Bidirectional Switch Driving for Lower ZVS Heat Loss
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Solution Overview
Problem
Existing switch driving devices fail to sufficiently suppress heat generation in bidirectional switches due to energy consumption from inherent capacitances during zero voltage switching, leading to inefficiencies in switching power supplies.
Innovation Solution
A switch driving device configuration that performs individual zero voltage switching control for each switch element, where one element is kept on while the other is turned off, and zero voltage switching control is applied at specific voltage thresholds to minimize energy storage in capacitances, thereby reducing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If both switch elements are turned on simultaneously when voltage across the bidirectional switch becomes 0V, then zero voltage switching control is achieved, but energy stored in inherent capacitances is consumed causing heat generation
Solution Approach 1:
The patent divides the bidirectional switch into two separate switch elements (first and second switch elements) with individual control. Instead of controlling them as a single unit, each element is independently switched based on voltage polarity detection, allowing separate optimization of their switching timing to avoid simultaneous turn-on and reduce capacitance energy loss.
Solution Approach 2:
The patent detects the polarity of voltage across each switch element before switching occurs. By preliminarily identifying which element has positive voltage and which has negative voltage, the control device can prepare the appropriate switching sequence in advance, ensuring that only one element turns on at a time and avoiding the harmful simultaneous turn-on condition.
2Loss of energy
If individual zero voltage switching control is performed for each switch element, then switching losses are reduced, but control complexity increases
Solution Approach 1:
The patent utilizes the inherent voltage polarity information already present across the switch elements during normal operation. The control device simply detects this existing polarity state and responds accordingly, rather than requiring complex external synchronization signals or additional control infrastructure. This self-service approach reduces control complexity while achieving individual zero voltage switching.
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 effectively reduces switching losses and heat generation in bidirectional switches, enhancing the efficiency and reliability of switching power supplies by minimizing energy consumption during transitions.
Implementation Method 1
voltages reverse to each other are applied to inherent capacitances of the respective switch elements 510 and 520
Implementation Method 2
energy stored in the respective inherent capacitances is consumed by the switch elements 510 and 520. Thus, it is difficult to suppress the heat generation of the bidirectional switch X
Data Source
AI summary
Disclosed are a switch driving device, in which individual zero voltage switching control of a first switch element and a second switch element forming a bidirectional switch is performed, and a switching power supply including a primary winding to which an alternating-current input voltage is applied, a secondary winding electromagnetically coupled to the primary winding, the bidirectional switch connected in series with the primary winding, a resonance capacitor connected in parallel with at least one of the bidirectional switch and the primary winding, a full-wave rectifier circuit that performs full-wave rectification of an induced voltage occurring in the secondary winding, a smoothing capacitor that smooths output of the full-wave rectifier circuit, and the switch driving device that drives the bidirectional switch. The alternating-current input voltage is directly converted into a direct-current output voltage by extracting a flyback voltage or a forward voltage and the flyback voltage from the secondary winding.