CN108565990B - A wireless power transmission device with constant current output characteristics - Google Patents

Abstract

The invention relates to a wireless power transmission device with constant current output characteristics, which adopts a self-excited inverter circuit to design an inverter power supply, adopts the design scheme of the self-excited inverter circuit, can realize the self-driving of a switching tube, omits an additional PWM generator and a driving circuit, has simple structure, can automatically realize a resonance frequency tracking function, has smaller loss when the switching tube works in a zero-voltage on-off state, and greatly reduces the complexity of the inverter circuit. The electromagnetic resonance system with constant current output characteristic is adopted, the transmitting end of the electromagnetic resonance system adopts single-capacitor parallel compensation topology, the receiving end adopts double-capacitor series-parallel compensation topology, and constant current output of the wireless electric energy transmission device can be basically realized under different load conditions by only using 3 compensation capacitor elements, so that the addition of a subsequent DC/DC converter is omitted.

Description

A wireless power transmission device with constant current output characteristics

technical field

The invention belongs to the technical field of wireless power transmission, and relates to a wireless power transmission device with constant current output characteristics, in particular to a magnetic coupling resonant wireless power transmission device with constant current output characteristics.

Background technique

Since the second industrial revolution, human society has entered the era of electrification, ranging from power grids and high-voltage lines all over the world to various household electrical equipment. The transmission of electric energy is mainly through point-to-point direct contact transmission of metal wires. This "wired" transmission method has brought many problems. Due to problems such as friction and aging, sparks are easily generated during power transmission, which in turn affects the life of electrical equipment and the safety of electrical use ^[1] . In addition, the traditional wired power transmission method cannot meet the needs of some special applications, such as mines and water. With the development of human society and economy, various electronic devices have been widely used, but too many wires and sockets bring inconvenience to people's lives. In addition, the long-term power supply of medical devices implanted in the body is also very inconvenient through battery replacement; the development of electric vehicles is constrained by high cost, high maintenance and low reliability of wired charging piles. These problems are calling for a power transmission method without metal wires, that is, wireless power transmission.

At present, according to different transmission mechanisms, wireless power transmission technology can be mainly divided into microwave type, electric field coupling type, electromagnetic induction type and magnetic coupling resonance type. The principle of the microwave type is to use microwave beams instead of wires for energy transmission, but microwaves will generate losses when transmitted in the air, cannot pass through obstacles, and are harmful to the human body, so they are not suitable for daily use. The electric field coupling wireless power transmission is to use the electric field coupling effect of the plate capacitor to realize the wireless transmission of electric energy. However, the capacitance of the plate capacitor is only at the pF level, high voltage will be generated at both ends of the plates, and the high-intensity electric field between the plates is harmful to the human body. It is not suitable for use if the safety problem cannot be solved. Electromagnetic induction wireless power transmission uses the electromagnetic induction principle of the transformer for energy transmission. Only at a short distance (less than 1cm) can power transmission with higher power and higher efficiency be achieved. When the distance increases, the transmission efficiency will increase. A rapid decline does not bring improvement to people's lives. The magnetic coupling resonant wireless power transmission technology that has emerged in the past two years uses the electromagnetic field as the medium, using an electromagnetic resonance system with the same resonant frequency and high quality factor, and realizes the wireless transmission of electric energy based on the resonance principle under the condition of weak magnetic field coupling. Magnetic coupling resonant wireless power transfer technology, also known as magnetic field resonance technology, integrates electromagnetic fields, microwave engineering, power electronics, circuit theory, and material science. The magnetic coupling resonant wireless transmission system has small energy loss and large transmission distance, which can generally reach more than 50cm. It does not require a strong corresponding positional relationship between the transmitting coil and the receiving coil, and a reasonable range of position offset is allowed. The energy transmission is only in resonance. In the system, it will not affect other objects other than the resonance system, and there is no need to worry about foreign matter entering the air gap and causing damage while maintaining transmission efficiency.

