Didelės spartos talpos ir įtampos keitiklis

Theoretical analysis and experimental investigation of the method to measure capacitance and structure’s capacitance-voltage characteristics by means of linearly varying voltage showed a linear dependence between the output voltage and capacitance (when transient process is over). Whereas the duration of transient process is determined mainly by the value of measured capacitance multiplied by resistance, the transient duration may be reduced by lowering resistor’s value, though it decreases signal to noise ratio. We choose another solution – the compensation of electric capacitance, which very effectively reduces (by a factor of several tens) the transient duration and does not affect the relationship measured capacitance – output voltage. It increases the operation speed of capacitance-voltage converter

Didelės spartos talpos ir įtampos keitiklis

Theoretical analysis and experimental investigation of the method to measure capacitance and structure’s capacitance-voltage characteristics by means of linearly varying voltage showed a linear dependence between the output voltage and capacitance (when transient process is over). Whereas the duration of transient process is determined mainly by the value of measured capacitance multiplied by resistance, the transient duration may be reduced by lowering resistor’s value, though it decreases signal to noise ratio. We choose another solution – the compensation of electric capacitance, which very effectively reduces (by a factor of several tens) the transient duration and does not affect the relationship measured capacitance – output voltage. It increases the operation speed of capacitance-voltage converter

Noncontact and instant detection of phosphor temperature in phosphor-converted white LEDs

Phosphor-converted white light-emitting diodes (pc-WLEDs) have become a major light source in general lighting. To stabilize the photometric characteristics of pc-WLEDs, much effort has been made to manage the heat dissipation of the LED dies. The thermal problems of the phosphor parts, a critical reliability concern for pc-WLEDs, have recently attracted academic interest. This study proposed a practical approach for measuring phosphor temperature in an operating pc-WLED using a noncontact, instant detection method to remotely monitor the emission spectrum. Conventionally, an infrared camera or thermocouples have been used to measure temperature. An IR camera requires good calibration on the emissivity and is usually blocked by the lens or other components covered on the phosphors. Moreover, a thermocouple requires time to reach the thermal equivalence between the detector and the sample under testing, and this approach is destructive when used for inner detection. Our approach has advantages over the conventional methods because it is noninvasive, noncontact, and instant, and inner detection. The approach is also independent of the peak wavelength of pumping lights, the concentration and thickness of phosphor, and correlated color temperatures