Quick Discharge Circuit for DC-DC Input Capacitor
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Solution Overview
Problem
In power supply systems, the slow discharge of large-capacity input capacitors in DCDC circuits leads to ineffective soft start circuits during quick power-on events, causing voltage and current spikes that can damage devices.
Innovation Solution
A quick discharge circuit comprising a reference voltage source, power supply voltage monitoring circuit, and control circuit, which uses a field-effect transistor to rapidly discharge the bulk capacitor when the voltage drops below a threshold, ensuring the soft start circuit functions properly upon power-on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large-capacity input capacitor is used in the DCDC circuit to handle spike-type load current, then the power supply stability is improved, but the discharge speed becomes slow causing voltage to drop slowly after power-off
Solution Approach 1:
The patent applies preliminary action by detecting the power-off state in advance through voltage monitoring circuits before the capacitor naturally discharges. When the voltage drops below a threshold, the control circuit activates the discharge switch to forcibly discharge the capacitor, preventing the soft-start circuit from malfunctioning due to residual voltage.
Solution Approach 2:
The patent introduces a discharge switch as an intermediary component between the bulk capacitor and ground. This switch acts as a controlled pathway that can rapidly discharge the capacitor when activated, bridging the gap between the need for energy storage and the need for rapid discharge capability.
2Use of energy by moving object
If the bulk capacitor discharges slowly after power-off, then the energy storage function is maintained, but the soft start circuit becomes ineffective during quick power-on events
Solution Approach 1:
The patent implements feedback through voltage monitoring circuits that continuously detect the voltage level across the bulk capacitor. This feedback signal is fed to the control circuit, which compares the detected voltage against a reference threshold and accordingly controls the discharge switch to maintain the soft-start circuit's effectiveness.
Solution Approach 2:
The patent applies dynamics by making the discharge switch controllable rather than fixed. The switch transitions between on and off states based on real-time voltage conditions, allowing the system to dynamically adjust its discharge behavior to match operational requirements.
3Productivity
If the soft start circuit is bypassed due to ineffective operation, then the power-on process is faster, but voltage and current spikes damage the device
Solution Approach 1:
The patent applies preliminary anti-action by proactively discharging the bulk capacitor when power-off is detected, preventing the condition that would cause soft-start circuit failure. This preliminary discharge action eliminates the harmful residual voltage before quick power-on events occur, protecting against voltage and current spikes.
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 enables rapid voltage drop to a safe range upon power-off and ensures normal operation of the soft start circuit during quick power-on, preventing damage from inrush currents and ensuring stable power supply.
Implementation Method 1
the voltage comparator determine whether an output of the output end of the voltage comparator is at a high level or a low level by comparing a voltage of the positive pole of the power supply input collected by the inverting input end and the reference voltage provided by the reference voltage source
Implementation Method 2
the discharge circuit comprises a field-effect transistor, a gate of the field-effect transistor is connected to the collector of the triode, a source of the field-effect transistor is connected to the positive pole of the power supply input, and a drain of the field-effect transistor is connected to the GND
Data Source
AI summary
A quick discharge circuit includes a reference voltage source, a power supply voltage monitoring circuit, a control circuit, and a discharge circuit. The reference voltage source provides a threshold voltage for quick discharge; the power supply voltage monitoring circuit collects change conditions of a power supply voltage; the control circuit performs logical control according to the power supply voltage collected by the power supply voltage monitoring circuit and the threshold voltage provided by the reference voltage source to determine whether the discharge circuit is ON. With the quick discharge circuit, when a terminal product is powered off, an input bulk capacitor of a DC-DC circuit is discharged quickly so that the voltage thereof rapidly drops to a safe voltage range. When the terminal product is powered on again quickly, it is guaranteed that a soft start circuit works normally so as to implement slow increase of power-on voltage and current.