CN1547319A

CN1547319A - Forward circuit combining active clamping and accessory power supply circuit

Info

Publication number: CN1547319A
Application number: CNA2003101192975A
Authority: CN
Inventors: 亚刘; 刘亚; 熊代富; 姜熠; 华桂潮
Original assignee: YIBO POWER SUPPLY (HANGZHOU) CO Ltd
Current assignee: YIBO POWER SUPPLY (HANGZHOU) CO Ltd
Priority date: 2003-12-03
Filing date: 2003-12-03
Publication date: 2004-11-17
Anticipated expiration: 2023-12-03
Also published as: CN1291542C

Abstract

The invention refers to a kind of normal shock circuit which can combine the active clamp and the assistant power circuit, the invention includes the primary power circuit, the secondary circuit, active clamp circuit and the assistant power circuit, the primary circuit includes primary power MOSFET, transformer primary windings, input end capacitance, the secondary circuit includes transformer secondary windings, rectifier, fly-wheel pipe, output inductance, and output capacitance, the active clamp circuit includes an active clamp MOSFET, an active clamp windings, a capacitance. The assistant power circuit includes assistant power windings, an inductance, a capacitance, a rectifier diode and a fly-wheel diode; the active clamp winding and the assistant power winding are the same winding. The invention reduces an assistant winding, thus the circuit is more compact, and the design is easier, the power model with small volume and high power density can be realized easily.

Description

Forward converter with active clamp and auxiliary power circuit merging

Technical field

The present invention relates to field of switch power, refer to adopt the forward converter of active clamp and accessory power supply especially, specifically a kind of forward converter active clamp and auxiliary power circuit merging.

Background technology

Along with modern very lagre scale integrated circuit (VLSIC) size constantly reduces, speed improves constantly, and at the power supply to integrated circuit aspect volume miniaturization and the high power density higher requirement has been arranged thereupon also.In order to reach the requirement of this two aspect, at first must select a high efficiency, the circuit topology controlled of being easy to again simple in structure.Secondly, consider the more compact power supply of project organization from manufacturing process.Aspect manufacturing process, each power supply manufacturer generally adopts PCB (circuit printing plate) transformer to substitute traditional transformer at present.

The forward converter that carries out active clamp with the tertiary winding is widely used in isolating the DC-DC Switching Power Supply because of having foregoing circuit topology advantage.This circuit comprises former limit power circuit, secondary circuit, active clamp circuit and auxiliary power circuit, described former limit circuit comprises main power MOSFET, the former limit of transformer winding, input end capacitor, described secondary circuit comprises transformer secondary winding, rectifying tube, continued flow tube, outputting inductance and output capacitor, described active clamp circuit comprises active clamp MOSFET, active clamp winding and an electric capacity, and described auxiliary power circuit comprises accessory power supply winding, an inductance, an electric capacity, a rectifier diode and a fly-wheel diode.

As main power MOSFET S ₁During conducting, active clamp MOSFET S ₂Be in off state, the rectifier diode D of auxiliary power circuit ₁Conducting allows the energy delivery on the accessory power supply winding also simultaneously part energy to be stored into inductance L to control circuit ₁In.At main power MOSFET S ₁Blocking interval, control circuit are opened active clamp MOSFET S ₂The transformer that resets, and rectifier diode D in the auxiliary power circuit ₁Because of voltage instead is turned off partially, be stored in inductance L ₁In energy then pass through sustained diode ₂Provide energy to control circuit.

In the above-mentioned forward converter, the accessory power supply of active clamp and control circuit is realized by complete two independent parts circuit.Therefore, though this circuit has some advantages on electric property,, he make its transformer become very complicated owing to comprising a plurality of windings.Many windings PCB transformer of realizing such complexity just needs a baroque multi-layer PCB, makes the cost of power module improve greatly; What is more important, it makes that finally volume miniaturization and high power density are difficult to realize.

Summary of the invention

What the present invention will solve is the above-mentioned defective that prior art exists, and a kind of follow-on forward converter is provided, and is intended to simplify circuit structure, also can reduce the complexity and the cost of circuit simultaneously.The technical scheme that addresses the above problem employing is: with the forward converter of active clamp and auxiliary power circuit merging, comprise former limit power circuit, secondary circuit, active clamp circuit and auxiliary power circuit, described former limit circuit comprises main power MOSFET, the former limit of transformer winding, input end capacitor, described secondary circuit comprises transformer secondary winding, rectifying tube, continued flow tube, outputting inductance and output capacitor, described active clamp circuit comprises active clamp MOSFET, active clamp winding and an electric capacity, described auxiliary power circuit comprises the accessory power supply winding, an inductance, an electric capacity, a rectifier diode and a fly-wheel diode is characterized in that described active clamp winding and accessory power supply winding are same winding.

