Non-insulating Switching Power Supply with Zero-Volt Control
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Solution Overview
Problem
Conventional switching power supply devices face challenges in suppressing switching loss and electromagnetic noise, particularly at high switching frequencies, which leads to increased loss and noise interference.
Innovation Solution
A non-insulating switching power supply device with synchronized rectification, utilizing an inductor, a first switch, and a second switch controlled by respective control circuits, where the first switch increases and the second switch decreases the inductor current, with control circuits managing the switches to minimize voltage across them and optimize ON-periods to achieve zero-volt switching, thereby reducing switching loss and electromagnetic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching frequency is increased to improve productivity, then switching loss and electromagnetic noise increase
Solution Approach 1:
The control circuit performs preliminary action by detecting the voltage across the first switch before turning it off. When the voltage drops to a predetermined level, the control circuit turns off the first switch in advance, ensuring that the switch operates at near-zero voltage. This preliminary detection and timing mechanism prevents high-voltage switching events that would generate excessive switching loss and electromagnetic noise, thereby resolving the contradiction between maintaining high switching frequency for productivity and minimizing switching loss.
2Productivity
If switching frequency is increased to improve productivity, then electromagnetic noise increases
Solution Approach 1:
The control circuit detects the voltage across the first switch in advance and turns off the switch when the voltage reaches a predetermined low level. This preliminary timing ensures that switching occurs at minimal voltage, significantly reducing electromagnetic noise generation. By maintaining this zero-volt switching condition even at high switching frequencies, the invention enables high productivity while suppressing electromagnetic noise to acceptable levels.
3Device complexity
If conventional switching control is used, then circuit complexity is reduced, but switching loss and electromagnetic noise increase
Solution Approach 1:
The control circuit incorporates feedback by continuously monitoring the voltage across the first switch and using this information to determine the optimal timing for turning off the switch. This feedback mechanism enables the system to adaptively adjust switching timing to maintain zero-volt switching conditions, thereby reducing switching loss and electromagnetic noise. The feedback-based approach achieves superior performance compared to conventional fixed-timing control, justifying the moderate increase in circuit complexity.
Data Source
AI summary
A switching power supply device includes a first control circuit that turns a first switch on when first and second switches are off and a voltage at a junction node therebetween is increased to decrease a voltage across the first switch to a first threshold voltage, turns off when a first ON-period has elapsed from when the first switch is turned on, and lengthens the first ON-period as an output voltage decreases relative to a reference voltage; and a second control circuit that turns the second switch on when both switches are off and a voltage across the second switch is decreased to a second threshold voltage, turns off when a reverse current flows through the inductor, sufficient to increase the voltage at the junction node to decrease the voltage across the first switch to the first threshold voltage after the second switch is turned off.