Solar panels are being increasingly used in street lighting applications to make for environment friendly designs by reducing the dependency on conventional energy. The use of High Brightness LEDs (HB-LEDs) for illumination in streetlights further increases their energy efficiency. Figure 1 shows a picture of a solar panel powered street light with high brightness LEDs. These systems employ lead acid batteries that get charged by solar panels during the day. The energy from the batteries is then used to drive the LEDs in the night.
Figure 1. Solar powered street light
Solar panels consist of photovoltaic cells that use light energy from the sun to generate electricity through photovoltaic effect. Maximum Power Point Tracking, referred to as MPPT, is an electronic system that operates the photovoltaic modules in solar panels to produce maximum power. MPPT varies the electrical operating point of the modules and enables them to deliver maximum available power. MPPT can be used in conjunction with a mechanical tracking system, but the two systems are completely different.
Cypress’ MPPT Solar Charge Controller is a battery charger and load controller with integrated LED driver, which features a smart tracking algorithm that maximizes energy harvest from solar panels. It is designed using Cypress’ PowerPSoC and uses the device’s integrated hysteretic controllers, its dedicated modulators, and PSoC core to implement the MPPT smart tracking algorithm, as well as the constant current LED driver circuit.
Table 1 below shows the specifications of the MPPT Solar Charge Controller Reference Design:
|Cypress Solution ||CY8CLED04D01 PowerPSoC|
MPPT Algorithm for optimized battery charging,
Buck and boost driver for LED applications
Solar panel open circuit voltage – 21 V
Short circuit current – 7 A
12 V Lead acid
Maximum charging current – 9.5 A
|Boost Driver Rating|
Voltage – 40 V,
Current – 1 A
|Floating Load Buck Driver Rating|
Voltage – 8 V,
Current – 1 A
The block diagram of the integrated solar charger and LED driver is shown in Figure 2. Power delivered by the solar panel is converted to a voltage level that can drive charging current into the battery. PowerPSoC generates the necessary control signal to drive a synchronous buck converter that converts the solar panel power to charge the battery. The MPPT algorithm embedded in the PowerPSoC takes voltage and current feedback from the panel and adjusts the control signals to operate the panel at its peak power. The PowerPSoC also monitors the battery charging process and provides status information based on battery condition and load switch status.
The application described below also integrates two channels of LED drivers. The first channel is configured in a floating load buck topology rated at 8V, 1A. The second channel is configured in a boost topology rated at 40V, 1A. The user can select between these two LED driver channels to drive LEDs with power from the batteries. The firmware in the attached code example is designed to operate one LED driver channel at a time. The solar charge controller also has board-level protection features that protect the board from battery short circuits, battery open, and battery/panel reverse connections.
Figure 2. MPPT Solar Charge Controller Block Diagram
Please contact Innovatech Switching Power India to purchase samples of this reference design board.
Please refer http://ispipl.com/contact_us for more information.