TWI862438B - Buck converter with soft handover - Google Patents

Abstract

A buck converter with soft handover, applied to high-power light-emitting diodes and electrically connected to high-power light-emitting diodes, an input power source, and a switching device, comprises a buck circuit and a snubber circuit. The buck circuit includes a first diode and a first inductor, where the first diode is coupled to the input power source, the switching device, and the first inductor, and the first inductor is coupled to the high-power light-emitting diodes and the switching device. The snubber circuit comprises a capacitor, a second inductor, a second diode, and a third diode, where the capacitor is connected to the switching device, the first inductor, the second diode, and the third diode, the second inductor is coupled to the high-power light-emitting diodes, the first inductor, and the third diode, and the second diode is coupled to the input power source, the high-power light-emitting diodes, and the third diode. This effectively reduces switching energy losses.

Description

Soft-cut buck converter

The present invention relates to a buck converter, and more particularly to a soft-cut buck converter capable of reducing switching energy loss.

Please refer to FIG. 1, which is a conventional floating output buck converter having an inductor L and a diode D electrically connected to a power source P, a light-emitting diode E, and a switch Q. The inductor L is electrically connected between the light-emitting diode E and the switch Q, and the diode D is electrically connected between the inductor L and the power source P. The circuit structure of this converter is simple, and therefore it is widely used in driving systems for medium and high power lighting light-emitting diodes.

Please refer to FIG. 2A and FIG. 2B. There are two switching modes for this converter, namely switch Q is on or off. This converter only has two switching states, so between on and off, a hard switching situation will be formed, causing the voltage of switch Q to rise too quickly, resulting in low conversion efficiency, obvious energy loss, and increased electromagnetic interference.

To solve the above problems, the present invention provides a soft-switching buck converter that can effectively reduce the loss of switching energy and reduce the emission energy of electromagnetic interference, thereby effectively improving power efficiency.

An embodiment of the present invention provides a soft-cut buck converter, which is applied to a high-power light-emitting diode. The soft-cut buck converter can be electrically connected between the high-power light-emitting diode, an input power source and a switching switch. The soft-cut buck converter includes: a buck circuit, which is electrically connected to the high-power light-emitting diode, the input power source and the switching switch. The buck circuit has a first diode and a first inductor. The first diode is electrically connected to the input power source, the switching switch and the first inductor. The first inductor is electrically connected to the high-power light-emitting diode. The high-power light-emitting diode and the switching switch are electrically connected; and a buffer circuit is electrically connected to the input power supply, the switching switch and the step-down circuit. The buffer circuit has a capacitor, a second inductor, a second diode and a third diode. The capacitor is connected to the switching switch, the first inductor, the second diode and the third diode. The second inductor is electrically connected to the high-power light-emitting diode, the first inductor and the third diode. The second diode is electrically connected to the input power supply, the high-power light-emitting diode and the third diode.

In one embodiment, the cathode of the first diode is electrically connected to the input power source, and the anode of the first diode is electrically connected to the switching switch and the first inductor.

In one embodiment, the switching switch is an N-type metal oxide semi-conductor field effect transistor, the source of the switching switch is grounded, and the drain of the switching switch is electrically connected to the first inductor and the anode of the first diode.

In one embodiment, the cathode of the second diode is electrically connected to the input power source and the high-power light-emitting diode, and the anode of the second diode is electrically connected to the third diode.

In one embodiment, the cathode of the third diode is electrically connected to the second diode and the capacitor, and the anode of the third diode is electrically connected to the second inductor.

In another embodiment of the present invention, a soft-cut buck converter is applied to a high-power light-emitting diode. The soft-cut buck converter can be electrically connected between the high-power light-emitting diode, an input power source, and a switching switch. The soft-cut buck converter includes: a buck circuit electrically connected to the input power source and the switching switch. The buck circuit has a first diode and a first inductor. The first diode is electrically connected to the input power source and the switching switch. The first inductor is electrically connected to the high-power light-emitting diode and the switching switch. ; and a buffer circuit electrically connected to the input power supply, the switching switch and the step-down circuit, the buffer circuit having a capacitor, a second inductor, a second diode and a third diode, the capacitor is electrically connected to the switching switch, the first inductor, the second diode and the second inductor, the second inductor is electrically connected to the third diode and the second diode, the second diode is electrically connected to the input power supply, the high-power light-emitting diode and the second inductor, and the third diode is electrically connected to the high-power light-emitting diode, the first inductor and the second inductor.

