Transformerless Hot Surface Igniter Controller Using Half-Cycle Pulse Modulation
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Solution Overview
Problem
Existing power control methods for low voltage heating devices, such as hot surface igniters, require expensive transformers and complex controllers to manage uncontrolled AC currents, and lack flexibility in pulse modulation, leading to inefficiencies and potential damage to loads.
Innovation Solution
A pulse modulation method using mains half-cycle pulses as a single power unit, allowing for flexible control of AC power delivery with variable duty cycles, ensuring full polarity symmetry and precise power management, implemented through a transformerless controller that adjusts to input voltage and frequency, utilizing a microcontroller for dynamic power adjustment and flame sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If transformers and complex controllers are used to manage uncontrolled AC currents, then power control capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the transformer component from the power control system. By using a transformerless design with solid-state switching devices (triacs) that directly control AC power delivery through pulse modulation, the system achieves power control capability without requiring complex magnetic components and their associated control circuitry.
Solution Approach 2:
The patent replaces the mechanical/magnetic transformer-based power control system with an electronic solid-state switching system. Triacs are used to switch AC power in controlled pulses, substituting the need for transformers and mechanical controllers with semiconductor-based pulse width modulation technology.
2Reliability
If transformers are used for voltage transformation, then voltage matching is improved, but energy losses increase
Solution Approach 1:
The patent removes the transformer from the system entirely, eliminating transformer core losses, copper losses, and other energy dissipation mechanisms inherent in magnetic voltage transformation. Voltage matching is achieved through direct AC pulse delivery at the required voltage level without intermediate transformation.
Solution Approach 2:
The patent converts the potentially harmful uncontrolled AC current into a beneficial controlled feature by using the full-wave AC waveform in pulse width modulation. The AC nature of the power source is leveraged to achieve efficient power delivery with natural zero-crossing current interruption, turning what was previously a problem (uncontrolled AC current) into the mechanism for efficient power control.
3Adaptability or versatility
If pulse width modulation is used for power control, then power adjustment flexibility is improved, but controller complexity increases
Solution Approach 1:
The patent employs periodic AC half-cycle pulses as the fundamental power delivery unit. By modulating the width and timing of these periodic AC pulses, the system achieves flexible power adjustment. The natural periodicity of the AC waveform simplifies the control logic compared to generating pulses from DC, reducing controller complexity while maintaining adaptability.
Solution Approach 2:
The patent controls power delivery by changing temporal parameters of AC pulses (pulse width, pulse timing, duty cycle) rather than requiring complex voltage or current regulation. This parameter-based control approach provides flexible power adjustment through simple timing control of solid-state switches, avoiding the need for complex analog regulation circuits.
4Device complexity
If asymmetric half-cycle control is used, then power control simplicity is improved, but polarity symmetry and load safety deteriorate
Solution Approach 1:
The patent deliberately introduces symmetry into the control scheme by treating positive and negative half-cycles equally. Both half-cycles are subjected to the same pulse width modulation logic, ensuring that an even number of half-cycles are delivered in each control period. This symmetric treatment of opposite polarity half-cycles prevents DC offset and magnetic saturation while maintaining control simplicity through unified control logic.
Data Source
Figure 1~4
AI summary
The present invention proposes a hot surface igniter (HSI) controller which is transformerless and which is capable of delivering power from a 120/240 VAC RMS mains voltage, for example, to a load whose nominal operational voltage is equivalent to 24VAC RMS, for example, sinusoidal full wave AC Voltage. The controller provides an impulse range which is mainly designed to deliver power to hot surface igniter active loads with sufficient thermionic inertia and mass, and where the real voltage shape of supplied power is unimportant. This is achieved by supplying half-cycle pulses to the HIS that are separated by even number of half-cycles that are not supplied to the HIS. Thus the consecutively applied half-cycles are always of opposing polarity.