JPH11220883A - Rectifier circuit with rush-current preventive function and onboard power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a power loss in a steady state operation concerning a preventive circuit against a rush current induced in the start in a rectifier circuit which rectifies a commercial AC power supply. SOLUTION: The input terminals of a rectifier circuit consisting of diodes 3 and 5 and thyristors 7 and 9 which are connected to each other so as to form a bridge are connected to a commercial AC power supply 1. The respective anodes of initial charging diodes 11 and 13 are connected to the input terminals. The respective cathodes of the initial charging diodes 11 and 13 are connected to a smoothing capacitor 17 and a load 19 through a resistor 15. The respective gates of the thyristors 7 and 9 are connected to a gate driving signal source (not shown). When a voltage between both the terminals of the capacitor 17 is sufficiently elevated, the thyristors 7 and 9 are turned on by a on-signal supplied by the gate driving signal source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier circuit having an inrush current preventing function and an on-board power supply, and more particularly to a rectifier circuit having an inrush current preventing function for improving efficiency and an on-board power supply.

[0002]

2. Description of the Related Art DC-
2. Description of the Related Art A so-called on-board power supply device in which all components such as a DC converter are mounted on a metal substrate has become widespread, and its performance has been further developed to achieve high efficiency and miniaturization. With the progress, high power output of several hundred watts is being realized by a small on-board power supply.

[0005] In this on-board power supply device, when the output becomes large, there is a problem of measures for heat radiation of main circuit components. Therefore, it is important to further improve the efficiency of the entire circuit, and avoiding concentration of heat loss of components such as the main circuit is also an effective solution.

When rectifying a commercial AC power supply as an input power supply, a large-capacity smoothing capacitor is required. At the time of startup, an inrush current flows to the smoothing capacitor. Conventionally, as a circuit for preventing this rush current, a rush current limiting resistor 15 is connected between the rectifier circuit 2 and the smoothing capacitor 17 as shown in FIG. When the input commercial AC power supply 1 is initially connected, the smoothing capacitor 17 is charged through the inrush current limiting resistor 15, and when the charging voltage of the smoothing capacitor 17 reaches a predetermined value, the inrush current A circuit in which a limiting resistor 15 is short-circuited by a thyristor 4 connected in parallel to the limiting resistor 15 is widely used.

Although this circuit works effectively for the function of preventing an inrush current at the time of startup, the thyristor 4 is always connected in series to the main circuit even during steady operation, and even if the thyristor 4 is turned on. In addition, one forward voltage drop of the diode causes extra power loss. In other words, a voltage drop of two diodes in the rectifier circuit and a voltage drop of the thyristor 4 generate a voltage drop of about three diodes in total, and the power loss is a problem.

[Problems to be solved by the invention]

An object of the present invention is to improve the efficiency of an inrush current prevention circuit in a rectifier circuit using a commercial AC power supply as an input. Another object of the present invention is to improve efficiency and avoid concentration of heat loss in an on-board power supply device in which the inrush current prevention circuit is mounted on a metal substrate together with a converter circuit and the like.

[0007]

Means for Solving the Problems The present invention proposes the following means. That is, a switching element such as a thyristor is provided on one of the arms constituting the rectifier circuit, and a series circuit of a diode for inrush current limiting and a resistor is provided separately, and the charging voltage of the smoothing capacitor is set to a predetermined value. The switching element is turned on at the time point when it reaches. By this means, the short-circuit switching element of the inrush current limiting resistor is included in the rectifying diode, so that the conventional voltage drop of the short-circuit switching element can be omitted, and the voltage drop of the main circuit in a steady state can be eliminated. Is to reduce.

[0010] Furthermore, by mounting this rectifier circuit on a metal substrate to form an on-board power supply device, the amount of heat generation can be reduced and the number of heat-generating points can be reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, diodes 3 and 5 and thyristors 7 and 9 are bridge-connected to a commercial AC power supply 1. The anodes of the diodes 11 and 13 are connected to the anodes of the thyristors 7 and 9, respectively. These cathodes are commonly connected and connected to the smoothing capacitor 17 via the resistor 15. At startup,
Thyristors 7 and 9 are off because no gate signal is supplied. Therefore, the diodes 3, 5,
The smoothing capacitor 17 is charged via the resistor 15 on the path of the rectifier circuit formed by 11 and 13. The charging current of the charging current is limited by the resistor 15. Then, when the charging voltage of the smoothing capacitor 17 reaches a predetermined value, the gate signals of the thyristors 7 and 9 are supplied and turned on. Until now, the thyristors 7 and 9 have a higher current path than the current paths flowing through the diodes 11 and 13 and the resistor 15.
Since the voltage drop is lower in the path, the current path is switched. That is, only the voltage drop of the diode 3 or 5 and the thyristor 7 or 9 of the rectifier circuit is required.

FIG. 2 shows a rectifier circuit having an inrush current prevention function according to the present invention, which is a center tap dual-wave rectifier circuit.

FIG. 3 shows a rectifier circuit having an inrush current prevention function according to the present invention, which is a three-phase bridge rectifier circuit.

In the rectifier circuit having an inrush current prevention function according to the present invention described above, the diodes connected in series with the inrush current prevention resistor 15 are provided on the AC input side of each rectifier circuit. Thus, the start-up speed becomes faster and a smoother operation can be obtained. However, at least one diode functions at least.

