LDO Power Supply Isolation for USB-PD Overvoltage Protection
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Solution Overview
Problem
Existing USB-C cables and connectors using USB-PD technology face issues with voltage regulation, where the power supply level negotiation can result in voltage exceeding target values, potentially damaging connected devices due to lack of effective isolation and protection mechanisms.
Innovation Solution
A device with a low-dropout linear voltage regulator and control circuit, including a hysteresis comparator and differential amplifier, is used to compare input and output voltages, controlling a switch to maintain the output voltage within a threshold, preventing damage by isolating the connector when voltages exceed safe levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If voltage negotiation is performed in USB-PD technology, then power supply adaptability is improved, but voltage may exceed target values causing device damage
Solution Approach 1:
A low-dropout linear voltage regulator is introduced as an intermediary component between the power supply source and the load. The regulator receives a first DC voltage from the power source and provides a regulated second DC voltage to the control circuit and load, ensuring that even when negotiated voltage exceeds target values, the actual voltage delivered remains within safe thresholds.
Solution Approach 2:
The control circuit continuously monitors the output voltage and uses feedback to adjust the switch control signals. The hysteresis comparator compares the output voltage with reference values and adjusts the switch duty cycle accordingly, maintaining voltage within acceptable ranges despite variations in input voltage or load conditions.
2Reliability
If switch control is added for voltage regulation, then voltage protection is improved, but device complexity increases
Solution Approach 1:
The control circuit integrates multiple functions into a unified design: the hysteresis comparator, voltage regulation control, and switch control are combined in a single control module. This merging reduces the number of discrete components and simplifies the overall circuit architecture while maintaining comprehensive voltage protection.
Solution Approach 2:
The control circuit automatically detects voltage conditions and adjusts switch operation without external intervention. The hysteresis comparator self-regulates by comparing output voltage against reference values and autonomously controlling the switch to maintain voltage within safe thresholds, eliminating the need for complex external control mechanisms.
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
Effectively regulates and limits the output voltage to prevent damage to electronic devices by ensuring it remains within safe thresholds, even when the input voltage exceeds negotiated levels, thus protecting the device from overvoltage conditions.
Implementation Method 1
a low-dropout (LDO) linear voltage regulator connected between the first and third terminals, the regulator being configured to provide the second voltage based on the first voltage
Implementation Method 2
the control circuit of the switch comprises a hysteresis comparator, a first input of which is coupled to the first terminal, a second input of which is connected to the third terminal
Implementation Method 3
a second circuit configured to provide, to the fourth terminal, a signal representative of the difference between the value of the second voltage and the threshold value. The second circuit comprises a differential amplifier
Data Source
AI summary
A first terminal receives a first DC voltage. A switch selectively couples the first terminal to a second terminal providing an output. A control circuit selectively actuates the switch in response to a comparison of the first DC voltage to a second DC voltage. A low-dropout (LDO) linear voltage regulator, connected between the first and third terminals, operates to provide the second DC voltage from the first DC voltage.