MOSFET Full-Bridge Rectifier for Battery Charging
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Solution Overview
Problem
In battery-charging devices using a full-bridge, full-wave rectifier circuit with MOSFETs, there is a challenge in quickly restarting the ON/OFF control of MOSFETs after short-circuit control is ended, leading to excessive heat generation and power loss due to current flowing through parasitic diodes during the transition from short-circuit to charging control, especially when battery voltage fluctuations occur frequently.
Innovation Solution
The solution involves a battery-charging device with a full-bridge rectifier circuit using MOSFETs, where a FET OFF time period is generated in a set cycle during short-circuit control, allowing detection of input terminal polarity and enabling quick restart of charging control, and a sampling timing generation means to stabilize control decisions, preventing oscillatory states and overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If short-circuit control is used to stop charging when battery voltage is high, then overcharging is prevented, but the MOSFET ON/OFF control cannot be quickly restarted after short-circuit control ends, causing excessive heat generation and power loss
Solution Approach 1:
The control unit stores polarity information detected during short-circuit control in a storage unit. This preliminary action ensures that when short-circuit control ends, the MOSFETs can be immediately restarted with correct polarity information, avoiding the delay that causes excessive power loss and heat generation in the rectifier circuit.
Solution Approach 2:
A storage unit is introduced as an intermediary component between the polarity detection circuit and the MOSFET control logic. This storage unit retains polarity information during short-circuit control, enabling seamless transition and quick restart of MOSFET control without loss of critical information, thereby reducing energy loss.
2Loss of energy
If MOSFETs are controlled to reduce power loss during rectification, then efficiency is improved, but frequent battery voltage fluctuations can cause oscillatory states and instability in control decisions
Solution Approach 1:
The control unit continuously monitors battery voltage and uses feedback control to adjust MOSFET operation. When voltage fluctuations are detected, the system responds by adjusting the charging control state, preventing oscillatory conditions while maintaining efficient power transfer and stable operation.
3Ease of manufacture
If a diode-bridge full-wave rectifier circuit is used to rectify generator output, then simple implementation is achieved, but appreciable power loss occurs in the diodes and temperature increases
Solution Approach 1:
The patent replaces the passive diode-bridge rectifier with an active MOSFET-based rectifier circuit controlled by a control unit. This substitution eliminates the fixed forward voltage drop of diodes, reducing power loss and heat generation while maintaining full-wave rectification functionality. The MOSFETs are controlled to conduct during appropriate half-cycles, achieving efficient 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 approach reduces power loss and heat generation in the rectifier circuit, prevents overcharging, and allows for efficient battery charging by ensuring accurate ON/OFF state establishment and control of MOSFETs, even during frequent battery voltage fluctuations.
Implementation Method 1
a full-bridge rectifier circuit in which each of upper arms and lower arms of a bridge circuit is configured from a MOSFET and has input terminals to which an output of the generator is inputted
Implementation Method 2
there will be appreciable power loss when the output of the generator is rectified... current flows in a forward direction
Data Source
AI summary
Provided is a battery-charging device that uses a full-bridge rectifier circuit in which each arm is composed of MOSFET as a circuit that rectifies an output of a magnet-type AC generator. The charging device comprises: an ON/OFF state establishment means that, on the basis of a polarity of a potential of each input terminal of the rectifier circuit, establishes ON/OFF state to be assumed by each MOSFET of the rectifier circuit when a battery is charged; a during-charging FET control means that performs control which matches the state of each MOSFET of the rectifier circuit with the state established by the ON/OFF state establishment means when the battery is charged; a short-circuit control means that performs short-circuit control which causes short-circuiting between output terminals of the generator when battery charging is paused; and a FET OFF means that generates a FET OFF time period in which all of the MOSFETs of the rectifier circuit assume an OFF state in a fixed cycle. While short-circuit control is being performed as well, information for establishing the states to be assumed by the MOSFETs of the rectifier circuit during battery charging can be obtained during the FET OFF time periods.