Self-Driven Synchronous Rectification Circuit Using Charge Pump
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Solution Overview
Problem
The existing synchronous rectification technologies face complexity and high costs due to the need for complex gate control of rectification MOSFETs in PWM mode, requiring external power supplies and slow charging speeds, which hinders their widespread application.
Innovation Solution
A synchronous rectification circuit utilizing a low-voltage charge pump module combined with a Boost module, eliminating the need for an external power supply and accelerating capacitor charging, while reducing the duty ratio and average conduction voltage drop through logic control modules and a self-driving mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If PWM mode is used for rectification MOSFET control, then rectification efficiency is improved, but circuit complexity and implementation difficulty increase
Solution Approach 1:
The charge pump circuit is driven automatically by the rectification MOSFET's own switching actions. The body diode of the MOSFET charges the pump capacitor during off-state, and this charged capacitor automatically drives the MOSFET gate during on-state, eliminating the need for external PWM control circuits.
Solution Approach 2:
A pump capacitor is introduced as an intermediary energy storage element between the rectification MOSFET and its gate control. This capacitor transfers energy from the MOSFET's body diode to its gate, enabling self-driven switching without complex external control circuits.
2Ease of operation
If external power supply driving mode is applied, then gate control capability is improved, but circuit complexity increases
Solution Approach 1:
The rectification MOSFET itself serves as the power source for its own gate control through its body diode. The MOSFET's switching actions automatically charge the pump capacitor, which then provides the necessary gate drive voltage, eliminating dependency on external power supplies.
Solution Approach 2:
The external power supply component is extracted and removed from the system. The gate control function is achieved using only the rectification MOSFET's inherent characteristics and the pump capacitor, simplifying the overall circuit.
3Device complexity
If independent charge pump self-driving mode is used, then circuit complexity is reduced, but charging speed becomes slow
Solution Approach 1:
The pump capacitor is designed with optimized capacitance value and the body diode is selected with low forward voltage drop characteristics. These parameter optimizations enable the charge pump to achieve fast charging speed while maintaining the simple self-driven circuit structure.
Solution Approach 2:
The body diode's forward voltage drop, which is typically considered a loss, is converted into a useful charging mechanism for the pump capacitor. This natural voltage drop during MOSFET off-state automatically charges the capacitor without requiring additional active switching or complex control.
4Device complexity
If simple charge pump mode is applied, then circuit complexity is reduced, but power consumption increases
Solution Approach 1:
The charge pump circuit extracts and utilizes the energy that would otherwise be lost through the body diode's forward voltage drop. By recycling this energy to drive the MOSFET gate, the system reduces overall power consumption while maintaining simple circuit architecture.
Solution Approach 2:
The energy dissipation through the body diode is converted into useful gate drive energy. The forward voltage drop during off-state becomes the charging mechanism for the pump capacitor, transforming what was previously wasted energy into a beneficial resource for reducing total power consumption.
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 simplifies the application complexity, reduces power consumption, and expands the application range of synchronous rectification by eliminating the need for external power supplies and enhancing charging speed.
Implementation Method 1
a low voltage charge pump module, a Boost module... the charge pump has its input connected to the oscillator
Implementation Method 2
the Boost module is composed of a first logic control module, a second logic control module, a first voltage detection module, a second voltage detection module, a PWM generation module, a reference voltage generation module, a switch PM1, a free-wheeling MOSFET NM2, an isolation MOSFET NM1, an inductor L and sampling resistors R1 and R2
Implementation Method 3
the sampling resistors R1 and R2 are connected in series, a common connection end of the sampling resistors R1 and R2 is connected to an input of the PWM generation module, the other end of the sampling resistor R1 is connected to the input of the first voltage detection module and the upper plate of the external capacitor C, the other end of the sampling resistor R2 is connected to the lower plate of the external capacitor C
Data Source
AI summary
Provided is a synchronous rectification circuit, which relates to electronic circuit technologies. The synchronous rectification circuit is self-driven by a combination of a charge pump and a Boost circuit, including a rectification MOSFET, a charge pump, logic control modules, voltage detection modules, an oscillator module, a PWM generation module, a reference voltage generation module, a switch, a free-wheeling MOSFET, an isolation MOSFET, an inductor, a capacitor and sampling resistors. According to the present application, initially, the charge is stored on the capacitor through the charge pump, the Boost circuit is turned on till the voltage is increased to a certain value; through processing by the logic control modules and the like, the rectification MOSFET is turned on, thus self-driving of the synchronous rectification circuit is achieved. The self-driving mode can charge the capacitor faster, lower the duty of the rectification circuit, and reduce the average conduction voltage drop.