Four-State Driver Reduces THD via Independent Discharge
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Solution Overview
Problem
Existing drivers for load circuits exhibit high total harmonic distortion (THD) and power factor, which need to be reduced to meet regulatory requirements.
Innovation Solution
A driver with an additional mode that blocks the supply current for a substantial time duration, allowing the storage circuit to discharge independently through the load circuit, thereby reducing THD and improving power factor, achieved through a switch circuit that controls the driver's states between charge, bypass, dependent discharge, and independent discharge modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the driver uses a conventional three-mode operation (storage unit bypassed, charged, or discharged with supply current), then the driver can provide basic load driving functionality, but the total harmonic distortion remains high and power factor needs improvement
Solution Approach 1:
The driver operation is segmented into four distinct modes instead of three: (1) storage unit bypassed, (2) storage unit charged by supply current, (3) storage unit discharged with supply current, and (4) storage unit discharged independently with supply current blocked. This segmentation allows the supply current to be completely decoupled from the load current during mode 4, eliminating the source of harmonic distortion while maintaining continuous load operation through the storage unit.
Solution Approach 2:
The driver operates in periodic cycles transitioning through the four modes, with the storage unit being charged during modes 2 and 3, and discharged during modes 3 and 4. The periodic blocking of supply current during mode 4 creates intervals of zero supply current, which eliminates harmonics during these intervals while the storage unit maintains continuous power delivery to the load.
2Object-generated harmful factors
If the supply current is blocked for substantial time duration to reduce THD, then the total harmonic distortion decreases and power factor improves, but the load circuit requires continuous current supply
Solution Approach 1:
The storage unit is charged in advance during modes 2 and 3 before the supply current is blocked in mode 4. This preliminary charging action ensures that sufficient energy is stored in the storage unit to maintain continuous load current supply during the period when the supply current is blocked, preventing any interruption in load operation.
Solution Approach 2:
The storage unit acts as an intermediary energy buffer between the supply circuit and the load circuit. During mode 4 when the supply current is blocked, the storage unit independently discharges to maintain continuous power delivery to the load, effectively mediating the discontinuous supply current and converting it into continuous load current.
Data Source
AI summary
Drivers (1-10) for driving load circuits (100) comprise supply circuits (1) for providing supply current signals from a mains source to the load circuits (100), storage circuits (2) for storing energy destined for the load circuits (100), and switch circuits (3-8) coupled with the storage circuit (2), the load circuit (100) and the supply circuit (1), and for switching the coupling among the storage circuits (2), the load circuit (100) and the supply circuit (1). The switched storage circuits (2) can, in charge states, be charged via the supply current signals, and in bypass states be bypassed, and in dependent discharge states be discharged via the load circuit (100) together with the supply current signals, and in independent discharge states be discharged via the load circuits (100) independently from the supply current signals for a substantial time duration. The drivers (1-10) may further comprise controllers (10) for controlling the switch circuits (3-8) for bringing the drivers (1-10) between two subsequent zero-crossings of signals supplied to the supply circuits (1) into the independent discharge state, the dependent discharge state, the bypass state, the charge state, the bypass state, the dependent discharge state and the independent discharge state, in this particular order. These drivers (1-10) show a reduced total harmonic distortion.