Modulating Input Device Using Linearized Transistor Output Stage
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Solution Overview
Problem
Existing signal conditioning circuits face challenges in processing AC power and analog DC control signals, particularly in achieving a zero output voltage using standard operational amplifiers, which are often expensive and unable to provide outputs to zero voltage, complicating the generation of control signals for actuators with varying power factors.
Innovation Solution
A circuit design incorporating a full wave rectifier, a differential operational amplifier, and a linearized transistor output stage that can provide an output signal capable of reaching zero voltage, allowing for efficient processing and modulation of control signals, even with standard, less expensive operational amplifiers, by configuring the amplifier as a differential amplifier and using a resistor network to enhance voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a standard operational amplifier is used to process control signals, then the circuit is simpler and cheaper, but the output cannot reach zero voltage
Solution Approach 1:
A transistor output stage is introduced as an intermediary between the operational amplifier and the final output. The transistor acts as a mediator that can drive the output voltage to zero, overcoming the limitation of standard operational amplifiers while keeping the op-amp itself simple and inexpensive.
Solution Approach 2:
The output stage is segmented into two independent parts: the operational amplifier for signal processing and the transistor for zero-voltage capability. This segmentation allows each component to be optimized independently - the op-amp for cost-effectiveness and the transistor for achieving zero output voltage.
2Use of energy by moving object
If a full wave rectifier is used, then the power factor is high (1.0), but there is no common ground for connecting analog DC control signals
Solution Approach 1:
The transistor output stage serves as an intermediary that bridges the gap between the full-wave rectifier's internal ground and the external control signal ground. It enables the control signals to be properly referenced while maintaining the high power factor benefits of full-wave rectification.
Solution Approach 2:
The circuit handles multiple voltage references simultaneously by operating in different voltage dimensions - the rectifier operates with its internal ground reference while the control circuit operates with an external ground reference, and the transistor stage coordinates between these different reference dimensions.
3Measurement precision
If an operational amplifier with zero output capability is used, then the signal processing is accurate, but the device cost increases
Solution Approach 1:
The signal processing function is segmented from the zero-voltage output function. The operational amplifier handles the accurate signal processing, while the transistor handles the zero-voltage output requirement. This allows using a standard, inexpensive operational amplifier rather than a costly specialized amplifier.
Solution Approach 2:
The transistor acts as an intermediary that preserves the accuracy of the operational amplifier's output while adding the capability to reach zero voltage. The transistor is driven by the op-amp's output and translates it to a final output that can reach zero, maintaining signal integrity.
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 solution enables the effective modulation of actuator outputs with a higher power factor, reducing the VA rating requirements and allowing for the use of lower-rated, cheaper transformers, while ensuring accurate and zero-capable signal processing for control signals, thereby improving system efficiency and cost-effectiveness.
Implementation Method 1
a full wave rectifier (57) and having a rectified output
Implementation Method 2
an operational amplifier (26) configured as a differential amplifier with a first input for a first voltage between a supply ground input of the rectifier and a device ground output of the rectifier
Implementation Method 3
a linearized transistor output stage (45) having an input connected to an output of the operational amplifier (26) and having an output that can go to zero
Data Source
Figure 1
Figure 2
AI summary
A circuit that receives AC power for rectification and analog DC control signals for processing. Two voltages may be noted. A first voltage may be between a supply ground and an internal device ground of a rectifier. A second voltage may be between a terminal of an input control signal source and the internal device ground. To get a control signal value, one may need a differential of those two voltages that can be accomplished with an operational amplifier configured as differential amplifier. A range of an input control signal may be from zero to a particular magnitude of voltage. A reasonably priced operational amplifier might not have an ability provide an output to zero. However, a linearized transistor output stage, having an output that can go to zero, may be connected to an output of the operational amplifier so as to effectively provide an output that goes to zero.