JPH0449844A - Dc/dc converter - Google Patents

Abstract

PURPOSE:To smoothly shift switching operation of a main circuit and a flywheel circuit synchronously by employing an inductance having a square magnetizing characteristic. CONSTITUTION:Switching means Q of a main circuit is controlled to be opened or closed by a control circuit R. Since a positive voltage is applied to the base of a transistor Q3 during a period of closing the means Q, flywheel circuit F switching means Q2 is opened, no current flows to the circuit F, and a capacitor C2 is charged. Then, when the means Q is opened, a current starts to flow through a diode D2 and an inductance SR having square magnetizing characteristic, the inductance SR momentarily operated as a function of a large inductance to generate a reverse voltage. Accordingly, a potential at a point A momentarily becomes a negative potential, the transistor Q3 is opened, and the means Q2 is closed. Thus, the circuit F is shifted between a nonconductive state and a conductive state.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to improvements in DC-DC converters.

In particular, it relates to improvements in the flywheel circuit.

More specifically, the present invention relates to an improvement in which power loss does not occur in a flywheel circuit of a DC-DC converter, and time delay does not occur in flywheel operation.

[Conventional technology]

FIG. 4 shows a schematic configuration diagram of an example of a conventional DC-DC converter.

Referring to FIG. 4, Q is a switching means such as a p-channel enhancement field effect transistor, L is an inductance, and C is a capacitor.

A DC input voltage (1) is applied between the primary side of the switching means Q and the secondary side of the capacitor C, and the voltage VO across the capacitor C is output as a DC output voltage v0. R
is the control circuit, and the DC output voltage ■. and reference voltage ■, find the deviation voltage ΔV, determine the duty ratio ΔT/T (see Figure 2) that makes this deviation voltage ΔV zero, and calculate this duty ratio ΔT/T. The switching means Q is controlled on and off to achieve this. D.
is a flywheel diode, which has the function of releasing the energy stored in the inductance while the switching means Q is closed to the load while the switching means Q is open.

In the above configuration, the flywheel diode D3
The DC-DC converter shown in FIG. 5 was developed because of the drawback that the power loss due to the forward voltage drop cannot be ignored.

See FIG. 5 The difference from the configuration shown in FIG. 4 is that flywheel switching means Q4, such as an n-channel enhancement field effect transistor, is used in place of the flywheel diode D. The flywheel switching means Q4 is applied with a signal generated by the control circuit R, and performs an opening/closing operation opposite to that of the switching means Q. When the switching means Q is closed, the flywheel switching means Q4 ,
is open, and when the switching means Q is open, the flywheel switching means Q4 is closed to perform flywheel operation.

[1ilf1 to be solved by the invention] In the improved DC-DC converter shown in FIG. 5, the problem of forward voltage drop of the diode, which is inevitable in the DC-DC converter shown in FIG. 4, is solved. , it is not easy to smoothly execute the synchronous transition from the open circuit of the switching means Q to the closed circuit of the switching means Q4. Although it is not impossible to achieve this synchronous transition in terms of circuit design, there are factors that are difficult to accurately grasp, such as an operation delay based on the accumulated charge of the switching means Q, so even if a complex circuit is used, However, there is an unavoidable drawback that it is not easy to carry out the synchronous transition of the two switching means completely smoothly.

An object of the present invention is to eliminate this drawback, and to provide a DC-DC converter in which a flywheel circuit consisting of a switching means such as a field effect transistor is used instead of a flywheel diode. It is an object of the present invention to provide a DC-DC converter which is improved so that the operation and the operation of switching means for a flywheel circuit smoothly and synchronously transition.

[Means for Solving the Problem] The above object is such that a series circuit including a switching means (Q), an inductance (L), and a capacitor (C) is connected to a DC input power source, and the capacitor (C) is connected to a DC input power source. It has a main circuit that outputs the voltage across both ends of the DC output voltage (VO) as a DC output voltage (VO), and the DC output voltage (VO) and the reference voltage (v2).
is input, and in response to the deviation voltage (ΔV), the duty ratio (ΔT/T) of the switching means (Q) is changed.
and controls the switching means (Q) using this duty ratio (ΔT/T).
), a rectangular magnetization characteristic connected to the primary side of the inductance (L) between the primary side of the inductance (L) and the secondary side of the capacitor (C). The inductance (S
a flywheel circuit (F) consisting of a series circuit of a parallel circuit of a diode (D3) connected to this inductance (SR) and a second switching means (C2);
The flywheel circuit (F) charges the second capacitor CC1) in response to the closing of the switching means (Q), and also charges the second capacitor CC1) in response to the closing of the switching means (Q). The control electrode of (C2) is connected to the secondary side of said capacitor (C) to open said second switching means (Q3) and to respond to said opening of said switching means (Q). Then, the charged second capacitor (C2) is connected to the second switching means (C2) by a voltage instantaneously generated due to a change in the current flowing through the inductance (SR). said second switching means (
Flywheel circuit starting circuit (K
), and in response to the opening of said switching means (Q), said flywheel circuit (F)
This is achieved by a DI, -DC converter adapted to release the stored energy of said inductance (L) to the load.

