Error Amplifier Gain Control for Power Supply Phase Compensation
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Solution Overview
Problem
Conventional switching power supply devices require high-cost and large elements for phase compensation in feedback control, leading to increased cost and device size.
Innovation Solution
A power supply device with a structure that includes an output transistor, a reference voltage generation circuit, an error amplifier, an oscillator, and a comparator, where the error amplifier has an input stage and an output stage with a boost circuit that changes impedance based on the frequency of an electric-current signal, and a current mirror, using a resistor and capacitor in parallel for the boost circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-cost and large elements (inductor, output capacitor, resistor, capacitor) are used for phase compensation in feedback control, then suitable phase compensation is achieved and output voltage stability is maintained, but device cost and size increase
Solution Approach 1:
The patent changes the impedance parameter of the error amplifier dynamically by introducing a boost circuit that varies its impedance based on the frequency of the electric-current signal. This allows the system to achieve suitable phase compensation across different operating conditions without requiring large, fixed-value passive components. The boost circuit modifies the gain characteristics of the error amplifier to maintain stability while using smaller external components.
Solution Approach 2:
The patent replaces the conventional approach of using large physical passive components (inductors, capacitors, resistors) for phase compensation with an active electronic circuit (boost circuit) that achieves the same phase compensation function through electronic impedance transformation. This substitution eliminates the need for large external passive components while maintaining the required phase margins for stability.
2Reliability
If conventional phase compensation methods are used with external passive components, then feedback control stability is achieved, but manufacturing cost increases
Solution Approach 1:
The patent merges the phase compensation function with the error amplifier by integrating a boost circuit within the error amplifier structure. This consolidation eliminates the need for separate external passive components that would be required for phase compensation in conventional designs, thereby reducing component count, assembly complexity, and manufacturing cost while maintaining feedback control stability.
Solution Approach 2:
The boost circuit within the error amplifier generates the necessary impedance transformation and phase compensation internally using the available feedback voltage and reference voltage signals. The circuit serves itself by utilizing the existing signal paths and power supply within the integrated circuit, eliminating the need for external passive components and reducing manufacturing cost.
Data Source
AI summary
A power supply device is provided with an output transistor for outputting a switch voltage having a rectangular waveform, based on an input signal by being switching-controlled by a pulse width modulation signal; a reference voltage generating circuit for generating a prescribed reference voltage; an error amplifier wherein a feedback voltage depending on the switch voltage and the reference voltage are inputted, an error voltage is generated by amplifying a difference between the voltages, and changes a gain of itself, in accordance with a current signal generated inside based on the feedback voltage and the reference voltage; an oscillator for generating an oscillation signal; and a comparator wherein the oscillation signal and the error voltages are inputted and the pulse width modulation signal is outputted by comparing the voltages.