CN201118530Y - Improvement of active clamping switch circuit - Google Patents

Abstract

The utility model provides an active clamp switch circuit's improvement, it has: a transformer having a first winding and a second winding; a first switch; a capacitor; an impedance device; a second switch; and a rectifier; the capacitor, the impedance device and the second switch can provide a return circuit for the first winding, and the impedance device can reduce the current flowing through the second switch so as to prevent the second switch from being burnt.

Description

Improvement of active clamp switch circuit

technical field

The utility model relates to an improvement of an active clamp switch circuit, in particular to an active clamp switch circuit in which an impedance device is connected in series in the return circuit of the first winding to reduce the current flowing through the switch, so as to avoid the switch from being burned. Improvement of the clamp switch circuit.

Background technique

Please refer to FIG. 1 , which shows a block diagram of a conventional forward converter. As shown in the figure, the known forward converter includes: a transformer 100, which has a first winding 101 and a second winding 102; a switch 110; an active clamp switch (active clamp switch) 120, which It is composed of a parasitic diode 121 and a capacitor 130 , and there is a leakage inductance 103 between the first winding 101 and the capacitor 130 .

In the above-mentioned forward converter, when the switch 110 is turned off, the energy stored in the leakage inductance 103 will be discharged through the return loop formed by the active clamp switch 120 and the capacitor 130 to return the potential to zero.

The current that the parasitic diode (body diode) 121 of the general active clamp switch 120 can withstand $(\mathrm{Io}\_\max \&Center\; Dot;\mathrm{no}+\frac{\mathrm{Vin}}{\mathrm{L\; m}+\mathrm{Lr}}\&Center\; Dot;\mathrm{D.}\&Center\; Dot;\mathrm{Ts}),$ However, under the condition of Over Current Protection (OCP for short) or Over Load Protection (OLP for short), a large Continuous Conductive Mode (CCM for short) current (Io_ocp·n) Will flow through the transformer 100 and generate a large current spike (spike) on the active clamp switch 120 when the switch 110 is turned off, and this large current spike often exceeds the rated current of the active clamp switch, which will easily make the active clamp switch 120 The second switch 120 burns out. Or some known technologies connect an iron powder core (bead coil) in series between the active clamp switch 120 and the capacitor 130 to increase the loop impedance and reduce the current flowing through it; A Shocky diode is connected in parallel between the source and the drain of the switch 120. When the voltage is greater than the reverse conduction voltage of the Shocky diode, even if the Shocky diode collapses (i.e. short circuit), the current flowing through the Shocky diode is reduced. The current of switch 120 is actively clamped. However, the effects of the above-mentioned known technologies are quite limited, and cannot effectively reduce the current flowing through the active clamp switch 120 and prevent the active clamp switch 120 from being burned, which is a fly in the ointment.

Utility model content

The purpose of the utility model is to provide an improvement of an active clamp switch circuit to improve the defects in the background technology.

In order to achieve the above purpose, the improvement of the active clamp switch circuit provided by the utility model has:

A transformer having a first winding and a second winding, one end of the first winding is coupled to a positive input end of a power supply;

A first switch is a three-terminal component, its first end is coupled to the other end of the first winding, its second end is coupled to a first control signal, and its third end is coupled to the negative pole of the power supply input terminal;

a capacitor, one end of which is coupled to one end of the first winding;

an impedance device, one end of which is coupled to the other end of the capacitor;

A second switch is also a three-terminal component, its first end is coupled to the other end of the impedance device, its second end is coupled to a second control signal, and its third end is coupled to the first switch the first end of the; and

a rectifier, one end of which is coupled between the capacitor and the impedance device, and the other end is coupled to the first end of the first switch;

The capacitor, the impedance device and the second switch can provide a return circuit for the first winding, and at the same time, the impedance device can reduce the current flowing through the second switch to prevent the second switch from being burned.

In the improvement of the active clamp switch circuit, the transformer is a transformer of a forward converter.

The improvement of the active clamp switch circuit, wherein the first switch and the second switch can be a power switch, and the power switch can be an N-channel metal-oxide-semiconductor field-effect transistor, an N-channel junction field-effect transistor, P-channel Metal Oxide Semiconductor Field Effect Transistor or P-Channel Junction Field Effect Transistor.

The improvement of the active clamp switch circuit, wherein the first terminal is the drain of the metal oxide semiconductor field effect transistor, the second terminal is the gate of the metal oxide semiconductor field effect transistor, and the third The terminal is the source of the metal oxide semiconductor field effect transistor.

