Jianxiong Xi

Multi-mode control strategy for primary-side regulation system

A multi-mode control strategy for primary-side regulation (PSR) system is presented. The idea uses four mode control strategy to improve the efficiency under variety load conditions. In addition, the usual peak current control mode is replaced by voltage control mode under standby condition. By this way, the pulse width of drive signal can be reduced regardless of the leading edge blanking time in the peak current control mode when the power switch turns on. Thus the standby power can be reduced when the system switching frequency remains the same as conventional system. The prototype is achieved by using CSMC 700V BCD technology. The experiment results show that the average efficiency is improved about 3.6% comparing with conventional system and the standby power is less than 10mW under different conditions.

A linear constant current LED driver without off-chip inductor and capacitor

A linear constant current light-emitting diode (LED) driver without off-chip inductor and capacitor is presented in this paper. The proposed driver consists of one resistor, one diode bridge and one controller integrated circuits (IC). The controller IC employs four LED strings and sequences their conduction to shape the output current in proportion to the input voltage. The controller IC was designed and implemented by using HHNEC 1μm 700V process. The experimental results show that high PF of 97.93% and efficiency of 90.41% under the input voltage of 220V|rms utility voltage were obtained.

An electrolytic-capacitorless and inductorless AC direct LED driver with power compensation

In this paper, a novel system for driving LEDs directly from AC supply without the use of electrolytic capacitors and inductors is proposed. The system includes a power compensation module, enabling the output power of LED approximately constant if there is a fluctuation in input voltage. Unlike the conventional LED drivers, the proposed LED driver only employs one rectifier, one controller IC, four LED strings and a few chip resistors and capacitors. The four LED strings will automatically conduct according to the level of input voltage, thus creating a step-shaped input current proportional to the sinusoidal voltage waveform. By this means, high power factor is achieved. The controller IC is designed by using CSMCs 0.8-μm 650V process. Simulation results show that the LED driver has a high power factor of 97.46% and efficiency of 90.64% under the 220V|rms utility input voltage.

A dimmable and power-compensated AC direct LED driver with high efficiency

A dimmable and power-compensated AC direct LED driver with high efficiency for lighting applications is presented. A Source-Coupled Pair (SCP) is adopted to realize the soft self-commutating. There is no additional sensing or control circuitry, which lower the system power dissipation. A pulse-width modulation (PWM) dimming technique is applied in regulating the LEDs brightness. Furthermore, the driver includes a Power Compensation module which enables the output power of LEDs approximately constant under various line voltage. The LED driver IC is designed and implemented in CSMCs 700 V 1 um BCD process. The post-layout simulation results show that under 220 V|rms AC voltage, the driver has a high efficiency of 90.28% and realizes dimming with a 90% duty ratio, 10 KHz dimming signal. The output power compensated only changes 4% under a 10% variation in input voltage.

A synchronous boost converter with high speed and high accuracy peak current control unit

A 3 MHz, 48W Boost converter with high speed and high accuracy Peak Current Control Unit (PCCU) is presented. The Boost controller IC adopts a novel PCCU consisting of a fully differential open-loop operational transconductance amplifier (OTA) and a trans-impedance amplifier (TIA), which can minimize the delay and error of the whole control loop. In the PCCU, the compensated output of error amplifier is moved forward to improve the control accuracy further. This IC is designed in CSMC 0.8 um 60 V BCD process. The simulation results show the Boost converter operates at 3 MHz and the peak current control error is 1.3% under the worst situation. The delay of peak current trigger point to the low side gate driver (LDRV) output is 25.14 ns and the delay of the compensated output of error amplifier to LDRV output is 37.56 ns.

A front-end circuit with 16-channel 12-bit 100-kSps RC-hybrid SAR ADC for industrial monitoring application

A front-end circuit with 16-channel 12-bit 100-kSps RC-hybrid successive approximation register (SAR) analog-to-digital converter (ADC) for industrial monitoring application is presented. The front-end circuit can process a wide range input voltage as large as 10 V which is beyond the supply voltage, with the help of voltage divider preceding an analog multiplexer. A programmable gain amplifier (PGA) is used to convert different input voltage ranges into a same one. A RC hybrid digital-to-analog converter (DAC) is employed in SAR ADC to avoid calibration requirement for the bridge capacitor which is usually needed for a split capacitor SAR ADC architecture. Serial peripheral interface (SPI) is integrated in the design for communication and configuration. The prototype circuit fabricated in a 0.18 um 3.3 V CMOS process shows the measured DNL and INL within −0.82/+0.68 LSB and −0.85/+0.82 LSB, respectively. The circuit consumes 2.04 mW with a 3.3 V supply voltage. The whole chip occupies an area of 1.844 × 1.387 mm2.

A constant current LED driver based on flyback structure with novel primary side control

A primary side control LED driver with a novel constant current control mechanism is proposed in this paper. In order to simplify the peripheral circuits, the proposed driver employs two cascaded power MOSFETs to eliminate auxiliary winding. The resonance occurs in the transformer will couple to the connection of power MOSFETs. Thus the system can obtain the demagnetization information by sampling the resonance. Based on this, the system can output constant current by adopting charging and discharging module. The control IC has been designed in CSMCs 0.8-μm 600V process. Simulation results show that the average output current precision is within +4.7% and the demagnetization time detection error is less than 0.2%.

Design of a high precision chip for detecting electric arc

A novel kind of chip which is used in high precision and low cost arc detection circuit (leakage detection included) was designed. Based on CSMCs 0.5pm process, the pad is specially designed to produce a specific capacitor. Cascode current mirror and trimming capacitors are used to generate a precise timing signal. High speed, large bandwidth and low offset op-amps with rail to rail output stage are used to realize the function of precise amplification of the current information. The chip is designed and simulated on the platform of Cadence. The experimental result shows that the chip can detect arc which is wider than 150ns and generate the corresponding interrupt signal.