Switching Power Supply Current Detection via Transformer Secondary Voltage
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Solution Overview
Problem
Switching power supply devices require multiple sensors for current and voltage detection, leading to complex configurations, power losses, and slowed PWM processes due to concurrent PWM and control processes in microcomputers.
Innovation Solution
A switching power supply device utilizing a current transformer for current detection, where the output current is calculated based on the voltage of the secondary side of the transformer, reducing the number of sensors and simplifying the circuit configuration, allowing for accurate current estimation and improved response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors (current sensor, shunt resistor) are used for current detection, then detection accuracy is improved, but device complexity and power loss increase
Solution Approach 1:
The patent extracts the current detection function from traditional sensors and implements it using the existing current transformer already present in the switching power supply circuit. The control unit calculates primary current based on secondary current from the transformer, eliminating the need for separate current sensors and shunt resistors.
Solution Approach 2:
The current transformer serves multiple functions: it provides galvanic isolation, enables current detection, and its secondary current is reused for calculating primary current. This multi-functional use reduces the need for additional components while maintaining detection accuracy.
2Measurement precision
If current sensor is used for current detection, then detection capability is improved, but device complexity increases
Solution Approach 1:
The patent removes the current sensor from the circuit and extracts the current detection capability from the existing current transformer. The control unit computes primary current from secondary current measurements, eliminating complex sensor hardware while preserving detection functionality.
3Measurement precision
If shunt resistor is used for current detection, then current measurement is achieved, but power loss increases
Solution Approach 1:
The patent removes the shunt resistor from the circuit and extracts current measurement capability from the current transformer's secondary side. This eliminates the continuous power dissipation associated with shunt resistors while maintaining accurate current measurement through transformer-based sensing.
4Device complexity
If PWM process and control process are performed concurrently in the same microcomputer, then integration is improved, but PWM process speed decreases
Solution Approach 1:
The patent segments the microcomputer's processing into distinct PWM process and control process sections. The PWM process operates independently at high speed for pulse generation, while the control process runs separately for calculations and monitoring, preventing mutual interference and maintaining PWM speed.
Solution Approach 2:
The patent implements periodic execution of control processes at specific intervals without interfering with the continuous PWM pulse generation. The control unit performs calculations during designated control cycles while the PWM unit maintains its high-frequency operation, achieving both integration and speed.
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 reduces the number of sensors, minimizes power losses, and simplifies the system, enabling smaller, lighter, and less costly designs while ensuring accurate current calculation and rapid response to input voltage changes.
Implementation Method 1
a current transformer arranged on a front stage of the switching circuit; a second voltage detecting circuit configured to detect a voltage of a secondary side of the current transformer
Data Source
AI summary
A system simplification can be achieved by reducing the number of sensors required to detect currents and voltages when an output current is estimated. A switching power supply device 6 includes a current transformer 12, a switching circuit 13, a rectifying circuit 15, a smoothing circuit 16, an input voltage detecting circuit 18, a control part 19, an output voltage detecting circuit 22 and a PWM signal generating part 30. The control part 19 calculates a duty rate and an average value of voltage of the secondary side voltage of the current transformer 12 detected by the input voltage detecting circuit 18 based on a waveform of the detected voltage. The control part 19 calculates an output current lo based on the calculated duty rate, the calculated average value of voltage and an output voltage Vo detected by the output voltage detecting circuit 22.