Insulated Switching Power Supply Using Pulse Transformer for Clamp Switch
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Solution Overview
Problem
Existing insulated switching power supply devices using p-type channel FETs as clamp switches suffer from high switching losses and require high-cost, large-size drive transformers due to the need for high inductance, which is not suitable for applications requiring high power and efficiency.
Innovation Solution
The use of a pulse transformer to transmit turn-on/turn-off timing for driving an n-type channel MOSFET as the clamp switch, eliminating the need for a high inductance drive transformer and enabling zero voltage switching, while a multiple transformer configuration minimizes size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a p-type channel FET is used as a clamp switch, then the device can operate with voltage clamping, but the switching loss increases and the device size and cost increase due to requiring a high inductance drive transformer
Solution Approach 1:
The patent changes the channel type of the MOSFET from p-type to n-type, which fundamentally alters the electrical parameters including on-resistance, input capacitance, and switching characteristics. This parameter change enables the use of a pulse transformer with much lower inductance requirements, thereby reducing switching losses and eliminating the need for large, expensive drive transformers while maintaining voltage clamping functionality.
2Reliability
If a high inductance drive transformer is used to drive the clamp switch, then the clamp switch can be properly controlled, but the device size and cost increase
Solution Approach 1:
By changing from p-type to n-type MOSFET, the gate charge requirements and driving voltage characteristics change, allowing the use of a pulse transformer with significantly lower inductance. This reduces the transformer size and weight while maintaining reliable clamp switch control through the modified driving parameters.
Solution Approach 2:
The patent replaces the expensive, large-size high inductance drive transformer with a smaller, lower-cost pulse transformer that has lower inductance. The n-type MOSFET's characteristics enable this substitution while maintaining adequate driving capability for the clamp switch.
3Productivity
If an n-type channel MOSFET is used as the clamp switch, then switching loss is reduced and efficiency is improved, but a drive transformer with high inductance is required which increases size and cost
Solution Approach 1:
The patent modifies the driving parameters by using a pulse transformer with lower inductance specifically designed for n-type MOSFET gate characteristics. This parameter optimization reduces the transformer volume while maintaining the high switching frequency operation and power capacity enabled by the n-type device.
Solution Approach 2:
The patent optimizes the driving waveform dynamics by adjusting the pulse transformer parameters to match the n-type MOSFET's switching characteristics, enabling fast switching transitions with reduced voltage spikes and improved efficiency without requiring excessive transformer inductance.
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 configuration achieves high circuit efficiency and power capacity with reduced size and cost, allowing the use of low-withstand-voltage transistors and effective zero voltage switching, enhancing efficiency and reducing noise.
Implementation Method 1
a pulse transformer transmitting at least a pulse edge signal
Implementation Method 2
a main transformer including a primary coil formed on a primary circuit side... and a secondary coil formed on a secondary circuit side so as to transmit power from the primary circuit side to the secondary circuit side
Data Source
Figure 1
Figure 2(a)~2(e)
Figure 3
AI summary
An insulated switching power supply device (104) includes a main transformer (T1) having a primary coil (n1) on a primary circuit side and a secondary coil (n2) on a secondary circuit side. On the primary circuit side are disposed an input smoothing capacitor (C2), a switching control circuit (1), a high-side driver (3), a low-side power switch (Q1), a high-side power switch (Q7), capacitors (C5,C6), and edge signal-generating circuits (5,6). A symmetrical control half bridge converter is thus provided. The secondary circuit side has a voltage clamping circuit (2) including a clamp capacitor (C1), a clamp switch (Q2) and a diode (D6).