Double-Ended Isolated DC-DC Converter Using Low-Inductance Pulse Transformers
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Solution Overview
Problem
Existing double-ended isolated DC-DC converters have complex circuit configurations and large size due to the need for high inductance signal transmission transformers, which complicates the design and increases size and weight, especially when transmitting switching frequency signals.
Innovation Solution
The implementation of a compact and lightweight double-ended isolated DC-DC converter using pulse transformers with low inductance to transmit pulse edge signals, allowing for complementary timing of switch and synchronous rectifier operations, and incorporating delay circuits to prevent short circuits and back-flow currents, thereby simplifying the circuit and reducing component costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a signal transmission transformer with high inductance is used to transmit switching frequency signals, then the signal transmission reliability is improved, but the size and weight of the converter are increased
Solution Approach 1:
The patent changes the signal transmission approach from using a high-inductance transformer at switching frequency to using a low-inductance transformer with pulse edge signals. By transmitting only the rising and falling edges of PWM signals rather than continuous switching frequency signals, the required inductance is dramatically reduced, allowing for a much smaller and lighter transformer while maintaining signal transmission reliability.
2Reliability
If a signal transmission transformer with high inductance is used to transmit switching frequency signals, then the signal transmission reliability is improved, but the device complexity is increased
Solution Approach 1:
The patent simplifies the circuit by changing the signal transmission method to pulse edge signaling, which requires a low-inductance transformer instead of a high-inductance transformer. This parameter change reduces the transformer specifications and simplifies the overall circuit configuration while maintaining the ability to reliably transmit control signals from the primary side to the secondary side.
3Loss of energy
If the synchronous rectifier is driven with complementary timing to the primary side switch, then the power conversion efficiency is improved, but the risk of short-circuit current due to timing shift is increased
Solution Approach 1:
The patent applies preliminary action by introducing a delay circuit that causes the synchronous rectifier to turn on slightly after the primary side switch turns off. This delayed timing prevents the risk of short-circuit current that would occur if both switches were off simultaneously, while still maintaining complementary operation to maximize power conversion efficiency by minimizing the period when current flows through the parasitic diode.
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 solution reduces the size and weight of the converter while maintaining high efficiency by using pulse transformers with low inductance and delay circuits to manage timing and prevent short circuits and back-flow currents, resulting in a more compact and cost-effective design.
Implementation Method 1
The alternating current power is transmitted from a primary side circuit to a secondary side circuit of the main transformer T1 by the main transformer T1
Implementation Method 2
a first pulse transformer arranged to transmit the first turn-off edge signal and the first turn-on edge signal to the secondary side, a second pulse transformer arranged to transmit the second turn-off edge signal and the second turn-on edge signal to the secondary side
Data Source
AI summary
In a double-ended isolated DC-DC converter, by using a main transformer and first and second pulse transformers, a first power switch of a primary side circuit and a first synchronous rectifier of a secondary side circuit are driven with complementary timing, and a second power switch of the primary side circuit and a second synchronous rectifier of the secondary side circuit are driven with complementary timing. A first turn-off edge signal and a first turn-on edge signal generated in a primary side control circuit are transmitted to the secondary side via the first pulse transformer so as to generate a driving signal of the first synchronous rectifier. In addition, a second turn-off edge signal and a second turn-on edge signal generated in a primary side circuit are transmitted to the secondary side via the second pulse transformer so as to generate a driving signal of the second synchronous rectifier.