Bootstrap Drive Voltage Control for Low-Noise Switching Power Supplies
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Solution Overview
Problem
Existing switching power supplies face challenges in efficiently controlling the bootstrap circuit, leading to noise characteristics and power supply efficiency issues.
Innovation Solution
The proposed solution involves a power supply controller with an output transistor drive circuit that uses a drive voltage having a first voltage (VBOOT−Vf) to switch the output transistor from an off state to an on state and then increases the drive voltage to a second voltage (VBOOT) when the insertion transistor is turned on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional bootstrap circuit is used to drive the output transistor, then the output transistor can be switched on and off, but noise characteristics deteriorate and power supply efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the drive voltage variable rather than fixed. The drive voltage generation circuit dynamically adjusts the drive voltage level based on the switching state: applying a first drive voltage during turn-on transition and a second drive voltage during on-state maintenance. This dynamic adjustment optimizes both noise characteristics and power supply efficiency by matching the drive voltage to the specific operational phase.
Solution Approach 2:
The patent changes the voltage parameter of the drive signal applied to the output transistor. Instead of using a constant bootstrap voltage, the system generates two distinct voltage levels (first drive voltage and second drive voltage) and selectively applies them based on the switching phase. This parameter change resolves the contradiction by optimizing the voltage level for each specific operational requirement.
2Reliability
If the drive voltage is continuously high to ensure reliable transistor switching, then switching reliability improves, but power consumption increases and efficiency decreases
Solution Approach 1:
The patent applies partial action by providing different levels of drive voltage depending on the switching phase. During the turn-on transition, a higher first drive voltage is applied to ensure reliable switching. Once the transistor is fully on, the voltage is reduced to a lower second drive voltage that maintains reliability while reducing power consumption. This partial application of high voltage only when necessary resolves the contradiction between reliability and energy efficiency.
Solution Approach 2:
The patent implements periodic action by alternately applying different drive voltage levels corresponding to the switching cycle phases. The drive voltage generation circuit periodically switches between the first drive voltage (during turn-on) and the second drive voltage (during on-state), creating a rhythmic pattern of high and low voltage application that maintains reliability while minimizing continuous power consumption.
3Device complexity
If the bootstrap circuit is simplified to reduce complexity, then device complexity decreases, but control precision and noise performance deteriorate
Solution Approach 1:
The patent applies universality by designing a drive voltage generation circuit that performs multiple functions within a single integrated structure. The circuit generates both the first drive voltage and the second drive voltage, automatically selects the appropriate voltage level based on switching phase, and provides this to the output transistor. This multi-functional approach achieves precise control and good noise performance without requiring separate complex circuits for each function.
Data Source
AI summary
A power supply controller provided in a switching power supply which generates output voltage from input voltage and configured to control operation of the switching power supply includes: an output stage including an output element between an application terminal for the input voltage and a switch terminal, and a rectifier element between the switch terminal and a reference potential terminal; a control circuit to generate control signal according to the output voltage; and an output element drive circuit to turn on or off the output element according to the control signal by drive voltage for turning on the output element, wherein when switching the output element from an off state to an on state, the output element drive circuit switches the output element from the off state to the on state by the drive voltage having first voltage and increases the drive voltage to second voltage.