Parallel MOSFET Switching Power Supply Standby Loss Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional switching power supplies face significant switching loss and high power consumption during standby mode due to the output capacitance and gate charge of high-power FETs, which is challenging to reduce effectively using existing frequency reduction and burst switching control schemes.
Innovation Solution
A switching power supply configuration that includes a main high-power capacity MOSFET and a secondary low-power capacity MOSFET connected in parallel, where the secondary MOSFET is used only during standby mode, reducing switching frequency and using a burst switching scheme to minimize power consumption and switching loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high-power capacity MOSFET is used as the switching element to satisfy the power capacity rating, then the power supply can provide rated power capacity, but switching loss increases during standby mode due to output capacitance and gate charge
Solution Approach 1:
The patent divides the switching element into two separate MOSFETs: a main switching element for normal operation and a secondary switching element for standby mode. This segmentation allows each MOSFET to be optimized for its specific operating condition, with the secondary MOSFET having lower output capacitance and gate charge to reduce switching loss during standby.
Solution Approach 2:
The patent dynamically switches between different MOSFETs based on operating mode. The control circuit activates the secondary switching element during standby mode when power consumption needs to be minimized, and switches to the main switching element during normal operation to provide full power capacity.
2Use of energy by stationary object
If frequency reduction control or burst switching control is applied during standby mode, then power consumption decreases, but switching loss cannot be reduced effectively due to the inherent output capacitance and gate charge of high-power FETs
Solution Approach 1:
The patent uses a secondary MOSFET specifically designed for standby mode operation that is optimized for low switching loss. This secondary element is activated only when needed (during standby mode) and has different characteristics (lower output capacitance and gate charge) compared to the main power MOSFET.
3Loss of energy
If the switching frequency is reduced during standby mode, then switching loss decreases, but the output capacitance and gate charge of high-power FETs still cause significant power consumption
Solution Approach 1:
The patent applies different quality characteristics to different switching elements based on their operating conditions. The secondary MOSFET used during standby mode has lower output capacitance and gate charge, making it locally optimized for low-power operation, while the main MOSFET maintains high power capacity for normal operation.
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 configuration significantly reduces switching loss and power consumption in standby mode by utilizing a MOSFET with lower output capacitance and gate charge, achieving power consumption less than 2 mW, while maintaining stable output voltage during normal operation.
Implementation Method 1
a main switching element Q-m that is attached to a primary coil Ta of a transformer T... a secondary switching element Q-s connected in parallel to the main switching element Q-m... a rectifying circuit that rectifies an alternating voltage induced in a secondary coil Tb of the transformer T
Implementation Method 2
a diode bridge circuit DB that full-wave rectifies AC power supplied from a commercial 100V or 220V AC power source
Implementation Method 3
an output capacitor Cout that smooths the rectified output from the diode D
Implementation Method 4
an input capacitor Cin that smooths the output from the diode bridge circuit DB
Data Source
AI summary
A switching power supply includes a main switching element that is connected to a primary coil of a transformer and switches a main current ON/OFF, and a secondary switching element connected in parallel to the main switching element and that has a lower power capacity than the main switching element. The switching power supply also includes a control circuit that controls these switching elements. The control circuit includes: a main driver circuit that generates, in accordance with a control signal generated according to an output voltage from a secondary coil of the transformer, a main drive signal for switching the main switching element ON/OFF; a secondary driver circuit that generates a secondary drive signal for switching the secondary switching element ON/OFF according to the control signal; and an enable control circuit that deactivates the main driver circuit when a power consumption of a load is less than a threshold value.