FIG. 4 is an embodiment of an on-board power supply according to the present invention. The on-board power supply receives the commercial AC power supply 1, temporarily rectifies the power, and generates a predetermined DC voltage output by a chopper circuit based on high-frequency switching. The circuit is mounted on a single metal substrate. However, the resistor 15 for preventing inrush current, which loses relatively large power, and the output smoothing capacitor are externally connected.

The diodes 3 and 5 and the thyristors 7 and 9 are bridge-connected to the commercial AC power supply 1. The anodes of the diodes 11 and 13 are respectively connected to thyristors 7
And 9 are connected to the anode, and these cathodes are connected in common and connected to the smoothing capacitor 17 via the resistor 15. At the time of startup, the thyristors 7 and 9 are off because no gate signal is supplied. Therefore, the smoothing capacitor 17 is charged via the resistor 15 on the path of the rectifier circuit formed by the diodes 3, 5, 11, and 13. The inrush current of this charging current is limited by the resistor 15.

The positive pole of the smoothing capacitor 17 is connected to one end of an inductor 21, and the other end of the inductor 21 is connected to a FET 23 which is a switching element of a chopper circuit.
, And to the output terminal 109. The negative pole of the smoothing capacitor 17 is connected to the FET 23
And to the output terminal 111. A smoothing capacitor 20 and a load 19 are connected to the outside between the output terminals 109 and 111. FE
The drive circuit 25 is connected to the gate of T23,
It supplies necessary drive signals as a chopper circuit.

A series circuit of the winding n 1 of the transformer 27 and the switching circuit 29 is connected between the output terminals 109 and 111. The switching circuit 29 is a semiconductor integrated circuit called a so-called intelligent power device including a high-frequency switching circuit and a constant voltage control function. For example, a TOP210 model from Power Integrations or equivalent can be used.
The switching circuit 29 is activated when the voltage between the terminals 109 and 111 becomes equal to or higher than a predetermined value, and operates so that the output voltage thereof also maintains the set value. The high frequency conversion is performed by the switching circuit 29, and the voltage of the winding n1 of the transformer 27 is transformed to the windings n2 and n3. The voltage of the winding n3 is determined by the diode 33 and the capacitor 37.
Rectified and smoothed to a lower DC voltage and supplied to each circuit. The voltage of the winding n2 is rectified and smoothed to a low DC voltage by the diode 31 and the capacitor 35, and an ON signal is supplied to the gates of the thyristors 7 and 9 via the resistors 43 and 45, respectively. Note that the capacitor 39 and the resistor 41 are circuits for adjusting the time constant.

Before this state, the current is limited because the main circuit is operating via the resistor 15. When an ON signal is supplied to the gates of the thyristors 7 and 9, the voltage of the thyristors 7 and 9 is lower than that of the current flowing through the diodes 11 and 13 and the resistor 15. , The current path switches. After that, a bridge rectifier circuit composed of the diodes 3, 5 and the thyristors 7, 9 in the ON state constitutes a main circuit. When the thyristor is turned on, the voltage drop between its anode and cathode becomes almost the same as that of a general diode, so that the power loss can be kept low.

[0018]

Since the present invention has the above-described features, it is possible to reduce the voltage drop of the main circuit in a steady state and improve the efficiency. In addition, the amount of heat generated can be reduced, and the number of heat generating points can be reduced, and the temperature distribution on the heat radiation of the on-board power supply is also leveled, and it is desired that the size and reliability be improved. There is.

[Brief description of the drawings]

FIG. 1 shows a rectifier circuit having an inrush current prevention function according to the present invention.

FIG. 2 shows a rectifier circuit having an inrush current preventing function according to the present invention, which is a center tap dual-wave rectifier circuit.

FIG. 3 shows a rectifier circuit having an inrush current prevention function according to the present invention, which is a three-phase bridge rectifier circuit.

FIG. 4 shows an on-board power supply according to the present invention.

FIG. 5 shows a conventional inrush current prevention circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Commercial AC power supply 3 ... Diode 5 ... Diode 6 ... Transformer 7 ... Thyristor 9 ... Thyristor 11 ... Diode 13 ... Diode 15 ... Resistor 17 ... Capacitor 19 ... Load 20 ... Capacitor 21 ... Inductor 23 ... FET 25 ... Drive circuit 27: Transformer 29: Switching circuit 31: Diode 33
... Diode 35 ... Capacitor 37 ... Capacitor 39 ... Capacitor 41 ... Resistor 43 ... Resistor 45 ... Resistor 53 ... Diode 55 ... Diode 59 ... Thyristor 100 ... On-board power supply

Claims (2)

[Claims] A rectifier circuit having a commercial AC power supply as an input, wherein one of the arms of the rectifier circuit is constituted by a diode and the other is constituted by a thyristor, and a rush current flows between an input terminal and an output terminal of the rectifier circuit. A rectifier circuit having an inrush current prevention function, comprising a prevention resistor and a diode. 2. A rectifier circuit having a commercial AC power supply as an input, wherein one of each arm of the rectifier circuit is constituted by a diode and the other is constituted by a thyristor, and a rush current is supplied between an input terminal and an output terminal of the rectifier circuit. An on-board power supply device comprising a rectifier circuit having an inrush current prevention function having a prevention resistor and a diode mounted on a metal substrate.