## 1 Introduction  
Currently attention is focusing on the energy harvesting technologies to electrify the small-rated electric devices by environmental energy such as waste heat energy and machine vibration. One of the power generation methods by waste heat energy is the thermoelectric power generation by Seebeck effect of thermoelectric power module (TM) [1]. The TM can generate the electric power at low-temperature difference. However the thermoelectric power generation has some problems, such as the energy conversion efficiency, thermal leakage, and internal resistance. It is necessary to improve the energy conversion efficiency from thermal energy to electric energy, to suppress the thermal leakage and to track the maximum power point voltage of TM.  
We have proposed a method of suppressing the thermal leakage using heat pipes. The heat pipes were used for heat transfer from TM to heat sink avoiding thermal leakage. We confirmed to supply the electric power to the self-contained wireless telemetry by using the heat pipes and boost converter continuously. However, the boost converter controlled the output voltage of TM only. In [2,3], the impedance was mismatch between the TM and load impedance, so TM did not generate the maximum power. Thus, the maximum power point tracking (MPPT) control is necessary to maximize the power generation.  
One of the MPPT control methods is the hill-climbing method, which is employed to seek the maximum power point by calculating the power with a voltage and current sensors [4]. This method needs two sensors to calculate and track the maximum power. We have proposed a method of the MPPT controller for TM by temperature detection [5]. The thermoelectric power generation system has been used for the power source of self-contained wireless telemetry. The reference output voltage of the TM is decided by the approximation formula of the V-P characteristics and the module temperature. This means the operation algorithm is simple, thus the one-chip microcomputer is enough to control the MPPT. The experimental results exhibit that the MPPT controller can track the maximum power point voltage. And then, the thermoelectric power generation system can work the self-contained wireless telemetry which is required a supplied voltage of at least 2.1V. On the other hand, the MPPT control method of photovoltaic power system is proposed [6]. This proposed method can achieve to track the maximum power point with only a single sensor. However, it is necessary that the generated power is calculated. These MPPT methods need a number of sensors and elaborate calculation.  
This paper proposes a novel MPPT control method for thermoelectric power generation system of the constant load with only single current sensor. Estimating the output of the TM, the MPPT controller can track the maximum power point. Analyzing the thermoelectric power generation system with boost chopper by state space averaging method [7], the output of the TM estimates with only current sensor. The maximum power point voltage can be decided by both the estimated values and the internal resistance at the maximum power point. The proposed MPPT control method can achieve to track the maximum power point voltage without calculating the generated power of the TM. Digital computer simulation was implemented to demonstrate the validity and practicability of the proposed method using PSIM. Simulation results demonstrate that the proposed MPPT controller can track the maximum power point perfectly.