High-Voltage Generator Using Auxiliary Coil Feedback
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Solution Overview
Problem
Existing high-voltage generators for image-forming apparatuses face challenges in achieving rapid output transient response and minimizing power loss while using a minimum number of transformer coils, and they struggle to provide outputs with different polarities using the same printed circuit board.
Innovation Solution
A high-voltage generator design utilizing a PNP-type bipolar junction transistor, a transformer with a primary, secondary, and auxiliary coil, and a voltage detection signal generator to produce a voltage control signal for regulating the oscillating amplitude of the AC voltage on the primary coil, eliminating the need for a separate voltage detection coil and allowing polarity changes by reversing diodes in the secondary rectifier/multiplier unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a voltage divider with high-impedance resistors is used to generate the feedback signal, then the power loss is reduced, but the output transient response becomes very slow
Solution Approach 1:
The patent introduces an auxiliary coil as an intermediary element that couples the primary and secondary sides of the transformer. This auxiliary coil generates a feedback signal that is proportional to the secondary output voltage but with appropriate impedance levels, thereby mediating between the high-impedance requirement for low power loss and the low-impedance requirement for fast transient response
Solution Approach 2:
The patent replaces the traditional voltage divider circuit (which uses resistors to divide voltage) with an electromagnetic coupling mechanism through the auxiliary coil. This substitution eliminates the need for high-impedance resistors while maintaining the feedback function, thereby resolving the contradiction between power loss and transient response speed
2Speed
If the impedance of the voltage-dividing resistors is reduced to improve output transient response, then the transient response improves, but considerable power loss occurs
Solution Approach 1:
The auxiliary coil acts as an intermediary that transfers energy and signal between the primary and secondary sides without requiring direct resistive coupling. This allows the feedback signal to be generated with appropriate impedance characteristics for fast transient response while avoiding the power loss associated with low-impedance voltage dividers
Solution Approach 2:
The patent substitutes the resistive voltage division mechanism with an electromagnetic induction mechanism through the auxiliary coil. This substitution enables the system to achieve fast transient response through low impedance coupling while minimizing power loss through the high efficiency of electromagnetic energy transfer
3Measurement precision
If a separate voltage detection coil is added to generate the feedback signal, then the feedback signal accuracy is improved, but the transformer coil count and manufacturing cost increase
Solution Approach 1:
The auxiliary coil is designed to serve multiple functions: it provides electromagnetic coupling for energy transfer between primary and secondary sides, generates the feedback signal through induced voltage, and enables voltage regulation control. This multi-functionality eliminates the need for a separate voltage detection coil while maintaining feedback signal accuracy
Solution Approach 2:
The patent merges the functions of the voltage detection coil and the energy transfer coil into a single auxiliary coil. By combining these functions, the design reduces the total number of transformer coils from four (primary, secondary, voltage detection, and energy transfer) to three (primary, secondary, and auxiliary), thereby reducing manufacturing complexity and cost
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 design enhances output transient response, reduces power loss, and enables the generation of outputs with different polarities using a single printed circuit board, while minimizing transformer coil count and manufacturing costs.
Implementation Method 1
The AC current on the base of the switch device 16 is provided through the auxiliary coil N13 whose voltage is induced by the primary coil N11
Implementation Method 2
the oscillating voltage on the primary coil N11 is amplified by the secondary coil N12
Implementation Method 3
the oscillating voltage on the primary coil N11 is amplified by the secondary coil N12 and thus a high-level AC voltage is induced across the secondary coil N12
Implementation Method 4
the high-level AC voltage is converted by a secondary rectifier/multiplier unit 13 into a high-level DC output voltage Vout
Data Source
AI summary
A high-voltage generator includes a high-voltage transformer having a primary coil, a secondary coil, and an auxiliary coil, and a PNP bipolar junction transistor. Based on the self-oscillation theory of a LC oscillator, an oscillating voltage is generated across the primary coil. The oscillating voltage is amplified to a high-level AC voltage through the secondary coil. One end of the auxiliary coil and an emitter of the transistor are coupled to an input DC voltage, and the other end of the auxiliary coil is connected to the base of the transistor through a RC circuit. One end of the primary coil is connected to the collector of the transistor, and the other end of the primary coil is connected to ground. Therefore, the primary coil can generate a voltage detection signal indicative of the voltage of the secondary output of the high-voltage generator by itself without using one extra voltage detection winding, so that a comparing unit can generate a control signal based on the comparison of the voltage detection signal and a reference signal to control the base current of the transistor to change the oscillating amplitude of the oscillating voltage, thereby controlling the voltage of the secondary output.