High Side Switch Charge Pump Voltage Drop Protection
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Solution Overview
Problem
High side switch circuits using n-channel MOSFETs often fail to maintain power supply to loads during momentary voltage drops, causing unintended shutdowns due to the reliance on charge pumps that stop operating below an undervoltage threshold.
Innovation Solution
Incorporating a diode in the ground path and a capacitor between the power supply and the diode within the charge pump circuit allows the charge pump to maintain the semiconductor switch in an ON state during momentary voltage drops by sustaining the necessary voltage and current, preventing shutdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge pump is used to provide gate voltage for the n-channel MOSFET, then the switch can be turned on, but the switch turns off during momentary voltage drops below the undervoltage threshold
Solution Approach 1:
The capacitor is pre-charged to the undervoltage threshold before the voltage drop occurs. When the voltage drop happens, this pre-stored charge is discharged to maintain the gate voltage above the threshold, keeping the MOSFET turned on during the transient event.
Solution Approach 2:
The capacitor acts as a cushion or buffer that absorbs the impact of voltage drops. By being pre-charged to the threshold voltage, it provides a safety margin that prevents the gate voltage from falling below the threshold during transient undervoltage conditions.
2Reliability
If the charge pump operates continuously to maintain switch on state, then the switch remains on, but power is consumed even during voltage drops
Solution Approach 1:
The capacitor is pre-charged during normal operation when voltage is sufficient. This preliminary charging action stores energy in advance, so that during voltage drops the charge pump doesn't need to operate continuously - it only needs to replenish the capacitor when voltage is available.
Solution Approach 2:
The capacitor ensures continuous useful action by maintaining gate voltage during voltage drops without requiring continuous charge pump operation. The charge pump operates intermittently to recharge the capacitor, reducing overall power consumption while maintaining continuous switch 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
This configuration ensures continuous power supply to loads during temporary voltage fluctuations, extending the operational time of the charge pump and preventing unnecessary switch-offs, even during brief supply voltage drops.
Implementation Method 1
a capacitor (C1) having a positive terminal adapted to be connected to the output of the charge pump and a negative terminal adapted to be connected to ground. The capacitor (C1) is charged to a voltage slightly below the undervoltage threshold of the charge pump.
Implementation Method 2
a diode (D1) having an anode adapted to be connected to the negative terminal of the capacitor (C1) and a cathode adapted to be connected to ground
Data Source
AI summary
A circuit arrangement for selectively supplying power from a power supply to a load includes a semiconductor switch, such as an n-channel FET, along with a gate control and a charge pump. The circuit additionally includes a diode located in a ground path between a ground connection of the charge pump and a circuit ground, and a capacitor connected between the power supply and the diode. The added diode and capacitor allow the charge pump to maintain the FET in an ON state during a momentary voltage drop of the supply voltage. This circuit is preferably used with a high side switch integrated circuit.