Method for reaching maximum power point of magnetic field energy collector

Abstract

The invention relates to the technical field of magnetic field energy collection, in particular to a method for reaching the maximum power point of a magnetic field energy collector, which comprises the following steps of: establishing an equivalent circuit of the magnetic field energy collector under a constant-voltage load, and performing theoretical analysis on the maximum power point of the magnetic field energy collector based on the equivalent circuit; designing a magnetic field energy collection system based on the theoretical analysis; and designing a specific circuit structure of the analog control circuit. Based on the characteristics of the magnetic field energy collector, the magnetic field energy collection maximum power point reaching method based on the low-power-consumption analog control circuit is provided, the maximum power point can be reached under different primary side currents and load resistors, and the performance of the magnetic field energy collector is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic field energy collection, and in particular to a method for achieving a maximum power point of a magnetic field energy collector. Background Art

[0002] In recent years, researchers have conducted extensive research on electromagnetic field energy harvesting technology. Among them, since the basic principle of electric field energy harvesting technology is to obtain energy through capacitor voltage division, this energy harvesting technology has limitations on the reactance of the coupling capacitor. Therefore, the main challenge facing electric field energy harvesting technology is the demand for the size of the coupling capacitor. For example, a one-meter-long capacitor plate is required to implement electric field energy harvesting technology. Due to its significant energy harvesting performance, compact size and economic feasibility, magnetic field energy harvesting technology has become the most promising technology for powering sensors. Magnetic field energy harvesting technology is a technology based on the principle of electromagnetic induction, which is divided into CT type and stand-alone type. Although the installation of stand-alone magnetic field energy harvesters is more flexible and convenient than that of CT type magnetic field energy harvesters, the magnetic field energy harvesting power of stand-alone magnetic field energy harvesting technology has not yet reached the energy requirements of most sensors.

[0003] However, the existing magnetic field energy harvesting technology has the problem of insufficient magnetic field energy harvesting power when the primary current is small. Therefore, it is necessary to design a method for achieving the maximum power point of the magnetic field energy harvester. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a method for achieving the maximum power point of a magnetic field energy collector.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: A method for achieving the maximum power point of a magnetic field energy collector comprises the following steps:

[0006] Step 1, establishing an equivalent circuit of a magnetic field energy harvester under a constant voltage load, and based on the equivalent circuit, performing a theoretical analysis on the maximum power point of the magnetic field energy harvester;

[0007] Step 2, designing a magnetic field energy collection system based on the theoretical analysis, wherein the magnetic field energy collection system includes a magnetic field energy collector, an analog control circuit, and a DC-DC converter, wherein the magnetic field energy collector, the analog control circuit, and the DC-DC converter are electrically connected in sequence; the DC-DC converter and the analog control circuit form an energy management circuit;

[0008] Step 3, designing the specific circuit structure of the analog control circuit.

[0009] Furthermore, in the step 1, it specifically includes:

[0010] In the equivalent circuit, the ideal current source I 1 sinωt; ideal transformer with N turns of magnetic core coil; excitation inductance L m (t); excitation current i m ; Load current i load ; Load voltage V load ;

[0011] When the core transfers energy to the load:

[0012]

[0013] In the formula: S is the equivalent cross-sectional area of ​​the magnetic core, B is the magnetic induction intensity, and t is the time;

[0014] Under constant voltage load, according to formula (1), the load voltage determines the rate of change of magnetic induction intensity. Rewrite formula (1) and integrate it:

[0015]

[0016] Where: t sat is the energy transfer time; B sat is the saturation magnetic induction intensity;

[0017] Solve formula (2):

[0018]

[0019] Where: T is the period of the primary current;

[0020] For the magnetic field energy harvester under constant voltage load, the magnetic field energy harvesting power is:

[0021]

[0022] It follows that:

[0023]

[0024] Where: ω is the primary current angular frequency;

[0025] Formula (3) shows that the energy transfer time is affected by the load resistance. When the load voltage is small, the magnetic core transfers energy in the full energy transfer cycle, and the magnetic field energy collection power is:

[0026]

[0027] When the load voltage is large, it is obtained:

[0028]

