Linear Regulator Surge Protection Using an External Diode
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Solution Overview
Problem
Existing linear regulators with Zener diodes for surge protection incur increased loss and size issues when handling high input voltages, necessitating larger, more costly diodes to manage surge voltages effectively.
Innovation Solution
A linear regulator design incorporating an external diode and a semiconductor integrated circuit with a parallel diode and control circuit, where the external diode is connected to the output terminal and the parallel diode is in parallel with the output transistor, allowing for efficient surge voltage management without the need for a Zener diode, thereby reducing overall size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Zener diode is used for surge protection in a linear regulator with high input voltage, then surge voltage protection is achieved, but the diode package size must be large causing increased overall size and cost
Solution Approach 1:
The patent extracts the surge protection function from the main linear regulator circuit by using a separate external diode connected to the output terminal. This external diode handles surge currents independently, allowing the main regulator circuit to use smaller protection components. The surge protection capability is separated from the voltage regulation function, enabling optimized component sizing.
Solution Approach 2:
The patent introduces an external diode as an intermediary element between the output terminal and ground. This external diode acts as a mediator that absorbs surge currents before they can damage sensitive internal circuits. By placing this intermediary protection element outside the main IC, the internal diode can be smaller while still providing effective surge protection.
2Reliability
If a Zener diode with high Zener voltage is used to protect against positive surge voltage, then protection capability is improved, but power loss in the diode increases significantly
Solution Approach 1:
The patent extracts the positive surge protection function from the internal Zener diode and assigns it to an external diode. The external diode is configured to handle positive surge currents by conducting them to ground through its forward bias path. This separation allows the internal diode to operate at lower voltages with reduced power loss while the external diode handles the high-voltage surge events.
Solution Approach 2:
The patent changes the operating parameters of the protection diode by using an external diode with different electrical characteristics. The external diode is selected to have appropriate forward voltage and current handling capabilities for surge protection, while the internal diode maintains lower voltage operation for normal regulation. This parameter differentiation reduces overall power loss while maintaining protection capability.
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 configuration effectively manages both positive and negative surge voltages by directing surge currents through the external and parasitic diodes, minimizing losses and allowing for the use of smaller diodes, thus reducing the linear regulator's size and cost while protecting the circuit from surge voltages.
Implementation Method 1
A surge current based on the positive surge voltage flows from the cathode of the Zener diode 920 to the anode so that a positive voltage applied to the input terminal 911 is clamped to the Zener voltage Vz
Implementation Method 2
a surge current based on the negative surge voltage flows from the anode of the Zener diode 920 to the cathode so that the magnitude of a negative voltage applied to the input terminal 911 is clamped to a forward voltage (Vf) of the Zener diode 920
Data Source
AI summary
Disclosed is a linear regulator for generating an output voltage from an input voltage with reference to a ground potential, the linear regulator including a semiconductor integrated circuit, and an external diode that is externally connected to the semiconductor integrated circuit, in which the semiconductor integrated circuit includes an input terminal, an output terminal, an output transistor, a parallel diode, and a control circuit, and an anode of the external diode is connected to a ground, and a cathode of the external diode is connected to the output terminal.