DC-to-DC Converter PWM Stabilization via Capacitor Discharge
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Solution Overview
Problem
Brief overvoltages in the on-board voltage of motor vehicles can cause supply overvoltages that disturb the operation of DC-to-DC converters powering LED light sources, leading to flickering luminous intensity and potential color changes due to the charging of capacitors during low states of pulse width modulation.
Innovation Solution
A protective circuit with a bypass mechanism for the diode is integrated into the DC-to-DC converter, allowing the storage capacitor to discharge during low states of pulse width modulation, using a PNP bipolar transistor or a diode in series with a resistor to manage the discharge current, ensuring the capacitor discharges when the voltage exceeds the input voltage, thereby preventing overvoltage disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective diode is connected across the input terminals of the DC-to-DC converter, then the converter is protected against polarity reversals, but the storage capacitor cannot discharge during low states of pulse width modulation, causing supply overvoltages to disturb correct operation
Solution Approach 1:
A bypass diode is introduced as an intermediary component connected in parallel with the protective diode. This bypass diode provides an alternative current path that allows the storage capacitor to discharge during low states of PWM operation, while the protective diode continues to protect against polarity reversals. The intermediary bypass diode resolves the conflict between capacitor discharge needs and protective function.
Solution Approach 2:
The protective circuit is segmented into two separate diode paths: one dedicated to protection (protective diode) and one dedicated to discharge (bypass diode). This segmentation allows each diode to perform its specific function independently without interfering with the other, enabling the capacitor to discharge while maintaining protection capabilities.
2Reliability
If the storage capacitor charges during brief overvoltages, then the capacitor stores energy that could compensate for voltage drops, but the charged capacitor creates supply overvoltages that disturb the correct operation of the converter when activated
Solution Approach 1:
The bypass diode is configured to become active before the converter is activated, allowing the storage capacitor to discharge its stored energy in advance during the low states of PWM. This preliminary discharge action prevents the capacitor from creating harmful supply overvoltages when the converter subsequently activates, while still maintaining the capability to compensate for voltage drops when needed.
Solution Approach 2:
The bypass diode's conductivity is dynamically controlled based on the operational state of the converter. During low states of PWM, the bypass diode is active to allow capacitor discharge. When the converter is active, the bypass diode becomes inactive. This dynamic switching resolves the contradiction between storing energy for stability and discharging to prevent flickering.
3Manufacturing precision
If pulse width modulation is used to control LED luminous intensity, then precise chromaticity control is achieved, but brief overvoltages during low states cause disturbances when the converter reactivates
Solution Approach 1:
The bypass diode acts as an intermediary that specifically addresses the issues arising during low states of PWM operation. It provides a discharge path for the storage capacitor during these low states, preventing the accumulation of charge that would otherwise cause disturbances upon reactivation. This allows PWM to maintain precise chromaticity control without suffering from luminous intensity flickering.
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 solution effectively prevents flickering of LED luminous intensity by rapidly discharging the capacitor during overvoltages, maintaining stable voltage levels when the converter becomes active again, thus ensuring consistent power supply to LED light sources.
Implementation Method 1
a storage capacitive component connected to a diode for protecting against polarity reversals
Implementation Method 2
a diode for protecting against polarity reversals
Implementation Method 3
the bypass means comprises a PNP bipolar transistor with an emitter connected to the anode of the protective diode and a collector connected to the cathode of said diode
Data Source
AI summary
A device for supplying electric power to an electronic component, including a DC-to-DC converter able to operate using pulse width modulation with high states and low states, with an input and an output, the output being intended to supply power to the electrical component; and a protective circuit connected to the input of the DC-to-DC converter, with a storage capacitive component connected to a diode for protecting against polarity reversals. The protective circuit furthermore includes a bypass for bypassing the protective diode so as to allow the storage capacitive component to discharge during the low states of the pulse width modulation.