Voltage Converter Discharge Switching for High-Side Overvoltage Protection
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Solution Overview
Problem
The known voltage converting circuit experiences issues with the high-side switch being damaged due to an extended conduction time caused by a slow drop in PWM signal voltage during transitions, leading to an excessively large output voltage.
Innovation Solution
A voltage converting circuit with a discharge switch controlled by various signals (PWM, control signals, bootstrap power, and phase output) to create a fast discharge path during PWM signal transitions, preventing excessive voltage and current buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the PWM signal voltage drops slowly during transitions, then the high-side switch conduction time becomes longer, but the output voltage becomes excessively large which may damage the high-side switch
Solution Approach 1:
The patent extracts the harmful slow voltage drop characteristic from the PWM signal by introducing a separate discharge path through the discharge switch. This discharge switch is controlled independently to rapidly discharge the PWM signal voltage during transitions, separating the normal PWM operation from the transition management, thereby preventing excessive output voltage while maintaining appropriate conduction time control.
Solution Approach 2:
The discharge switch acts as an intermediary component between the PWM signal source and the high-side switch. By controlling the discharge switch based on the control signals, it mediates the voltage transition process, providing a fast discharge path that prevents the PWM signal voltage from dropping too slowly, thus protecting the high-side switch from damage while maintaining proper timing control.
2Reliability
If a discharge switch is added to create a fast discharge path, then the conduction time of the high-side switch is shortened and damage is prevented, but the device complexity increases
Solution Approach 1:
The discharge switch is designed to serve multiple functions: it provides fast discharge during transitions, protects the high-side switch from damage, and works in coordination with existing control signals. By making the discharge switch controllable by various existing signals (PWM signal, control signals, bootstrap power signal, phase output signal), it achieves multi-functionality that justifies its addition to the circuit.
Solution Approach 2:
The patent changes the operational parameters of the discharge switch dynamically - it is enabled or disabled based on different operating conditions and control signals. This parameter-based control allows the discharge switch to activate only when needed (during transitions), providing protection without continuously affecting circuit operation, thereby minimizing the impact on overall device complexity.
Data Source
AI summary
A voltage converting circuit includes a logic circuit, a driver control circuit, a high-side switch, a low-side switch, and a discharge switch. The logic circuit receives a PWM signal from an input node and outputs first and second control signals according to the PWM signal. The driver control circuit receives the first and second control signals and outputs a high-side control signal and a low-side control signal according to the first and second control signals. The high-side and low-side switches respectively receive the high-side control signal and the low-side control signal and correspondingly output a phase output signal. The discharge switch is coupled between the input node and a ground terminal and controlled by at least one of the PWM signal, the first control signal, an inversion of the second control signal, the high-side control signal, an inversion of the low-side control signal, and the phase output signal.