Switching Power Supply Control Circuit for Constant Frequency and Dead Time
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Solution Overview
Problem
Existing switching power supplies face challenges in maintaining a constant switching frequency and optimizing dead time to prevent simultaneous switching element activation, leading to inefficiencies and potential noise issues.
Innovation Solution
A switching power supply design that includes a direct-current power-supply input unit, a transformer with magnetically coupled windings, and switch circuits with complementary turn-on and turn-off operations, utilizing a switching control circuit with a triangular wave oscillator and comparators to determine switching element timings based on feedback and monitor signals, ensuring constant frequency and optimal dead time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dead time is provided to prevent simultaneous switching of multiple elements, then reliability is improved, but switching frequency varies and switching noise occurs in a wide range
Solution Approach 1:
The patent applies dynamics by making the dead time variable rather than fixed. The control circuit dynamically adjusts the dead time duration based on real-time detection of switching element states and circuit conditions, allowing the system to maintain reliable operation while adapting to different operating points and load conditions, thereby reducing unnecessary wideband noise
Solution Approach 2:
The patent implements feedback by using detection circuits to monitor the actual switching states and circuit parameters, then feeding this information back to the control circuit. This closed-loop control enables precise timing of switching elements, ensuring proper dead time implementation while maintaining constant switching frequency and minimizing noise generation
2Reliability
If a dead time having the same time length is set in a full load region, then reliability is improved, but efficiency deteriorates in steady state
Solution Approach 1:
The patent applies dynamics by implementing variable dead time that adapts to different operating conditions. In transient states, a longer dead time ensures reliable switching, while in steady-state full load conditions, the dead time is optimized to be shorter, reducing energy losses and improving efficiency without compromising reliability
Solution Approach 2:
The patent changes the parameter of dead time duration based on operating conditions. The control circuit modifies the dead time parameter dynamically - maintaining a conservative, reliable value during transients and optimizing it for efficiency during steady-state operation, thereby resolving the contradiction between reliability and efficiency
3Device complexity
If the on-time of the second switching element is determined by a time constant circuit including a resistor and a capacitor, then switching control is simplified, but switching frequency varies and switching noise occurs
Solution Approach 1:
The patent replaces the open-loop RC time constant circuit with a closed-loop feedback control system. The control circuit receives feedback about actual switching states and circuit conditions, then actively adjusts switching element timing to maintain constant frequency, eliminating the frequency variation and noise inherent in passive RC-based approaches
Solution Approach 2:
The patent substitutes the passive mechanical/electrical RC time constant system with an active electronic control system using comparison circuits and feedback mechanisms. This replacement transitions from a fixed, noise-generating time constant approach to a controlled, frequency-stable switching scheme
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 configuration enables a reliable and efficient switching power supply with reduced noise and improved EMI characteristics, allowing for stable output voltage and efficient energy transmission.
Implementation Method 1
a transformer T being configured by one magnetic component and including at least a first primary winding np and a first secondary winding ns1, magnetically coupled
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3(A)~3(B)
AI summary
The comparator (110) outputs the first determination criterion signal (Vcmp) on the basis of the saw-tooth wave signal (Vchp) whose level fluctuates with a constant period and the detection voltage signal (Vo). The inverter (113) subjects the first determination criterion signal (Vcmp) to reverse processing, and outputs the second determination criterion signal (Vcmp'). The comparator (111) outputs the first switching judgment-use signal (Vtrl)) from the monitor signal (Vm) and the threshold value (VI), and the comparator (112 outputs the second switching judgment-use signal, (Vtr2) from the monitor signal (Vm) and the threshold value (V2). The AND circuit (114) outputs the first switching control signal (Vgs1) from the first determination criterion signal (Vcmp) and the first switching judgment-use signal (Vtr1) and the AND circuit (115) outputs the second switching control signal (Vgs2) from the second determination criterion signal (Vcmp) and the second switching judgment-use signal (Vtr2)