Analog constant power driving circuit without power feedback

Abstract

The invention relates to the technical field of constant power driving, in particular to an analog constant power driving circuit without power feedback. The circuit is characterized by comprising a current monitoring circuit, a voltage-controlled current source circuit and a control circuit, and the circuit is composed of an analog current monitoring chip U1, an operational amplifier U2, an NMOS tube M1, a resistor RS, a resistor RFT, a resistor RFB and a resistor RB. According to the analog constant-power driving circuit, the voltage of a load is monitored and fed back without using an additional circuit or component, and negative feedback of the voltage of the load can be realized only by depending on the topological structure of the circuit; components and circuits related to a digital circuit technology are not needed, extra chips such as an MCU and a DSP are not needed, and the method is realized by using a pure simulation technology; there is no need to monitor load power. Compared with a traditional constant-power driving circuit, the constant-power driving circuit has the advantages that the structure of the constant-power driving circuit is simplified, the complexity and the cost of the circuit are reduced, the reliability and the response speed of a system are improved, and meanwhile potential noise and interference caused by power feedback are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of constant power driving, and in particular to an analog constant power driving circuit without power feedback. Background Art

[0002] Generally speaking, the feedback signal for a constant-current drive circuit is the load current, while the feedback signal for a constant-voltage drive circuit is the load voltage. Similarly, the feedback signal for a traditional constant-power drive circuit is the load power. However, unlike constant-current and constant-voltage drive circuits, traditional constant-power drive circuits monitor load power based on the formula P = UI. This requires simultaneous monitoring of both the load current and voltage, and also requires power calculation, making load power monitoring costly. Generally speaking, there are three approaches to calculating load power: the first uses an analog multiplier to perform power calculations; the second uses an analog power monitoring chip with integrated current and voltage sampling (such as the MAX4211) or a digital power monitoring chip (such as the INA4235); and the third uses an analog-to-digital converter chip to convert the current and voltage signals into digital values, then uses an additional MCU or DSP chip to perform power calculations. However, it should be emphasized that any of these three approaches significantly increases the cost of the constant-power drive circuit and introduces additional noise and latency. This drawback is particularly pronounced when a solution includes analog-to-digital conversion. In addition, if digital processing technology is used to obtain the load power signal, then the corresponding circuit part that adjusts the load power must also add the function of processing digital signals, which will undoubtedly further increase the cost and complexity of the constant power drive circuit, making it difficult to apply in practice under cost constraints. Summary of the Invention

[0003] To address one or more of the above-mentioned problems mentioned in the background technology, the present invention proposes an analog constant power drive circuit without power feedback. The specific technical solution provided by the present invention is as follows: The present invention provides an analog constant power drive circuit without power feedback, characterized by including a current monitoring circuit, a voltage-controlled current source circuit, and a control circuit.

[0004] The current monitoring circuit includes an analog current monitoring chip U1, a resistor R S , resistor R S It is connected in series with the load to monitor the load current and output the monitored current signal after amplification.

[0005] The voltage-controlled current source circuit includes an N-channel enhancement mode MOS transistor (NMOS transistor) M1, a resistor R B , M1 is connected in series with the load, and the voltage control characteristics of the MOS tube are used to make the MOS tube work in the saturation region to output current to the load.

[0006] The control circuit includes an operational amplifier U2, a resistor R FB and resistor R FT , used to set the voltage signal V according to the load current signal output by the current monitoring circuit and the given power REF The gate voltage of the NMOS tube M1 of the voltage-controlled current source is adjusted, thereby adjusting the current of the load to achieve a constant power driving effect of the load.

[0007] The analog constant power drive circuit is composed of an analog current monitoring chip U1, an operational amplifier U2, an NMOS tube M1 and a resistor R S 、R FT 、R FB 、R B The non-inverting input terminal of the analog current monitoring chip U1 is connected to the resistor R S One end is connected to the power supply VCC, and the inverting input is connected to the resistor R S The other end and the drain of NMOS tube M1, the output end of chip U1 is connected to the resistor R FT The non-inverting input of the operational amplifier U2 is connected to the power setting voltage V REF , the inverting input is connected to a resistor R FT The other end and resistor R FB The drain of NMOS tube M1 is connected to the resistor R S The other end is connected to the inverting input of the analog current monitoring chip U1, and the gate is connected to the output of the operational amplifier U2, the resistor R FB The other end and resistor R B The source is connected to one end of the load, and the other end of the load is grounded. S One end is connected to the non-inverting input of the analog current monitoring chip U1 and the power supply VCC, and the other end is connected to the source of the NMOS tube M1. FT One end is connected to the output of chip U1, and the other end is connected to the resistor R FB One end of the resistor R FB One end is connected to the resistor R FT The other end is connected to the signal output terminal of the operational amplifier U2 and is also connected to the gate of the NMOS tube M1 and the resistor R B One end of the resistor R B One end is connected to the output of the operational amplifier U2, the resistor R FB The other end is connected to the gate of the NMOS tube M1, and the other end is grounded.

