Current-sensing Circuit Research Articles

Open-loop linear differential current sensor based on dual-mode Hall effect

This study proposes a novel double Hall linear differential sensor and investigates its output and temperature characteristics in detail. Finite element method is used to confirm the effectiveness of the proposed method. A practical, open-loop current sensor circuit is designed and constructed based on dual-mode Hall effect theory. Results show that the quiescent output voltage is significantly reduced, and that the signal amplitude is increased by 99.5%. Moreover, sensitivity is more than 40mV/mT, linearity is 1.2% full scale, and the zero drift coefficient is 0.033mV/°C. The differential output model can suppress common mode interference and zero drift. The sensor also exhibits temperature self-compensation and non-linear correction functions.

Integrated Current-Mode DC-DC Buck Converter with Low-Power Control Circuit

A low power CMOS control circuit is applied in an integrated DC-DC buck converter. The integrated converter is composed of a feedback control circuit and power block with 0.35 <TEX>${\mu}m$</TEX> CMOS process. A current-sensing circuit is integrated with the sense-FET method in the control circuit. In the current-sensing circuit, a current-mirror is used for a voltage follower in order to reduce power consumption with a smaller chip-size. The N-channel MOS acts as a switching device in the current-sensing circuit where the sensing FET is in parallel with the power MOSFET. The amplifier and comparator are designed to obtain a high gain and a fast transient time. The converter offers well-controlled output and accurately sensed inductor current. Simulation work shows that the current-sensing circuit is operated with an accuracy of higher than 90% and the transient time of the error amplifier is controlled within <TEX>$75{\mu}sec$</TEX>. The sensing current is in the range of a few hundred <TEX>${\mu}A$</TEX> at a frequency of 0.6~2 MHz and an input voltage of 3~5 V. The output voltage is obtained as expected with the ripple ratio within 1%.

Design and Implement of High-Accuracy On-Line Metal Thickness Measuring Instrument Based on NiosII Processor

The paper proposes a new design of high-accuracy On-line Metal Thickness Measuring Instrument, which was based on EP2C20 series FPGA chip, through adding NiosII soft processor and other interfaces to FPGA, equipped with high precision data collection system and TFT LCD module and so on. The key hardware blocks schematics and components of the RC Oscillation Circuit,eddy current sensor Circuit,rectifier and filter Circuit,A/D converting circuit,FPGA Circuit are described,software flow charts and sample codes are given. According to practice, The measurement range of this system is 1~100 mm and the resolving power is 0.1 μm. degree of linearity is 1%, The system has many features including small volume of hardware, low cost, high detecting precision, convenient operating, high intelligent and so on, leading to broad and bright future. Key words: NiosII processor; eddy current sensor; metal thickness

Current Sensing Circuit Applied to Switching Regulator

A current sensing circuit for current mode switching regulator control circuit is designed, sensing the current through a power switch. Compared with sensing series resistor voltage drop, it reduces the power consumption of a switching regulator, improves efficiency, and sense smaller inductor current. This structure can be used in devices such as mobile phones, tablet PCs power management circuitry.

Integrated BiCMOS Control Circuits for High-Performance DC–DC Boost Converter

This paper introduces the design of integrated BiCMOS current-sensing circuit and amplifier for high-performance current-mode dc-dc boost converter. By exploiting the advantage presented by the integration of both CMOS and bipolar devices within same technology, the BiCMOS circuits offers high-gain amplifier and accurately sensed inductor current. The error amplifier has BJT differential pair and current sources to obtain a fast response, while the current-sensing circuit exploits a current-mirror instead of opamplifier as a voltage follower. The test in 0.35-μm BiCMOS process shows that the transient time of the error amplifier is about 4 μs and the current-sensing circuit can operate with accuracy of 88% at the frequency of 20 kHz. The output voltage of 4.8-8 V is obtained at the input voltage of 3-5 V with the ripple ratio within 5%.

Detection of Faults in SRAM Using Transient Current Testing

Fast development of memory devices cause more area occupation of memory in a chip and the strong market competition have increased the standards of the produced memories. The increased demand on reliability has, in turn, stressed the importance of failure analysis and device testing techniques. More and more effort and thought is being dedicated to the study of testing memory devices with regards to new fault models, fault diagnosis and new memory architectures. In order to detect these faults, March test has been widely used. However, some defects on SRAM cells may not be detected by the conventional March tests. This detection of defects in CMOS SRAM has been a time consuming process. Hence we go for current testing method. This paper implements a transient current testing (IDDT) method to detect defects in CMOS SRAM cells. By monitoring a transient current pulse during a transition write operation or a read operation, defects can be detected. In order to measure the transient current pulse, a current monitoring circuit is designed. Keywords— SRAM, memory testing, March algorithm, IDDT, Current sensor circuit.

