Output Driver Start-Up Circuit for Fast MOS Gate Turn-On
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Solution Overview
Problem
Metal oxide semiconductor (MOS) transistors in output drivers experience delayed response times due to variations in process, voltage, or temperature, leading to disproportionate rise and fall ratios, particularly when the MOS transistor requires time to reach the turn-on voltage.
Innovation Solution
A start-up circuit comprising a voltage provider that charges a charge store to a pre-turn-on voltage, which is then connected to the MOS driver, enabling rapid activation of the output driver by discharging the stored voltage directly to the driver transistor, thus mitigating delays and controlling the rise and fall ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a MOS transistor is used in the output driver, then the device can be manufactured with standard semiconductor processes, but the response time is delayed due to PVT variations and gate charging requirements
Solution Approach 1:
The patent applies preliminary action by pre-charging a capacitor to a specific voltage level before the MOS transistor needs to switch. This stored charge is then rapidly discharged through the transistor gate, providing an immediate voltage boost that overcomes the delayed gate charging problem. The capacitor is charged in advance during a setup phase, so when switching is needed, the charge is already available for rapid transfer.
Solution Approach 2:
The patent introduces a capacitor as an intermediary energy storage element between the power source and the MOS transistor gate. This capacitor acts as a mediator that can rapidly discharge its stored charge to quickly charge the transistor gate, bypassing the slow direct charging path. The intermediary capacitor decouples the slow charging process from the fast switching requirement.
2Device complexity
If the MOS transistor gate is charged directly from the power source, then the circuit is simple, but the response time is delayed due to gate charging requirements
Solution Approach 1:
The capacitor is pre-charged to a voltage higher than the normal operating voltage before the switching event. This preliminary charging action stores energy in advance, so when the MOS transistor needs to switch, the gate can be charged rapidly from this pre-charged capacitor rather than slowly charging from the power source through resistive paths.
Solution Approach 2:
The circuit operates in periodic phases: a charging phase where the capacitor is slowly charged from the power source, and a discharging phase where the capacitor rapidly discharges to charge the MOS gate. This periodic alternation between slow charging and fast discharging resolves the contradiction between simple circuitry and fast response.
3Ease of manufacture
If the output driver uses standard MOS transistor switching, then the design is straightforward, but disproportionate rise and fall ratios occur due to delay variations
Solution Approach 1:
The patent changes the voltage parameter by using a capacitor charged to a voltage higher than the normal operating voltage. This elevated voltage level compensates for PVT variations by providing sufficient overdrive voltage even when process variations, voltage drops, or temperature effects reduce the effective gate voltage. The parameter change ensures consistent switching behavior across different operating conditions.
Solution Approach 2:
The circuit incorporates a voltage margin or cushion by charging the capacitor to a voltage higher than the minimum required turn-on voltage. This beforehand cushioning accounts for potential voltage drops and PVT variations, ensuring that the MOS transistor receives sufficient gate voltage to switch properly even under adverse conditions, thereby maintaining consistent rise and fall ratios.
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 reduces the response time of the output driver, minimizes start-up current, and maintains consistent voltage levels, effectively addressing the delays and disproportionate rise and fall ratios caused by PVT variations.
Implementation Method 1
a voltage provider charges a charge store to a pre-turn-on voltage
Implementation Method 2
enabling rapid activation of the output driver by discharging the stored voltage directly to the driver transistor
Data Source
AI summary
One or more techniques and systems for starting an output driver and an associated start-up circuit are provided herein. In some embodiments, a voltage provider is configured to charge a charge store to a pre-turn-on voltage. In some embodiments, an output driver is configured to control a connection between the charge store and the output driver. For example, the connection enables the charge store to discharge a voltage to the output driver, thus starting the output driver. Accordingly, a response time associated with starting the output driver is mitigated at least because the charge store is charged to the pre-turn-on voltage and connected to the output driver such that a gate of the driver is biased in a sudden fashion. In this manner, the driver is turned on more quickly. Additionally, effects associated with process, voltage, and temperature variations are mitigated, for example.