A Charge-Sharing-Based Half-Bridge Driver Suitable for Any Duty Cycle With No External Component

A fully-integrated half-bridge driver with dual N-type power transistors is proposed in this paper, which adopts on-chip charge pumps with integrated capacitors based on charge sharing to avoid external bootstrap components. Without bootstrap-capacitor charging paths through low-side power transistors and high-frequency high-power switching nodes, overcharge and large electro-magnetic interference (EMI) can be avoided by eliminating parasitic interconnect inductance and body diode. Adaptive dead time is employed to enhance efficiency, enabling the system to achieve appropriate dead times in various applications. Besides, 100% duty-cycle control is realized by duty-cycle detection and additional continuous charge pump, which can charge the on-chip driver capacitor during on-time, the restriction of minimum off-time is eliminated and the proposed driver can work at full duty cycle range. The proposed charge-sharing-based (CSB) half-bridge driver with any duty-cycle capability embedded in a buck converter with 2A load is implemented in a 0.18 μm BCD technology, which occupies an active area of 0.151mm². Verification results demonstrate that a 2.2 MHz switching frequency is realized with 2.4V–5.5V input voltage and a peak efficiency of 96.8% is achieved for 5 to 4V conversion. The minimum regulation voltage difference between input voltage and output voltage is 70 mV with the help of 100% duty-cycle circuit.