TWI514730B - Ultra high step-down converter - Google Patents

Description

Low buck converter

The invention relates to a buck converter, in particular to a low voltage step which is simple in circuit design, easy to control, has a linearity in voltage conversion ratio, and can prevent an output load if a switch does not operate normally and does not generate a high voltage. converter.

Buck converters are known for use in digital circuits. For example, a 48 volt voltage bus in a network communication system provides a voltage of 3.3 volts or less. The existing method is to reduce the duty cycle of the pulse width control signal to 10% or lower, but this method is easy to cause. Switching losses, therefore, currently take two-stage buck, the first phase from 48 volts to 12 volts, and then 12 volts to 3.3 volts, 2.5 volts, 1.8 volts, 1.5 volts, 1.2 volts or 1 volt, but Therefore, many active switches and multiple control components are required, which is not only complicated in circuit design but also difficult to control.

Therefore, the lack of existing buck converters includes: complicated circuit design, difficult control, non-linear characteristics of voltage conversion ratio, and when switching failure or abnormal operation occurs, other switches will cause high voltage at the output when they are turned on. Unable to protect the output load.

Accordingly, it is an object of the present invention to provide a low buck converter that can protect an output load without providing a high voltage if the circuit design is simple, the control is easy, the voltage conversion ratio exhibits linear characteristics, and if the switch does not operate normally.

The low buck converter of the present invention is used to step down an input voltage of a power supply to an output voltage. The low buck converter includes a first switch, a second switch, a third switch, a coupled inductor, and an energy. Transfer capacitor and an output capacitor.

The first switch has a first input end, a first control end and a first output end, the first input end is coupled to the power source; the second switch has a second input end, a second control end, and a second output end coupled to the first output end, the second output end is grounded; one end of the energy transfer capacitor is electrically connected to the second input end; the coupled inductor has a first winding and a second winding, the dot end of the first winding is electrically connected to the other end of the energy transfer capacitor, and the non-tapping end of the first winding is electrically connected to the dot end of the second winding; the third switch has a third An input end, a third control end and a third output end, the third input end is coupled to the non-tapping end of the first winding and the striking end of the second winding, the third output end is grounded; the output capacitor is electrically The non-dot end of the second winding is connected.

The first control end of the first switch receives a wave width modulation signal to control whether the first switch is turned on or not, and the second control end of the second switch and the third control end of the third switch accept the wave width adjustment The reverse signal of the variable signal controls whether the second switch and the third switch are turned on or not, whereby the output capacitor generates an output voltage after the input voltage is stepped down.

The voltage conversion ratio of the low buck converter is in accordance with the following formula: The number of turns of the first winding is N1, the number of turns of the second winding is N2, V _o is an input voltage value, V _in is an output voltage value, and D is a duty cycle of the wave width modulation signal.

The function of the low buck converter of the invention is that the circuit design is simple, the control is easy, the conversion ratio has linear characteristics, and when any switch fails or does not operate normally, at the same time, other switches are turned on, and high voltage does not appear at the output end. It protects the output load.

100‧‧‧Low Buck Converter

1‧‧‧coupled inductor

C _B ‧‧‧ energy transfer capacitor

C _O ‧‧‧ output capacitor

11‧‧‧First winding

12‧‧‧second winding

N ₁ ‧‧‧Number of turns in the first winding

N ₂ ‧‧‧Number of turns in the second winding

Q ₁ ‧‧‧First switch

Q ₂ ‧‧‧Second switch

Q ₃ ‧‧‧third switch

V _in ‧‧‧ input voltage

V _O ‧‧‧Output voltage

Other features and advantages of the present invention will be apparent from the embodiments of the present invention, wherein: FIG. 1 is a circuit diagram illustrating an embodiment of the low buck converter of the present invention; FIGS. 2-8 are schematic views The current direction of the low buck converter of the present invention in different states is illustrated; FIG. 9 is a waveform diagram illustrating the wave width modulation signal and related signals of the low buck converter of the present invention; FIG. Waveform diagram illustrating the load enable signal, output voltage, and output current of the low buck converter of the present invention changed from 50% to 100% load; FIG. 13 is a waveform diagram illustrating the low buck converter of the present invention from 100 % is changed to load enable signal, output voltage and output current of 50% load; FIG. 14 is a graph illustrating the rated negative of the low buck converter of the present invention Load corresponding to conversion performance.

Referring to FIG. 1 and FIG. 2, in the embodiment of the present invention, the low buck converter 100 is configured to step down an input voltage V _in a power supply to an output voltage V _O , and the low buck converter 100 includes a first switch. Q ₁ , a second switch Q ₂ , a third switch Q ₃ , a coupled inductor 1 , an energy transfer capacitor C _B and an output capacitor C _O .

