SMPS Controller Valley Detection Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing SMPS controllers face false triggering issues due to spurious valley detection caused by the ringing frequency of the coil, leading to premature actuation of the switch, which can result in inefficient power supply and potential damage.
Innovation Solution
Implementing a SMPS controller that requires a valley to be detected only when the monitored rate of change of input voltage falls below a predetermined threshold and the voltage drop exceeds another threshold, using a monitoring circuit with comparators and a timer to ensure accurate valley detection and prevent false triggering, and incorporating a 'gate stretch' signal to manage the switching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a capacitor is coupled to the junction between the coil and switch to provide power to the controller, then the controller can operate without an auxiliary winding, but the capacitor begins to conduct when the voltage on the switch has fallen by a certain amount, which slows down the ringing frequency and causes false triggering of the valley detection circuit
Solution Approach 1:
The patent applies preliminary action by asserting a gate stretch signal before the actual valley detection occurs. This gate stretch signal is asserted when the rate of change of voltage falls below a first predetermined threshold, which happens before the true valley point. By preparing the system in advance with this preliminary signal, the patent ensures that the switch is not accidentally triggered by the capacitor's conduction slowing the ringing frequency, while still enabling the controller to operate without an auxiliary winding.
Solution Approach 2:
The patent implements dynamics by using multiple changing thresholds for valley detection. Instead of a single static threshold, it employs a first predetermined threshold for the rate of change of voltage and a second predetermined threshold for the voltage drop. These dynamic thresholds adapt to the changing conditions during the switching cycle, allowing the system to distinguish between the capacitor's conduction effect and the true valley point, thereby preventing false triggering while maintaining simplicity.
2Loss of energy
If valley detection is used to minimize switching losses, then switching efficiency is improved, but the detection may be triggered prematurely by spurious valleys caused by ringing frequency changes, leading to incorrect switch actuation
Solution Approach 1:
The patent applies preliminary action by asserting a gate stretch signal before the actual valley detection occurs. This gate stretch signal is asserted when the rate of change of voltage falls below a first predetermined threshold, which happens before the true valley point. By preparing the system in advance with this preliminary signal, the patent ensures that the switch is not accidentally triggered by the capacitor's conduction slowing the ringing frequency, while still enabling the controller to operate without an auxiliary winding.
Solution Approach 2:
The patent implements parameter changes by using multiple changing thresholds for valley detection. Instead of a single static threshold, it employs a first predetermined threshold for the rate of change of voltage and a second predetermined threshold for the voltage drop. These dynamic thresholds adapt to the changing conditions during the switching cycle, allowing the system to distinguish between the capacitor's conduction effect and the true valley point, thereby preventing false triggering while maintaining simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents false triggering and ensures accurate valley detection, thereby minimizing switching losses and preventing damage from premature actuation, leading to a more efficient and reliable power supply.
Implementation Method 1
the current through a capacitor is related to the rate of change of voltage. Thus, when the current is zero, it can be inferred that the rate of change of voltage is also zero and the voltage is at a peak or valley.
Implementation Method 2
The discrimination between a peak and a valley is made with an auxiliary winding electromagnetically coupled to the coil; the polarity of the voltage on this auxiliary winding at the point where the current through the capacitor reaches zero will be different for peaks and valleys.
Implementation Method 3
A second diode is coupled the junction between the capacitor and first diode to clamp the voltage at that point to ground potential.
Data Source
Figure 1
AI summary
A switched mode power supply (SMPS) controller is disclosed. The controller comprises a monitoring circuit adapted to monitor the rate of change of a voltage at an input (1) and to monitor the drop in voltage at the input (1) from a peak value. The controller is adapted to generate a signal for closing the switch when the monitored rate of change falls below a first predetermined threshold and the monitored drop in voltage exceeds a second predetermined threshold.