[0008] The constant power principle of the analog constant power drive circuit without power feedback proposed by the present invention is as follows:

[0009] Load current feedback signal V FB The relationship with the load current is as follows:

[0010] V FB =A V R S I L (1)

[0011] Among them A V is the voltage magnification of U1, I L is the load current. U2 and resistor R FB 、R FT The control circuit is formed. Using the virtual short and virtual open characteristics of the operational amplifier, we can know the gate voltage V of the NMOS tube M1. G for:

[0012]

[0013] Simplify formula (2) and let K F =R FB / R FT , we can get:

[0014] V G =(K F +1)V REF -K F V FB (3)

[0015] Load R L One end is grounded, and the other end is connected to the source of the NMOS tube M1. The load voltage is the source voltage of M1, which actually provides a negative feedback path for the load voltage. The gate of the NMOS tube has a high input impedance. When the gate is floating, the gate voltage may change randomly due to electrostatic induction, noise interference, etc., which may cause the NMOS tube to be mistriggered, accidentally turned on, or cut off and pulled down. B It is used to prevent the gate of M1 from being suspended. When the gate is not driven by other signals, the grounding resistor will pull the gate down to the ground level to ensure that the NMOS tube is in the cut-off state. In some embodiments, the resistor R B An additional capacitor is connected in parallel at both ends to reduce the high-frequency noise of the gate and improve the stability of the circuit. B The value can be 10KΩ to 100KΩ. M1 works in the saturation region when the following conditions are met, and behaves as a voltage-controlled current source controlled by the gate-source voltage:

[0016]

[0017] Here V GS(th) is the on-threshold voltage of M1, the voltage between the drain and source of M1 is VDS for:

[0018] V DS =VCC-I L (R L +R S ). (5)

[0019] From equations (4) and (5), we can see that when the load R L When the voltage changes, in order to make M1 work in the saturation region, the power supply voltage VCC should have some margin. Under the premise of ensuring the normal operation of the circuit, a lower power supply voltage VCC can be selected to improve the power efficiency of the constant power drive circuit.

[0020] Load R L The current is the drain current of M1. When M1 works in the saturation region, ignoring the channel length modulation effect, its current I L for:

[0021]

[0022] where μ n is the electron mobility, C ox is the gate oxide capacitance, W and L are the channel width and length of the MOS tube respectively. As we all know, for a constant power drive circuit, its load current should decrease as the load increases. A rough analysis of the entire drive circuit shows that when R L At a certain moment, the source voltage V S Increase so that V GS decreases, so the load current I L decreases, and I L Reducing the load current will cause the feedback signal V FB Decrease, according to formula (3), V G will increase. When V G With V S When both increase, V GS It is difficult to analyze the changing trend of the load current I L In fact, according to formula (6), the load current I L For load R L The partial derivative of can be obtained:

[0023]

[0024] Simplifying the above formula, we can get:

[0025]

[0026] As long as M1 does not work in the cut-off region, V GS ≥VGS(th) , so according to formula (8) we can get:

[0027]

[0028] If M1 works in the cut-off region, then V GS <V GS(th) , but at this time the load has no current, so in fact it still satisfies equation (9). Therefore, R L When it increases, its I L decreases, while R L When it decreases, its I L Increase, satisfying the basic law of constant power drive. Further analysis of R L with I L Relationship:

[0029]

[0030] According to formula (10), we can get:

[0031]

[0032] Analyzing the equation in formula (11), we can get:

[0033] △=(1+2ABK) 2 -4K 2 A 2 B 2 =1+4ABK>0. (12)

[0034] That is, the equation has two unequal real roots, and the analytical solution of its roots is:

[0035]

[0036] But in fact there should be only one real number solution. Note that the condition for the equation to be valid is V GS ≥V GS(th) ,Right now:

[0037]

[0038] According to equation (13) and inequality (14), the feasible analytical solution of the equation is:

[0039]

[0040] According to formula (15), the load power P can be obtained L With the load resistor R L The relationship is:

[0041]

[0042] It is difficult to judge the relationship between the load and its power based solely on formula (16). We can analyze the partial derivative relationship between the load power and the load resistance based on formula (8):

[0043]

[0044] Obviously, if If it is always established, it is an ideal constant power drive circuit. That is, it must meet the following conditions:

[0045]

[0046] If 2K(V GS -V GS(th) )(K F A V R S +R L )<<1 is always true, then 2K(V GS -V GS(th) )R L <<1 is always true. According to formula (18), it can be seen that the conditions of the ideal constant power drive circuit are not met. This situation is not within the scope of the present invention. Therefore, when the analog constant power drive circuit without power feedback proposed by the present invention works normally, the following conditions are always true:

[0047] 2K(V GS -V GS(th) )(K F A V R S +R L )>>1. (19)

[0048] Therefore, formula (17) can be simplified as follows:

[0049]

[0050] Formula (18) can be simplified as follows:

[0051]

[0052] As the load changes, it is difficult to require that Equation (21) always holds true. However, according to the load R L The range of change can be determined by reasonably setting K F 、A V and R S The value of can achieve the effect of constant power drive to a certain extent.

[0053] Let R T =K F A V R S 、R L ∈[RL_MIN ,R L_MAX ], if the following conditions are met:

[0054] R L_MIN ≤R T ≤R L_MAX , (twenty two)

[0055] Then the load R L The power variation law is:

[0056]

[0057] From formula (23), it can be seen that the load power increases first and then decreases as the load resistance increases. Therefore, the relationship curve between load power and load resistance is an inverted U-shaped single-peak curve. L =R T When , the load power reaches its maximum value. Moreover, according to the partial derivative relationship of power to load resistance in formula (20), it can be known that the influence of current on power change is greater than that of load resistance, so the relationship curve between load power and load resistance is not about R T Symmetrical, the power change on the left side of the curve is steeper than that on the right side. T The following conditions are met:

[0058]

[0059] Then there is

[0060] P(R L_MIN )≤P(R L_MAX ). (25)

[0061] In order to optimize the constant power characteristics of the constant power drive circuit, the power deviation compared to the target power must be reduced as much as possible in the entire load range. This can be achieved by adjusting R T With V REF The implementation steps of the present invention can be divided into two steps:

[0062] Step 1: According to the load R L The value range of [R L_MIN ,R L_MAX ] Use formula (33) to calculate R T The value of R T and formula R T =K F A V R S Adjust K F 、A V and R S value.

[0063] The purpose of step 1 is to adjust R T So that the objective function f P (R T ) to obtain the minimum value:

[0064]

[0065] Objective function f P (R T ) is the minimum value of the load R L_MIN and the maximum value R L_MAX The absolute value of the difference in load power between the two cases. The best case is:

[0066]

[0067] Solve R according to formula (16) and formula (27) T With R L_MIN 、R L_MAX The relational expression shows that:

[0068]

[0069] This equation contains nonlinear terms such as square roots and fractions. It is not a pure polynomial equation, but a nonlinear transcendental equation. According to equation (28), we can solve R by conventional algebraic methods. T The exact analytical solution of is not feasible, so we can only seek the next best option and find an approximate solution. This term makes the whole equation difficult to solve, so we try to simplify and approximate it. According to formula (19), the value range of 4ABK is analyzed. L The following conditions always hold true within the range of :

[0070] 4ABK>>2+4KB 2 I>>1,(29)

[0071] The following approximation can be made:

[0072]

[0073] Substituting the above formula into formula (16) and ignoring high-order infinitesimals, we can obtain:

[0074]

[0075] So formula (28) can be simplified as:

[0076]

[0077] Solving equation (32), we can obtain:

[0078]

[0079] Step 2: According to the desired load constant power value P T To adjust V REF So that the objective function f err (V REF ) to obtain the minimum value:

[0080]

[0081] The objective function f err (V REF ) is the minimum value of the load R L_MIN , maximum value R L_MAX and R calculated by formula (33) T Load power in three cases and the expected load constant power value P T The maximum absolute value of the difference.

