Adjustable Shunt Regulator Circuit Using Bipolar Transistors
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Solution Overview
Problem
Existing bandgap shunt regulator circuits are not adjustable for voltage greater than 1.22 volts and suffer from additional offset error and increased power consumption due to the use of error amplifiers.
Innovation Solution
An adjustable shunt regulator circuit with two parallel current paths, each containing a bipolar transistor, where a MOS transistor is connected to a high impedance node, and a resistor divide circuit provides the output, eliminating the need for an error amplifier by using resistor ratios to adjust the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an error amplifier is used to adjust output voltage, then voltage adjustability is improved, but offset error and power consumption increase
Solution Approach 1:
The patent extracts and removes the error amplifier component from the regulator circuit. By eliminating this component, the source of offset errors is removed, while voltage adjustability is maintained through alternative means (resistor-based voltage division and feedback network).
Solution Approach 2:
The patent replaces the active error amplifier (electronic amplification system) with a passive resistor-based voltage division and feedback network. This substitution eliminates the need for high-gain amplification while achieving the same voltage regulation function through passive components that do not introduce offset errors.
2Adaptability or versatility
If an error amplifier is used to adjust output voltage, then voltage adjustability is improved, but power consumption increases
Solution Approach 1:
The error amplifier is extracted and removed from the circuit, eliminating its power consumption. The voltage adjustability function is transferred to passive resistor networks that consume minimal power compared to active amplification circuits.
Solution Approach 2:
The patent uses simple, low-cost passive resistor components instead of complex, power-hungry active error amplifier circuits. These passive components achieve the same functional goal with significantly lower power consumption and simpler implementation.
3Stability of the object's composition
If a fixed bandgap reference circuit is used, then temperature stability is improved, but voltage adjustability is limited to 1.22V
Solution Approach 1:
The patent makes the voltage reference system multi-functional by adding a resistor-based voltage division network that can generate multiple output voltages from the same stable reference. This allows the circuit to maintain temperature stability while providing adjustable output voltages beyond the fixed 1.22V bandgap reference.
Solution Approach 2:
The patent introduces dynamic adjustability to the previously fixed bandgap reference circuit by incorporating variable resistor networks and feedback mechanisms. This allows the output voltage to be dynamically adjusted while the underlying reference maintains its temperature stability.
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 allows for adjustable output voltage without offset errors and reduced power consumption, achieving accuracy and efficiency by eliminating the need for error amplifiers.
Implementation Method 1
The emitter of transistor Q2 is larger than the emitter of transistor Q1. As an example shown in FIG. 1 the emitter of transistor Q2 is 16 times larger than the emitter of transistor Q1. As a result, transistor Q2 with the larger emitter area requires a smaller base-emitter voltage for the same current than for the transistor Q1. The delta between the base-emitter voltage of transistor Q1 and that of the transistor Q2 is amplified by a factor of about 10 and added to the base-emitter voltage of transistor Q1. The total of these two voltages add up to approximately 1.22v, which is the approximate bandgap of silicon at 0 degrees K. The circuit 10 has the benefit of the accuracy of the Vbe term which decreases at a rate of about −2 mV/C degree.
Implementation Method 2
A MOS transistor has a gate connected to the high impedance node, and a source and a drain.
Implementation Method 3
The resistor divide circuit has a first resistor connected in series with a second resistor at a first node. A feedback connects the first node to the bases of the bipolar transistors connected in common of the two current paths.
Data Source
AI summary
An adjustable shunt regulator circuit has two current paths in parallel, with each current path having a bipolar transistor therein with the bases of the bipolar transistors of the two current paths connected in common. One of the current paths has a high impedance node. A MOS transistor has a gate connected to the high impedance node, and a source and a drain. A resistor divide circuit is connected in parallel to the source and drain of the MOS transistor and provides the output of the regulator circuit. The resistor divide circuit has a first resistor connected in series with a second resistor at a first node. A feedback connects the first node to the bases of the bipolar transistors connected in common of the two current paths.