JPH04101663A - Switching regulator - Google Patents

Abstract

PURPOSE:To enhance power conversion efficiency without causing power loss due to dissipation of heat by absorbing a spike voltage, produced through switching operation, by means of a capacitor and discharging the capacitor immediately thereafter thereby returning the spike voltage back to a power supply and further transferring to the secondary. CONSTITUTION:Upon switching of a switch circuit 1 from ON to OFF (at time t2), voltage Vc rises to turn a diode D61 ON to feed a capacitor C6 with a charging current thus increasing a current IC6 instantaneously. A current ID begins to flow through a secondary winding NS at time t2 and a voltage is induced in the base winding NB in the direction for turning the transistor Q5 in a switch circuit 5 from OFF to ON. At that time, a diode D62 is turned ON to discharge excessive charges from the capacitor C6. The charges are fed to an input capacitor Co to be utilized again in power supply and further fed to the secondary.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a Swiss-tin regulator, and particularly to a switching regulator that is equipped with a circuit that absorbs spike-like voltage increases that occur in transformer windings during switching operations. Regarding.

[Conventional technology]

In a conventional switching regulator of this type, as illustrated in FIG.
A snubber circuit 4 is connected between both ends of the switch circuit 1 to absorb the spike voltage generated when the switch circuit 1 changes from on to off.

DC voltage V i input across the input capacitor C0
n is applied to the collector of the transistor Q1 of the switch circuit 1 through the primary winding NP of the transformer T, and to the collector of the transistor Q1 through the resistor R11.

is applied to the base of Further, the base of the transistor Q1 is connected to the input return line of the DC voltage V in via the resistor R12, the capacitor C1, and the base winding NB of the transformer T, and is also connected to the collector of the transistor Q2 of the stabilizing circuit 2. . The emitter of transistor Q1 is connected to the input return wire. Transistor Q of stabilization circuit 2
The emitter of 2 is connected to a constant voltage diode D21, and the base is connected to provide a divided voltage of resistors R2□ and R2□.Resistors R21 and R22 are connected in parallel with a capacitor C2 between both ends. It is connected between both ends of the base windings N, 3 via a diode D2□ for backflow prevention. A diode D is connected to the secondary winding Ns of the transformer T.
A rectifier circuit 3 consisting of a capacitor C3 and a capacitor C3 is connected to obtain a DC output voltage V out.

When the input voltage V in passes through the resistor RII) and the base current flows through the transformer Q1, the transistor Q1 starts to turn on (at time 1+ in Figure 10), and as a result, current flows through the primary winding of the transformer T. begins to flow (current ■ in Figure 10). Accordingly, the first winding N of the transformer T
A voltage is generated at B, supplying base current to transistor Q, and further ■. increases.

■. When Q increases and it becomes impossible for the base current to maintain the saturation of Q, Q goes out of saturation and V. increases, transistor Q1 rapidly switches to the off state, and the current flow increases. stops flowing (time t2 in FIG. 10).

At this time, the current ■. Trans T caused by the rapid decrease of
Snubber circuit 4 for electromotive force of leakage inductance
If there is no voltage at the collector of transistor Ql. As shown by the broken line in FIG. 10, the voltage becomes a steep spike-like voltage. In FIG. 9, the diode D4 of the snubber circuit 4
turns on, and this spike-like voltage can be absorbed by resistor: a+ and capacitor C4 (voltage ■ in Figure 10).

solid waveform).

When the transistor Q1 is turned off, the stored energy of the transformer T turns on the diode D3 of the rectifier circuit 3 connected to the secondary winding N, and is output as a current 1. When this energy is gone, Taito D3
is turned off (time 13 in FIG. 10), the transistor Q1 turns on again, and the switching operation continues.

[Problem to be solved by the invention]

In the above-mentioned conventional switching regulator, a snubber circuit is connected to the primary winding of the conversion transformer to absorb the spike-like voltage rise that occurs due to switching operation. This energy is dissipated by the internal resistance and becomes thermal energy, which reduces the power conversion efficiency of the switch regulator. Particularly when the switching frequency is high, the loss in the snubber circuit increases, significantly reducing the conversion efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide a switching regulator which eliminates the above-mentioned drawbacks, eliminates heat dissipation through resistance, and improves conversion efficiency.

