A driving circuit for plant lighting

Abstract

To address the technical problem that existing driving schemes fail to function properly in high-frequency chopping applications or cannot achieve high-precision LED current, this invention proposes a driving circuit for plant lighting, comprising a constant voltage source and an adjustable circuit. The first terminal of the constant voltage source is connected to the first terminal of the load. The adjustable circuit includes: an adjustable voltage source, the first terminal of which is connected to the second terminal of the constant voltage source; a chopper switch, the first terminal of which is connected to the second terminal of the adjustable voltage source, and the second terminal of which is connected to the second terminal of the load; and a control circuit, the first terminal of which is connected to the first terminal of the load, the second terminal of which is connected to the third terminal of the chopper switch, and the third terminal of which is connected to the third terminal of the adjustable voltage source. The control circuit controls the chopper switch and also controls the voltage of the adjustable voltage source according to the load current signal, so that the sum of the voltage of the adjustable voltage source and the voltage of the constant voltage source matches the target voltage.

Description

Technical Field

[0001] The present invention relates to the field of circuit electronics, and in particular to a driving circuit for plant lighting. Background Art

[0002] In the field of plant lighting, it is often used Figure 1 The driving circuit shown is used to power the LED lamp for plant lighting. Switch S0 acts as a chopper switch, so that the DC power received by the LED lamp is high-frequency chopped DC power. The current waveform is as follows Figure 2 In order to enable plants to achieve better photosynthesis or to use lighting electricity more efficiently, the frequency f of the chopper switch S0 is usually above MHz.

[0003] exist Figure 1 In the driving circuit, the constant voltage source Q0 of the previous stage outputs a DC power with a constant voltage amplitude. In order to stabilize the brightness of the LED lamp, it is necessary to connect a current limiting module A1 in series in the LED lamp branch. The circuit structure diagram of the current limiting module A1 is shown in FIG. Figure 3 As shown, the current of the LED lamp is detected in real time through the detection resistor R0, and the detection value I LED By comparing with the preset value Iref, the impedance at both ends of the current limiting module is controlled to make the current of the LED lamp branch equal to the preset value.

[0004] When Figure 1 When the circuit is used in the field of plant lighting, the operating frequency f of the chopper switch belongs to the high frequency field, that is, above megahertz, that is, the on-time of the chopper switch is very short. In the short on-time, the current limiting module needs to adjust faster to make the LED current equal to the preset value, but the adjustment speed of the existing current limiting module cannot be adjusted within the chopping time above megahertz. Therefore, the existing driving scheme cannot be used in the field of plant lighting, which will cause the LED lamp current to be unable to stabilize at the predetermined amplitude, which will make the LED lamp brightness unstable, which is not conducive to controlling the brightness of the LED lamp.

[0005] Therefore, it is necessary to provide a solution to solve the technical problem that the existing driving solution cannot work normally in high-frequency chopping occasions or cannot obtain a high-precision LED current. Summary of the invention

[0006] In the field of plant lighting, the LED lamp current waveform is required to be a PWM waveform that is chopped at high frequency, but the existing driving scheme cannot work properly in high-frequency chopping situations, or cannot obtain a high-precision LED current. In order to solve the technical problem that the existing driving scheme cannot work properly in high-frequency chopping situations, or cannot obtain a high-precision LED current, the present invention proposes a driving circuit for plant lighting, and the present invention is specifically implemented by the following technical solution.

[0007] The present invention provides a driving circuit for plant lighting, comprising a constant voltage source and an adjustable circuit, wherein a first end of the constant voltage source is used to connect a first end of a load, and the adjustable circuit comprises:

[0008] An adjustable voltage source, a first end of the adjustable voltage source being connected to a second end of the constant voltage source;

[0009] a chopper switch, wherein a first end of the chopper switch is connected to a second end of the adjustable voltage source, and a second end of the chopper switch is used to connect to a second end of the load;

[0010] A control circuit, wherein a first end of the control circuit is used to connect to the load, a second end of the control circuit is connected to a third end of the chopper switch, and a third end of the control circuit is connected to a third end of the adjustable voltage source. The control circuit is used to control the chopper switch and is also used to control the voltage of the adjustable voltage source according to a load current signal so that the sum of the voltage of the adjustable voltage source and the voltage of the constant voltage source matches a target voltage.