Main power MOSFET controlled by control circuit and active clamp MOSFET opens in turn and closes.As main power MOSFET S ₁During conducting, the end of the same name of auxiliary winding is for just, so rectifier diode D ₁Conducting, the energy delivery on the auxiliary winding is to control circuit and simultaneously part energy is stored into inductance L ₁In.At main power MOSFET S ₁Conduction period, active clamp MOSFET S ₂Be in off state.When main power MOSFETS ₁After being turned off, the voltage reversal on the winding of the former limit of transformer, the voltage on secondary winding and the auxiliary winding is also reverse thereupon.Rectifier diode D ₁Because of voltage instead is turned off partially, be stored in inductance L ₁In energy pass through sustained diode ₂Provide energy to control circuit.At main power MOSFET S ₁Blocking interval, control circuit are opened active clamp MOSFET S ₂Transformer is resetted.

Forward converter of the present invention, creatively the active clamp winding that will be originally separate and the accessory power supply winding of control circuit are substituted by same winding, and then active clamp circuit and accessory power supply be merged into a circuit, make circuit structure become very simple, have higher reliability, and do not bring the increase of any device voltage and current stress.The number of turn of auxiliary winding is by the required bias voltage decision of control circuit.The meaning that the present invention has reduced by an auxiliary winding is not only and is made circuit more compact, what is more important, and the design of transformer is more simple, and the power module of volume miniaturization and high power density also is easier to realize.

The present invention can be applied to circuit of reversed excitation (being particularly useful for the occasion that the former secondary high pressure of requirement is isolated) and positive circuit of reversed excitation equally.

Description of drawings

The invention will be further described below in conjunction with drawings and Examples.

Fig. 1 is the existing forward converter that carries out active clamp with the tertiary winding.

The main waveform of each point in Fig. 2 Fig. 1 circuit.

Fig. 3 is the forward converter with active clamp and auxiliary power circuit merging of the present invention.

The main waveform of each point in Fig. 4 Fig. 3 circuit.

Fig. 5 is the circuit of reversed excitation with active clamp and auxiliary power circuit merging of the present invention.

The main waveform of each point in Fig. 6 Fig. 5 circuit.

Fig. 7 is the positive circuit of reversed excitation with active clamp and auxiliary power circuit merging of the present invention.

The main waveform of each point in Fig. 8 Fig. 7 circuit.

Embodiment

Figure 1 shows that and existingly carry out the forward converter of active clamp with the tertiary winding, Fig. 2 is the main waveform of each point in the circuit, wherein V _Gs1, V _Gs2Be respectively the main power MOSFET S of forward converter ₁Gate voltage waveform and active clamp power MOSFET S ₂The gate voltage waveform; V _aAnd V _bBe respectively the voltage waveform on auxiliary source winding Na and the active clamp winding Nb; Vbias is the bias voltage of circuit.The defective of this circuit was described before this, was not repeated at this.

With reference to Fig. 3, forward converter of the present invention comprises former limit power circuit, secondary circuit, active clamp circuit and auxiliary power circuit, and described former limit circuit comprises main power MOSFET S ₁, the former limit of transformer winding Np, input end capacitor C _In, described secondary circuit comprises transformer secondary winding Ns, rectifying tube S ₄, continued flow tube S ₃, outputting inductance Lo and output capacitor Co, described active clamp circuit comprises active clamp MOSFET S ₂, active clamp winding Nc and a capacitor C ₁, described auxiliary power circuit comprises accessory power supply winding Nc, inductance L 1, a capacitor C ₂, a rectifier diode D ₁With a sustained diode ₂, as seen, described active clamp winding and accessory power supply winding are same winding Nc among the figure.

The basic functional principle of foregoing circuit is as follows:

Control circuit is controlled main power MOSFET S ₁With active clamp MOSFET S ₂Open in turn and close.During [t0, t1], main power MOSFET S ₁Conducting, the end of the same name of auxiliary winding Nc is for just, so diode D ₁Conducting, the energy delivery on the auxiliary winding Na is to control circuit and simultaneously part energy is stored into inductance L ₁In.At main power MOSFET S ₁Conduction period, active clamp MOSFET S ₂Be in off state, active clamp MOSFET S ₂On voltage as shown in Figure 4.When t=t1, main power MOSFET S ₁Be turned off.Voltage reversal on the former limit winding Np, the voltage on secondary winding Ns and the auxiliary winding Nc is also reverse thereupon.Diode D ₁Because of voltage instead is turned off partially, be stored in inductance L ₁In energy pass through sustained diode ₂Provide energy to control circuit.At main power MOSFET S ₁Blocking interval, control circuit are opened active clamp MOSFET S ₂Transformer is resetted.

Claims

1, with the forward converter of active clamp and auxiliary power circuit merging, comprise former limit power circuit, secondary circuit, active clamp circuit and auxiliary power circuit, described former limit circuit comprises main power MOSFET (S ₁), the former limit of transformer winding (Np), input end capacitor (C _In), described secondary circuit comprises transformer secondary winding (Ns), rectifying tube (S ₄), continued flow tube (S ₃), outputting inductance (Lo) and output capacitor (Co), described active clamp circuit comprises active clamp MOSFET (S ₂), active clamp winding and an electric capacity (C ₁), described auxiliary power circuit comprises accessory power supply winding, an inductance (L1), an electric capacity (C ₂), a rectifier diode (D ₁) and a fly-wheel diode (D ₂), it is characterized in that described active clamp winding and accessory power supply winding are same winding (Nc).