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A digital pulse width modulation closed loop control LDMOS gate driver for LED drivers implemented in a 0.18 μm HV CMOS technology | IEEE Conference Publication | IEEE Xplore

A digital pulse width modulation closed loop control LDMOS gate driver for LED drivers implemented in a 0.18 μm HV CMOS technology


Abstract:

For multicolor LED driver applications several integrated high voltage (HV) LDMOS transistors in ASICs have to be driven efficiently and securely. The presented digital P...Show More

Abstract:

For multicolor LED driver applications several integrated high voltage (HV) LDMOS transistors in ASICs have to be driven efficiently and securely. The presented digital PWM gate driver is based on gate charge modulation (GCM) and employs a digital centric closed loop gate-source voltage (VGS) control to ensure stable operation over a large temperature and supply voltage range. This enables secure operation close to the maximum VGS of the LDMOS transistors and operating point dependent VGS tuning to optimize the LED driver efficiency. Due to the short minimum on-time and its fast control loop, the converter operates at higher switching frequency, which leads to smaller passive components. In addition the DPWM driver directly drives 5 V and 20 V gate-oxide transistors out of the 24 V supply without requiring any external components. Hence, the LED driver's BOM is kept as low as possible further lowering its cost and PCB area. The DPWM driver has been fabricated in a 0.18 μm HV CMOS technology and occupies 0.35 mm2 to operate a 331 pF load. Its digital centric closed loop VGS control maintains the desired target value despite temperature variations from 27 °C-70 °C and supply voltages changes of more than 10 V with rise and fall times of 12 ns/7 ns.
Date of Conference: 30 April 2017 - 03 May 2017
Date Added to IEEE Xplore: 27 July 2017
ISBN Information:
Electronic ISSN: 2152-3630
Conference Location: Austin, TX, USA

I. Introduction

Due to efficiency, high quality solid-state lighting requires multi-color LED drivers. To achieve a small and cost efficient solution for these applications the single-inductor multiple-output (SIMO) LED driver has been developed [1]. This architecture depicted in Fig. 1 requires only a single inductor and no output capacitors for driving four LED strings of different forward voltages. Therefore, one high-side (HS) 5 V gate-oxide transistor M0 for charging the inductor and four low-side (LS) 20 V gate-oxide transistors which select the active LED string have to be controlled individually. Hence, in total five gate drivers are required which have to be very area efficient to keep the size of the whole ASIC as small as possible. In addition, the SIMO LED driver consists of a high-side shunt current sensing circuit and a digital current and color control.

References

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