Level Shift Circuit Using Capacitor Hold-Up Below Ground Potential
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Solution Overview
Problem
Conventional high-voltage level shift circuits experience signal transmission malfunctions when the power supply of the secondary circuit becomes equal to or lower than the ground potential, leading to attenuation of the transmission signal source.
Innovation Solution
A level shift circuit incorporating a level shift transistor, a diode connected in forward direction, a capacitor in parallel to the diode, and an inverter to invert the signal, with the control electrode connected to the primary side power supply and the second main electrode connected to the output of the inverter, ensuring signal transmission even when the secondary side power supply is equal to or lower than the primary side reference potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional high-voltage level shift circuit is used, then signal transmission is achieved under normal power supply conditions, but signal transmission malfunctions occur when the secondary side power supply becomes equal to or lower than the ground potential
Solution Approach 1:
The capacitor is pre-charged to the power supply voltage before the power supply drops to ground potential or lower. When the power supply voltage becomes ground or lower, the capacitor maintains the potential difference needed for signal transmission, enabling the level shift transistor to continue functioning as a signal transmission path despite the degraded power supply condition.
Solution Approach 2:
The capacitor acts as an intermediary energy storage element between the power supply and the level shift transistor. It mediates the transition from normal power supply conditions to degraded conditions by maintaining the necessary voltage potential, allowing signal transmission to continue when direct power supply connection would fail.
2Use of energy by moving object
If the secondary side power supply drops to ground potential or lower, then power consumption is reduced, but the transmission signal source becomes attenuated and signal transmission fails
Solution Approach 1:
The capacitor is charged in advance when power supply voltage is normal, storing energy before the power supply drops. This preliminary energy storage ensures that when power consumption is reduced to ground potential or lower, the stored energy in the capacitor maintains the signal transmission capability, preventing signal attenuation and transmission failure.
Solution Approach 2:
The circuit transitions from relying on real-time power supply voltage to relying on stored capacitor voltage when the power supply parameter drops to ground or lower. This parameter change allows the signal transmission function to maintain reliability despite the degraded power supply condition, as the capacitor provides the necessary voltage potential.
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 proposed solution maintains signal transmission to the secondary side circuit by dropping the potential of the capacitor electrodes, applying the dropped voltage to a resistance element, and transmitting the signal effectively, even when the secondary side power supply is at or below the ground potential.
Implementation Method 1
a capacitor connected in parallel to the diode
Implementation Method 2
a diode connected in a forward direction between a first main electrode of the level shift transistor and the secondary side circuit
Data Source
AI summary
A level shift transistor of a first conductivity type configured to level shift a signal from a primary side circuit to a secondary side circuit between the primary side circuit having a primary side reference potential as reference and the secondary side circuit having a secondary side reference potential independent from the primary side reference potential as reference, a diode connected in a forward direction between a first main electrode of the level shift transistor and the secondary side circuit, a capacitor connected in parallel to the diode, and an inverter configured to invert the signal are provided. A control electrode of the level shift transistor is connected to a primary side power supply of the primary side circuit, and a second main electrode thereof is connected to an output of the inverter. The inverter operates between the primary side reference potential and the primary side power supply.