Furthermore, in any of the above configurations, the flywheel circuit starting circuit (K) includes the inductance (L
) and a series circuit of the second capacitor (C1) and a diode (DI) connected between the primary side of the capacitor (C) and the secondary side of the capacitor (C), and the second capacitor (C2). ) and the secondary side of the capacitor (C), the voltage on the primary side of the inductance (L) and the inductance (S) having the square magnetization characteristic.
It is possible to use a circuit having a third switching means (Q3) controlled by R) and whose primary side is connected to the control electrode of the second switching means (C2).

[Effect]

In the DC-DC converter according to the present invention, a flywheel circuit F is constituted by a parallel circuit of a switching means Q such as a field effect transistor, a diode Dt, and a series circuit of an inductance SR having square magnetization characteristics, such as a saturable reactor. , and a diode (D1) connected between the primary side of the inductance (L) and the secondary side of the capacitor (C) and the second capacitor (C2).
the voltage on the primary side of the inductance (L) connected between the primary side of the second capacitor (C2) and the secondary side of the capacitor (C), and the voltage on the primary side of the inductance (L); an inductance (SR) having magnetizing properties; and third switching means (Q3), the primary side of which is connected to the control electrode of said second switching means (C2). When the switching means Q of the main circuit is closed, the second switching means Qt of the flywheel circuit is opened.
When the switching means Q of the main circuit is opened, the capacitor Ct is charged, and when the switching means Q of the main circuit is opened, the voltage generated instantaneously in response to a change in the current that starts flowing in the inductance SR having a rectangular magnetization characteristic, for example, a saturable reactor, is used. , the charged second capacitor C1 is connected to the second switching means Q, and this is closed to operate the flywheel circuit F, and when the switching means Q of the main circuit is closed again, The second switching means Q is opened to terminate the operation of the flywheel circuit F.

〔Example〕

Hereinafter, with reference to the drawings, D according to two embodiments of the present invention.
The C-DC converter will be explained.

1 is a schematic block diagram of a DC-DC converter according to a first embodiment of the present invention.

In the figure, Q is a switching means such as a P-channel enhancement field effect transistor, L is an inductance, and C is a capacitor.

A DC input voltage V1 is applied between the primary side of the switching means Q and the secondary side of the capacitor C, and the voltage across the capacitor C is .

is output as a DC output voltage V0. R is a control circuit which inputs the DC output voltage v0 and the reference voltage vl, calculates the deviation voltage ΔV, and sets the duty ratio ΔT/T (see Figure 2) to make the deviation voltage ΔV zero. Then, the switching means Q is controlled on/off so as to realize this duty ratio ΔT/T. An inductance SR having a rectangular magnetization characteristic connected to the primary side of the inductance L, a diode Dt connected to the inductance SR, and a second switching means Q.

a flywheel circuit F configured with a series circuit with a parallel circuit of the inductance L, a diode D connected between the primary side of the inductance L and the secondary side of the capacitor C, and the second capacitor A series circuit with Ct,
The inductance L is connected between the primary side of the second capacitor C2 and the secondary side of the capacitor C.
and the inductance SR having the square magnetization characteristic, and the primary side of the second
A flywheel circuit starting circuit having a control electrode of the switching means Q and a third switching means Q connected to the control electrode of the switching means Q is a component according to the gist of the present invention.

Refer to FIG. 2 Hereinafter, referring to the time chart shown in FIG. 2, the D according to the first embodiment of the present invention whose schematic block diagram is shown in FIG.
The operation of the C-DC converter will be explained.

