JPS59165957A - Snubber circuit of power converter - Google Patents

Abstract

PURPOSE:To reduce power loss by discharging a snubber capacitor by the induced voltage and its leakage reactance of an auxiliary winding provided in an electromagnetic part and effectively recovering the discharged energy. CONSTITUTION:When a switching element 3 is ON, energy stored in a reactor 3 is discharged through a rectifying diode 4 to a smoothing condenser 5 in case that the element 3 becomes OFF. One end of an auxiliary winding n3 provided with a reactor 2 is connected to a snubber capacitor 6, and the other end of the winding n3 is connected to one end of the condenser 5 through a discharging diode 8. When the element 3 is ON, approx. double of voltage variation of the induced voltage is generated in the capacitor 6 by the vibration of half cycle of the leakage reactance and the capacitor 6 in the winding n3, and the capacitor 6 is discharged. The energy discharged from the capacitor 6 and the winding n3 is recovered by the condenser 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charging/discharging snubber circuit used in a power converter such as a DC-DC converter.

As shown in Figure 6, the charging/discharging snubber circuit is a circuit consisting of a capacitor C and a resistor R connected in parallel to a semiconductor switch T using a transistor, thyrisk, etc. When the switch T is turned off, the capacitor C is charged. The switch is designed to suppress the sudden rise in voltage (av/d, t) between the switch poles, and to prevent overcurrent from flowing during discharge when the switch is still on. In the figure, the resistance R
A diode connected in parallel to 2 is shown.

Incidentally, the charging/discharging energy of the charging/discharging snubber capacitor C is generally wasted due to consumption of the resistor R, but in recent years, there has been a need to recover this charging/discharging energy in order to save energy and downsize equipment. It's increasing.

In particular, in the field of DC-DC converters, the switching frequency can reach 20 Hz or more, and recovery of the charging and discharging energy as described above is an important issue for improving conversion efficiency.

The purpose of the present invention was invented to satisfy these requirements, and it is possible to drastically reduce power loss compared to the conventional method.As a result, by providing a sufficiently large snubber, the duty of the switching element is reduced, and a large current can be generated. An object of the present invention is to provide a snubber circuit for a power converter that can switch at high frequencies.

According to the present invention, this object is achieved by forming a snubber circuit with an auxiliary winding and a capacitor provided on the electromagnetic component in a power converter that combines a semiconductor switching element and electromagnetic components such as a transformer and a reactor. This is achieved by connecting one end of the winding to a snubber energy recovery means via a discharge diode.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, and FIG. 2 is a time chart showing its operation.

The circuit shown in Figure 1 is a DC-D circuit usually called a flybank type.
This is an example of a C converter. When a switching element 3 using a semiconductor such as a transistor is turned on, the energy accumulated in a reactor 2 is released through a rectifier diode 4 to a smoothing capacitor 5 when the switching element 3 is turned off. The input/output voltage is switched to switching element 3.
The on-duty can be adjusted.

In the figure, 1 is an input power supply, 4 is a rectifier diode, 5 is a smoothing capacitor, 6 is a snubber capacitor, and 7 is a snubber diode. It forms a discharge snubber section.

One end of an auxiliary winding n3 provided on the reactor 2 was connected to the snubber capacitor 6, and the other end of this auxiliary winding n3 was connected to one end of the smoothing capacitor 5 via a discharge diode 8.

Note that instead of the reactor 2, electromagnetic parts such as a transformer or a motor may be used.

In this way, as shown in FIG. 2, when the switching element 3 is off, the voltage e3 rises, and at that time, the current 176 flows from the diode 7 to the capacitor 6, which is responsible for turning off the switching element 3. is reduced.

When such operation is completed, the voltage 11 of the capacitor 6
Since &-4 is charged to a voltage of approximately V (input voltage) and 10 Vo (output voltage), it must be discharged before the next turn-off.

In the present invention, the electromotive force generated in the auxiliary winding n3 is used to discharge the capacitor 6 at the moment the switching element 3 is turned on, instead of wasting energy with a resistor or the like as in the conventional case.

That is, the auxiliary winding n3 has vi + v when the switching element 3 is on. If the number of turns is set so that a voltage en3 of about % is induced, the leakage reactance L3 in n3
Due to the half-cycle vibration between the capacitor 6 and the capacitor 6, a voltage change approximately twice the induced voltage occurs in the capacitor 6, and the capacitor 6 is discharged. At this time, capacitor 6 and auxiliary winding n
Almost all of the energy released from the capacitor 3 is recovered by the smoothing capacitor 5 through the diode 8.

The current at this time is indicated by 18 in the figure and is as follows.

Completion time T-πE7 peak current IB max#, mfuji'a (,"l+
VO, )/2 Note that in order for the above discharge operation to be performed properly, the induced voltage of the auxiliary winding n3 must be Vi+
Vo, the discharge completion time T is shorter than the on time of the switching element 3, and the peak current i
6max is required to be sufficiently smaller than the allowable current of the switching element 3.

Further, FIGS. 3 to 5 are circuit diagrams showing other embodiments of the present invention, and FIG. 3 shows an example of application to an isolated converter.
The auxiliary winding n3 was connected to a snubber energy recovery circuit 9 via a discharge diode 8.

This snubber energy recovery circuit 9 serves as an auxiliary power supply circuit for the input power supply 1.

FIG. 4 shows an example of application to a step-up converter, and FIG. 5 shows an example of application to a step-down converter.

Furthermore, it is also possible to apply the present invention to power converters other than those shown.

As described above, the snubber circuit of the power converter of the present invention is
In power converters that combine semiconductor switching elements and electromagnetic parts such as transformers and reactors, the snubber capacitor is discharged by the induced voltage and leakage reactance of the auxiliary windings installed in the electromagnetic parts, and the released energy is effective. As a result, power loss can be significantly reduced compared to conventional methods, and as a result, a sufficiently large snubber is provided to reduce the duty of the switching element, making it possible to switch large currents at high frequencies. It is something.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a first embodiment of the snubber circuit of the present invention, Fig. 2 is a waveform diagram showing the operation of the circuit shown in Fig. 1, and Figs. 3 to 5 are circuits showing other embodiments. 6 are circuit diagrams showing general examples of snubber circuits. ]...Human power supply 2...Reactor 3...
Switching element 4... Rectifier diode 5... Smoothing capacitor 6...
・Snubber capacitor 7...Snubber diode 8...Discharge diode 9...Snubber energy recovery circuit n3...Auxiliary winding Applicant: Fuji Electric Manufacturing Co., Ltd. Patent attorney Tsukasa Kubo a==,,I −J′
``'1・. 1・・ 1 1-Ko, -KoFigure 1Figure 3Figure 5

Claims (3)

[Claims] (1) In a power converter that combines a semiconductor switch element and electromagnetic parts such as a transformer and a reactor, a snubber circuit is formed by an auxiliary winding provided on the electromagnetic part and a capacitor, and one end of the auxiliary winding is discharged. A power converter solar power converter circuit characterized in that it is connected to solar energy recovery means via a diode. (2) The snubber circuit for a power converter according to claim 1, wherein the snubber energy recovery means is a smoothing capacitor provided in the power converter. (3) The snubber circuit for a power converter according to claim 1, wherein the snubber energy recovery means is an auxiliary power supply circuit for an input power source of the power converter.