JPS6318962A - Switching power source - Google Patents

Abstract

PURPOSE:To stabilize the output of a switching power source by connecting a field effect transistor with a rectifier at the secondary side of the power source, and controlling the ON time of the FET. CONSTITUTION:When a voltage is applied to the gate of an FET 35 through the secondary winding 32 of a converter transformer in a direction becoming ON, a charging current flows through an inductance 38 to a capacitor 39 to raise its output voltage. When the output voltage arrives at a reference voltage, a signal is produced from a detector 41 to turn ON a transistor 40. Thus, the FET 35 is turned OFF. When the FET 35 is turned from ON to OFF, the energy of the inductance 38 is charged through a diode 37 in the capacitor 39. Thus, the output voltage is detected by the detector 41 to control the FET 35, thereby stabilizing the output voltage.

Description

[Detailed description of the invention] Field effect transistors (field effect transistors) are used in rectifier circuits of switching power supplies in industrial applications.
By using the FET (hereinafter referred to as FET), the FET
This relates to a switching power supply that controls the output by controlling the output.

Conventional technology In general, the secondary side rectifier circuit of a switching power supply cannot be stabilized against load fluctuations or input fluctuations unless its output circuit is controlled, and it cannot be stabilized against fluctuations in load or input. There is usually no protection available.

FIG. 11 shows an example of a switching power supply having a non-stabilized output circuit, and FIG. 12 shows an example of a switching power supply having a DC stabilizing circuit added to the non-stabilizing circuit.

In Figures 11 and 12, 1.16 is a rectifier bridge diode, 2.9.13.17.24.29 is a smoothing capacitor, 3.18 is a control circuit, 4.19 is an inverter FET, and 5.20 is a converter transformer, 6.7.1
0.11.21.22.26.27 is a diode, 8.
12, 23, and 28 are choke coils, 14.30 is a detection circuit, 15.31 is a feedback circuit, and 25 is a DC stabilizing power supply circuit.

Problems to be Solved by the Invention In the conventional switching power supply configured as described above, only the rectifier circuit of channel CH2, which applies feedback to control the switching semiconductor element, stabilizes its output. It can provide overcurrent and overvoltage protection. However, the output of the rectifier circuit of the other channel CHI, which does not apply feedback, fluctuates due to load fluctuations, input fluctuations, or fluctuations in other output circuits, so in order to stabilize it, a DC stabilization circuit 25 is installed in the circuit. must be added.

Although a wide variety of circuits are used for the additional DC stabilizing circuit 25, all of them have problems such as deteriorating power supply efficiency, increasing the number of parts, and increasing material costs.

Means for Solving the Problems The present invention solves the above-mentioned problems, and provides a switching system that extracts a stabilized DC output from a rectifying and smoothing circuit connected to the secondary winding of a converter transformer by controlling a switching semiconductor element. The switching power supply is characterized in that a field effect transistor is connected to the rectifier circuit on the secondary side of the switching power supply to stabilize the output voltage.

Function The switch/g power supply of the present invention uses a FET in the rectifier port n on the secondary side, and has the function of stabilizing the output voltage by controlling the on time of the FET, and sends an on/off signal to the FET. Therefore, it can also be used as a switch for sequencing, and has the function of protecting against overcurrent and the like.

Embodiments The present invention will be described below with reference to embodiments shown in FIGS. 1 to 10. FIG. 1 shows a principle diagram of an on-on type forward converter circuit, and FIG. 3 shows a principle diagram of an on-off type ringing choke converter circuit. Note that FETs currently on the market have a built-in diode between the drain D and source S, as shown in Figure 8, so in this case, the principle diagram in Figure 1 changes to the one shown in Figure 2. In addition, Fig. 3 shows FET45 or 64 as shown in Fig. 4.
This can be realized by inserting a diode 4G or 65 in series with . G in FIG. 7 is a gate. In Figures 1 to 4, 32.42.53.61 is the secondary winding of the transformer, 33.37.43.46.48.5
4.62.65 is a diode, 34.36.44.47
．． 55.57.63.66 is resistance, 35.45.56.
64 is an FET according to the present invention, 39.50.58.67 is a smoothing capacitor, 40.51.59.68 is a control transistor, and 41.52.60.69 is a detection circuit.

Next, the principle of operation will be explained using FIG.