Off-the-Line Primary Side Regulation LED Lamp Driver With Single-Stage PFC and TRIAC Dimming Using LED Forward Voltage and Duty Variation Tracking Control

Non-isolation LED drivers [1] are more attractive than isolated drivers in terms of efficiency and lower fabrication cost. However, some areas such as bar-typed fluorescent lamp retrofit applications still require a solution with isolation. Even for replacement of the incandescent and compact fluorescent lamps, some LED lamp makers prefer isolated driver solutions due to safety issues. One of the popular solutions is the flyback converter which is widely used in low-to-moderate power applications [2]. However, generally, it requires secondary voltage or current-sense circuit, and opto-coupler isolator to form a feedback loop. Thus, primary-side regulation (PSR) flyback converters have been steadily used in LED applications since they do not need secondary circuits and isolator [3]. This paper introduces a PSR method for LED lamp which satisfies low price, good efficiency, high power factor (PF) and triode AC switch (TRIAC) dimming control.

A Spurious-Free Switching Buck Converter Achieving Enhanced Light-Load Efficiency by Using a $\Delta \Sigma$-Modulator Controller With a Scalable Sampling Frequency

This paper presents a spurious-free switching buck converter with enhanced light-load efficiency for use in noise-sensitive portable electronics. The proposed switching buck converter achieves low output noise by using a delta-sigma-modulator (ΔΣ) controller. Its light-load efficiency is enhanced by: 1) scaling the switching frequency of the buck converter (i.e., the sampling frequency of its ΔΣ-modulator controller) with the load current; 2) switching its operation from continuous conduction mode (CCM) to discontinuous conduction mode (DCM) at light loads; and 3) using a new low-power current-sensing circuit. The ΔΣ modulator is designed with an input-feedforward architecture, which enables the switching frequency of the controller to be scaled without disturbing the stability of the feedback loop of the buck converter, and also reduces the controller quiescent current. The proposed switching buck converter was fabricated in 0.13-μm digital CMOS. Measurements results demonstrate that this buck converter achieves a spurious-free output with a noise floor below -60 dBm and voltage ripples below 70 mV over its full loading range (2 mA to 800 mA). Furthermore, it achieves a power efficiency higher than 70% over this entire range, with a peak efficiency of 95.1%.

A Current-Sensing Method for Integrated Transformer

Current-sensing circuit is critical for dc-dc converter to achieve current mode control, current protection, and current sharing. Moreover, for voltage regulator module (VRM) applications, the inductor current needs to be sensed for adaptive voltage positioning. A high-frequency, self-driven full-bridge-type VRM has been recently proposed for high efficiency with integrated transformer. However, the existing current-sensing methods are unsuitable for integrated transformer. To solve this problem, this letter proposes a novel current-sensing method for VRMs with integrated transformer. A well-designed capacitor-resistor-sensing network is employed in parallel with the transformer's secondary side, and then the voltage across the capacitor is sensed to monitor the transformer magnetizing inductor current instantaneously. This method is accurate, lossless, and simple in structure. A 1.2-V/130-A output voltage regulator module is built in the laboratory to verify the proposed method.

High Performance Current-Mode DC-DC Boost Converter in BiCMOS Integrated Circuits

A simulation study of a current-mode direct current (DC)-DC boost converter is presented in this paper. This converter, with a fully-integrated power module, is implemented by using bipolar complementary metal-oxide semiconductor (BiCMOS) technology. The current-sensing circuit has an op-amp to achieve high accuracy. With the sense metal-oxide semiconductor field-effect transistor (MOSFET) in the current sensor, the sensed inductor current with the internal ramp signal can be used for feedback control. In addition, BiCMOS technology is applied to the converter, for accurate current sensing and low power consumption. The DC-DC converter is designed with a standard 0.35 <TEX>${\mu}m$</TEX> BiCMOS process. The off-chip inductor-capacitor (LC) filter is operated with an inductance of 1 mH and a capacitance of 12.5 nF. Simulation results show the high performance of the current-sensing circuit and the validity of the BiCMOS converter. The output voltage is found to be 4.1 V with a ripple ratio of 1.5% at the duty ratio of 0.3. The sensing current is measured to be within 1 mA and follows to fit the order of the aspect ratio, between sensing and power FET.

