chrispeng TI’s bq25504 is a high-efficiency ultra-low-power energy harvesting boost charging IC that can manage microwatts or milliwatts of power generated by various DC sources such as solar or thermoelectric generators (TEGs), with ultra-low quiescent current less than 330nA, It can continuously collect energy from input sources with VIN greater than 80mV, cold cranking voltage VIN greater than 330mV, with programmable dynamic MPPT, the collected energy can be stored in lithium batteries, thin film batteries, super capacitors or traditional capacitors. Mainly used for energy harvesting , solar chargers, TEG harvesting, wireless sensor networks (WSN), industrial monitoring, energy storage, environmental monitoring, bridge/structural health monitoring (SHM), smart building controls, handheld healthcare devices, and remote control of entertainment systems, etc. This article introduces bq25504 key advantages and features, block diagram, solar, TEG and MPPT application circuit diagram, bq25504 EVM evaluation board specifications, circuit diagram and bill of materials, PCB layout and total solar energy harvesting solution including traditional inverter solution block diagram, micro-inverter Solution block diagram and solar street lighting block diagram.
Texas Instruments introduces highly efficient boost charger IC for nano power energy harvesting
The bq25504 is the first of a new family of intelligent integrated energy harvesting Nano-Power management solutions that are well suited for meeting the special needs of ultra low power applications. The product is specifically designed to efficiently acquire and manage the microwatts (μW) to miliwatts (mW) of power generated from a variety of DC sources like photovoltaic (solar) or thermal electric generators. The bq25504 is the first device of its kind to implement a highly efficient boost converter/charger targeted toward products and systems, such as wireless sensor networks (WSN) which have stringent power and operational demands. The design of the bq25504 starts with a DCDC boost converter/charger that requires only microwatts of power to begin operating.
Main advantages and features of the bq25504:
• Ultra Low Power With High Efficiency DC/DC Boost Converter/Charger
–Continuous Energy Harvesting From Low Input Sources: VIN ≥ 80 mV(Typical)
–Ultra Low Quiescent Current: IQ < 330 nA (Typical)
–Cold-Start Voltage: VIN ≥ 330 mV (Typical)
• Programmable Dynamic Maximum Power Point Tracking (MPPT)
– Integrated Dynamic Maximum Power Point Tracking for Optimal Energy Extraction From a Variety of Energy Generation Sources
–Input Voltage Regulation Prevents Collapsing Input Source
• Energy Storage
–Energy can be Stored to Re-Chargeable Li-ion Batteries, Thin-film Batteries, Super-Capacitors, or Conventional Capacitors
• Battery Charging and Protection User Programmable Undervoltage /Overvoltage Levels
– On-Chip Temperature Sensor with Programmable Overtemperature Shutoff
• Battery Status Output
–Battery Good Output Pin
–Programmable Threshold and Hysteresis
–Warn Attached Microcontrollers of Pending Loss of Power
–Can be Used to Enable/Disable System Loads
bq25504 application:
• Energy Harvesting
• Solar Charger
• Thermal Electric Generator (TEG) Harvesting
• Wireless Sensor Networks (WSN)
• Industrial Monitoring
• Energy Storage
• Environmental Monitoring
• Bridge / Structural Health Monitoring (SHM)
• Smart Building Controls
• Portable and Wearable Health Devices
• Entertainment System Remote Controls
Figure 1. bq25504 functional block diagram
Figure 2. bq25504 solar application circuit diagram
VIN_DC = 1.2 V, CSTOR= 4.7 μF, LBST= 22 μH, CHVR= 4.7 μF, CREF= 10 nF, TSD_PROTL (65°C), MPPT (VOC) = 80% VBAT_OV = 3.1 V, VBAT_UV = 2.2 V, VBAT_OK = 2.4 V, VBAT_OK_HYST = 2.8 V, ROK1 = 4.42 MΩ, ROK2 = 4.22 MΩ, ROK3 = 1.43 MΩ, ROV1 = 5.9 MΩ, ROV2 = 4.02 MΩ, RUV1= 5.6 MΩ, RUV2 = 4.42 MΩ, ROC1= 15.62 MΩ, ROC2 = 4.42 MΩ
Figure 3. bq25504 TEG application circuit diagram
VIN_DC = 0.5 V, CSTOR = 4.7 μF, LBST = 22 μH, CHVR = 4.7 μF, CREF = 10 nF, TSD_PROTH (120°C), MPPT (VOC) = 50% VBAT_OV = 4.2 V, VBAT_UV = 3.2 V, VBAT_OK = 3.5 V, VBAT_OK_HYST = 3.7 V, ROK1 = 3.32 MΩ, ROK2 = 6.12 MΩ, ROK3 = 0.542 MΩ, ROV1 = 4.42 MΩ, ROV2 = 5.62 MΩ, RUV1 = 3.83 MΩ, RUV2 = 6.12 MΩ, ROC1 = 10 MΩ, ROC2 = 10 MΩ
