Current Mode PWM Boost Circuit Feedback Signal Sensing
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Solution Overview
Problem
Conventional current mode PWM boost circuits face issues with signal distortion, open-loop instability, and noise sensitivity when measuring inductor current and generating slope compensation ramp signals, particularly at high duty cycles.
Innovation Solution
A current mode PWM boost circuit that employs a feedback signal generating unit with a current source and capacitor to directly measure inductor current and equivalent slope compensation ramp signals, eliminating the need for voltage-to-current transfer structures and enabling direct signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If voltage-to-current transfer structures (resistors or transconductance amplifiers) are used to generate inductor current and slope compensation ramp signals, then the circuit can operate in continuous conduction mode with duty cycle greater than 50%, but signal distortion occurs and open-loop instability arises
Solution Approach 1:
The patent extracts and eliminates the voltage-to-current transfer structures (resistors or transconductance amplifiers) from the circuit. By directly using voltage signals to control the current, the patent removes the source of signal distortion and open-loop instability while maintaining the ability to operate at duty cycles greater than 50%.
Solution Approach 2:
The patent introduces a current mirror circuit as an intermediary mechanism to generate the inductor current signal and slope compensation ramp signal directly from voltage signals without requiring voltage-to-current transfer structures. This mediator enables accurate signal generation while avoiding the distortion problems of conventional approaches.
2Power
If conventional voltage-to-current transfer structures are used, then the circuit can generate required current signals, but noise sensitivity increases and response speed decreases
Solution Approach 1:
The patent removes the noisy voltage-to-current transfer structures from the signal path. By using direct voltage control methods with current mirrors, the patent eliminates the noise sensitivity associated with resistors and transconductance amplifiers while maintaining full signal generation capability.
3Power
If voltage-to-current transfer structures are employed, then current signals can be generated, but device complexity increases due to additional components
Solution Approach 1:
The patent extracts and eliminates unnecessary voltage-to-current transfer components (resistors, transconductance amplifiers) from the circuit. The signal generation function is achieved more efficiently using direct voltage control and current mirror techniques, reducing the total component count while maintaining functionality.
Solution Approach 2:
The patent makes the voltage control signals serve multiple functions simultaneously - controlling the main power switch, generating inductor current signals, and providing slope compensation. This multi-functionality eliminates the need for separate voltage-to-current transfer structures for each signal path.
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 signal distortion, enhances response speed, and eliminates open-loop instability, providing a more accurate and stable feedback signal for adjusting DC output voltage.
Implementation Method 1
a current flows through the boost inductor L forward, such that the voltage on the boost inductor L increases. However, the current does not flow through the boost inductor L in an instant, but increases linearly and forms an electromagnetic field
Implementation Method 2
When the MOS transistor T is turned on, the output current is provided by the output capacitor C2 only
Data Source
AI summary
A feedback signal sensing method includes the steps of: providing a pulse width modulation (PWM) signal having a period; charging a capacitor by a current source during a pulse duration of the period, so as to form an equivalent slope compensation ramp signal; conducting an inductor current flowing from a boost inductor to flow through an equivalent resistor during the pulse duration of the period, so as to form an equivalent inductor current signal; and using a coupling characteristic of the capacitor together with the equivalent slope compensation ramp signal and the equivalent inductor current signal to form a feedback signal.