TWI614981B - Isolated high step-down ratio DC-DC converter - Google Patents

Abstract

The invention relates to an isolated high step-down ratio DC-DC converter, comprising an input unit, a front half stage circuit and a second half stage circuit, the front half stage circuit is connected to the input unit, and the second half stage circuit is connected to the first half stage The circuit, the first half of the circuit mainly provides buck function and low input current chopping. The latter half circuit mainly provides electrical isolation, buck, and low output current chopping. The invention has the function of high step-down ratio, and only a single switch is used, and the control is simpler.

Description

Isolated high step-down ratio DC-DC converter

The present invention relates to an isolated high step-down ratio DC-DC converter, which is a DC-DC having an electrical isolation function and providing high step-down ratio, low input and output current chopping, and only one switching switch converter.

Nowadays, the development of science and technology, such as integrated circuit technology, has developed rapidly. The general electronic products are aimed at attracting the masses with the aim of being light, thin and short. The power source of the general electronic products is a power supply, which meets the power requirements of different electronic products. Related power conversion devices have been designed and improved.

For example, the Republic of China New Patent Publication No. I462456 "DC/DC conversion circuit" is a DC/DC conversion circuit coupled between a DC power supply and a load, comprising: a first charge extraction circuit coupled to The first power-distributing circuit is coupled to the load; a first switch is coupled to the first charge-discharging circuit; and a second switch is coupled to the second charge-discharging circuit; And a first inductor, one end of the first inductor is coupled to the first charge pumping circuit and the second charge pumping circuit, and the other end is coupled to one of the first switch and the second switch a node, wherein the first inductor, the first switch, and the second open relationship are coupled between the first charge pumping circuit and the second charge pumping circuit.

However, there are still some disadvantages such as insufficient pressure reduction ratio and non-isolated type, which have more doubts about the safety of use.

In view of this, the inventors continue to innovate and develop, and further propose an isolated high step-down DC-DC converter, comprising: an input unit for inputting a constant current; a front half circuit comprising an input inductor, a first a diode, a second diode, a third diode, a fourth diode, a first capacitor, a second capacitor, and a switch, wherein one end of the input inductor and the first The cathode end of the quadrupole is electrically connected to one of the positive ends of the input unit, and the other end of the input inductor is electrically connected to one end of the first capacitor and the cathode end of the second diode, the first The other end of the capacitor is electrically connected to the anode end of the third diode and the cathode end of the first diode, and the anode end of the second diode is electrically connected to the cathode end of the third diode And one end of the second capacitor, the anode end of the first diode, the other end of the second capacitor, and the first end of the switch are connected to one of the negative ends of the input unit; and a second half circuit , including a forward type DC-DC conversion Road, the forward type DC - DC converter circuit is coupled to the first-half stage circuit, and provides electrical isolation and down.

Further, the forward type DC-DC conversion circuit includes a transformer and an output circuit, and the transformer is a three-winding transformer including a primary side winding, a secondary side winding, and a tertiary side winding, the primary side One end of the winding is electrically connected to the cathode end of the second diode, and the other end of the primary winding is electrically connected to one second end of the switch, and one end of the tertiary winding is electrically connected to the switch The first end of the third side winding is electrically connected to the anode end of the fourth diode, and the secondary winding provides electrical isolation and voltage reduction, and is electrically connected to the output circuit.

Further, the output circuit includes a fifth diode, a sixth diode, an output inductor, an output capacitor, and a load, and one end of the secondary winding is electrically connected to the anode of the fifth diode Extremely, the cathode end of the fifth diode is electrically connected to the cathode end of the sixth diode and one end of the output inductor, and the other end of the output inductor is electrically connected to one end of the output capacitor and the negative One end of the carrier, the anode end of the sixth diode, the other end of the output capacitor, and the other end of the load are electrically connected to the other end of the secondary winding.

Further, the operation has a mode one and a mode two, the mode is that the switch is turned on, the first capacitor and the second capacitor are connected in parallel to release energy, and the mode is the switch is turned off, the first capacitor And the second capacitor stores energy in series.

Further, a pulse width modulation technique is used to control the on and off of the switch.

Further, the switching relationship is an N-type metal oxide semiconductor field effect transistor.

