Active-Clamp Power Supply ZVS Detection Without Drain Sensing
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Solution Overview
Problem
In insulated AC-DC convertors with active clamp circuits employing zero voltage switching (ZVS) control, determining whether ZVS control is performed without directly monitoring the drain voltage is challenging, leading to noise generation and reduced conversion efficiency due to unnecessary energy losses.
Innovation Solution
The insulated power supply apparatus includes a power supply control semiconductor device with a ZVS determining circuit that assesses the drain side voltage of the switching element based on input voltages from current-voltage conversion elements, allowing for ZVS control determination without direct drain voltage monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If drain voltage is directly monitored to determine ZVS control, then measurement accuracy is improved, but device complexity increases due to high voltage resistance elements
Solution Approach 1:
The patent introduces an intermediary current-voltage conversion element that converts the drain voltage to a current signal, which is then converted back to a measurable voltage level. This intermediary conversion process allows accurate measurement of high drain voltage without requiring high voltage resistance elements, thus resolving the contradiction between measurement accuracy and device complexity
Solution Approach 2:
The patent changes the measurement parameter from direct voltage measurement to current measurement through a conversion element. By measuring the current flowing through the current-voltage conversion element and converting it back to voltage, the system achieves accurate drain voltage measurement while using only low voltage resistance elements, eliminating the need for complex high voltage components
2Device complexity
If voltage is divided by resistors to enable low voltage measurement, then device complexity is reduced, but energy loss increases due to current flowing to voltage dividing circuits
Solution Approach 1:
The patent replaces the passive resistor-based voltage division system with an active current-voltage conversion element. This substitution eliminates the continuous current flow through high-value resistors that causes energy loss, while still providing the necessary voltage scaling function. The conversion element only draws significant current during active conversion periods, dramatically reducing overall power loss
3Loss of energy
If impedance of voltage dividing circuit is increased to decrease current, then energy loss is reduced, but measurement accuracy deteriorates due to waveform corruption and timing shift
Solution Approach 1:
The patent introduces an intermediary current-voltage conversion element that acts as a buffer between the high impedance voltage dividing circuit and the measurement system. This intermediary provides a low impedance path during active measurement, preventing waveform corruption and timing shifts, while the high impedance circuit continues to minimize energy loss during idle periods
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 enables easy determination of ZVS control performance, reducing noise and energy losses, and enhancing the conversion efficiency of the power supply apparatus.
Implementation Method 1
a current-voltage conversion element connected between a source terminal of the switching element and a grounding point
Implementation Method 2
a transformer that converts voltage; a switching element connected in series with a primary side winding of the transformer
Implementation Method 3
the switching element includes a field effect transistor
Data Source
AI summary
An insulated power supply apparatus includes, a transformer; a switching element connected in series with a primary side winding of the transformer; an active clamp circuit connected between terminals of the primary side winding of the transformer; and a power supply control semiconductor device. The switching element includes a field effect transistor and a current-voltage conversion element is connected between a source terminal of the switching element and a grounding point. The power supply control semiconductor device includes the following, a first external terminal in which voltage according to a drain side of the switching element is input, a second external terminal in which voltage converted by the current-voltage conversion element is input, an on/off control circuit that performs turn-on and turn-off of the switching element, and a ZVS determining circuit that determines whether zero voltage switching control is performed.