Clamp Circuit Stabilizes Reference Voltage in Series Regulators
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Solution Overview
Problem
Existing semiconductor integrated circuits for series regulators experience significant variations in noise levels and output voltages when switching output voltages, which is not effectively addressed by existing noise reduction techniques using MOS transistors or bandgap reference voltage circuits.
Innovation Solution
A semiconductor integrated circuit design that includes a control transistor, a control circuit, a reference voltage circuit, a current source circuit, and an operating-current stabilizing circuit with a clamp circuit to maintain stable operating current and reduce noise, utilizing bipolar transistors and a variable resistor to generate a variable reference voltage, and a low-pass filter to reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the resistance value of voltage dividing resistors is adjusted to generate multiple output voltages, then the regulator becomes applicable to various systems with different voltage requirements, but the noise level in the output voltage varies significantly with different output voltage settings
Solution Approach 1:
A clamp circuit is introduced as an intermediary component between the reference voltage circuit and ground. This clamp circuit includes a transistor whose base is connected to the reference voltage output node, collector to the power supply line, and emitter to ground. The clamp circuit acts as a mediator that stabilizes the operating point of the reference voltage circuit, preventing noise level variations when output voltage is switched by changing the voltage dividing resistor values.
Solution Approach 2:
The invention changes the operating parameters of the reference voltage circuit by introducing the clamp circuit that maintains a stable voltage at the reference voltage output node. This parameter stabilization ensures that the noise characteristics remain consistent across different output voltage settings, as the reference voltage circuit operates from a stable baseline regardless of the selected output voltage level.
2Object-affected harmful factors
If a low-pass filter is added between the reference voltage circuit and error amplifier to reduce noise, then the noise in the voltage output is reduced, but the circuit complexity increases and MOS transistors are used which are less advantageous for noise reduction compared to bipolar transistors
Solution Approach 1:
The invention extracts the noise reduction function from a complex low-pass filter circuit and implements it through a simpler clamp circuit configuration. By removing the need for complex filtering components and using a straightforward transistor-based clamp, the essential noise reduction capability is achieved with minimal circuit complexity addition.
Solution Approach 2:
The clamp circuit uses a simple transistor structure that is easier to implement and more effective for noise reduction than complex MOS-based low-pass filters. The solution favors a simpler, more direct approach using bipolar transistors which inherently provide better noise performance, avoiding the need for elaborate filtering circuits.
3Reliability
If a bandgap reference voltage circuit is used in a semiconductor integrated circuit for controlling a series regulator, then the reference voltage is generated with good stability, but the power supply circuit complexity increases to improve ripple rejection capability and existing solutions do not address output voltage switching issues
Solution Approach 1:
The clamp circuit is merged with the existing bandgap reference voltage circuit architecture. The transistor's base is connected to the reference voltage output node, effectively combining the reference voltage generation function with the noise stabilization function in a single integrated structure, rather than adding separate complex power supply circuits.
Solution Approach 2:
The clamp circuit serves multiple functions: it stabilizes the reference voltage operating point, reduces noise variations during output voltage switching, and maintains compatibility with bandgap reference circuits. This multi-functional approach eliminates the need for separate complex power supply circuits designed solely for ripple rejection.
4Object-affected harmful factors
If bipolar transistors are used in the series regulator circuit, then the noise performance is improved for systems sensitive to noise, but the circuit design becomes more challenging when addressing output voltage switching and noise level variations
Solution Approach 1:
The circuit is segmented into distinct functional blocks: the reference voltage circuit with its clamp circuit, the voltage dividing circuit for output voltage selection, and the error amplifier. This segmentation allows the bipolar transistor-based reference voltage circuit to optimize noise performance independently, while the voltage dividing circuit handles output voltage switching without interfering with the noise-critical reference voltage section.
Data Source
AI summary
A semiconductor integrated circuit includes a control transistor, a control circuit, a reference circuit, a current source, and a stabilizing circuit including a first transistor whose base is connected to a node to receive the reference voltage. The reference circuit includes series-connected second transistor and first and second resistors, third and fourth transistors and third and fourth resistors, and fifth and sixth transistors. The fifth transistor has connected base and collector, which base is connected to a base of the third transistor, the second transistor has a base connected to a node between third and fourth transistors, fourth and sixth transistors have bases connected to a first node between first and second resistors or a second node between second transistor and first resistor, a potential at the first or second node is the reference voltage, and a gain is determined depending on a resistance of the first resistor.