P‐45: A Multi‐Phase, High‐Current‐Drivability Charge Pump in Display Driver ICs

Abstract

In this work, a multi-phase charge pump topology is proposed to drive the display driver integrated circuits. To achieve high integration and power efficiency simultaneously, a converter with full-coverage voltage conversion ratios ranging from 1 to 2 n is realized while the count of off-chip capacitors is halved. At the same time, the charging period for each clock phase is designed to be equal and it allows a higher operation frequency of 2 n /(n+1) times while the capacitor can still be fully charged. Based on 0.25 μm process, a three-stage topology has been performed. It has improved the current drivability by 40%-150%. This design is quite suitable for display panels with higher resolution requirements. Author KeywordsMulti-phase charge pump; voltage conversion ratio; charging period; current drivability; display driver. P-45 /H. Lin • SID 2018 DIGEST

P‐58: Efficiency Enhancement by Non‐Overlapping Time Design and Adaptive Ratio Control for Charge Pump of Display Drivers

“…Figure 5 shows the charge pump core and its fourphase clock signals. Compared with previous work in [11], the parameters of the charge pump are same for both schemes. The frequency is set to be 25 kHz, and the parameters of the pumps are shown in Table 1.…”

“…9. Comparison between the proposed charge pump and the one in [11] under the open loop operation for (a) current drivability and (b) efficiency with maximum load. Figure 9 shows the simulation results of the maximum output current and efficiency with maximum load.…”

“…Another flip-flop FF2 is used to pull down the signal ∅ 12 and ∅ 22 without inducing any glitches, as their falling edges are the same as that of ∅ 32 . In the design [11], all pumping stages are kept working even in the condition with low VCRs, which leads to larger dynamic power loss. For lower VCRs of 3 and 4, we only need two pumping stages to transfer the energy and keep the other stage turning on all the time.…”

“…To widen the range of input voltage and output voltage and then improve the total efficiency, more voltage conversion ratios (VCRs) are required while high integration needs be kept [4][5][6][7]. Thus, multi-phase charge pumps are superior since they have achieved efficient utilization of each off-chip capacitor [8][9][10][11]. However, today's multi-phase schemes seldom address the non-overlapping (NON) time of each clock phase, which introduces more unreliability and results in poor product yield.…”

“…Moreover, the multi phases require a more rational clock scheme to improve power efficiency. In the previous work [11], a high integration and multi-phase structure with full-coverage VCRs is proposed, but for the conditions with lower VCRs, a long charging chain and large turn-on resistance result in poor systematic performance. The following work improves the efficiency at lower VCRs (1 to 2 (N-1) ) by automatically bypassing some unnecessary converter stages [13], but its low frequency introduces large voltage loss.…”