Ignition Current Limiting Circuit With Temperature-Matched Reference Voltage
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Solution Overview
Problem
Existing ignition control devices for internal combustion engines face challenges in accurately detecting primary currents due to the positive temperature-dependent characteristic of metal detection resistors, leading to detection errors and increased product costs from additional adjustment steps required to match MOS transistor gate voltages.
Innovation Solution
The solution involves a current limiting circuit with a detection voltage generation unit using a metal current detection resistor and a reference voltage generation unit based on a potential difference between bipolar transistors, which generates a reference voltage with a similar temperature-dependent characteristic, eliminating the need for extra adjustment steps and reducing product costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a metal detection resistor with positive temperature dependent characteristic is used to detect primary current, then the detection voltage varies with temperature change, but using a reference voltage with temperature dependent characteristic (MOS transistor ON resistor) can prevent detection error
Solution Approach 1:
The patent changes the parameter of the reference voltage generation mechanism from MOS transistor ON resistor to bipolar transistor circuit. The bipolar transistor circuit generates a reference voltage with temperature dependent characteristic that matches the detection voltage's temperature characteristic, eliminating the need for complex adjustment steps while maintaining detection accuracy across temperature variations.
2Measurement precision
If MOS transistor ON resistor is used to generate reference voltage with temperature dependent characteristic, then detection error can be prevented, but device variation requires matching adjustment and increases unit price
Solution Approach 1:
The patent replaces the expensive MOS transistor-based reference voltage generation (requiring adjustment) with a bipolar transistor circuit that inherently provides temperature-compensated reference voltage. This substitution eliminates the need for costly adjustment steps and reduces manufacturing complexity while maintaining detection accuracy.
3Measurement precision
If the reference voltage is made to have temperature dependent characteristic to match detection voltage, then detection error is reduced, but additional adjustment steps are required
Solution Approach 1:
The bipolar transistor circuit automatically generates a reference voltage with temperature dependent characteristic that self-adjusts to match the detection voltage's temperature characteristic. This self-service mechanism eliminates the need for external adjustment steps, saving time while maintaining detection accuracy across temperature variations.
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 approach stabilizes the reference voltage, reducing detection errors and eliminating the need for additional adjustment steps, thereby maintaining product cost-effectiveness and accuracy across varying temperatures.
Implementation Method 1
the detection voltage also has a 'positive' temperature dependent characteristic
Implementation Method 2
the reference voltage is generated by a potential difference (proportional to a thermal voltage VT) between a base and an emitter of a first bipolar transistor circuit
Data Source
AI summary
To provide an ignition control device of an internal combustion engine capable of reducing the number of adjustment steps required for adjustment such as matching of a MOS gate voltage or the like without being affected by device variation. A detection voltage is generated on the basis of a primary current flowing through a current detection resistor having a positive temperature dependent characteristic. A reference voltage is generated by a potential difference between a base and an emitter of a first bipolar transistor circuit and a multiple type second bipolar transistor circuit in which a plurality of bipolar transistors are connected in parallel, and a resistance value of a first resistor connected to the emitter side of the plurality of the bipolar transistor circuit, on the basis of a current having a positive temperature dependent characteristic similar to the current detection resistor.