A high-PSR transient-enhanced output-capacitorless CMOS low-dropout regulator for SoC applications

A transient-enhanced output-capacitorless CMOS low-dropout voltage regulator (LDO) with high power supply rejection (PSR) is introduced for system-on-chip applications. In order to reduce external pin count and device area and be amenable to full integration, the large external capacitor used in the classical LDO design is eliminated and replaced with a much smaller 5.7 pF on-chip capacitor. High-gain folded-cascode stage, wideband common source stage, voltage subtractor stage and transient-enhanced circuit are designed altogether to realise circuit compensation and achieve good frequency and transient performances. A current-sensing and transient-enhanced circuit is utilised to reduce transient voltage dips effectively and efficiently drive different kinds of load capacitances. The active chip area of the proposed regulator is only 200 × 280 µm2. The simulation results under mixed-signal 0.18 µm 1P6M process show that this novel LDO's output voltage can recover within 1.7 µs (rising) and 2.41 µs (falling) under full load-current changes. The input voltage is ranged from 2 to 5 V for a load current 50 mA and an output voltage of 1.8 V. This novel LDO has wide unity-gain frequency stability and is stable for estimated equivalent parasitic capacitive loads from 0 to 100 pF. Moreover, it can achieve a PSR of −78.5 and −73 dB at 1 and 10 kHz, respectively.

Design and implementation of a socket with zero standby power using a photovoltaic array

This paper further enhances our previous research into reducing the standby power of electric home appliances. Turned-off electric home appliances generally still require standby power when they are plugged in. We present a way to reduce the standby power of a socket. Our socket supplies the appliances with power when the user turns them on. When the user turns them off, our socket shuts the electric power off and thus reduces the standby power. Our design, which uses an MCU, receives signals from a PIR sensor which detects the user approaching the socket. The MCU controls the SSR On/Off when used as an appliance switch for shutting off the standby power. A load current sensor circuit provides a signal to the MCU to keep the SSR on until the appliance has finished its work. The MCU monitoring program provides both automatic detection of the user by the PIR sensor and detection of the load current. The MCU with low-power technology has internal modules to simplify the hardware circuit design. The PV array is added in our design to reduce the consumption from the local electric power company. The standby power consumption of an appliance with our new design is 7 mW in a darkroom and less than 7 mW in a non-darkroom. When the illumination intensity suffices, the consumption is 0 W from the local electric power company.

An Integrated Speed- and Accuracy-Enhanced CMOS Current Sensor With Dynamically Biased Shunt Feedback for Current-Mode Buck Regulators

This paper presents a new compact on-chip current-sensing circuit to enable current-mode buck regulators operating at a high switching frequency for reducing the inductor profile. A dynamically biased shunt feedback technique is developed in the proposed current sensor to push nondominant poles to higher frequencies, thereby improving the speed and stability of the current sensor under a wide range of load currents. A feedforward gain stage in the proposed current sensor also increases the dc loop-gain magnitude and thus enhances the accuracy of the current sensing. A current-mode buck regulator with the proposed current sensor has been implemented in a standard 0.35-μm CMOS process. Measurement results show that the proposed current sensor can achieve 95% sensing accuracy and <;; 50-ns settling time. The buck converter can thus operate properly at the switching frequency of 2.5 MHz with the duty cycle down to 0.3. The output ripple voltage of the regulator is <;; 43 mV with a 4.7-μF off-chip capacitor and a 2.2-μH off-chip inductor. The power efficiency of the buck regulator achieves above 80% over the load current ranging from 25 to 500 mA.

A 400-mA current-mode buck converter with a self-trimming current sensing scheme

A current-programmed mode (CPM) controller is designed for improved DC---DC converter control. The key building block of the CPM controller is an accurate current-sensing circuit. This paper proposes a lossless current-sensing technique to measure the inductor current by measuring the current through the power transistor. A self-trimming circuit is used to compensate for any inaccuracies caused by voltage and temperature variations. The measurement results validate the operation of the fabricated chip.

출력전류 제어 기능이 향상된 고휘도 LED 구동 IC 설계

In this paper, High brightness LED (light-emitting diodes) driver IC (integrated circuit) using new current sensing circuit is proposed. This LED driver IC can provide a constant current with high current precision over a wide input voltage range. The proposed current-sensing circuit is composed of a cascode current sensor and a current comparator with only one reference voltage. This IC minimizes the voltage stress of the MOSFET (metal oxide semiconductor field effect transistor) from the maximum input voltage and has low power consumption and chip area by using simple-structured comparator and minimum bias current. To confirm the functioning and characteristics of our proposed LED driver IC, we designed a buck converter. The LED current ripple of the designed IC is in <TEX>${\pm}5%$</TEX> and a tolerance of the average LED current is lower than 2.43%. This shows much improved feature than the previous method. Also, protections for input voltage and operating temperature are designed to improve the reliability of the designed IC. Designed LED driver IC uses 1.0 <TEX>${\mu}m$</TEX> X-Fab. BiCMOS process parameters and electrical characteristics and functioning are verified by spectre (Cadence) simulation.

