Half Bridge Driver Filter Circuit for Pulse Width Distortion
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Solution Overview
Problem
Traditional RC filter circuits in high voltage half-bridge driver systems cause pulse width distortion, leading to shoot-through currents and missed PWM cycles due to their inability to handle minimum pulse width signals effectively.
Innovation Solution
A filter circuit with diodes D1 and D2 is introduced across the amplifier, preventing signals with pulse widths shorter than the minimum from propagating by ensuring the capacitor charges towards VDD and discharges accordingly, maintaining the output pulse width without distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional RC filter is used in the high voltage half-bridge driver, then signal filtering is achieved, but pulse width distortion occurs when the input signal pulse width is near the RC time constant
Solution Approach 1:
The patent introduces diodes D1 and D2 as intermediary elements between the RC filter and the amplifier. These diodes act as mediators that prevent the capacitor from discharging during the input pulse, thereby eliminating pulse width distortion while maintaining the signal filtering function of the RC circuit.
Solution Approach 2:
The diodes D1 and D2 are configured to preemptively prevent the capacitor discharge that would cause pulse width distortion. By establishing this protective mechanism before the distortion can occur, the circuit maintains accurate pulse width transmission even when the input signal pulse width is near the RC time constant.
2Duration of action of moving object
If the RC filter time constant is reduced to handle shorter pulses, then minimum pulse width handling is improved, but signal filtering effectiveness decreases
Solution Approach 1:
The diodes serve as intermediaries that decouple the capacitor discharge behavior from the input signal pulse width. This allows the RC time constant to be optimized for signal filtering without being constrained by the minimum pulse width requirement, as the diodes prevent the capacitor from discharging during the pulse.
Solution Approach 2:
The circuit dynamically adapts its behavior based on the input signal state. When the input pulse is present, the diodes conduct and prevent capacitor discharge. When the input pulse is absent, the capacitor can discharge normally through the resistor, maintaining filtering effectiveness for continuous signals while preserving minimum pulse width handling capability.
3Device complexity
If pulse width distortion is allowed to pass to the half bridge stage, then circuit simplicity is maintained, but shoot-through currents and missed PWM cycles occur
Solution Approach 1:
The diodes D1 and D2 are inserted as intermediary protective elements between the filter and the amplifier stage. These diodes specifically prevent the harmful capacitor discharge effect that causes pulse width distortion, while minimally impacting the overall circuit simplicity and adding only minimal complexity to achieve shoot-through prevention.
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 prevents pulse width distortion and shoot-through currents, ensuring accurate signal propagation and maintaining PWM cycles even with input signals near the RC time constant, thus enhancing the reliability of high voltage half-bridge driver systems.
Implementation Method 1
A capacitor C is coupled across the amplifier 24 between input and output
Implementation Method 2
two diodes D1 and D2 are series coupled at a node N between the resistor R and the amplifier 24
Data Source
AI summary
A driver integrated circuit for driving at least one high voltage half bridge stage. The driver including a filter circuit for filtering a signal provided to the half bridge stage, a minimum pulse width of the signal being near a constant time of the filter, wherein the filter circuit prevents distortions introduced when the signal is at its minimum pulse width from being passed to the half bridge stage.