A 3.5-A Buck DC-DC Regulator with Wire Drop Compensation for
Remote-Loading Applications
Lei Zhu
1
, Qi Cheng
1
, Jianghui Deng
1
, Jianping Guo
2, 3
*, Dihu Chen
2, 3
, and Xidong Ding
1
1
School of Physics and Engineering, Sun Yat-sen University, Guangzhou, China
2
School of Microelectronics, Sun Yat-sen University, Guangzhou, China
3
SYSU-CMU Shunde International Joint Research Institute, Foshan, China
* Email: guojp3@mail.sysu.edu.cn
Abstract
Voltage drop introduced by long cable cannot be
neglected any more in high-power remote-loading
applications, e.g., power adaptor for the charger of
modern smart phones or tablets. In this paper,
self-adaptive wire drop compensation (WDC) schemes
for DC-DC regulator have been proposed and discussed.
A 3.5-A buck DC-DC regulator with the proposed WDC
circuit has been implemented in 0.6-μm CMOS
technology. Simulation results show that the load
regulation (0.004 V/A) is typically improved by 51 times
than the circuit without WDC when load current changes
from 0.5 A to 3 A.
1. Introduction
Power management integrated circuits (ICs) are
commonly used in portable device, such as smart phone,
tablet PC and laptop etc. Current trend shows that
portable smart devices with multi-core high-frequency
CPU and large touch-screen are popular. These
inevitably increase power consumption and also lead to
the demands of high-capacity batteries. Also, power
adaptors are needed to provide enough power to charge
device for saving charging time. In this case, DC-DC
regulators with large output current are in demand for
battery-powered portable electronic devices. As a
consequence, the charging current of mobile phone has
been boosting gradually from 350 mA to 2000 mA (some
application such as tablet PCs even reach 2400 mA).
Normally, in low-current application the resistance of
transmission wire can be neglected. However, as the
charging current becomes larger and larger, the voltage
drop caused by wire resistance cannot be ignored any
more. As stated in [1], the distributive voltage and
current control methodology is needed to prolong the
battery life. Traditional compensation approach is adding
a roughly estimated voltage to ideal output (e.g., a
pre-set 5.2 V output for a 5 V nominal system). However,
this methodology is prone to be inaccurate for load
voltage in remote-loading and high-current applications.
Some approaches were proposed to fulfill wire drop
compensation (WDC) [2–4], but they are not suitable for
DC-DC regulators. Even though compensation schemes
proposed in [5–7] were designed for DC-DC regulators,
compensation circuits in [5, 6] are rather complex and
bipolar transistors are needed in the circuit in [7].
Moreover, the amplifier used in WDC scheme [7] is
difficult to design.
In this paper, we developed a precise and
self-adaptive scheme to fit the above requirements.
Owing to the advantages of fast dynamic response and
automatic over-current protection [8], this design is
based on a current-mode pulse-width-modulation (PWM)
buck DC-DC regulator.
The rest of this paper is organized as follows.
Architecture of proposed DC-DC regulator is described
in Section II. Operation principle and circuit design of
proposed WDC are presented in Section III. Simulation
results are shown in Section IV and the conclusion is
drawn in Section V.
2. Architecture for the Proposed Buck DC-DC
Regulator with WDC
This work was supported in part by a grant from National Natural
Science Foundation of China (61204035) and a grant from Guangdong
Natural Science Foundation (2015A030313154)
VIN
Mp
Mn
VX
L
Cout
RF
RG
VFB
Vout
Rload
Rcs
Rw1
Rw2
Logic Control
Vref
VFB
cmp
EA
Current
Limit
Over Current
Protection
Current
Sensor
Wire Drop
Compensation
Vcs
Dead-Time
Control
On Chip
Figure 1. Block diagram of current-mode buck
DC-DC regulator with proposed WDC circuit