When the switching means Q (in this example, a p-channel enhancement field effect transistor) of the circuit is closed, the DC input voltage V is applied to the capacitor C and the load via the inductance L, and the capacitor C is charged. , the DC output voltage V. is applied to the load. DC output voltage V. Since is also applied to the control circuit R, it is compared with the reference voltage V, and the duty ratio ΔT/T is determined in accordance with the deviation voltage ΔV, and the switching means Q of the main circuit sets ΔT. The DC output voltage (2) is controlled to be closed during the period (T-ΔT) and open during the period (T-ΔT), so that the DC output voltage (2) matches the reference voltage (2). is supplied to the load.

During the period when the switching means Q of the royal circuit is closed,
npn) Since a positive voltage is applied to the base of the run lister Q, which is closed, the second switching means Q, which constitutes the flywheel circuit F (in this example,
The n-channel enhancement field effect transistor) is open, and tfL does not flow through the flywheel circuit F.

However, during this period, the second capacitor C7 is charged.

Next, when a period of 8T has elapsed and the control circuit R operates and the switching means Q of the main circuit is opened, the capacitor C
The charge stored in the inductance L and the energy stored magnetically in the inductance L are released, and DC output continues to be supplied.

At this time, the potential on the primary side of the inductance L (point A in the figure) decreases, so a current flows through the diode D and the inductance SR (in this example, a saturable reactor) having square magnetization characteristics. To begin with, since the inductance SR having square magnetization characteristics instantaneously functions as a large inductance and generates a reverse voltage, the potential at point A instantaneously becomes a negative potential. Therefore,
npn) The runlister Q3 is opened, and the positive potential of the second capacitor C2, which has already been charged, is applied to the gate of the second switching means Q, and the second switching means Q2 is closed, and the flywheel circuit F becomes conductive, and the energy stored in the inductance L is released via this flywheel circuit F. This state is maintained until the npn) run lister Q3 is closed.

On the other hand, the inductance SR having the rectangular magnetization characteristic is saturated with the inflow of a small amount of current and does not function as an inductance thereafter, so that no large power loss occurs in the flywheel circuit F.

Note that even if the second switching means Q should open during the period when the switching means Q is open, the flywheel circuit F will be maintained in a conductive state via the diode D8. Therefore, reliability is high.

Furthermore, the resistors R, R2, and Rs are all current-limiting resistors and have no significant significance to the circuit operation.On the other hand, the diode D4 is just a protection means, and this also has no significant significance to the circuit operation. No effect.

When the period T is completed and the switching means Q is closed again, the initial state is restored, but at this time the second switching means Q2 is still in the closed state. However, the inductance SR with square magnetization characteristics does not have a large inductance value when the direction of current flow is reversed, so a voltage is generated across the inductance SR with square magnetization characteristics, and the potential at point A increases. do. At that time, a positive voltage is applied to the base of the npn) run lister Q3, and the npn) run lister Q is closed, thereby opening the second switching means Q.

Therefore, the npn transistor Q, is closed and the second
There is a slight time delay before the second switching means Q opens, but during that period, the second switching means Q
In reality, this does not entail any disadvantages, since only a small current flows through the inductor, which is limited by the large inductance value of the inductance SR, which has square magnetization characteristics.

As explained above, the DC-DC converter having the circuit configuration shown in FIG. However, there is no forward loss in the flywheel circuit F, and the flywheel operation can be performed by rapidly following the opening and closing of the switching means Q.

''See Figure 3 The difference between this example and the first example is that the gate potential of the second switching means Q constituting the flywheel circuit F is closed during the period when the switching means Q is closed. The second switching means Q is held at a negative potential and kept open, and is opened during the period when the switching means Q is open to change the potential of the second capacitor C8 to the second switching means Q constituting the flywheel circuit F. An n-channel enhancement type field effect transistor is used as the switching means Q3 for closing the gate of the switching means Qt, and only some minor changes have been made in this connection. The basic operation is exactly the same.

〔Effect of the invention〕

As explained above, in the DC-DC converter according to the present invention, a series circuit including a switching means, an inductance, and a capacitor is connected to a DC input power source, and outputs the voltage across the capacitor as a DC output voltage. It has a main circuit, receives the DC output voltage and the reference voltage, determines a duty ratio of the switching means in response to the deviation voltage, and controls the switching means using this duty ratio. In a DC-DC converter having a control circuit, an inductance having a rectangular magnetization characteristic connected to the primary side of the inductance, such as a saturable reactor, is connected between the primary side of the inductance and the secondary side of the capacitor. A flywheel circuit is provided, which is formed by a series circuit of a diode connected to this inductance, for example, a saturable reactor, and a parallel circuit of the second switching means, and this flywheel circuit includes a closed circuit of the switching means. In response, charging the second capacitor also opens said second switching means, and in response to opening said switching means, an inductance having said rectangular magnetization characteristic, e.g. A circuit for starting a flywheel circuit, which closes the second switching means using the charged second capacitor with a voltage instantaneously generated due to a change in the current flowing in the reactor. is provided, and in response to opening of said switching means, said flywheel circuit is adapted to release the stored energy of said inductance to the load, so that the forward voltage of the flywheel diode is increased. It goes without saying that the problem below has been resolved, and furthermore, the operation of the switching means for the main circuit and the operation of the switching means for the flywheel circuit have been improved so that they transition smoothly and synchronously. .

