Switching Power Supply Frequency Control Circuit
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Solution Overview
Problem
Current resonant type switching power supply devices experience oscillation in the feedback control loop and inrush current issues due to linear control of switching frequency and cycle, leading to instability and startup problems.
Innovation Solution
A switching power supply device with a frequency control circuit that divides control regions based on feedback signal size, executing linear frequency control when feedback is low and linear cycle control when feedback is high, using a comparator and oscillator to generate a pulse width modulated drive signal, thereby preventing oscillation and inrush current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear frequency control is used to control the switching frequency in accordance with the feedback signal, then the output voltage can be maintained, but oscillation occurs in the feedback control loop and inrush current issues arise
Solution Approach 1:
The patent changes the control parameter from linear frequency control to dual-mode control (linear frequency control for low feedback signals, linear cycle control for high feedback signals). This parameter change resolves the contradiction by selecting different control modes based on operating conditions, preventing oscillation and inrush current while maintaining output voltage stability.
Solution Approach 2:
The patent implements dynamic switching between two control modes based on the feedback signal level. The control circuit automatically transitions between linear frequency control and linear cycle control, making the system adaptive to different operating conditions and eliminating the harmful effects of fixed linear frequency control.
2Reliability
If linear cycle control is used to control the switching cycle in accordance with the feedback signal, then startup issues can be addressed, but unintended gain rises occur in the feedback loop causing oscillation
Solution Approach 1:
The patent changes the control strategy by introducing dual-mode control that selects between linear frequency control and linear cycle control based on feedback signal level. This prevents the unintended gain rises that occur with pure linear cycle control while maintaining startup stability benefits.
Solution Approach 2:
The patent makes the control system dynamic by automatically switching between control modes. During startup when feedback is low, linear cycle control provides stable operation; during normal operation when feedback is high, linear frequency control prevents gain rise and oscillation.
3Measurement precision
If the feedback control loop gain is increased to maintain output voltage, then voltage regulation improves, but oscillation occurs in the feedback control loop
Solution Approach 1:
The patent changes the control parameter selection based on operating conditions. By using linear cycle control at low feedback levels and linear frequency control at high feedback levels, the system maintains good voltage regulation while preventing feedback loop oscillation that would occur with continuously high gain.
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 approach stabilizes switching operations by selectively switching between linear frequency and cycle control, suppressing unintended gain rises in the feedback loop and preventing oscillation, effectively addressing startup issues and maintaining stable output voltage.
Implementation Method 1
the second switching element Q2 is turned on, generating current resonance in a resonant circuit formed of the capacitor Cr, inductor Lr, and a leakage inductor Lm of the insulating transformer T
Implementation Method 2
The first switching element Q1 is connected in series to a primary coil P of an insulating transformer T in series via a capacitor Cr and inductor Lr
Implementation Method 3
the output circuit is such that alternating voltage generated in the secondary coils S1 and S2 of the insulating transformer T is rectified via the diodes D1 and D2
Data Source
AI summary
Included are a switching power supply device main body, and a frequency control circuit that controls the switching frequency of a switching element in accordance with a feedback signal in accordance with the output voltage of the switching power supply device main body. The frequency control circuit is divided into a frequency control region wherein the amount of the feedback signal is greater than a predetermined boundary value and a frequency control region wherein the amount is less, linear frequency control whereby the switching frequency of the switching element is caused to change linearly in accordance with the feedback signal is executed in the frequency control region wherein the feedback amount is less, and linear cycle control whereby the switching cycle of the switching element is caused to change linearly in accordance with the feedback signal is executed in the frequency control region wherein the feedback amount is greater.