[0082] Power setting voltage V REF and load power P L Positive correlation, V REF The value range of {V REF_MIN ,V REF_MAX ]as follows:

[0083]

[0084] Obviously, the resistor R S Change the resistor R under the premise of the series relationship between the NMOS tube M1 and the load S For example, the resistor R S One end of the resistor R is connected to the source of the NMOS tube M1, and the other end is connected to one end of the load; or S One end is connected to the other end of the load and the other end is grounded. S After the position of the resistor R is changed, the connection relationship of other components also needs to be changed accordingly. S After the position of the above resistor R S The relevant formulas also need to be changed accordingly. For example, if the resistor R S One end of the resistor R is connected to the source of the NMOS tube M1, and the other end is connected to one end of the load; or S One end is connected to the other end of the load and the other end is grounded, then the formula R T =K F A V R S Strain R T =(K F A V +1)R S .

[0085] Obviously, the analog current monitoring chip U1 can also be replaced by an analog circuit based on an operational amplifier chip and components such as capacitors and resistors. Such simple replacements, improvements, etc. should be included in the scope of protection of this application.

[0086] Compared with the prior art, the present invention has the following beneficial effects:

[0087] (1) The constant power drive circuit proposed in this invention does not require components or circuits related to digital circuit technology, and does not require additional chips such as MCU and DSP. It is implemented using pure analog technology. This not only reduces the cost and complexity of load power closed-loop control, but also improves the stability and anti-interference ability of the system. It is particularly suitable for application scenarios with high requirements on cost and reliability.

[0088] (2) The constant power drive circuit proposed in the present invention does not require the use of additional circuits or components to monitor and feedback the load voltage, and can achieve negative feedback of the load voltage only by relying on the topology of the circuit itself.

[0089] (3) The constant power drive circuit proposed in the present invention does not require a power feedback circuit to monitor the load power, thus simplifying the constant power drive circuit structure compared to conventional constant power drive circuits. This simplification not only reduces circuit complexity but also improves system reliability and response speed, while also reducing potential noise and interference caused by power feedback.

[0090] (4) The constant power drive circuit proposed in the present invention only consists of an analog current monitoring chip U1, an operational amplifier U2, an NMOS tube M1 and a resistor R S 、R FT 、R FB 、R B Compared with the traditional constant power drive circuit, the circuit components are fewer and the cost is lower. This simple design not only reduces the production cost, but also improves the maintainability of the system and has greater commercial value.

[0091] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for the description. Obviously, the drawings described below are merely some principle schematic diagrams and embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0093] Figure 1 This is the structural diagram of the traditional constant power drive circuit;

[0094] Figure 2 This is a structural diagram of a simulated constant power drive circuit without power feedback provided by the present invention;

[0095] Figure 3 This is a schematic diagram of a simulated constant power drive circuit without power feedback provided by the present invention;

[0096] Figure 4 The present invention provides a load power diagram of a constant power driving circuit without power feedback, which shows the load power changing with the load. DETAILED DESCRIPTION

[0097] In order to make the objectives, technical solutions and advantages of this application more clear, this application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0098] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should have the usual meanings understood by people with ordinary skills in the field to which this application belongs. The "first", "second" and similar words used in the embodiments of the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0099] To facilitate understanding, the specific process of the embodiment of the present invention is described below.

[0100] See also Figure 1 and Figure 2 , Figure 1 Module symbols in represents the multiplication operation, Figure 1 and Figure 2 The V+ and V- are respectively the positive and negative terminals of the DC power supply. Figure 1The traditional constant-power drive circuit shown requires monitoring the load's current and voltage and multiplying the load's current and voltage signals to determine the load's power. This power signal is then fed into a control unit as feedback. The control unit compares the load's power with a set power value and calculates a corresponding control voltage signal. This voltage control signal acts on a voltage-controlled current source to adjust the load's current, ultimately achieving negative feedback regulation of the load's power. Generally speaking, there are three approaches to calculating load power: the first uses an analog multiplier to perform power calculations; the second employs an analog power monitoring chip with integrated current and voltage sampling (such as the MAX4211) or a digital power monitoring chip (such as the INA4235); and the third employs an analog-to-digital converter chip to convert the current and voltage signals into digital values before using an additional MCU or DSP chip to perform power calculations. However, it should be noted that any of these three approaches significantly increases the cost of the constant-power drive circuit and introduces additional noise and latency. This drawback is particularly pronounced when using an analog-to-digital converter. In addition, if digital processing technology is used to obtain the load power signal, then the corresponding circuit part that adjusts the load power must also add the function of processing digital signals, which will undoubtedly further increase the cost and complexity of the constant power drive circuit, making it difficult to apply in practice under cost constraints.

