Takahide Sato

Linearity enhancement technique for one bit A/D converter in wireless communication devices

In this paper, a novel one bit resolution ADC for wireless communication devices is presented. If we use a conventional one bit resolution ADC for wireless communication devices, the communication quality becomes worse due to heavy non-linearity. To overcome this problem, we proposed a novel one bit resolution ADC circuit with linearity enhancement technique, which uses a S/H and a hysteresis comparator. By using hysteresis effect, the periodicity of one bit resolution ADC output signal can be reduced. Signal-to-Quantization-Noise Ratio (SQNR) can be improved by 6.4dB, thanks to the proposed technique.

An Average Input Current Sensing Method of LLC Resonant Converters for Automatic Burst Mode Control

Burst mode control techniques have been studied for LLC resonant dc–dc converters to improve power conversion efficiencies at light load conditions. However, there are not many studies about how to detect the load conditions at burst mode not even at normal mode, at the primary side of LLC resonant dc–dc converters. In this paper, we propose and implement a lossless load detection technique for normal and burst modes by a novel average input current sensing method at the primary side of LLC resonant converters. Detailed theoretical analysis at normal and burst modes is presented and a load detection circuit is proposed with the consideration of integrated circuits. To verify the analysis, an LLC resonant offline converter with 400 V input and 16 V/10 A output is simulated using PSIM and a prototype board is built. The experimental results show that the proposed load detection technique is valid and practical. As a result, an automatic burst mode control for LLC resonant converters at light load conditions is realized with the proposed average input current sensing method.

An average input current sensing method of LLC resonant converters for precise overload protection

A precise overload protection is able to improve the thermal design of power supply systems. However, as for LLC resonant off-line converters, there are not many studies about how to detect the load conditions at the primary side of the converters which is important to realize the precise overload protection. In this paper, we implement a lossless and precise load detection technique by a novel average input current sensing method to achieve the precise overload protection. Detailed theoretical analysis is presented with statistical analysis on overload conditions. To verify the analysis, an LLC resonant off-line converter with 400V input and 16V/10A output is simulated using PSIM and a prototype board is built. The theoretical and experimental results show that the precise overload protection is realized based on the novel load detection technique. As a result, the thermal design of the LLC resonant off-line converters is improved.

An electronic ballast for electrodeless lamp with a long transmission cable

This paper explains the reason for an electrodeless lamp not lighting up when connected with a long transmission cable. Turning on the lamp is possible by selecting the appropriate capacitance in the resonance circuit according to the length of transmission cable used. A condition the chosen capacitor should satisfy is clarified.

High frequency ring oscillator using capacitor based level shift circuits

This paper proposes a novel high frequency ring oscillator. The proposed ring oscillator consists of CMOS inverters which use simple capacitor based level shift circuits. The level shift circuit consists of only a capacitor and a MOSFET. Its power consumption is ideally zero. Thanks to the level shift circuits, transconductance and drain conductance of MOSFETs in CMOS inverters increase and high oscillation frequency is achieved. Validity of the proposed method is confirmed by simulations. The simulation results show that oscillation frequency of the proposed circuit is 2.7 times as high as that of conventional circuit.