Testing Performance of Low Voltage Arresters

Due to important consideration of protection against lightning surge on electrical, electronic and telecommunication equipment, it was necessary to carry out a special study to look at the performance of protective devices. The study was testing performance of arresters on low voltage system. The activity was testing of arresters using steady state and impulse voltages. The arresters consisted of gas tube, zener diode, varistor and spark gap arresters, then it was made a cascade circuit between the varistor and spark gap arresters with a decoupling element. The decoupling elements were used air, iron and ferrite. The test yielded data of current and voltage on the tables and oscilloscope waveforms. The arresters had cut voltages early different from each other, namely the gas tube, zener diode, spark gap and varistor arresters were at the voltages of 500 V, 250 V, 1,000 V and 565 V respectively. The iron core decoupling element cascade circuit had the least oscillation among remaining cores.

High-performance pulse-width modulation AC/DC controller using novel under voltage lockout circuit according to Energy StarⅥstandard

This paper proposes a high-performance pulse-width modulation（PWM） AC/DC controller, which can drive a high-voltage（HV） 650-V power metal-oxide-semiconductor field-effect Transistor（MOSFET） in typical applications of adapters in portable electronic devices. In order to reduce the standby power consumption and improve the response speed in the start-up state, an improved under voltage lockout（UVLO） circuit without a voltage reference source or comparator is adopted. The AC/DC controller is fabricated using a 40-V 0.8-μm onepoly two-metal（1P2M） CMOS process, and it only occupies 1410 × 730 μm^2. A 12 V/2 A flyback topology for quick-charge application is illustrated as the test circuit, which is currently one of the most advanced power adapters in use. Test values show that the turn-on and the turn-off threshold voltages are 19.318 and 8.01 V, respectively. A high hysteresis voltage of 11.308 V causes the value of the power-charging capacitor to decrease to as low as 1 μF to reduce production cost. In addition, the start-up current of 2.3 μA is extremely small, and is attributed to a reduction in the system＇s standby power consumption. The final test results of the overall system are proven to meet the Energy Star Ⅵ standard. The controller has already been mass produced for industrial applications.

A constant-g_m and high-slew-rate operational amplifier for an LCD driver

To drive the backplane of a liquid crystal display device and achieve different kinds of grey levels, a high-slew-rate operational amplifier with constant-gin input stage is presented. A Zener-diode structure is inserted between the tails of the complementary input pairs to keep the grn of the input stage constant. A novel slew rate enhancement circuit is implemented to achieve a very high slew rate. The chip has been implemented in a 0.5μm CMOS process and the chip area of the operational amplifier circuit is 0.11 mm^2. The testing results indicate that in the 5-8 V input range, the maximum gm fluctuation is only 4.2%. The result exhibits a high slew rate of 111 V/μs and 102 V/μs for the rising and falling edges under a 20 pF capacitance load, and the low frequency gain is up to 109 dB with a phase margin of 70 ℃.