MOSFET Ideal Diode Circuit for High-Temperature Low-Current Startup
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Solution Overview
Problem
Conventional ideal diode circuits face challenges in high temperature and low current conditions, where the forward body diode voltage of MOSFET is small, and the charge pump's pumping ability is weak, leading to failure in reaching the upper limit voltage and resulting in the circuit being unable to turn on the MOSFET and operate normally.
Innovation Solution
The proposed ideal diode circuit includes a capacitor unit, a transistor unit, a voltage conversion unit, and a control unit, which outputs driving signals based on the capacitor voltage to control the transistor's conduction and closure, ensuring operation even under extreme conditions. Additionally, a reverse bias cut-off driving unit is included to protect the transistor and capacitor units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional hysteresis comparator scheme is used to determine capacitor voltage limits, then the control logic is simple, but the design becomes complicated and fails under high temperature and low current conditions
Solution Approach 1:
The patent changes the control parameter from voltage threshold comparison (hysteresis comparator) to time-based control. The microcontroller measures capacitor voltage and controls MOSFET switching based on time intervals, allowing adaptation to varying temperature and current conditions while maintaining simple overall system architecture.
Solution Approach 2:
The patent replaces the analog hysteresis comparator mechanism with a digital control system using a microcontroller. This substitution enables more flexible and reliable control logic that can handle extreme conditions while actually reducing design complexity through standardized digital components.
2Temperature
If the charge pump operates under high temperature and low current conditions, then the forward body diode voltage is small, but the pumping ability becomes weak and cannot reach the upper limit voltage
Solution Approach 1:
The patent implements feedback control where the microcontroller continuously measures the capacitor voltage and adjusts the MOSFET switching timing accordingly. This feedback mechanism ensures the charge pump reaches the desired upper limit voltage even under high temperature and low current conditions by dynamically optimizing the pumping cycle.
Solution Approach 2:
The patent uses periodic switching control of the MOSFET based on measured time intervals. By controlling the charge pump to operate in periodic cycles with optimized duration, the system maintains effective voltage pumping capability under extreme temperature conditions where continuous operation would be ineffective.
3Reliability
If the hysteresis comparator clock cannot reach the flip condition, then the ideal diode circuit cannot turn on the MOSFET, but the voltage drop across the MOSFET remains high
Solution Approach 1:
The patent performs preliminary voltage measurement and time interval calculation before MOSFET switching. The microcontroller measures the capacitor voltage and pre-determines the optimal switching timing, ensuring the MOSFET is turned on at the precise moment needed to minimize voltage drop and maximize efficiency, rather than relying on comparator flip conditions.
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 enables the ideal diode circuit to operate reliably under high temperature and low current conditions by periodically controlling the transistor's conduction and closure, and triggering capacitor charging without waiting for an accurate set voltage upper limit, thus enhancing reliability.
Implementation Method 1
a voltage conversion unit electrically connected to the capacitor unit and the transistor unit respectively, and configured to charge the capacitor unit via a parasitic diode in the transistor unit
Data Source
Figure 1~2
Figure 3~4
AI summary
An ideal diode circuit comprises a capacitor unit and a transistor unit electrically connected thereto, a voltage conversion unit electrically connected to the capacitor unit and the transistor unit respectively and configured to charge the capacitor unit via a parasitic diode in the transistor unit, a control unit, whose the input end electrically connected to the capacitor unit, whose the output end electrically connected to the control end of the transistor unit, configured to output a first driving signal or a second driving signal based on the voltage signal of the capacitor unit, drive the transistor unit to turn off under the first driving signal, or drive the transistor to turn on under the second driving signal, and a reverse bias cut-off driving unit configured to drive the transistor unit to turn off in a case where voltage at two ends of the transistor unit is reversed.