Power Supply Soft Start Circuit Using Field-Effect Transistor
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Solution Overview
Problem
Conventional power supply circuits for electronic products, such as LCDs, have complex soft start circuits with bipolar junction transistors, leading to high power consumption and electric noise, which negatively impact reliability.
Innovation Solution
A power supply circuit utilizing a field-effect transistor with a simple configuration, eliminating the need for a separate DC power supply, where the field-effect transistor controls the charging and discharging of a capacitor to manage the soft start function, reducing power consumption and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bipolar junction transistors are used in the soft start circuit, then the soft start function is achieved, but the circuit complexity increases and power consumption rises
Solution Approach 1:
The patent replaces bipolar junction transistors (current-controlled devices) with field-effect transistors (voltage-controlled devices). This substitution changes the control mechanism from current-based to voltage-based, eliminating the need for bias resistors and DC power supply, thereby simplifying the circuit configuration while maintaining the soft start function.
Solution Approach 2:
The patent extracts and removes unnecessary components from the conventional soft start circuit. By using field-effect transistors, the bias resistors and separate DC power supply are eliminated, leaving only the essential soft start capacitor and the field-effect transistor itself, thus reducing circuit complexity.
2Reliability
If bipolar junction transistors are used in the soft start circuit, then the soft start function is achieved, but power consumption increases
Solution Approach 1:
The patent replaces bipolar junction transistors (current-controlled devices requiring continuous bias current) with field-effect transistors (voltage-controlled devices with high input impedance). This substitution eliminates the continuous bias current requirement, significantly reducing power consumption while maintaining the soft start function.
Solution Approach 2:
The field-effect transistor's gate electrode has very high input impedance, meaning it draws negligible current to maintain the voltage control function. The soft start capacitor charges and discharges through the inherent circuit paths without requiring additional bias power, making the circuit self-sufficient and low-power.
3Reliability
If bipolar junction transistors are used in the soft start circuit, then the soft start function is achieved, but electric noise increases
Solution Approach 1:
The patent replaces bipolar junction transistors with field-effect transistors. Field-effect transistors generate less electric noise because they are voltage-controlled devices with insulated gates, eliminating the noise associated with base current switching and bias resistor networks in bipolar junction transistors.
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 solution results in a power supply circuit with lower power consumption, reduced signal noise, and enhanced reliability by using a voltage-controlled field-effect transistor to manage the soft start process, simplifying the circuit configuration.
Implementation Method 1
The field-effect transistor includes a gate electrode, a source electrode, and a drain electrode. The gate electrode is connected to the output port of the scaler. The source electrode is grounded. The drain electrode is connected to the input port of the pulse width modulation circuit.
Data Source
AI summary
An exemplary power supply circuit (20) includes a scaler (21), a field-effect transistor (23), a pulse width modulation circuit (25), and a capacitor (29). The scaler includes an output port (213). The pulse width modulation circuit includes an input port (251). The input port of the pulse width modulation circuit is grounded via the capacitor. The field-effect transistor includes a gate electrode (231), a source electrode (232), and a drain electrode (233). The gate electrode is connected to the output port of the scaler. The source electrode is grounded. The drain electrode is connected to the input port of the pulse width modulation circuit.