EMC Protection Circuit Using PMOS Switch and Delay Control
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Solution Overview
Problem
Electronic circuits face challenges in protecting against electromagnetic compatibility (EMC) disturbances and transient overvoltage pulses, which can lead to damage from reverse current flow and polarity reversal, especially in harsh environments like automotive systems, where existing solutions require thick gate NMOS devices and charge pumps, resulting in high voltage drops and inefficiencies.
Innovation Solution
A protection circuit using a PMOS transistor switch with a comparator and delay circuit to control the switch's operation, preventing reverse current flow and maintaining functionality during EMC disturbances and negative overvoltage pulses, eliminating the need for charge pumps and reducing voltage drop, and incorporating a diode for continued supply during switch off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection circuit uses thick gate NMOS devices to protect against polarity reversal and voltage transients, then protection reliability is improved, but voltage drop increases and circuit complexity increases due to charge pump requirements
Solution Approach 1:
The patent changes the transistor type from NMOS to PMOS and modifies the gate control mechanism. By using a PMOS transistor with gate controlled by a comparator output, the circuit achieves protection without requiring thick gate devices or charge pumps, thereby reducing voltage drop while maintaining protection reliability.
Solution Approach 2:
The patent extracts and eliminates the charge pump component from the protection circuit. By using a simplified PMOS-based approach with direct comparator control, the charge pump is removed entirely, reducing circuit complexity and eliminating the associated voltage drop and energy loss.
2Reliability
If a protection circuit uses thick gate NMOS devices to protect against polarity reversal and voltage transients, then protection reliability is improved, but device complexity increases due to charge pump requirements
Solution Approach 1:
The patent extracts and eliminates the charge pump component from the protection circuit. By using a simplified PMOS-based approach with direct comparator control, the charge pump is removed entirely, reducing circuit complexity while maintaining protection functionality.
Solution Approach 2:
The protection circuit uses the existing power supply voltage and ground references to control the PMOS gate through the comparator. The circuit serves itself by using available voltage rails (VCC, VREG, GND) without requiring external charge pump circuits or additional complex control mechanisms.
3Speed
If a protection circuit switches off immediately upon detecting voltage drop, then protection speed is improved, but functionality is lost during transient pulses due to lack of delay
Solution Approach 1:
The patent implements a delay mechanism that keeps the PMOS transistor switched off for a predetermined time period after voltage recovery is detected. This preliminary delay action ensures that transient negative pulses are fully cleared before the circuit resumes operation, preventing premature switching that would compromise functionality during transients.
Solution Approach 2:
The delay circuit provides a cushioning period that protects the circuit from premature operation during transient recovery. By maintaining the switched-off state for a predetermined time, the circuit cushions against potential instability or residual effects of the transient pulse, ensuring reliable functionality before resuming normal operation.
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 effectively protects electronic circuits from EMC disturbances and transient overvoltage pulses, ensuring continuous operation with reduced voltage drop and no need for external charge pumps, enhancing resilience to electromagnetic interference and reducing the risk of damage from reverse current and polarity reversal.
Implementation Method 1
a comparator for comparing a first operating parameter with a second operating parameter and producing a comparison signal
Implementation Method 2
The transistor is a P-channel enhancement MOSFET of which the source is coupled to the positive terminal of the power supply and the drain is coupled to the positive terminal of the load
Implementation Method 3
a delay circuit adapted for delaying closing of the switch
Data Source
AI summary
A protection circuit for protecting an electronic circuit against EMC disturbances and/or negative transient overvoltage pulses comprises a switch in series between a power supply and the electronic circuit to be protected; a comparator for comparing a first operating parameter with a second operating parameter and producing a comparison signal, the comparison signal being used as a control signal for controlling opening and closing of the switch; and a delay circuit adapted for delaying closing of the switch. A corresponding method is also provided.