In one embodiment, the cathode of the first diode is electrically connected to the input power source, and the anode of the first diode is electrically connected to the switching switch and the first inductor.

In one embodiment, the switching switch is an N-type metal oxide semi-conductor field effect transistor, the source of the switching switch is grounded, and the drain of the switching switch is electrically connected to the first inductor and the anode of the first diode.

In one embodiment, the cathode of the second diode is electrically connected to the input power source and the high-power light-emitting diode, and the anode of the second diode is electrically connected to the second inductor.

In one embodiment, the cathode of the third diode is electrically connected to the second inductor, and the anode of the third diode is electrically connected to the high power light emitting diode and the first inductor.

As described above, the present invention can effectively reduce the loss of switching energy, reduce the emission energy of electromagnetic interference, and reduce the cost of setting up a heat dissipation structure by combining a buck circuit with a buffer circuit; thereby, it can effectively improve the low conversion efficiency of the traditional buck, thereby effectively improving the power efficiency.

In order to facilitate the description of the central idea of the present invention in the above invention content column, specific embodiments are used for illustration. Various objects in the embodiments are depicted according to the proportions, sizes, deformations or displacements suitable for the description, rather than being drawn according to the proportions of the actual components.

The directional terms mentioned in the present invention, such as "upper", "lower", "front", "back", "left", "right", "inner", "outer", "side", etc., are merely directions of the drawings; therefore, the directional terms used are used to illustrate and understand the present invention, rather than to limit the present invention, and it is necessary to explain them in advance.

Please refer to Figures 3 to 9. The present invention provides a soft-cut buck converter, which is applied to a high-power light-emitting diode Do. The soft-cut buck converter can be electrically connected between the high-power light-emitting diode Do, an input power Pin and a switching switch Q1. In the first embodiment of the present invention, the switching switch Q1 is an N-type metal oxide semi-conductor field effect transistor, and the source of the switching switch Q1 is grounded.

The soft-cut buck converter in the first embodiment of the present invention comprises:

A step-down circuit 10 is electrically connected to a high-power light-emitting diode Do, an input power source Pin and a switching switch Q1. The step-down circuit 10 has a first diode D1 and a first inductor Lo. The first diode D1 is electrically connected to the input power source Pin, the switching switch Q1 and the first inductor Lo. The first inductor Lo is electrically connected to the high-power light-emitting diode Do and the switching switch Q1. In the first embodiment of the present invention, the drain of the switching switch Q1 is electrically connected to the first inductor Lo and the anode of the first diode D1.

A buffer circuit 20 is electrically connected to the input power Pin, the switching switch Q1 and the step-down circuit 10. The buffer circuit 20 has a capacitor Cr, a second inductor Lr _, a second diode D2 and a third diode D3. The capacitor Cr is connected to the switching switch Q1, the first inductor Lo, the second diode D2 and the third diode D3. The second inductor Lr is electrically connected to the high-power light-emitting diode Do, the first inductor Lo and the third diode D3. The second diode D2 is electrically connected to the input power Pin, the high-power light-emitting diode Do and the third diode D3. In the first embodiment of the present invention, the first diode The cathode of the first diode D1 is electrically connected to the input power Pin, the anode of the first diode D1 is electrically connected to the switching switch Q1 and the first inductor Lo, the cathode of the second diode D2 is electrically connected to the input power Pin and the high-power light-emitting diode Do; the anode of the second diode D2 is electrically connected to the third diode D3; the cathode of the third diode D3 is electrically connected to the second diode D2 and the capacitor Cr, and the anode of the third diode D3 is electrically connected to the second inductor Lr.

Please refer to the waveforms in Figures 4 and 9 corresponding to the process from _t0 to _t1 . When the switching switch Q1 is turned on, the voltage Vgs1 of the input power Pin excites the high-power light-emitting diode Do and the first inductor Lo. At this time, the capacitor Cr and the second inductor Lr resonate, and the voltage Vcr of the capacitor Cr gradually increases, and the second inductor Lr oscillates for half a cycle.