[0029] Combining formula (3) and formula (7), the magnetic field energy harvesting power under deep saturation is:

[0030]

[0031] When the maximum value of the magnetic field energy harvesting power under constant voltage load occurs when the magnetic core is slightly saturated, substituting formula (3) into formula (5), the magnetic field energy harvesting power is:

[0032]

[0033] Formula (9) is derived with respect to the load voltage:

[0034]

[0035] The load voltage value when formula (10) is equal to zero is the optimal load resistance value, let:

[0036]

[0037] Convert the zeros of formula (10) into the zeros of function f(x):

[0038] f(x)=1-cos xx sin x (12)

[0039] When the maximum power point appears when the core is slightly saturated, the zero point is between zero and π. Matlab software is used to plot the function graph of the function f(x) between zero and π in the open interval; the zero point is obtained as:

[0040] x=2.331 (13)

[0041] According to formula (9), formula (11) and formula (13), the optimal load voltage and maximum output power are obtained together:

[0042]

[0043] P max =0.652I 1 wSB sat (15)

[0044] Where: V max The load voltage value that maximizes the magnetic field energy harvesting power; P max It is the maximum value of magnetic field energy collection power.

[0045] Furthermore, in the step 2, it specifically includes:

[0046] In the analog control circuit, there are resistor dividers, voltage followers, and comparators. The resistor divider is used to control the load voltage V rect Sampling is performed to obtain Vi ; Use a voltage follower to prevent subsequent circuits from interfering with the resistor divider function, and use a comparator to make V i With the preset reference voltage V ref Compare; and then adjust the charge and discharge state of capacitor Ci by controlling the enable port of the DC-DC converter according to the comparison result;

[0047] When the DC-DC converter is in the state I where the enable terminal is not enabled, the output of the comparator is low, and the input resistance of the comparator input is above several thousand megohms, so no current flows; therefore, according to Kirchhoff's law, V in It can be expressed as:

[0048]

[0049] Where: V in is the voltage at the positive input of the comparator; R f is the resistance in the comparator feedback loop; R r is the resistance in the comparator feedback loop; V i is the output voltage of the resistor divider;

[0050] No current will flow through the input of the voltage follower:

[0051] V i = k(V rect -V D1 ) (17)

[0052] Where: k is the voltage divider ratio of the resistor divider; V rect is the load voltage; V D1 is the conduction voltage drop of diode D1;

[0053] According to formula (16) and formula (17), V in It can be expressed as:

[0054]

[0055] When V in exceeds the reference voltage V at the negative input of the hysteresis comparator ref When the comparator output V comp Output high level, so that the DC-DC converter enable terminal is enabled, the circuit enters state II; when the circuit state changes, V in and V ref Equal, according to formula (18) we can get the state transition threshold voltage V rect1 :

[0056]

[0057] Where: Vrect1 is the load voltage threshold for the circuit to switch from state I to state II; V ref is the reference voltage of the negative input terminal of the hysteresis comparator;

[0058] In state II, the enable terminal of the DC-DC converter is enabled, and energy is transferred from capacitor Ci to the load through the DC-DC converter; comp Output high level, according to Kirchhoff's law, V in The value of V i and V comp Joint decision:

[0059]

[0060] Where: V comp is the output voltage of the hysteresis comparator;

[0061] According to formula (20) and formula (17):

[0062]

[0063] When V in drops below V ref , the hysteresis comparator outputs a low level, so that the enable terminal of the DC-DC converter is not enabled, and the circuit state returns to state I; when the circuit state changes, V in and V ref equal, therefore, the state transition threshold voltage V rect2 for:

[0064]

[0065] After the circuit switches back to state I, the load voltage V rect rises again; then, V rect In V rect1 and V rect2 changes periodically between rect1 and V rect2 When both are close to the optimum load voltage, the magnetic field energy harvester always operates at the maximum power point.

[0066] Furthermore, in step 2, the DC-DC converter model is LTC3388-3.

