Buck Constant-Voltage Driver With Load-Current Voltage Compensation
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Solution Overview
Problem
Buck constant voltage drivers experience significant output voltage deviations due to changes in load current, primarily caused by variations in the forward voltage drop of diodes, which is unacceptable for applications requiring accurate voltage regulation.
Innovation Solution
Incorporating an output voltage compensation module that acquires output current information through a sampling resistor and compensates a preset reference voltage, maintaining the output voltage constant across different load currents by using a peak sampling circuit, superposition coefficient circuit, and adding circuit to adjust the reference voltage accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional Buck constant voltage driver is used with simple structure, then the device complexity is low and cost is reduced, but the output voltage deviation under different load currents increases significantly
Solution Approach 1:
The patent implements a feedback mechanism by sampling the output current through a sampling resistor and feeding back the sampled signal to a compensation module. This feedback loop enables the system to detect output current changes and automatically adjust the reference voltage to compensate for diode forward voltage variations, thereby maintaining stable output voltage across different load conditions without significantly increasing device complexity
Solution Approach 2:
The patent dynamically changes the reference voltage parameter based on output current conditions. The compensation module adjusts the reference voltage upward when output current increases (to compensate for increased diode forward voltage drop) and downward when output current decreases. This parameter change strategy directly addresses the voltage deviation issue while maintaining a relatively simple overall structure
2Adaptability or versatility
If the load current changes, then the diode forward voltage drop varies significantly, but the output voltage should remain constant
Solution Approach 1:
The compensation module continuously monitors output current through the sampling resistor and uses this feedback information to adjust the reference voltage. When load current increases causing diode forward voltage drop to increase, the feedback signal triggers an increase in reference voltage, compensating for the voltage loss and maintaining constant output voltage
Solution Approach 2:
The system takes preliminary anti-action by proactively adjusting the reference voltage in anticipation of output voltage deviation. The compensation module predicts the voltage drop based on sampled current and adjusts the reference voltage beforehand to counteract the expected deviation, preventing output voltage instability before it occurs
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
The solution effectively maintains the output voltage constant, reducing deviations from 5% in the prior art to approximately 1%, thereby improving the stability and accuracy of voltage regulation.
Implementation Method 1
an input terminal of the output voltage compensation module is connected between the sampling resistor and the power tube to acquire a sampling voltage on the sampling resistor
Implementation Method 2
the forward voltage drop VD1 has a large deviation while the forward voltage drop VD2 is approximately unchanged, under different load currents
Data Source
AI summary
A Buck constant voltage driver and an application circuit thereof, are disclosed. In the Buck constant voltage driver, the peripheral structure is remained unchanged for possessing the advantages of low cost and simplicity of the prior art. Meanwhile, in order to compensate the difference of output voltage caused by the change of the forward voltage drop under different output currents, an output voltage compensation module is added to the Buck constant voltage driver. The output voltage compensation module is operable to acquire an output current information based on the sampling voltage on the sampling resistor, and to compensate the preset first reference voltage according to the output current information, thus maintaining the output voltage of the Buck constant voltage driver constant, under different output current conditions.