JPH02133068A - Magnetic control type dc-dc converter - Google Patents

Abstract

PURPOSE:To prevent the decrease of load power by installing a control winding, one end of which is connected to a main winding, to a saturable coil, connecting an output-current control circuit so as to keep load voltage constant to a node, bonding the other end of the control winding with the positive pole side of the secondary winding of a transformer and connecting another end of the main winding to a rectifier diode. CONSTITUTION:A control winding NC, one end of which is bonded with a main winding NL, is mounted to a saturable coil 3, an output from a control circuit 4 using load voltage EO as an input and varying output currents so as to keep load voltage constant is connected at a node, the other, end of the control circuit NC is connected to the positive pole side of the secondary winding NS of a transformer T, and another end of the main winding NL is bonded with a rectifier diode D1. Accordingly, an effect on the saturable coil 3 by currents Ir made to flow for the reverse recovery time of the rectifier diode D1 is eliminated, thus preventing the reduction of load power.

Description

[Detailed Description of the Invention] [Summary] Regarding a magnetically controlled DC-DC converter that keeps the load voltage constant by controlling a saturable coil, the present invention relates to a magnetically controlled DC-DC converter that keeps the load voltage constant by controlling a saturable coil. The first method aims to provide a controlled DC-DC converter, and the saturable coil is provided with a control #@ line connected to the main winding at one end, and the load voltage is input to the connection point. The output of a control circuit that varies the output current to keep the load voltage constant is connected, and the other end of the control Ill winding is connected to the positive electrode side of the secondary winding of the transformer, and the other end of the main winding is connected. Connect it to the rectifier diode.

In the second method, a control winding is provided in the saturable coil, one end of which is connected to the main winding NL, the connection point being connected to the positive side of the secondary winding of the transformer, and the other end of the main winding being connected to the positive terminal of the secondary winding of the transformer. is connected to a rectifier diode, and the other end of the control winding is connected to the output of a control circuit which receives the load voltage as an input and varies the output current so as to keep the load voltage constant.

[Industrial application field]

The present invention provides a magnetically controlled DC-DC that keeps the load voltage constant by controlling a saturable coil using an amorphous core or the like.
Concerning improvements to the converter.

In a magnetically controlled DC-DC converter, the time ratio of turning on and off the switching element is constant and does not vary, and the time ratio of the saturable coil is in an unsaturated state, which indicates the switch-off state, and the time indicates the switch-on state. The load voltage is kept constant by changing the ratio to the saturation time, and this ratio is changed using a control current.

Since the amorphous core has less iron and has good square characteristics of the B-H curve, magnetically controlled DC-DC converters using this core in the saturable coil have come to be widely used.

In a magnetically controlled DC-DC converter, when the switching element is turned off and a back electromotive force of the transformer is generated,
A reverse current flows through the saturable coil during the reverse recovery time when the impedance of the rectifier diode changes from low to high.

Then, when the switching element is turned on, the voltage-time product required to bring it into a saturated state increases, and the output power decreases, so it is desirable to prevent this.

[Conventional technology]

A conventional example will be explained below using figures.

Fig. 4 is a circuit diagram of a conventional magnetically controlled DC-DC converter, Fig. 5 is a diagram showing voltage waveforms at various parts in Fig. 4, and Fig. 6
The figure is an explanatory diagram of problems in a conventional magnetically controlled DC-DC converter.

In FIG. 4, when the switching transistor Tr is turned on and off at a ratio of 1:1 under the control of the drive circuit 1, a voltage as shown in FIG. 5 V8m is generated in the secondary winding NS of the transformer T.

When the switching transistor Tr is turned on and a voltage is generated in the secondary winding NS of the transformer T, the saturable coil 3 is in a non-saturated state and the impedance is high. applied to the saturable coil 3.

After a while, it becomes saturated and the impedance becomes approximately 0.
Therefore, no voltage drop occurs here, so the voltage across the flywheel diode D2 is as shown in Figure 5 ■1
The voltage will be as shown in .

This voltage is smoothed by a smoothing filter 6 and supplies power to the load 5.

When the switching transistor Tr is turned off, the energy stored in the coil is smoothed by the capacitor C via the flywheel diode D2 and supplies power to the load 5.

In order to stabilize the load voltage E0, for example, when the load voltage E0 increases, the control circuit 4 increases the output control current IC to increase the voltage duration that is applied to the saturable coil 3 when the switching transistor Tr is turned on. The load voltage E0 is lowered by increasing the product VSRtl.

