Switched Mode Power Supply Clamp Circuit for Voltage Overshoot
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In switched-mode power supplies, particularly boost converters, current limiting can lead to control voltage drift and significant overshoot in output voltage during load changes, causing prolonged recovery times and increased voltage margins when current limiting is active.
Innovation Solution
A clamp-circuit is introduced to regulate the control voltage, preventing it from exceeding a clamp-voltage-value when current limiting occurs, thereby maintaining the control voltage within a normal operating region and reducing overshoot by clamping it to the voltage level at which current limiting starts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current limiting is used to protect the power supply during high load conditions, then the maximum current is restricted to prevent damage, but the control voltage drifts and leaves the normal operating region, causing prolonged recovery time and increased output voltage overshoot
Solution Approach 1:
The clamp circuit performs preliminary action by clamping the control voltage to a predetermined value before it can drift excessively during current limiting. This prevents the control voltage from leaving the normal operating region entirely, enabling faster recovery when the load condition improves. The clamp circuit is activated in advance to maintain the control voltage within acceptable bounds throughout the current limiting event.
2Reliability
If current limiting is used to protect the power supply during high load conditions, then the maximum current is restricted to prevent damage, but the output voltage overshoot increases significantly during load reduction
Solution Approach 1:
The clamp circuit applies preliminary anti-action by preventing the control voltage from rising too high during current limiting. By clamping the control voltage to a predetermined value, it counteracts the tendency toward excessive voltage overshoot that would occur during subsequent load reduction. This anticipatory constraint on the control voltage directly reduces the harmful overshoot effect on the output voltage.
3Productivity
If the control voltage is allowed to drift during current limiting, then the power supply can maintain maximum current output, but the control voltage leaves the normal operating region requiring prolonged recovery
Solution Approach 1:
The clamp circuit changes the parameter of the control voltage by constraining it to a predetermined value during current limiting conditions. This parameter change prevents the control voltage from drifting outside the normal operating region while still allowing the power supply to deliver maximum current through the current limiting mechanism. The control voltage stability is improved without sacrificing current output capability.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A circuit for a switched-mode-power-supply. The switched-mode-power-supply is configured to: receive a current-control-signal; and provide an output-voltage based on the current-control-signal. The circuit comprises a controller, a current-limiter and a clamp-circuit. The controller is configured to: generate a control-voltage based on the difference between: (i) a sense-voltage, which is representative of the output-voltage of the switched-mode-power-supply; and (ii) a reference-voltage; generate a target-current-control-signal based on the control-voltage, wherein the target-current-control-signal is configured to adjust the current through the switched-mode-power-supply in order to bring the sense-voltage closer to the reference-voltage. The current-limiter is configured to provide the current-control-signal as the target-current-control-signal limited to a max-current-control-value. The clamp-circuit is configured to set the control-voltage to a clamp-voltage-value when the current-limiter provides the current-control-signal having the limited value of the max-current -control-value.