Sensor-Feedback Gate Driver Circuit for Through-Current Suppression
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Solution Overview
Problem
In motor driver circuits, rapid changes in gate voltage of high-side and low-side transistors lead to through-currents and ringing due to reverse recovery currents of flywheel diodes, which existing gate driver circuits struggle to effectively suppress.
Innovation Solution
A gate driver circuit is designed with high-side and low-side sensors that assert detection signals when potential differences across transistor nodes cross threshold levels, allowing the control circuit to adjust driving capabilities and detect abnormalities, such as ground faults or short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gate voltage is changed rapidly to improve switching speed, then the productivity is improved, but through-current and ringing occur due to reverse recovery current of flywheel diodes
Solution Approach 1:
The gate driver circuit dynamically adjusts its driving capability based on the switching state. During turn-on, the driver operates in a first driving state with higher current supply capability to charge the gate quickly. During turn-off, it switches to a second driving state with lower current supply capability to suppress reverse recovery current. This dynamic adaptation allows fast switching while minimizing harmful through-currents.
Solution Approach 2:
The invention changes the driving capability parameter of the gate driver circuit according to the switching phase. By controlling the current supply capability to be higher during turn-on and lower during turn-off, the circuit achieves fast switching speed while suppressing reverse recovery effects. The sensor output triggers these parameter changes in real-time during operation.
2Object-generated harmful factors
If the driving capability is reduced to suppress through-current and ringing, then the harmful factors are reduced, but the switching speed decreases
Solution Approach 1:
The gate driver circuit dynamically adjusts its driving capability based on the switching state. During turn-on, the driver operates in a first driving state with higher current supply capability to charge the gate quickly. During turn-off, it switches to a second driving state with lower current supply capability to suppress reverse recovery current. This dynamic adaptation allows fast switching while minimizing harmful through-currents.
Solution Approach 2:
The gate driver circuit applies periodic switching between two driving states corresponding to the switching frequency of the power transistor. During each switching cycle, the driver provides high current capability during the turn-on phase and reduces current capability during the turn-off phase. This periodic modulation of driving capability enables fast switching while suppressing reverse recovery effects at each transition.
3Measurement precision
If sensors are added to detect potential difference for adjusting driving capability, then the control precision is improved, but the device complexity increases
Solution Approach 1:
The sensor circuit serves multiple functions: it detects the potential difference between gate and source to determine transistor switching state, generates control signals for adjusting driving capability, and enables both turn-on and turn-off phase control. This multi-functionality reduces the need for separate control circuits and sensors, thereby limiting the increase in device complexity while achieving precise measurement.
Solution Approach 2:
The sensor provides feedback about the gate-source potential difference to the gate driver circuit. Based on this feedback, the driver automatically adjusts its driving capability by switching between first and second driving states. This feedback mechanism enables precise control of the switching process without requiring complex external control systems, as the adjustment is performed autonomously within the gate driver itself.
Data Source
AI summary
A gate driver circuit includes: a high-side sensor that asserts a high-side detection signal when a potential difference between two nodes of a high-side transistor constituting an inverter circuit crosses a threshold level; a high-side driver configured to be capable of supplying a high voltage or a low voltage between a gate and a source of the high-side transistor and have a controllable driving capability; and a control circuit that causes the high-side driver to generate the high voltage when a control signal instructs turning-on of the high-side transistor, and changes the driving capability of the high-side driver in response to an assertion of the high-side detection signal, wherein the control circuit determines that abnormality has occurred when the assertion of the high-side detection signal does not occur within a predetermined time.