Load Driving Circuit Bootstrap Clamp Voltage Control
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Solution Overview
Problem
Conventional load driving circuits with bootstrap circuits often incorrectly detect a power fault state when the load is in an open state, due to a voltage rise in the clamp circuit caused by the bootstrap circuit's charging current.
Innovation Solution
Incorporating a clamp voltage rise suppressing circuit and adjusting the second reference voltage based on the current flowing from the bootstrap circuit through the capacitor, ensuring the clamp voltage remains within safe limits to prevent false power fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a bootstrap circuit is added to drive a high-side MOSFET, then the switching element can be properly activated, but the charging current from the bootstrap circuit causes the clamp voltage to rise and incorrectly triggers the power fault detection
Solution Approach 1:
The patent introduces a current detection circuit as an intermediary between the bootstrap circuit and the clamp circuit. This intermediary detects the charging current from the bootstrap circuit and generates a compensation signal that prevents the clamp voltage from rising to the faulty level, thereby eliminating the false power fault detection while maintaining proper switching element activation
Solution Approach 2:
The patent dynamically adjusts the reference voltage of the clamp circuit based on the detected bootstrap charging current. By changing the reference voltage parameter in response to the charging current, the system accommodates the temporary voltage rise during bootstrap operation without triggering false power fault detections
2Adaptability or versatility
If the clamp circuit is designed to detect load open state, then load open state detection is enabled, but the clamp circuit cannot distinguish between load open state and power fault state when bootstrap charging current is present
Solution Approach 1:
The current detection circuit serves as an intermediary that provides additional information about the system state. By detecting the bootstrap charging current and providing this information to the control logic, the system can distinguish between a load open state (where no bootstrap charging occurs) and normal operation with bootstrap charging, thereby improving measurement precision
Solution Approach 2:
The patent implements a feedback mechanism where the clamp circuit's detection of voltage levels is combined with feedback from the current detection circuit about bootstrap charging activity. This feedback allows the system to interpret clamp voltage readings in context, distinguishing between legitimate voltage rises during bootstrap operation and actual fault conditions
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
Prevents incorrect power fault state detection by maintaining the clamp voltage below the second reference voltage, accurately distinguishing between load open and power fault states.
Implementation Method 1
a first comparator configured to compare a voltage of the second terminal with a first reference voltage that is lower than an input voltage inputted to the first terminal to detect a load open state
Implementation Method 2
a clamp circuit configured to clamp the voltage of the second terminal to a clamp voltage that is higher than the first reference voltage and lower than the input voltage
Implementation Method 3
a second comparator configured to compare the voltage of the second terminal with a second reference voltage that is lower than the input voltage and higher than the clamp voltage to detect a power fault state
Implementation Method 4
a bootstrap circuit configured to generate a constant voltage based on a voltage of the power supply at the first terminal, and to feed a charging current to the third terminal at the constant voltage
Data Source
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AI summary
A first comparator CP1 compares a voltage of an output terminal OUT with a first reference voltage V1 is lower than a voltage E inputted to a power terminal Vcc to detect a load open state where a switching element Q1 is off and a load 20 is not connected to output terminal. A second comparator CP2 compares voltage of output terminal OUT with a second reference voltage V2 is lower than voltage E and higher than a clamp voltage to detect a power fault state. A clamp circuit 14 clamps voltage of output terminal to a clamp voltage is higher than first reference voltage and lower than voltage E in load open state, a capacitor C1. A bootstrap circuit 10 feeds a charging current to an amp terminal at a constant voltage generated based on voltage of a power supply. A clamp voltage rise suppressing circuit 16 suppresses a rise in clamp voltage of clamp circuit when first comparator detects load open state.