Sequential Gate Drive Control for Parallel Power Devices
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Solution Overview
Problem
Conventional load driving circuits for gate-driven power devices, such as IGBTs, do not effectively minimize switching losses when driving multiple power devices in parallel, as they often result in increased turn-on current for subsequent devices, leading to inefficiencies and potential damage from overcurrent.
Innovation Solution
A load driving device with separate turn-on and turn-off drive circuits for each power device, where the control circuit manages the gate voltage change rates to prevent overcurrent and minimize losses, by turning on the first device with a lower gate voltage build-up rate and the second device with a higher rate only after the first device is stable, and vice versa during turn-off, using current detection to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple power devices are driven in parallel with simultaneous turn-on, then large current can be supplied to the load, but turn-on surge current increases causing overcurrent damage
Solution Approach 1:
The patent divides the turn-on process into sequential stages by controlling multiple power devices to turn on at different timings. The first power device turns on with a controlled gate voltage change rate, and subsequent devices turn on after a predetermined time delay, segmenting the total turn-on process to limit surge current while maintaining total current capability.
Solution Approach 2:
The patent applies preliminary action by turning on the first power device before the others, allowing it to establish initial current flow and voltage conditions. This preliminary turn-on creates a controlled baseline that prevents simultaneous switching surge when subsequent devices are activated.
2Object-affected harmful factors
If the first power device is turned on with a controlled gate voltage change rate to prevent overcurrent, then overcurrent damage is avoided, but switching losses increase
Solution Approach 1:
The patent applies different gate voltage change rates dynamically to different power devices based on their turn-on sequence. The first device uses a slower change rate for safety, while subsequent devices use faster change rates to minimize their individual switching losses, optimizing the overall balance between protection and efficiency.
Solution Approach 2:
The patent changes the gate voltage application parameters by using different change rates for different devices. The control circuit adjusts the gate voltage change rate parameter according to the turn-on sequence, applying a first change rate to the first device and a second change rate to subsequent devices, thereby optimizing both protection and loss reduction.
3Loss of energy
If subsequent power devices are turned on with higher gate voltage change rate to reduce their switching losses, then turn-on losses decrease, but current control precision must be carefully managed
Solution Approach 1:
The patent incorporates current detection circuits that monitor the actual current flow through each power device. This feedback mechanism allows the control circuit to adjust the gate voltage application timing and rate for subsequent devices, ensuring that even with faster turn-on rates, the current remains within safe limits and control precision is maintained.
Data Source
AI summary
A load driving device includes: a first turn-on drive circuit turning on a first power device as one of a plurality of gate-driven power devices; a second turn-on drive circuit turning on a second power device as another one of the plurality of gate-driven power devices different from the first power device; a current detection circuit detecting a current in at least the first power device; and a control circuit controlling the first turn-on drive circuit to turn on the first power device by applying a gate voltage with a first change rate, and subsequently controlling the second turn-on drive circuit to turn on the second power device by applying a gate voltage with a second change rate, which is larger than the first change rate, based on a condition in which the current detection circuit does not detect an overcurrent in the first power device.