[Means to solve the problem]

A switching regulator according to a first aspect of the present invention includes a transformer having one primary winding for input and a secondary winding for output electromagnetically coupled to the primary winding, and connected in series to the secondary winding. , a switch circuit that repeatedly connects and disconnects the DC input power source, and a charging path TIO F between the series connection point of the primary winding and the switch circuit and one terminal of the input terminal pair of the DC input power source. A charging path has a capacitor connected thereto, and a discharging path has a switching element connected in parallel to both ends of the diode and turned on when the capacitor is discharged.

The switching regulator of the second invention includes a transformer having two primary windings for input and a secondary winding for output electromagnetically coupled to the transformer, and a transformer connected in series between the two windings, and a direct current A switch circuit that repeatedly switches on and off the input power supply, a charging path that has a capacitor connected between both ends of the switch circuit via a charging path diode, and a charging path that is connected in parallel to the diode and is turned on when the capacitor is discharged. and a discharge path having a switch element.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of a first embodiment of the first aspect of the present invention, and FIG. 5 is a signal waveform diagram illustrating the operation of this embodiment. This embodiment does not use the snubber circuit 4 of the conventional circuit (see FIG. 9), but instead uses a charging/discharging circuit consisting of a capacitor C6, diodes D61 and D a2, and a switch circuit for controlling the operation of this circuit. 5 is provided. One end of the capacitor C6 is connected to the connection point between the primary winding Np of the transformer T and the switch circuit 1, and the other end is connected to the input return line via a diode D61 and via a diode F' D62. It is connected to the collector of the transistor Q5 of the switch circuit 5. A resistor Rs is connected between the emitter and base of the transistor Q of the switch circuit 5.
+ is connected, and a resistor R52 is connected to the base of the transistor Q5.
and a capacitor C5 are connected in series to one end of the base winding N8 of the transformer T, and the emitter is connected to the other end of the base winding NB.

The operation of the switch circuit 1 from when it starts to turn on until it turns off, that is, from time t1 to time t2 in FIG. 5, is the same as that of the conventional circuit, and therefore a description thereof will be omitted. When the switch circuit l switches from on to off (time t2),
Voltage V. increases, diode D6□ turns on, and in response, a charging current flows through capacitor C6, resulting in a current ■. 6 increases instantaneously. On the other hand, at time t2, the secondary winding N becomes ■. begins to flow, and this current induces a voltage in the base winding N8 in the direction of switching the transistor Q5 of the switch circuit 5 from off to on.

At this time, capacitor C6 is connected to the input return line via diode D62, but since the input return line has a higher potential, diode D62 is turned on and capacitor C
Discharge the surplus charge of 6.

This discharged charge is charged into the input capacitor C0 and reused for power supply, and also sends energy to the secondary side via the transformer T.

In this way, the spike-like voltage rise when the switch circuit 1 switches from on to off is absorbed by charging the capacitor C6, and is then discharged and transferred to the capacitor C9. There is no need to dissipate the heat absorbed by the electrician, and there is no reduction in power conversion efficiency.

Note that the operations other than the above-mentioned spike-like voltage absorption operation are the same as those of the conventional circuit, so the explanation will be omitted.

FIGS. 2 and 3 are circuit diagrams of second and third embodiments of the first aspect of the present invention, respectively.

In both embodiments, an intermediate tap is provided on the primary winding Np of the transformer T and connected to the emitter of a switching transistor Q6. Switch circuit] A diode F' D s is connected to the connection end with the primary winding Np in the direction that leads to the spike voltage generated when the switch circuit 1 is switched from on to off.
+ is connected. The tie auto 'Da+ is connected to one end of the charging/discharging capacitor C6 whose other end is connected to the input return line, and is further connected to a diode D in the discharge direction of the capacitor C6.
82 is connected. Diode D62 is connected to the collector of transistor Q6 so as to provide the mid-tap voltage of primary winding N2 between the base and emitter of transistor Q6.