According to the above technical features, the following effects can be achieved:

，其中n=N₂/N₁為匝數比，D為責任週期，可提供高降壓比。 1. The voltage gain of the isolated high step-down DC-DC converter of the present invention is

Where n = N ₂ / N ₁ is the turns ratio and D is the duty cycle, which provides a high step-down ratio.

2. Only a single switch is used, the control is simple, and the cost can be reduced.

3. With low input current chopping and low output current chopping, the voltage stability is good.

4. It is electrically isolated and safe to use.

(1)‧‧‧Isolated high step-down ratio DC-DC converter

(11)‧‧‧ Input unit

(12) ‧‧‧First half circuit

(121)‧‧‧Input inductance

(122)‧‧‧First Diode

(123)‧‧‧Secondary diode

(124)‧‧‧ Third Dipole

(125)‧‧‧Fourth diode

(126)‧‧‧First Capacitor

(127)‧‧‧second capacitor

(128)‧‧‧Switch

(13) ‧‧‧second half circuit

(131)‧‧‧First side winding

(132)‧‧‧secondary winding

(133)‧‧‧3rd side winding

(134)‧‧‧ Fifth Dipole

(135)‧‧‧ Sixth diode

(136)‧‧‧Output inductance

(137)‧‧‧ Output capacitance

(138)‧‧‧ Load

[First FIG. 1] is a circuit diagram of an isolated high step-down DC-DC converter according to an embodiment of the present invention.

[Second diagram] is an equivalent circuit diagram of the isolated high step-down ratio DC-DC converter of the embodiment of the present invention.

[Third Diagram] The main waveform diagram of the isolated high step-down DC-DC converter of the embodiment of the present invention in a single switching period.

[Fourth Diagram] A current path diagram of the isolated high step-down DC-DC converter operating in the mode of the present invention.

[Fifth Diagram] A current path diagram of the isolated high step-down DC-DC converter operating in mode 2 of the embodiment of the present invention.

[Sixth Diagram] In the embodiment of the present invention, when the input voltage V _in is 200V, the output voltage V _o is 25V, the full-load output power is 200W, and the turns ratio of the transformer is 0.5, the trigger signal V _{GS1 of the} switch The analog waveform of the input inductor current i _L1 and the output inductor current i _Lo , the scale value of the waveform diagram is: i _L1 /i _Lo : 5A / div, time: 20μs / div.

[Seventh figure] The isolated high step-down DC-DC converter according to the embodiment of the present invention operates at an input voltage V _in 200V, an output voltage V _o of 25V, a full-load output power of 200W, and a turns ratio of the transformer. At 0.5 o'clock, the input voltage V _{in of} the input unit, the voltage V _C1 of the first capacitor, the voltage V _{C2 of} the second capacitor, and an analog waveform diagram of the output voltage V _o across the load, the waveform diagram thereof The scale values are: V _in /V _c1 /V _c2 /V _o :100V/div, time: 2ms/div.

[Eighth image] The isolated high step-down DC-DC converter according to the embodiment of the present invention operates at an input voltage V _in 200V, an output voltage V _o of 25V, a full-load output power of 200W, and a turns ratio of the transformer. At 0.5 o'clock, the analog waveform diagram of the current i _D1 of the first diode and the current i _D2 of the second diode has a scale value of the waveform: i _D1 /i _D2 : 2 A / div, time: 20 μs /div.

[Ninth aspect] The isolated high step-down DC-DC converter according to the embodiment of the present invention operates at an input voltage V _in 200V, an output voltage V _o of 25V, a full-load output power of 200W, and a turns ratio of the transformer. At 0.5 o'clock, the current of the third diode, i _D3 , the analog waveform of the current i _S1 of the switch, the scale value of the waveform diagram is: i _D3 /i _S1 : 2 A / div, time: 20 μs / div.

[Tenth Graph] The isolated high step-down DC-DC converter according to the embodiment of the present invention operates at an input voltage V _in 200 V, an output voltage V _o of 25 V, a full-load output power of 200 W, and a turns ratio of the transformer. At 0.5 o'clock, the analog waveform of the current i _D5 of the diode and the current i _D6 of the sixth diode, the scale value of the waveform diagram is: i _D5 /i _D6 : 5 A / div, time: 20 μs / div .

