LED Drive Circuit DC Bus Voltage Control
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Solution Overview
Problem
Conventional LED drive circuits using silicon-controlled rectifier dimmers face inefficiencies due to large circuit losses and increased temperature from bleeder circuits, especially when the conduction angle is large, leading to suboptimal system performance.
Innovation Solution
The proposed solution involves controlling the direct current bus voltage to be constant during bleeding, with an adjustable desired value, to delay the turn-on time of the silicon-controlled rectifier dimmer when the conduction angle is large, ensuring the bus voltage is near the lighting voltage when the dimmer is turned on, thereby reducing the need for prolonged bleeder current sinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the conduction angle of the silicon-controlled rectifier dimmer is large, then the dimming control range is improved, but the direct current bus voltage when the dimmer is turned on is less than the lighting voltage of the LED load, requiring the bleeder circuit to sink a large current to raise the voltage, which results in large circuit loss and reduced system efficiency
Solution Approach 1:
The patent applies preliminary action by controlling the direct current bus voltage to rise in advance before the silicon-controlled rectifier dimmer is turned on. The voltage is raised to a predetermined value (greater than or equal to the lighting voltage of the LED load) prior to dimmer conduction, ensuring that when the dimmer turns on, the bus voltage is already sufficient to illuminate the LED load immediately, eliminating the need for the bleeder circuit to sink large current to raise the voltage.
Solution Approach 2:
The patent changes the parameter of direct current bus voltage by controlling it to follow a predetermined rise pattern. Instead of allowing the voltage to rise passively after the dimmer turns on, the system actively controls the voltage parameter to reach the required level beforehand, thereby changing the operational state from voltage-deficient to voltage-sufficient condition.
2Reliability
If the bleeder circuit sinks large current to raise the direct current bus voltage, then the LED load can operate, but the temperature of the circuit is increased due to heat generated by the bleeder circuit, which further affects the system performance
Solution Approach 1:
The patent applies preliminary action by pre-raising the direct current bus voltage to the required level before the silicon-controlled rectifier dimmer turns on. This ensures that when the dimmer conducts, the LED load receives sufficient voltage immediately and does not require the bleeder circuit to sink large current, thereby preventing excessive heat generation and temperature rise in the circuit.
3Loss of time
If the direct current bus voltage is controlled to be constant during bleeding, then the turn-on time instant can be delayed when the conduction angle is large, but the system requires precise control mechanisms to maintain the voltage
Solution Approach 1:
The patent employs feedback control where the control circuit monitors the direct current bus voltage and adjusts the bleeding process accordingly. The feedback mechanism ensures that the voltage is controlled to follow the predetermined rise pattern and reach the required level at the appropriate time, enabling precise control of the turn-on timing without excessive complexity.
Solution Approach 2:
The patent changes the parameter of direct current bus voltage by controlling it to follow a predetermined rise pattern. Instead of allowing the voltage to rise passively after the dimmer turns on, the system actively controls the voltage parameter to reach the required level beforehand, thereby changing the operational state from voltage-deficient to voltage-sufficient condition.
Data Source
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AI summary
There are provided a circuit module, a dimmable light emitting diode (LED) drive circuit and a control method. A direct current bus voltage during bleeding is controlled to be constant, and a desired value of the direct current bus voltage is adjustable, so that a turn-on time instant can be delayed in a case that the conduction angle is large, and the direct current bus voltage when the silicon-controlled rectifier dimmer is turned on can be near a lighting voltage. In this way, it is not required to sink a bleeder current from a direct current bus for a long time period after the silicon-controlled rectifier dimmer is turned on, effectively reducing the system loss, and improving the system efficiency.