[Problem to be Solved by the Invention] However, when the switching transistor Tr is turned off, the secondary winding NS of the transformer T has the
A back electromotive force is generated as shown in ○.

Then, a reverse current 1r flows during the reverse recovery time of the rectifier diode D1, and the current ISR flowing through the saturable coil 3 becomes as shown in the following equation.

1, R=lc+Ir Then, due to the influence of this reverse current 1r, when the switching transistor Tr is on, the voltage-time product applied to the saturable coil 3 increases, and the power sent to the load decreases.The first problem is that There is a point.

That is, as shown in FIG. 6(B), there is a decrease in the load voltage E0.

Also, as shown by VSR in FIG. 5, the reset time L2 when resetting the saturable coil 3 is shortened because the current Ir flows through the flywheel diode D2 during the reverse recovery time of the rectifier diode D1. The voltage applied to the saturable coil 3 is E,XNS/ND (where E is the power supply voltage and ND is the I line of the transformer T), which is the load voltage E. is not related, so the voltage is small and the reset time t2
There is a second problem that the conversion frequency cannot be increased because it is long.

An object of the present invention is to provide a magnetically controlled DC-DC converter that reduces the decrease in power sent to a load and can increase the conversion frequency.

[Means to solve the problem]

FIGS. 1 and 2 are magnetically controlled DC-Ds according to embodiments of the present invention.
FIG. 2 is a circuit diagram of a C converter.

As shown in FIGS. 1 and 2, a DC power supply 2, a primary winding NP of a transformer T, and a switching element Tr are connected in series, and a saturable coil 3 and a rectifier diode are connected to the positive side of the secondary winding NS of the transformer T. D1 are sequentially connected, and then a smoothing filter 6 having a flywheel diode D2 is connected, and the power output to the secondary winding NS of the transformer T is transferred to the saturable coil 3 by turning on and off the switching element Tr. In a magnetically controlled DC-DC converter that maintains a constant load voltage E0, the first method is to connect the saturable coil 3 with one end connected to the main winding NL, as shown in FIG. A control winding NC is provided, and the output of a control circuit 4 that inputs the load voltage E0 and varies the output current to keep the load voltage constant is connected to the connection point, and the other end of the control circuit NC is connected to the connection point. It is connected to the positive electrode side of the secondary winding NS of the transformer T, and the other end of the main winding NL is connected to the rectifier diode DI.

In the second method, as shown in 2nd V, the saturable coil 3 has a control +a cotton N which is connected at one end to the main cotton NL.
C, the connection point is connected to the positive side of the secondary winding NS of the transformer T, the other end of the main winding NL is connected to the rectifier diode DI, and the other end of the control winding NC is f1, Load voltage E. is connected to the output of a control circuit 4 which inputs and varies the output current so as to keep the load voltage constant.

L), and the current Ir flowing through the rectifier diode DI via the flywheel diode D2 is reduced by IcX compared to the conventional one.
It can be made smaller by NC/NL, and it can also be made O by changing the winding ratio.

Therefore, it is possible to eliminate the influence on the saturable coil 3 due to the current 1r flowing during the reverse recovery time of the rectifier diode D1, and to reduce the decrease in load power.

If the above current 1r is O, then the switching element Tr
The maximum voltage applied to the saturable coil 3 when off is (
E, XNS/ND)+Eo, which is larger than the conventional case by the load voltage E0, so the reset time t2 of the saturable coil 3 can be reduced and the conversion frequency can be increased.

[For production]

When configured as shown in Figures 1 and 2, the switching element Tr is turned off, a back electromotive force is generated in the secondary winding NS of the transformer T, and during the reverse recovery time of the rectifier diode DI, the saturable coil Current flowing through 3 I s++' =
I c+ (I r-1 cXNC/N [Example]) Fig. 1 is a circuit diagram of a magnetically controlled DC-DC converter according to an embodiment of the present invention, and Fig. 2 is a circuit diagram of a magnetically controlled DC-DC converter according to another embodiment of the present invention. The circuit diagram of the DC-DC converter, FIG. 3, is a diagram showing voltage waveforms at various parts and load current versus load voltage characteristics in the case of FIGS. 1 and 2.

1 and 2, the difference from the conventional example shown in FIG. 4 is that a control winding NC is provided in the saturable coil 3, and a control current Tc is passed through the control winding NC from the control circuit 4. The point is that it is possible to control the

In this way, in both the cases of FIGS. 1 and 2, the switching transistor Tr is turned off, a back electromotive force is generated in the secondary winding NS of the transformer T, and during the reverse recovery time of the rectifier diode D1, the switching transistor Tr is turned off. The current flowing through the saturation coil 3 is I
．． ．． ' = Ic+ (Ir - IcXNC/NL), and the current 1r flowing through the rectifier diode D1 via the flywheel diode D2 is reduced to IcXNC/N compared to the conventional one.
It can be made smaller by L, and it can also be made O by changing the winding ratio.

