Magnetic Stripe Data Transmission Driver PWM Current Slope Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional magnetic stripe data transmission (MST) drivers face challenges in controlling load current slopes and time durations, leading to high power consumption and inefficiency, with limited control over inductance and series resistance, resulting in unreliable signal transmission and increased noise due to high current slopes.
Innovation Solution
The implementation of a magnetic stripe data transmission driver using pulse width modulation (PWM) to control the current slopes of the load current through an inductive coil, allowing for programmable rising and falling slopes, reducing power loss during signal transmission and improving signal recognition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional MST drivers transmit magnetic signals using full bridge switch configuration with constant frequency pulses, then magnetic stripe data can be transmitted to card readers, but power consumption is high and current slope control is limited
Solution Approach 1:
The patent implements dynamic control of current slopes through PWM modulation of switch driving signals. The controller adjusts the duty cycle of PWM signals to dynamically control the rising and falling slopes of load current through the inductive coil, replacing the conventional fixed-frequency square wave approach. This enables adaptive current slope control that optimizes power consumption while maintaining reliable signal transmission.
Solution Approach 2:
The patent changes the operational parameters by introducing programmable current slope control through PWM. Instead of using fixed frequency and duty cycle, the system varies the duty cycle of PWM signals to control the rate of current change (di/dt) in the inductive coil. This parameter change enables independent control of current rising and falling slopes, resolving the contradiction between power efficiency and control flexibility.
2Speed
If high current slopes are used in conventional MST drivers, then signal transmission speed is improved, but noise increases and transmission reliability decreases
Solution Approach 1:
The patent uses dynamic PWM control to adjust current slopes adaptively. During signal transmission, the controller increases the PWM duty cycle to achieve steeper current slopes for faster signal transmission. During non-transient periods, it reduces the duty cycle to minimize noise and power consumption. This dynamic adjustment resolves the contradiction between transmission speed and reliability.
Solution Approach 2:
The patent employs periodic PWM switching to control the inductive coil current. By modulating the duty cycle of periodic PWM signals, the system achieves controlled current ramps that generate the necessary magnetic flux changes for signal transmission while limiting peak current slopes to reduce noise. The periodic nature of PWM allows precise control over the timing and magnitude of current changes.
3Device complexity
If conventional MST drivers use fixed duty ratio square wave signals, then circuit simplicity is maintained, but power loss during non-transient periods increases
Solution Approach 1:
The patent replaces fixed duty ratio square waves with variable duty cycle PWM signals. The controller adjusts the PWM duty cycle based on transmission requirements, using higher duty cycles during active signal transmission and lower duty cycles during idle periods. This periodic modulation with variable duty cycle reduces average power consumption while maintaining the ability to generate sufficient magnetic flux changes during transmission.
Solution Approach 2:
The patent changes the duty ratio parameter dynamically through PWM control. Instead of maintaining a fixed 50% duty ratio, the system varies the duty cycle to control the average current through the inductive coil. During non-transient periods, the reduced duty cycle minimizes power loss, while during transmission, the duty cycle is increased to ensure adequate signal strength, resolving the contradiction between simplicity and energy efficiency.
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 enables reliable and efficient magnetic signal transmission with reduced power consumption by controlling current slopes using PWM, minimizing power loss during non-transient periods and optimizing signal recognition.
Implementation Method 1
magnetic flux density of the inductive coil is varied according to the load current density, inductance value and the load current slope of the inductive coil which remotely induces a back electromagnetic force (Bemf) in a receiver of the card reader
Implementation Method 2
The MST driver transmits the magnetic signal to the card reader. In the transmission of the magnetic signal, magnetic flux density of the inductive coil is varied according to the load current density
Data Source
AI summary
A magnetic stripe data transmission (MST) driver and a method for driving the MST are disclosed. The MST driver is configured to transmit magnetic strip data comprising of streams of pulses. The MST driver comprises a pair of high side switches and a pair of low side switches. The pair of high side switches comprises a first switch and a second switch. The pair of low side switches comprises a third switch and a fourth switch. The first, second, third and fourth switches are arranged in a full bridge type configuration connected across a voltage source and a ground. An inductive coil is connected across outputs of the full bridge type configuration of the switches. The MST driver includes a switch driver configured to drive the pair of low side switches and the pair of high side switches under current slope control using pulse width modulation. The driven load current has a rising portion and a falling portion through the inductive coil in a forward direction or in a reverse direction with programmable load current rising and falling slopes to induce a recognizable back electromagnetic force at a receiver emulating the magnetic strip data during the load current rising and falling portions and to reduce power loss during time periods without signal transmission.