Low-Voltage Transconductor with Wide Input Range and Large Tuning Capability

A CMOS triode transconductor was developed with common mode feedback suitable for operating in low-voltage and low-power applications. The design is based on a body-driven input stage with feedback loops to extend both the signal input range and the tuning capability. The effective transconductance of the body-driven triode stage is increased using a partial positive feedback technique which also partially solves the problem introduced by the small transconductance. This design uses the UMC 0.18 μm CMOS process. Simulations show the transconductor operated with 1 V supply voltage has less than -55 dB total harmonic distortions （THD） in the complete tuning range （0 V≤ Vcont≤ 0.43 V） for a 1 MHz 0.8 Vp-p differential input. The power consumption is 70 μW for a 0.43 V control voltage.

A new variable-mode control strategy for LLC resonant converters operating in a wide input voltage range

This paper proposes a new variable-mode control strategy that is applicable for LLC resonant converters operating in a wide input voltage range. This control strategy incorporates advantages from full-bridge LLC resonant converters, half-bridge LLC resonant converters, variable-frequency control mode, and phase-shift control mode. Under this control strategy, different input voltages determine the different operating modes of the circuit. When the input voltage is very low, it works in a full-bridge circuit and variable frequency mode(FB_VF mode). When the input voltage rises to a certain level, it shifts to a full-bridge circuit and phase-shifting control mode(FB_PS mode). When the input voltage further increases, it shifts into a half-bridge circuit and variable frequency mode(HB_VF mode). Such shifts are enabled by the digital signal processor(DSP), which means that no auxiliary circuit is needed, just a modification of the software. From light load to heavy load, the primary MOSFET for the LLC resonant converter can realize zero-voltage switching(ZVS), and the secondary rectifier diode can realize zero-current switching(ZCS). With an LLC resonant converter prototype with a 300 W rated power and a 450 V output voltage, as well as a resonant converter with 20–120 V input voltage, the experiments verified the proposed control strategy. Experimental results showed that under this control strategy, the maximum converter efficiency reaches 95.7% and the range of the input voltage expands threefold.

Implementation of 1.7 kV Silicon Carbide Metal Oxide Semiconductor Field Effect Transistors in Auxiliary Power Supplies for Industrial Applications

An auxiliary power supply(Aux-PS)has become an essential component of electronic equipment for many industrial applications,such as in motor drives,photovoltaic(PV)inverters,uninterruptible power supply(UPS)systems and modular multilevel converters.The introduction of 1700 V silicon carbide(SiC)metal oxide semiconductor field effect transistors(MOSFETs)is useful for such applications,providing benefits with respect to a low on-state resistance,smaller package,low switching loss and single-switching implementation.A single end flyback Aux-PS is designed for industrial applications with a wide input voltage range using 1.7 kV SiC MOSFETs.The special design tradeoffs involved in the usage of SiC MOSFETs are discussed in detail,such as those with regard to gate driving voltage selection,isolation transformer design considerations,and clamping circuit design details.A 60 W demonstration hardware is developed and tested under different working conditions.The results verify the higher efficiency and better thermal performance of the proposed hardware relative to those of traditional Si solutions.