Therefore, it is possible to eliminate the influence on the saturable coil 3 due to the current Ir flowing during the reverse recovery time of the rectifier diode DI, and to reduce the decrease in load power.

Therefore, when the load current is increased, the point at which the load voltage decreases is the conventional load current ■, as shown in FIG. 3(A). Load current I larger than in case of 1. Case 2 can be used.

Also, if the above current Tr is set to 0, no current flows through the rectifier diode D1, so the voltage across the control winding NC of the saturable coil 3 is V NC = (E = XNS/ND) 10B.
．． Therefore, the voltage applied to the winding NL is VNL=V NC
X (NC/NL) = C (E = xNS/ND)
+E, )x (NC/NL), for example, NC=NL
Then, V NL = (E 6 XNS/ND) + E
0, and the load voltage E0 is increased compared to the conventional case, so the reset time of the saturable coil 3 when the switching transistor Tr is turned off can be reduced as shown in FIG. It is possible to increase the frequency.

〔Effect of the invention〕

As explained in detail above, the present invention has the following effects.

When the switching transistor Tr is turned off, the current flowing through the saturable coil 3 during the reverse recovery time of the rectifier diode DI can be reduced to a small value <<0, so that the decrease in output load power can be minimized.

Furthermore, since the time during which the saturable coil 3 is turned off can be reduced compared to the conventional case, changes in magnetic flux density can also be reduced, iron loss is reduced, temperature rise in the core is suppressed, and the device can be made smaller.

Furthermore, the reset time of the saturable coil 3 can be reduced, and the conversion frequency can be increased.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a magnetically controlled DC-DC converter according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a magnetically controlled DC-DC converter according to another embodiment of the present invention, and FIG. 3 is a circuit diagram of a magnetically controlled DC-DC converter according to another embodiment of the present invention. Figure 4 is a circuit diagram of a conventional magnetically controlled DC-DC converter; Figure 5 is a diagram showing the voltage waveforms and load current vs. load voltage characteristics of each part in the case of Figure 2; Figure 5 is a diagram showing each part of Figure 4. FIG. 6 is a diagram illustrating problems in a conventional magnetically controlled DC-DC converter. In the figure, 1 is a drive circuit, 2 is a DC power supply, 3 is a saturable coil, 4 is a control circuit, 5 is a load, 6 is a smoothing filter, Tr is a switching element, a switching transistor, T is a transformer, D1 is a rectifier diode, D2 is a flywheel diode, D3 and D4 are diodes, L is a choke, C is a capacitor, E0 is a load voltage, NL is a main winding, NC is a control winding, NP is a primary winding, Fig. Flood's real ass M ke `` stone a ki p '' jp type le C-
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Claims (1)

[Claims] 1. Primary winding (NP) of DC power supply (2) and transformer (T)
) and a switching element (Tr) are connected in series, a saturable coil (3) and a rectifier diode (D1) are connected in series to the positive electrode side of the secondary winding (NS) of the transformer (T), and then is connected to a smoothing filter (6) having a flywheel diode (D2), which controls the power output to the secondary winding (NS) of the transformer (T) by turning on and off the switching element (Tr). Saturation coil (3)
In the magnetically controlled DC-DC converter that controls the load voltage (E_0) to be constant, the saturable coil (3) is provided with a control winding (NC) whose one end is connected to the main winding (NL), The main winding (NL) and the control winding (NC
) is connected to a control circuit (
4), and connect the other end of the control circuit (NC) to the positive side of the secondary winding (NS) of the transformer (T),
A magnetically controlled DC type characterized in that the other end of the main winding (NL) is connected to the rectifier diode (D1).
DC converter. 2. According to claim 1, the saturable coil (3) is provided with a control winding (NC), one end of which is connected to the main winding (NL), and the control winding (NC) is connected to the main winding (NL). The connection point is connected to the positive side of the secondary winding (NS) of the transformer (T), the other end of the main winding (NL) is connected to the rectifier diode (D1), and the other end of the control winding (NC) is connected to the positive side of the secondary winding (NS) of the transformer (T). The end is the load voltage (E_0
) is connected to the output of a control circuit (4) which takes the input voltage and varies the output current so as to keep the load voltage constant.