DC-DC Converter Pulse Skipping Circuit Prevents Backward Current
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Solution Overview
Problem
DC-DC converters face issues with backward current flow when the load becomes light, leading to potential damage to switching elements due to delayed control and electromagnetic energy reversal.
Innovation Solution
Incorporating a pulse skipping detecting circuit that switches off the second switching element when the PWM control circuit stops outputting a pulse signal for a predetermined period, allowing the first pulse skipping detecting circuit to preemptively switch off the second switching element before the light load detecting circuit, thereby preventing backward current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a synchronous rectifying method is used to supply returning current to the load, then power efficiency is improved, but backward current flows from the smoothing circuit to the synchronous rectifying circuit when the load becomes light, causing potential damage to switching elements
Solution Approach 1:
The light load detecting circuit detects the light load condition in advance and generates a light load detection signal before backward current can flow. This preliminary detection allows the synchronous rectifying switching element to be switched off proactively, preventing the harmful backward current from occurring in the first place
Solution Approach 2:
The control circuit continuously monitors the load condition through the light load detecting circuit and adjusts the switching state of the synchronous rectifying element based on the detected load level. This feedback mechanism ensures that the switching element is properly controlled to prevent backward current while maintaining efficient synchronous rectification during normal operation
2Reliability
If the light load detecting circuit is used to switch off the synchronous rectifying switching element, then backward current is prevented, but the control response is delayed causing the switching element to be switched off after backward current has already flowed
Solution Approach 1:
The light load detecting circuit is designed to detect load conditions in advance and generate the light load detection signal before backward current can flow. This preliminary action ensures that the synchronous rectifying switching element is switched off proactively, eliminating the delay that would otherwise occur after backward current starts flowing
3Loss of energy
If the synchronous rectifying switching element is kept on during light load, then power efficiency is maintained, but electromagnetic energy reverses and causes backward current flow
Solution Approach 1:
The light load detecting circuit continuously monitors the load condition and provides feedback to the control circuit. When the load becomes light, this feedback signal triggers the switching off of the synchronous rectifying element, preventing electromagnetic energy reversal and backward current flow while maintaining efficient operation during normal load conditions
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
This solution effectively reduces backward current flow and prevents damage to switching elements by ensuring timely control during load changes from heavy to light, maintaining system stability and efficiency.
Implementation Method 1
a first inductance element connected between the first intermediate terminal and an output terminal
Implementation Method 2
a first capacitor connected between the output terminal and the terminal to which the second potential is applied
Implementation Method 3
a PWM control circuit which detects a voltage of the output terminal, and outputs a pulse signal having a pulse width determined based on the voltage of the output terminal
Data Source
AI summary
A DC-DC converter has a switching circuit including switching elements at the high-side and at the low-side, an inductor connected to the output end of the switching circuit, a smoothing capacitor connected to the inductor, a switching control circuit for supplying a switching pulse to the switching elements, and a circuit. The circuit detects that a state that the switching element at the high side is switched off and the switching element at the low side is switched on is maintained for a predetermined period or longer. In this case, the circuit forcibly switches off the switching element at the low side.