SMPS Driver Timing for Safe Multi-Switch Transitions
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Solution Overview
Problem
As the number of power switches in switched mode power supplies increases, the complexity of drivers grows, and the risk of forbidden switching states leading to undesirable effects such as shoot-through currents and voltage mispositioning becomes more significant, necessitating a solution to prevent these issues.
Innovation Solution
A driver system that receives input signals to control power switches, delaying off-on transitions until all intended on-off transitions have occurred, using logic circuits and arbitration circuits to ensure safe switching sequences and prevent overlap, employing programmable delay signals and feedback mechanisms to manage power switch states effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of power switches is increased to achieve higher power conversion capability, then the power supply performance is improved, but the driver complexity and risk of forbidden switching states increase
Solution Approach 1:
The driver is divided into multiple independent control cells, each responsible for controlling one power switch. Each control cell contains dedicated logic circuits that independently manage the switching sequences, eliminating the need for a single complex centralized driver and reducing overall system complexity while maintaining the ability to handle multiple switches
Solution Approach 2:
The logic circuits within each control cell pre-establish the correct switching sequences by asserting output signals in the proper order. The system performs preliminary validation of switching states before actual switching occurs, ensuring that forbidden states are prevented before they can cause harmful effects
2Power
If the number of power switches is increased to achieve higher power conversion capability, then the power supply performance is improved, but the risk of forbidden switching states and shoot-through currents increases
Solution Approach 1:
The logic circuits in each control cell monitor the states of power switches and use feedback signals to determine when it is safe to transition switches between states. The system continuously checks whether all intended on-off transitions have occurred before allowing off-on transitions, dynamically adjusting switching sequences based on real-time switch states to prevent forbidden conditions
Solution Approach 2:
The logic circuits proactively prevent forbidden switching states by asserting output signals in a predetermined safe sequence. The system applies counter-actions in advance by delaying off-on transitions until all on-off transitions are confirmed complete, thereby preventing shoot-through currents and voltage mispositioning before they can occur
3Reliability
If deadtime is extended to prevent shoot-through currents, then the safety is improved, but the switching efficiency and power loss increase
Solution Approach 1:
The deadtime is made dynamic rather than fixed. The logic circuits adjust the timing of off-on transitions based on the actual completion status of on-off transitions. This dynamic adjustment allows the system to use the minimum necessary deadtime in each switching cycle, preventing shoot-through currents only when absolutely required and reducing unnecessary energy losses during switching transitions
Data Source
AI summary
A driver for driving a switched-mode power supply is presented. The driver receives a set of input signals. Each input signal is configured for changing a state of an associated power switch from a first state to a second state. The driver generates an output signal to change the state of the associated power switch from the first state to the second state. When the first state is an on state and the second state is an off state, the driver asserts the output signal to change the state of the associated power switch to perform an on-off transition. When the first state is the off state and the second state is the on state, the driver delays the assertion of the output signal to perform an off-on transition by a predetermined delay time, so that the off-on transition is delayed until all intended on-off transitions have occurred.