High-Side Driver Control Circuit for 100 Percent Duty Cycle Bootstrap Voltage
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Solution Overview
Problem
Existing semiconductor devices face challenges in generating high-voltage for high-side transistors, requiring large capacitors that occupy significant area and increase costs, while bootstrap circuits often fail to achieve a 100% duty cycle and introduce electromagnetic interference noise.
Innovation Solution
A control circuit configuration that includes a voltage generation circuit with a charging and storage circuit, utilizing a flying capacitor and diodes to store and maintain a bootstrap voltage, allowing for smaller capacitors and reduced area usage, while enabling a 100% duty cycle and minimizing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a bootstrap circuit or charge pump circuit is used to generate high-voltage for high-side transistors, then the high-voltage can be supplied to enable the transistors, but large capacitors are required which occupy significant area and increase costs
Solution Approach 1:
The capacitor is divided into two separate capacitors (first capacitor and second capacitor) that operate at different voltage levels. The first capacitor operates at a lower voltage and stores energy, while the second capacitor operates at the boosted voltage level. This segmentation allows each capacitor to be optimized for its specific voltage range, reducing the total area required compared to a single large capacitor operating at high voltage.
Solution Approach 2:
A voltage boost circuit is introduced as an intermediary between the low-voltage energy storage capacitor and the high-voltage load. This boost circuit temporarily stores energy in the first capacitor, then uses switching elements (transistors and diodes) to transfer and boost the voltage to the second capacitor, which supplies the high-side transistor. This intermediary approach eliminates the need for a single large high-voltage capacitor.
2Adaptability or versatility
If a bootstrap circuit is used to provide high-voltage, then the circuit can be integrated onto the semiconductor device, but the bootstrap circuit cannot enable high-side transistors with a substantially 100% duty cycle
Solution Approach 1:
The first capacitor is charged in advance during periods when the high-side transistor is off, storing energy before it is needed. The control circuit monitors the voltage on the first capacitor and activates the boost circuit to charge the second capacitor before the high-side transistor needs to be enabled again. This preliminary charging action ensures that sufficient energy is available even during continuous or high-duty-cycle operation.
Solution Approach 2:
The control circuit incorporates feedback mechanisms that monitor the voltage levels on both capacitors and adjust the switching of the boost circuit accordingly. When the voltage on the first capacitor drops below a threshold or when the second capacitor needs recharging, the control circuit automatically activates the boost circuit to transfer energy. This feedback control ensures continuous operation capability regardless of duty cycle requirements.
3Power
If traditional high-voltage generation circuits are used, then the required high-voltage can be supplied, but electromagnetic interference noise is generated
Solution Approach 1:
The voltage boost circuit operates in periodic cycles rather than continuously. The switching elements (transistors and diodes) are activated in controlled periodic intervals to transfer energy from the first capacitor to the second capacitor. This periodic operation, rather than continuous switching, reduces the frequency and intensity of electromagnetic interference generated during high-voltage generation, while still maintaining the ability to supply the required high-voltage to the load.
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
The solution effectively generates high-voltage for high-side transistors with a 100% duty cycle, reduces capacitor size and area requirements, and minimizes electromagnetic interference, enhancing the efficiency and cost-effectiveness of semiconductor devices.
Implementation Method 1
store an interim voltage, greater than the input voltage, on a first capacitor for at least a portion of a first time interval that the second switch is enabled
Implementation Method 2
couple the first capacitor to supply current and voltage to operate the first driver in response to controlling the first driver to enable the first switch
Data Source
AI summary
In one embodiment, a control circuit for a high side driver forms alternate signals to control a store mode and a maintain mode. An embodiment of the control circuit stores a voltage that is greater than an input voltage which results in storing a large charge for at least a portion of one of the cycles. The charge is used to supply operating voltage to the driver for at least a portion of another of the cycles.