[0011] A further improvement of the driving circuit for plant lighting provided by the present invention is that the adjustable circuit also includes a first capacitor, a first end of the first capacitor is connected to the second end of the adjustable voltage source, and the second end of the first capacitor is connected to the first end of the constant voltage source.

[0012] A further improvement of the driving circuit for plant lighting provided by the present invention is that the adjustable voltage source includes a transistor, the first end of the transistor is connected to the second end of the constant voltage source, the second end of the transistor is connected to the first end of the chopper switch, and the third end of the transistor is connected to the control circuit, and the control circuit is used to control the impedance of the transistor according to the load current signal to control the voltage of the adjustable voltage source.

[0013] A further improvement of the driving circuit for plant lighting provided by the present invention is that the control circuit comprises a PWM generator for generating a PWM signal, and the PWM generator is connected to the third end of the chopper switch.

[0014] A further improvement of the driving circuit for plant lighting provided by the present invention is that the PWM generator is also used to adjust the duty cycle or frequency of the PWM signal.

[0015] A further improvement of the driving circuit for plant lighting provided by the present invention is that the control circuit further includes a sampling module and a comparison module;

[0016] The sampling module is connected to the constant voltage source, and the sampling module is used to connect to the load and sample the load current signal;

[0017] The comparison module is connected to the sampling module and the adjustable voltage source respectively, and is used to generate a control signal according to the load current signal and a reference signal, and control the adjustable voltage source according to the control signal.

[0018] A further improvement of the driving circuit for plant lighting provided by the present invention is that the comparison module includes a second capacitor, a first resistor and an operational amplifier, the inverting input terminal of the operational amplifier is respectively connected to the first end of the second capacitor and the sampling module, the non-inverting input terminal of the operational amplifier is used to receive the reference signal, the second end of the second capacitor is connected to the first end of the first resistor, and the second end of the first resistor is respectively connected to the output end of the operational amplifier and the third end of the adjustable voltage source.

[0019] A further improvement of the driving circuit for plant lighting provided by the present invention is that the sampling module includes a second resistor, the first end of the second resistor is connected to the comparison module, the first end of the second resistor is also used to connect the load, the second end of the second resistor is respectively connected to the ground terminal and the first end of the constant voltage source, the second resistor is used to sample the load current amplitude and generate the load current signal, wherein the sampling frequency is lower than the frequency of the PWM signal.

[0020] A further improvement of the driving circuit for plant lighting provided by the present invention is that the sampling module further includes a filtering unit and a ratio operator;

[0021] The filtering unit comprises a third resistor and a third capacitor, wherein a first end of the third resistor is connected to a first end of the second resistor, a second end of the third resistor is connected to a first end of the third capacitor, and a second end of the third capacitor is grounded, and the filtering unit is used to generate a current mean signal according to a load current sampled by the second resistor;

[0022] The first end of the ratio operator is connected to the second end of the third resistor, the second end of the ratio operator is connected to the PWM generator, and the third end of the ratio operator is connected to the comparison module. The ratio operator is used to generate a current amplitude signal according to the current mean signal and the duty cycle of the PWM signal, and the current amplitude signal serves as the load current signal.

[0023] A further improvement of the driving circuit for plant lighting provided by the present invention is that it comprises a plurality of the adjustable circuits, and the plurality of the adjustable circuits are used to connect a plurality of groups of the loads in a one-to-one correspondence.

[0024] The present invention is applied to the field of plant lighting and can maintain the high-frequency operation of the chopper switch; the current limiting module in the prior art is deleted, so that the chopping frequency of the chopper switch is not limited, which is beneficial to the photosynthesis of the plant, and the current limiting module is not required to adjust the LED current within the extremely short conduction time of the chopper switch; the loop speed of the control circuit can be much lower than the working speed of the chopper switch, reducing the difficulty of circuit design.

