Power Circuit Desaturation and Charge Pump Design
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Solution Overview
Problem
Conventional power circuits face parasitic effects, such as negative voltage spikes at the switch node, which interfere with the boost voltage during charging of the boost capacitor, necessitating the elimination of these effects to ensure proper operation of the power transistor.
Innovation Solution
A power circuit design incorporating a high-side transistor, low-side transistor, charge pump, pre-driver, and desaturation circuit, along with hysteresis circuits and unidirectional conducting devices, to generate a high-side voltage exceeding the supply voltage and detect over-current conditions, thereby managing power current and eliminating parasitic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a charge pump is used to boost supply voltage to drive the power transistor, then the power transistor can be fully turned on, but parasitic effects such as negative voltage spikes at the switch node interfere with the boost voltage
Solution Approach 1:
The patent extracts and removes the parasitic effects from the system by using a desaturation circuit that detects and eliminates negative voltage spikes at the switch node. The circuit separates the harmful parasitic voltage components from the useful boost voltage, allowing the charge pump to maintain clean boosted voltage for driving the power transistor.
Solution Approach 2:
The patent introduces a desaturation circuit as an intermediary between the charge pump and the power transistor. This intermediary circuit detects parasitic effects through saturation voltage monitoring and actively compensates for them, preventing the negative voltage spikes from interfering with the boost voltage while maintaining the driving capability.
2Use of energy by moving object
If the boost capacitor is charged through the power transistor, then the supply voltage is boosted, but the inductor induces significant parasitic effects at the switch node
Solution Approach 1:
The patent implements a feedback mechanism through the desaturation circuit that continuously monitors the saturation voltage at the switch node. When parasitic effects cause the voltage to drop below a threshold, the feedback loop activates compensation transistors to counteract the negative voltage spikes, maintaining stable voltage boosting efficiency while eliminating harmful parasitic effects.
3Device complexity
If conventional driving circuit is used, then the circuit structure is simple, but the parasitic effects cannot be eliminated and interfere with operation
Solution Approach 1:
The patent applies preliminary action by proactively detecting and compensating for parasitic effects before they can significantly interfere with the power transistor operation. The desaturation circuit is designed to detect saturation voltage changes in advance and activate compensation mechanisms preemptively, ensuring reliable operation while maintaining relatively simple circuit structure.
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 eliminates parasitic effects, improves driving capability, and ensures the power transistor operates efficiently by generating a high-side voltage and managing over-current conditions, thus enhancing the overall performance of the power circuit.
Implementation Method 1
The charge pump, which is coupled to the high-side node and the driving node, is configured to generate the high-side voltage that exceeds the supply voltage
Implementation Method 2
The low-pass filter filters out a ripple at the first desaturation node to generate a detection voltage at a detection node
Implementation Method 3
The first hysteresis circuit, which is coupled between the control signal and the pre-driver, receives the control signal to generate a second internal signal
Data Source
AI summary
A power circuit includes a power transistor and a driving circuit. The power transistor draws a power current from a loading node according to a voltage of a driving node and stops drawing the power current according to an over-current signal. The driving circuit includes a high-side transistor, a low-side transistor, a charge pump, a pre-driver, and a desaturation circuit. The high-side transistor provides a supply voltage to the driving node according to a high-side voltage of a high-side node. The low-side transistor couples the driving node to the ground according to a first internal signal. The charge pump generates a high-side voltage that exceeds the supply voltage according to the first internal signal. The pre-driver generates the first internal signal according to a control signal. The desaturation circuit determines that the power current exceeds a threshold to generate the over-current signal.