These devices rely on battery power for their operation which needs frequent recharging. Situations where external power sources are not accessible and the battery getting drained at the most inconvenient time are common nowadays. The feasibility of providing power o these portable devices on the go is gaining much research interest due to this fact. Advances in semiconductor technology have brought down the power consumption modern portable electronics considerably. So energy harvesting is a feasible approach for operating these low power devices.
Energy harvesting or scavenging is the processes to capturing the energy trot environmental sources and convert it into usable electrical energy As these devices are meant to be carried around, one suitable way of power scavenging is to harvest the usually wasted kinetic energy due to human physical activities. Piezoelectric energy harvesting can be used in order to do so. A transducer is a device capable of converting one form of energy into another. A piezoelectric transducer is capable of converting energy due to mechanical vibrations into electrical energy and vice versa.
To harvest the energy thus produced, the piezoelectric element has to be attached to a vibrating environment and use an interface circuit to transfer the produced energy into the load. The piezoelectric buzzer is an example of piezoelectric transducer. The ease of implanting the device makes it the suitable choice for harvesting the energy reduced during human physical activity. Therefore “A Portable Mobile Charger using Piezoelectric Energy” is designed to charge the mobile phone battery whenever it is needed, especially in an emergency situation.
The circuit operates by using available vibration source surrounding our life to generate its own electricity and thus can be used to charge mobile phone batteries and is be handy when the need arises. This allows people to move around with their daily activities while keeping their mobile phone fully charged. In the recent years, standardized chargers and connectors for mobile phones and other portable gadgets have been introduced. USB has been the standard for charging pretty much any small electronic gadget nowadays.
The standard USB power rating will be V mamma which meaner that a device connected will receive V and be able to draw a maximum of mamma. The bottom line is that if a circuit capable of converting the piezoelectric energy generated into the above mentioned ratings, then it is suitable to act as a USB charger regardless of different makes of mobile phones. With the exceptions of certain companies blocking USB charging, we can be sure that any phone supporting the feature can be charged using this. This Portable Mobile Charger using Piezoelectric Energy is a cheap and convenient alternative to conventional charging methods. The energy produced by piezoelectric transducer is continuously varying depending on the vibration level and also does not possess enough power for directly act as a power supply. So the generated electrical energy thus has to be conditioned to a constant sufficient power level for practical use. The piezoelectric harvesting system includes two stages namely harvesting structure and the harvesting circuit. The harvesting structure consists of piezoelectric buzzer, typically placed such that it is susceptible to vibrations.
The energy produced by the harvesting structure is collected by the harvesting circuit where it is conditioned for practical use. Piezoelectric Buzzer Rectifier & Storage Capacitor Voltage Butter and Implicit re Switching Circuit Voltage Regulator Target Device Figure 1: Block Diagram The first stage of harvesting circuit is to convert the alternating current (AC) produced by the harvesting structure into direct current (dc) by rectification. The output from a piezoelectric buzzer is only in the range of a few millions. A capacitor is used as an intermediate storage device.
The voltage stored has to be conditioned into the required USB voltage and current voltage rating. A voltage buffer followed by an amplifying circuit serves that purpose. The voltage amplified will be regulated and is supplied to the target device battery through a switching mechanism. Each block is described in detail in the following sections.
