Synchronous Rectifier DC-DC Converter Control Circuit for Overshoot Prevention
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Solution Overview
Problem
Existing DC-DC converters in portable electronic devices face challenges in reducing power consumption and preventing overshoot and chattering in output voltage, particularly when transitioning between load states, leading to inefficiencies and increased power losses.
Innovation Solution
A control circuit for a synchronous rectifier-type DC-DC converter that includes a first switching element for accumulating power in an induction element and a second switching element for supplying power to a load, with a detecting unit that maintains the second switching element in a conductive state after discharge, using a hysteresis comparator and gate circuits to manage the switching states based on output voltage thresholds, preventing overshoot and stabilizing voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the switching section is frequently switched between ON and OFF states to precisely control power supply, then the power supply control precision is improved, but the power losses increase due to increased switching frequency
Solution Approach 1:
The patent changes the control parameter from simple ON/OFF switching to pulse width modulation (PWM) duty ratio control. By adjusting the duty ratio of the PWM signal, the patent achieves precise power supply control while reducing the number of complete switching cycles, thereby lowering switching losses. The control section varies the duty ratio based on output voltage feedback to maintain precise control without excessive switching frequency.
2Stability of the object's composition
If the switching section is kept in ON state to supply continuous power to load, then the power supply stability is improved, but the power consumption increases
Solution Approach 1:
The patent implements periodic PWM switching action instead of continuous ON state. The switching section operates in periodic cycles with variable duty ratios, where the ON time is optimized to maintain power supply stability while minimizing energy consumption. The periodic switching allows the system to maintain average power delivery stability without requiring continuous high-power conduction.
3Speed
If the switching frequency is increased to improve power supply response, then the power supply response speed is improved, but the power losses increase
Solution Approach 1:
The patent implements dynamic duty ratio adjustment based on real-time output voltage feedback. The control section dynamically modifies the PWM duty ratio in response to load conditions and voltage variations, achieving fast power supply response without requiring high switching frequency. This dynamic control allows the system to respond quickly to changes by adjusting pulse width rather than increasing switching frequency, thereby avoiding associated power losses.
4Loss of energy
If the duty ratio is optimized to reduce switching losses, then the power losses are reduced, but the control complexity increases
Solution Approach 1:
The patent employs feedback control where the control section monitors the output voltage and adjusts the PWM duty ratio accordingly. This closed-loop feedback mechanism automatically optimizes the duty ratio to minimize switching losses while maintaining stable output voltage. The feedback approach simplifies the control logic compared to complex predictive algorithms, as it uses real-time voltage information to adjust switching parameters, achieving loss reduction without excessive control complexity.
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
The solution effectively suppresses power losses and stabilizes output voltage by maintaining the second switching element in an ON state after power discharge, preventing overshoot and reducing chattering, thus enhancing the efficiency and longevity of portable electronic devices.
Implementation Method 1
a first switching element that is made conductive when power is accumulated in an induction element
Implementation Method 2
using a hysteresis comparator and gate circuits to manage the switching states based on output voltage thresholds
Data Source
AI summary
To provide a control circuit for a synchronous rectifier-type DC-DC converter, a synchronous rectifier-type DC-DC converter and a control method thereof in which, in a light load state and a no-load state, an output voltage can be dropped to thus prevent an overshoot state from continuing. A synchronous rectifier-type DC-DC converter 10 and a control circuit 20A thereof comprising a first switching element FET1 that is made conductive when power is accumulated in an induction element L1, and a second switching element FET2 that is made conductive when power accumulated in induction element L1 is supplied to a load, also comprises a detecting unit COMP2 that detects that a value of an output voltage VOUT of the synchronous rectifier-type DC-DC converter 10A is a predetermined voltage value that is higher than a target voltage value, and control units COMP1 and OR1 that maintain the second switching element FET2 in a conductive state after discharge of the power accumulated in the induction element L1 is finished, based on the detection results of the detecting unit COMP2.