Cascoded GaN half-bridge with 17-MHz wide-band galvanically isolated current sensor

A cascoded GaN half-bridge with wide-band galvanically isolated current sensor is proposed. A 650-V depletion-mode GaN FET is switched by a low-propagation-delay gate driver in active-mode. The standby and active modes are switched by a 25-V N-ch LDMOS. The current sensor uses the LDMOS as a shunt resistor, gm-cell-based sense amplifier and mixer based isolation amplifier for wider bandwidth. PVT variations of on-resistance of the current-detecting MOSFET are compensated using a reference MOSFET. A digital calibration loop across the isolation is formed to keep the current sensor gain constant within ±1.5% across the whole temperature range. The wide-band current sensor can measure power device switching current. In this study, a cascoded GaN half-bridge switching and inductor current sensing using low-side and high-side device current are demonstrated. The proposed techniques show the possibility of implementing a GaN half-bridge module with isolated current sensor in a package.

A Wide-Band High-Resolution Transmitter for Optical Isolation Amplifier

A wide-band and high-resolution transmitter of optical isolation amplifier is proposed for switching power supply isolation and servo motor drive applications. The transmitter is based on the chopper-stabilized technique and sigma delta modulator. A built-in common-mode voltage circuit of switched capacitor is proposed to ensure the stability of input DC common mode. Meanwhile, the feedback capacitor is used to improve the driving ability, which helps to avoid a buffer with large input swing. The circuit is tapeout with GF CMOS 0.18 μm 1P6M process with 5 V power supply. The test results show that in 5 V supply voltage, the input swing of transmitter is 2 V and the effective signal bandwidth is 110 kHz. And the output resolution achieves 11 bit.

Study on Application of Decoupling Circuit to I&C System of Nuclear Power Plant

Electrical isolation is required for signal exchanging between redundant I&C divisions. Relay and isolation amplifier are often used as the isolation device for binary and analog signal transmission. Simple isolation device is not enough to make the electrical isolation. Decoupling circuit which is the combination of isolation devices and an independent power supply can totally compensate the insufficiency of simple isolation device and prevent the electrical fault propagating along the signal exchanging circuit.