Flyback Converter Control Device for Constant Current Regulation
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Solution Overview
Problem
Existing flyback converter circuits, such as VIPer12A and VIPer22A, are complex and costly due to the use of numerous components for secondary regulation, including an optocoupler to separate feedback signals and additional transformer windings for high output voltages, which increases size and complexity.
Innovation Solution
A control device for a flyback converter that regulates constant output current using a transformer with an auxiliary primary winding to sense output voltage, a circuit to multiply signals representing primary current and input voltage, and a pulse width modulation driving circuit to adjust switch on and off times to maintain constant output current, reducing the need for additional components and windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secondary regulation with optocoupler and additional secondary windings is used, then feedback signal separation and high output voltage capability are improved, but device complexity and size increase
Solution Approach 1:
The patent extracts the optocoupler from the feedback path and replaces it with a resistive divider network that directly senses the output voltage. This eliminates the need for optical isolation components while maintaining the feedback function, thereby reducing device complexity and component count.
Solution Approach 2:
The auxiliary primary winding serves multiple functions: it provides feedback signal separation, enables high output voltage capability, and replaces the need for additional secondary windings. This multi-functional approach reduces the overall number of components and simplifies the transformer structure.
2Adaptability or versatility
If additional secondary windings are added for high output voltage, then high output voltage capability is improved, but device complexity and size increase
Solution Approach 1:
The auxiliary primary winding is designed to provide high output voltage capability through its coupling with the secondary winding, eliminating the need for additional secondary windings. This single winding performs the function that would otherwise require multiple windings, thereby reducing device complexity.
Solution Approach 2:
Instead of adding secondary windings to achieve high output voltage, the patent inverts the approach by using an auxiliary primary winding that couples to the secondary side. This inverted configuration achieves the same high voltage capability with fewer windings.
3Reliability
If secondary regulation components are used, then constant current regulation is improved, but cost and size increase
Solution Approach 1:
The patent merges the functions of multiple secondary regulation components into a unified control architecture. The auxiliary primary winding, combined with the multiplier circuit and comparator, integrates feedback signal separation, voltage sensing, and current regulation functions into a single coordinated system, reducing the number of discrete passive and active components.
Solution Approach 2:
The patent replaces complex mechanical/optical isolation systems (optocoupler) with electrical field-based sensing and signal processing circuits. The multiplier circuit and comparator provide constant current regulation through electrical signal manipulation rather than optical coupling, reducing component count and size.
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
The solution simplifies the flyback converter design by reducing the number of components and windings, lowering cost and size while maintaining constant current to high brightness LEDs, ensuring efficient and reliable operation.
Implementation Method 1
an auxiliary primary winding in a transformer in the current supply circuit adapted to sense a direct output voltage from a secondary winding in the transformer
Implementation Method 2
a first circuit structured to multiply a signal representative of current flowing in the primary winding and a second signal representative of an input voltage to the primary winding in the transformer and to output a multiplied signal that is representative of the product of the multiplication
Implementation Method 3
a second circuit coupled to the auxiliary primary winding and structured to compare the multiplied signal with the representative signal of the direct output voltage and to output a comparison signal
Implementation Method 4
a pulse width modulation driving circuit to adjust switch on and off times to maintain constant output current
Data Source
AI summary
A control device for regulating the constant output current of a flyback converter, the control device adapted to control the on time period and the off time period of a primary winding switch and including a first circuit adapted to multiply a first signal representative of current flowing through the primary winding and a second signal representative of an input voltage and outputting a signal representative of the multiplication, a second circuit adapted to compare the output signal of the first circuit and a third signal representative of the direct output voltage, the control device determining, on the basis of the output signal of the second circuit, the on time period and the off time period of the switch so that the output signal of the first circuit is equal to the signal representative of the direct output signal to have the output current of the flyback converter constant.