Power Supply Circulation Current Compensation Using PWM Phase Shifting
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Solution Overview
Problem
Switched power supplies face inefficiencies due to circulation currents in coupled inductors, leading to magnetic saturation and coupling losses, which existing methods like using hall current transducers are costly to mitigate.
Innovation Solution
A power supply system that includes a pulse width modulator, inverter legs, a phase shifter, and a compensator to generate and combine pulse width modulation signals, with a compensation signal calculated as Y = 2 × Δm to counteract circulation currents within the coupled inductor, minimizing magnetic saturation and maximizing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple switching legs are combined in a coupled inductor to increase efficiency and reduce hardware cost, then power supply efficiency is improved, but circulation currents arise causing magnetic saturation and coupling losses
Solution Approach 1:
The invention applies preliminary action by calculating and applying a compensation signal to the second PWM control signal before the circulation current problem occurs. The compensator determines the compensation signal based on the modulation wave signal m(n) and applies it in advance to prevent magnetic saturation in the coupled inductor, rather than detecting and correcting the problem after it occurs.
Solution Approach 2:
The invention changes the parameter of the PWM control signal by adding a compensation signal Y = 2 × Δm to the second PWM control signal. This parameter modification adjusts the switching timing and duty cycle to eliminate the circulation current while maintaining the benefits of multiple switching legs operating in parallel.
2Object-generated harmful factors
If hall current transducers are used in each switching leg to measure and counteract circulation current, then circulation current compensation is achieved, but hardware cost increases significantly
Solution Approach 1:
The invention extracts the circulation current compensation function from the expensive hall current transducer approach and implements it through a mathematical calculation-based compensator. Instead of using physical sensors to detect circulation current, the system extracts the necessary information from the modulation wave signal and computes the compensation signal, eliminating the need for expensive current sensing hardware.
Solution Approach 2:
The invention replaces expensive hall current transducers with a low-cost computational approach using basic arithmetic operations on PWM signals. The compensation signal is generated through simple mathematical calculations (Y = 2 × Δm) rather than expensive physical measurement devices, dramatically reducing hardware cost while achieving the same compensation effect.
3Device complexity
If circulation current is not compensated, then hardware remains simple, but magnetic saturation occurs leading to coupling losses and reduced efficiency
Solution Approach 1:
The invention implements feedback by using the modulation wave signal m(n) to generate a compensation signal that is fed back to the second PWM control signal. This closed-loop approach continuously adjusts the switching signals based on the modulation waveform to prevent circulation current and magnetic saturation, maintaining high efficiency without complex hardware.
Data Source
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Figure 3
Figure 4~5
AI summary
A power supply (1) for generating an output signal (OUT) is provided. The power supply (1) comprises a first inverter leg (11) and a second inverter leg (12), respectively adapted to generate a first pulse width modulation signal (PWM1) and a second pulse width modulation signal (PWM2) by modulating an input DC voltage (IN). Moreover, the power supply (1) comprises a phase shifter (120), which is adapted to generate a provisional second pulse width modulation signal (PWM2') by phase shifting a signal (PWM1CTRL), which the first pulse width modulation signal (PWM1) is derived from. Furthermore, the power supply (1) comprises a compensator (121), which is adapted to determine the second pulse width modulation signal (PWM2) from the provisional second pulse width modulation signal (PWM2'). Especially, the compensator (121) adds a compensation signal during the generating of the second pulse width modulation signal (PWM2). Finally, the power supply (1) comprises a coupled inductor (13), which is adapted to combine the first pulse width modulation signal (PWM1) and the second pulse width modulation signal (PWM2) to form the output signal (OUT).