CN201118530Y

CN201118530Y - Improved active clamp switch circuit

Info

Publication number: CN201118530Y
Application number: CNU2007201934771U
Authority: CN
Inventors: 夏存孝; 古忠平
Original assignee: GAOXIAO ELECTRONIC CO Ltd
Current assignee: Chicony Power Technology Co Ltd
Priority date: 2007-11-22
Filing date: 2007-11-22
Publication date: 2008-09-17
Anticipated expiration: 2017-11-22

Abstract

The utility model provides an improved drive clamp switch circuit, comprising a transformer with a first winding and a second winding; a first switch; a capacitor; an impedance unit; a second switch and a rectifier. The capacitor, the impedance unit and the second switch can provide a resetting loop for the first winding; the impedance unit can reduce the current passing through the second switch to prevent the second switch from being burnt out.

Description

The improvement of active clamp switch circuit

Technical field

The utility model relates to a kind of improvement of active clamp switch circuit, especially refer to a kind of in the involution loop of first winding serial connection one impedance means flow through the electric current of switch with reduction, to avoid the improvement of the active clamp switch circuit that switch burnt.

Background technology

Please refer to Fig. 1, it shows the block schematic diagram of known forward converter.As shown in the figure, known forward converter comprises: a transformer 100, and it has one first winding 101 and-the second winding 102; One switch 110; One active clamping switch (active clamp switch) 120, it has a parasitic diode 121; And one capacitor 130 combine, and can there be a leakage inductance 103 in this

first winding

101 and 130 in this capacitor.

When above-mentioned forward converter ended at this switch 110, energy stored on this leakage inductance 103 will discharge by this active clamping switch 120 and this capacitor 130 formed involution loops, so that current potential makes zero.

Parasitic diode (body diode) 121 electric currents that can bear of general active clamping switch 120

(Io_\max \cdot n + \frac{Vin}{Lm + Lr} \cdot D \cdot Ts),

But at overcurrent protection pattern (Over Current Protection; be called for short OCP) or overload protection pattern (Over Load Protection; abbreviation OLP) under the condition; one big continuous conduction mode (Continue Conductive Mode; abbreviation CCM) electric current (Io_ocpn) will flow through transformer 100 and produce a big electric current surging (spike) when this switch 110 ends on this active clamping switch 120; this big electric current surging often surpasses the rated current of active clamping switch, and this second switch 120 will be burnt.Or some known technology is connected in series a ferrocart core (bead coil) between this active clamping switch 120 and this capacitor 130, to increase its impedance loop and then to reduce the electric current that it flows through; Perhaps some known technology is between the source electrode of this active clamping switch 120 and drain electrode and connect a desolate long-pending diode (Shocky diode), when voltage during greater than the reverse conducting voltage of this desolate long-pending diode, even this desolate long-pending diode collapses (being short circuit), flow through the electric current of this active clamping switch 120 with reduction.Only the effect of above-mentioned known technology is all quite limited, and can't effectively reduce the electric current that flows through this active clamping switch 120 and avoid this active clamping switch 120 to be burnt, the real a fly in the ointment that belongs to.

The utility model content

The purpose of this utility model is to provide a kind of improvement of active clamp switch circuit, to improve the defective that exists in the background technology.

For achieving the above object, the improvement of the active clamp switch circuit that the utility model provides, it 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 can provide this first winding, one involution loop, and this impedance means can reduce the electric current that flows through this second switch simultaneously, are burnt to avoid this second switch.

The improvement of described active clamp switch circuit, wherein this transformer is the transformer of a consequent converter.

The improvement of described active clamp switch circuit, wherein this first switch and second switch can be a power switch, and this power switch can be 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.

The improvement of described active clamp switch circuit, 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.

The improvement of described active clamp switch circuit, wherein this first switch further has a parasitic diode.

The improvement of described active clamp switch circuit, wherein this second switch further has a parasitic diode.

The improvement of described active clamp switch circuit, wherein this rectifier can be a diode.

The improvement of described active clamp switch circuit, wherein this impedance means can be reactance devices such as resistance or ferrocart core.

The improvement of described active clamp switch circuit, wherein this first control signal can be pulsewidth and adjusts signal, and this second control signal then is that reverse pulsewidth is adjusted signal.

The effect that the utlity model has:

The improvement of active clamp switch circuit of the present utility model, it is connected in series an impedance means flows through the active clamping switch with reduction electric current in the involution loop of first winding, to avoid advantages such as the active clamping switch is burnt, therefore, the improvement of active clamp switch circuit of the present utility model is than the true tool progressive of active clamp switch circuit of known technology.

Description of drawings

Fig. 1 is a schematic diagram, and it shows the block schematic diagram of known forward converter.

