Power Switch Gate Drive Circuit for Turn-On Current Limiting
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Solution Overview
Problem
In power supply systems, the current overshoot during the turning-on period of power switches leads to reduced system efficiency and reliability due to uncontrolled current flow, which is exacerbated by the reverse recovery process of freewheeling diodes, necessitating prolonged driving times to prevent damage.
Innovation Solution
A drive method and circuit that utilize a current limiting module to control the current during the turning-on period of power switches, with a logic control module to manage the current limiting module and a voltage comparator to quickly turn on the power switch when the drain-source voltage reaches a threshold, ensuring the current is maintained at a predetermined limited value until the switch is fully conductive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driving time for turning on the main switch is increased to prevent current overshoot, then the current control problem is solved, but the system efficiency is reduced
Solution Approach 1:
The patent applies dynamics by making the gate voltage increase at different rates during different stages of the turning-on period. Specifically, the gate voltage increases at a first slope during the current limited period and at a second slope (faster) during the current non-limited period. This dynamic adjustment of voltage rise rate allows the system to prevent current overshoot when needed while minimizing the turning-on time overall, thus resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent divides the turning-on period into distinct periodic stages: a current limited period where current is controlled, and a current non-limited period where the switch turns on rapidly. This periodic structure allows the system to apply current limiting only during the critical initial phase, then transition to rapid switching, thereby preventing overshoot while maintaining high efficiency.
2Reliability
If the driving time for turning on the main switch is increased to prevent current overshoot, then the current control problem is solved, but the driving time cannot be optimized
Solution Approach 1:
The patent uses dynamic control by adjusting the gate voltage slope based on the switching stage. The control circuit detects the current status and dynamically changes the voltage rise rate, allowing the system to spend more time on current-controlled turning-on when necessary and minimize time during rapid turning-on, thus optimizing the overall driving time while maintaining reliable current control.
Solution Approach 2:
The patent changes the parameter of gate voltage rise slope from a fixed value to a variable value that depends on the switching stage. By changing this parameter dynamically (first slope during current limited period, second slope during non-limited period), the system optimizes the driving time while ensuring current control reliability.
3Reliability
If different driving delay times are used for different switches and temperatures, then the current control is accurate, but the device complexity increases
Solution Approach 1:
The patent applies self-service by enabling the control circuit to automatically detect the current status and adjust the gate voltage slope accordingly. The system self-regulates the turning-on process based on real-time conditions without requiring external intervention or complex pre-programming for different devices and temperatures, thus maintaining accurate current control while reducing design complexity.
Solution Approach 2:
Instead of using fixed delay times for different devices and temperatures, the patent dynamically changes the gate voltage slope parameter based on the actual switching stage and current conditions. This parameter change approach eliminates the need for complex device-specific and temperature-specific delay configurations, simplifying the design while maintaining control accuracy.
Data Source
AI summary
Disclosed a drive method, a drive circuit for a power switch and a power supply system. During the turning-on period of the power switch, which can be roughly divided into three processes, a current limiting module is used to limit the current flowing through the power switch for preventing current overshoot, a logic control module is used for controlling the current limiting module not to operate before the turning-on period and the control terminal of the power switch is turned off; during the turning-on period, a feedback circuit adjusts the gate voltage of the power switch for controlling the current flowing through the power switch to reach a predetermined limited value quickly and then maintain at the limited value until the power switch is fully turned on. The current limiting module can be employed in various embodiments. According to the disclosure, the current flowing through the power switch can be effectively controlled during the turning-on period, and the driving time for turning on the power switch is decreased.