Motor Drive Circuit Kickback Voltage Suppression
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Solution Overview
Problem
Existing motor drive circuits face issues with voltage rise during kickback, leading to potential MOSFET destruction and unintended braking forces when the power supply voltage is reduced, and these solutions often require costly Zener diodes or result in inefficient energy dissipation.
Innovation Solution
A motor drive circuit with an H-bridge configuration, including P-channel and N-channel MOSFETs, parasitic diodes, and a control circuit that monitors power supply voltage, preventing MOSFET activation when the voltage falls below a threshold, thus avoiding loop formation and braking forces, and using regeneration diodes to manage kickback energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Zener diode is used to suppress voltage rise during kickback, then MOSFET destruction is prevented, but the circuit cost increases and the Zener diode size must increase with motor size
Solution Approach 1:
The patent extracts the voltage suppression function from a dedicated Zener diode component and implements it through the inherent characteristics of the H-bridge circuit topology and controlled MOSFET operation. The circuit uses the natural voltage relationships and switching sequences to limit kickback voltage without requiring an additional expensive Zener diode component.
Solution Approach 2:
The H-bridge circuit components (MOSFETs, diodes, capacitors) perform multiple functions: they control motor operation, manage kickback energy, and provide voltage suppression. This multi-functionality eliminates the need for dedicated protection components like large Zener diodes, reducing overall circuit cost and complexity.
2Loss of energy
If the H-bridge circuit allows loop formation during kickback, then energy is dissipated, but unintended braking forces occur when power supply voltage is reduced
Solution Approach 1:
The patent implements dynamic control of the H-bridge circuit based on real-time detection of power supply voltage conditions. The control circuit monitors voltage levels and adjusts MOSFET switching states accordingly, enabling the circuit to adapt between different operational modes (energy dissipation vs. preventing braking) based on current conditions.
Solution Approach 2:
The control circuit uses feedback from voltage detection to determine whether to allow loop formation for energy dissipation or to prevent it to avoid unwanted braking. This feedback mechanism enables intelligent decision-making about kickback energy management based on the current power supply state.
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
Effectively suppresses voltage rise during kickback events, preventing MOSFET destruction and braking forces at a lower cost without relying on large Zener diodes, ensuring efficient energy dissipation and maintaining motor operation.
Implementation Method 1
energy accumulated in the motor coil 10 works to keep the electric current flowing. For that reason, the electric current flows through the parasitic diode 13d, the motor coil 10 and the parasitic diode 12d. In other words, a kickback is caused.
Implementation Method 2
the electric current flows through the parasitic diode 13d, the motor coil 10 and the parasitic diode 12d
Implementation Method 3
the MOSFETs 11 and 12 are turned on when the voltage Vm on the power supply line 21 rises enough so that a voltage between a gate and a source of each of the MOSFETs 11 and 12 exceeds a threshold voltage
Data Source
AI summary
This invention provides a motor drive circuit, which makes it possible to prevent braking when a power supply voltage is lower than a predetermined voltage while suppressing at a low cost a rise in a voltage on a power supply line when a kickback occurs. The motor drive circuit is formed to include first and second power supply lines connected with and shunted from a power supply, an H-bridge circuit, and a means to control the H-bridge circuit. The means controls the H-bridge circuit so that a regeneration path is not created in the H-bridge circuit when the power supply voltage is lower than a predetermined voltage.