Switching Power Supply Adaptive Frequency Control
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Solution Overview
Problem
Conventional switching power supply apparatuses face challenges in maintaining a stable power factor and reducing noise and switching losses, especially when parameters such as input voltage, output voltage, and inductance vary, leading to inefficient operation and impaired response performance.
Innovation Solution
A switching power supply apparatus with a chopper circuit that includes a second threshold signal generator circuit, which adjusts the voltage dividing ratio based on frequency error signals to maintain a constant switching frequency, thereby optimizing ON- and OFF-periods of the switching device and reducing noise and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If critical conduction mode control method is used, then switching noise is reduced, but current ripple increases causing large stress on inductor and diode
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the switching frequency based on operating conditions (load current, input voltage). By changing the switching frequency parameter adaptively, the system achieves lower current ripple under heavy load while maintaining low switching noise, thus resolving the contradiction between noise reduction and stress reduction on components.
2Strength
If continuous conduction mode control method is used, then current ripple is reduced, but switching noise increases
Solution Approach 1:
The patent implements dynamics by making the switching frequency variable rather than fixed. The control system dynamically adjusts switching frequency based on real-time operating conditions, allowing the system to transition between conduction modes adaptively. This dynamic approach enables the system to maintain low current ripple when needed while controlling switching noise through frequency adjustment.
3Adaptability or versatility
If switching frequency varies with input voltage and inductance, then circuit adaptability improves, but power factor stability deteriorates
Solution Approach 1:
The patent applies feedback by implementing a control system that monitors operating conditions and adjusts switching frequency accordingly. The feedback mechanism ensures that despite variations in input voltage and inductance, the power factor remains stable by compensating for parameter changes through adaptive frequency adjustment, thus resolving the contradiction between adaptability and stability.
4Speed
If switching frequency increases, then response performance improves, but switching losses increase
Solution Approach 1:
The patent implements dynamics by making switching frequency variable and adaptive to operating conditions. Instead of using a fixed high switching frequency that causes excessive losses, the system dynamically adjusts frequency to achieve necessary response performance while minimizing switching losses. This dynamic frequency adjustment resolves the contradiction between response speed and energy efficiency.
Data Source
AI summary
In a switching power supply apparatus, multiplier 9 multiplies error voltage Verr generated in voltage error amplifier 8 and input voltage Vin to generate first threshold signal Vth1 in-phase with and similar to input voltage Vin and having an amplitude proportional to error voltage Verr. Second threshold signal generator circuit 14 generates second threshold signal Vth2 from first threshold signal Vth1. Switching device 7 is turned on and off so that the inductor current may change between first and second threshold signals Vth1 and Vth2. The switching frequency is detected and the proportional factor of first and second threshold signals Vth1 and Vth2 is changed to control the average switching frequency almost at a constant value for reducing the high frequency noises and the switching losses. The switching power supply apparatus facilitates reducing the noises and losses, improving the power factor thereof, and preventing the response performances thereof from being impaired.