DC-DC Converter PWM Delay Reduction via Variable Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
DC-DC converters experience efficiency degradation due to propagation delay of PWM signals, leading to increased switching loss and ripple in load current, especially in low load states, causing pulse skipping and reduced efficiency.
Innovation Solution
A current mode DC-DC converter with a sense amplifier unit that varies the resistance value based on the load state to control the PWM signal delay, reducing the ON time of the internal power transistor and minimizing switching loss by adjusting the sensing current and resistance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the PWM signal propagation delay is reduced, then the switching loss is decreased and efficiency is improved, but the circuit complexity increases due to the need for variable resistance control
Solution Approach 1:
The patent applies dynamics by making the resistance value of the sensing load unit variable rather than fixed. The resistance is dynamically adjusted based on the load state through a load control signal, allowing the PWM signal delay to be optimized for different operating conditions. This dynamic adjustment reduces switching loss in low load states while maintaining stability across varying load conditions.
Solution Approach 2:
The patent changes the resistance parameter of the sensing load unit according to the load state. By varying the resistance value, the sensing current is adjusted, which directly controls the PWM signal delay. This parameter change enables the system to reduce PWM delay and switching loss in low load states while maintaining appropriate delay characteristics in high load states.
2Loss of energy
If the ON time of the internal power transistor is reduced to minimize switching loss, then the efficiency is improved, but the load current control precision may be affected
Solution Approach 1:
The patent uses feedback through the sense amplifier unit that senses the current flowing through the power switch unit. The sensed current is amplified and used to control the power switch unit, creating a closed-loop system. This feedback mechanism ensures that even with reduced ON time, the load current control precision is maintained by continuously monitoring and adjusting based on actual current conditions.
Solution Approach 2:
The patent applies preliminary action by adjusting the resistance value of the sensing load unit before the power switch unit operates. By pre-configuring the appropriate resistance based on the load state, the system prepares the optimal sensing current level in advance, ensuring that the PWM signal delay is minimized while maintaining control precision when the power switch unit is activated.
3Device complexity
If a fixed resistance value is used in the sensing load unit, then the circuit simplicity is maintained, but the PWM signal delay varies causing instability in low load states
Solution Approach 1:
The patent transforms the fixed resistance into a dynamic, variable resistance controlled by the load control signal. This dynamic adjustment allows the sensing load unit to adapt its resistance value according to the load state, ensuring stable operation in low load states by reducing PWM signal delay when needed, while maintaining circuit functionality across all operating conditions.
4Loss of energy
If the sensing current is increased to reduce PWM signal delay, then the switching loss is reduced, but the power consumption of the sense amplifier increases
Solution Approach 1:
The patent changes the sensing current parameter dynamically by adjusting the resistance value of the sensing load unit based on the load state. Instead of using a continuously high sensing current, the system uses higher sensing current only when needed (in low load states with high PWM delay), and reduces it when the load increases, thereby reducing switching loss while minimizing unnecessary power consumption in the sense amplifier.
Data Source
AI summary
A voltage regulator uses a comparing apparatus having hysteresis characteristics. The voltage regulator includes a comparator for comparing a comparison voltage with a reference voltage, and outputs a result of the comparison; a switching controller for generating a plurality of switching signals in response to the comparison result; resistors connected in the form of a string, to divide the comparison voltage into a plurality of voltages; and a switching box for selecting one of the plural voltages, as the comparison voltage, in response to the switching signals.