The design of the high-frequency inverter power supply and the resonance system of the magnetically coupled resonant wireless power transfer system is a key part. At present, the commonly used high-frequency power supply is mainly designed based on the bridge inverter power supply. The traditional bridge inverter power supply has a complex structure, and requires an external PWM signal generator to drive the switch tube. Usually, a frequency tracking circuit is also required to realize the wireless power transmission system. Frequency tracking function, the drive of the inverter power supply is complicated, and the loss is relatively large. It is usually used in the high-power field of the kilowatt level, and the application effect is not good in the small and medium power field; for electronic products that use electric energy, some occasions require wireless power. The output current of the transmission device does not change with the change of the load, that is, the wireless power transmission device is required to maintain a constant output current under different output power conditions (the load changes), or only a small change, such as electric There is a constant current charging stage in the car charging process. At present, most wireless power transmission devices cannot automatically realize constant voltage output under different load conditions, but realize constant current output by adding a DC/DC converter in the subsequent stage, which leads to system complexity and cost. The efficiency is reduced, and the wide input voltage range of the DC/DC converter also poses great difficulties to its design.

Contents of the invention

technical problem to be solved

In order to avoid the disadvantages of the prior art, the present invention proposes a wireless power transmission device with a constant current output characteristic.

Technical solutions

A wireless power transmission device with constant current output characteristics is characterized in that it includes a self-excited inverter circuit, a transmitter, a receiver and a rectifier; the self-excited inverter circuit includes two MOS transistors Q ₁ and Q ₂ , two An inductive choke coil L _f1 and L _f2 , two diodes D ₁ and D ₂ , two zener diodes Dz-20V with a withstand voltage of 20V, two zener diodes Dz-3.9V with a withstand voltage of 3.9V, two Capacitors C _p1 and C _p2 and 4 resistors R _a , R _b , R _c , R _d ; resistor R _a is connected in series with R _c , resistor R _c is connected in series with R _d , and then connected in parallel to both ends of power supply U _dc ; inductor choke Flow coil L _f1 is connected in series with MOS transistor Q ₁ , inductive choke coil L _f2 is connected in series with MOS transistor Q ₂ , and then connected in parallel to both ends of the driving power supply U _drive ; the G pole and S pole of the two MOS transistors are connected in parallel for voltage regulation A series circuit of diode Dz-20V and Zener diode Dz-3.9V, the anodes of the two diodes are connected in series; MOS transistor _Q1 is connected between resistors R _a and R _c through capacitor C _p1 , and MOS transistor _Q2 is connected through capacitor C _p2 Connected between resistors _Rc and _Rd ; the negative end of diode _D1 is connected to the D pole of MOS transistor _Q1 , the positive end is connected between resistors _Rc and _Rd , the negative end of diode _D2 is connected to the pole of MOS transistor _Q2 The D poles are connected, and the positive end is connected between the resistors R _a and R _b ; the transmitter is a parallel resonant circuit of L ₁ C ₁ , and the input terminals are respectively between the D pole of the MOS transistor Q ₁ and the resistors R _c and R _d ; The receiver is a coil _L2 connected in series with capacitor _C2 and connected in parallel with capacitor _C3 . Both ends of capacitor _C3 are connected to full-bridge rectifiers _DR1 , _DR2 , _DR3 and _DR4 , and the rectified output is connected to filter inductor _Lf A filter circuit with a filter capacitor C _f , the filter output is connected to a load; the R _a = R _c is less than R _b = R _d ; the D ₁ = D ₂ ; the capacitor C _p1 = C _p2 ; the MOS tube Q ₁ =Q ₂ ; the inductance choke L _f1 =L _f2 ; the drive power U _drive is smaller than the power power U _dc .

The capacitances of C _p1 and C _p2 are much larger than the gate parasitic capacitances of Q ₁ and Q ₂ .

The relationship between the transmitter and receiver is: f _s frequency of self-excited inverter.

The models of the MOS tubes _Q1 and _Q2 are C2M0040120D.

The type of the diodes D ₁ and D ₂ is FR607.

The model of the Zener diode Dz-20V with a withstand voltage of 20V is 1n5335A.

The model of the four identical rectifying diodes of the full bridge rectifier is MBR20100.

