Half-Bridge Bootstrap Circuit Dynamic Duty Cycle Control
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Solution Overview
Problem
Existing half-bridge bootstrap circuits control the low-side switch with a constant minimum duty cycle, limiting the maximum power of the motor as its power increases, necessitating a dynamic control method to adapt to varying operational phases of the load.
Innovation Solution
A method and circuit that dynamically control the minimum duty cycle by adjusting the turn-on times of the high-side and low-side switches based on the motor's rotational speed, using a control circuit to manage charging and discharging periods and adjust the duty cycle curve accordingly, ensuring sufficient capacitor charging and maximizing motor power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant minimum duty cycle is used to ensure sufficient capacitor charging, then the high-side switch can remain turned on reliably, but the maximum motor power is limited as motor power increases
Solution Approach 1:
The patent applies dynamics by transitioning from a static, fixed minimum duty cycle to a dynamic, adjustable minimum duty cycle that varies with motor operating conditions. The control circuit dynamically modifies the minimum duty cycle parameter based on detected motor state (such as speed or load), allowing the system to adapt the capacitor charging time to actual power requirements. This enables higher motor powers to be achieved while maintaining sufficient capacitor charging for high-side switch operation.
2Quantity of substance
If the turn-on time of the low-side switch is increased to charge the capacitor, then the capacitor has sufficient energy storage, but the motor power output is reduced due to longer OFF periods
Solution Approach 1:
The patent implements dynamics by making the minimum duty cycle a variable parameter that adapts to motor operating conditions. During high-power operation, the control circuit reduces the minimum duty cycle requirement, allowing shorter low-side switch turn-on times while still maintaining adequate capacitor charging. This dynamic adjustment optimizes the trade-off between capacitor energy storage and motor power output capability.
Solution Approach 2:
The patent applies parameter changes by modifying the minimum duty cycle parameter based on motor operating state. The control circuit detects motor conditions (such as speed or current) and adjusts the minimum duty cycle parameter accordingly. This allows the system to change the charging time parameter dynamically, reducing it when high power is needed and increasing it when lower power operation is sufficient, thereby optimizing both capacitor charging and motor power output.
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 allows for increased motor power by dynamically adjusting the minimum duty cycle according to operational phases, preventing power limitations and ensuring efficient energy storage and transmission, thereby enhancing motor performance.
Implementation Method 1
a boot capacitor, a high-side switch, and a low-side switch... When the high-side switch is turned off and the low-side switch is turned on, the DC voltage may charge the boot capacitor. When the high-side switch is turned on and the low-side switch is turned off, the energy stored in the boot capacitor may keep the high-side switch turned on
Data Source
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AI summary
A half-bridge bootstrap circuit includes a high-side switch, a low-side switch, and a boot capacitor. A dynamically controlled minimum duty cycle curve is adopted to guarantee the minimum turn-on time of the low-side switch so that the boot capacitor can be sufficiently charged for keeping the high-side switch in the turn-on state. Also, the value of the minimum duty cycle curve can be dynamically set according to different operational phases of a load, thereby increasing the maximum output power of the load.