DC-DC Converter Pulse Width Regulation for Voltage Stability
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Solution Overview
Problem
The switching from PFM control to PWM control in DC-DC converters can result in a significant decrease in output voltage due to insufficient charge supply to the smoothing condenser, leading to voltage fluctuations when the load is light.
Innovation Solution
Incorporating a clamp circuit in the switching control circuit to regulate the PWM control pulse width and clamp the output of the error amplifier, ensuring the pulse width is not smaller than a predetermined value during the switch from PFM to PWM control, thereby preventing excessive voltage drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If PFM control is used when the load is light, then power consumption is reduced, but the output voltage fluctuates greatly and may decrease significantly when switching to PWM control
Solution Approach 1:
The patent applies preliminary action by pre-regulating the pulse width of the PWM control pulse using a pulse width regulation section before the switching from PFM to PWM control occurs. This ensures that when the transition happens, the PWM pulse already has an appropriate width to prevent output voltage drop, rather than waiting for the voltage to actually drop and then correcting it.
Solution Approach 2:
The pulse width regulation section acts as an intermediary between the PWM comparator and the drive switching element. It receives the PWM control pulse, regulates its width to be within a predetermined range, and then outputs the regulated pulse. This intermediary component ensures smooth transition and prevents direct coupling of the switching action to the output voltage.
2Device complexity
If the PWM control pulse width is determined by the error amplifier output during PFM to PWM switching, then the switching is simple, but the pulse width may be too small causing insufficient charge supply to the smoothing condenser
Solution Approach 1:
The pulse width regulation section performs preliminary regulation on the PWM control pulse width before it reaches the drive switching element. By pre-adjusting the pulse width to be within a predetermined range, the system ensures sufficient charge supply to the smoothing condenser during switching without requiring complex real-time adjustment mechanisms.
Solution Approach 2:
The pulse width regulation section uses feedback from the error amplifier output and switching state to dynamically adjust the PWM control pulse width. The regulation section monitors the pulse width and adjusts it to maintain it within the predetermined range, ensuring both precision and adaptability during the transition from PFM to PWM control.
Data Source
AI summary
Provided is a DC-DC converter comprising: a drive switching element so that a current flows to an inductor, the drive switching element being driven by a PWM control pulse or a PFM control pulse, wherein a direct-current input voltage supplied from a direct-current power source is converted so as to output the converted direct-current voltage having a different potential, and wherein a PWM control is performed when a load is larger than a predetermined value and a PFM control is performed when the load is smaller than the predetermined value, the DC-DC converter further comprising: a pulse width regulation section to regulate the PWM control pulse so as not to have a pulse width smaller than a predetermined pulse width, at least when the PFM control is switched to the PWM control.