DC-to-DC Controller Undershoot Mitigation via Pulsed Switching
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Solution Overview
Problem
Conventional DC-to-DC buck converters experience undershoot and instability in output voltage due to continuous operation of the lower-bridge switch, leading to excessive negative current that can damage the output inductor.
Innovation Solution
A DC-to-DC controller with a time generation unit, VID change determining circuit, and time control circuit that controls the upper-bridge and lower-bridge switches by turning off the upper-bridge switch for a first preset time and turning on the lower-bridge switch multiple times for a second preset time and off for a third preset time, where the second time is greater than the third, to manage the inductor current and prevent undershoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the lower-bridge switch is continuously turned on to reduce output voltage, then the output voltage decreases, but excessive negative current is generated causing undershoot and instability
Solution Approach 1:
The patent applies periodic action by controlling the lower-bridge switch to operate in pulsed intervals rather than continuously. The controller turns on the lower-bridge switch for a first preset time period, then turns it off for a second preset time period, creating a periodic switching pattern. This periodic operation allows the inductor current to recover between pulses, preventing excessive negative current accumulation while still achieving the desired output voltage reduction, thereby eliminating undershoot and stabilizing the output.
2Power
If the lower-bridge switch is continuously turned on to reduce output voltage, then the output voltage decreases, but the negative current may burn out the output inductor
Solution Approach 1:
The patent applies periodic action by controlling the lower-bridge switch to operate in pulsed intervals rather than continuously. The controller turns on the lower-bridge switch for a first preset time period, then turns it off for a second preset time period, creating a periodic switching pattern. This periodic operation allows the inductor current to recover between pulses, preventing excessive negative current accumulation while still achieving the desired output voltage reduction, thereby eliminating undershoot and stabilizing the output.
Solution Approach 2:
The patent applies beforehand cushioning by implementing protective control measures before damage can occur. The controller detects when the output voltage reaches the reference voltage and proactively limits the lower-bridge switch conduction time to preset intervals. This preemptive timing control cushions against the development of excessive negative current that would otherwise burn out the output inductor, preventing damage before it happens rather than reacting after failure occurs.
Data Source
AI summary
A DC-to-DC controller, a DC-to-DC power converter and a control method thereof are provided. The controller is coupled to an upper-bridge switch and a lower-bridge switch and includes a time generation unit providing a time signal, a voltage identification (VID) change determining circuit and a time control circuit. The VID change determining circuit provides a determination signal in response to a VID signal. The time control circuit provides a control signal according to the time signal and the determination signal. When the VID signal changes from high to low, the time control circuit turns off the upper-bridge switch for a first preset time according to the determination signal and the time signal, and during the first preset time, the time control circuit controls the lower-bridge switch to be turned on for a second preset time multiple times, and to be turned off for a third preset time multiple times.