[0067] Further, in step 3, the analog control circuit includes a resistor divider, a voltage follower, a comparator, a capacitor Ce, and a diode;

[0068] The resistor divider includes a start-up diode D1 and two resistors R i1 and R i2, the voltage follower includes an operational amplifier on the left, and the comparator includes a resistor R r , the operational amplifier on the right, resistor R1, resistor R f composition,

[0069] The resistor divider R i1 and R i2 The connection point is connected to the positive terminal of the operational amplifier on the left;

[0070] The negative terminal of the operational amplifier on the left is connected to the output terminal, and the output terminal is connected to the resistor R in the comparator. r connected;

[0071] The resistor R r Connected to the positive terminal of the operational amplifier on the right, the resistor R f The resistor R1 is connected between the output terminal and the positive terminal of the operational amplifier on the right, and the capacitor Ce is connected between the negative terminal of the operational amplifier on the right and the resistor R c1 and R c2 connected at the connection points;

[0072] The diode and capacitor Ce form the power supply V for the analog control circuit operation. cc , connected to the power supply end of the voltage follower and comparator for power supply.

[0073] It can be seen from the above description of the present invention that, compared with the prior art, the method for achieving the maximum power point of the magnetic field energy harvester of the present invention includes at least one of the following beneficial effects:

[0074] 1. Based on the characteristics of the magnetic field energy harvester itself, the present invention proposes a method for achieving the maximum power point of magnetic field energy harvesting based on a low-power analog control circuit. The maximum power point can be reached under different primary side currents and load resistances, greatly improving the performance of the magnetic field energy harvester.

[0075] 2. The present invention uses low-power analog devices and resistors above megohm to design an analog control circuit, avoiding the use of a microcontroller and achieving self-power supply of the analog control circuit. Compared with the original magnetic field energy collector, this method only adds some analog circuits with microwatt power consumption. Compared with other technical solutions, this method has almost no negative impact on the magnetic field energy collector, and the reliability of the analog circuit is significantly higher than that of the circuit containing a microcontroller.

[0076] 3. The present invention adopts a DC-DC converter instead of directly connecting a resistor after the rectifier bridge to provide a more practical and feasible solution for the design of the magnetic field energy harvester. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1A flowchart of the steps of a method for achieving the maximum power point of a magnetic field energy collector in a preferred embodiment of the present invention;

[0078] Figure 2 is a circuit diagram of an equivalent circuit in a preferred embodiment of the present invention;

[0079] Figure 3 A circuit diagram of a magnetic field energy collection system in a preferred embodiment of the present invention;

[0080] Figure 4 4 is a circuit diagram of an analog control circuit in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0081] 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.

[0082] Reference Figure 1 As shown, a preferred embodiment of the present invention, a method for achieving the maximum power point of a magnetic field energy harvester, comprises the following steps:

[0083] Step 1: Establish an equivalent circuit of the magnetic field energy collector under constant voltage load, and based on the equivalent circuit, perform theoretical analysis on the maximum power point of the magnetic field energy collector; wherein the circuit diagram of the equivalent circuit refers to Figure 2 As shown;

[0084] Step 2, based on the theoretical analysis, design a magnetic field energy collection system, the magnetic field energy collection system includes a magnetic field energy collector, an analog control circuit, and a DC-DC converter, the magnetic field energy collector, the analog control circuit, and the DC-DC converter are electrically connected in sequence; the DC-DC converter and the analog control circuit form an energy management circuit; wherein the circuit diagram of the magnetic field energy collection system refers to Figure 3 As shown;

[0085] Step 3, designing the specific circuit structure of the analog control circuit. Figure 4 shown.

[0086] As a preferred embodiment of the present invention, it may also have the following additional technical features:

[0087] In this embodiment, step 1 specifically includes:

[0088] In the equivalent circuit, the ideal current source I 1sinωt; ideal transformer with N turns of magnetic core coil; excitation inductance L m (t); excitation current i m ; Load current i load ; Load voltage V load ;

[0089] When the core transfers energy to the load:

[0090]

[0091] In the formula: S is the equivalent cross-sectional area of ​​the magnetic core, B is the magnetic induction intensity, and t is the time;

[0092] Under constant voltage load, according to formula (1), the load voltage determines the rate of change of magnetic induction intensity. Rewrite formula (1) and integrate it:

[0093]

[0094] Where: t sat is the energy transfer time; B sat is the saturation magnetic induction intensity;

[0095] Solve formula (2):

[0096]

[0097] Where: T is the period of the primary current;

[0098] For the magnetic field energy harvester under constant voltage load, the magnetic field energy harvesting power is:

[0099]

[0100] It follows that:

[0101]

[0102] Where: ω is the primary current angular frequency;

[0103] Formula (3) shows that the energy transfer time is affected by the load resistance. When the load voltage is small, the magnetic core transfers energy in the full energy transfer cycle, and the magnetic field energy collection power is:

[0104]

[0105] When the load voltage is large, it is obtained:

[0106]

[0107] Combining formula (3) and formula (7), the magnetic field energy harvesting power under deep saturation is:

[0108]

[0109] When the maximum value of the magnetic field energy harvesting power under constant voltage load occurs when the magnetic core is slightly saturated, substituting formula (3) into formula (5), the magnetic field energy harvesting power is:

[0110]

[0111] Formula (9) is derived with respect to the load voltage:

[0112]

[0113] The load voltage value when formula (10) is equal to zero is the optimal load resistance value, let:

[0114]

[0115] Convert the zeros of formula (10) into the zeros of function f(x):

[0116] f(x)=1-cos xx sin x (12)

[0117] When the maximum power point appears when the core is slightly saturated, the zero point is between zero and π. Matlab software is used to plot the function graph of the function f(x) between zero and π in the open interval; the zero point is obtained as:

[0118] x=2.331 (13)

[0119] According to formula (9), formula (11) and formula (13), the optimal load voltage and maximum output power are obtained together:

[0120]

[0121] P max =0.652I 1 wSB sat (15)

[0122] Where: V max The load voltage value that maximizes the magnetic field energy harvesting power; P max It is the maximum value of magnetic field energy collection power.

[0123] In this embodiment, step 2 specifically includes:

[0124] In the analog control circuit, there are resistor dividers, voltage followers, and comparators. The resistor divider is used to control the load voltage V rect Sampling is performed to obtain V i ; Use a voltage follower to prevent subsequent circuits from interfering with the resistor divider function, and use a comparator to make Vi With the preset reference voltage V ref Compare; and then adjust the charge and discharge state of capacitor Ci by controlling the enable port of the DC-DC converter according to the comparison result;

[0125] When the DC-DC converter is in the state I where the enable terminal is not enabled, the output of the comparator is low, and the input resistance of the comparator input is above several thousand megohms, so no current flows; therefore, according to Kirchhoff's law, V in It can be expressed as:

[0126]

[0127] Where: V in is the voltage at the positive input of the comparator; R f is the resistance in the comparator feedback loop; R r is the resistance in the comparator feedback loop; V i is the output voltage of the resistor divider;

[0128] No current will flow through the input of the voltage follower:

[0129] V i = k(V rect -V D1 ) (17)

[0130] Where: k is the voltage divider ratio of the resistor divider; V rect is the load voltage; V D1 is the conduction voltage drop of diode D1;

[0131] According to formula (16) and formula (17), V in It can be expressed as:

[0132]

[0133] When V in exceeds the reference voltage V at the negative input of the hysteresis comparator ref When the comparator output V comp Output high level, so that the DC-DC converter enable terminal is enabled, the circuit enters state II; when the circuit state changes, V in and V ref Equal, according to formula (18) we can get the state transition threshold voltage V rect1 :

[0134]

[0135] Where: V rect1 is the load voltage threshold for the circuit to switch from state I to state II; V refis the reference voltage of the negative input terminal of the hysteresis comparator;

[0136] In state II, the enable terminal of the DC-DC converter is enabled, and energy is transferred from capacitor Ci to the load through the DC-DC converter; comp Output high level, according to Kirchhoff's law, V in The value of V i and V comp Joint decision:

[0137]

[0138] Where: V comp is the output voltage of the hysteresis comparator;

[0139] According to formula (20) and formula (17):

[0140]

[0141] When V in drops below V ref , the hysteresis comparator outputs a low level, so that the enable terminal of the DC-DC converter is not enabled, and the circuit state returns to state I; when the circuit state changes, V in and V ref equal, therefore, the state transition threshold voltage V rect2 for:

[0142]

[0143] After the circuit switches back to state I, the load voltage V rect rises again; then, V rect In V rect1 and V rect2 changes periodically between rect1 and V rect2 When both are close to the optimum load voltage, the magnetic field energy harvester always operates at the maximum power point.