Beneficial effect

A wireless power transmission device with constant current output characteristics proposed by the present invention adopts a self-excited inverter circuit to design an inverter power supply, and uses a self-excited inverter circuit design scheme to realize self-driving of the switch tube, eliminating the need for An additional PWM generator and drive circuit are added, the structure is simple, and the resonant frequency tracking function can be automatically realized at the same time, and the switching tube works in the zero-voltage on and off state, and the loss is small, which greatly reduces the complexity of the inverter circuit. Spend. Using an electromagnetic resonance system with constant current output characteristics, the transmitter of the electromagnetic resonance system adopts a single-capacitor parallel compensation topology, and the receiving end adopts a dual-capacitor series-parallel compensation topology. Only 3 compensation capacitor elements can be used under different load conditions. The constant current output of the wireless power transmission device is realized, and the addition of a post-stage DC/DC converter is omitted.

The present invention mainly has two beneficial effects:

1. The inverter power supply of the present invention realizes self-driving, soft switching, and simple structure.

2. The output current of the present invention has nothing to do with the size of the load, and has a constant current output characteristic.

As shown in Figure 3, in the absence of an external drive circuit, the wireless power transfer system realizes the self-driving of the switching tube, and when the driving voltage V _ds rises and falls, the drain-source voltage of the switching tube is 0V, that is, the The zero-voltage turn-on and turn-off of the switch tube is ensured, and the value of the off-state voltage V _ds is less than 0, that is, the negative-voltage turn-off of the switch tube is realized.

As shown in Figure 4, when the load resistance changes from 5Ω to 15Ω, the load change rate is 200%, the output current only changes from 2.698A to 2.562A, and the current change rate is 5%. It can be considered that when the load changes, The output current of the system remains basically constant, that is, the system has a constant current output characteristic.

Description of drawings

Figure 1: Circuit schematic diagram of the present invention

Figure 2: System Equivalent Circuit Diagram

Figure 3: Simulation working waveform diagram of Q ₁ and Q ₂

Figure 4: Simulation waveform diagram of output current changing with load

Detailed ways

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

The circuit diagram of a wireless power transmission device with constant current output characteristics is shown in Figure 1, specifically including:

(1) Two input power interfaces, one of which is the driving power supply U _drive (22V), and the other is the power supply U _dc (36V);

(2) A self-excited inverter circuit, including 2 MOS transistors Q ₁ and Q ₂ ; 2 inductive choke coils L _f1 and L _f2 ; 4 resistors R _a ~ R _d , the resistance values satisfy R _a = R _c ＝300Ω, R _b ＝R _d ＝10kΩ _; 2 diodes D ₁ and D ₂ , ideally the conduction voltage drop is 0V; ₂ is forward breakdown; 2 zener diodes Dz-3.9V with a withstand voltage of 3.9V, to prevent Q ₁ and Q ₂ from being reversely broken down; two capacitors C _p1 and C _p2 realize the switching tube Q ₁ and The negative voltage of Q ₂ is turned off, and the capacitance values of C _p1 and C _p2 are much larger than the gate parasitic capacitances of Q ₁ and Q ₂ .

The working principle of the self-excited inverter circuit is as follows: the inductance choke coils L _f1 and L _f2 are large enough, and the current flowing through L _f1 and L _f2 can be considered constant. Assuming that Q ₁ is in the off state at the beginning, and Q ₂ is in the on state, then the diode D ₁ is off, D ₂ is on, the inductor L _f2 stores energy, and the inductor L _f1 supplies power to the parallel L ₁ C ₁ resonant network, the inductor Resonance between L ₁ and capacitor C ₁ , when the quality factor of the L ₁ C ₁ resonant network is high enough, the resonant voltage u _ab at both ends of C ₁ is a sine wave, and the frequency of the sine wave is the natural resonant frequency of the L ₁ C ₁ resonant network. When the voltage u _ab resonantly decreases to the vicinity of U _drive , the diode D ₁ starts to conduct, and as the voltage u _ab further decreases, the gate potential of Q ₂ will decrease so that Q ₂ enters the amplification region from the conduction state. Once _Q2 enters the amplification region, the drain-source voltage of _Q2 is no longer 0V, and the gate potential of _Q1 will increase through the voltage transfer effect of diode _D2 , so that _Q1 enters the amplification region from the off state, which is A positive feedback process, as the voltage _uab resonates to about 0V, _Q2 will enter the off state and _Q1 will be turned on. Afterwards, the inductor L _f1 stores energy, the inductor L _f2 supplies power to the parallel L ₁ C ₁ resonant network, and the voltage u _ab reverses resonance. The working process is similar to the above analysis.