When the switch circuit 1 switches from on to off and a spike-like voltage rise begins to occur in the primary winding NP, the diode D6
1 turns on, passing charging current to capacitor C6 and absorbing the spike-like voltage. Transistor Q6 then switches on, but at this time capacitor C6 is charged and has a potential higher than the input voltage, so diode D
6□ turns on, discharging the surplus charge of the capacitor C6 and transferring it to the capacitor C0.

FIG. 4 is a circuit diagram of a fourth embodiment of the first aspect of the present invention. The charging/discharging capacitor C6 has one end connected to the hot side of the input voltage, and the other end connected to the primary winding N of the switch circuit 1 via a diode D7. The source and drain of a MOS type transistor Q7 are connected to both ends of the diode D, and a knob voltage is applied between the gate and source of the transistor Q7.

When the switch circuit 1 is switched from on to off and a spike-like voltage rise occurs in the primary winding NF, the diode D7 turns on and charges the capacitor C6 to absorb the spike-like voltage. Transistor Q7 then turns on, discharging capacitor C6 and transferring energy to the secondary side via transformer T. Note that the diode D7 may be replaced by a parasitic diode inside the MOS transistor Q7. Further, in FIG. 4, the transistors in FIG. 3 are replaced with MO8 type transistors, but they may be replaced with MO3 type transistors in the embodiments of FIGS. 1 and 2 as well.

In each of the second to fourth embodiments, similarly to the first embodiment, the spike voltage generated during the switching operation is once charged into the capacitor C6, and then discharged to the power supply input side and the secondary Because energy is transferred, there is no heat dissipation of electrical energy as in conventional circuits, and a decrease in power conversion efficiency can be prevented.

In each of the above embodiments, the case where the primary winding N2 of the transformer T has one winding has been shown, but the present invention can also be applied when the primary winding NP has two windings. An example is shown below.

FIG. 6 is a circuit diagram showing an embodiment of the second invention of the present invention, in which the primary winding is made into two windings in the first embodiment of the first invention (see FIG. 1). show.

The transformer T has two primary windings Np0. The switch circuit 1, capacitor C6, and diode DB+ connected to the secondary winding N,1 are connected to the input return wire via the primary winding Np2. This operation is the same as that in the first embodiment, so a description thereof will be omitted.

If the primary winding is made into two windings and balanced in this way, it is possible to suppress the noise of the longitudinal current component from being transmitted from the primary side to the secondary side of the transformer T, and it is possible to reduce high frequency radiation noise. 6th
In the figure, the primary winding of the transformer in FIG. 1 is divided into two, but it can be similarly divided into two windings in FIGS. 2 to 4.

Although the above embodiments are all of the ringing choke converter type, they can also be applied to the forward converter type, and an example thereof will be shown below.

FIG. 7 is a circuit diagram showing a fifth embodiment of the first aspect of the present invention, and FIG. 8 is a signal timing diagram illustrating its operation. The present side is of a forward converter type, and the DC input voltage Vin input to both ends of the input capacitor C8 is applied between the primary winding N of the transformer T and the collector-emitter of the switching transistor Ql, The output signal a of the switching control ICI given to the base of is on, and is off. A capacitor C6 for charging and discharging and a tie-auto D61 for forming a charging path are connected between the collector and emitter of the transistor Q1, and a diode D62 for forming a discharge path and a diode D62 for forming a discharge path are connected between both ends of the diode D61. It is connected between the collector and emitter of the control transistor Q6. Transistor Q6 is already turned on or off by the switching control signal generated across N p 3 by the coupling between NF2 and NF2.

