Half-Bridge Current Detection Circuit for Switching Power Supplies
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Solution Overview
Problem
In high-frequency switching power supplies, sensing the inductor current through the high side switch becomes challenging due to the short turn ON time, making it difficult for existing amplifiers to respond adequately for overcurrent protection and other purposes.
Innovation Solution
A current detection circuit that samples and holds the valley and peak of the inductor current using capacitors during the low side switch's turn ON time and generates a representative sense current by combining the charges stored in these capacitors during the turn OFF time, allowing for accurate inductor current sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fast current sensing amplifiers are employed for high side current sensing, then measurement precision is improved, but device complexity increases and response time becomes unattainable at high frequencies
Solution Approach 1:
The patent performs preliminary sampling of the inductor current at specific moments (when low side switch turns ON) using capacitors to hold the current value. This preliminary action during the low side switch ON time allows the system to capture current information in advance, eliminating the need for fast amplifiers during the high side switch ON time and resolving the response time contradiction.
2Duration of action of moving object
If the high side switch turn ON time is extended, then amplifier response time is improved, but switching frequency must be reduced
Solution Approach 1:
The patent introduces capacitors as intermediary elements that sample and hold the inductor current during the low side switch ON time. These capacitors act as mediators, storing current information that can be used during the high side switch ON time, thereby decoupling the amplifier response time requirement from the high side switch duration and enabling high frequency operation.
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 method enables effective inductor current sensing, even at high frequencies, by providing a representative sense current that accurately reflects the inductor current, enhancing overcurrent protection and other monitoring capabilities.
Implementation Method 1
a current detection circuit samples and holds in a capacitor a valley of an inductor current flowing through the output inductor. Also during the turn ON time of the low side switch, the current detection circuit samples and holds in another capacitor a peak of the inductor current
Implementation Method 2
a sense inductor current that is representative of the inductor current is generated by combining the charges stored in the capacitors
Data Source
AI summary
A power supply includes a half-bridge circuit. The power supply further includes an output inductor connected to a switch node that is common to a high side switch and a low side switch of the half-bridge. During a turn ON time of the low side switch, a current detection circuit of the power supply samples and holds in a capacitor a valley of an inductor current flowing through the output inductor. Also during the turn ON time of the low side switch, the current detection circuit samples and holds in another capacitor a peak of the inductor current. During a turn OFF time of the low side switch, a sense inductor current that is representative of the inductor current is generated by combining the charges stored in the capacitors.