Input Detection Circuit for HID Ballast Surge Protection
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Solution Overview
Problem
Power supply systems face high failure rates due to input voltage surges, incorrect wire connections, phase loss, and lightning-induced voltage fluctuations, which exceed the designed withstand voltage, leading to damage to internal components like electrolytic capacitors and MOS transistors, especially in complex grid environments.
Innovation Solution
An input detection and protection circuit comprising a power input circuit with varistors and a thermistor, an input voltage acquisition circuit with diodes and capacitors, a pull-in circuit for a relay, and an MCU chip that controls the Power Factor Correction (PFC) circuit to limit and monitor input voltage, preventing damage by switching on/off the relay and PFC accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the product is connected to a wrong wire in 3-phase 4-wire power distribution, then the actual input voltage becomes 1.7 times the nominal value (e.g., 400 VAC for a 230 V product), but the product's withstand voltage is greatly exceeded causing damage
Solution Approach 1:
The patent implements preliminary voltage detection and relay control before the power supply circuit is activated. The MCU detects input voltage through the voltage acquisition circuit, and the relay is controlled to be in a disconnected state before power-on. This preliminary action prevents overvoltage damage by ensuring the relay is only connected after voltage normality is confirmed, avoiding the scenario where wrong wire connection causes immediate damage.
Solution Approach 2:
The patent introduces an intermediary detection and control system between the power input and the power supply circuit. The voltage acquisition circuit acts as an intermediary to detect input voltage, the MCU processes the voltage information, and the relay serves as an intermediary switching device. This intermediary system mediates between the potentially harmful input voltage and the protected power supply circuit, enabling safe operation.
2Reliability
If the grid has voltage surge exceeding the withstand voltage of internal devices, then the surge voltage damages electrolytic capacitors and MOS transistors, but adding protection circuits increases system complexity
Solution Approach 1:
The patent implements a multi-functional integrated protection system where the voltage acquisition circuit, MCU, and relay work together to provide multiple protection functions. The same detection circuit monitors both overvoltage and undervoltage conditions, and the relay provides both pre-power-on protection and ongoing voltage abnormality protection. This universal approach achieves comprehensive protection without proportionally increasing circuit complexity.
Solution Approach 2:
The protection system is self-regulating through automatic detection and control. The voltage acquisition circuit automatically detects voltage abnormalities, the MCU automatically processes the detection results, and the relay automatically switches states based on voltage conditions. This self-service mechanism eliminates the need for external manual intervention or complex control systems, achieving reliable protection with minimal added complexity.
3Reliability
If three-phase imbalance caused by neutral line phase loss occurs, then one phase voltage exceeds input rating, resulting in damage to internal electrolytic capacitors and MOS transistors, but detection and protection mechanisms increase device complexity
Solution Approach 1:
The voltage acquisition circuit and MCU serve multiple detection purposes: they detect both overvoltage conditions and undervoltage conditions, and by extension can detect phase loss conditions through voltage imbalance analysis. The relay provides unified protection for all these conditions. This multi-functional approach enables phase loss protection without requiring separate dedicated detection circuits, thereby limiting the increase in device complexity.
4Reliability
If surge voltage is induced at the moment of switching on or off, then high voltage is generated which damages internal devices, but implementing soft-start and protection circuits increases system complexity
Solution Approach 1:
The patent implements preliminary voltage detection and relay control before the power supply circuit is activated. The MCU detects input voltage through the voltage acquisition circuit, and the relay is controlled to be in a disconnected state before power-on. This preliminary action prevents overvoltage damage by ensuring the relay is only connected after voltage normality is confirmed, avoiding the scenario where wrong wire connection causes immediate damage.
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
Effectively reduces surge current and protects against abnormal input voltages, minimizing damage from high or low voltages, and providing standby power to indicate abnormalities, thus enhancing the reliability of power supply systems in diverse voltage environments.
Implementation Method 1
a first varistor, a second varistor, a thermistor and the relay, and the input surge voltage is firstly limited by the first varistor and then secondly limited by the second varistor and the thermistor
Implementation Method 2
the input surge voltage is firstly limited by the first varistor and then secondly limited by the second varistor and the thermistor
Implementation Method 3
the pull-in circuit for a relay is connected to a relay in the power input circuit, and the MCU chip controls the PFC circuit to switch on and off, and controls pull-in and drop-out of the relay
Data Source
AI summary
An input detection and protection circuit and an AC electronic ballast for HID lamps, including a power input circuit performing a first limitation to an input surge voltage and then performing a second limitation to a residual voltage from the first input surge voltage limitation; an input voltage acquisition circuit feeding back an input voltage to an MCU chip; a pull-in circuit for a relay connecting to a relay in the power input circuit; a PFC circuit, and an MCU chip controlling the PFC circuit to switch on and off according to voltage values input by the input voltage acquisition circuit, and controlling pull-in and drop-out of the relay through the pull-in circuit for the relay.