Switching Power Supply Light Load Detection Control
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Solution Overview
Problem
Existing switching power supply apparatuses face inefficiencies at rated loads due to high switching surge voltages, large conduction losses, and poor output response characteristics, especially during light and heavy load fluctuations.
Innovation Solution
A switching power supply apparatus with a direct-current power-supply input, a transformer, and series circuits including switching elements and an inductor, where a light load detection mechanism controls the on-time ratio of switching elements to maintain high efficiency and reduce switching losses across varying loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is reduced at standby time to reduce switching loss, then switching loss is reduced, but the power consumption of the switching control circuit cannot be reduced sufficiently
Solution Approach 1:
The patent changes the operating parameters of the switching control circuit by reducing the power supply voltage to near minimum allowable operating voltage during light load conditions, while maintaining high switching frequency. This allows the control circuit to operate with reduced power consumption even at high switching frequencies, resolving the contradiction between maintaining high switching frequency (for fast response) and reducing control circuit power consumption.
2Reliability
If a high-voltage switching element is used to withstand large switching surge voltage, then voltage breakdown is prevented, but conduction loss increases and efficiency decreases
Solution Approach 1:
The patent introduces a voltage breakdown prevention circuit as an intermediary component that protects the switching element from voltage breakdown without requiring the switching element itself to have high voltage withstand capability. This mediator circuit absorbs the voltage stress, allowing the use of low-voltage switching elements with low conduction loss while still preventing voltage breakdown.
3Loss of energy
If intermittent oscillation operation is used to reduce switching loss, then switching loss is reduced, but output voltage ripple increases and audible noise is generated
Solution Approach 1:
The patent employs periodic action through high-frequency switching operations that are too fast to be perceived as audible noise. By operating at frequencies above the audible range and maintaining continuous periodic switching, the patent reduces switching loss while avoiding the audible noise and excessive ripple problems associated with lower frequency intermittent oscillation methods.
4Use of energy by moving object
If switching frequency is increased to reduce control circuit power consumption, then control circuit efficiency is improved, but switching loss increases
Solution Approach 1:
The patent simultaneously changes multiple parameters: it increases switching frequency to improve control circuit efficiency while implementing voltage breakdown prevention and using appropriate switching elements to minimize the increase in switching loss. The voltage breakdown prevention circuit and optimized switching element selection allow the system to operate at higher frequencies with acceptable switching loss.
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 achieves high efficiency and excellent output response characteristics by reducing switching operations and drive losses, minimizing output ripple, and maintaining voltage accuracy across light, rated, and heavy loads.
Implementation Method 1
a transformer (T) configured to include at least a primary winding (np) and a secondary winding (ns), magnetically coupled to each other
Data Source
AI summary
In a switching power supply apparatus, a first switching element is controlled by a driving voltage output from a switching control IC. A second switching control circuit controls the on-time of a second switching element so that the time ratio of the on-time of the second switching element to the on-time of the first switching element becomes almost constant with respect to a change in a load current. In a normal load state, since a square wave output from a frequency setting unit within the switching control IC is output with no change, a converter operates in a current-continuous mode. In a light load state, a driving signal generation unit within the switching control IC is subjected to blanking with the period of a signal output from a maximum frequency setting unit and an oscillation frequency is reduced. Accordingly, the converter operates in a current-discontinuous mode.