The first switch Q ₁ has a first input end, a first control end and a first output end, the first input end is coupled to the power source; the second switch Q ₂ has a second input end and a second control end And a second output end, the second input end is coupled to the first output end, the second output end is grounded; the end of the energy transfer capacitor C _{B is} electrically connected to the second input end; the coupled inductor 1 has a first winding 11 and a The second winding 12, the striking end of the first winding 11 is electrically connected to the other end of the energy transfer capacitor C _B , the non-injecting end of the first winding 11 is electrically connected to the striking end of the second winding 12; the third switch Q ₃ has a a third input end, a third control end and a third output end, the third input end is coupled to the non-tapping end of the first winding 11 and the striking end of the second winding 12, and the third output end is grounded; the output capacitor C _O electrically connected to the second winding 12 of the non-striking end; wherein the first switch Q ₁ of the first control terminal receiving a wave width modulation signal controls the first switch Q ₁ is turned on or not, the second switch Q ₂ of and two control terminal of the third switch Q ₃ of the third control terminal receiving the inverted signal of the pulse width modulation signal Whereby the control of the second switch and the third switch Q ₂ Q ₃ is turned on or not, and may generate the input voltage V _in a stepped-down output voltage V _O at the output capacitor C _O.

Referring to FIG. 2 to FIG. 8 together with FIG. 1, the first to seventh states of the present embodiment will be respectively described, and the relational expressions relating to the input voltage V _in and the DC output voltage V _{O will be} described.

Referring to Figure 2, a first state, the first switch Q ₁ is not turned on, the second switch and the third switch Q ₂ Q ₃ is not turned on, the first winding 11 of coupled inductor 1 and the second winding 12 is energized, and the first The currents of the winding 11 and the second winding 12 are slowly increased, and the voltage of the first winding 11 is as shown in Equation 1, wherein the voltage of the energy transfer capacitor C _B is V _CB .

In Formula 1, the number of turns of the first winding 11 is N ₁ , and the number of turns of the second winding 12 is N ₂ .

Referring to Figure 3, a second state, the first switch Q ₁ originally nonconductive, the second switch and the third switch Q ₂ Q ₃ is not turned on, however, pulse width modulation signal having this delay zone state (Dead time), The second switch Q ₂ and the third switch Q ₃ are turned on by the self diode.

4, with reference to FIG third state, the first switch Q ₁ originally nonconductive, the second switch and the third switch Q ₂ Q ₃ is not turned on, but the pulse width modulation signal having a time delay in this state such that the second switch Q ₂ zone And the third switch Q ₃ is turned on by the self-diode. When the first winding 11 releases energy to the output to a voltage of zero to a fourth state.

5, with reference to FIG fourth state, the first switch Q ₁ originally nonconductive, the second switch and the third switch Q ₂ Q ₃ is turned on, and the second switch Q ₂ and the third switch Q3 to zero voltage switching (zero voltage switching In this state, the energy transfer capacitor C _B reversely excites the first winding 11 of the coupled inductor 1 , and the coupled inductor 1 transfers energy to the output through the second winding 12 by a transformer behavior. Therefore, the current I _{N1 of the} first winding 11 increases in the opposite direction and the current I _{N2 of the} second winding 12 also increases, and the voltage of the first winding 11 is as shown in Equation 2.

Referring to FIG 6, a fifth state, the first switch Q ₁ originally nonconductive, the second switch and the third switch Q ₂ Q ₃ is not turned on, but the pulse width modulation signal such that the region of this state has a second switch Q ₂ is retarded And the third switch Q ₃ is turned on by the self-diode.

Referring to Figure 7, the sixth state, the original first switch Q _1, the second switch and the third switch Q ₂ Q ₃ is not turned on, the second switch Q ₂ and Q ₃ because the third switch diode autologous turned, The leakage inductance energy of the first winding 11 is demagnetized in the opposite direction, so that the voltage is 0 to the seventh state.

Referring to Figure 8, a seventh state, the first switch Q ₁ is turned on with zero voltage switching, the second switch and the third switch Q ₂ Q ₃ is not conducting, in this state, the input voltage V _in the energy charge transfer capacitance C _B The current I _{N1 of the} first winding 11 is much lower than the current I _{N2 of the} second winding 12 , and the third switch Q ₃ maintains conduction, when the current I _{N1 of the} first winding 11 is equal to the current I _{N2 of the} second winding 12 , the third Q switch diode from conducting body ₃ does not return to the first state.

According to Equation 1 and Equation 2, and based on the volt-second principle of the first winding 11, the derivation is as shown in Equation 3.