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a DC-DC converter according to a first embodiment of the present invention. FIG. 2 is a time chart for explaining the operation of the DC-DC converter according to the first embodiment of the present invention. FIG. 3 is a schematic block diagram of a DC-DC converter according to a second embodiment of the present invention. FIG. 4 is a schematic block diagram of a DC-DC converter according to the prior art. FIG. 5 is a schematic block diagram of an improved DC-DC converter according to the prior art. Q・ ・ L ・ ・ C・ ・ ■１ ・ ■o ・ R・ ・ ■１ ・ ΔV ・ T ・ ・ ΔT ・ F ・ ・ SR・ Main circuit switching means, main circuit inductance, main circuit capacitor, ・DC input voltage of the main circuit, - DC output voltage of the main circuit, constant voltage control device of the main circuit, - Reference voltage of the main circuit, - Deviation voltage of the main circuit, chopper control m period of the main circuit, - Continuity of the main circuit Period, flywheel circuit, - inductance (saturable reactor) with rectangular magnetization characteristics of the flywheel circuit, Q, ... second switching means of the flywheel circuit, D! ...Flywheel circuit diode, K...
・Circuit for starting the flywheel circuit, Ct...Second capacitor of the circuit for starting the flywheel circuit, D,...Diode of the circuit for starting the flywheel circuit, Q3...Second capacitor of the circuit for starting the flywheel circuit. 3 switching means, R,, R,, R,... Current limiting resistance of the flywheel circuit starting circuit, D4... Protection diode of the flywheel circuit starting circuit, A... Inductance of the main circuit. Point D on the primary side of L,
... flywheel diode of a DC-DC converter according to the prior art, Q4 ... an n-channel enhancement type field effect transistor for a flywheel circuit of a DC-DC converter according to the prior art.

Claims (1)

[Claims] [1] Switching means (Q) and inductance (L)
and a capacitor (C) are connected to a DC input power source, and have a main circuit that outputs the voltage across the capacitor (C) as a DC output voltage (V_O), and has a main circuit that outputs the voltage across the capacitor (C) as a DC output voltage (V_O). V_O) and reference voltage (V_R) are input, and in response to the deviation voltage (ΔV), the duty ratio (ΔT/T) of the switching means (Q) is determined and the duty ratio (ΔT/T) is determined. a control circuit (R) for controlling the switching means (Q) with a DC-
In the DC converter, the primary side of the inductance (L) and the capacitor (
An inductance (SR) having a square magnetization characteristic connected to the primary side of the inductance (L), a diode (D_2) connected to the inductance (SR), and a second switching means (Q_2
) is provided with a flywheel circuit (F) consisting of a series circuit with a parallel circuit of
The second capacitor (C_2) is charged, and the second capacitor (C_2) is charged.
The control electrode of the switching means (Q_2) is connected to the secondary side of the capacitor (C) to open the second switching means (Q_2) and to respond to the opening of the switching means (Q). Then, the inductance (SR
), the charged second capacitor (C_
2) to the control electrode of the second switching means (Q_2), and the second switching means (Q_2)
A flywheel circuit activation circuit (K) is provided, which closes the inductance (L), and in response to the opening of the switching means (Q), the flywheel circuit (F) closes the inductance (L).
D, which is characterized by releasing the stored energy of
C-DC converter. [2] Inductance (SR
) is a saturable reactor [
1] DC-DC converter described. [3] The flywheel circuit starting circuit (K) includes the primary side of the inductance (L) and the capacitor (C
) and a series circuit of a diode (D_1) and the second capacitor (C_2) connected between the primary side of the second capacitor (C_2) and the secondary side of the capacitor (C). The inductance (
third switching means (L) controlled by the voltage on the primary side of L) and the inductance (SR) having the rectangular magnetization characteristic, the primary side of which is connected to the control electrode of the second switching means (Q_2); D according to claim [1] or [2], characterized in that it has Q_3)
C-DC converter.