Variable-Current Load Driver for Fast Switching With Lower Hold Current
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Solution Overview
Problem
Existing load drivers face challenges in turning on switching elements quickly while minimizing current consumption, particularly in driver circuits, due to continuous high current supply after the switching element reaches the on state, leading to increased power consumption and potential damage from overshoot.
Innovation Solution
A load driver design that includes a constant current generator supplying a first current value to turn on the switching element quickly and then reduces to a second, lower current value once the element is on, using a variable constant current circuit to manage current flow and reduce consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high value constant current is supplied to turn on the switching element quickly, then the rising time is shortened and switching speed increases, but current consumption in the driver circuit increases continuously
Solution Approach 1:
The patent applies periodic action by switching between two constant current values (first and second current values) based on the switching state. During turn-on period, a higher first current value is supplied to quickly charge the gate capacitance and achieve fast switching. After the switching element reaches on-state, the current is reduced to a lower second current value to maintain the on-state while minimizing current consumption. This time-varying current supply strategy resolves the contradiction between fast switching and low power consumption.
Solution Approach 2:
The patent implements dynamics by making the constant current value changeable based on operational phase. The constant current generator dynamically switches between different current levels (first current value during turn-on, second current value during on-state) using control circuitry that monitors the switching element's state. This dynamic adaptation allows the system to optimize both switching speed and power consumption at different operational stages.
2Reliability
If a clamp circuit is connected to restrict gate voltage overshoot, then the switching element is protected from damage, but a current path is formed and constant current is continuously supplied to the clamp circuit increasing power consumption
Solution Approach 1:
The patent applies periodic action to the clamp circuit current supply by making it time-dependent. The clamp circuit receives the first current value during the turn-on period to quickly establish protection and achieve switching. After the switching element reaches on-state, the current to the clamp circuit is reduced to the second current value. This periodic current supply pattern maintains protection functionality while eliminating continuous high current consumption through the clamp circuit.
Solution Approach 2:
The patent implements dynamics in the clamp circuit operation by dynamically adjusting the constant current level based on the switching element's state. The control circuitry monitors whether the switching element is in transition or steady on-state, and accordingly adjusts the current supplied to the clamp circuit between the first and second current values. This dynamic control maintains reliability during switching while reducing power consumption during steady operation.
Data Source
AI summary
A load driver includes a switching element connected to a load, a constant current generator that generates a constant current, and a driver circuit that turns on the switching element for an on-period, which depends on a value of the constant current and is shortened with an increase in the value of the constant current. The constant current generator supplies a first constant current having a first current value to the driver circuit during the on-period, and supplies a second constant current having a second current value smaller than the first current value after the on-period has elapsed and the switching element reaches an on state.