Please refer to the waveforms of FIG. 5 and FIG. 9 corresponding to the process from t ₁ to t _2. When the voltage Vcr of the capacitor Cr increases to be equal to the voltage Vgs1 of the input power Pin, it means that the capacitor Cr is fully charged, and the current iCr of the second inductor Lr passes through the third diode D3 and the second diode D2, causing the current iD3 and the current iD2 to change, and the second inductor Lr will be in a discharge state, and the current iCr of the second inductor Lr will gradually decrease to 0.

Please refer to the waveforms in FIG. 6 and FIG. 9 corresponding to the process from t ₂ to t _3. When the switching switch Q1 is still turned on, the current of the input power Pin will still pass through the high-power LED Do and the first inductor Lo (current iLo), while the voltage Vcr of the capacitor Cr remains unchanged, and the current iCr of the capacitor Cr is 0.

Please refer to the waveforms of FIG. 7 and FIG. 9 corresponding to the process from t ₃ to t _4. When the switching switch Q1 is closed, the current iLo of the first inductor Lo needs to be demagnetized, so the current will move toward the capacitor Cr and pass through the second diode D2 (current iD2), and the voltage Vcr of the capacitor Cr will drop rapidly to be in a discharge state. At this time, the voltage Vds1 of the switching switch Q1 will gradually increase; it can be seen that the loss can be effectively reduced; it should be particularly noted that the larger the capacitance of the capacitor Cr, the slower the voltage Vds1 of the switching switch Q1 in this state rises, which can reduce the loss of switching energy.

Please refer to the waveforms in FIG. 8 and FIG. 9 corresponding to the process from t ₄ to t _0+sw . The switching switch Q1 is still turned off, and when the capacitor Cr is discharged, the current will move toward the first diode D1, and the current iD1 of the first diode D1 will be turned on.

Referring to FIG. 10 , a soft-cut buck converter is provided in the second embodiment of the present invention. The difference between the second embodiment of the present invention and the first embodiment is that the electrical connection positions of the second inductor Lr and the third diode D3 are different. The capacitor Cr is electrically connected to the switching switch Q1, the first inductor Lo, the second diode D2 and the second inductor Lr. The second inductor Lr is electrically connected to the third diode D3 and the second diode D2. The second diode D2 is electrically connected to the input power Pin, the high power LED Do and the The second inductor Lr is electrically connected, and the third diode D3 is electrically connected to the high-power light-emitting diode Do, the first inductor Lo and the second inductor Lr; in the second embodiment of the present invention, the cathode of the second diode D2 is electrically connected to the input power Pin and the high-power light-emitting diode Do, and the anode of the second diode D2 is electrically connected to the second inductor Lr; the cathode of the third diode D3 is electrically connected to the second inductor Lr, and the anode of the third diode D3 is electrically connected to the high-power light-emitting diode Do and the first inductor Lo.

It should be particularly noted that, in the second embodiment of the present invention, when the switching switch Q1 is turned on or off, the various waveforms generated corresponding to different operating states are the same as those of the first embodiment, as shown in FIG. 9 .

Therefore, the present invention can effectively reduce the loss of switching energy, reduce the emission energy of electromagnetic interference, and reduce the cost of setting up a heat dissipation structure by combining the step-down circuit 10 with the buffer circuit 20, so as to effectively improve the power efficiency.

The above embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Any modifications or changes that do not violate the spirit of the present invention are within the scope of protection of the present invention.

<Knowledge> P: Power supply E: LED Q: Switch L: Inductor D: Diode <Present invention> Do: High power LED Pin: Input power Q1: Switch 10: Buck circuit D1: First diode Lo: First inductor 20: Buffer circuit Cr: Capacitor Lr: Second inductor D2: Second diode D3: Third diode Vcr: Voltage Vgs1: Voltage Vds1: Voltage iCr: Current iD1: Current iD2: Current iD3: Current iLo: Current

FIG. 1 is a circuit diagram of a conventional floating output buck converter. FIG. 2A is a schematic diagram of a conventional floating output buck converter in which the switching switch is in the on state. FIG. 2B is a schematic diagram of a conventional floating output buck converter in which the switching switch is in the off state. FIG. 3 is a circuit diagram of the first embodiment of the present invention. FIG. 4 is an operation state diagram (I) of the first embodiment of the present invention, indicating that the switching switch is on. FIG. 5 is an operation state diagram (II) of the first embodiment of the present invention, indicating that the switching switch is on. FIG. 6 is an operation state diagram (III) of the first embodiment of the present invention, indicating that the switching switch is on. FIG. 7 is an operation state diagram (IV) of the first embodiment of the present invention, indicating that the switching switch is off. FIG8 is an operation state diagram (V) of the first embodiment of the present invention, indicating that the switching switch is closed. FIG9 is a waveform diagram of the first embodiment of the present invention. FIG10 is a circuit diagram of the second embodiment of the present invention.

