PWM Controller with Temperature Compensation and Short Circuit Protection
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Solution Overview
Problem
Current charger circuits for handsets and digital cameras face issues such as low efficiency, high system cost, increased circuit board area, and undesirable harmonic wave and noise performance, particularly in the second type of charger design which uses a dual operational charge circuit, and the third type with ASIC design is costly and limited to few manufacturers.
Innovation Solution
A high-performance PWM controller with a short circuit mode circuit connected to both power supply and output driving circuit inputs, incorporating a temperature compensation circuit using a medium value multi-transistor resistor of negative temperature coefficient and a well resistor of positive temperature coefficient, eliminating the need for a voltage stabilization diode and enhancing short circuit protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual operational charge circuit is adopted on the secondary side of the transformer, then constant voltage and current control requirements are met, but system cost increases and circuit board area increases
Solution Approach 1:
The patent combines the PWM controller and power transistor into a single integrated circuit package, merging multiple functions (constant voltage control, constant current control, and power switching) into one compact unit. This integration eliminates the need for separate dual operational charge circuits on the secondary side, reducing circuit board area while maintaining control functionality through the integrated controller's internal circuitry.
2Device complexity
If an ASIC design with dedicated integrated circuit on the primary side is adopted, then constant voltage and current control is achieved without optical coupler, but system cost increases and harmonic wave performance deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the PWM controller monitors output conditions and adjusts switching duty cycle accordingly. The controller includes voltage detection and current detection circuits that provide feedback signals to regulate the power transistor switching, enabling the system to maintain constant voltage and current while reducing harmonic waves through active control rather than passive filtering.
3Device complexity
If RCC separated elements with self actuation control are adopted on the primary side, then circuit simplicity is achieved, but efficiency decreases and short circuit function is lost
Solution Approach 1:
The patent implements a self-service mechanism through the integrated PWM controller that automatically detects short circuit conditions and adjusts operating parameters without external intervention. The controller monitors voltage and current feedback signals, and when a short circuit is detected, it automatically enters protection mode by adjusting the duty cycle, eliminating the need for separate protection circuits while maintaining high efficiency through optimized switching control.
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 achieves higher efficiency, improved short circuit characteristics, reduced system output harmonic wave, and lower system cost, while maintaining constant voltage and current control, and allows for a more compact design by packaging the power transistor and controller in a single TO-94 package.
Implementation Method 1
an oscillator which includes a temperature compensation circuit adopting a medium value multi-transistor resistor of a negative temperature coefficient and a well resistor of a positive temperature coefficient
Data Source
AI summary
A PWM controller includes a short circuit mode circuit which has input ends connecting simultaneously to a power supply input end and an output end of an output driving circuit, and an oscillator which has a temperature compensation circuit that includes a medium value multi-transistor resistor of a negative temperature coefficient and a well resistor of a positive temperature coefficient. The invention also provides a charger circuit which includes the PWM controller set forth above and a constant voltage/current control circuit coupling with the PWM controller through a transformer. A system adopting the PWM controller circuit and charger circuit of the invention does not need a voltage stabilization diode now equipped in many conventional designs. The invention provides an improved short circuit protection and eliminates low frequency harmonic waves.