[0025] In order to provide stable direct current to the LED lamp, the current amplitude of the LED lamp during the conduction time of the chopper switch is obtained by detecting its average current, combining the duty cycle of the chopper switch, and performing ratio calculation. After comparing with the reference signal, the output voltage amplitude of the front-stage adjustable voltage source is adjusted to adjust the output voltage amplitude of the power supply toward the target voltage, so as to achieve the effect that the current amplitude of the LED lamp is equal to the target current, stabilize the current of the LED lamp, improve its current control accuracy, and make the brightness of the LED lamp stable and controllable. The present invention is suitable for high-frequency chopping occasions and can obtain high-precision LED current. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 is a circuit diagram of a driving circuit in the prior art.

[0028] Figure 2 for Figure 1 Current diagram of LED lamp.

[0029] Figure 3 for Figure 1 Circuit diagram of the current limiting module.

[0030] Figure 4 This is a circuit diagram of a driving circuit for plant lighting provided in Example 1 of the present invention.

[0031] Figure 5 for Figure 4 Current diagram of LED lamp.

[0032] Figure 6 1 is a circuit connection diagram of the transistor and other components in Example 1 of the present invention.

[0033] Figure 7 1 is a circuit connection diagram of the control circuit and other components in Example 1 of the present invention.

[0034] Figure 8 This is a circuit diagram of a driving circuit for plant lighting provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0035] The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] In order to solve the technical problem that the existing driving scheme cannot work normally in high-frequency chopping occasions, or cannot obtain LED current with higher precision, the present invention proposes a driving circuit for plant lighting, and the present invention is specifically implemented by the following technical scheme.

[0037] Combination Figure 4 As shown, the driving circuit for plant lighting provided in this embodiment 1 includes a constant voltage source Qs and an adjustable circuit, wherein a first end of the constant voltage source Qs is used to connect to a first end of a load, and the adjustable circuit includes:

[0038] An adjustable voltage source Qr, a first end of the adjustable voltage source Qr is connected to a second end of the constant voltage source Qs;

[0039] A chopper switch S1, wherein a first end of the chopper switch S1 is connected to a second end of the adjustable voltage source Qr, and a second end of the chopper switch S1 is used to connect to a second end of the load;

[0040] A control circuit L, wherein a first end of the control circuit L is used to connect to a load, a second end of the control circuit L is connected to a third end of the chopper switch S1, a third end of the control circuit L is connected to a third end of the adjustable voltage source Qr, and the control circuit L is used to control the chopper switch S1, and is also used to control the voltage of the adjustable voltage source Qr according to a load current signal, so that the sum of the voltage of the adjustable voltage source Qr and the voltage of the constant voltage source Qs matches the target voltage.

[0041] In this embodiment 1, the target voltage is the voltage value presented by the load under the rated current. In this embodiment 1, the constant voltage source Qs and the adjustable voltage source Qr are connected in series, and the two are connected in series and serve together as the power supply of other components (including the load) in the electrical circuit. The voltage obtained by other components is the sum of the output voltage of the constant voltage source Qs and the output voltage of the adjustable voltage source Qr; wherein, the output voltage of the constant voltage source Qs is fixed, and the output voltage of the adjustable voltage source Qr can be controlled by the control circuit L. On the one hand, the control circuit L outputs a chopping signal to the chopping switch S1, so that the chopping switch S1 works under the control of the chopping signal, thereby working in the on and off state; on the other hand, the control circuit L can detect the load current signal of the load, and control the voltage of the adjustable voltage source Qr according to the load current signal. In this embodiment 1, the voltage of the adjustable voltage source Qr is controlled according to the load current signal, so that the sum of the voltage of the adjustable voltage source Qr and the voltage of the constant voltage source Qs matches the target voltage, wherein the target voltage is the voltage value presented by the load under the rated current; specifically, matching can mean being equal, or the sum value and the target voltage are kept within a preset difference range. In this embodiment 1, the load is an LED lamp.

