Switched Mode Power Supply Dynamic Frequency Foldback
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Solution Overview
Problem
Switched mode power supplies, particularly flyback converters with active clamp topology, face efficiency challenges at lighter loads due to continuous conduction losses and are not adaptable to varying frequency requirements set by regulatory standards, which demand high frequency operation at full load and low frequency at light or no load conditions.
Innovation Solution
The implementation of a switched mode power converter with dynamic frequency foldback, which operates in hysteretic ACF mode at normal loads, frequency foldback at light loads, and skip mode at very light loads or no load conditions, using a switched mode power supply controller that adjusts the operating frequency based on load conditions to maintain efficiency and comply with regulatory standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the operating frequency is increased to reduce the size of magnetic core and transformer, then the converter size is reduced, but the standby power consumption increases due to increased switching losses at light loads
Solution Approach 1:
The patent implements dynamic frequency adjustment where the switching frequency varies based on load conditions. At full load, the converter operates at high frequency (e.g., 1 MHz) to minimize size, while at light or no load, the frequency automatically reduces (e.g., to 25 kHz or lower) to minimize switching losses and standby power consumption. This dynamic adaptation resolves the contradiction between size reduction and power consumption.
Solution Approach 2:
The patent changes the operating frequency parameter dynamically based on load detection. The controller monitors load conditions and adjusts the switching frequency accordingly, transforming the fixed frequency operation into variable frequency operation. This parameter change enables the converter to optimize between size and power consumption at different operating points.
2Volume of moving object
If the converter operates at fixed high frequency to maintain small size, then the converter remains compact, but efficiency decreases at light loads due to continuous switching losses
Solution Approach 1:
The converter transitions from fixed frequency operation to dynamic frequency operation. The switching frequency is continuously adjusted based on real-time load detection, enabling the converter to operate at high frequency when size is critical and at low frequency when efficiency is paramount, thus resolving the contradiction between maintaining compact size and reducing switching losses.
Solution Approach 2:
The patent implements periodic load assessment and frequency adjustment cycles. The controller periodically evaluates load conditions and modifies the switching frequency accordingly, creating a rhythmic pattern of high-frequency operation during heavy load and low-frequency operation during light load, thereby minimizing energy losses while maintaining size benefits.
3Volume of moving object
If the converter is designed for high frequency operation to meet size requirements, then the magnetic core and transformer can be smaller, but the converter cannot comply with regulatory standards requiring low frequency at light loads
Solution Approach 1:
The patent makes the switching frequency dynamic rather than fixed. The controller detects load conditions and automatically adjusts frequency to comply with regulatory requirements: operating at high frequency (e.g., 1 MHz) during full load to maintain small magnetic core size, and switching to low frequency (e.g., 25 kHz or below) during light or no load to meet standby power regulations. This dynamic behavior enables simultaneous satisfaction of both size and compliance requirements.
Solution Approach 2:
The converter is designed with multi-functional capability to operate effectively across diverse regulatory environments and load conditions. By incorporating variable frequency operation, a single converter design can satisfy multiple regulatory standards (such as DOE Level 6, ErP, and other efficiency regulations) while maintaining compact size, eliminating the need for multiple dedicated converter designs.
4Reliability
If multiple dedicated converter designs are used for different load conditions, then each converter can be optimized for specific conditions, but the device complexity and cost increase
Solution Approach 1:
The patent creates a universal converter design that can adapt to different load conditions through variable frequency operation. A single converter topology with a programmable controller can replace multiple dedicated converters, each optimized for specific conditions. The controller detects load type and frequency requirements, then automatically adjusts operating parameters to match, providing the same optimization benefits as multiple dedicated designs without the complexity and cost of maintaining separate converter designs.
Solution Approach 2:
The converter incorporates dynamic parameter adjustment capabilities that allow a single design to behave differently under various conditions. By making the switching frequency and other parameters dynamically可调, the converter can optimize its performance for different load conditions in real-time, effectively replacing the need for multiple static, dedicated converter designs and reducing overall system complexity.
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 enhances efficiency by reducing power consumption at light loads, meeting strict regulatory efficiency standards, and allows for flexible operation across a wide range of load conditions without the need for multiple dedicated converter designs.
Implementation Method 1
A flyback converter is based on a flyback transformer that alternately builds up flux in the magnetic core and transfers energy to the output. When current is switched through the primary winding, the primary current in the transformer increases, storing energy within the transformer. When the switch is opened, the primary current in the transformer drops, inducing a voltage on the secondary winding.
Implementation Method 2
ACF converters can reduce electric stress on components and improve efficiency by achieving close to zero volt switching (ZVS) of the primary switch and to produce clean drain waveforms without any ringing. They also allow soft increase in secondary current.
Data Source
AI summary
In one form, a switched mode power supply controller with frequency foldback includes a pulse width modulator responsive to a clock signal to generate a drive signal having a pulse width that varies in response to a feedback signal, and a variable frequency oscillator having a first input for receiving the feedback signal, a control input for receiving a control signal defining a foldback starting frequency, a foldback ending frequency, a foldback starting voltage, and a foldback ending voltage, and an output for providing the clock signal having a variable frequency that varies over a range between the foldback starting frequency and the foldback ending frequency as the feedback signal varies between the foldback starting voltage and the foldback ending voltage, respectively. The control signal is user programmable for at least one of the foldback starting frequency, the foldback ending frequency, the foldback starting voltage, and the foldback ending voltage.