Flyback Power Converter Voltage Regulation
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Solution Overview
Problem
Conventional switched-mode power supplies face challenges in providing stable output voltage under light-loading or low-voltage conditions, often resulting in unstable PWM control signals and mechanical noise due to reduced switching frequencies.
Innovation Solution
The proposed solution incorporates a flyback power converter with a transformer, active snubber circuit, and time-shared-energy-transfer method, utilizing a primary-side and secondary-side PWM controller to maintain a stable switching frequency and control output voltage between a minimal and preset voltage range, avoiding skip-cycles and mechanical noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the duty cycle is reduced to provide low output voltage, then the output voltage level is reduced, but the PWM control signal becomes weaker and approaches system noises making stabilization difficult
Solution Approach 1:
The patent introduces a secondary-side switch as an intermediary component between the transformer and the output load. This switch amplifies the PWM control signal effect by directly controlling the output voltage through a separate control loop, allowing the primary-side PWM controller to operate at higher frequencies without signal degradation. The secondary-side switch acts as a mediator that enhances the control signal strength and stability while enabling precise low-voltage regulation.
2Power
If the switching frequency is reduced to control low voltage output, then the output voltage is reduced, but the power supply produces mechanical noise below sonic frequency
Solution Approach 1:
The patent segments the power conversion function into two independent parts: the primary-side PWM controller handles high-frequency switching for voltage regulation, while the secondary-side switch handles low-voltage control separately. This segmentation allows the primary switching frequency to remain above the audible range (above 20 kHz) to avoid mechanical noise, while the secondary-side controller manages the actual output voltage level through phase-compensated control, effectively separating the noise-generating function from the voltage regulation function.
3Power
If the duty cycle is reduced below minimal activating time, then the output voltage control becomes difficult, but the PWM control signal period becomes too short
Solution Approach 1:
The patent adds another dimension to the control system by introducing a secondary-side control loop that operates independently from the primary-side PWM timing constraints. This additional control dimension allows voltage regulation to be achieved through phase compensation and secondary switching timing rather than being limited by the primary PWM duty cycle minimums. The secondary controller can extend the effective control period by using phase-compensated timing, effectively adding a temporal dimension to the control strategy.
4Speed
If burst-mode method is used for light-loading status, then the switching frequency is maintained, but energy-storing elements still produce mechanical noise due to envelope curve frequency
Solution Approach 1:
The patent implements a feedback mechanism through the secondary-side phase-compensation circuit that continuously monitors the output voltage and adjusts the secondary-side switch timing accordingly. This feedback loop allows the system to maintain continuous switching operation at a constant high frequency (above audible range) even under light-loading conditions, eliminating the need for burst-mode operation. The phase-compensated feedback ensures stable voltage regulation while keeping the switching frequency consistently above the mechanical noise threshold.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for linear control of output voltage across a wide range, maintaining stable frequency and preventing output voltage instability, even at low loads, thus ensuring consistent power delivery without mechanical noise.
Implementation Method 1
The transformer has a primary side and a secondary side. The primary side has an excitation winding and a vice-output winding
Implementation Method 2
The active snubber circuit has a first diode, a second diode, a third diode, a snubber capacitor, an energy-storing inductor and a snubber switch
Implementation Method 3
The second diode, the energy-storing inductor and the third diode are sequentially connected in series and connected to the input power
Data Source
AI summary
The present invention is a switched-mode power supply for providing a stable output voltage. An excitation winding, a vice-output winding and an active snubber circuit are connected to a primary side of a flyback-based transformer. A main-output winding is connected to a secondary side of the transformer. A primary-side PWM controller and a secondary-side PWM controller are respectively connected to the primary side and the secondary side of the transformer. By a time-shared-energy-transfer method, the main-output winding and the vice-output winding are controlled to sequentially extract demand electricity from the transformer during a same switching cycle. Additionally, by a time-shared-energy transformation, the output voltage on the secondary side of the transformer is stabilized to be provided between a stable minimal voltage and a preset higher voltage for satisfying a heavy-loading status and a light-loading status.