< /a> MPPT" title="MPPT">MPPT" title="MPPT">MPPT)集成电路,工作频率高达72MHz,具有多种串行接口(I2C, UART, SPI, SSP),专用的功能如光伏(PV)电压和电流测量,PV板参数配置,系统效率高达98%,提供10位ADC和8个模拟输入,转换时间低至 2.44 μs,主要用在 太阳能PV和燃料电池DC充电控制,公共照明和LED街灯照明的电池充电,DC/DC转换器,微逆变器等.本文介绍了MPT612主要特性和优势,方框图,PV板,控制器 DC负载的简化PV系统框图以及MPPT充电控制器参考系统框图,电路图和材料清单.

The MPT612, the first dedicated IC for performing the Maximum Power Point Tracking (MPPT) function, is designed for use in applications that use solar photovoltaic (PV) cells or in fuel cells. To simplify development and maximize system efficiency, the MPT612 is supported by a patent-pending MPPT algorithm, an application-specific software library and easy-to-use application programming interfaces (APIs). Dedicated hardware functions for PV panels, including voltage and current measurement and panel parameter configuration, simplify design and speed development.

The MPT612 is based on a low-power ARM7TDMI-S RISC processor that operates at up to 70 MHz and can achieve system efficiency ratings up to 98 %. It controls the external switching device through a signal derived from a patent-pending MPPT algorithm. The DC source can be connected to the IC through appropriate voltage and current sensors. The IC dynamically extracts the maximum power from the DC source, without user intervention. The IC can be configured for boundary conditions set in software. There are up to 15 kB of flash memory available for application software.

MPT612主要特性和优势:

ARM7TDMI-S 32 bit RISC core operating at up to 70 MHz

128-bit wide interface and accelerator enabling 70 MHz operation

10-bit ADC providing

Eight analog inputs

Conversion times as low as 2.44 μs per channel and dedicated result registers minimize interrupt overhead

Five analog inputs available for user specific applications

. One 32-bit timer and external event counter with four capture and four compare channels

. One 16-bit timer and external event counter with three compare channels

. Low power Real-Time Clock (RTC) with independent power supply and dedicated 32 kHz clock input

. Serial interfaces including:

Two UARTs (16C550)

Two Fast I2C-buses (400 kbit/s)

SPI and SSP with buffering and variable data length capabilities

. Vectored interrupt controller with configurable priorities and vector addresses

. Up to twenty eight (28), 5 V tolerant fast general purpose I/O pins

. Up to 13 edge or level sensitive external interrupt pins available

. Three levels of flash Code Read Protection (CRP)

. 70 MHz maximum clock available from programmable on-chip PLL with input frequencies between 10 MHz and 25 MHz and a settling time of 100 ms

. Integrated oscillator operates with an external crystal at between 1 MHz and 25 MHz

. Power saving modes include:

Idle mode

Two Power-down modes; one with the RTC active and with the RTC deactivated

. Individual enabling/disabling of peripheral functions and peripheral clock scaling for additional power optimization

. Processor wake-up from Power-down and Deep power-down mode using an external interrupt or the RTC

MPT612应用:

. DC application charge controller for solar PV power and fuel-cells. The use cases are Battery charging for home appliances such as lighting, DC fans, DC TV,DC motor or any other DC appliance

Battery charging for public lighting and signaling - LED street lighting, garden/driveway lighting, railway signaling, traffic signaling, remote telecom terminals/towers etc

Battery charging for portable devices

. DC-DC converter per panel to provide improved efficiency

. Micro inverter per panel removes the need for one large system inverter

图1.MPT612方框图

采用MPT612参考板的光伏MPPT电池充电控制器

Photovoltaic MPPT battery charge controller using the MPT612 IC reference board Dwindling fossil fuel resources and the adverse environmental effects arising from converting these resources into energy have placed increasing focus on the use of non-fossil fuel energy sources such as solar energy.

Solar illumination can be converted into electrical energy through solar cells and the energy generated is called PhotoVoltaic (PV) energy. While the sun as a source is available for free, generating PV energy is expensive. This makes it important to extract the maximum PV energy from the incident sun light using the solar cells.

Typical solar cells comprise a PN junction made of a semiconductor material such as silicon. Since the power from a single cell is too small to be of practical use, cells are connected in series-parallel fashion to realize higher power, voltage and current. These are called solar panels or modules. PV panels are rated in terms of peak-watt at standard test conditions (25 degree C, 1000 W/m2 power density and spectrum of AirMass 1.5).

太阳能充电控制器

The PV power extracted can be used:

• To directly power a DC load

• To be converted to AC using an inverter to drive an AC load

• To charge an energy storage device (battery, super capacitor etc.) enabling the power to be used on demand

This application note focuses on charging batteries from a PV panel using an

MPPT-enabled charge controller.

Typically a charge controller performs the following basic functions:

• Controls maximum power extraction from a panel by tracking the MPP and ensuring that the panel operates at MPP

• Controls battery charging as defined in the battery charge cycle specification to improve usable battery life and protect it against reverse connection, over charging and deep discharging

• Load protection against overloads and short-circuits

• LED or LCD Status indications

• Communication of system parameters to external systems using dedicated interfaces MPPT充电控制器参考设计

The MPPT charge controller reference design example introduces a small, low-power MPPT IC called the MPT612, the first of its kind, supported by a patent-pending MPPT algorithm, which delivers up to 98% efficiency, and can be configured for customer-specific tasks. In this example, the charge controller takes power from solar PV panel and charges the battery as per the battery charge cycle specification. It also enables the battery to supply power to the DC loads connected to the controller. Apart from this, a number of protection mechanisms, system status indications, configurability, and communication facilities are implemented. The demo board also consists of a JTAG/UART add-on board which can be used for debugging, configuration, and data logging.


图2.PV板,控制器 DC负载的简化PV系统框图

图3.充电控制器参考系统外形图

图4.MPPT充电控制器参考系统框图

图5.PV电压和电流检测电路图


图6.电池电压和电流检测电路图

图7.DC/DC降压/升压转换器电路图

图8.MPPT数字电路图

Charge controller board power supply schematic

图9.JTAG/UART插入板电路图
充电控制器板材料清单(BOM):



JTAG/UART插入板材料清单:

详情请见:
http://ics.nxp.com/support/design/microcontrollers/solar.mppt/pdf/mpt612.pdf
和
http://ics.nxp.com/support/documents/pdf/an10936.pdf