Figure 4. bq25504 MPPT application circuit diagram
VIN_DC = 1.2 V, CSTOR = 4.7 μF, LBST = 22 μH, CHVR = 4.7 μF, TSD_PROTL (65℃),
MPPT (VOC) = Disabled VBAT_OV = 3.3 V, VBAT_UV = 2.2 V, VBAT_OK = 2.8 V, VBAT_OK_HYST = 3.1 V, ROK1 = 3.97 MΩ, ROK2 = 5.05 MΩ, ROK3 = 0.976 MΩ, ROV1 = 5.56 MΩ, ROV2 = 4.48 MΩ , RUV1 = 5.56 MΩ, RUV2 = 4.42 MΩ
bq25504 EVM Evaluation Board
bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for Energy Harvester Applications
bq25504EVM-674 – Ultra Low Power Boost Converter with Battery Management for Energy Harvester Applications. This EVM is programmed from the factory for settings compatible with most MCU’s and 3V coin cell batteries. The EVM is programmed to deliver a 3.1VDC maximum voltage (OV) for charging the storage element and the under voltage is programmed to 2.2VDC. The VBAT_OK indication toggles high when VSTOR ramps up at 2.8VDC and when VSTOR ramps down to 2.4VDC. The user’s guide describes the bq25504 evaluation module (EVM), how to perform a stand-alone evaluation and allows the EVM to interface with the system and host.
Key features of the bq25504 EVM evaluation board:
Evaluation Module for bq25504
Ultra Low Power Boost Converter/Charger with Battery Management for Energy Harvester Applications
Resistor-programmable settings for under voltage, over voltage for flexible battery management Including POTs for fine tuning the settings (not populated)
Programmable push-pull output Indication for battery status (VBAT_OK)
Test Points for Key Signals Available for Testing Purpose – Easy Probe Hook-up Jumpers Available – Easy to Change Settings
Figure 5. bq25504 EVM Evaluation Board Outline Drawing
bq25504 EVM Evaluation Board Specifications:
Figure 6. bq25504 EVM Evaluation Board Circuit Diagram
bq25504 EVM Evaluation Board Bill of Materials (BOM):
Figure 7. bq25504 EVM Evaluation Board PCB Layout
TI Solar Energy Harvesting Total Solutions
Traditional Inverter Solutions
Central, or “traditional”, inverters are centralized power control units that convert DC power from a string of 72-cell solar panels to AC power for use on the electrical utility grid. These are usually large scale commercial or residential systems producing in excess of 1 kW of power. Maximum power point tracking for the entire string is done only at the inverter box, which may also include relays to “island” the solar system from the grid.
Figure 8. Block diagram of a conventional inverter solution
Micro Inverter Solutions
Micro-inverters operate similarly to central inverter systems, but are installed on each individual panel and handle much less
power, typically 300 W. Micro-inverters provide the benefit of scalability for those who want to start small, yet have full
DC/AC conversion with MPPT, and expand later.
Figure 9. Microinverter solution block diagram (1)
Micro-converters maximize the DC power point of a single solar panel and convert (down or up) the DC voltage to be transported downstream to a centralized AC (grid-tied) inverter. Being located on each panel, these systems are lower power ( typ. 300 W) than centralized converters. These are sometimes called “optimizers” because they optimize the power of each panel, increasing the overall efficiency of the system.
➔
Figure 10. Microinverter solution block diagram (2)
3. Battery charging solutions
Off-grid solar power systems often need to charge a battery, or array of battery cells, that provide continuous power to the load when solar energy is no longer present. Often cost sensitive, in order to optimize the size, cost and usable power of the storage elements, off-grid systems also require that the power point be maximized. However, this can be done by employing, lower power and less complex MCUs than grid-tied systems or by employing a simple fixed power point – often set at 76 % of VOC. Loads such as LED lighting and motors may require additional power boosting and/or control.
Figure 11. Block diagram of solar street lighting.
For details, see:
http://www.ti.com/lit/ds/symlink/bq25504.pdf
and
http://www.ti.com/lit/ug/sluu654a/sluu654a.pdf
as well as
http://www.ti.com/lit/sl/slyy027/slyy027.pdf
The Links: SP14N02L6ALCZ 7MBR10SA120-70