[11th] is a voltage gain graph of an isolated high step-down DC-DC converter according to an embodiment of the present invention.

In summary of the above technical features, the main effects of the isolated high step-down ratio DC-DC converter of the present invention will be apparent in the following embodiments.

Referring to the first figure, a circuit diagram of an isolated high step-down DC-DC converter (1) according to an embodiment of the present invention, the isolated high step-down DC-DC converter (1) includes an input unit ( 11), a front half circuit (12) and a second half circuit (13), wherein: the input unit (11) is used for inputting current. The first half circuit (12) includes an input inductor (121), a first diode (122), a second diode (123), a third diode (124), and a fourth The pole body (125), a first capacitor (126), a second capacitor (127), and a switch (128). The first capacitor (126) and the second capacitor (127) have substantially equal capacitance, and one end of the input inductor (121) and the cathode end of the fourth diode (125) are electrically The first end of the input unit (11) is electrically connected to one end of the first capacitor (126) and the cathode end of the second diode (123). The other end of the first capacitor (126) is electrically connected to the anode end of the third diode (124) and the cathode end of the first diode (122), and the anode of the second diode (123) The extreme end is electrically connected to the cathode end of the third diode (124) and one end of the second capacitor (127), and the anode end of the first diode (122) and the second capacitor (127) One end and one of the first ends of the switch (128) are connected to one of the negative ends of the input unit (11). The switching switch (128) is, for example, an N-type metal oxide semiconductor field effect transistor. The second-stage circuit (13) includes a forward-type DC-DC conversion circuit, the forward-type DC-DC conversion circuit includes a transformer and an output circuit, the transformer includes a primary side winding (131), a secondary side winding (132) and a tertiary side winding (133), the output circuit comprising a fifth diode (134), a sixth diode (135), an output inductor (136), a Output capacitor (137) and a load (138). Wherein, the primary side winding (131) One end is electrically connected to the cathode end of the second diode (123), and the other end of the primary winding (131) is electrically connected to one of the second ends of the switch (128), the tertiary winding ( 133) One end is electrically connected to the first end of the switch (128), and the other end of the third side winding (133) is electrically connected to the anode end of the fourth diode (125), the second The side winding (132) is electrically isolated and stepped down, and is electrically connected to the anode end of the fifth diode (134) at one end, and the cathode end of the fifth diode (134) is electrically connected to the first end a cathode end of the hexapole (135) and one end of the output inductor (136), the other end of the output inductor (136) is electrically connected to one end of the output capacitor (137) and one end of the load (138), The anode end of the sixth diode (135), the other end of the output capacitor (137), and the other end of the load (138) are electrically connected to the other end of the secondary winding (132).

Referring to the second figure, which is the equivalent circuit diagram of the first figure, the transformer is regarded as an ideal transformer and a magnetizing inductance (139), the ideal transformer includes the primary side winding (131), the secondary side The winding (132) and the tertiary winding (133), and the magnetizing inductance (139) is connected in parallel with the primary winding (131).

Referring to the third figure, the isolated high step-down DC-DC converter (1) of the present embodiment [the isolated high step-down DC-DC converter (1) is as shown in the second figure] The main waveform diagram of a single switching cycle uses a pulse width modulation technique to control the on and off of the switch (128) [the switch (128) as shown in the second figure] and includes two modes of operation. :

Mode 1: Referring to the third and fourth figures, the operation interval is [t ₀ , t ₁ ]. At t = 0, the switch (128) is turned "on" and the current path is indicated by the arrow in the fourth figure. Within this interval, the input unit (11) delivers energy to the input inductor (121) and the magnetizing inductance (139) of the transformer. The energy stored in the first capacitor (126) and the second capacitor (127) is paralleled to the output inductor (136), the output capacitor (137), and the load (138) via the transformer. Therefore, the current i _{L1 of} the input inductor (121) and the current i _Lo of the output inductor (136) increase linearly (as shown in the third figure, i _L1 and i _Lo ). In addition, in this interval, the magnetization inductance (139) of the transformer stores little energy, which is called remanence. When t=t ₁ , the switch (128) is switched to be off, and the mode is over.