[0144] In this embodiment, in step 2, the DC-DC converter model is LTC3388-3.

[0145] In this embodiment, in step 3, the analog control circuit includes a resistor divider, a voltage follower, a comparator, a capacitor Ce, and a diode;

[0146] The resistor divider includes a start-up diode D1 and two resistors R i1 and R i2 , the voltage follower includes an operational amplifier on the left, and the comparator includes a resistor R r, the operational amplifier on the right, resistor R1, resistor R f composition,

[0147] The resistor divider R i1 and R i2 The connection point is connected to the positive terminal of the operational amplifier on the left;

[0148] The negative terminal of the operational amplifier on the left is connected to the output terminal, and the output terminal is connected to the resistor R in the comparator. r connected;

[0149] The resistor R r Connected to the positive terminal of the operational amplifier on the right, the resistor R f The resistor R1 is connected between the output terminal and the positive terminal of the operational amplifier on the right, and the capacitor Ce is connected between the negative terminal of the operational amplifier on the right and the resistor R c1 and R c2 connected at the connection points;

[0150] The diode and capacitor Ce form the power supply V for the analog control circuit operation. cc , connected to the power supply end of the voltage follower and comparator for power supply.

[0151] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and improved concepts of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A method for achieving the maximum power point of a magnetic field energy harvester, characterized in that: The following steps are involved: Step 1, establishing an equivalent circuit of a magnetic field energy harvester under a constant voltage load, and based on the equivalent circuit, performing a theoretical analysis on the maximum power point of the magnetic field energy harvester; Step 2, designing a magnetic field energy collection system based on the theoretical analysis, wherein the magnetic field energy collection system includes a magnetic field energy collector, an analog control circuit, and a DC-DC converter, wherein the magnetic field energy collector, the analog control circuit, and the DC-DC converter are electrically connected in sequence; the DC-DC converter and the analog control circuit form an energy management circuit; Step 3, designing the specific circuit structure of the analog control circuit.

2. A method for achieving the maximum power point of a magnetic field energy harvester according to claim 1, characterized in that: In the step 1, it specifically includes: In the equivalent circuit, there are an ideal current source I1sinωt on the primary side of the power frequency; an ideal transformer with a core coil having N turns; and an excitation inductor L m (t); excitation current i m ; Load current i load ; Load voltage V load ; When the core transfers energy to the load: In the formula: S is the equivalent cross-sectional area of ​​the magnetic core, B is the magnetic induction intensity, and t is the time; Under constant voltage load, according to formula (1), the load voltage determines the rate of change of magnetic induction intensity. Rewrite formula (1) and integrate it: Where: t sat is the energy transfer time; B sat is the saturation magnetic induction intensity; Solve formula (2): Where: T is the period of the primary current; For the magnetic field energy harvester under constant voltage load, the magnetic field energy harvesting power is: It follows that: Where: ω is the primary current angular frequency; Formula (3) shows that the energy transfer time is affected by the load resistance. When the load voltage is small, the magnetic core transfers energy in the full energy transfer cycle, and the magnetic field energy collection power is: When the load voltage is large, it is obtained: Combining formula (3) and formula (7), the magnetic field energy harvesting power under deep saturation is: When the maximum value of the magnetic field energy harvesting power under constant voltage load occurs when the magnetic core is slightly saturated, substituting formula (3) into formula (5), the magnetic field energy harvesting power is: Formula (9) is derived with respect to the load voltage: The load voltage value when formula (10) is equal to zero is the optimal load resistance value, let: Convert the zeros of formula (10) into the zeros of function f(x): f(x)=1-cosx-xsinx (12) When the maximum power point appears when the core is slightly saturated, the zero point is between zero and π. Matlab software is used to plot the function graph of the function f(x) between zero and π in the open interval; the zero point is obtained as: x＝2.331 (13) According to formula (9), formula (11) and formula (13), the optimal load voltage and maximum output power are obtained together: P max =0.652I1ωSB sat (15) Where: V max The load voltage value that maximizes the magnetic field energy harvesting power; P max It is the maximum value of magnetic field energy collection power.

