Energy Harvesting Conditioning Circuit - EHE004

The EHE004 is an energy harvesting conditioning circuit, which converts the AC output from a piezoelectric energy harvester to a regulated DC output.

The EHE004 consists of a full-wave rectifier with integrated charge management and DC-DC conversion, and connects directly to any Volture™ piezoelectric energy-harvesting product. The DC output can be configured to the following voltage settings: 1.8 V, 2.5 V, 3.3 V, and 3.6 V. The board includes 200 µF of storage capacitance onboard - more capacitance can be added if required.

The EHE004 utilizes the Linear Technology LTC3588 piezoelectric charge management IC - designed to maximize total piezoelectric energy harvester output and mechanical-to-electrical conversion efficiency with medium to heavy loads (below 10K-ohms).

Each Volture™ energy harvesting product has two piezoelectric wafers. The EHE004 provides the user with ability to connect these wafers either in series or parallel. The series setting provides power output at lower g levels for small vibration amplitude applications. The parallel setting provides higher average power output levels at higher vibration amplitude levels.

EHE004 Schematic

Please contact Chris Ludlow at cludlow@mide.com or 781-306-0609 x227, for further information.

EHE004

The following provides a brief summary of the most important specifications of the EHE004. For complete specifications and performance plots for the LTC3588-1 charge management IC, please refer to the LTC3588-1 data sheet.

For Volture™ specifications, such as typical relationships between frequency, tip mass and output voltage for each product, please refer to the Volture™ data sheet.

NOTE 1: An internal clamp circuit limits the input voltage to 20V; the maximum input voltage stated may be safely exceeded provided the maximum input current condition is satisfied.

NOTE 2: Does not include active switching or inductor currents (Isw=0). Dynamic supply current is higher due to gate charge being delivered at the switching frequency.

NOTE 1: Approximate maximum power point (open-circuit piezo voltage) at which power transfer to the load is maximized.

NOTE 2: Minimum start-up voltage in halfbridge (“superseries”) configuration.

NOTE 3: Ripple values measured at no load and the 10uF onboard output capacitance.

EHE004

The EHE004 performance was measured while connected to a Volture™ V25W piezoelectric energy harvester. The system was properly clamped and tuned using the procedures detailed in the Volture™ datasheet. The assembly was attached to a shake table to generate vibrations to test the system. The shake table was driven by a function generator and the amplitude was measured with an accelerometer. To determine average power, the output duty cycle at the known output voltage over a fixed 1.00K-ohm load was measured. Performance measurements were taken at 0.25g, 0.50g, 0.75g, and 1g amplitudes. The lowest amplitude at which the EHE004 input exceeded the UVLO threshold, producing a usable output, was also recorded. The figure below shows the results for these tests. For the same amplitude conditions, other Volture™ products would exhibit similar performance characteristics though with different power output levels. Typical average power output levels for Volture™ energy harvesting products can be found on the Volture™ datasheet.

EHE004 Applications

• Industrial Health Monitoring Network Sensors
• Condition Based Maintenance Sensors
• Wireless HVAC Sensors
• Mobile Asset Tracking
• Tire Pressure Sensors
• Oil and Gas Sensors
• All Air, Land, and Sea Vehicle Sensors
• Battery and Hard Wired Power Replacement