Mode 2: Referring to the third and fifth figures, the operation interval is [t ₁ , t ₂ ]. At t = t _1, the changeover switch (128) is turned off, a current path as shown by arrow a fifth point to FIG. In this interval, the input unit (11) releases energy in series with the input inductor (121), and transfers energy to the first capacitor (126) and the second capacitor (127). At this time, the first capacitor (126) And the second capacitor (127) stores energy in series. In addition, the residual magnetic energy of the transformer is returned to the input unit (11) via the third winding (133). The output inductor (136) supplies energy to the output capacitor (137) and the load (138). Therefore, the current i _{L1 of} the input inductor (121) and the current i _Lo of the output inductor (136) are linearly reduced (as shown by the three figures i _L1 and i _Lo ). When t=t ₂ , the switch (128) is switched to be turned on again, and mode 2 ends.

，

，故電壓增益

，其中，n=N₂/N₁為匝數比，D為責任 週期。 It can be seen from the above analysis that the current of the input inductor (121) and the current of the output inductor (136) can provide a low chopping current function in the continuous conduction mode operation. The voltage gain (M) of the isolated high step-down DC-DC converter (1) of this embodiment is expressed as:

,

Voltage gain

Where n = N ₂ / N ₁ is the turns ratio and D is the duty cycle.

Referring to FIG. 6 , the switching switch (128) is operated when the input voltage V _in is 200V, the output voltage V _o is 25V, the full-load output power is 200W, and the turns ratio of the transformer is 0.5. The analog waveform diagram of the trigger signal V _GS1 , the current i _{L1 of} the input inductor (121), and the current i _Lo of the output inductor (136), the scale value of the waveform diagram is: i _L1 /i _Lo : 5A/div, Time: 20μs/div, it can be seen that the input inductor (121) and the output inductor (136) are both operated in continuous conduction mode, and the duty cycle is about 0.4.

Referring to FIG. 7 , the input unit (11) is operated when the input voltage V _in is 200V, the output voltage V _o is 25V, the full-load output power is 200W, and the turns ratio of the transformer is 0.5. The input voltage V _in , the voltage V _{C1 of} the first capacitor (126), the voltage of the second capacitor (V _C2 ), and an analog waveform diagram of the output voltage V _o across the load, the scale of the waveform diagram The value is: V _in /V _c1 /V _c2 /V _o :100V/div, time: 2ms/div, it can be seen that the isolated high step-down ratio DC-DC converter of this embodiment can achieve a high step-down ratio Features. The voltage of the first capacitor (V _C1 ) and the voltage of the second capacitor (V _C2 ) are both 125V, which is consistent with the analysis of mode one and mode two.

Referring to FIG. 8 , the first diode is operated when the input voltage V _in is 200V, the output voltage V _o is 25V, the full-load output power is 200W, and the turns ratio of the transformer is 0.5. The analog waveform of the current i _{D1 of} (122) and the current (i _D2 ) of the second diode (123), the scale value of the waveform diagram is: i _D1 /i _D2 : 2A / div, time: 20 μs / Div.

Referring to FIG. 9 , the third diode is operated when the input voltage V _in is 200V, the output voltage V _o is 25V, the full-load output power is 200W, and the turns ratio of the transformer is 0.5. (124) Current i _D3 , the analog waveform of the current i _S1 of the switch (128), the scale value of the waveform diagram is: i _D3 /i _S1 : 2A / div, time: 20 μs / div.

Referring to FIG. 10, when the input voltage V _in is 200V, the output voltage V _o is 25V, the full-load output power is 200W, and the turns ratio of the transformer is 0.5, the fifth diode ( 134) The current waveform of the current i _D5 and the current i _D6 of the sixth diode (135), the scale value of the waveform diagram is: i _D5 /i _D6 : 5A / div, time: 20 μs / div, Corresponding to the analysis of the aforementioned mode of operation.

Referring to FIG. 11 , it is a voltage gain curve diagram of the isolated high step-down DC-DC converter (1) according to an embodiment of the present invention, which can be seen to have a high step-down ratio.

In view of the foregoing description of the embodiments, the operation and the use of the present invention and the effects of the present invention are fully understood, but the above described embodiments are merely preferred embodiments of the present invention, and the invention may not be limited thereto. Included within the scope of the present invention are the scope of the present invention.