The existence of L _f1 and L _f2 makes the output of the inverter circuit have the characteristics of a current source. The voltage u _ab across the capacitor _C1 is the output voltage of the inverter circuit. In fact, the system samples u _ab through diodes D ₁ and D ₂ , and then controls the working state of switching tubes Q ₁ and Q ₂ , so the working frequency of switching tubes always depends on the frequency of u _ab , so that the inverter circuit The working frequency always follows the natural resonance frequency of the load network, realizing the frequency tracking function of the system. The parallel resonant circuit composed of L ₁ C ₁ is the transmitter of the WPT system. When the quality factor of the parallel resonant circuit of L ₁ C ₁ is high, the voltage u _ab can be regarded as a sinusoidal voltage, which can be expressed as:

U _ab is the effective value of the voltage u _ab , and f ₀ is the operating frequency of the inverter.

Apply the volt-second theorem to the inductance L _f1 or L _f2 :

Available: The voltage u _ab can be further expressed as:

u _ab ＝πU _dc sin(2πf ₀ t)

(3) An electromagnetic resonance system

The electromagnetic resonance system includes a transmitter and a receiver. The transmitter is composed of a capacitor _C1 and a transmitting coil _L1 , and the receiver is composed of a receiving coil _L2 and capacitors _C2 and _C3 .

Assuming the inverter frequency of the inverter circuit is f _s , the resonant system satisfies:

The working principle of the electromagnetic resonance system is as follows:

The self-excited inverter circuit is equivalent to the AC power supply U _ab , according to the switching theorem in the circuit theory, the rectifier device in the rear stage can be equivalent to an AC voltage source U _m , the mutual inductance of the transmitting coil and the receiving coil is M, and the rectifier’s The input alternating current is I _m . There are two power supplies in the circuit, in order to analyze the expression of _Im , the superposition theorem is adopted.

When the AC voltage source U _ab acts alone, the AC voltage source U _m is short-circuited, and the current flowing through the branch of the voltage source U _m is I _m1

When the AC voltage source U _m acts alone, the AC voltage source U _ab is short-circuited, and the current flowing through the branch of the voltage source U _m at this time is I _m2

At this time, the receiving coil L ₂ and the capacitors C ₂ and C ₃ resonate in parallel, and _Im2 = 0.

According to the superposition theorem,

The expression of the input AC current I _m of the rectifier is independent of the load resistance.

(4) A full bridge rectifier

The full-bridge rectifier includes 4 rectifying diodes DR1-DR4, a filter inductor L _f , a filter capacitor C _f , and a load resistor _RL . The full bridge rectifier realizes the conversion of AC to DC.

Assume that the output current of the rectifier module is I _o , and the relationship between I _o and I _m satisfies:

The input AC current I _m of the rectifier satisfies:

Combine the above conditions to get:

According to the expression that the output current is _Io , the system output current has nothing to do with the load resistance _RL . When the load changes, the system can still achieve constant current output.

Table 1 Simulation value of core components of wireless power transmission device

Detailed ways:

The present invention has two input power interfaces, one of which is the driving power supply U _drive = 22V, and the other is the power supply U _dc = 36V;

A self-excited inverter circuit, including 2 identical MOS transistors Q ₁ and Q ₂ , the model is C2M0040120D; 2 identical inductive choke coils L _f1 and L _f2 , L _f1 = L _f2 = 220uH; 4 resistors R _a ～R _d , the resistance value should satisfy R _a ＝R _c ＝300Ω, R _b ＝R _d ＝10kΩ; 2 identical diodes D ₁ and D ₂ , the type is FR607; 2 identical voltage regulators with a withstand voltage of 20V Diode Dz-20V, the model is 1n5357B; 2 identical zener diodes Dz-3.9V with a withstand voltage of 3.9V, the model is 1n5335A; two identical capacitors C _p1 and C _p2 , C _p1 =C _p2 =100nF.

