Switching Power Supply Control Using a Dual-Use Current Sense Terminal
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Solution Overview
Problem
Existing switching power supply devices face challenges in adjusting switching frequency control characteristics and balancing power efficiency and output ripple without requiring additional external terminals or increasing costs, particularly in the light load range.
Innovation Solution
A switching power supply device with a transformer, a switching element, and a power control semiconductor device that includes a current-voltage conversion element, a period signal generation circuit, a current detection circuit, and a complementary current circuit, which uses a complementary resistor to adjust switching frequency and ripple without an additional external terminal for resistor connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an additional external terminal is added to change switching frequency control characteristics, then adaptability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent makes the existing current detection terminal (CS) serve dual purposes: its original function of detecting current and a new function of allowing external resistance connection to adjust switching frequency characteristics. This eliminates the need for a separate adjustment terminal while maintaining adaptability.
Solution Approach 2:
The power control IC is designed to accept an external resistance connected to the current detection terminal, enabling the same terminal to perform both current sensing and frequency characteristic adjustment functions, thereby reducing terminal count without sacrificing adaptability.
2Loss of energy
If power efficiency is increased in light load range, then energy consumption is reduced, but output ripple increases
Solution Approach 1:
The patent introduces a light load detection circuit that dynamically switches between two operating modes: PWM mode for medium-heavy loads and burst mode for light loads. This dynamic operation allows the system to optimize power efficiency during light loads while providing a mechanism to control ripple through external resistance adjustment.
Solution Approach 2:
The patent allows external resistance connection to the current detection terminal to change the reference voltage for burst operation. By adjusting this resistance, users can modify the threshold at which burst operation starts, thereby controlling the trade-off between power efficiency and output ripple according to specific application requirements.
3Adaptability or versatility
If external resistance is connected to adjust switching frequency characteristics, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent enables the current detection terminal to serve dual purposes: original current detection and new frequency characteristic adjustment through external resistance connection, eliminating need for separate adjustment components.
Solution Approach 2:
The system uses its existing current detection infrastructure to provide additional functionality. The same terminal and associated circuitry that detect current are also used to accept external resistance for frequency adjustment, making the system self-sufficient and reducing external component requirements.
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
Enables flexible adjustment of switching frequency control characteristics and power efficiency/output ripple trade-offs without additional terminals, improving efficiency and reducing ripple as needed, while maintaining cost-effectiveness.
Implementation Method 1
a transformer for voltage conversion that includes a primary-side winding to which a direct voltage is applied and a secondary-side winding
Implementation Method 2
a current-voltage conversion element that is connected in series to the switching element and that converts a current flowing through the primary-side winding into a voltage
Data Source
AI summary
A switching power supply includes a transformer, a switching element connected to the primary-side winding, a power control semiconductor device that outputs a signal for performing ON/OFF control of the switching element, and a current-voltage conversion element connected to the switching element. The semiconductor device includes: a first terminal that receives a voltage/current corresponding to an output from the secondary side of the transformer; a second terminal that receives the voltage converted by the current-voltage conversion element; a period signal generation circuit that generates a signal for periodically turning on the switching element; a current detection circuit that generates a signal for turning off the switching element, based on a voltage/current at the first terminal and a voltage at the second terminal; and a complementary current circuit that outputs a complementary current to the second terminal. A complementary resistor is provided between the second terminal and the current-voltage conversion element.