Novel circuit design for two-stage AC/DC converter to meet standby power regulations

The objective of this study is to design and implement an AC/DC converter in order to meet the standby power specification. The design of auxiliary circuit (including start-up circuit) and power factor correction (PFC)-OFF control which significantly reduces the standby power to meet the energy code under standby condition will be presented. Moreover, it will be shown that these circuits do not need any current sensor and hysteresis circuit to detect the load condition, which can reduce the cost and avoid false activation caused by current noise. The specifications of the converter are as follows: universal input voltage: 90–265 VAC, 50–60 Hz; output voltage: 19 VDC; output power: 250 W; standby power: input power &lt;1 W at 265 VAC input. Experimental results have demonstrated that the input power factor is greater than 98% in the whole voltage range and full load condition. The power consumption under standby condition is less than the specified value, 1 W, confirming the design and implementation.

Magnetically Coupled Current Sensors Using CMOS Split-Drain Transistors

Integrated current-sensing circuits intended for smart-power and embedded applications featuring galvanic isolation are implemented. They are based on magnetic detection using a CMOS-compatible split-drain transistor that provides a very linear output current versus magnetic field. Two approaches are used to generate the magnetic field: the coil approach and the strip approach. In the first, the current to be sensed flows through an integrated coil placed atop the split-drain transistor and produces a magnetic coupling strong enough to cause a detectable current. The second approach features an array of 126 paralleled split-drain transistors placed along a metal strip intended to carry higher current levels. Both techniques were realized as integrated current sensors built in 0.35 mum CMOS technology. The calculated and measured sensitivities were around 1 and 0.75 muA/A for the coil and strip approaches, respectively. For a typical single split-drain bias current of 50 muA, the minimum detectable currents within 1 Hz are 2.8 and 42 muA/radicHz for the coil and strip approaches, respectively. The strip can carry currents up to 500 mA, whereas the flowing current in the coil is limited to 20 mA. Thus, the choice is based on the resolution and sensing current level of the application.

Design of anti-jamming current-sensing circuit for current-mode buck regulator

A novel anti-jamming integrated CMOS current-sensing circuit for current-mode buck regulators is presented. Based on the widely-used traditional current-sensing structure, anti-jamming performance is improved significantly by adding on-chip capacitors and one-shot circuit. Also the transient response is faster through the introduction of current offset. The circuit is concise, simple to implement and suits for SoC applications with single power supply. A dual-output current-mode DC-DC buck converter with proposed structure has been fabricated with a 0.5 μm CMOS process for validation. In the 2.5–5.5 V input range, the two channels work steadily in the load current range of 0–600 mA. And the measured maximum efficiency is up to 96%.

Current-Controlled Nanospray Ionization Mass Spectrometry

The hypothesis that direct determination of electrospray current would provide a viable method for maintaining spray stability to enable optimal nanospray analysis was tested by building a feedback apparatus capable of reading the current and readjusting the emitter voltage in real time. The apparatus consists of a current-sensing circuit that reads the voltage drop across a resistor located between the high-voltage power supply and the nanospray emitter. A low voltage proportional to the observed current is generated and sent to a data acquisition card. The information is used by a proportional-derivative-integral (PID) algorithm to calculate the magnitude of a low-voltage signal that is used to control the power supply output. Any variation of current across the sensing resistor is thus counteracted by an opposite-direction variation of the high voltage applied to the nanospray emitter. In this way, the apparatus adjusts the emitter voltage to achieve a preset value of current, which it strives to maintain over time in spite of any possible variation of the parameters influencing the spray regime. Preliminary results have shown that the feedback apparatus is capable of establishing and maintaining stable spray for samples that are usually considered challenging in traditional voltage-controlled analysis, such as those consisting of nucleic acid solutions with high salt loads. For these types of samples, the total ion count recorded in current-controlled mode was significantly more stable than that observed in voltage-controlled mode. At the same time, overall signal intensities and signal-to-noise ratios were also significantly improved. Setting the target nanospray current to a predefined value and letting the apparatus reach the target without operator intervention enabled the acquisition of viable data from solutions containing up to 2.5 M ammonium acetate, which are ordinarily difficult by traditional manual tuning. A deeper understanding of the current-voltage relationships for samples of very different compositions is expected to enable one not only to predict the target current that should be used for a certain analysis, but also to devise algorithms to change such target as a function of predictable variations of sample properties and analytical conditions. This will allow for optimal performance to be maintained during on-line gradient chromatography in which the nature of the sprayed solution may vary very widely during the course of the analysis.

On-chip CMOS current-sensing circuit for DC-DC buck converter

An on-chip CMOS current-sensing circuit for a DC-DC buck converter is presented. The circuit can measure the inductor current through sensing the voltage of the switch node during the converter on-state. By matching the MOSFETs, the achieved sense ratio is almost independent of temperature, model and supply voltage. The proposed circuit is suitable for low power DC-DC applications with high load current.