Gate Driver Power Supply Circuit for Isolated Bootstrap Charging
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Solution Overview
Problem
Load driving circuits face challenges in providing isolated and electrically floating supply voltages to high side gate drivers, leading to decreased performance and prolonged startup sequences due to energy draw from the source supply voltage and lengthy initialization processes.
Innovation Solution
An augmented power supply circuit that includes an isolated power supply and a cyclic charging power supply, with a control circuit to regulate power delivery, ensuring the supply voltage is maintained or increased during transistor on-states, and providing an initial charge to bootstrap capacitors during startup, thereby enabling arbitrary duty cycles and accelerated startup times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bootstrap power supply circuit is used to provide isolated supply voltage to the high side gate driver, then galvanic isolation is achieved, but the supply voltage decreases during transistor on-states due to energy draw
Solution Approach 1:
The isolated power supply circuit pre-charges the bootstrap capacitor during transistor off-states before the transistor turns on. This preliminary charging action ensures that the capacitor has sufficient energy stored to maintain the supply voltage during the subsequent on-state, preventing voltage collapse while preserving galvanic isolation.
Solution Approach 2:
The power supply operates in periodic cycles, alternating between charging the bootstrap capacitor during off-states and supplying power during on-states. This periodic operation allows the capacitor to be recharged regularly, maintaining adequate voltage levels throughout the switching cycle while preserving isolation between primary and secondary sides.
2Reliability
If a bootstrap power supply circuit is used, then isolated supply voltage is provided, but initialization requires an undesirably prolonged startup sequence
Solution Approach 1:
During the startup sequence, the isolated power supply circuit performs preliminary charging of the bootstrap capacitor before normal operation begins. This advance charging action eliminates the need for prolonged startup sequences involving low side gate driver operation, as the capacitor is ready to provide isolated supply voltage immediately when needed.
3Productivity
If the gate driver draws energy from the source of supply voltage while driving the load, then the load is driven effectively, but the supply voltage decreases to levels that impact gate driver performance
Solution Approach 1:
The bootstrap capacitor is charged in advance during transistor off-states, storing energy before it is needed. This preliminary energy storage allows the gate driver to draw sufficient current to drive the load effectively without causing the supply voltage to collapse, as the capacitor acts as a local energy reservoir.
Solution Approach 2:
The bootstrap capacitor serves as an intermediary energy storage element between the isolated power supply and the gate driver. It decouples the gate driver's high current demands from the power supply, allowing the driver to draw energy rapidly without directly impacting the supply voltage level, thus maintaining both load driving capability and voltage stability.
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 maintains or increases supply voltage levels, allowing for arbitrary duty cycle variations and rapid startup sequences, improving the performance and reliability of load driving circuits by selectively controlling power delivery through current, voltage, or temperature regulation modes.
Implementation Method 1
an isolated power supply circuit to provide power to a cyclic charging power supply circuit
Implementation Method 2
cyclic charging of a capacitive energy storage element
Data Source
AI summary
An embodiment of a power supply circuit to generate a supply voltage for a gate driver circuit can include an isolated power supply circuit to receive a first voltage in a first isolated system and provide power to a cyclic charging power supply circuit, the cyclic charging power supply circuit providing a supply voltage to the gate driver circuit in a second isolated system, the isolated power supply circuit providing the power to the cyclic charging power supply circuit while the gate driver circuit drives a transistor in an on state. The isolated power supply circuit can include a control circuit to regulate the power provided to maintain or increase the supply voltage while the gate driver circuit drives the transistor in an on state. The power supply circuit can also include the cyclic charging power supply circuit to receive a second voltage in the second isolated system and provide the supply voltage to the gate driver circuit. The cyclic charging power supply circuit can include one or more of a bootstrap power supply circuit or a charge pump power supply circuit.