In the improvement of the active clamp switch circuit, the first switch further has a parasitic diode.

In the improvement of the active clamp switch circuit, the second switch further has a parasitic diode.

In the improvement of the active clamp switch circuit, the rectifier can be a diode.

The improvement of the active clamp switch circuit, wherein the impedance device can be a reactance device such as a resistor or an iron powder core.

In the improvement of the active clamp switch circuit, the first control signal can be a pulse width adjustment signal, and the second control signal is an inverse pulse width adjustment signal.

The utility model has the effect:

The improvement of the active clamp switch circuit of the present utility model has the advantages of connecting an impedance device in series in the return circuit of the first winding to reduce the current flowing through the active clamp switch, so as to avoid the active clamp switch from being burned, etc. , The improvement of the active clamp switch circuit of the present utility model is indeed progressive compared with the active clamp switch circuit of the known technology.

Description of drawings

FIG. 1 is a schematic diagram showing a block diagram of a conventional forward converter.

FIG. 2 is a schematic diagram showing a block diagram of an active clamp switch circuit according to a preferred embodiment of the present invention.

Detailed ways

The improvement of the active clamp switch circuit of the present invention includes: a transformer having a first winding and a second winding, one end of the first winding is coupled to a positive input end of a power supply; a first The switch is a three-terminal component, the first end of which is coupled to the other end of the first winding, the second end is coupled to a first control signal, and the third end is coupled to the negative input end of the power supply; A capacitor, one end of which is coupled to one end of the first winding; an impedance device, one end of which is coupled to the other end of the capacitor; a second switch, also a three-terminal component, whose first end is coupled to the the other end of the impedance device, the second end of which is coupled to a second control signal, and the third end is coupled to the first end of the first switch; and a rectifier, one end of which is coupled to the capacitor and the impedance device between, and the other end is coupled to the first end of the first switch; so that the capacitor, the impedance device, and the second switch can provide a return circuit for the first winding, and the impedance device can reduce the flow through the second switch current to prevent the second switch from being burned.

The improvement, features and purpose of the active clamp switch circuit of the present invention are described in detail with accompanying drawings and examples.

Please refer to FIG. 2 , which shows an improved block diagram of an active clamp switch circuit according to a preferred embodiment of the present invention. As shown in the figure, the improvement of the active clamp switch circuit of the present invention includes: a transformer 10, which has a first winding 11 and a second winding 12; a first switch 20; a capacitor 30; an impedance The device 40; a second switch 50; and a rectifier 60 are combined.

Wherein, the transformer 10 has a first winding 11 and a second winding 12, and a leakage inductance 13, wherein one end of the first winding 11 is coupled to a positive input terminal of a power supply (Vin), the transformer 10 For example, but not limited to, a transformer that is a forward converter is well known in general power supplies, so details will not be described here.

The first switch 20 is a three-terminal device, which can be any power switch, such as but not limited to an N-channel MOSFET, N-channel junction field effect transistor, P-channel MOSFET Transistor or P-channel junction field effect transistor, hereinafter referred to as the first metal oxide semiconductor field effect transistor switch 20, its first end is coupled to the other end of the first winding 11, and its second end is coupled to a first control signal, and the third end is coupled to the negative input end of the power supply. Wherein, the first terminal is the drain (Drain) of the first MOSFET 20, the second terminal is the gate (Gate) of the first MOSFET 20, and the first terminal is the gate (Gate) of the first MOSFET 20. The three terminals are the source (Source) of the first MOSFET 20 . In addition, the first switch 20 further has a parasitic diode 21 . Wherein, the first control signal is, for example but not limited to, a pulse width adjustment signal.

One end of the capacitor 30 is coupled to one end of the first winding 11 to form a reset loop with the impedance device 40 , the second switch 50 and the first winding 11 .

One end of the impedance device 40 is coupled to the other end of the capacitor 30 to increase the impedance of the reset loop and reduce the current flowing through the second switch 50 to prevent the second switch 50 from being burned. Wherein, the impedance device 40 is, for example but not limited to, a reactance device such as a resistor or an iron powder core. In this embodiment, a resistor is used as an example for illustration, but it is not limited thereto.

