LED constant-current drive circuit
AssigneeShenzhen Fuxinya Technology Development Co., Ltd
InventorsYuan Gao, Yubo Qiao
Life of this patent
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Abstract
An LED constant-current drive circuit includes a BUCK circuit consisting of a transformer T1, a diode D9, a capacitor C5 and a field effect transistor Q1; a voltage limiting circuit consisting of a resistor R1, a diode D8, a capacitor C1, a resistor R3, a triode Q2, a zener diode DZ1 and a diode D10; and a current limiting circuit consisting of a resistor R4, a triode Q3, a triode Q4 and a resistor R2. When the transistor Q1 is turned on, a current flows through a primary side of the transformer T1 and an LED load, and then flows through the transistor Q1 and the resistor R2, and then flows back to a negative electrode of a power supply. When the transistor Q1 is turned off, the current flows through the primary side of the transformer T1, the LED load and the diode D9, thus forming a loop.
Claims8
An LED (light emitting diode) constant-current drive circuit, comprising:
- a BUCK circuit consisting of a transformer (T1), a diode (D9), a capacitor (C5) and a field effect transistor (Q1);
- a voltage limiting circuit consisting of a resistor (R1), a diode (D8), a capacitor (C1), a resistor (R3), a triode (Q2), a zener diode (DZ1) and a diode (D10);
- and
- a current limiting circuit consisting of a resistor (R4), a triode (Q3), a triode (Q4) and a resistor (R2),
- wherein when the field effect transistor (Q1) is turned on, a current flows through a primary side of the transformer (T1) and an LED load, and then flows through the field effect transistor (Q1) and the resistor (R2), and then flows back to a negative electrode of a power supply, and when the field effect transistor (Q1) is turned off, the current flows through the primary side of the transformer (T1), the LED load and the diode (D9), thus forming a loop,
- wherein a homonymous terminal at a primary side of the transformer (T1) is connected with a positive electrode of a power supply, the other terminal at the primary side of the transformer (T1) is connected with an anode of an LED load, a cathode of the LED load is connected with an anode of the diode (D9) and a drain electrode of the field effect transistor (Q1), a positive electrode and a negative electrode of the capacitor (C5) are respectively connected with the anode and the cathode of the LED load, a cathode of the diode (D9) is connected with the positive electrode of the power supply, a homonymous terminal at a secondary side of the transformer (T1) is connected with an anode of the diode (D8) and one end of the capacitor (C1), the other end at the secondary side of the transformer (T1) is connected with a source electrode of the field effect transistor (Q1), the source electrode of the field effect transistor (Q1) is connected with a negative electrode of the power supply via the resistor (R2), a gate electrode of the field effect transistor (Q1) is connected with the other end of the capacitor (C1), an emitter of the triode (Q2), a cathode of the diode (D10), one end of the resistor (R4) and an emitter of the triode (Q3), a base of the triode (Q3) is connected with the other end of the resistor (R4) and a collector of the triode (Q4), a collector of the triode (Q3) is connected with the source electrode of the field effect transistor (Q1) and a base of the triode (Q4), an emitter of the triode (Q4) is connected with the negative electrode of the power supply, a collector of the triode (Q2) is connected with a cathode of the diode (D8), one end of the resistor (R1) and one end of the resistor (R3), the other end of the resistor (R1) is connected with the positive electrode of the power supply, a base of the triode (Q2) is connected with the other end of the resistor (R3), an anode of the diode (D10) and a cathode of the zener diode (DZ1), and an anode of the zener diode (DZ1) is connected with the negative electrode of the power supply.
Dependencies are inferred from the claim text.