[0042] Furthermore, the adjustable circuit further includes a first capacitor C1, a first end of the first capacitor C1 is connected to a second end of the adjustable voltage source Qr, and a second end of the first capacitor C1 is connected to a first end of the constant voltage source Qs.

[0043] In order to allow the constant voltage source Qs and the adjustable voltage source Qr to work better in high-frequency chopping situations and avoid damaging the constant voltage source Qs and the adjustable voltage source Qr, in this embodiment 1, the first end of the first capacitor C1 is connected to the second end of the adjustable voltage source Qr, and the second end of the first capacitor C1 is connected to the first end of the constant voltage source Qs.

[0044] Combination Figure 6 As shown, further, the adjustable voltage source Qr includes a transistor T, a first end of the transistor T is connected to the second end of the constant voltage source Qs, a second end of the transistor T is connected to the first end of the chopper switch S1, and a third end of the transistor T is connected to the control circuit L, and the control circuit L is used to control the impedance of the transistor T according to the load current signal to control the voltage of the adjustable voltage source Qr.

[0045] The adjustable voltage source Qr includes a transistor T with variable impedance, and the transistor T may be a MOS tube (metal-oxide-semiconductor field effect transistor T) or a triode. In the present embodiment 1, the transistor T is an N-channel field effect transistor, the drain of the N-channel field effect transistor is connected to the constant voltage source Qs, the source of the N-channel field effect transistor is connected to the chopper switch S1, and the gate of the N-channel field effect transistor is connected to the control circuit L. The control circuit L can control the transistor T and change the impedance at both ends of the transistor T to change the voltage at both ends of the transistor T, change the sum of the output voltage of the constant voltage source Qs and the transistor T, and adjust the sum of the output voltage of the constant voltage source Qs and the transistor T toward the target voltage.

[0046] Combination Figure 7 As shown, further, the control circuit L includes a PWM generator U0 for generating a PWM signal, and the PWM generator U0 is connected to the third end of the chopping switch S1. In this embodiment 1, the chopping switch S1 receives the chopping signal output by the control circuit L, and the chopping signal is a PWM signal.

[0047] Furthermore, the PWM generator U0 is also used to adjust the duty cycle D or frequency of the PWM signal. In this embodiment 1, the PWM generator U0 can adjust the duty cycle D of the PWM signal. The user can adjust the PWM generator U0 according to the demand for the brightness of the LED lamp, thereby adjusting the duty cycle D of the PWM signal. When the LED brightness needs to be increased, the user can control the PWM generator U0 to increase the duty cycle D. When the LED brightness needs to be reduced, the user can control the PWM generator U0 to reduce the duty cycle D.

[0048] Furthermore, the control circuit L also includes a sampling module and a comparison module; the sampling module is connected to the constant voltage source Qs, and the sampling module is used to connect the load and sample the load current signal; the comparison module is respectively connected to the sampling module and the adjustable voltage source Qr, and the comparison module is used to generate a control signal according to the load current signal and the reference signal Vref, and control the adjustable voltage source Qr according to the control signal.

[0049] Furthermore, the comparison module includes a second capacitor C2, a first resistor R1 and an operational amplifier U1, the inverting input terminal of the operational amplifier U1 is respectively connected to the first end of the second capacitor C2 and the sampling module, the non-inverting input terminal of the operational amplifier U1 is used to receive a reference signal Vref, the second end of the second capacitor C2 is connected to the first end of the first resistor R1, and the second end of the first resistor R1 is respectively connected to the output end of the operational amplifier U1 and the third end of the adjustable voltage source Qr.

[0050] Furthermore, the sampling module includes a second resistor R2, a first end of the second resistor R2 is connected to the comparison module, the first end of the second resistor R2 is also used to connect the load, the second end of the second resistor R2 is respectively connected to the ground terminal and the first end of the constant voltage source Qs, and the second resistor R2 is used to sample the load current amplitude and generate a load current signal, wherein the sampling frequency is lower than the frequency of the PWM signal.

