Power Switch Circuit Current Sensing Accuracy
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Solution Overview
Problem
Conventional current sensing circuits face calibration issues when the output voltage at the load is zero, leading to poor accuracy due to non-zero bias voltage caused by the feedback switch, affecting the stable proportion between output current and sensing current.
Innovation Solution
A power switch circuit with current sensing that includes a power switch, a first sensing switch, an adjusting circuit, and a second sensing switch, where separate control voltages are supplied to the power switch and sensing switches to maintain the sensing switch in the linear region, independent of the current limiting mechanism, thereby improving current sensing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback switch is used to calibrate current sensing error, then current sensing accuracy is improved under normal operating conditions, but calibration effectiveness deteriorates when output voltage is zero due to non-zero bias voltage
Solution Approach 1:
The patent divides the control voltage supply into separate channels: a first control voltage for the power switch and a second control voltage for the sensing switch. This segmentation allows independent optimization of each switch's operating conditions, enabling the sensing switch to maintain proper operation even when the power switch is off or output voltage is zero.
Solution Approach 2:
The patent applies different control voltages to different parts of the circuit: the power switch receives a control voltage optimized for power switching operations, while the sensing switch receives a separate control voltage optimized for linear region operation. This local quality differentiation ensures each component operates in its optimal region under all conditions.
2Device complexity
If the sensing switch shares gate and source with the power switch, then device complexity is reduced, but current sensing accuracy deteriorates due to inability to independently control operating region
Solution Approach 1:
The patent segments the control voltage supply into separate first and second control voltages for the power switch and sensing switch respectively. This segmentation maintains the simplified shared gate and source structure while enabling independent voltage control, thus preserving low device complexity while improving sensing accuracy.
Solution Approach 2:
The patent changes the control parameter from a single shared control voltage to two independent control voltages. This parameter change allows the sensing switch to be maintained in the linear region through appropriate second control voltage selection, improving current sensing accuracy without significantly increasing device complexity.
Data Source
AI summary
A power switch circuit with current sensing is disclosed. The power switch circuit is coupled between an input voltage and an output terminal. The power switch circuit includes a power switch, a first sensing switch, an adjusting circuit and a second sensing switch. The power switch is coupled to the input voltage. The first sensing switch is coupled in series between the power switch and the output terminal. There is a first node between the first sensing switch and the power switch. The adjusting circuit is coupled to the first node. The second sensing switch is coupled between the adjusting circuit and the output terminal. A control terminal of the power switch is coupled to a first control voltage. Control terminals of the first sensing switch and the second sensing switch are coupled to a second control voltage. The second control voltage is different from the first control voltage.