DC-DC Converter Reverse Current Detection Circuit
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Solution Overview
Problem
Existing DC-DC converters face inefficiencies due to reverse current issues at light loads, leading to reduced power efficiency and increased circuit operation rates, which worsen power consumption and output voltage stability.
Innovation Solution
A DC-DC converter design incorporating a control circuit with a pulse signal generating circuit, minimum pulse width limiting circuit, selector, driver circuit, and reverse current detecting circuit to adjust switching element on periods and prevent reverse currents, optimizing pulse widths based on load current to enhance power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the on period of the first switching element is shortened to reduce circuit operation rate at light loads, then power efficiency is improved, but output voltage stability deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the on period of the first switching element based on load conditions. At light loads, the on period is shortened to reduce switching frequency and improve power efficiency. At heavy loads, the on period is extended to maintain adequate voltage output and stability. This dynamic parameter adjustment resolves the contradiction between power efficiency and output voltage stability across different operating conditions.
2Loss of energy
If PWM control is used to switch main transistor and synchronous rectifying transistor, then power conversion efficiency is improved, but reverse current occurs at light loads
Solution Approach 1:
The patent introduces a second switching element as an intermediary component between the synchronous rectifying transistor and ground. This second switching element acts as a mediator to block reverse current flow from the output node back through the synchronous rectifying transistor to ground. By adding this intermediary switching element controlled by the control circuit, the system maintains PWM control efficiency while preventing the harmful reverse current effect at light loads.
3Stability of the object's composition
If the synchronous rectifying transistor is kept on to maintain output voltage, then output voltage stability is improved, but reverse current increases and power efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the on/off state of the synchronous rectifying transistor dynamic rather than static. The control circuit dynamically controls the synchronous rectifying transistor to be turned off during specific periods when reverse current would occur (particularly at light loads), while the second switching element dynamically adjusts to maintain the necessary current path. This dynamic control strategy allows the system to maintain output voltage stability only when necessary while preventing reverse current and improving power efficiency at other times.
Data Source
AI summary
A DC-DC converter includes a first switching element and a second switching element; a pulse signal generating circuit which generates a pulse signal used to control on/off periods of the switching elements; a limiting circuit which generates a minimum pulse width signal; a selector configured to select one of the pulse signal and the minimum pulse width signal, and a driver circuit switches the first and second switching element and a reverse current detecting circuit detects a reverse current. The driver circuit controls the first or second switching element, when the reverse current is detected. The selector selects the pulse signal when the reverse current is not detected, and selects the minimum pulse width signal when the reverse current is detected.