[0051] In the first embodiment, sampling is performed through the second resistor R2, and the voltage signal at both ends of the second resistor R2 can represent the current signal of the LED lamp branch (current signal of PWM waveform), that is, the voltage signal at both ends of the second resistor R2 can represent the load current signal, therefore, the second resistor R2 can sample the load current amplitude and generate the load current signal; in the first embodiment, the comparison module can directly compare the reference signal Vref with the signal obtained by real-time sampling, and control the impedance of the transistor T according to the comparison result, so that the voltage amplitude at both ends of the power supply (a power supply formed by the constant voltage source Qs and the adjustable voltage source Qr connected in series) is adjusted in the direction of the target voltage, so that the LED current is equal to the target current, wherein the target voltage is the voltage value presented by the load at the rated current, and the target current is the rated current of the load. The reference signal Vref can be determined according to the load demand, and different loads require currents of different amplitudes. In the first embodiment, the value of the reference signal Vref can be equal to the product of the resistance of the sampling resistor and the rated current of the load. In other embodiments, the target current and the value of the reference signal Vref may also be determined by the brightness of the LED lamp required by the user. When determining the target current, the current value may be determined according to actual needs, as long as the current value does not exceed the rated current of the LED lamp. The voltage value of the reference signal Vref is then determined based on the target current and the resistance value of the sampling resistor.

[0052] In this embodiment 1, the amplitude of the output voltage of the adjustable voltage source Qr is controlled so that the output voltage of the power supply is adjusted toward the target voltage. For example, the target voltage is 50V, the output voltage of the constant voltage source Qs is 40V, and the current output voltage of the adjustable voltage source Qr is 8V, then the voltage of the power supply is 48V. In other words, in order to obtain "the output voltage of the power supply is adjusted toward the target voltage", it is necessary to increase the output voltage of the adjustable voltage source Qr; if the current output voltage of the adjustable voltage source Qr is 13V, then the output voltage of the adjustable voltage source Qr is adjusted to decrease.

[0053] Furthermore, the sampling module also includes a filtering unit and a ratio operator U2; the filtering unit includes a third resistor R3 and a third capacitor, the first end of the third resistor R3 is connected to the first end of the second resistor R2, the second end of the third resistor R3 is connected to the first end of the third capacitor, and the second end of the third capacitor is grounded, and the filtering unit is used to generate a current mean signal according to the load current sampled by the second resistor R2; the first end of the ratio operator U2 is connected to the second end of the third resistor R3, the second end of the ratio operator U2 is connected to the PWM generator U0, and the third end of the ratio operator U2 is connected to the comparison module, and the ratio operator U2 is used to generate a current amplitude signal according to the current mean signal and the duty cycle D of the PWM signal, and the current amplitude signal is used as the load current signal.

[0054] In the present embodiment 1, the filtering unit and the ratio operator U2 can filter and average the signal sampled by the second resistor R2, respectively, to obtain a signal that can characterize the load current amplitude, and transmit it to the comparison module, which compares the signal with the reference signal Vref. According to the comparison result, the amplitude of the output voltage of the adjustable voltage source Qr is controlled to adjust the output voltage of the power supply in the direction of the target voltage so that the ratio operation result of the ratio operator U2 is equal to the product of the target current and the sampling resistor. In the present embodiment 1, the sampled signal is filtered and averaged, and then input into the comparison module. This scheme is easy to operate, has low requirements on its subsequent circuit, and is easy to implement. In the present embodiment 1, the target voltage is the voltage value presented by the load under the rated current, and the target current is the rated current of the load.