Do: High power LED

Pin: Input power

Q1: Switching switch

10: Step-down circuit

D1: First diode

Lo: First Inductor

20: Buffer circuit

Cr: Capacitance

Lr: Second inductor

D2: Second diode

D3: The third diode

Claims (10)

A soft-cut buck converter is applied to a high-power light-emitting diode. The soft-cut buck converter can be electrically connected between the high-power light-emitting diode, an input power source and a switching switch. The soft-cut buck converter comprises: A buck circuit electrically connected to the high-power light-emitting diode, the input power source and the switching switch. The buck circuit has a first diode and a first inductor. The first diode is electrically connected to the input power source, the switching switch and the first inductor. The first inductor is electrically connected to the high-power light-emitting diode and the switching switch; and A buffer circuit electrically connects the input power source, the switching switch and the step-down circuit. The buffer circuit has a capacitor, a second inductor, a second diode and a third diode. The capacitor is connected to the switching switch, the first inductor, the second diode and the third diode. The second inductor is electrically connected to the high-power light-emitting diode, the first inductor and the third diode. The second diode is electrically connected to the input power source, the high-power light-emitting diode and the third diode. A soft-switched buck converter as described in claim 1, wherein the cathode of the first diode is electrically connected to the input power source, and the anode of the first diode is electrically connected to the switching switch and the first inductor. A soft-cut buck converter as described in claim 2, wherein the switching switch is an N-type metal oxide semi-conductor field effect transistor, the source of the switching switch is grounded, and the drain of the switching switch is electrically connected to the first inductor and the anode of the first diode. A soft-cut buck converter as described in any one of claims 1 to 3, wherein the cathode of the second diode is electrically connected to the input power source and the high-power light-emitting diode, and the anode of the second diode is electrically connected to the third diode. A soft-cut buck converter as described in claim 4, wherein the cathode of the third diode is electrically connected to the second diode and the capacitor, and the anode of the third diode is electrically connected to the second inductor. A soft-cut buck converter is applied to a high-power light-emitting diode. The soft-cut buck converter can be electrically connected between the high-power light-emitting diode, an input power source and a switching switch. The soft-cut buck converter comprises: A buck circuit electrically connected to the input power source and the switching switch. The buck circuit has a first diode and a first inductor. The first diode is electrically connected to the input power source and the switching switch. The first inductor is electrically connected to the high-power light-emitting diode and the switching switch; and A buffer circuit is electrically connected to the input power source, the switching switch and the step-down circuit. The buffer circuit has a capacitor, a second inductor, a second diode and a third diode. The capacitor is electrically connected to the switching switch, the first inductor, the second diode and the second inductor. The second inductor is electrically connected to the third diode and the second diode. The second diode is electrically connected to the input power source, the high-power light-emitting diode and the second inductor. The third diode is electrically connected to the high-power light-emitting diode, the first inductor and the second inductor. A soft-switched buck converter as described in claim 6, wherein the cathode of the first diode is electrically connected to the input power source, and the anode of the first diode is electrically connected to the switching switch and the first inductor. A soft-cut buck converter as described in claim 7, wherein the switching switch is an N-type metal oxide semi-conductor field effect transistor, the source of the switching switch is grounded, and the drain of the switching switch is electrically connected to the first inductor and the anode of the first diode. A soft-cut buck converter as described in any one of claims 6 to 8, wherein the cathode of the second diode is electrically connected to the input power source and the high-power light-emitting diode, and the anode of the second diode is electrically connected to the second inductor. A soft-cut buck converter as described in claim 9, wherein the cathode of the third diode is electrically connected to the second inductor, and the anode of the third diode is electrically connected to the high-power light-emitting diode and the first inductor.

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