Asynchronous Switch Power Supply With MOSFET Diode Replacement
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Solution Overview
Problem
Switch power supply circuits, particularly asynchronous boost and buck circuits, suffer from high power loss and low efficiency due to the use of diodes, which result in increased costs and complex circuit designs when trying to control switch transistors with PWM controllers.
Innovation Solution
The implementation of a switch power supply circuit that replaces diodes with low-voltage-drop switch transistors and uses discrete component-based control circuits to manage the on/off states of these transistors, eliminating the need for additional PWM controllers and reducing hardware costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a diode is used in an asynchronous boost switch power supply circuit, then the circuit structure is simple, but the turn-on voltage drop is large causing high power loss and low efficiency
Solution Approach 1:
The patent changes the key parameter from diode turn-on voltage (typically 0.7V) to MOSFET on-resistance (Rds(on)), which can be optimized to be much lower. By selecting MOSFETs with appropriate Rds(on) values and optimizing the switching control, the voltage drop during conduction is significantly reduced, thereby reducing power loss while maintaining reasonable circuit complexity
Solution Approach 2:
The patent uses a second MOSFET to replace the diode function, creating a synchronous rectification path that mirrors the main switching path. This 'copy' of the low-loss switching mechanism (using MOSFET instead of diode) in the rectification path achieves similarly low voltage drop and power loss characteristics
2Manufacturing precision
If a PWM controller is used to control the switch transistor, then the switching control is precise, but the hardware cost and circuit design complexity increase
Solution Approach 1:
The patent enables the circuit to control its own switching operation through inherent feedback mechanisms. The control circuit monitors the output voltage and automatically adjusts the switching duty cycle without requiring an external PWM controller, making the system self-regulating and reducing hardware complexity while maintaining adequate control precision
Solution Approach 2:
The patent extracts and removes the PWM controller component from the circuit, eliminating the need for complex external control hardware. The switching control function is integrated into simpler control circuitry that works in conjunction with the MOSFETs, reducing overall circuit complexity while maintaining functional effectiveness
3Loss of energy
If a second switch transistor is used to replace the diode, then the power loss is reduced, but additional control circuitry is needed
Solution Approach 1:
The patent merges the control functions for both MOSFETs into a single integrated control circuit that generates complementary gate drive signals. This unified control approach coordinates the switching of Q1 and Q2 simultaneously, reducing the need for separate control circuits while achieving the low power loss benefits of synchronous rectification
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 solution significantly reduces power loss and improves efficiency by utilizing switch transistors with low turn-on voltage drops, while simplifying circuit designs and lowering hardware costs through the use of discrete component control circuits.
Implementation Method 1
one end of the first inductor is connected to a positive input end of the boost switch power supply circuit, and the other end of the first inductor is connected to a first end of the first switch transistor
Implementation Method 2
the output capacitor is connected in parallel between the positive output end and the ground end
Data Source
AI summary
This application provides a switch power supply circuit and a terminal device, and the switch power supply circuit uses a second switch transistor to replace a diode in an asynchronous switch power supply circuit. A turn-on impedance of the switch transistor is very small, only tens of milliohms, so that a turn-on voltage drop in the switch power supply circuit is reduced from hundreds of millivolts to tens of millivolts, power loss of the switch power supply circuit is greatly reduced, and output efficiency is improved. Moreover, this solution uses a discrete component to form a control circuit to control a switch status of the second switch transistor without additionally setting a pulse width modulation (PWM) controller, and costs of the discrete component are far lower than costs of the PWM controller, reducing hardware costs of a switch power supply and simplifying a circuit design.