[0101] Omitting the calculation of load power can fundamentally solve the above problem, which seems to be impossible. However, if the current and voltage of the load can be directly fed back to the control unit and the voltage-controlled current source through a special circuit topology, and the closed-loop feedback of current and voltage can achieve a feedback effect similar to power feedback to a certain extent, then in principle it is feasible to realize a constant power drive circuit. In view of this, the present invention innovatively proposes the following Figure 2 A simulated constant power drive circuit without power feedback is shown in FIG. Figure 1 Unlike the conventional constant-power drive circuit shown in Figure 1, the proposed constant-power drive circuit eliminates the need to monitor load voltage and calculate load power, while adding a negative feedback path for the load voltage to the voltage-controlled current source. Unlike conventional constant-power drive circuits that monitor load voltage, this negative voltage feedback is implemented without any additional components, but rather through the circuit's inherent topology.

[0102] See also Figure 3 , a schematic diagram of an analog constant power drive circuit without power feedback provided by an embodiment of the present invention is characterized in that it includes a current monitoring circuit, a voltage-controlled current source circuit, and a control circuit.

[0103] The current monitoring circuit includes an analog current monitoring chip U1, a resistor RS , resistor R S It is connected in series with the load to monitor the load current and output the monitored current signal after amplification.

[0104] The voltage-controlled current source circuit includes an N-channel enhancement mode MOS transistor (NMOS transistor) M1, a resistor R B , M1 is connected in series with the load, and the voltage control characteristics of the MOS tube are used to make the MOS tube work in the saturation region to output current to the load.

[0105] The control circuit includes an operational amplifier U2, a resistor R FB and resistor R FT , used to set the voltage signal V according to the load current signal output by the current monitoring circuit and the given power REF The gate voltage of the NMOS tube M1 of the voltage-controlled current source is adjusted, thereby adjusting the current of the load to achieve a constant power driving effect of the load.

[0106] The analog constant power drive circuit is composed of an analog current monitoring chip U1, an operational amplifier U2, an NMOS tube M1 and a resistor R S 、R FT 、R FB 、R B The non-inverting input terminal of the analog current monitoring chip U1 is connected to the resistor R S One end is connected to the power supply VCC, and the inverting input is connected to the resistor R S The other end and the drain of NMOS tube M1, the output end of chip U1 is connected to the resistor R FT The non-inverting input of the operational amplifier U2 is connected to the power setting voltage V REF , the inverting input is connected to a resistor R FT The other end and resistor R FB The drain of NMOS tube M1 is connected to the resistor R S The other end is connected to the inverting input of the analog current monitoring chip U1, and the gate is connected to the output of the operational amplifier U2, the resistor R FB The other end and resistor R B The source is connected to one end of the load, and the other end of the load is grounded. S One end is connected to the non-inverting input of the analog current monitoring chip U1 and the power supply VCC, and the other end is connected to the source of the NMOS tube M1. FT One end is connected to the output of chip U1, and the other end is connected to the resistor R FB One end of the resistor R FB One end is connected to the resistor R FTThe other end is connected to the signal output terminal of the operational amplifier U2 and is also connected to the gate of the NMOS tube M1 and the resistor R B One end of the resistor R B One end is connected to the output of the operational amplifier U2, the resistor R FB The other end is connected to the gate of the NMOS tube M1, and the other end is grounded.

[0107] Set the load range to 60Ω to 80Ω and the target constant power to 400mW. The corresponding simulation parameters are as follows:

[0108] Table 1 Simulation parameters of the simulated constant power drive circuit without power feedback

[0109]

[0110] The simulation parameters in Table 1 are used for simulation. The load power changes with the load as shown in Figure 4 As shown. Figure 4 It can be seen that the analog constant power driving circuit without power feedback proposed in the present invention has good constant power characteristics, and its maximum relative power deviation (MRPD) is only ±0.26%. The calculation formula of the maximum relative power deviation is:

[0111]

[0112] The load resistance corresponding to the maximum load power is approximately 69.30Ω. Use formula (33) to calculate R T =69.28Ω, it can be seen that the simulation results are highly consistent with the given calculation formula. Considering the limitations of the actual resistance specifications, the R set in Table 1 T =69Ω. Preferably, multiple resistors can be connected in series or in parallel to form an equivalent resistance R FB , more accurately adjust the resistance R FB .

