Bipolar Charge Pump Switching for Fewer Flying Capacitors
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Solution Overview
Problem
Bipolar output voltage charge pump circuits face inefficiencies in power consumption and size, particularly in portable electronics, due to the need for multiple flying capacitors and high power requirements for varying output signal levels and supply voltages, which increases cost and physical size.
Innovation Solution
A charge pump circuit with a network of switching paths and a controller that uses only two flying capacitors to generate a range of bipolar output voltages (±VV/3, ±VV/4, ±VV/5, ±VV/6) by sequencing switching states, with at least one NMOS switch on a semiconductor substrate isolated by n-well regions, allowing for efficient operation across different supply voltages and load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple flying capacitors are used to provide different bipolar output voltages, then the adaptability to different supply voltages is improved, but the device complexity and physical size increase
Solution Approach 1:
The single flying capacitor is designed to perform multiple functions by being switched into different circuit configurations. The controller sequences the switching paths to connect the flying capacitor to different nodes (input, output, reference) at different times, enabling the same capacitor to generate multiple output voltage ratios (±VV/2, ±VV/3, ±VV/4, ±VV/5, ±VV/6) from a single component, thereby eliminating the need for multiple dedicated capacitors for each voltage ratio
2Adaptability or versatility
If multiple flying capacitors are used to provide different bipolar output voltages, then the adaptability to different supply voltages is improved, but the physical size of the circuit increases
Solution Approach 1:
The patent merges the functionality of multiple flying capacitors into a single flying capacitor by using a unified switching network. The controller coordinates the switching paths to sequentially connect the single flying capacitor to different circuit nodes, effectively combining what would have been separate capacitor functions into one shared component, thereby reducing the total physical area required
3Power
If high power is supplied to drive transducers, then the driving capability is improved, but the power consumption increases
Solution Approach 1:
The charge pump circuit employs dynamic switching control to adapt its power consumption to the actual driving requirements. The controller sequences the switching paths based on the selected output voltage ratio and load conditions, enabling the circuit to operate efficiently across different power levels. This dynamic operation allows the system to supply high power when needed (e.g., to drive transducers like backlights or piezoelectric transducers) while consuming less power during normal operation, optimizing the trade-off between driving capability and power consumption
Data Source
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Figure 3a~3b
AI summary
A bipolar output charge pump circuit 100 is provided having a network of switching paths 110 for selectively connecting an input node (VV) and a reference node (VG) for connection to an input voltage, a first pair of output nodes (VP, VN), two pairs of flying capacitor nodes (CF1A, CF1B; CF2A, CF2B), and a controller for controlling the switching of the network of switching paths. The controller is operable to control the network of switching paths when in use with two flying capacitors (CF1, CF2) connected to the two pairs of flying capacitor nodes, to provide a first mode and a second mode when in use with two flying capacitors connected to the flying capacitor nodes, wherein at least the first mode corresponds to a bipolar output voltage of +/-3VV, +/-VV/5 or +/-VV/6.