When the transistor Q1 is turned on in response to the voltage rise of the signal a, current begins to flow through the primary winding Np+ of the transformer T (time 1). When the voltage of signal a falls (time t2)
When the current in the primary winding Np is suddenly turned off and a spike-like voltage starts to occur, the diode D61 turns on,
The capacitor C6 is charged and absorbed, and NPI and N
Due to the coupling of P□, a forward current flows through D6 and is returned to co. Furthermore, at this time, due to the combination of N,2 and NF2, N
A voltage is generated in F2 in the direction of reverse biasing D9, which turns on transistor Q6, and in response, turns on transistor F' D 61 to circulate the excess charge of capacitor C6 to C8.

In this way, this embodiment also charges the capacitor to absorb the spike-like voltage that occurs due to the switching operation.
Since it immediately flows back to the power supply input side, heat dissipation does not occur, and therefore, a decrease in power conversion efficiency can be prevented.

Depending on the switching of the current in the primary winding NP, the secondary winding N
The voltage induced across the diode D3□.

It is rectified by D32 and smoothed by a coil L and a capacitor C3 to obtain a DC output voltage V out.

〔Effect of the invention〕

As explained above, according to the present invention, the capacitor is charged with the spike voltage generated due to the switching operation, absorbed, and immediately discharged to be returned to the power source, and at the same time, the energy is transferred to the secondary side. There is no power loss due to heat dissipation, and power conversion efficiency can be improved compared to when using a conventional snubber circuit.

Furthermore, since there is no need to reduce leakage inductance in order to suppress spike-like voltages, the structure of the magnetic core and winding of the transformer can be made simpler than before. In addition, the effect of suppressing spike voltages is better than that of conventional snubber circuits, so the output voltage rise caused by spike voltages at light loads is smaller than before, and the tummy resistor for no-load conditions is lower than that of conventional snubber circuits. Since the load can be lightened, power loss in the dummy resistor can be significantly reduced. Furthermore, since the charging/discharging capacitor is connected in parallel to the power supply input switching transistor, resistance to external surge noise is improved, and radiation of high frequency noise can be reduced. Furthermore, according to the experimental results using the link choke converter type, the degree of decrease in switching frequency under heavy loads is smaller than that of conventional circuits, and therefore the switching frequency is higher than that of conventional circuits, so transformers and capacitors are etc. parts! ”・You can also get the effect of being able to give shape.

D 3+ , D 32. D8. D-...
・Tie auto, T...)・Lance, N,, NP engineering+
NF2 + N P3... Primary winding, N3 - Secondary winding, NB... Be-3 winding, L... Coil.

Claims (7)

[Claims] (1) A transformer having one primary winding for input and a secondary winding for output electromagnetically coupled to the primary winding, which is connected in series to the primary winding, and repeatedly switches the DC input power supply on and off. a charging path including a switch circuit, a capacitor connected via a charging path diode between a series connection point of the primary winding and the switch circuit, and one terminal of a pair of input terminals of the DC input power source; A switching regulator comprising: a discharge path having a switch element connected in parallel to both ends of the diode and turned on when the capacitor is discharged. (2) The transformer has a base winding for controlling the connection/disconnection switching of the switch circuit, the charging path is connected in parallel to the switch circuit, and the discharge path is a discharge path connected in series to the switch element. The switching regulator according to claim 1, further comprising a diode for the switching regulator. (3) The switching regulator according to claim 2, wherein the discharge path turns on the switch element in response to an induced voltage in the base winding. (4) The switching regulator according to claim 2, wherein an intermediate tap is provided in the primary winding of the transformer, and the discharge path turns on the switch element in response to an induced voltage of the intermediate tap. (5) The switching regulator according to claim (1), wherein the charging path is connected in parallel to the primary winding. (6) The switching regulator according to claim (1), wherein the switching of the switching circuit and the on-operation of the switching element of the discharge path are respectively instructed by externally applied control signals. (7) A transformer having two primary windings for input and a secondary winding for output electromagnetically coupled to the transformers, and a transformer connected in series between the two windings to switch the DC input power supply on/off. a charging path having a capacitor connected between both ends of the switching circuit via a charging path diode, and a switching element connected in parallel to the diode and turned on when the capacitor is discharged. A switching regulator comprising a path.