Wireless power supply has a lot of kinds of kind. Use look sex or perceptual coupling means in the distance that is less than a few inches normally. Article discussion uses the solution of perceptual coupling.

 

The perceptual coupling radio in the model in source system, communicate magnetic field by emissive coil generation, generate alternating current in the induction in receiving coil next, the transformer system that resembles a model is same. The main distinction of transformer system and radio source system depends on, transformer system passes air gap or other non-magnetic the clearance that material forms parts emitter and receiver. In addition, hair ray is encircled and receive the coupling coefficient between coil normally very low. The coupling coefficient of transformer system is normally 0.95 to 1, and the coupling coefficient of radio source system is 0.8 to 0.05.

 

[graph 1. In radio source system, LTC4125 launchs coil in 24 H of the drive below 103 KHz, threshold value of input electric current is 1.3 A, frequency is restricted to be worth for 119 KHz, temperature of emissive coil surface is restricted to be worth for 41.5°C, LTC4120-4.2 uses as in receiver end charger of batteries of ion of lithium of 400 MA only part. ]

 

Radio pool charges ABC

 

Radio source system comprises by the two parts of air gap space: Blast off (Tx) circuit (include to launch coil) and receive (Rx) circuit (include to receive coil) .

 

In the design radio source batteries charges when the system, the n that can increase batteries energy actually is a crucial parameter. Receive power to depend on a lot of elements, include:

 

The power that ● projects is worth

● hair ray is encircled and receive the distance between coil and alignment condition, express normally with the coupling coefficient between coil

● blasts off and receive the tolerance of package

 

The main goal that any radio source emitter design is to make emissive circuit can produce a strong field, ensure in worst power transmission condition issues those who offer place to need to receive power. But, avoid to issue receiver overheat and electric overload in optimal circumstance as much important. When output power asks inferior and when coupling performance is excellent, this are attached most importance to especially should. For example, batteries uses those who stand by emissive coil to receive the batteries charger when coil fills report.

 

The simple and complete transmitter solution of use LTC4125

 

LTC4125 transmitter IC aims with Power By Linear™The charger of a batteries in range of products IC conjugate, use latter as receiver; For example, receiver of LTC4120— wireless power and batteries charger IC.

 

LTC4125 is had simple, powerful and all functions that place of safe circuit of wireless power transmitter needs. Can ask to adjust its to output power according to receiver load especially, and detect whether to put in electric eyewinker.

 

The place before be like is narrated, the transmitter in system of radio pool charger needs to produce strong magnetic field, transfer power in order to make sure in worst power transmission condition falls. For this, LTC4125 used a kind to have AutoResonant technology only.

 

The voltage that LTC4125 AutoResonant drive can ensure every SW brings a foot to go up from beginning to end as inphase as electric current of the input that cite a base. Referenced graph 2, flow to SW2 from SW1 when electric current when, switch A and C are opened, at the same time switch D and B are shut, vice versa. With this kind of method circular lock decides drive frequency, ensure LTC4125 from beginning to end with drive of its resonance frequency exterior LC network. Although the variable of successive change affects the syntonic frequency of LC resonator, be like temperature and the reflection impedance of around receiver, also be such.

 

 

[graph 2. LTC4125 AutoResonant drive]

 

Use this kind of technology, LTC4125 adjusts collect to become the drive frequency of complete bridge switch ceaselessly, so that with the actual resonance of network of series connection LC frequency photograph matchs. Such, LTC4125 can build alternating current of a big amplitude effectively, both neither needs tall dc to input voltage, also do not need value of high accuracy LC.

 

LTC4125 still passes those who change complete bridge switch to occupy the pulse width that adjusts the weaveform on network of series connection LC than coming for nothing. Occupy sky comparing through increasing, lieutenant general of network of series connection LC produces more electricity, provide higher power for receiver load thereby.

 

LTC4125 scans regularly this occupies sky comparing, the laden condition that carries in the light of receiver searchs optimal operation to nod. This kind of optimal power nods a search to allow bigger air gap tolerance and coil amlposition tolerance, avoid to cause receiver circuit overheat and electric overload below all circumstances at the same time. Use individual and exterior capacitance to be able to be opposite scanning interval is relaxed process designing.