Fig. 2 is a schematic diagram, and it shows the block schematic diagram of the active clamp switch circuit of the utility model one preferred embodiment.

Embodiment

The improvement of active clamp switch circuit of the present utility model, it comprises: a transformer, it has one first winding and one second winding, 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 a rectifier, the one end is coupled between this capacitor and this impedance means, and the other end then is coupled to first end of this first switch; Can provide this first winding, one involution loop in order to do this capacitor, impedance means, second switch, this impedance means can reduce the electric current that flows through this second switch simultaneously, is burnt to avoid this second switch.

The improvement of active clamp switch circuit of the present utility model, feature and purpose with accompanying drawing and example in detail as after.

Please refer to Fig. 2, the block schematic diagram of the improvement of the active clamp switch circuit of its demonstration the utility model one preferred embodiment.As shown in the figure, the improvement of active clamp switch circuit of the present utility model comprises: a transformer 10, and it has one first winding 11 and one second winding 12; One first switch 20; One capacitor 30; One impedance means 40; One second switch 50; And one rectifier 60 combine.

Wherein, this transformer 10, it has one first winding 11 and one second winding 12, an and leakage inductance 13, wherein an end of this first winding 11 is coupled to the electrode input end of a power supply (Vin), this transformer 10 is for example and without limitation to the transformer of a consequent converter, for generally power supply unit is known, so do not intend giving unnecessary details at this.

This first switch 20 is one or three end assemblies, it can be any power switch, be for example and without limitation to a 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, to call the first metal oxide semiconductcor field effect transistor switch 20 in the following text, its first end is coupled to the other end of this first winding 11, 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.Wherein, the drain electrode (Drain) that this first end is this first metal oxide semiconductcor field effect transistor 20, the grid (Gate) that this second end is this first metal oxide semiconductcor field effect transistor 20, the 3rd end are the source electrode (Source) of this first metal oxide semiconductcor field effect transistor 20.In addition, this first switch 20 further has a parasitic diode 21.Wherein, this first control signal is for example and without limitation to a pulsewidth and adjusts signal.

These capacitor 30 one ends are coupled to an end of this first winding 11, in order to constitute an involution (Reset) loop with this impedance means 40, second switch 50 and this first winding 11.

One end of this impedance means 40 is coupled to the other end of this capacitor 30, can increase the impedance in this involution loop and reduce the electric current that flows through this second switch 50, is burnt to avoid this second switch 50.Wherein, this impedance means 40 is for example and without limitation to reactance devices such as resistance or ferrocart core, is to be that example is illustrated with resistance in the present embodiment, but not as limit.

This second switch 50 also is one or three end assemblies, can be provided as the active clamping switch uses, it is for example and without limitation to a 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, to call the second metal oxide semiconductcor field effect transistor switch 50 in the following text, its first end is coupled to the other end of this impedance means 40, its second end is coupled to one second control signal, and the 3rd end then is coupled to first end of this first switch 20.Wherein, the drain electrode (Drain) that this first end is this second metal oxide semiconductcor field effect transistor 50, the grid (Gate) that this second end is this second metal oxide semiconductcor field effect transistor 50, the 3rd end are the source electrode (Source) of this second metal oxide semiconductcor field effect transistor 50.In addition, this second switch 50 further has a parasitic diode 51.Wherein, this second control signal is for example and without limitation to a reverse pulsewidth and adjusts signal, and it can control its time of delay by the controller that adds (figure does not show), to prevent adjusting signal conducting simultaneously with the pulsewidth of this first control signal.

This rectifier 60, one end are coupled between this capacitor 30 and this impedance means 40, and the other end then is coupled to first end of this first switch 20, and it can be a diode or a power switch; If when considering manufacturing cost, this rectifier 60 can be selected to implement with diode, to reduce its cost.

When this first switch 20 ends, energy stored on this leakage inductance 13 will pass through this rectifier 60, capacitor 30 and this

second switch

50,30 liang of paths of impedance means 40 and this capacitor discharge, wherein, the resistance in these rectifier 60 paths is lower, therefore can flow through big electric current, the resistance in this second switch 50 and impedance means 40 paths is bigger, therefore flow through less electric current, when electric current flows through impedance means 40, pressure drop meeting on it makes a large amount of electric currents this rectifier 60 of flowing through, therefore, the electric current that can guarantee to flow through on the parasitic diode 51 of this second switch 50 is lower than its rated value, so can avoid burning this second switch 50, and reach the purpose that current potential is made zero.Therefore, the improvement of active clamp switch circuit of the present utility model is really than known technology tool progressive.

The utility model is described, is preferred embodiment, and claim category of the present utility model is not all taken off in Ju Bu change or modification and come from the technological thought of this case and be what those skilled in the art were easy to know by inference such as.

Claims

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

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;

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.