Configurable Feedback Loop for USB Charger Voltage Regulation
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Solution Overview
Problem
USB chargers compliant with USB Power Delivery require adjustable feedback loops to effectively regulate output voltage across a range of 5V to 20V, as existing feedback loops are inadequate for switching between these nominal voltages, leading to inefficient voltage regulation and longer settling times.
Innovation Solution
A power converter with a flyback topology and a configurable power controller that uses a selection signal to determine the nominal output voltage, employing a reference voltage generator, comparator, and low-pass filtering to adjust the switching frequency based on compensation and feedback signals, ensuring optimal regulation at both 5V and 20V.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed feedback loop is used for USB charger, then the circuit design is simple, but the voltage regulation is inefficient when switching between different nominal output voltages (5V to 20V)
Solution Approach 1:
The feedback loop transitions from a static fixed design to a dynamic configurable design. The system dynamically selects between different feedback loop configurations (first feedback loop for 5V, second feedback loop for 20V) based on the nominal output voltage requirement, enabling optimal regulation performance at each voltage level while maintaining manageable circuit complexity through systematic design.
Solution Approach 2:
The feedback loop parameters (resistor values, capacitor values, compensation network characteristics) are changed according to the operating voltage. The system configures different feedback loop parameters for different nominal output voltages, allowing the voltage regulation to be optimized for each specific voltage level (5V or 20V) rather than using a compromise fixed design.
2Device complexity
If a single feedback loop is used for both 5V and 20V regulation, then the device structure is simple, but the settling time is long when switching between voltage levels
Solution Approach 1:
The feedback loop is segmented into multiple independent configurations (first feedback loop for 5V, second feedback loop for 20V) rather than using a single unified loop. Each segmented feedback loop is optimized for its specific voltage range, allowing the system to switch between pre-optimized configurations and achieve fast settling times when transitioning between 5V and 20V operation.
Solution Approach 2:
The appropriate feedback loop configuration is preliminarily prepared and configured before voltage switching occurs. The system proactively switches to the correct feedback loop (first or second) in advance of or simultaneously with the voltage transition, eliminating the need for lengthy re-adjustment periods and reducing settling time during voltage level changes.
3Reliability
If the feedback loop is optimized for 20V regulation, then the high voltage performance is good, but the regulation performance degrades when operating at 5V
Solution Approach 1:
The power supply system achieves universal voltage regulation capability by implementing multiple feedback loop configurations that can be selectively activated. The first feedback loop provides optimized regulation for 5V operation, while the second feedback loop provides optimized regulation for 20V operation. This multi-functional approach allows the system to maintain high regulation performance across the entire voltage range rather than compromising for a single voltage level.
Solution Approach 2:
The feedback loop parameters are changed based on the operating voltage level. When operating at 5V, the system configures the first feedback loop with parameters optimized for low voltage regulation. When operating at 20V, the system configures the second feedback loop with parameters optimized for high voltage regulation. This parameter adaptation ensures reliable voltage regulation performance at each operating point.
Data Source
AI summary
A power controller is in use of a power converter whose output voltage can be regulated at a first nominal output voltage or a second nominal output voltage less than the first nominal output voltage. An ON-time controller controls an ON time of a driving signal provided to a power switch according to a compensation signal. A frequency controller controls, based on the compensation signal and a feedback signal, a switching frequency of the driving signal. If the compensation signal has an input waveform and when the output voltage is regulated at the first or second nominal output voltage, the frequency controller provides first or second settling time to stabilize the switching frequency, respectively. The second settling time is longer than the first settling time.