Charge Pump Buck Converter Droop Reduction Circuit
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Solution Overview
Problem
Existing buck-boost converter solutions for DC power supplies are inefficient, requiring large circuit areas and experiencing significant resistive losses, especially when transitioning from low-voltage, low-power to high-voltage, high-power supplies, and suffer from voltage droop issues during rapid input voltage changes.
Innovation Solution
The proposed charge pump buck power converter (CPBC) combines a charge pump stage for step-up conversion and a buck converter stage in parallel, with control circuitry that includes a voltage sensor, voltage level generator, and an under-voltage monitor block to minimize voltage droop by adjusting the duty cycle and providing additional energy to the inductor during handoff from the charge pump to the buck stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional buck-boost converter is used for power supply conversion, then voltage conversion capability is achieved, but power efficiency deteriorates and resistive losses increase
Solution Approach 1:
The power conversion function is segmented into two separate stages: a charge pump stage for voltage multiplication and a buck stage for regulated output. Each stage operates independently with optimized components, reducing overall resistive losses compared to a single-stage buck-boost converter.
Solution Approach 2:
The charge pump and buck converter stages are combined in a cascaded configuration where the charge pump output feeds the buck converter input. This merging allows the system to leverage the high efficiency of the charge pump for voltage boosting while maintaining the regulated output of the buck stage, achieving superior overall efficiency.
2Area of stationary object
If a conventional buck-boost converter is used, then voltage conversion is achieved, but circuit area increases
Solution Approach 1:
By separating the voltage conversion functions into distinct charge pump and buck stages, each stage can use smaller, optimized components. The charge pump uses capacitors instead of large inductors, and the buck stage uses a smaller inductor due to the pre-boosted input voltage, reducing total circuit area.
Solution Approach 2:
The charge pump stage changes the voltage parameter before the buck stage, allowing the buck stage to operate with smaller magnetic components. This parameter transformation enables compact component sizing while maintaining full power supply capability.
3Stability of the object's composition
If the buck control loop bandwidth is limited, then system stability is maintained, but voltage droop increases during rapid input voltage changes
Solution Approach 1:
The charge pump stage performs preliminary voltage boosting before the buck stage processes the signal. During rapid input voltage changes, the charge pump quickly establishes a higher input voltage for the buck stage, providing headroom that prevents output voltage droop while the control loop maintains stability.
Solution Approach 2:
The charge pump acts as an intermediary stage between the input voltage source and the buck converter. It mediates rapid voltage changes by providing a buffered, pre-regulated input to the buck stage, isolating the buck control loop from transient disturbances while maintaining output voltage reliability.
4Device complexity
If the charge pump and buck stage operate at the same voltage level, then circuit simplicity is maintained, but voltage regulation precision deteriorates
Solution Approach 1:
The control circuitry is designed with local quality optimization: the charge pump control operates at one voltage level with its own reference, while the buck stage control operates at a different voltage level with its own reference. This allows each stage to be precisely regulated for its specific operating conditions, improving overall voltage regulation precision.
Solution Approach 2:
Separate feedback loops are implemented for each stage, with the charge pump feedback ensuring accurate voltage multiplication and the buck stage feedback ensuring precise output regulation. This dual feedback approach achieves high precision without requiring complex cross-regulation circuitry.
Data Source
AI summary
A Charge Pump Buck Converter (CPBC) includes a BC including an inductor and a CP coupled in parallel. Control logic is coupled to a switch driver coupled to a power switch(es). Control circuitry includes a voltage sensor sensing Vout and a voltage level generator for generating a first voltage level coupled to the CP stage and a second voltage level coupled to a duty cycle/rate generator block providing an input to an under voltage (UV) monitor coupled between OUT and the control logic. The control circuitry disables the CP when Vout>a first Vout level and controls the BC to regulate to a second Vout level>the first Vout level. During handoff between CP and BC during power up if Vout drops below a UV threshold, the UV monitor block modifies an input applied to the control logic for increasing charging supplied to the inductor.