Switched Mode Voltage Regulator Startup Overshoot Control
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Solution Overview
Problem
Switched mode voltage regulators often experience fast ramp rates and overshoot during power-up, leading to issues like electrostatic discharge and overvoltage conditions, which can cause reliability problems.
Innovation Solution
A switched mode voltage regulator with a compensator that adjusts its RC time constant during start-up to slow down the ramp rate, using a filter with increased resistance to control the PWM duty cycle and prevent overshoot, and includes a voltage clamp to ensure the output does not exceed a certain level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the voltage regulator uses a standard RC time constant during start-up, then the circuit responds quickly, but the ramp rate becomes too fast causing ESD protection triggering and reset
Solution Approach 1:
The patent applies dynamics by making the RC time constant adjustable rather than fixed. During start-up, a first (larger) RC time constant is used to slow the ramp rate and prevent ESD triggering. After start-up completes, a second (smaller) RC time constant is used for normal operation. This dynamic adjustment resolves the contradiction between fast response and reliable power-up.
Solution Approach 2:
The patent changes the parameter values of the RC time constant based on operational phase. By switching between different resistance values (R1 during start-up, R2 during normal operation) while maintaining the same capacitor, the system achieves different time constants to satisfy different operational requirements - slow ramp during start-up for reliability, faster response during normal operation for performance.
2Productivity
If the voltage regulator allows fast ramp-up, then power delivery is efficient, but overshoot occurs causing overvoltage conditions and reliability problems
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor through a higher resistance value during the start-up phase before normal operation begins. This preliminary slow ramp-up prevents overshoot from occurring in the first place, eliminating the need for corrective actions and ensuring reliable power delivery without overvoltage conditions.
Solution Approach 2:
The dynamic switching between different RC time constants allows the system to optimize for different phases: a larger time constant during start-up to prevent overshoot and ensure reliability, then switching to a smaller time constant during normal operation to improve power delivery efficiency and productivity.
3Reliability
If the RC time constant is increased during start-up, then the ramp rate is reduced for stable power-up, but the response time during normal operation becomes slower
Solution Approach 1:
The patent resolves this contradiction through dynamic parameter adjustment - using a first RC time constant (with higher resistance) during start-up to ensure stability and prevent ESD triggering, then switching to a second RC time constant (with lower resistance) during normal operation to achieve faster response time. The system adapts its time constant based on operational phase requirements.
Solution Approach 2:
The system employs periodic action by switching between different operational modes with different RC time constants. The start-up mode with slower response is applied only during the initial power-up period, then transitions to the normal operation mode with faster response, allowing the system to optimize for reliability when needed and performance when stable.
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 effectively reduces the risk of fast ramp rates and overshoot, ensuring stable power-up and long-term reliability by allowing a slower ramp-up of the output voltage and preventing overvoltage conditions.
Implementation Method 1
the filter circuit has a first resistor-capacitor (RC) time constant during startup of the voltage regulator, and the filter circuit has a second RC time constant during normal operation
Data Source
AI summary
A voltage regulator includes a transistor, a comparator, and a compensation circuit. The comparator has a first input terminal coupled to receive a clock signal, a second input terminal, and an output terminal coupled to a control electrode of the transistor. The compensation circuit has a first input terminal coupled to receive a reference voltage, a second input terminal coupled to the output terminal of the voltage regulator, and an output terminal coupled to the second input terminal of the comparator. The compensation circuit has a filter circuit. The filter circuit has a first RC time constant during startup of the voltage regulator, and the filter circuit has a second RC time constant during normal operation. Changing the RC time constant for startup prevents an overshoot of an output voltage of the voltage regulator.