Current-mode DC-DC Buck Converter Research Articles

Type-II Compensation for Automotive Buck Converters Implemented by Fully Integrated Capacitor Multiplier

This paper presents a solution for full integration of a Type-II compensation circuit for DC-DC buck converters. It employs a novel active circuit based on capacitor multiplier, able to emulate the R-series-C ensemble within the conventional Gm-RC compensation network. The proposed solution was used to design a current-mode DC-DC buck converter for automotive applications. The implementation of key circuits in a 180 nm CMOS process is presented in some detail. Simulation results demonstrate that the converter meets all design requirements: it provides a 5 V output voltage over wide ranges of the input voltage, 6 V to 45 V, and load current, between 10 mA and 300 mA. Its frequency and transient responses compare well against the performance of a similar converter that employs a conventional Gm-RC compensation circuit. It consumes 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> more, but requires significantly less die area, than its counterpart. Furthermore, the tuning required to compensate for process and temperature variations is realized by programming the multiplication factor of the capacitor multiplier.

Low-power CMOS integrated current sensor for current-mode DC-DC buck converter

PurposeThis paper aims to propose a low-power complementary MOS (CMOS) current sensor for control circuit in an integrated DC-DC buck converter.Design/methodology/approachThe integrated DC-DC converter, which is composed of feedback control circuit and power block, is designed with 0.35-µm CMOS process. Current sensor in the control circuit is integrated with sense-FET and voltage-follower circuits to reduce power consumption and improve its sensing accuracy. In the current-sensing circuit, the size ratio of the power metal oxide semiconductor field effect transistor (MOSFET) to the sensing transistor (K) is 1,000, and a current-mirror is used for a voltage follower. 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.FindingsExperiment shows that the current sensor is operated with accuracy of more than 85 per cent, and the transient time of the error amplifier is controlled within 100 µs. The sensing current is in the range of a few hundred µA 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 5 per cent.Originality/valueThe proposed current sensor in DC-DC converter provides an accurately sensed inductor current with a significant reduction in power consumption in the range of 0.2 mW. High-accuracy regulation is obtained using the proposed current sensor. As the sensor utilizes simple switch-type voltage follower and sense-FET, it can be widely applied to other low-power applications such as high-frequency oscillator and over-current protection circuit.

Integrated Chip Current Mode DC-DC Buck Converter for Wireless Power Receiver

In this paper, we propose integrated chip DC-DC buck converter for wireless power receiver. The control of DC-DC buck converter is designed by current-mode technique. The DC-DC converter is an essential power management circuit that adjusts the output voltage based on portable electronic device applications. In addition, it reduces the energy loss due to thermal degradation and noise generated at power transmission. Therefore, DC-DC converter that operates at high efficiency is a major design constraint for wide input voltage variation. The proposed DC-DC converter is implemented andfabricated using 0.18μm BCD process. The DC-DC converter comprises of OTA, compensator, current sensing circuit, clock and ramp signal generator and a comparator. It is designed for 85% peak efficiency with a 1MHz switching frequency, 5.5V to 10V input voltage and 400mA maximum load current. The maximum accuracy for sensing current reaches 99%.

Feedback Loop Analysis and Optimized Compensation Slope of the Current-Mode Buck DC-DC Converter in DCM

Frequency characteristics of the total feedback loop of a current-mode buck DC-DC converter in the discontinuous conduction mode (DCM) are examined by formulating an equivalent small-signal transfer function using a proposed block structure that does not suffer direct influence from the current feedback. Utilizing this transfer function, it is clarified that the type of the compensation slope in a current feedback loop affects the loop frequency characteristics in DCM, and in terms of stability, high voltage gain and large 0-dB frequency bandwidth, the quadratic compensation slope is more effective than the linear compensation slope. The validity of the proposed block structure and formulations and the effectiveness of applying a quadratic compensation slope instead of a linear compensation slope in DCM are verified by comparing calculation results, SPICE simulation results and evaluation results using circuit and measurement data from an MOS current-mode buck DC-DC converter IC that had been previously fabricated. More than 10-dB higher voltage gain, three times larger 0-dB frequency bandwidth, more than 10-degree larger phase margin and faster recovery time in load current change are realizable in DCM compared with the case using a linear compensation slope.

A Current-Mode DC–DC Buck Converter with Efficiency-Optimized Frequency Control and Reconfigurable Compensation

Large input voltage range and wide output current range are usually needed for dc-dc converters. For these input and output conditions, the converter's efficiency can be maximized by a proposed method, efficiency-optimized switching-frequency (EOF) control. The optimal switching frequency for maximizing the efficiency is generated by the low-complexity and low-power EOF generator. A reconfigurable compensator is developed for improving the load regulation and the transient response. A piecewise-linear current sensor (PLCS) is employed to reduce controller power loss without sacrificing the sensing accuracy. With the aforementioned three proposed methods, a monolithic current-mode dc-dc buck converter is implemented in a 0.35-μm 3.3-V CMOS process. The measured power-loss reductions and efficiency improvements achieve 16 and 15 mW, and 16% and 1%, both in light and heavy loads, respectively. The load regulation and the transient recovery time are improved by 40 mV and 12 μs, respectively, while the PLCS can reduce 3 mW of power loss. Compared with other published converters in 0.35-μm CMOS process, the implemented converter achieves a higher efficiency of 96.3% and smaller chip area of 0.97 mm.

A Current-Mode Buck DC-DC Converter with Frequency Characteristics Independent of Input and Output Voltages Using a Quadratic Compensation Slope

By using a quadratic compensation slope, a CMOS current-mode buck DC-DC converter with constant frequency characteristics over wide input and output voltage ranges has been developed. The use of a quadratic slope instead of a conventional linear slope makes both the damping factor in the transfer function and the frequency bandwidth of the current feedback loop independent of the converter's output voltage settings. When the coefficient of the quadratic slope is chosen to be dependent on the input voltage settings, the damping factor in the transfer function and the frequency bandwidth of the current feedback loop both become independent of the input voltage settings. Thus, both the input and output voltage dependences in the current feedback loop are eliminated, the frequency characteristics become constant, and the frequency bandwidth is maximized. To verify the effectiveness of a quadratic compensation slope with a coefficient that is dependent on the input voltage in a buck DC-DC converter, we fabricated a test chip using a 0.18µm high-voltage CMOS process. The evaluation results show that the frequency characteristics of both the total feedback loop and the current feedback loop are constant even when the input and output voltages are changed from 2.5V to 7V and from 0.5V to 5.6V, respectively, using a 3MHz clock.

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%.

A Constant Frequency Output-Ripple-Voltage-Based Buck Converter Without Using Large ESR Capacitor

A constant frequency output-ripple-voltage based CMOS current-mode dc-dc buck converter, providing fast load transient response and reference-tracking speed, is proposed in this paper. Unlike V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> control output-ripple-voltage based buck converter, the proposed buck converter can achieve fast and stable load transient response without relying on ESR value of output capacitor. In addition, the proposed converter has faster reference-tracking speed than V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> the control counterparts by about 25 times.