Boost DC-DC Converter Load Switch Control for Voltage Leap-Up
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Solution Overview
Problem
Boost DC-DC converters experience significant leap-up of output voltage when activated with input voltage higher than the target level due to induced voltage from the inductor, leading to unstable output voltage stabilization.
Innovation Solution
A control circuit that includes a pulse modulator, logic circuit, load switch drive circuit, and current detection circuit, allowing the load switch drive circuit to switch between fully turning on the PMOS transistor and adjusting its gate voltage based on current detection signals to maintain a current supply capacity greater than the detected current, thereby preventing excessive current flow and voltage leap-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the load switch is fully turned on to minimize loss when input voltage is higher than target output voltage, then energy loss is reduced, but output voltage leaps up significantly due to inductor induced voltage
Solution Approach 1:
The load switch drive circuit dynamically adjusts the gate voltage of the PMOS transistor based on real-time current detection signals. Instead of maintaining a fixed fully-on state, the circuit continuously modulates the gate voltage to keep the current supply capacity slightly larger than the detected current, preventing voltage leap-up while minimizing energy loss.
Solution Approach 2:
The circuit employs a feedback mechanism where the current detection signal from the current detection circuit is fed back to the load switch drive circuit. This feedback loop enables the drive circuit to adjust the PMOS transistor's gate voltage in response to changing current conditions, maintaining stable output voltage while optimizing energy efficiency.
2Productivity
If the load switch is fully turned on to minimize loss, then energy efficiency is improved, but the current supply capacity becomes excessive causing voltage leap-up
Solution Approach 1:
The circuit changes the operating parameters of the PMOS transistor by dynamically adjusting its gate voltage. This parameter adjustment optimizes the transistor's current supply capacity to be slightly larger than the detected current, achieving a balance between energy efficiency and preventing harmful voltage leap-up effects.
Solution Approach 2:
The circuit intentionally maintains the current supply capacity of the PMOS transistor at a level slightly excessive compared to the detected current requirement. This partial excess capacity provides a safety margin that prevents voltage leap-up while keeping energy loss minimal, avoiding the need for complete full-on operation.
3Reliability
If a load switch is inserted to prevent voltage supply when stopped, then voltage control is improved, but device complexity increases
Solution Approach 1:
The load switch drive circuit is designed to perform multiple functions: it controls the PMOS transistor during normal operation to prevent voltage leap-up, and also enables the load switch to prevent voltage supply when the converter is stopped. This multi-functional design improves voltage control reliability without proportionally increasing device complexity.
Solution Approach 2:
The circuit merges the functions of the load switch control with the main control circuitry. By integrating the load switch drive circuit with the existing pulse modulator and current detection circuit, the design achieves improved voltage control while minimizing the increase in overall device complexity through functional consolidation.
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 suppresses output voltage leap-up, stabilizing the output voltage by adjusting the current supply capacity of the PMOS transistor, reducing losses and maintaining the target voltage level even when the input voltage exceeds the output voltage target.
Implementation Method 1
the output voltage may significantly leap up due to the influence of an induced voltage of the inductor
Data Source
AI summary
Disclosed is a control circuit of a boost DC-DC converter including a high side transistor and a low side transistor, and a load switch connected between the high side transistor and an output line of the boost DC-DC converter. The control circuit includes a pulse modulator that generates a pulse signal with a pulse modulated to bring an output voltage of the output line close to a target level, a logic circuit that generates a high side control signal and a low side control signal based on the pulse signal, a load switch drive circuit that drives a first PMOS transistor provided as the load switch, and a current detection circuit that generates a current detection signal indicating a current flowing through the first PMOS transistor. The load switch drive circuit is switchable between a first mode and a second mode.