Adaptive High-Side Gate Drive for Soft-Switching Resonant Converters
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Solution Overview
Problem
Resonant power converters experience hard switching and high voltage stress on power devices when the output voltage is low, leading to reduced reliability due to insufficient voltage for soft-switching of the high-side switch.
Innovation Solution
An adaptive slew rate control method and circuit are implemented to generate high-side drive signals with fast or slow slew rates based on bias voltage thresholds, ensuring soft-switching for the high-side switch, using a high-side drive circuit and a switching control circuit to manage path resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the high-side switch is turned on with fast slew rate to achieve soft-switching, then switching efficiency is improved, but voltage stress on power devices increases when output voltage is low
Solution Approach 1:
The high-side drive circuit dynamically adjusts the slew rate of the drive signal based on the bias voltage level. When bias voltage is sufficient (above threshold), the circuit uses fast slew rate to enable soft-switching and improve efficiency. When bias voltage is insufficient (below threshold), the circuit automatically switches to slow slew rate to prevent hard-switching and reduce voltage stress on power devices.
Solution Approach 2:
The invention changes the slew rate parameter of the high-side drive signal based on the bias voltage condition. By monitoring the bias voltage level and adjusting the slew rate accordingly, the system optimizes the trade-off between switching efficiency and device reliability under different operating conditions.
2Reliability
If the bias voltage is increased to ensure soft-switching, then reliability is improved, but the complexity of the power supply circuit increases
Solution Approach 1:
The bootstrap capacitor circuit serves multiple functions: it provides the bias voltage for the high-side drive circuit and simultaneously enables the slew rate adjustment mechanism. This multi-functional design achieves reliability improvement without adding separate dedicated circuits for each function.
Solution Approach 2:
The high-side drive circuit automatically adjusts its own slew rate based on the bias voltage level it receives. The circuit monitors its own operating conditions and self-regulates the drive signal characteristics without requiring external control, simplifying the overall system architecture.
Data Source
AI summary
A circuit of a resonant power converter comprising: a high-side switch and a low-side switch, coupled to form a half-bridge switching circuit which is configured to switch a transformer for generating an output voltage; a high-side drive circuit, generating a high-side drive signal coupled to drive the high-side switch in response to a high-side control signal; a bias voltage, coupled to a bootstrap diode and a bootstrap capacitor providing a power source from the bootstrap capacitor for the high-side drive circuit; wherein the high-side drive circuit generates the high-side drive signal with a fast slew rate to turn on the high-side switch when the high-side switch is to be turned on with soft-switching; the high-side drive circuit generates the high-side drive signal with a slow slew rate to turn on the high-side switch when the high-side switch is to be turned on without soft-switching.