High Side Switch Bootstrap Charge Maintenance
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Solution Overview
Problem
Standard high side switch controllers for MOSFET and IGBT devices fail to maintain bootstrap capacitor charge when the load is absent or has high resistance, leading to discharge and failure to turn on the switching device, especially in static switching conditions without PWM.
Innovation Solution
An electrical switching circuit with a primary and secondary energy storage system, where a controllable switch toggles between circuit ground and the primary energy storage unit, and unidirectional current gates facilitate charging of the secondary energy storage device, which in turn charges the primary device, ensuring continuous operation regardless of load resistance or switching mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bootstrap capacitor is used to generate gate-to-source potential, then the switching device can be turned on, but the capacitor discharges and the switching device remains off when the load is absent or has very high resistance
Solution Approach 1:
The patent introduces a second energy storage device as an intermediary between the first energy storage device (bootstrap capacitor) and the power source. This intermediary device is periodically charged from the power source and used to recharge the first energy storage device, ensuring continuous charge maintenance even when the load is absent or has high resistance, thus preventing the switching device from remaining off due to capacitor discharge
Solution Approach 2:
The patent implements periodic charging action through a controllable switch that periodically connects the second energy storage device to charge the first energy storage device. This periodic action ensures that the bootstrap capacitor is continuously recharged at regular intervals, maintaining the necessary gate-to-source potential for reliable switching device operation regardless of load conditions
2Loss of energy
If PWM switching is used to recharge the bootstrap capacitor, then the capacitor can be kept charged during OFF state intervals, but the switching device cannot be turned on statically without PWM
Solution Approach 1:
The patent creates a universal charging system that can support multiple switching operation modes (both PWM and static switching) through the addition of the second energy storage device and periodic charging circuitry. This multi-functional design allows the bootstrap capacitor to be recharged regardless of whether the system operates in PWM mode or static switching mode, making the circuit adaptable to different application requirements without requiring mode-specific charging solutions
3Reliability
If the controllable switch periodically charges the secondary energy storage device, then the primary energy storage device remains charged, but the circuit complexity increases
Solution Approach 1:
The patent implements a self-service charging mechanism where the controllable switch automatically periodically connects the second energy storage device to charge the first energy storage device based on voltage detection. The circuit self-regulates the charging process through the unidirectional current gate and voltage comparison, eliminating the need for complex external control circuitry or manual intervention, thus maintaining reliability while minimizing added complexity
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 ensures the bootstrap capacitor remains charged, allowing the switching device to function correctly even without PWM intervals, maintaining reliable operation across varying load conditions and switching modes.
Implementation Method 1
a primary unidirectional current gate coupled between the high side of the secondary energy storage device and the high side of the primary energy storage device to let current flow from the secondary energy storage device to the primary energy storage device when the potential difference of the high side of the secondary energy storage device is higher than the high side of the primary energy storage device
Implementation Method 2
a controllable electrical switch that toggles the low side of the secondary energy storage device from the circuit ground to the low side of the primary energy storage device
Implementation Method 3
a secondary unidirectional current gate coupled between a secondary power source with an electrical potential difference of at least the predetermined potential relative to the circuit ground and the high side of the secondary energy storage device to let current flow from the secondary power source to the high side of the secondary energy storage device when the potential difference of the secondary power source is higher than the high side of the secondary energy storage device
Data Source
AI summary
An electrical switching circuit for controlling current flow to an electrical load from a primary power source with a first electrical potential difference relative to a circuit ground comprising a primary energy storage device with a low side coupled to the electrical load, a secondary electrical energy storage device with a high side and a low side, a controllable electrical switch that toggles the low side of the secondary energy storage device from the circuit ground to the low side of the primary energy storage device, a primary unidirectional current gate coupled between the high side of the secondary energy storage device and the high side of the primary energy storage device to let current flow from the secondary energy storage device to the primary energy storage device when the potential difference of the high side of the secondary energy storage device is higher than the high side of the primary energy storage device, a secondary unidirectional current gate coupled between a secondary power source with an electrical potential difference of at least the predetermined potential relative to the circuit ground and the high side of the secondary energy storage device to let current flow from the secondary power source to the high side of the secondary energy storage device when the potential difference of the secondary power source is higher than the high side of the secondary energy storage device, wherein periodic operation of the secondary electrical switch charges the secondary energy storage device when the secondary switch toggles its low side to the circuit ground and the secondary energy storage device charges the primary storage device when the secondary switch toggles its low side to the low side of the primary energy storage device.