[0113] For the convenience of description, the above-mentioned analog constant power drive circuit without power feedback proposed by the present invention is described by dividing it into various circuit modules according to their functions. Of course, when implementing this application, the functions of each circuit module can be implemented in the same or multiple hardware.

[0114] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present application (including the claims) is limited to these examples. Within the scope of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0115] In addition, to simplify description and discussion, and in order not to make the embodiment of the application difficult to understand, the connection with integrated circuit (IC) chip and other components may or may not be shown in the accompanying drawings provided. In addition, it can be shown in the form of a block diagram to avoid making the embodiment of the application difficult to understand, and this also takes into account the following fact, that is, the details of the implementation method of these block diagram devices are highly dependent on the platform to be implemented in the embodiment of the application (that is, these details should be completely within the scope of understanding of those skilled in the art). When specific details (for example, the calculation formula of circuit component parameters and the circuit component model used) are set forth to describe the exemplary embodiments of the application, it will be apparent to those skilled in the art that the embodiment of the application can be implemented in the absence of these specific details or when these specific details are changed. Therefore, these descriptions should be considered to be illustrative rather than restrictive.

[0116] The embodiments of the present application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of this application.

Claims

1. A simulated constant power drive circuit without power feedback, characterized in that: Including current monitoring circuit, voltage-controlled current source circuit, and control circuit; The current monitoring circuit includes an analog current monitoring chip U1, a resistor R S , resistor R S Connected in series with the load to monitor the load current and output the monitored current signal after amplification; The voltage-controlled current source circuit includes an N-channel enhancement mode MOS transistor (NMOS transistor) M1, a resistor R B , M1 is connected in series with the load, and the voltage control characteristics of the MOS tube are used to make the MOS tube work in the saturation region to output current to the load; The control circuit includes an operational amplifier U2, a resistor R FB and resistor R FT , used to set the voltage signal V according to the load current signal output by the current monitoring circuit and the given power REF The gate voltage of the NMOS tube M1 of the voltage-controlled current source is adjusted, thereby adjusting the current of the load to achieve a constant power driving effect of the load.

2. The analog constant power drive circuit without power feedback according to claim 1, characterized in that: The analog constant power drive circuit is composed of an analog current monitoring chip U1, an operational amplifier U2, an NMOS tube M1 and a resistor R S 、R FT 、R FB 、R B Composition: The in-phase input terminal of the analog current monitoring chip U1 is connected to the resistor R S One end is connected to the power supply VCC, and the inverting input is connected to the resistor R S The other end and the drain of NMOS tube M1, the output end of chip U1 is connected to the resistor R FT The non-inverting input of the operational amplifier U2 is connected to the power setting voltage V REF , the inverting input is connected to a resistor R FT The other end and resistor R FB The drain of NMOS tube M1 is connected to the resistor R S The other end is connected to the inverting input of the analog current monitoring chip U1, and the gate is connected to the output of the operational amplifier U2, the resistor R FB The other end and resistor R B One end of the resistor R S One end is connected to the in-phase input terminal of the analog current monitoring chip U1 and the power supply VCC, and the other end is connected to the source of the NMOS tube M1; the resistor R FT One end is connected to the output of chip U1, and the other end is connected to the resistor R FB One end of the resistor R FB One end is connected to the resistor R FT The other end is connected to the signal output terminal of the operational amplifier U2 and is also connected to the gate of the NMOS tube M1 and the resistor R B One end of the resistor R B One end is connected to the output of the operational amplifier U2, the resistor R FB The other end is connected to the gate of the NMOS tube M1, and the other end is grounded.

3. The analog constant power driving circuit without power feedback according to claim 1, characterized in that: The analog constant power driving circuit has no components and circuits related to digital circuit technology, does not require additional chips such as MCU and DSP, and is implemented using pure analog technology.

4. The analog constant power drive circuit without power feedback according to claim 1, characterized in that: The analog constant power driving circuit does not need to use additional circuits or components to monitor and feedback the load voltage, and can achieve negative feedback of the load voltage only by relying on the topology structure of the circuit itself.

5. The analog constant power driving circuit without power feedback according to claim 1, characterized in that: The analog constant power driving circuit does not need to monitor the power of the load.

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