PWM Controller Short Circuit Protection via Voltage Drop Timing
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Solution Overview
Problem
Existing PWM controller short circuit protection mechanisms fail to effectively prevent damage from overcurrent and do not maintain stable voltage levels due to repeated transistor on/off states and lack of initiation during the PWM controller's startup phase.
Innovation Solution
A PWM controller design incorporating a voltage-sensing module and a timer that detects voltage drops at a first terminal, initiating a short circuit signal when the duration exceeds a predetermined value, thereby isolating system power and preventing damage by temporarily turning off the PWM controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a short circuit protection module detects feedback pin voltage drop and turns off power transistor, then output voltage short circuit is prevented, but devices in relevant paths and PWM controller are still damaged by overlarge current
Solution Approach 1:
The patent introduces a timer that measures the duration of voltage drop at the feedback pin before triggering the short circuit protection. This preliminary timing action allows the system to distinguish between temporary voltage fluctuations and actual short circuit conditions, enabling more precise protection activation that prevents overcurrent damage while maintaining reliability.
2Reliability
If a P-type MOSFET transistor is used to prevent system power from being affected by output voltage, then power isolation is improved, but repeated on/off states cause voltage to follow triangular waveform instead of remaining stable
Solution Approach 1:
The timer circuit performs preliminary measurement of the voltage drop duration before triggering the MOSFET to turn off. This preliminary action prevents premature or repeated switching operations, allowing the MOSFET to remain in a stable state and maintain steady voltage levels rather than creating triangular waveform oscillations.
3Device complexity
If short circuit protection mechanism is not initiated upon initiation stage of PWM controller, then startup process is simplified, but full protection is not provided to the circuit
Solution Approach 1:
The timer circuit is designed to operate from the initiation stage of the PWM controller, performing preliminary monitoring of the feedback pin voltage throughout the entire operation including startup. This ensures comprehensive protection coverage is provided from the very beginning without adding significant complexity to the startup process.
Data Source
AI summary
A PWM comprises a voltage transformation module, a voltage-sensing module and a timer. The voltage transformation module is configured to transform an input voltage into an output voltage. The voltage-sensing module is coupled to the voltage transformation module and configured to detect a voltage of a first terminal, wherein the voltage of the first terminal is proportional to the output voltage. The timer is configured to measure the time duration for which the voltage of the first terminal is lower than a reference voltage, wherein the timer initiates a short circuit signal when the time duration is greater than a predetermined value.