Bridge Output Circuit Gate Voltage Control
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Solution Overview
Problem
Bridge output circuits experience increased response delay and power loss due to varying load currents, leading to inefficient operation when trying to maintain a constant slew rate of the output voltage.
Innovation Solution
The implementation of assist circuits and voltage monitoring units in the bridge output circuit allows for rapid gate voltage control, enabling the output voltage to transition with a constant slope and reducing response delay while maintaining a consistent slew rate, by using assist circuits to pre-condition the gate voltage before slew rate control begins and switching current sources based on threshold voltage comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the slew rate of the switching voltage is increased to reduce response delay, then the response delay is reduced, but high frequency components are increased causing noise
Solution Approach 1:
The assist circuit pre-charges or pre-discharges the gate capacitance of the power transistor before the main switching action. By preparing the gate voltage in advance, the main switching transistor can transition more quickly between on and off states, reducing response delay without requiring excessive current that would generate harmful high-frequency noise.
2Object-affected harmful factors
If the slew rate of the switching voltage is restricted to reduce noise, then noise is reduced, but response delay increases
Solution Approach 1:
The assist circuit performs preliminary charging or discharging of the gate capacitance, so that when the main switching signal arrives, the transistor is already close to its target state. This eliminates the need for a high slew rate during the main switching event, thereby reducing noise while maintaining fast response.
3Stability of the object's composition
If a constant current source is used to control gate voltage for maintaining constant slew rate, then slew rate is maintained constant, but response delay increases due to fixed current limitation
Solution Approach 1:
The patent replaces the static constant current source with a dynamic assist circuit that can adjust its current output based on real-time switching conditions. The assist circuit provides higher current when needed for fast transitions and reduces current when the transistor approaches its target state, thereby maintaining constant slew rate while reducing overall response delay.
Solution Approach 2:
The assist circuit anticipates the switching requirements by actively managing gate voltage before and during the switching event. By dynamically adjusting current in real-time rather than using a fixed constant current source, the system achieves both fast response and controlled slew rate.
Data Source
AI summary
A bridge output circuit includes an output terminal, a high side transistor, a low side transistor, a high side driver for controlling a gate voltage of the high side transistor, a low side driver for controlling a gate voltage of the low side transistor, and a controller for controlling the high side and low side drivers. The low side driver includes a first current source, a second current source, and a first assist circuit. The controller is configured to control the turning-on and turning-off states of the first current source, the second current source and the first assist circuit.