Drive Circuit Eliminates Transformer Auxiliary Winding
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Solution Overview
Problem
Existing drive circuits for switching power source apparatuses require an auxiliary winding in transformers, increasing costs due to the need for additional components and complex configurations to power controllers.
Innovation Solution
A drive circuit that employs a series connection of a normally-on high-side switch and a normally-off low-side switch, utilizing a capacitor connected to a DC power source to supply power to a controller, eliminating the need for an auxiliary winding by rectifying and smoothing AC voltage through diodes and resistors to generate a control signal for the switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an auxiliary winding is added to the transformer to power the controller, then the controller can be powered reliably, but the cost and device complexity increase
Solution Approach 1:
The invention extracts the controller power supply function from the transformer's auxiliary winding and relocates it to the switching element itself. By utilizing the switching element's inherent characteristics (normally-on state for high-side switch), the power supply function is separated from the transformer structure, eliminating the need for auxiliary windings while maintaining reliable controller operation.
Solution Approach 2:
The switching element is given multiple functions: it serves both as the main power switching component and as the power source for the controller. The normally-on high-side switching element continuously provides power to the controller during operation, eliminating the need for a dedicated auxiliary winding and reducing overall system complexity.
2Reliability
If an auxiliary winding and rectifying-smoothing circuit are added, then the controller can be powered, but the manufacturing cost increases
Solution Approach 1:
The invention removes the auxiliary winding component from the transformer and the associated rectifying-smoothing circuitry, extracting the power supply function and implementing it through the switching element's inherent characteristics. This reduction in component count directly lowers manufacturing costs while maintaining controller operation capability.
Solution Approach 2:
The switching element serves itself by providing power to the controller through its own operational characteristics. The normally-on state of the high-side switching element automatically generates the necessary power without requiring external auxiliary components, reducing both component count and manufacturing complexity.
3Reliability
If a startup circuit is added to power the controller during startup, then the controller can operate during startup, but the device complexity and cost increase
Solution Approach 1:
The invention prepares the power supply path in advance by designing the switching element to be normally-on during startup. This preliminary configuration allows the controller to receive power immediately when the power source is activated, eliminating the need for separate startup circuits while ensuring reliable controller operation from the moment the system powers up.
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 reduces the cost of the switching power source apparatus by eliminating the need for an auxiliary winding and simplifies the power supply to the controller, ensuring reliable operation without a startup circuit, while maintaining efficient voltage regulation.
Implementation Method 1
a capacitor (C2) connected to a second end of the rectifier and a first end of the DC power source and serving as a power source for the controller
Implementation Method 2
a rectifier having a first end connected to a connection point of the high-side and low-side switches
Data Source
AI summary
A drive circuit drives a normally-on high-side switch Q1 and a normally-off low-side switch Q2 that form a series circuit connected in parallel with a DC power source. The drive circuit includes a controller 10 that outputs a control signal to turn on/off the high- and low-side switches, a rectifier D2 having a first end connected to a connection point of the high- and low-side switches, a capacitor C2 that is connected to a second end of the rectifier and a first end of the DC power source and serves as a power source for the controller, and a driver (A1, AND1, Q3, Q4) that turns on/off the high- and low-side switches according to the control signal from the controller and a voltage from the capacitor.