Regulator Voltage Reference Pre-Charge for Switching Noise Control
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Solution Overview
Problem
Existing power management systems induce transient voltage drops and current spikes when enabling disabled regulator voltage reference circuits, causing noise on power supply lines that can disrupt associated voltage regulators and circuits, and prior solutions like RC-filters consume significant area and often transfer noise to the ground plane.
Innovation Solution
A power management circuit that uses separate enable and pre-charge signals for regulator voltage reference circuits, incorporating a first current limiting transistor and a second current limiting transistor configured as a current mirror to limit initial current and minimize transient effects, allowing the regulator voltage reference circuit to ramp up smoothly and reduce noise on other circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a regulator voltage reference circuit is enabled by turning on a switch to interrupt current flow, then the circuit can be selectively activated to save power, but a transient voltage drop and current spike occur on the power supply line causing noise that disrupts other circuits
Solution Approach 1:
The patent applies preliminary action by pre-charging the output node of the regulator voltage reference circuit before fully enabling it. A pre-charge transistor is activated first to gradually charge the output capacitance, then the main enable switch is turned on. This sequence prevents sudden current spikes by preparing the circuit state in advance, thereby eliminating transient voltage drops and noise on the power supply line while maintaining selective power activation.
2Object-affected harmful factors
If RC-filters are used to mitigate switching noise, then noise on power supply lines is reduced, but significant circuit area is consumed and noise is transferred to the ground plane
Solution Approach 1:
The patent extracts the noise mitigation function from traditional RC-filter approaches and implements it directly within the regulator voltage reference circuit structure. By using a pre-charge transistor to control the charging current of the output capacitance, the noise reduction function is integrated into the enabling mechanism itself, eliminating the need for separate RC-filter components and their associated area consumption while avoiding ground plane noise transfer.
3Adaptability or versatility
If a switch is used to selectively enable the regulator voltage reference circuit, then independent control of multiple circuits is achieved, but sudden load induction causes transient voltage drops when enabling
Solution Approach 1:
The patent maintains independent circuit control through the enable switch while preserving voltage stability by introducing a pre-charge phase. Before the main enable switch closes, the pre-charge transistor activates to gradually charge the output capacitance. This preliminary action ensures that when the full load is connected, the voltage remains stable without transient drops, combining selective control capability with voltage stability.
4Use of energy by moving object
If current is suddenly interrupted to disable a regulator voltage reference circuit, then power savings are achieved, but the sudden load change induces noise on the main reference voltage signal
Solution Approach 1:
The patent applies periodic action by controlling the disabling process in two distinct phases. First, the pre-charge transistor is turned off to allow the output capacitance to discharge gradually. After a predetermined time delay, the main enable switch is opened to fully disconnect the circuit. This staged periodic approach ensures that current interruption occurs progressively rather than suddenly, achieving power savings while minimizing noise generation on the reference voltage signal.
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 minimizes noise on other regulator voltage reference circuits during enabling, reduces power consumption, and avoids the area and cost constraints of external capacitors, effectively managing transient effects and maintaining circuit stability.
Implementation Method 1
a second current limiting transistor selectively configured as a current mirror with the first current limiting transistor
Data Source
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AI summary
A power management circuit generates a reference voltage and distributes it to a plurality of independently-enabled regulator voltage reference circuits, each of which generates a predetermined voltage for a voltage regulator. Separate enable signals and enable pre-charge signals are distributed to each regulator voltage reference circuit. As a regulator voltage reference circuit is enabled via its associated enable signal, an enable precharge signal is also asserted for an initial duration. Each regulator voltage reference circuit includes a voltage setting circuit and a first current limiting transistor in series and operative to interrupt current to the voltage setting circuit when the regulator voltage reference circuit is disabled. A second current limiting transistor is configurably configured as a current mirror with the first current limiting transistor, and a pre-charge bias current from a current source passes through the second transistor. This limits the current through the first transistor and into the voltage setting circuit for the initial duration. After the initial duration, the current mirror is disabled and the first transistor is rendered fully conductive.