Digital Control for Switch Mode Power Supply Saturation
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Solution Overview
Problem
Modern switch mode power supplies face inefficiencies due to high switching losses in DC-DC converters, particularly at high input voltages and varying voltage conditions, leading to potential transformer saturation and transistor failure without active power factor correction.
Innovation Solution
A digital control module regulates the duty cycle and switching frequency of the control signal to maintain constant maximum magnetic core flux density, preventing transformer saturation and transistor failure by adjusting the duty cycle and frequency based on input voltage levels, and using an output feedback circuit to continuously adjust the control signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching frequency is increased to improve power conversion efficiency, then the power loss increases proportionally to the squared value of the bulk voltage, but the switching losses of the DC-DC converter primary transistor increase dramatically
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The control module dynamically adjusts the switching frequency based on the bulk voltage level - using lower frequencies at high voltages to reduce switching losses, and higher frequencies at lower voltages to maintain power conversion efficiency. This dynamic adaptation resolves the contradiction between maintaining efficiency and reducing switching losses across varying operating conditions.
Solution Approach 2:
The patent changes the parameter of switching frequency based on bulk voltage conditions. By monitoring the bulk voltage and adjusting the switching frequency accordingly, the system optimizes the trade-off between power conversion efficiency and switching losses. This parameter adaptation allows the power supply to operate efficiently across a wide input voltage range without suffering from excessive switching losses at high voltages.
2Device complexity
If active power factor correction is not used to simplify the circuit, then the device complexity is reduced, but the power supply cannot handle wide input voltage variation effectively and suffers from dramatic power loss variation
Solution Approach 1:
The patent implements dynamic control of the DC-DC converter without requiring complex active PFC circuitry. The control module continuously monitors bulk voltage and dynamically adjusts operating parameters to adapt to wide input voltage variations. This dynamic approach provides the adaptability of active PFC while maintaining simpler circuit architecture, resolving the contradiction between circuit complexity and voltage variation handling capability.
3Power
If the duty cycle is increased to improve power transfer, then the power loss due to switching process increases, but the power conversion efficiency decreases
Solution Approach 1:
The patent changes multiple parameters including switching frequency and duty cycle based on bulk voltage conditions. At high bulk voltages, the system uses lower switching frequencies and optimizes duty cycle to minimize switching losses while maintaining adequate power transfer. This coordinated parameter adjustment resolves the contradiction between power transfer capability and switching loss minimization.
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 reduces power dissipation, allows for smaller components, decreases output voltage noise, and minimizes electromagnetic interference while maintaining efficiency across varying input conditions.
Implementation Method 1
a primary winding and a secondary winding. The primary winding of the transformer is coupled to a rectified input voltage and the secondary winding of the transformer provides an AC output voltage
Implementation Method 2
a transistor having a control terminal, a first current terminal and a second current terminal. The control terminal of the transistor is coupled to the control signal and the first current terminal of the transistor is coupled to the primary winding
Data Source
AI summary
A power supply includes an input filter and rectifier module, a digital control module, and a converter module. The input filter and rectifier module is configured to rectify an input voltage. The digital control module is adapted to prevent a potential saturation of a transformer by setting a maximum allowable duty cycle for a control signal transmitted to the transistor based on an input voltage. The digital control model is further adapted to reduce switching losses in the power supply by setting the control signal switching frequency, based on the input voltage. The converter module is configured to convert the input voltage into a direct current output voltage based upon the control signal.