitude of the current can be precisely controlled, so as to adapt to weeds in different growth stages and types, effectively improving the targeting and efficiency of electric shock weeding.

[0066] In one embodiment, the working cycle of the device includes six consecutive stages:

[0067] Stage 1: The primary current continues to flow through the body diode of the first switching transistor pair, and the secondary current continues to flow through the body diode of the fourth switching transistor pair;

[0068] Stage 2: The primary current switches to the conduction path of the first switching transistor pair, and the secondary current switches to the conduction path of the fourth switching transistor pair;

[0069] Stage 3: The secondary current switches to the body diode of the third switching transistor pair to continue flowing;

[0070] Stage 4: The primary current switches to the body diode of the second switching transistor pair to continue flowing;

[0071] Stage 5: The primary current switches to the conduction path of the second switching transistor pair, and the secondary current switches to the conduction path of the third switching transistor pair;

[0072] Stage 6: The secondary current switches to the body diode of the fourth switching transistor pair to continue flowing. Specifically,

[0073] The first stage (t0 - t1): The operating state of the circuit is as Figure 2 shown. At time t0, the switching transistors S2 and S3 are turned off, and S1 and S4 are turned on. Since the current is negative at this time, the primary current continues to flow through diodes D1 and D4, and the secondary current still continues to flow through diodes Dq2 and Dq4. During this stage, the voltage across the equivalent inductor is V L +V H / 4n, and the current in inductor L r is:

[0074]

[0075] The second stage (t1 - t2): The operating state of the circuit is as Figure 3 shown. At time t1, the current changes from negative to positive. Since the switching transistors S1 and S4 have been turned on before, the primary current forms a loop through S1 and S4. In the secondary side, since the switching transistors Q2 and Q4 have been turned on, the current will form a loop through Q2 and Q4. At this time, the voltage across the equivalent inductor is still V L +V H / 4n, and the current in inductor L r is:

[0076]

[0077] The third stage (t2 - t3): The operating state of the circuit is as Figure 4 shown. At time t2, the switching transistors Q2 and Q4 are turned off, and Q1 and Q3 are turned on. Since the current is positive at this time, the secondary current will continue to flow through diodes Dq1 and Dq3. The state of the primary loop does not change, and the voltage across the equivalent inductor becomes V L -V H / 4n, and the current in inductor L r is:

[0078]

[0079] The fourth stage (t3 - t4): The operating state of the circuit is as Figure 5 shown. At time t3, the switching transistors S1 and S4 are turned off, and S2 and S3 are turned on. At this time, the current is still positive, and the primary current will flow through diodes D2 and D3. At this time, the voltage across the equivalent inductor becomes -V L -V H / 4n, and the current in inductor L r is:

[0080]

[0081] The fifth stage (t4 - t5): The operating state of the circuit is as Figure 6As shown. At time t4, the current changes from positive to negative. Since the switching transistors S2 and S3 have been turned on before, the primary current forms a loop through S2 and S3. On the secondary side, since the switching transistors Q1 and Q3 have been turned on, the current will form a loop through Q1 and Q3. The voltage across the equivalent inductor remains -V L -V H / 4n, inductor L r The current is:

[0082]

[0083] The sixth stage (t5 - t6): The operating state of the circuit is as Figure 7 shown. At time t5, the switching transistors Q1 and Q3 are turned off, and Q2 and Q4 are turned on. Since the current is negative at this time, the secondary current will freewheel through the diodes Dq2 and Dq4. The state of the primary loop does not change, and the voltage across the equivalent inductor becomes -V L +V H / 4n, inductor L r The current is:

[0084]

[0085] The current expression of inductor L within one cycle r is:

[0086]

[0087] In the above formula, let t0 = 0, then each moment can be expressed in turn as: t3 = T hs , t6 = 2T hs . Where K = V L / (V H / 4n), defined as the voltage transfer ratio. When the circuit is stable, according to the symmetry of the inductor current, i L (t0) = -i L (t3), i L (t2) = -i L (t5). Combining with the inductor current expression, the current expressions at each moment can be obtained as:

[0088]

[0089] Therefore, the average value of the input current can be expressed as:

[0090]

[0091] The corresponding input power can be expressed as:

[0092]

[0093] Without considering transmission losses, the transmission power is equal to the output power, and the expressions for the output voltage and output current can be obtained as follows:

[0094]

[0095] Among them, Figure 8 is Figures 2 - 7 the modulation waveform diagrams of each stage.

[0096] In one embodiment, taking the case of a load resistance close to that of weeds as an example, the key parameters are shown in Table 1.

[0097] Table 1 Key Parameter Table

[0098]

[0099] In one embodiment, a control method provided by an embodiment of the present application includes:

[0100] The processing unit detects the change in the high-voltage side load impedance in real time and dynamically adjusts the phase shift angle θ to keep the output current stable at a set value, which is the breakdown current threshold preset according to the weed type.

[0101] In one embodiment, an electric shock weeding system provided by an embodiment of the present application includes:

[0102] A current-type electric shock weeding device.

[0103] A high-voltage electrode assembly, connected to the output end of the voltage multiplier circuit of the electric shock weeding device, includes metal probes with adjustable spacing.

[0104] An impedance detection module calculates the load impedance by measuring the high-voltage side voltage and current, and maps the impedance value to the adjustment amount of the phase shift angle θ to achieve closed-loop constant current control.