[0055] On the one hand, the control circuit L outputs a chopping signal to the chopping switch S1, so that the chopping switch S1 works under the control of the chopping signal and works in the on and off states; on the other hand, the average current or the LED current amplitude of the LED lamp is detected. When the average value of the LED lamp is detected, the average current detection value is ratio-operated with the duty cycle D of the chopping signal through the ratio operator U2, and the current value (target current) of the LED lamp is pre-set; in the comparison module, the result of the ratio operation or the LED current amplitude is compared with the target current, and the amplitude of the output voltage of the adjustable voltage source Qr is controlled according to the comparison result, so that the output voltage of the power supply is adjusted in the direction of the target voltage, so that the ratio operation result or the LED current amplitude is equal to the target current.

[0056] Embodiment 2:

[0057] In this embodiment 2, the driving circuit for plant lighting may include multiple adjustable circuits, and the multiple adjustable circuits are used to connect multiple groups of loads in a one-to-one correspondence. Figure 8As shown, n adjustable circuits are used to connect n groups of loads one by one. When there are n LED lamp loads, each LED lamp load corresponds to a chopper switch and an adjustable voltage source, and multiple LED loads share a constant voltage source Qs. In the multi-channel output driving circuit, the voltage of each LED lamp is allowed to be different. The voltage difference of the LED lamp in each branch is supplemented by adjusting the voltage at both ends of the adjustable voltage source in each branch, so that the sum of the adjustable voltage source and the LED lamp voltage of each channel is equal to the parameter voltage of the constant voltage source. Each group of LED loads can include multiple LED lamps connected in series. Figure 8 There are n groups of adjustable circuits, the first group of adjustable circuits includes a first group of adjustable voltage source Qr1, a first group of first capacitors C1, a first group of chopping switches S1, and a first group of control circuits L1, and the first group of adjustable circuits is used to connect the first group of loads LED1; the nth group of adjustable circuits includes an nth group of adjustable voltage source Qrn, an nth group of first capacitors Cn, an nth group of chopping switches Sn, and an nth group of control circuits Ln, and the nth group of adjustable circuits is used to connect the nth group of loads LEDn.

[0058] The present invention can maintain the high-frequency operation of the chopper switch S1; and there is no current limiting module, nor is it necessary for the current limiting module to adjust the LED current in the extremely short conduction time of the chopper switch S1, but the average value of the high-frequency LED lamp current is sampled, such as Figure 5 As shown, the current amplitude of the LED lamp within several, dozens or more cycles, or the average current of the LED lamp, is sampled, and the adjustable voltage source Qr is controlled by the current amplitude or the average value. The long sampling period allows the loop speed of the control circuit L to be much lower than the operating speed of the chopper switch S1, so that the control of the adjustable voltage source Qr by the control circuit L is freed from the limitation of the operating frequency of the chopper switch S1, reducing the difficulty of circuit design.

[0059] The present invention is applied to the field of plant lighting, and the current limiting module in the prior art is deleted, and the chopping frequency of the chopper switch S1 can be made unrestricted, which is beneficial to the photosynthesis of plants. In order to provide stable direct current to the LED lamp, the current amplitude of the LED lamp during the conduction time of the chopper switch S1 is obtained by detecting its average current, combining the duty cycle D of the chopper switch S1, and performing ratio calculation, and the output voltage amplitude of the front-stage adjustable voltage source Qr is adjusted after comparison with the reference signal Vref, so that the output voltage amplitude of the power supply is adjusted in the direction of the target voltage, so as to achieve the effect that the current amplitude of the LED lamp is equal to the target current value, stabilize the current of the LED lamp, improve its current control accuracy, and make the brightness of the LED lamp stable and controllable.

