Switched Mode Power Supply Controller Voltage Boosting Circuit
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Solution Overview
Problem
In low output voltage applications of switched-mode power supplies, existing solutions like pulse linear regulators and auxiliary transformer windings lead to significant power loss and inefficiency due to the need for additional components and space, especially when the DC output voltage is lower than the operating supply voltage of the controller.
Innovation Solution
A switched-mode power supply design that includes a circuit with a capacitor, buffer, and diodes coupled between the gate or drain terminal of the synchronous rectifier and the supply voltage terminal of the controller, using the control signal voltage to boost the DC output voltage and reduce the reliance on pulse linear regulators, thereby minimizing power loss and component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pulse linear regulator is used to supply voltage to the controller when output voltage is low, then the controller can operate, but power loss increases significantly
Solution Approach 1:
The patent introduces a voltage boosting circuit as an intermediary between the low output voltage and the controller's supply voltage terminal. This circuit uses a capacitor charged to the output voltage and a buffer (with switches and diodes) to generate a boosted voltage that exceeds the output voltage, thereby eliminating the need for a pulse linear regulator and reducing power loss.
2Reliability
If an auxiliary winding is added to the transformer to supply controller voltage, then the controller can operate during low voltage conditions, but device complexity and component count increase
Solution Approach 1:
The patent makes the existing output capacitor serve multiple functions: it continues to provide output voltage filtering while also being used to store energy for the voltage boosting circuit. By charging this existing capacitor to the output voltage and using it in the boosting circuit, the patent eliminates the need for an auxiliary transformer winding and reduces component count.
3Reliability
If additional components are added to supply controller voltage during low output voltage, then controller operation is ensured, but PCB space requirements increase
Solution Approach 1:
The patent merges the voltage boosting function with the existing output filtering capacitor and uses existing controller terminals (gate or drain) as part of the boosting circuit. This integration approach minimizes additional components and reduces PCB space requirements compared to using separate auxiliary windings or dedicated voltage supply circuits.
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 enhances efficiency by reducing power loss and minimizing the need for additional components, achieving an efficiency improvement of approximately 1% from 81.8% to 82.8% in certain scenarios, while maintaining cost-effectiveness and reducing PCB space requirements.
Implementation Method 1
The circuit comprises a first capacitor and a buffer coupled between a first terminal of the first capacitor, the output, and the gate terminal of the controller
Implementation Method 2
The buffer comprises at least two buffer switches
Data Source
AI summary
A switched-mode power supply includes an input, an output, and a transformer including primary and secondary windings. The power supply also includes a synchronous rectifier coupled to selectively conduct current through the secondary winding of the transformer. The synchronous rectifier includes a source, a gate and a drain terminal. The power supply further includes a controller having a supply voltage terminal and a gate terminal to supply a control signal to the gate of the synchronous rectifier, and a circuit coupled between the supply voltage terminal of the controller and at least one of the gate terminal of the controller and the drain terminal of the synchronous rectifier to supply power from the gate terminal of the controller or the drain terminal of the synchronous rectifier to the supply voltage terminal of the controller. Methods of supplying power in switched-mode power supplies are also disclosed.