(1)‧‧‧Isolated high step-down ratio DC-DC converter

(11)‧‧‧ Input unit

(12) ‧‧‧First half circuit

(121)‧‧‧Input inductance

(122)‧‧‧First Diode

(123)‧‧‧Secondary diode

(124)‧‧‧ Third Dipole

(125)‧‧‧Fourth diode

(126)‧‧‧First Capacitor

(127)‧‧‧second capacitor

(128)‧‧‧Switch

(13) ‧‧‧second half circuit

(131)‧‧‧First side winding

(132)‧‧‧secondary winding

(133)‧‧‧3rd side winding

(134)‧‧‧ Fifth Dipole

(135)‧‧‧ Sixth diode

(136)‧‧‧Output inductance

(137)‧‧‧ Output capacitance

(138)‧‧‧ Load

Claims (5)

An isolated high step-down ratio DC-DC converter includes: an input unit for inputting a constant current; a front half circuit comprising an input inductor, a first diode, a second diode, and a a third diode, a fourth diode, a first capacitor, a second capacitor, and a switch, wherein the first capacitor and the second capacitor have substantially equal capacitance, and the input inductor One end and the cathode end of the fourth diode are electrically connected to one positive end of the input unit, and the other end of the input inductor is electrically connected to one end of the first capacitor and the cathode of the second diode Extremely, the other end of the first capacitor is electrically connected to the anode end of the third diode and the cathode end of the first diode, and the anode end of the second diode is electrically connected to the third a cathode end of the pole body and one end of the second capacitor, the anode end of the first diode, the other end of the second capacitor, and the first end of the switch are connected to one of the negative ends of the input unit; a second half circuit comprising a forward type DC-DC The forward-type DC-DC conversion circuit is coupled to the first-stage circuit and provides electrical isolation and voltage reduction. The forward-type DC-DC conversion circuit includes a transformer and an output circuit, and the transformer includes a primary side winding, a secondary side winding, and a tertiary side winding, one end of the primary side winding is electrically connected to the cathode end of the second diode, and the other end of the primary side winding is electrically connected to the switch One end of the third side winding is electrically connected to the first end of the switch, and the other end of the third side winding is electrically connected to the anode end of the fourth diode, the secondary side The winding system provides electrical isolation and voltage reduction, and is electrically connected to the output circuit; the DC power is input to the first half circuit by the input unit, and when the switching switch is turned on, the input unit transmits energy to the input inductor and the The magnetizing inductance of the transformer, the energy stored in the first capacitor and the second capacitor is parallelly sent to the output inductor, an output capacitor and a load of the output circuit through the transformer. When the switch is turned off, the input unit releases energy in series with the input inductor to store the energy in series with the first capacitor and the second capacitor, and the residual magnetic energy of the transformer is all sent back to the input unit via the tertiary side winding, and The output inductor supplies energy to the output capacitor and the load; thereby obtaining a voltage gain of the isolated high step-down DC-DC converter Where n is the turns ratio of the secondary winding and the primary winding, and D is the duty cycle. The isolated high step-down DC-DC converter according to claim 1, wherein the output circuit comprises a fifth diode, a sixth diode, the output inductor, the output capacitor, and In the load, one end of the secondary winding is electrically connected to the anode end of the fifth diode, and the cathode end of the fifth diode is electrically connected to the cathode end of the sixth diode and the output inductor In one end, the other end of the output inductor is electrically connected to one end of the output capacitor and one end of the load, and the anode end of the sixth diode, the other end of the output capacitor, and the other end of the load are electrically Connect the other end of the secondary winding. The isolated high step-down DC-DC converter according to claim 2, wherein the operation has a mode one and a mode two, the mode is that the switch is turned on, the first capacitor and the second The capacitor discharges energy in parallel. The second mode is that the switch is turned off, and the first capacitor and the second capacitor store energy in series. The isolated high step-down ratio DC-DC converter according to claim 1, wherein the switch is turned on and off by a pulse width modulation technique. The isolated high step-down ratio DC-DC converter according to claim 1, wherein the switching relationship is an N-type metal oxide semiconductor field effect transistor.