Switching Power Supply Circuit Cost Reduction
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Solution Overview
Problem
Conventional switching power supply circuits require insulated elements like photocouplers for feedback, increasing costs due to their higher cost compared to non-insulated components.
Innovation Solution
A switching power supply circuit using a non-insulated rectifying element instead of a photocoupler, with a configuration that includes a switch, energy transmitting element, output generation circuit, output voltage detection circuit, transmission circuit, control circuit, and rectifying element, allowing for cost-effective stabilization of output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photocoupler is used as a transmission circuit for feedback, then output voltage stabilization is achieved, but cost increases due to the insulated element requirement
Solution Approach 1:
The patent extracts the insulation function from the transmission circuit by removing the photocoupler. The feedback signal transmission is separated from the insulation requirement, allowing the use of non-insulated transistors while maintaining electrical isolation through circuit topology design where the feedback loop operates on the secondary side and controls the primary side switching through a non-insulated path.
Solution Approach 2:
The patent replaces the expensive photocoupler with inexpensive non-insulated transistors (BJT or MOSFET). These standard transistors are much cheaper than insulated photocouplers while still achieving the required feedback function. The circuit accepts that these transistors operate in a high-voltage environment but uses their low cost to reduce overall system cost.
2Ease of manufacture
If a non-insulated element is used in the transmission circuit, then cost is reduced, but the circuit configuration becomes more complex to ensure proper voltage handling
Solution Approach 1:
The patent applies equipotentiality by carefully designing the voltage references and biasing circuits for the non-insulated transistors. The emitters of the PNP transistors are connected to specific voltage potentials that ensure proper operation. The circuit establishes equipotential connections between corresponding nodes on primary and secondary sides to simplify the non-insulated feedback path while maintaining proper voltage handling.
Solution Approach 2:
The patent introduces intermediary elements such as diodes and resistors that mediate the voltage and current between the non-insulated transistors and the high-voltage nodes. These intermediary components protect the transistors from voltage spikes and ensure proper signal transmission without requiring insulation, thus managing circuit complexity while enabling cost reduction.
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 enables cost reduction by replacing expensive insulated components with non-insulated ones, maintaining stable output voltage without the need for insulated feedback elements, thus providing a low-cost non-insulated power supply circuit.
Implementation Method 1
a rectifying element which is connected between the transmission circuit and the control circuit and outputs the transmission signal only in a direction from the transmission circuit to the control circuit
Implementation Method 2
an energy transmitting element which transmits, as energy, the input voltage applied through the switch
Implementation Method 3
an output generation circuit which smoothes the energy transmitted by the energy transmitting element and outputs the smoothed energy through two output terminals as an output voltage
Data Source
AI summary
A switching power supply circuit, which includes: a switch; a coil serving as an energy transmitting element; and a capacitor serving as an output generation circuit that outputs, as an output voltage, the energy transmitted from the coil. The switching power supply circuit also includes an output voltage detection circuit that generates a detection signal according to the output voltage; a PNP transistor serving as a transmission circuit that outputs a transmission signal according to a value of the detection signal; and a controller that controls the switch according to the transmission signal. The switching power supply circuit further includes a diode serving as a rectifying element connected between the transmission circuit (PNP transistor) and the controller.