Feedback Zero-Current Detection in Synchronous Boost Converters
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Solution Overview
Problem
High-frequency, high-gain on-chip synchronous boost converters suffer from poor power efficiency due to delays in detecting zero current crossing, leading to substantial reverse charging and inefficiencies in Discontinuous Conduction Mode (DCM) operation.
Innovation Solution
Implementing feedback-based Zero Current Detection (ZCD) circuits with switched capacitor integrators and pulse generators to precisely detect zero current crossing, using comparator or Voltage Controlled Delay Line (VCDL) based systems to control switches SW1 and SW2 for accurate timing, thereby preventing reverse currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ZCD circuit with comparator is used to detect zero current crossing, then the circuit structure is simple, but the detection precision is insufficient due to non-zero delays causing reverse charging
Solution Approach 1:
The patent implements a feedback-based ZCD circuit where the voltage across the bypass switch is sensed and fed back to a switched capacitor integrator. The integrator output controls a pulse generator that adjusts the switch turning-off timing in real-time, creating a closed-loop feedback system that precisely detects zero current crossing and eliminates reverse charging current.
2Loss of time
If switch SW2 is turned off later to account for detection delay, then the detection delay is compensated, but reverse charging current increases due to high discharge rate
Solution Approach 1:
The patent uses a bypass switch SW_BP that is turned on before the inductor current actually reaches zero. This preliminary action allows the inductor current to be diverted through the bypass switch in advance, preventing reverse charging current from forming in the first place, rather than attempting to compensate for delay after it occurs.
3Productivity
If high frequency operation is implemented to improve productivity, then the converter efficiency decreases due to substantial reverse charging
Solution Approach 1:
The feedback-based ZCD circuit continuously monitors the voltage across the bypass switch and dynamically adjusts the switch turning-off timing based on real-time current conditions. This feedback mechanism becomes increasingly effective at higher frequencies, enabling precise zero current crossing detection and eliminating reverse charging losses even during high-frequency operation.
Data Source
AI summary
Embodiments disclosed herein relate to synchronous boost converters, and to feedback based zero current detection (ZCD) circuits and operation methods for precisely detecting zero current crossing. The feedback based ZCD circuit may improve power efficiency of a fully on-chip, high gain, and high frequency synchronous boost converter by preventing generation of reverse inductor current in a dead phase of synchronous boost converter. The feedback based ZCD circuit may be a comparator based ZCD circuit for obtaining a precise Discontinuous Conduction Mode (DCM) operation with high efficiency. The feedback based ZCD circuit may be a voltage controlled delay line (VCDL) based ZCD circuit for obtaining a precise DCM operation with high efficiency. The feedback based ZCD circuit may generate a feedback control signal for a switch for accurate and adaptive turning off at all dynamic conditions of various circuits.