Bootstrapped High-Side Driver Control Without Static DC Current
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Solution Overview
Problem
High-side driver circuits in electric motor driver circuits face challenges in reducing current draw and power consumption from the boosted supply voltage, leading to the need for a more efficient integrated motor driver circuit with reduced charge pump capacitance.
Innovation Solution
The proposed solution involves a high-side driver circuit that shortens the gates of high-side driver transistors to the output nodes instead of applying a boosted voltage, using the motor supply voltage to power the high-side driver circuit, thereby minimizing static and dynamic current draw from the charge pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge pump is used to generate boosted voltage for high-side driver, then the driver can achieve low on-resistance, but current draw and power consumption from the charge pump increases
Solution Approach 1:
The patent implements periodic charging of the high-side driver gate using a capacitor that is charged during specific phases (when low-side driver is active) and discharged during other phases. This periodic action replaces continuous charge pump operation, reducing current draw while maintaining the necessary gate voltage for low on-resistance operation.
Solution Approach 2:
The high-side driver circuit uses the existing motor supply voltage and low-side driver operation to automatically charge the gate capacitor through diodes and resistors. The circuit serves itself by utilizing the motor's own operating cycles to generate the required gate drive voltage, eliminating dependence on continuous charge pump current.
2Use of energy by moving object
If a large charge pump capacitor is used to supply current, then current draw can be managed, but the capacitor cannot be integrated on chip
Solution Approach 1:
By charging the capacitor periodically during low-side driver operation rather than requiring continuous charge pump current, the patent reduces the capacitor size needed for current management. This periodic charging approach enables on-chip integration of the capacitor while still managing current draw effectively.
Solution Approach 2:
The patent changes the operating parameters by using the motor supply voltage (rather than boosted voltage) for capacitor charging and by utilizing the natural operation cycles of the low-side driver. This parameter change enables smaller capacitor values that can be integrated on chip while maintaining current management performance.
3Ease of operation
If predriver and control circuits are powered by boosted voltage, then they can control the high-side driver, but they draw static and dynamic current from the charge pump
Solution Approach 1:
The predriver and control circuits are designed to operate periodically using the motor supply voltage rather than continuous boosted voltage. They utilize the natural switching cycles of the motor driver to activate only when needed, reducing static and dynamic current draw from the charge pump while maintaining high-side driver control capability.
Solution Approach 2:
Instead of powering the predriver and control circuits with boosted voltage from the charge pump, the patent inverts the approach by powering them with the motor supply voltage. This inversion eliminates their current draw from the charge pump while they still perform their control function through the periodic charging mechanism.
Data Source
AI summary
A motor driver circuit for driving the gate node of a high-side driver transistor to a boosted voltage from a charge pump draws little or no static current from the charge pump. The gate node is pulled to the boosted voltage by a p-channel pullup-control transistor that is driven by p-channel transistors that are pumped by capacitors that cut off current flow to ground from the charge pump. An n-channel output-shorting transistor shorts the gate node to the output when the high-side driver is turned off. A coupling capacitor initializes the shorting transistor for each output transition. A p-channel output-sensing transistor generates a feedback to a second stage that drives the coupling capacitor. P-channel diode transistors and an n-channel equalizing transistor control the voltage on the coupling capacitor.