Switching Power Supply Control Circuit for Wide ON-Period Ratio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional switching power supply control circuits face limitations in controlling the ON-period ratio due to response delays in PWM comparators, which restrict the ability to increase switching frequency, especially at high frequencies, leading to a narrow range of controllable ON-period ratios.
Innovation Solution
A control circuit that includes an error amplifier circuit, a pulse generator circuit, and an ON-period adjusting circuit, which starts generating the PWM signal in every cycle and adjusts the ON-period based on the error signal, allowing for a wider range of ON-period ratios to be controlled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional PWM comparator is used for controlling switching power supply, then the control circuit can operate at lower switching frequencies, but the range of controllable ON-period ratios becomes narrow due to response delays
Solution Approach 1:
The patent extracts the problematic PWM comparator from the control circuit and replaces it with a pulse generator circuit that produces a triangular wave signal. This removal eliminates the response delay issue while maintaining the necessary comparison functionality through alternative means (comparing error signal with triangular wave), thereby widening the controllable ON-period ratio range.
2Productivity
If switching frequency is increased to improve power supply efficiency, then the response delay of PWM comparator becomes more significant, further restricting the controllable ON-period ratio range
Solution Approach 1:
The patent substitutes the conventional PWM comparator mechanism with a pulse generator-based approach. Instead of using a comparator that suffers from response delays at high frequencies, the system uses a pulse generator to create a triangular wave that is compared with the error signal, enabling high-frequency operation without the same timing constraints.
3Speed
If PWM comparator response time is reduced to enable higher switching frequencies, then the circuit complexity and precision requirements increase
Solution Approach 1:
The patent inverts the conventional approach by not trying to speed up the PWM comparator, but rather by generating a triangular wave signal that inherently accommodates the timing requirements. This inversion of the problem-solving approach allows high-frequency operation without requiring ultra-fast comparators or complex timing circuits.
Data Source
AI summary
Control circuit and method for controlling a switching power supply, which regulates its output voltage using pulse-width modulation (PWM) that switches on and off a main switch with a PWM signal (VCONT) at an adjusted ON-period ratio of the main switch. The control circuit includes an error signal amplifier circuit that compares the output voltage with a reference voltage and outputs an error signal VE based on the comparison. The control circuit also includes an ON-period adjusting circuit that starts generating a PWM signal (VCONT) in every cycle based on a pulse VPULSE, the period thereof being fixed, and adjusts the HIGH-period of the PWM signal (VCONT) based on the output voltage of the error signal VE. As a result, the control circuit widens the HIGH-period ratio range or the LOW-period ratio range of the PWM signal greatly.