Darlington Bias Circuit for Analog Controller Static Power Reduction

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Solution Overview

Problem

The existing biasing circuits in power converter systems for analog controller integrated circuits result in significant static power loss, particularly during the start-up phase when high input voltages are used, as they continue to dissipate power even after the startup is complete.

Innovation Solution

A control circuit is introduced to selectively disable the bias resistors or potential divider network after the startup phase, ensuring that the startup voltage supply is disabled only when a stable operating voltage is available through alternate means, such as an auxiliary winding, thereby reducing static power losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a biasing circuit is used to generate supply voltage for the analog controller during startup, then the controller can be powered during the start-up phase, but significant static power loss occurs because the biasing circuit continues to dissipate power even after startup is complete

Engineering Contradiction:

Improvestartup power supply reliabilityVSAvoidstatic power loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The biasing circuit's operation is made dynamic through a control transistor that switches the circuit between active and disabled states. During startup, the transistor conducts to enable the biasing circuit to generate supply voltage. After startup completion detected by the control circuit, the transistor turns off to disable the biasing circuit, eliminating static power loss while maintaining startup reliability.

Inventive Principle:

Principle #15Dynamics

2Loss of energy

If the biasing circuit is disabled to reduce power loss, then static power consumption decreases, but the controller cannot be properly powered during the start-up phase

Engineering Contradiction:

Improvestatic power lossVSAvoidstartup power supply reliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

A control circuit provides feedback monitoring of the supply voltage to determine when startup is complete. This feedback signal controls the biasing transistor, ensuring the biasing circuit remains enabled during startup and is disabled only after successful startup, thus maintaining reliability while reducing power loss.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The biasing circuit is designed to self-regulate its operation through the control transistor that automatically switches based on the supply voltage level. The circuit serves itself by using its own output voltage to control its input switching element, eliminating the need for external control while ensuring proper startup and shutdown timing.

Inventive Principle:

Principle #25Self-service

3Power

If high voltage rectified DC supply is used during startup, then sufficient voltage is available to power the controller, but power dissipation is significantly higher compared to normal operating voltage

Engineering Contradiction:

Improvesupply voltage availabilityVSAvoidpower dissipation

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The biasing circuit operates periodically rather than continuously - it is activated only during the startup phase when high voltage is needed, and deactivated during normal operation when lower voltage suffices. This periodic operation reduces average power dissipation while maintaining sufficient power availability during the critical startup period.

Inventive Principle:

Principle #19Periodic action

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 implementation significantly reduces static power loss by disconnecting the high voltage rectified DC supply voltage path after startup, achieving an 82.7% improvement in power dissipation reduction compared to traditional methods.

Implementation Method 1

a second circuit that controls the selective generation by the first circuit, said second circuit coupled to receive the input voltage and the DC supply voltage and configured to compare the DC supply voltage to a threshold

Methodology Applied

Scientific EffectVoltage threshold comparison:

Implementation Method 2

A control circuit is introduced to selectively disable the bias resistors or potential divider network after the startup phase

Methodology Applied

Scientific EffectTransistor switching:

Data Source

PatentUS10897192B1Scheme to reduce static power consumption in analog controller based power converters requiring an external high voltage startup circuit

Publication Date: 2021.01.19 STMICROELECTRONICS INT NV

AI summary

A Darlington switch in series with a biasing circuit is biased in an ON state by default to generate a supply voltage for a controller integrated circuit chip during start-up. On powering up, the supply voltage for the controller integrated circuit chip rises. When the supply voltage exceeds a minimum operating voltage threshold, the controller integrated circuit chip is enabled for operation and an auxiliary supply circuit begins generating the supply voltage for the controller integrated circuit chip. The Darlington switch is turned OFF when the supply voltage being generated by the auxiliary circuit is sufficiently higher than a threshold associated with the minimum operating voltage threshold. The circuit for controlling ON/OFF state of the Darlington switch has a substantially lower static power dissipation than the biasing circuit.