[0060] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A driving circuit for plant lighting, characterized in that: It includes a constant voltage source (Qs) and an adjustable circuit, wherein a first end of the constant voltage source (Qs) is used to connect a first end of a load, and the adjustable circuit includes: an adjustable voltage source (Qr), a first end of the adjustable voltage source (Qr) being connected to a second end of the constant voltage source (Qs); a chopper switch (S1), wherein a first end of the chopper switch (S1) is connected to a second end of the adjustable voltage source (Qr), and a second end of the chopper switch (S1) is used to connect to a second end of the load; A control circuit (L), wherein a first end of the control circuit (L) is used to connect to the load, a second end of the control circuit (L) is connected to a third end of the chopper switch (S1), and a third end of the control circuit (L) is connected to a third end of the adjustable voltage source (Qr), the control circuit (L) is used to control the chopper switch (S1), and is also used to control the voltage of the adjustable voltage source (Qr) according to a load current signal, so that the sum of the voltage of the adjustable voltage source (Qr) and the voltage of the constant voltage source (Qs) matches a target voltage; wherein matching refers to being equal, or the sum value and the target voltage are maintained within a preset difference range; The control circuit (L) comprises a PWM generator (U0) for generating a PWM signal, the PWM generator (U0) being connected to the third end of the chopper switch (S1), and the PWM generator (U0) being further used to adjust the duty cycle or frequency of the PWM signal; the control circuit (L) further comprises a sampling module and a comparison module; the sampling module is connected to the constant voltage source (Qs), and the sampling module is used to connect to the load and sample the load current signal; The comparison module is connected to the sampling module and the adjustable voltage source (Qr) respectively, and the comparison module is used to generate a control signal according to the load current signal and the reference signal, and control the adjustable voltage source (Qr) according to the control signal; The comparison module comprises a second capacitor (C2), a first resistor (R1) and an operational amplifier (U1), the inverting input terminal of the operational amplifier (U1) is respectively connected to the first terminal of the second capacitor (C2) and the sampling module, the non-inverting input terminal of the operational amplifier (U1) is used to receive the reference signal, the second terminal of the second capacitor (C2) is connected to the first terminal of the first resistor (R1), and the second terminal of the first resistor (R1) is respectively connected to the output terminal of the operational amplifier (U1) and the third terminal of the adjustable voltage source (Qr); The sampling module comprises a second resistor (R2), a first end of the second resistor (R2) is connected to the comparison module, the first end of the second resistor (R2) is also used to connect the load, the second end of the second resistor (R2) is respectively connected to the ground end and the first end of the constant voltage source (Qs), and the second resistor (R2) is used to sample the load current amplitude and generate the load current signal, wherein the sampling frequency is lower than the frequency of the PWM signal.

2. The driving circuit for plant lighting according to claim 1, characterized in that: The adjustable circuit also includes a first capacitor (C1), a first end of the first capacitor (C1) is connected to a second end of the adjustable voltage source (Qr), and a second end of the first capacitor (C1) is connected to a first end of the constant voltage source (Qs).

3. The driving circuit for plant lighting according to claim 1, characterized in that: The adjustable voltage source (Qr) comprises a transistor (T), a first end of the transistor (T) is connected to a second end of the constant voltage source (Qs), a second end of the transistor (T) is connected to a first end of the chopper switch (S1), a third end of the transistor (T) is connected to the control circuit (L), and the control circuit (L) is used to control the impedance of the transistor (T) according to the load current signal to control the voltage of the adjustable voltage source (Qr).

4. The driving circuit for plant lighting according to claim 1, characterized in that: The sampling module also includes a filtering unit and a ratio operator (U2); The filtering unit comprises a third resistor (R3) and a third capacitor (C3), a first end of the third resistor (R3) is connected to a first end of the second resistor (R2), a second end of the third resistor (R3) is connected to a first end of the third capacitor (C3), and a second end of the third capacitor (C3) is grounded, and the filtering unit is used to generate a current mean value signal according to a load current sampled by the second resistor (R2); The first end of the ratio operator (U2) is connected to the second end of the third resistor (R3), the second end of the ratio operator (U2) is connected to the PWM generator (U0), and the third end of the ratio operator (U2) is connected to the comparison module. The ratio operator (U2) is used to generate a current amplitude signal according to the current mean signal and the duty cycle of the PWM signal, and the current amplitude signal is used as the load current signal.

5. The driving circuit for plant lighting according to claim 1, characterized in that: It comprises a plurality of the adjustable circuits, and the plurality of the adjustable circuits are used for connecting a plurality of groups of the loads in a one-to-one correspondence.

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