Lamp Circuit Current Amplification for High Temperature Control
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Solution Overview
Problem
Lamp circuits without a microcontroller (MCU) are vulnerable to external noise and have limited current control performance, leading to ineffective current control at high temperatures, reduced dimming control range, and increased production costs due to the need for noise filters and large heat sinks.
Innovation Solution
A lamp circuit design that includes a light emitting circuit with a thermistor and a light emission control circuit comprising a constant current circuit, dimming control circuit, voltage divider, and current amplification circuit to amplify the thermistor current and improve dimming control, allowing effective current control at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a lamp circuit does not include an MCU and uses only diode characteristics and thermistor resistance change for current control, then the device complexity is reduced, but the current control performance at high temperatures deteriorates
Solution Approach 1:
The patent introduces a current amplification circuit as an intermediary component between the thermistor and the light emitting device. This amplifier circuit receives the small current signal from the thermistor and amplifies it to a level sufficient for effective control of the light emitting device, even at high temperatures where the thermistor's resistance change is minimal. This resolves the contradiction by adding a moderate complexity component (amplifier) that significantly boosts control performance without requiring a full MCU system.
2Reliability
If the current control starts from a low temperature to compensate for slowed thermistor current change rate at high temperature, then the current control effectiveness is improved, but the dimming control temperature range is reduced
Solution Approach 1:
The patent changes the operating parameter by introducing current amplification. Instead of relying solely on the thermistor's resistance change (which slows down at high temperatures), the amplifier circuit maintains a consistent gain ratio that preserves control effectiveness across a wide temperature range. This allows the dimming control to function effectively from low to high temperatures without needing to start control only from low temperature conditions.
3Reliability
If a filter is included in the lamp circuit to prevent vulnerability to noise, then the reliability against external noise is improved, but the production cost increases
Solution Approach 1:
The current amplification circuit serves as an intermediary that inherently provides noise rejection capability. By amplifying the thermistor current signal with a fixed gain ratio, the circuit maintains signal integrity and rejects external noise without requiring additional filter components. This resolves the contradiction by achieving noise immunity through the amplifier's inherent characteristics rather than adding separate filter elements that would increase cost.
4Temperature
If a large heat sink is used to prevent the lamp circuit from reaching high temperature, then the temperature control is improved, but the device volume increases
Solution Approach 1:
The patent implements a feedback control mechanism where the thermistor continuously monitors the current through the light emitting device and the amplification circuit adjusts the current accordingly. This active feedback control allows for precise temperature management without requiring excessive passive cooling components like large heat sinks. The system actively regulates heat generation rather than relying solely on passive heat dissipation, thereby reducing the required heat sink volume.
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
Enhances current control of the light emitting device at high temperatures, expands the dimming control temperature range, and reduces the need for large heat sinks and noise filters, thereby lowering production costs.
Implementation Method 1
a current amplification circuit, and the current amplification circuit amplifies a current of the thermistor
Implementation Method 2
a voltage divider, and the voltage divider divides a first voltage to a first node between the first resistor and the second resistor based on the amplified current
Implementation Method 3
a negative temperature coefficient thermistor (NTC)... the decrease rate of resistance value per unit temperature is slowed as the temperature increases
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A lamp circuit including a light emitting circuit and a light emission control circuit that controls the light emitting circuit. The light emitting circuit includes a thermistor and a light emitting device, and the light emission control circuit comprised a constant current circuit, dimming control circuit, voltage divider having a first resistor and a second resistor, and a current amplification circuit. The current amplification circuit amplifies a current of the thermistor, and the voltage divider divides a first voltage to a first node between the first resistor and the second resistor based on the amplified current. The dimming control circuit controls an output current of the constant current circuit based on the first voltage, and the constant current circuit outputs a current to the light emitting device based on the control of the dimming control circuit.