17.9 A High-Conversion-Ratio and 97.4% Peak-Efficiency 3-Switch Boost Converter with Duty-Dependent Charge Topology for 1.2A High Driving Current and 20% Reduction of Inductor DC Current in MiniLED Applications

Today’s miniLED displays can be divided into multiple arrays. Each miniLED array with 900 pixels can have 60 channels where each channel has 15 LEDs connected in series. To drive multi-channel miniLEDs in parallel from a low input voltage $\mathrm{V}_{\mathrm{I}\mathrm{N}}$(=6V), a boost converter with high output voltage (up to 30V) and high output current (up to 1. 2A for 2000 nits) is required where the conversion ratio (CR $=\mathrm{V}_{\mathrm{OUT}}/\mathrm{V}_{\mathrm{I}\mathrm{N}}$) is 5. Since the inductor current $I_{L}=I_{LOAD}/(1-D)$ of the conventional 2-switch (2S) boost converter is high, where $\mathrm{I}_{\mathrm{LO}\mathrm{A}\mathrm{D}}$ is the load current and D is the duty cycle, 2S boost converters have low efficiency and high output voltage ripple. Although the boost converter assisted by a series flying capacitor $\mathrm{C}_{\mathrm{F}}$ can reduce the inductor current level to improve efficiency [1] –[5], $\mathrm{C}_{\mathrm{F}}$ lacks energy under high CR and high loading conditions. At the top of Fig. 17.9.1, both techniques in [1] and [2] charge the $\mathrm{C}_{\mathrm{F}}$ during $\varphi$ 2. ln case of high CR, the duration of $\varphi$ 2 becomes small to seriously affect the charging time. Hence, due to insufficient charge stored in $\mathrm{C}_{\mathrm{F}}$, the driving capability will decrease. At no load (left of Fig. 17.9.2), [1] fails to regulate and D is 0.87 in [2] to haveCR=5. lnterestingly, both$$ [1] and [2] fail to have CR=5 at load current =1.2A. Although additional dual channel-interleaved three-level buck-boost (DTLBB) structure in [1] can alternatively charge two flying capacitors, the hardware overhead is double and the quiescent current becomes high.