An electromagnetic resonance system includes a transmitter and a receiver. The transmitter consists of a capacitor C ₁ and a transmitting coil L ₁ , C ₁ = 300nF, L ₁ = 9uH; the receiver consists of a receiving coil L ₂ and capacitors C ₂ and C ₃ Composition, L ₂ =42uH, C ₂ =C ₃ =128nF. The capacitors C ₁ , C ₂ and C ₃ are CBB capacitors, and the transmitting coil L ₁ and receiving coil L ₂ are wound by 750 Litz wires with a diameter of 0.1mm.

A full-bridge rectifier includes 4 identical rectifier diodes from DR1 to DR4, the model is MBR20100, a filter inductor L _f , L _f =2mH, a filter capacitor C _f , C _f =220uF, and a load resistor R _L , R _L = 5Ω.

After the system is connected to the power supply, the self-excited inverter circuit works, and the inverter frequency is the same as that of the electromagnetic resonance system. The energy is transferred from the transmitting end to the receiving end through magnetic field coupling, and the alternating current is converted into direct current through the rectifier to realize the direct current output.

Claims (7)

1. A wireless power transmission device with constant current output characteristics, characterized in that it includes a self-excited inverter circuit, a transmitter, a receiver and a rectifier; the self-excited inverter circuit includes two MOS transistors Q1 and Q2, two An inductive choke coil Lf1 and Lf2, two diodes D1 and D2, two zener diodes Dz-20V with a withstand voltage of 20V, two zener diodes Dz-3.9V with a withstand voltage of 3.9V, and two capacitors Cp1 and Cp2 And 4 resistors Ra, Rb, Rc, Rd; resistor Ra is connected in series with Rb, resistor Rc is connected in series with Rd, and then connected in parallel at both ends of power supply Udrive; inductive choke coil Lf1 is connected in series with MOS tube Q1, inductive choke coil Lf2 is connected with The MOS transistor Q2 is connected in series, and then connected in parallel to both ends of the drive power supply Udc; between the G pole and the S pole of the two MOS transistors is a series circuit of a parallel Zener diode Dz-20V and a Zener diode Dz-3.9V, and the positive poles of the two diodes Relatively in series; MOS transistor Q1 is connected between resistors Ra and Rb through capacitor Cp1, MOS transistor Q2 is connected between resistors Rc and Rd through capacitor Cp2; the negative end of diode D1 is connected to the D pole of MOS transistor Q1, and the positive end is connected to Between the resistors Rc and Rd, the negative terminal of the diode D2 is connected to the D pole of the MOS transistor Q2, and the positive terminal is connected between the resistors Ra and Rb; the transmitter is the a terminal of the parallel resonant circuit of L1C1 and the D pole of the MOS transistor Q1 connection, the b terminal is connected to the D pole of the MOS transistor Q2; the receiver is a parallel circuit with the capacitor C3 after the coil L2 is connected in series with the capacitor C2, and the two ends of the capacitor C3 are connected to the full-bridge rectifiers DR1, DR2, DR3 and DR4, and the rectified output is connected to The filter circuit of the filter inductor Lf and the filter capacitor Cf, the filter output is connected to the load; the Ra=Rc is less than Rb=Rd; the D1=D2; the capacitor Cp1=Cp2; the MOS tube Q1=Q2; the inductor The choke coil Lf1=Lf2; the drive power Udrive is smaller than the power power Udc. 2 . The wireless power transmission device with constant current output characteristics according to claim 1 , wherein the capacitances of Cp1 and Cp2 are much larger than the gate parasitic capacitances of Q1 and Q2 . 3. The wireless power transmission device with constant current output characteristic according to claim 1, characterized in that: the relationship between the transmitter and the receiver is: f _s is the frequency of the self-excited inverter. 4. The wireless power transmission device with constant current output characteristics according to claim 1, characterized in that: the models of the MOS transistors Q1 and Q2 are C2M0040120D. 5. The wireless power transmission device with constant current output characteristic according to claim 1, characterized in that: the diodes D1 and D2 are FR607. 6 . The wireless power transmission device with constant current output characteristic according to claim 1 , characterized in that: the model of the Zener diode Dz-20V with a withstand voltage of 20V is 1n5335A. 7. The wireless power transmission device with constant current output characteristic according to claim 1, characterized in that: the model of the four identical rectifying diodes of the full bridge rectifier is MBR20100.