Bootstrap Circuit Voltage Stabilization for High-Side Drivers
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Solution Overview
Problem
Existing semiconductor devices face challenges in maintaining a stable supply voltage to high-side driver circuits when the ON time of high-side switching devices is long, leading to increased power consumption and complexity due to the need for high breakdown voltage devices and complex bootstrap circuit configurations.
Innovation Solution
A semiconductor device with a supplementary bootstrap capacitor connected in parallel to the main bootstrap capacitor, charged by an intermediate voltage when the high-side switching device is ON, and a Zener diode to regulate the charging voltage, which compensates for voltage decreases in the main capacitor, ensuring stable power supply to the high-side driver circuit without requiring high breakdown voltage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the ON time of the high-side switching device is long, then the charge stored in the bootstrap capacitor decreases, but it becomes difficult to maintain the required supply voltage for the high-side driver circuit
Solution Approach 1:
The patent charges the bootstrap capacitor in advance during the period when the low-side switching device is ON, before the high-side switching device needs to operate. This preliminary charging ensures that sufficient voltage is stored in the capacitor to support the high-side driver circuit throughout the entire ON period of the high-side switching device, even when this duration is extended.
2Reliability
If a floating power supply is used to charge the bootstrap capacitor, then the supply voltage can be maintained, but the device complexity and cost increase
Solution Approach 1:
The patent enables the bootstrap capacitor to charge itself using the existing low-side switching device and power supply circuitry. When the low-side switching device is ON, the power supply automatically charges the bootstrap capacitor through the existing circuit paths, eliminating the need for separate floating power supply circuits or additional active charging components.
3Device complexity
If the bootstrap capacitor is charged directly from the high-voltage DC voltage via a resistor, then the circuit is simplified, but the resistor becomes a load that discharges the capacitor and increases power consumption
Solution Approach 1:
The patent removes the resistive charging path from the circuit by eliminating the need for a charging resistor. Instead of charging through a resistor that continuously leaks current, the bootstrap capacitor is charged through the low-side switching device when it is ON, and the charging path is effectively disconnected when the low-side device turns OFF, preventing discharge and reducing power consumption.
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 configuration allows for stable operation of the high-side driver circuit even with long ON times of the high-side switching device, reducing power consumption and component costs while maintaining a simple bootstrap circuit design.
Implementation Method 1
a Zener diode to regulate the charging voltage
Implementation Method 2
a bootstrap capacitor connected to a power supply that supplies driving power to the low-side driver circuit via a diode such that the bootstrap capacitor is charged when the low-side switching device is ON
Data Source
AI summary
A semiconductor device includes: a bootstrap capacitor charged via a diode when a low-side switching device is ON, a resulting charge voltage being applied to a high-side driver circuit when the low-side switching device is OFF; a supplementary bootstrap capacitor charged when the low-side switching device is OFF; a Zener diode that regulates a charge voltage of the supplementary bootstrap capacitor; and a control circuit that applies the charge voltage of the supplementary bootstrap capacitor to the high-side driver circuit via a switch circuit when the charge voltage of the bootstrap capacitor decreases to less than a prescribed voltage while a high-side switching device is ON.