3. A method for achieving the maximum power point of a magnetic field energy harvester according to claim 1, characterized in that: In the step 2, it specifically includes: In the analog control circuit, there are resistor dividers, voltage followers, and comparators. The resistor divider is used to control the load voltage V rect Sampling is performed to obtain V i ; Use a voltage follower to prevent subsequent circuits from interfering with the resistor divider function, and use a comparator to make V i With the preset reference voltage V ref Compare; and then adjust the charge and discharge state of capacitor Ci by controlling the enable port of the DC-DC converter according to the comparison result; When the DC-DC converter is in the state I where the enable terminal is not enabled, the output of the comparator is low, and the input resistance of the comparator input is above several thousand megohms, so no current flows; therefore, according to Kirchhoff's law, V in It can be expressed as: Where: V in is the voltage at the positive input of the comparator; R f is the resistance in the comparator feedback loop; R r is the resistance in the comparator feedback loop; V i is the output voltage of the resistor divider; No current will flow through the input of the voltage follower: V i =k(V rect -V D1 ) (17) Where: k is the voltage divider ratio of the resistor divider; V rect is the load voltage; V D1 is the conduction voltage drop of diode D1; According to formula (16) and formula (17), V in It can be expressed as: When V in exceeds the reference voltage V at the negative input of the hysteresis comparator ref When the comparator output V comp Output high level, so that the DC-DC converter enable terminal is enabled, the circuit enters state II; when the circuit state changes, V in and V ref Equal, according to formula (18) we can get the state transition threshold voltage V rect1 : Where: V rect1 is the load voltage threshold for the circuit to switch from state I to state II; V ref is the reference voltage of the negative input terminal of the hysteresis comparator; In state II, the enable terminal of the DC-DC converter is enabled, and energy is transferred from capacitor Ci to the load through the DC-DC converter; comp Output high level, according to Kirchhoff's law, V in The value of V i and V comp Joint decision: Where: V comp is the output voltage of the hysteresis comparator; According to formula (20) and formula (17): When V in drops below V ref , the hysteresis comparator outputs a low level, so that the enable terminal of the DC-DC converter is not enabled, and the circuit state returns to state I; when the circuit state changes, V in and V ref equal, therefore, the state transition threshold voltage V rect2 for: After the circuit switches back to state I, the load voltage V rect rises again; then, V rect In V rect1 and V rect2 changes periodically between rect1 and V rect2 When both are close to the optimum load voltage, the magnetic field energy harvester always operates at the maximum power point.

4. A method for achieving the maximum power point of a magnetic field energy harvester according to claim 1, characterized in that: In step 2, the DC-DC converter model is LTC3388-3.

5. A method for achieving the maximum power point of a magnetic field energy harvester according to claim 1, characterized in that: In step 3, the analog control circuit includes a resistor divider, a voltage follower, a comparator, a capacitor Ce, and a diode; The resistor divider includes a start-up diode D1 and two resistors R i1 and R i2 , the voltage follower includes an operational amplifier on the left, and the comparator includes a resistor R r , the operational amplifier on the right, resistor R1, resistor R f composition, The resistor divider R i1 and R i2 The connection point is connected to the positive terminal of the operational amplifier on the left; The negative terminal of the operational amplifier on the left is connected to the output terminal, and the output terminal is connected to the resistor R in the comparator. r connected; The resistor R r Connected to the positive terminal of the operational amplifier on the right, the resistor R f The resistor R1 is connected between the output terminal and the positive terminal of the operational amplifier on the right, and the capacitor Ce is connected between the negative terminal of the operational amplifier on the right and the resistor R c1 and R c2 connected at the connection points; The diode and capacitor Ce form the power supply V for the analog control circuit operation. cc , connected to the power supply end of the voltage follower and comparator for power supply.

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