Inverting Buck-Boost Converter for Stable Auxiliary Voltage
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Solution Overview
Problem
Existing power converters with galvanic isolation face challenges in regulating the auxiliary voltage provided by an auxiliary winding of the transformer, which varies significantly with the output voltage, making it difficult to design a controller that can operate across this wide range of supply voltages.
Innovation Solution
The implementation of a buck-boost converter within the power converter, where the first input terminal is coupled to a first terminal of the auxiliary winding and the second input terminal is coupled to a second terminal of the auxiliary winding, allows for the regulation of the auxiliary voltage to a predefined value usable by the controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an auxiliary winding is used to provide power to the controller, then the controller can be supplied with power, but the auxiliary voltage varies significantly with the output voltage range
Solution Approach 1:
A dedicated voltage regulation circuit is introduced as an intermediary between the auxiliary winding and the controller. This circuit actively regulates the varying auxiliary voltage to a stable level, decoupling the controller's power supply from the output voltage variations. The regulation circuit acts as a mediator that transforms the problematic variable voltage into a reliable fixed voltage for the controller.
Solution Approach 2:
The voltage regulation circuit dynamically adjusts its operating parameters (such as duty cycle in PWM regulation or reference voltage levels) to maintain a constant output voltage despite variations in the auxiliary winding voltage. By changing these parameters in response to input voltage changes, the circuit maintains stable controller power supply across the full output voltage range.
2Reliability
If conventional solutions like depletion MOSFET with Zener diode are used to clamp the maximum voltage, then the voltage can be regulated, but the area requirement and bill of materials increase
Solution Approach 1:
The voltage regulation circuit is designed to perform multiple functions: it regulates the auxiliary voltage, provides soft-start capability, and can implement over-voltage protection. By consolidating these functions into a single integrated circuit or minimal component set, the solution avoids the need for separate depletion MOSFETs, Zener diodes, and associated components, thereby reducing overall circuit area and BOM while maintaining comprehensive voltage regulation capability.
3Reliability
If conventional solutions like divided auxiliary windings are used, then the voltage can be regulated, but the power efficiency deteriorates
Solution Approach 1:
The voltage regulation circuit incorporates feedback from the auxiliary winding voltage to dynamically adjust its operation. By continuously monitoring the input voltage and adjusting the duty cycle or conduction time accordingly, the circuit minimizes energy losses through optimized switching operation. This feedback mechanism ensures high efficiency across the full range of auxiliary voltage conditions, unlike fixed divided winding approaches that waste energy through resistive drops.
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 solution effectively stabilizes the auxiliary voltage, enabling the controller to operate reliably across a wide range of output voltages, from 5V to 48V, thereby addressing the challenges of variable auxiliary voltage in power converters.
Implementation Method 1
an inductor, a capacitor, a first diode and a second diode... an anode of the second diode is coupled to the first terminal of the inductor
Implementation Method 2
a first terminal of the capacitor is coupled to the first output terminal and a cathode of the second diode, an anode of the second diode is coupled to the first terminal of the inductor and a second terminal of the capacitor is coupled to the second output terminal and the second terminal of the inductor
Implementation Method 3
a first diode and a second diode... a cathode of the second diode... an anode of the second diode is coupled to the first terminal of the inductor
Data Source
Figure 1A~1B
Figure 2
Figure 3A~4
AI summary
Buck-boost converters and corresponding power converters are disclosed. The buck-boost converter includes a transistor (11) having a terminal, e.g. source terminal, coupled to an output terminal (17B) and a terminal of a capacitor (15).