Boost Converter Current Limiting Across CCM and PFM Modes
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Solution Overview
Problem
Existing DC-to-DC converters, particularly boost converters, operate within a narrow current limiting range and struggle to efficiently handle low current levels, requiring larger inductors and additional hardware, which increases inefficiency and cost.
Innovation Solution
The implementation of a DC-to-DC boost converter with a switch, diode, clamp circuit, and minimum time off module that controls the inductor output current to achieve a wide current limiting range from 5 mA to 1.5 A by clamping the inductor current to a reference current in continuous conduction mode and maintaining zero current for a minimum time in pulse frequency modulation mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing DC-to-DC converters operate with narrow current limiting range, then the converter can be simpler in design, but the converter cannot efficiently handle low current levels and requires larger inductors
Solution Approach 1:
The converter dynamically switches between CCM and PFM operating modes based on the current level. The control circuit automatically selects CCM for higher currents and PFM for lower currents, enabling the converter to adapt to a wide current range (5 mA to 1.5 A) without requiring complex external components
Solution Approach 2:
The converter changes its operating parameters by switching between two distinct modes: CCM for higher current operation and PFM for lower current operation. This parameter change allows the same converter circuit to efficiently handle currents from 5 mA to 1.5 A, eliminating the need for larger inductors that would be required in a single-mode design
2Adaptability or versatility
If larger inductors are used to handle low current levels, then the converter can operate at low currents, but the converter efficiency decreases and cost increases
Solution Approach 1:
The converter uses dynamic mode switching to operate in PFM at low currents, which maintains efficiency by minimizing unnecessary switching activity and reducing the current through the inductor. This dynamic adaptation eliminates the need for larger inductors that would increase resistive losses and improve efficiency across the full current range
Solution Approach 2:
In PFM mode, the converter uses periodic switching with variable duty cycles to maintain efficient operation at low currents. The periodic action allows the converter to deliver precise low current levels (as low as 5 mA) while minimizing energy losses through optimized switching timing and reduced inductor current stress
3Adaptability or versatility
If additional hardware is added to expand current range, then the converter can handle wider current levels, but the converter cost and complexity increase
Solution Approach 1:
The control circuit is designed to perform multiple functions: it regulates output voltage, monitors inductor current, determines operating mode (CCM or PFM), and controls the switching duty cycle. This universal control architecture enables wide current range operation (5 mA to 1.5 A) without requiring additional dedicated hardware components for each function
Solution Approach 2:
The patent merges voltage regulation and current limiting functions into a single control circuit that operates in two modes. The same control hardware that regulates voltage also performs current limiting by switching between CCM and PFM modes, eliminating the need for separate current limiting circuitry and reducing overall device complexity
Data Source
AI summary
A boost converter that provides a wide average current limiting range includes a switch coupled to an inductor output and a power input, a diode coupled to the inductor output and an output terminal load and configured to conduct current in only one direction away from the inductor output and toward the output terminal, a clamp circuit coupled to the diode and the switch, and a minimum time off module coupled to the diode and the switch. The clamp circuit is configured to clamp an inductor output current to a reference current while the converter is operating in a continuous conduction mode (CCM) of operation. The minimum time off module is configured to cause the inductor output current to be zero for at least a time Toff while the converter is operating in a pulse frequency modulation (PFM) mode of operation.