The voltage conversion ratio of the low buck converter 100 conforms to the following formula:

In the above formulas 3 and 4, D is the duty cycle of the wave width modulation signal, and it is understood that as long as the number of turns of the first winding 11 is N ₁ and the number of turns of the second winding 12 is N ₂ fixed, only By adjusting the duty cycle D of the bandwidth modulation signal, the voltage conversion ratio of the low buck converter 100 can be controlled.

In this embodiment, the actual specifications of the components are as follows: (i) the input voltage V _{in is} set to 48 volts; (ii) the output voltage V _{O is} set to 3.3 V; (iii) the rated output current is 15 amps; (iv) the switch The frequency fs is 100 kHz; (v) the number of turns N ₁ of the first winding 11 is 24 turns, the number of turns N ₂ of the second winding 12 is 8 turns, and the main inductance is 86 μH; (vi) the output capacitor Co is selected to have a capacitance of 1800 μF; (vii) The model of the first switch Q ₁ and the second switch Q ₂ is PHB34NQ10T; (viii) the model of the third switch Q3 is PHD96NQ3LT.

Referring to Figure 9, a first switch Q ₁ 'wave width modulated signal and the second switch Q V _gs1 pulse width modulation signal V _{gs2 2,} the first winding 11 and a current of the current I and the second winding 12 of _Nl I _N2 .

Referring to Figure 10, shows a positive edge of the first switch Q ₁ 'wave width modulated signal V _gs1 of (positive edge) and the corresponding voltage V _ds1, and the negative edge of the second switching pulse width modulation signal Q V _{gs2 2} ( Negative edge) and the corresponding voltage V _ds2 .

Referring to FIG. 11, the negative edge of the width modulation signal V _gs1 of the first switch Q ₁ and the corresponding voltage V _ds1 , and the positive edge of the width modulation signal V _gs2 of the second switch Q ₂ and the corresponding voltage V are _displayed . _Ds2 .

Referring to Figure 12, the load transient response is changed from 50% to 100% load load enable (LOAD_EN) signal, output voltage V _O and output current I _O ; see Figure 13, showing load transient response (load transient response) A load enable signal, an output voltage V _{O ,} and an output current I _{O that are} changed from 100% to 50% load. Figures 12 and 13 also show that the undershoot or overshoot voltage is about 320 millivolts and the recovery time is about 500 microseconds.

Referring to Figure 14, the conversion efficiency corresponds to the load current. The display conversion performance can exceed 84.86% and the conversion performance can reach up to 95.78%, and the rated load conversion performance is 88.79%. .

In summary, the low buck converter 100 of the present invention has a simple circuit design, easy control, and a linear conversion characteristic, and when any switch fails or does not operate normally, other switches are turned on, and the output terminal does not appear. The high voltage protects the output load, so the object of the present invention can be achieved.

However, the above is only the embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and the patent specification of the present invention are still It is within the scope of the patent of the present invention.

100‧‧‧Low Buck Converter

1‧‧‧coupled inductor

C _B ‧‧‧ energy transfer capacitor

C _O ‧‧‧ output capacitor

11‧‧‧First winding

12‧‧‧second winding

N ₁ ‧‧‧Number of turns in the first winding

N ₂ ‧‧‧Number of turns in the second winding

Q ₁ ‧‧‧First switch

Q ₂ ‧‧‧Second switch

Q ₃ ‧‧‧third switch

V _in ‧‧‧ input voltage

V _O ‧‧‧Output voltage

Claims (1)

A low buck converter for stepping down an input voltage of a power supply to an output voltage, comprising: a first switch having a first input end, a first control end, and a first output end, the first An input terminal is coupled to the power source; a second switch has a second input end, a second control end, and a second output end, the second input end is coupled to the first output end, the second output end Grounding; an energy transfer capacitor, one end is electrically connected to the second input end; a coupled inductor has a first winding and a second winding, and the dot end of the first winding is electrically connected to the other end of the energy transfer capacitor, The non-injecting end of the first winding is electrically connected to the striking end of the second winding; the third switch has a third input end, a third control end and a third output end, and the third input end is coupled The non-tapping end of the first winding and the striking end of the second winding, the third output end is grounded; and an output capacitor electrically connected to the non-tapping end of the second winding; wherein the first switch is first The control terminal receives a wave of wide modulation signal to control the first Whether the second control terminal of the second switch and the third control terminal of the third switch receive the inverted signal of the wave width modulation signal to control whether the second switch and the third switch are turned on or not. Thereby, the output voltage is generated by the output capacitor after the output voltage is stepped down, and the voltage conversion ratio thereof conforms to the following formula: The number of turns of the first winding is N ₁ , the number of turns of the second winding is N ₂ , V _O is an input voltage value, V _in is an output voltage value, and D is a duty cycle of the wave width modulation signal.