Charge and high efficiency solutions are charged in wirelessly

　　Author ：Iflowpower – Portable Power Station Supplier

Introduction Powering of many different applications from multiple industries. In many such applications, it is difficult to use or simply use the charging connector. For example, some products should seal the outer casing to protect sensitive electronic components from harsh environment, or allow convenient cleaning or disinfection.

Other products may be too small, can't accommodate the connector. In addition, when the battery-powered application includes moving or rotating components, please forget to charge this. Wireless charging is valuable in these and other applications, enhances reliability and robustness.

The wireless power system is overview, as shown in Figure 1, the wireless power system consists of two parts, namely the transmission circuit and the receiving circuit, there is a gap in the middle. The transmitting circuit includes a transmitting coil, the receiving circuit includes a receiving coil. Send circuit surrounds a high-frequency alternating magnetic field around the transmission coil.

The magnetic field is coupled to the receiving coil and converted into electrical energy, which can be charged to the battery or power supply to other circuits. Figure 1: Radio Battery Charger System Overview When designing a wireless power charging system, key parameters are actual charging power to new energy to batteries. The size of the received power depends on many factors, including the size of the transmit power, the distance, and the arrangement of the transmission coil (also referred to as a coil), and the tolerance transmitting and receiving components.

An important goal of any wireless power supply design is to ensure that the required power is supplied in the case of the worst power transmission condition. However, it is also important to prevent the heat and electrical overtility of the receiver under the best conditions. This is especially important when the output power requirements are very low, for example, when the battery is fully charged or close to full charging, this is especially important.

In such cases, the available power from the wireless system is high, but the required power is very low. This excess power generally results in a highly stream voltage, or consumes this extra power to make it heat. When the power required for the receiver is low, there are several ways to deal with excess power problems.

Rectifier voltage can be used with power Zener diodes or transient voltage suppressor clamp. However, this solution is generally large, and the heat appears is quite large. Assume that there is no feedback from the receiver, then the maximum power of the transmitter can be reduced, but this or will limit the available reception power, or shorten the transmission distance.

You can also send a receiving power information to the transmitter to adjust the transmission power in real time. Wireless power standard such as wireless charging alliance (WirelessPowerConsortium) QI standard uses this method. However, you can also use compact and efficient solution to solve such problems without having to confine complex digital communication methods.

In order to efficiently manage the power transfer from the transmitter to the receiver in all cases, the LTC4120 wireless power receiver integrates PowerbyProxi's patented technology, and PowerByProxi is Lineart's partner. PowerByProxi has obtained patented dynamic coordination control (DHC) technology to achieve non-contact charging efficiently, and no heat or electrical abortion in the receiver. With this technology, up to 2W power can be transmitted on a distance of 1.

2 cm. By adjusting the resonance frequency of the receiver from the "Tuning" state, DHC ensures that the required power can be supplied in worst cases, and do not worry that there is a problem in unloaded best. This allows the LTC4120-based wireless charging system to transmit power in the case of a long distance and with significant coil misalignment.

In addition, only the LTC4120-based system is controlled by the LTC 4120, such as the presence, there is a possible interrupt power transfer if there is existence. What is the operating effect of the system-based system-based system? Figure 2 shows the battery that is received with a LTC4120 wireless power receiver with the distance between the transmission coil and the receiving coil and the center to the center alignment, by a LTC4120 wireless power receiver Charging power. When the distance is 10mm, 2W charging power can be obtained, and the misalignment between the coils can be large without causing the available power to decrease.

Although there are many different wireless power transmitters available, the data shown in Figure 2 is from the basic DC-AC transmitter. This basic transmitter is an open source reference design. For more information on this electric feed-type push-pull transmitter, you can log in to Linellet's website and view related application guides.

Figure 2: Several factors should be considered when sending distance - receiving power analysis Select a transmitter. The transmitter is backup power (when the receiver does not exist)? Is the transmitter to distinguish the effective receiver and unrelated metal foreign body? Is the peripheral circuit to the EMI? Basic transmitter is a simple, low price Solution. Since passive resonant filtering is used, the EMI spectrum is well controlled at the transmitter base frequency (about 130kHz).

However, the transmitter transmits a full power regardless of whether the LTC4120 is present, so the backup power is relatively high. The transmitter also does not distinguish LTC4120 and metal foreign matter, so unrelated metal objects may be heated by inductive eddy currents. From PowerByProxi, you can purchase two ready-to-cemented transmitters: Proxi-Point and Proxi-2D.

The transmission distance of these transmitters and the same alternative tolerance performance is almost the same as the basic transmitter. However, these more advanced transmitters can detect if the LTC4120-based active receiver exists. This feature enables the two transmitters to reduce the backup power when the receiver does not exist, and if neither is unrelated to metal foreign matter, these transmitters are terminated.

Due to the high-efficiency buck type switch topology and DHC technology, the overall efficiency of the system is about 50% to 55%. This efficiency value can be calculated using battery charging power divided by DC input power to the transmitter. Overall efficiency and coupling and load have a big relationship.

When charging a single-cell battery is charged at 400 mA, the components based on the LTC 4120 are maintained within the ambient temperature of 10oC. The LTC4120-based receiver is shown in Figure 3. Figure 3: LTC4120 Receiver Demonstration Circuit Board Components Other System Configuring LTC4120 The wireless charging system based on an impressive gap can charge the battery at 400mA.

Based on lithium rechargeable battery for many hand-held applications, 1S (nominal 3.7V) and 2S (nominal 7.4V) lithium-ion battery pack is very common.

Lifecycle extension and safety function improvement also creates great market space for lithium iron phosphate (Lifepo4) battery. In addition, this type of battery pack has a wide variety of target charging voltages because customers want to make fine trade-offs between the initial battery capacity, life cycle, and the retention capacity change of time. If the LTC4120 does not have any additional circuits, it is possible to charge one and two lithium ion batteries and one, two and 3 phosphate ion batteries, so the demand for multiple target charging voltages can be met.

The charging current can be set in the range of 50 mA to 400 mA, while the charging voltage can be set in the range of 3.5V to 11V. In addition to the built-in constant current / constant voltage charging algorithm, the LTC4120 also supplies a variety of battery safety functions.

Terminate the safety end of the press. An NTC input supply battery temperature monitoring, and automatically suspend charging when temperature conditions are not safe. Two charging state pins supply charging cycle and fault status information.

Conclusion In many different types of applications, wireless charging is valuable, enhance reliability and robustness. It is important to consider how much power and power must be transmitted over most distances, and how much is the standard. Decide how to deal with maximum load power and the worst the worst cases of coupling between transmitters and receivers are often very easy.

Managing additional available power in light load or no load and maximum coupling may be challenging. In order to help respond to this challenge, Lao Lel has developed an LTC4120, which supplies everything you need for manufacturing compact and high-efficiency radio battery chargers. Its DHC technology allows very wide transfer gaps, extremely irresponsive to the transmission coil to the receiving coil.

LTC4120 is a key component of a solid non-contact charging system. .