AC-to-DC Converter BJT Base Current Control
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Solution Overview
Problem
Existing AC-to-DC power converters using BJTs as power switches face challenges in accurately detecting inductor current and compensating for delay time due to limitations in base current control and recovery currents, leading to peak errors and inefficiencies.
Innovation Solution
An AC-to-DC power converter with a control IC that includes a base-current-setting circuit and a shifting circuit to detect the resistance value of a current-setting resistor, generating a current-controlling signal to set the base current and compensate for delay time by shifting voltages across a sensing resistor, allowing correct detection of inductor current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a BJT is used as a power switch with fixed base current control, then the device complexity is reduced, but the measurement precision of inductor current detection deteriorates due to inability to compensate for delay time
Solution Approach 1:
The patent applies preliminary action by detecting the resistance value of the current-setting resistor in advance and storing it in a memory circuit before switching operations. This pre-detection and storage of base current parameters enables the control circuit to compensate for delay time effects during subsequent inductor current detection, improving measurement precision without significantly increasing device complexity.
Solution Approach 2:
The patent introduces an intermediary mechanism by using a sensing resistor and associated voltage detection circuitry as a mediator between the BJT switching operation and the control IC. This intermediary circuit measures the voltage across the sensing resistor, which correlates to inductor current, and enables accurate current detection by compensating for delay time through pre-stored resistance values.
2Adaptability or versatility
If the base current is set by an external current-setting resistor, then the adaptability of the power converter is improved, but the device complexity increases due to additional pins and external components
Solution Approach 1:
The patent merges the base current setting function with the inductor current detection function by using the same sensing resistor and pin for both purposes. The control IC detects the resistance value of the current-setting resistor through the existing sensing circuitry and uses this information to determine both the base current and compensate for delay time, thereby achieving adaptability without requiring additional pins.
Solution Approach 2:
The patent applies universality by designing the sensing resistor and associated circuitry to serve multiple functions: it acts as both the current-setting element for base current control and the sensing element for inductor current detection. This multi-functional design allows the power converter to achieve adaptability while minimizing the number of external components and pins required.
3Ease of operation
If the control IC provides base current within a fixed range, then the ease of operation is improved, but the manufacturing precision of base current control deteriorates when optimal base current is outside the fixed range
Solution Approach 1:
The patent applies dynamics by making the base current control adaptive rather than fixed. The control IC dynamically adjusts the base current based on the detected resistance value of the current-setting resistor. This dynamic adjustment mechanism allows the system to maintain ease of operation with automatic control while achieving high manufacturing precision by adapting the base current to the specific application requirements.
Data Source
AI summary
An AC-to-DC power converter with a BJT as a power switch can set a base current of the BJT by a current setting resistor which is in the outside of a control integrated circuit. Since an output current and a recovery current of the BJT are injected into a sensing resistor, the AC-to-DC power converter can correctly detect an inductor current thereof from the sensing resistor.