When a voltage is applied to the gate of the FET 35 through the winding 32 of the transformer in a direction that turns it on, conduction occurs between the drain D and source S of the FET 35, charging current flows to the capacitor 39 through the inductance 38, and the output voltage increases. do. When the output voltage reaches the reference voltage, a signal is output from the detection port 4I and turns on the transistor 40, so that F
The gate voltage of ET35 decreases and the area between the drain D and source S of FET35 is turned off. The subsequent operation is the same as that of the secondary side rectifier circuit of the forward converter circuit, and when the FET 35 is turned off from the on state, the capacitor 39 is charged with the energy of the inductance 38 through the diode 37.

FIG. 9 illustrates the above operation using voltage waveforms at various parts, and is illustrated using modeled waveforms for easier understanding.

It is understood that the output voltage is stabilized by detecting the output voltage and controlling the FET according to the present invention in this manner.

FIG. 5 shows an embodiment of a forward converter circuit in a switching power supply, and FIG. 6 shows an embodiment of a ringing converter circuit in a switching power supply, in which 70.91 is a rectifier bridge diode, 71.82.88.92.101.
105 is a smoothing capacitor, 72.93 is a control circuit, 7
4.95 is a converter transformer, 75.79.80.
85.86.96.97.104 is a diode, 73
is an inverter FET, 76.7g, 98.100 is a resistor, 79.99 is an FET according to the present invention, 94 is an inverter transistor, 83.102 is a control transistor, 84.89.103.106 is a detection circuit, 90.10
7 is an auto coupler, and FET79.99 is the FET mentioned above.
It performs the same operation as 35.45.56.64. FIG. 7 shows a configuration in which two channels CHI in FIG. 5 are provided, and in this case, the auto-coupler 90 is removed and reliability can be further improved.

Figure 10 shows the rated human power of 100VAC, 1 output of 10V, 7A.

FIG. 5 is a regulation characteristic diagram of a switching power supply comparing a two-channel switching power supply using the forward converter circuit of FIG. 5 of the present invention and a conventional switching power supply of the same rating as shown in FIG. 10;

In FIG. 10, the horizontal axis is the output current in channel CHI, the vertical axis is the output voltage in channel CH2, solid line A is the product of the present invention, dotted line is the conventional product, and dotted line B1 is the channel CH2.
The maximum load (10■, 7A) &iB2 is the case when the same channel CH2 has the minimum load (10■, 0, IA).

As is clear from FIG. 10, it was demonstrated that the output voltage of the product of the present invention was extremely stable.

Effects of the Invention As described above, the switching power supply of the present invention can significantly stabilize the output by controlling the on-time of the output of the secondary winding of the transformer using the FET. It has remarkable effects, such as being able to be used as a sequence circuit or a protection circuit, and is of great industrial and practical value.

[Brief explanation of drawings]

Figures 1 to 7 show embodiments of the present invention, Figures 1 and 2 are examples of rectifier circuits on the secondary side of switching power supplies using the forward converter circuit system, and Figures 3 and 4 are ringing choke converters. An example of a rectifier circuit on the secondary side of a switching power supply using a circuit system, Figures 5 and 7 are circuit diagrams of the main parts of a switching power supply using a forward converter circuit system,
Figure 6 is a circuit diagram of the main parts of a switching power supply using a ringing choke converter circuit system, Figure 8 is a circuit diagram of a field effect transistor, Figure 9 is a waveform diagram of each part of the rectifier circuit in Figure 1, and Figure 10 is a diagram of the main parts of the rectifier circuit in Figure 1. Regulation characteristic diagram of switching power supply comparing invented product and conventional product, No. 11
1 and 12 are circuit diagrams of main parts of a switching power supply using a conventional forward converter circuit system. 32.42.53.61: Secondary winding of converter transformer 74.95: Transformer for converter 35.45.56.64.79.99: Field effect transistor patent published by Honda Capacitor Industry Co., Ltd. Figure l 2z Oi 3rd ward also 4-c 5z $z. Procedural amendment (voluntary)

Claims (1)

[Claims] In a switching power supply that extracts a stabilized DC output from a rectifier and smoothing circuit connected to a secondary winding of a converter transformer by controlling a switching semiconductor element, a field effect transistor is connected to the rectifier circuit on the secondary side of the switching power supply. , a switching power supply characterized by stabilizing the output voltage.