Glow Time Control Device Protection Circuit
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Solution Overview
Problem
Existing glow time control devices for vehicle engines are prone to damage due to incorrect wiring, polarity reversal, and electrostatic discharges, which can lead to malfunction or destruction of the device and connected glow plugs.
Innovation Solution
The implementation of a protective circuit within the glow time control device that includes power transistors, zener diodes, and ESD spark gaps to prevent damage from incorrect connections, polarity reversals, and electrostatic discharges, ensuring reliable operation by blocking power transistors when unreliable signals are present and dissipating high voltages to ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the glow time control unit is incorrectly connected during assembly or maintenance, then voltages can be applied to the inputs and outputs which can damage the control unit, but adding protective circuits increases device complexity
Solution Approach 1:
The protective circuit proactively monitors the supply voltage before it can cause damage to the control unit. The circuit is pre-configured with transistors and zener diodes that automatically activate when voltage thresholds are exceeded, preventing damage before it occurs rather than responding after damage happens.
Solution Approach 2:
The protective circuit acts as an intermediary between the external power source and the control unit. It includes intermediate components such as transistors (T1-T4), zener diodes (D1-D8), and resistors that stand between the potentially harmful voltage sources and the vulnerable control unit inputs, filtering and regulating the voltage to safe levels.
2Reliability
If a protective circuit is added to prevent damage from polarity reversal and electrostatic discharges, then reliability improves, but manufacturing complexity increases
Solution Approach 1:
The protective circuit is divided into separate functional segments: polarity protection segments using diodes (D1-D4) for each input line, ESD protection segments using zener diodes (D5-D8) and transistors (T1-T4) for voltage clamping, and monitoring segments using resistors (R1-R4) to detect voltage conditions. Each segment can be independently analyzed and manufactured.
Solution Approach 2:
The protective circuit changes the electrical parameters of the input signals through voltage clamping (using zener diodes to limit voltage to safe levels), current limiting (using resistors to restrict current flow), and polarity blocking (using diodes to prevent reverse current). These parameter transformations make incompatible signals compatible for the control unit.
3Ease of operation
If the control inputs of power transistors are commonly coupled to reduce complexity, then ease of operation improves, but vulnerability to electrostatic discharges increases
Solution Approach 1:
Individual protective components are placed as intermediaries between the common control input and each power transistor. Zener diodes (D5-D8) and transistors (T1-T4) are positioned between the control signal line and each transistor gate, acting as local mediators that protect each transistor from ESD while still allowing the common control signal to reach all transistors.
Solution Approach 2:
The protection is applied locally at each transistor gate rather than globally at the control input. Each power transistor receives individual protection through its own zener diode and transistor combination, allowing the control inputs to remain commonly coupled for ease of operation while each local protection zone handles ESD independently.
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 protective circuit effectively prevents damage to the glow time control device and connected glow plugs by blocking power transistors during incorrect connections and discharging electrostatic discharges, ensuring reliable engine operation and preventing malfunctions.
Implementation Method 1
ESD spark gaps for dissipating voltages of electrostatic discharges to ground
Implementation Method 2
The protection circuit has an input which is coupled to the supply voltage input of the control unit, the protection circuit being set up to set a predetermined potential at the protection circuit output when the supply voltage of the control unit is below a predetermined value
Data Source
Figure 1
Figure 2
AI summary
The present invention relates to a glow time control device (100) for controlling glow rods (206-209) in a vehicle (200). The glow time control device (100) comprises a control unit (IC1), at least two power transistors (T1, T4) and a protective circuit (T6, T7). The control unit (IC1) comprises a control output (GG1) for emitting a control signal, a supply voltage input (VCC) and a supply voltage output (VDD). The control unit (IC1) provides an output voltage at the supply voltage output (VDD) depending on a voltage at the supply voltage input (VCC). A corresponding glow rod control output (G1, G4) is assigned to each of the power transistors (T1, T4) and the control inputs of the power transistors (T1, T4) are coupled to the control output (GG1). The protective circuit (T6, T7) comprises a protective circuit output which is coupled to the control inputs of the power transistors (T1, T4), and an input which is coupled to the supply voltage output (VDD). The protective circuit adjusts a predefined potential at the protective circuit output if the output voltage of the control unit (IC1) is below a predefined value.