Transient Response Circuit With Parallel Diode And Transistor
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Solution Overview
Problem
Switching power supplies have inherently slow transient responses due to large energy storage elements, which limits their ability to quickly respond to increased current demands, and existing solutions to improve this often result in unstable control loops.
Innovation Solution
A transient response circuit is connected in series with the output stage of the power supply, comprising a diode and a source follower transistor that selectively bypasses the diode's voltage drop during transient periods, allowing the power supply to quickly increase output voltage by removing the diode's forward voltage drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a switching power supply uses a relatively large output capacitor to keep output ripple low, then efficiency is improved and temperature rise is reduced, but transient response becomes slow when responding to increased current demand
Solution Approach 1:
The invention segments the voltage regulation function into two parts: the main power supply circuit handles steady-state regulation using PWM control, while the transient response circuit handles dynamic voltage adjustments during transient periods. This segmentation allows each circuit to be optimized for its specific function without compromising the other.
Solution Approach 2:
The transient response circuit is pre-configured with a capacitor charged to a higher voltage level and a diode positioned to automatically conduct during transient periods. When a sudden current demand occurs, the circuit immediately responds by conducting current through the diode without waiting for feedback control, thus providing preliminary action that speeds up transient response.
2Speed
If the value of compensation capacitor of the error amplifier is reduced to reduce transient amplitude, then transient response is improved, but the control loop becomes unstable or oscillatory
Solution Approach 1:
The invention introduces a transient response circuit as an intermediary between the main power supply output and the load. This intermediate circuit handles the transient voltage adjustments, allowing the main feedback control loop to remain stable with its original compensation capacitor values while still achieving fast transient response through the intermediary circuit's immediate action.
3Speed
If a linear power supply uses a series control element operating in linear mode to maintain constant output voltage, then transient response is very quick, but efficiency is low and large amount of heat is generated
Solution Approach 1:
The invention makes the diode's voltage drop dynamic rather than fixed. During transient periods, the diode conducts and provides a fixed voltage drop that enables fast response. During steady-state operation, the PWM control adjusts the duty cycle to compensate for the diode's voltage drop, maintaining efficient operation. This dynamic operation allows the system to switch between fast response mode and efficient mode as needed.
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 configuration enhances the transient response of switching power supplies to match the speed of linear power supplies, improving the power supply's ability to handle current transients while maintaining high efficiency and low heat generation.
Implementation Method 1
a diode connected in series with an output of the power supply and configured to provide a predetermined voltage drop to an output voltage of the power supply
Implementation Method 2
a source follower transistor connected in parallel with the diode and configured to be selectively activated to remove at least a portion of the predetermined voltage drop of the diode from the output voltage of the power supply during a transient period
Data Source
AI summary
A device for improving transient response of a power supply includes a diode connected in series with an output of the power supply and configured to provide a predetermined voltage drop to an output voltage of the power supply. The device further includes a source follower transistor connected in parallel with the diode and configured to be selectively activated to remove at least a portion of the predetermined voltage drop of the diode from the output voltage of the power supply during a transient period, in which an output current of the device is increasing.