Power converter and air-conditioning apparatus
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Solution Overview
Problem
Existing bootstrap circuits in power converters experience increased size, power loss, and heat generation due to large current flows during capacitor charging, and voltage drops in the control power supply can lead to abnormal stops, especially when using intermittent charging methods without considering internal impedance and pulse width.
Innovation Solution
A power converter design with a series-connected switching element configuration, including a gate drive circuit with first and second drive circuits and a power supply module, uses variable pulse widths to charge the bootstrap capacitor, minimizing voltage drops by adjusting pulse widths based on allowable voltage drops and internal impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a large current is used to charge the bootstrap capacitor quickly, then the charging speed is improved, but voltage drop and power loss occur in the control power supply
Solution Approach 1:
The patent applies dynamics by making the pulse width variable rather than fixed. The control unit adjusts the pulse width dynamically based on the charging state of the bootstrap capacitor, allowing the charging current to be high initially for fast charging and then reduced as the capacitor approaches full charge, thereby minimizing power loss while maintaining charging speed.
Solution Approach 2:
The patent uses periodic action by implementing intermittent charging through repeated pulse signals. The control unit outputs pulse signals with controlled widths in a periodic manner, allowing the bootstrap capacitor to charge in stages rather than continuously, which reduces the average current and minimizes power loss in the control power supply.
2Reliability
If the pulse width is increased to ensure sufficient charging current, then the charging reliability is improved, but voltage drop in the control power supply increases
Solution Approach 1:
The patent applies parameter changes by adjusting the pulse width parameter based on the charging state. Instead of using a fixed large pulse width that causes voltage drop, the control unit varies the pulse width parameter dynamically - using larger widths when needed for reliability and smaller widths when the capacitor is nearly charged, thus maintaining charging reliability while minimizing voltage drop stress.
Solution Approach 2:
The patent implements feedback by having the control unit monitor the charging state of the bootstrap capacitor and adjust the pulse width accordingly. The control unit receives feedback about the capacitor's charge level and modifies the pulse width in response, ensuring sufficient charging current for reliability while preventing excessive voltage drop by reducing pulse width when appropriate.
3Loss of energy
If intermittent charging is used to reduce current, then power loss is reduced, but voltage drop may still occur without proper pulse width control
Solution Approach 1:
The patent applies dynamics by making the pulse width adaptive rather than fixed. The control unit dynamically adjusts the pulse width based on real-time charging state feedback, ensuring that intermittent charging reduces power loss while the dynamic adjustment maintains charging stability by providing sufficient current when needed.
Solution Approach 2:
The patent uses parameter changes by varying the pulse width parameter during the charging process. The control unit changes the pulse width parameter based on the charging state, allowing intermittent charging to reduce power loss while maintaining charging stability through appropriate parameter adjustment that ensures sufficient charging current is delivered.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the probability of voltage drops during bootstrap capacitor charging, preventing abnormal stops and minimizing power loss, while maintaining efficient capacitor charging.
Implementation Method 1
a bootstrap capacitor 133, and a power supply module 137 including a limiting resistor 131, a bootstrap diode 132, and the bootstrap capacitor 133 connected in series between the control power supply 135 and the output terminal 126
Implementation Method 2
a power supply module 137 including a limiting resistor 131, a bootstrap diode 132, and the bootstrap capacitor 133 connected in series between the control power supply 135 and the output terminal 126
Implementation Method 3
a power supply module 137 including a limiting resistor 131, a bootstrap diode 132, and the bootstrap capacitor 133 connected in series between the control power supply 135 and the output terminal 126
Data Source
AI summary
A power converter includes a power converting module and a gate drive circuit that includes first and second drive circuits and a power supply module including a limiting resistor, a bootstrap diode, and a bootstrap capacitor, and configured to generate a voltage to be supplied to the second drive circuit. The bootstrap capacitor is charged when a switching element connected to a reference potential side performs switching. A charging period of the bootstrap capacitor includes at least first and second periods. In the first period, the switching element is driven by a pulse signal having a first pulse width. In the second period, the switching element is driven by a pulse signal having a second pulse width greater than the first one. The first pulse width in the first period is determined based on an allowable magnitude of a voltage drop of the control power supply in the first period.