Switching Mode Power Supply Dynamic High-Voltage Charging
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Solution Overview
Problem
Conventional USB chargers using isolation topology face challenges in maintaining the operating voltage within a safe range for the power controller, especially when the output voltage varies between 5V and 20V, as the induced voltage across the auxiliary winding may not be sufficient to power the controller effectively, leading to potential damage or inadequate operation.
Innovation Solution
The USB charger configuration eliminates the need for a low drop out (LDO) regulator, instead using high-voltage charging to maintain the operating voltage within a safe range of 10V to 30V by adjusting the induced voltage of the auxiliary winding based on the output voltage, ensuring the power controller operates normally regardless of the voltage rating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output voltage is set to 20V to induce sufficient operating voltage for the power controller, then the power controller can operate normally, but when the output voltage is reduced to 5V, the operating voltage becomes too low to power the controller
Solution Approach 1:
The auxiliary winding is designed to induce a voltage higher than normally required (e.g., 40V when output is 20V) so that when the output voltage is reduced to 5V, the induced voltage (10V) remains sufficient to power the controller. This preliminary over-design of the auxiliary winding compensates for future voltage reductions.
Solution Approach 2:
The turns ratio of the auxiliary winding is specifically optimized to change the induced voltage proportionally with output voltage changes. By designing the auxiliary winding with appropriate turns ratio, the induced voltage maintains adequate levels across the full output voltage range from 5V to 20V, ensuring continuous controller operation.
2Reliability
If an LDO regulator is used to clamp the operating voltage to protect the power controller, then the controller is protected from over-voltage damage, but the manufacturing cost increases and the LDO consumes power
Solution Approach 1:
The LDO regulator component is completely removed from the circuit. Instead of using an LDO to clamp and regulate the operating voltage, the design relies on the naturally induced voltage from the auxiliary winding being within the acceptable range, thereby eliminating the need for additional voltage regulation hardware and reducing manufacturing cost.
Solution Approach 2:
The auxiliary winding automatically provides the appropriate operating voltage to the power controller through electromagnetic induction, without requiring external regulation. The system self-regulates by design, where the induced voltage inherently stays within the controller's operating range across different output voltage conditions.
3Device complexity
If the auxiliary winding induces voltage proportional to output voltage, then the system is simple and efficient, but when output voltage drops to 5V, the induced voltage becomes insufficient to drive the power switch
Solution Approach 1:
The turns ratio of the auxiliary winding is specifically optimized to ensure that even at minimum output voltage (5V), the induced voltage remains above the threshold required to drive the power switch (greater than 10V). This parameter optimization allows the simple proportional induction system to meet minimum power requirements without adding complexity.
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 allows for a lower manufacturing cost and effective operation of the USB charger across different voltage ratings, ensuring the power controller is protected from over-voltage stress while maintaining adequate power supply, regardless of the output voltage being 5V or 20V.
Implementation Method 1
the induced voltage across an auxiliary winding of a transformer
Implementation Method 2
An alternating-current voltage from a power grid is rectified by a bridge rectifier to generate an input voltage
Data Source
AI summary
A power controller in a switching mode power supply dynamically performs high-voltage charging to maintain an operating voltage. The power controller includes a PWM signal generator, a high-voltage charging circuit, and a high-voltage charging controller. The PWM signal generator provides a PWM signal to a power switch to perform power conversion regulating an output voltage of the switching mode power supply at a voltage rating. The high-voltage charging circuit has a high-voltage-tolerant switch connected between a line voltage and the operating voltage, wherein rectifying an AC voltage generates the line voltage. The high-voltage charging controller turns ON the high-voltage-tolerant switch to perform high-voltage charging at the same time when performing the power conversion. The high-voltage charging directs a charging current from the line voltage through the high-voltage-tolerant switch to charge the operating voltage.