参数资料
| 型号： | EHE004 |
| 厂商： | Mide Technology Corporation |
| 文件页数： | 18/24页 |
| 文件大小： | 0K |
| 描述： | BOARD ENERGY HARVESTING |
| 产品培训模块： | EHE004 Piezoelectric Energy Harvesting Conditioning Circuit |
| 特色产品： | Energy Harvesting Power Products |
| 标准包装： | 1 |
| 系列： | Volture™ |
| 主要目的： | 电源管理，能量收集 |
| 嵌入式： | 否 |
| 已用 IC / 零件： | LTC3588 |
| 主要属性： | 用户可选择的输出电压 |
| 次要属性： | 最多 100mA 输出 |
| 已供物品： | 板 |
APPLICATIONS INFORMATION - LOAD ISOLATION EXAMPLE
Load Isolation Example for Maximum
Efficiency with Low-Impedance Loads
A cantilevered-beam piezoelectric energy harvester is a
complex electromechanical system in which the
electrical and mechanical loading of the beam are inter-
related. Understanding of this relationship is critical to
getting the most out of the system.
A properly tuned switched boost-buck circuit will
always outperform any circuit in which you do not
tune to the characteristics of its application. This
R
R
leak
leak
application note demonstrates a high-efficiency
switched step-down (buck) converter and
optimizations for maximum performance in a real-
world application. This circuit isolates the end-
application’s electrical load from the piezo beam,
providing proper impedance-matching of the circuit’s
“virtual load” to the beam, as well as minimizing
mechanical loading effects. Such a circuit is ideal for
low-impedance loads such as rechargeable batteries,
“bursty” loads such as intermittently-operating
sensors/transmitters, and applications where the
electrical load cannot be known in advance.
Basic Piezoelectric Beam Model
Before mechanical loading effects are taken into
account, each piezo beam can be thought of as a small
current source in parallel with a capacitor and parasitic
resistance, as shown in Figure 1. Typical values for this
parallel capacitance and resistance are on the order of
10nF and >40M, respectively. This parallel resistance
is insignificant for our purposes and may be ignored.
The current flow is equal to the derivative of the strain-
induced charge, or dQ/dt. The voltage transfer function
of each beam therefore is V(s)/q(s) = sR/(1+sRC),
where R is the parallel resistance and C is the parallel
capacitance of the beam.
In its simplest form, power is drawn from a small
capacitor which is constantly recharged by its
Figure 1: Piezo parallel and series equivalent circuits
environment. Care must be taken to choose when this
power is drawn. To maximize transfer efficiency, the
load must be matched to the piezo’s equivalent
impedance. In practice, the piezo impedance at a given
amplitude and frequency, as well as the load
impedance, can be thought of as a pair of simple (but
unknown) resistances which make up a resistor
divider. The power transfer between the two is
optimized when their values match. This corresponds
to the point at which the piezo’s loaded voltage is equal
to half its open-circuit voltage. Thus the impedance
match can be optimized without formally measuring or
knowing the impedance of the piezo source or load in-
situ.
Implementation
The circuit of Figure 2 provides a simple but effective
approach to meeting these goals.
The main components are a bridge rectifier formed by
D1-D4, low-power comparator (U1) and buck
converter (U2). During vibration, main storage
capacitor C1 slowly charges until its voltage reaches
the operating point (V oc /2) set by R1 and R2. Buck
converter U2 is enabled once the stored voltage
exceeds this value plus a small hysteresis. At typical
loads, the buck converter operation into the load will
REVISION N0. 002
REVISION DATE: 01-23-2013
18
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相关代理商/技术参数 |
参数描述 |
|---|---|
| EHEA 1PR | 制造商:Nexans 功能描述:CABLE SCRN 1CORE 7/0.2MM 100M 制造商:NEXANS 功能描述:CABLE, SCRN, 1CORE, 7/0.2MM, 100M 制造商:Nexans 功能描述:SHLD MULTICOND CABLE, 1COND, 24AWG, 328FT, 250V; Reel Length (Imperial):328ft; Reel Length (Metric):100m; No. of Conductors:1; Conductor Size AWG:24AWG; Voltage Rating:250V; No. of Strands x Strand Size:7 x 0.2mm; Cable Type:Shielded;RoHS Compliant: Yes |
| EHEA 2PR BLACK | 制造商:Nexans 功能描述: |
| EHEALTH-GW-SDK | 制造商:Bluegiga Technologies Inc 功能描述:EHEALTH SOFTWARE DEVELOPMENT KIT (SDK) LICENSE* |
| EHF-103-01-F-D | 制造商:Samtec Inc 功能描述:.050 EJECTOR HEADER ASSEMBLY - Bulk |
| EHF-10301-F-D-RA | 制造商:SAMTEC 制造商全称:Samtec, Inc 功能描述:.050 EJECTOR HEADER ASSEMBLY |
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