Control Circuit for Power Converter Propagation Delay Compensation
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Solution Overview
Problem
Conventional primary side regulators in power converters suffer from propagation delay errors, leading to inaccurate cut-off points of the power switch and variations in output voltage and current, which degrade line regulation.
Innovation Solution
A control circuit that calculates peak and valley currents by sampling voltages at specific times during the power switch's conduction period, using a current sensing unit, current emulating unit, and control unit to generate a control signal that adjusts the power switch's operation, thereby correcting errors caused by propagation delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional primary side regulator controls power switch conduction period to control inductor current, then circuitry is simple and routing cost is low, but propagation delay causes inductor current error and degrades line regulation
Solution Approach 1:
The patent applies preliminary action by sampling the inductor current at multiple time points (including before, during, and after the power switch conduction period) to predict and correct the actual peak current value. This advance sampling and calculation compensates for propagation delay effects without adding complex real-time feedback circuitry, thus maintaining circuit simplicity while improving measurement precision.
Solution Approach 2:
The patent implements a feedback mechanism where the sampled current values are used to calculate the actual peak current, which then feeds back to adjust the control signal for the power switch. This closed-loop approach corrects errors caused by propagation delay, improving line regulation while keeping the overall circuit structure relatively simple through efficient use of sampling data.
2Device complexity
If propagation delay is not compensated, then control circuit is simple, but output current varies and line regulation degrades
Solution Approach 1:
The control circuit performs preliminary sampling of the inductor current at multiple predetermined time points within and around the power switch conduction period. By calculating the actual peak current from these advance samples before the next switching cycle begins, the system compensates for propagation delay without requiring complex real-time adjustment mechanisms, thus maintaining circuit simplicity while improving reliability.
Solution Approach 2:
The calculated actual peak current from sampled values is fed back to generate an adjusted control signal for the power switch. This feedback loop corrects the effects of propagation delay on output current accuracy, improving line regulation while keeping the control circuit relatively simple through efficient algorithms rather than complex hardware.
3Measurement precision
If multiple sampling points are used to calculate peak and valley currents, then current accuracy improves, but sampling and calculation complexity increases
Solution Approach 1:
The system performs preliminary sampling at multiple fixed time points (t1, t2, t3, t4) that are predetermined based on the switching frequency and conduction period. By calculating peak and valley currents from these pre-sampled values using straightforward algebraic operations, the system achieves high measurement accuracy without requiring complex real-time processing, thus balancing precision with computational simplicity.
Solution Approach 2:
The current waveform is segmented into distinct phases (rising edge, peak, falling edge, valley) with specific sampling points assigned to each phase. This segmentation allows the system to extract peak and valley currents from specific sample combinations, simplifying the calculation process while maintaining measurement accuracy across different operating conditions.
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
The control circuit effectively corrects inductor current errors, improving line regulation and maintaining a constant output current.
Implementation Method 1
an auxiliary winding N3 of the transformer 210, the power switch 220, and the current sensing unit 231. The current emulating unit 232 is configured to determine a propagation delay period according to a voltage transient time of the auxiliary winding
Implementation Method 2
The current sensing unit is configured to sense a current flowing through the power switch, and to convert the current into a voltage
Data Source
AI summary
A control circuit is adapted for controlling a converter. The converter includes a transformer and a power switch. The control circuit includes a current sensing unit, a current emulating unit, and a control unit. The current sensing unit senses a current flowing through the power switch coupled to a primary winding of the transformer. The current emulating unit determines a propagation delay period according to a voltage transient time of an auxiliary winding of the transformer and a turn-off time of the power switch, and retrieves several sampling times in a conduction period of the power switch according to the propagation delay period. The current emulating unit obtains a peak current and a valley current according to the sampling voltages corresponding to the sampling times. The control unit generates a control signal configured to control the power switch according to the peak current and the valley current.