Charge Pump Holding-Mode Control for Light-Load Efficiency
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Solution Overview
Problem
Charge pumps face inefficiencies in light load conditions, resulting in low overall efficiency, as they typically operate below half of the input voltage and enter an idle state, disconnecting capacitors from the input, leading to reduced performance.
Innovation Solution
A control circuit and method for a charge pump that uses two bridge arms and capacitors, with a judging circuit and logic circuit to provide complementary control signals, keeping one capacitor coupled between the input and output nodes and the other between the output and ground, allowing efficient operation by maintaining capacitors connected during light loads and flipping control signals based on hysteretic comparisons of output voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the charge pump operates in traditional mode with capacitors disconnected during light load, then the device enters idle state to save energy, but the efficiency drops and output voltage stability deteriorates
Solution Approach 1:
The patent applies dynamics by implementing a dual-mode control mechanism that dynamically switches between traditional idle mode and new holding mode based on load conditions. The judging circuit continuously monitors output voltage and transitions between modes: in light load conditions, it maintains capacitors connected in holding mode for stability; in heavy load conditions, it switches to idle mode for efficiency. This dynamic adaptation resolves the contradiction between energy saving and voltage stability.
Solution Approach 2:
The patent changes the operational parameters of the charge pump by modifying the connection state of capacitors during light load conditions. Instead of disconnecting capacitors (traditional mode), the invention keeps them connected and changes their configuration to maintain holding capability. The logic circuit adjusts control signals to maintain output voltage above threshold levels, transforming the parameter of capacitor connection state from binary (connected/disconnected) to a three-state system (connected in holding mode, connected in idle mode, disconnected), thereby improving both efficiency and stability.
2Power
If the charge pump uses traditional control with inductors and control loops, then voltage conversion is achieved, but the size increases and efficiency decreases
Solution Approach 1:
The patent extracts and removes the inductor component from the charge pump structure, replacing the traditional inductor-based DC-DC converter architecture with a capacitor-based charge pump architecture. By taking out the inductor and control loop, the invention achieves voltage conversion through capacitor switching alone, significantly reducing device size and structural complexity while maintaining voltage conversion capability.
Solution Approach 2:
The patent substitutes the mechanical/magnetic energy storage mechanism (inductor) with an electrical field-based mechanism (capacitor). The inductor-based magnetic field energy storage is replaced by capacitor-based electric field energy storage, enabling voltage conversion through electrostatic charge pumping rather than electromagnetic induction. This substitution eliminates the need for bulky inductors and complex control loops, reducing device complexity while preserving power conversion functionality.
3Ease of operation
If the charge pump operates below half of input voltage in traditional mode, then the switching operation is simplified, but the output voltage range is limited and efficiency is reduced
Solution Approach 1:
The patent implements dynamics by creating a voltage-threshold-based dual-mode operation system. The judging circuit monitors output voltage and dynamically determines operating mode: when output voltage exceeds the threshold (Vout > Vin/2), the system enters holding mode with complementary switch control to maintain voltage; when output voltage is below threshold (Vout < Vin/2), the system switches to traditional idle mode. This dynamic mode switching expands the output voltage range while maintaining operational simplicity through standardized switching patterns in each mode.
Solution Approach 2:
The patent applies periodic action through the cyclic switching of capacitors between charging and holding states. In holding mode, the charge pump operates with periodic capacitor switching that maintains output voltage above the threshold level, creating a sustained periodic charge transfer mechanism. This periodic operation enables the system to maintain elevated output voltages continuously during light load conditions, expanding the effective output voltage range beyond the traditional half-input-voltage limit while preserving the simplicity of periodic switching control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the charge pump's efficiency by maintaining capacitors connected, allowing the output voltage to exceed half of the input voltage, thereby improving efficiency from 98% to 99% and prolonging the holding mode, reducing output voltage drops and increasing overall performance.
Implementation Method 1
The judging circuit is configured to provide a mode signal by comparing the output voltage of the charge pump with a first threshold voltage and a second threshold voltage via a hysteretic comparison
Data Source
AI summary
A charge pump comprises two bridge arms coupled in parallel, two capacitors, and a control circuit. Each bridge arm has two pairs of switches coupled in series, each pair of switches having two switches coupled in series through a common node. Each capacitor is connected between the two common nodes of the corresponding bridge arm. The control circuit provides a mode signal by comparing an output voltage of the charge pump with two threshold voltages via a hysteretic comparison, and provides two control signals with opposite logic states based on the mode signal to control each pair of the switches to work complementarily, wherein the logic states of the control signals flip in response to transiting from a first status to a second status of the mode signal, and maintain in response to transiting from the second status to the first status of the mode signal.