The second switch 50 is also a three-terminal component, which can be used as an active clamp switch, such as but not limited to an N-channel metal oxide semiconductor field effect transistor, an N-channel junction field effect transistor, a P-channel metal oxide An object semiconductor field effect transistor or a P-channel junction field effect transistor, hereinafter referred to as a second metal oxide semiconductor field effect transistor switch 50, its first end is coupled to the other end of the impedance device 40, and its second end is coupled to A second control signal, the third terminal is coupled to the first terminal of the first switch 20 . Wherein, the first end is the drain (Drain) of the second MOSFET 50, the second end is the gate (Gate) of the second MOSFET 50, and the second end is the gate (Gate) of the second MOSFET 50. The three terminals are the source (Source) of the second MOSFET 50 . In addition, the second switch 50 further has a parasitic diode 51 . Wherein, the second control signal is, for example but not limited to, an inverse pulse width adjustment signal, whose delay time can be controlled by an external controller (not shown in the figure), so as to prevent the pulse width adjustment signal of the first control signal from conduction.

The rectifier 60, one end is coupled between the capacitor 30 and the impedance device 40, and the other end is coupled to the first end of the first switch 20, which can be a diode or a power switch; if the manufacturing cost is considered , the rectifier 60 can optionally be implemented as a diode to reduce its cost.

When the first switch 20 is turned off, the energy stored in the leakage inductance 13 will be discharged through two paths of the rectifier 60, the capacitor 30 and the second switch 50, the impedance device 40 and the capacitor 30, wherein the The resistance value of the path of the rectifier 60 is relatively low, so a larger current can flow through it. The resistance value of the path of the second switch 50 and the impedance device 40 is relatively large, so a smaller current flows through it. When the current flows through the impedance device 40, its A large amount of current will flow through the rectifier 60 due to the voltage drop across the rectifier 60. Therefore, it can be ensured that the current flowing through the parasitic diode 51 of the second switch 50 is lower than its rated value, so that the second switch 50 can be avoided from burning out, and To achieve the purpose of zeroing the potential. Therefore, the improvement of the active clamp switch circuit of the present invention is indeed more progressive than the prior art.

What is described in this utility model is a preferred embodiment, for example, all partial changes or modifications derived from the technical idea of this case and easily deduced by those skilled in the art will not depart from the scope of claims of this utility model.

Claims (9)

1, a kind of improvement of active clamp switch circuit is characterized in that, has:

One transformer, it has first winding and one second winding one by one, and an end of this first winding is coupled to the electrode input end of a power supply;

One first switch is one or three end assemblies, and its first end is coupled to the other end of this first winding, and its second end is coupled to one first control signal, and the 3rd end then is coupled to the negative input of this power supply;

One capacitor, one end are coupled to an end of this first winding;

One impedance means, the one end is coupled to the other end of this capacitor;

One second switch also is one or three end assemblies, and its first end is coupled to the other end of this impedance means, and its second end is coupled to one second control signal, and the 3rd end then is coupled to first end of this first switch; And

One rectifier, one end are coupled between this capacitor and this impedance means, and the other end then is coupled to first end of this first switch;

This capacitor, impedance means, second switch provide this first winding, one involution loop, and this impedance means reduces the electric current that flows through this second switch simultaneously, avoids this second switch to be burnt.

2, the improvement of active clamp switch circuit as claimed in claim 1 is characterized in that, wherein this transformer is the transformer of a consequent converter.

3, the improvement of active clamp switch circuit as claimed in claim 1, it is characterized in that, wherein this first switch and second switch are a power switch, and this power switch is N channel mos field-effect transistor N passage junction field effect transistor, P channel mos field-effect transistor or P passage junction field effect transistor.

4, the improvement of active clamp switch circuit as claimed in claim 3, it is characterized in that, wherein this first end drain electrode that is this metal oxide semiconductcor field effect transistor, this second end is the grid of this metal oxide semiconductcor field effect transistor, and the 3rd end is the source electrode of this metal oxide semiconductcor field effect transistor.

5, the improvement of active clamp switch circuit as claimed in claim 1 is characterized in that, wherein this first switch further has a parasitic diode.

6, the improvement of active clamp switch circuit as claimed in claim 1 is characterized in that, wherein this second switch further has a parasitic diode.

7, the improvement of active clamp switch circuit as claimed in claim 1 is characterized in that, wherein this rectifier is a diode.

8, the improvement of active clamp switch circuit as claimed in claim 1 is characterized in that, wherein this impedance means is resistance or ferrocart core reactance device.

9, the improvement of active clamp switch circuit as claimed in claim 1 is characterized in that, wherein this first control signal is that pulsewidth is adjusted signal, and this second control signal then is that reverse pulsewidth is adjusted signal.

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