 

[graph 3. LTC4125 pulse width scans—Medium voltage and electric current follow Tx coil to occupy sky comparing to increase and increase. ]

 

Graph 1 in shows system has taller amlposition tolerance. When coil when apparent amlposition, LTC4125 can adjust the magnetic field intensity of generation to receive full load charging current in order to ensure LTC4120 is received. It is in the system that the graph shows 1 times, be as long as the distance of 12 Mm can be transmitted be as high as 2 W.

 

Electric eyewinker detects

 

Another when any feasible and wireless power transmit circuit main feature is to be able to detect whether does electric eyewinker exist in the magnetic field that emissive coil produces. Emissive circuit aims to provide the power of made of baked clay above of hundreds fine long hair to receiver, need can detect whether to put in electric eyewinker, eddy current is formed in order to prevent in the eyewinker, bring about calorific.

 

The AutoResonant framework of LTC4125 allows to use distinctive means, let IC detect whether to put in electric eyewinker. Electric eyewinker can reduce the effective inductance cost in network of series connection LC. Bring about AutoResonant driver to raise collect to become frequency of complete bridge drive thereby.

 

[graph 4. Existence and nonexistent electric eyewinker from time to tome frequency of LC resonator voltage compares LTC4125 transmitter. ]

 

[graph 5. In radio source system, LTC4125 launchs coil in 24 H of the drive below 103 KHz, frequency is restricted to be worth for 119 KHz, temperature of emissive coil surface is restricted to be worth for 41.5°C, LT3652HV uses as in receiver end LiFePO4 of 1 A only part (3.6 V drifts) batteries charger. ]

 

Be restricted to be worth to frequency through resistor voltage divider after undertaking process designing is installed, LTC4125 exceeds this in AutoResonant drive when frequency is restricted to be worth, width can develop drive arteries and veins to be reduced inside period of time 0. Such, detect when LTC4125 when be being put in electric eyewinker, will stop to transmit power.

 

Attention, use this kind of frequency to move the phenomenon will detect whether to put in electric eyewinker, can use syntonic electric capacity (C) and emissive coil inductance (the tolerance of L) is exchanged detect of sensitivity rise. Initiative to the 5% models of each L value and C value public errand, can anticipate with what be worth than typical LC natural frequency is tall the frequency of 10% is restricted to be worth process designing into travel frequency, with obtaining reasonable eyewinker to detect sensitivity and reliable transmitter circuit are designed. But, the frequency that the component of 1% sets more close together noncombatant duty is restricted to be worth what compare a pattern only to anticipate natural frequency is tall 3% , can obtain taller detect sensitivity, still maintain the rash club sex of the design at the same time.

 

Power n flexibility and function

 

Through adjusting resistor and capacitance value, still can use identical applied circuit and different receiver IC pair, obtain taller fill electric power.

 

Because launch circuit to have efficient complete bridge driver, and receive circuit use develop of efficient step-down switch to attack, systematic whole efficiency can be as high as 70% . The dc input of emissive circuit of basis of systematic whole efficiency and the batteries that receive circuit output data computation to reach. Ask an attention, to systematic whole efficiency, the quality factor of two coil reachs its coupling state, the others with circuit is likewise important.

 

Of LTC4125 all these character are the implementation below the case that did not have direct communication between emitter and receiver coil. Because this can form a simple applied design, include all sorts of power requirements that are as high as 5 W, and a lot of different physical coil configuration.

 

[graph 6. The circuit of transmitter of power of typical and devoid line of use LTC4125 board. ]

 

Graph the LTC4125 application circuit of 6 indication models has small size, the character with concise layout. The place before be like is narrated, most character can use exterior resistor or capacitance is custom-built.

 

Conclusion

 

LTC4125 is the new-style IC with a powerful function, can offer found safe, simple and all character that efficient wireless power transmitter needs. Search of AutoResonant technology, optimal power and move through frequency detect the function of electric eyewinker, simplified wireless power transmitter designs complete function, offer outstanding distance and alignment allowance. LTC4125 is a kind of when obtain wireless power transmitter to be designed reliably right choice.