[0105] In summary, the present invention proposes an innovative electric shock weeding technology. Compared with traditional electric shock weeding devices, it adopts a more efficient current-type design. By outputting a constant current, this device can efficiently kill weeds and achieve a thorough weeding effect. In the present invention, a voltage multiplier circuit is adopted on the high-voltage side, which can significantly increase the load voltage. The output voltage is affected by factors such as the input voltage, load resistance, leakage inductance, switching frequency, and phase shift duty cycle. Among them, the load resistance is proportional to the output voltage. At the same time, the current remains stable, and its value is related to the input voltage, phase shift duty cycle, transformer turns ratio, leakage inductance, and switching frequency.

[0106] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A current-type electric shock weeding device, characterized in that, Comprising: A battery-side voltage source; A primary full-bridge inverter circuit connected to the battery-side voltage source; A voltage multiplier circuit for generating a high-voltage DC output; A transformer winding, with its primary connected to the midpoint of the primary full-bridge inverter circuit and its secondary connected to the voltage multiplier circuit; A phase-shift control module configured to: Apply complementary preset duty-cycle PWM drive signals to the first switch pair and the second switch pair of the primary full-bridge inverter circuit, where the drive signal of the second switch pair lags the drive signal of the first switch pair by a preset phase; Apply complementary preset duty-cycle PWM drive signals to the third switch pair and the fourth switch pair of the voltage multiplier circuit, where the drive signal of the fourth switch pair lags the drive signal of the third switch pair by a preset phase, and the drive signal of the third switch pair lags the drive signal of the first switch pair by a phase-shift angle θ; Change the phase-shift duty ratio by adjusting the phase-shift angle θ Control the output current.

2. The current-type electric shock weeding device according to claim 1, characterized in that, The first switch pair is composed of the first and fourth switches connected diagonally, and the second switch pair is composed of the second and third switches connected diagonally; the third switch pair is composed of the fifth and seventh switches, and the fourth switch pair is composed of the sixth and eighth switches. Among them, the fifth and sixth switches are located on the left bridge arm, and the seventh and eighth switches are located on the right bridge arm.

3. The current-type electric shock weed control device according to claim 1, characterized in that The primary full-bridge inverter circuit includes a first switch, a second switch, a third switch, a fourth switch, and a leakage inductance; The positive pole of the battery-side voltage source is connected to the drains of the first switch and the second switch, and the negative pole of the battery-side voltage source is connected to the sources of the third switch and the fourth switch; The source of the first switch is commonly connected to the drain of the third switch and the first end of the leakage inductance, the second end of the leakage inductance is connected to the same-name end of the primary winding, and the source of the second switch is commonly connected to the drain of the fourth switch and the different-name end of the primary winding.

4. The current-type electric shock weeding device according to claim 1, characterized in that, The voltage multiplier circuit includes: A high-voltage side load, with its first end connected to the first end of the third capacitor and its second end connected to the second end of the fifth capacitor; A fifth switch, with its drain connected to the first end of the third capacitor and its source connected to the drain of the sixth switch and the first end of the second capacitor; A sixth switch, with its source connected to the second end of the third capacitor; A seventh switch, with its drain connected to the first end of the fifth capacitor and its source connected to the drain of the eighth switch; An eighth switch, with its source connected to the second end of the fifth capacitor and its drain connected to the second end of the fourth capacitor; The first end of the fifth capacitor is commonly connected to the second end of the third capacitor and the same-name end of the secondary winding, the second end of the second capacitor is commonly connected to the first end of the fourth capacitor and the different-name end of the secondary winding, and the secondary winding is connected in parallel with the exciting inductance.

5. The current-type electric shock weeding device according to claim 1, characterized in that, The output current is as follows: Among them, V L is the input voltage, n is the transformer turns ratio, f is the switching frequency, L is the leakage inductance value, is the phase-shifted duty cycle.

6. The current-type electric shock weeding device according to claim 1, characterized in that, The operating cycle of the device includes six consecutive stages: Stage 1: The primary current continues to flow through the body diodes of the first switch pair, and the secondary current continues to flow through the body diodes of the fourth switch pair; Stage 2: The primary current switches to the conduction path of the first switch pair, and the secondary current switches to the conduction path of the fourth switch pair; Stage 3: The secondary current switches to the body diodes of the third switch pair to continue flowing; Stage 4: The primary current switches to the body diodes of the second switch pair to continue flowing; Phase 5: The primary side current switches to the conduction path of the second switch pair, and the secondary side current switches to the conduction path of the third switch pair; Phase 6: The secondary side current switches to the body diode of the fourth switch pair for freewheeling.

7. The current-type electric shock weeding device according to claim 1, characterized in that When the phase-shift duty cycle reaches the maximum transmission power.

8. A control method for a current-type electric shock weeding device according to any one of claims 1-7, characterized in that Comprising: The processing unit detects the change of the high-voltage side load impedance in real time and dynamically adjusts the phase shift angle θ to make the output current stable at a set value, and the set value is the breakdown current threshold preset according to the weed type.

9. An electric shock weeding system, characterized in that, Comprising: The current-type electric shock weed control device according to any one of claims 1-7; A high-voltage electrode assembly, connected to the output end of the voltage multiplier circuit of the electric shock weed control device, comprising metal probes with adjustable spacing; An impedance detection module calculates the load impedance by measuring the high-voltage side voltage and current, and maps the impedance value to the adjustment amount of the phase shift angle θ to achieve closed-loop constant current control.

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