CN1558542A - Resistor, capacitor, diode reset dual-transistor forward converter - Google Patents

Abstract

Resistor, capacitor, diode reset dual-tube forward converter includes a DC power supply, a transformer, two main switches, the drain of the first main switch is connected to the positive pole of the power supply, and the second reset branch is a diode, or the first reset branch The circuit is a diode, and the second reset branch is a circuit in which a resistor and a capacitor are connected in parallel and then connected in series with a diode, or both reset branches are connected in parallel by a resistor and a capacitor, and the source is connected to one end of the primary side of the transformer. The source of the switch is connected to the negative pole of the power supply, the drain is connected to the other end of the primary winding of the transformer, and the secondary side of the transformer is connected to the rectifier circuit. There is a first reset branch indirectly between the positive pole of the power supply and the drain of the second main switch, and a second reset branch indirectly between the negative pole of the power supply and the source of the first main switch, wherein the first reset branch is composed of a resistor and a capacitor The circuit connected in parallel and then connected in series with the diode, the voltage stress of the main switch of the converter is low, the duty cycle can be greater than 50%, the resistance loss is low, and it can be used in occasions requiring high input voltage, wide variation range and high efficiency.

Description

Resistor, capacitor, diode reset dual-transistor forward converter

Technical field

The present invention relates to a resistor, capacitor, diode (referred to as RCD) reset dual-transistor forward converter, more particularly, it relates to a power supply device including a DC/DC converter.

Background technique

The prior art resistor, capacitor, diode (referred to as RCD) reset single-transistor forward converter as shown in Fig. 1 has a simple structure and a duty cycle greater than 50%, which is suitable for a wide range of low-cost applications. However, the voltage stress of the main switch S is relatively large, usually more than twice the input voltage, so it is not suitable for high-voltage input applications. In addition, its reset method is an energy-consuming reset method, and its excitation energy is finally consumed on the resistor R. The reset resistor R needs to use a resistor with relatively high power, which not only increases the volume of the converter, but also greatly reduces the efficiency of the converter.

In order to reduce the voltage stress of the main switch, someone proposed a dual-tube forward converter as shown in Figure 2. It includes a DC power supply V _in , a transformer T _R , and two main switches S1 and S2. The drain of the main switch S1 is connected to the positive pole of the DC power supply, the source is connected to one end of the primary winding of the transformer, and the source of the main switch S2 is connected to the positive pole of the DC power supply. The negative pole of the DC power supply is connected, and the drain is connected to the other end of the primary winding of the transformer. There is a first reset branch D2 indirectly at the junction between the drain of the main switch S1 and the positive pole of the power supply and the junction between the drain of the main switch S2 and the primary winding of the transformer. There is a second reset branch D ₁ indirectly at the junction between the source of the main switch S2 and the negative pole of the power supply and the junction between the source of the main switch S1 and the primary winding of the transformer, and the secondary winding of the transformer is connected to the rectifier circuit. The voltage stress of each main switch of this converter is equal to the input voltage, which is about half of the single-transistor forward, and is suitable for high-voltage input occasions, so some people classify it as a kind of three-level converter. The dual-tube forward converter uses the input voltage to reset the transformer. The structure is also very simple, and the excitation energy is not wasted, but fed back to the input side. But this dual-tube forward converter has its fatal disadvantage: it can only work in a state where the duty cycle is less than 50%, so it is not suitable for applications with a very wide conversion range. What Fig. 3 shows is the working waveform of the two-tube forward converter. During the DT period when the main switch is turned on, the voltage on the transformer is positive V _in ; when the main switch is turned off (1-D)T time, the diodes D ₁ and D ₂ are first turned on, and the transformer is reset by the negative V _in , when the positive and negative volt-seconds are balanced, D ₁ and D ₂ are naturally turned off, and the voltage on the transformer is zero. Therefore, the transformer must meet the following conditions for volt-second balance:

V _in (1-D)≥V _in D (1)

It can be calculated from formula (1): D≤50%

Therefore, this dual-tube forward converter can only work in the region where the duty cycle is less than 50%.

Contents of Invention

The purpose of the present invention is to provide a resistance, capacitor and diode reset dual-transistor forward converter with a duty cycle greater than 50%, low switch voltage stress, high conversion efficiency, and high voltage input and wide conversion range.

To achieve the above object, the present invention has the following three technical solutions.

plan 1:

Resistor, capacitor, diode reset dual-tube forward converter, including DC power supply, transformer, first main switch, second main switch, the drain of the first main switch is connected to the positive pole of the DC power supply, and the source is connected to the primary winding of the transformer The source of the second main switch is connected to the negative pole of the DC power supply, and the drain is connected to the other end of the primary winding of the transformer. There is an indirect connection between the positive pole of the power supply and the drain of the second main switch and the primary winding of the transformer. The first reset branch has a second reset branch indirectly at the negative pole of the power supply and the contact between the source of the first main switch and the primary winding of the transformer. The secondary winding of the transformer is connected to the rectifier circuit, which is characterized by the first The reset branch is a circuit in which a resistor and a capacitor are connected in parallel and then connected in series with a diode, wherein the anode of the diode is connected to the drain of the second main switch and the contact point of the primary winding of the transformer, and the second reset branch is a diode branch. The anode of the diode is connected to the cathode of the power supply.

Scenario 2:

Resistor, capacitor, diode reset dual-tube forward converter, including DC power supply, transformer, first main switch, second main switch, the drain of the first main switch is connected to the positive pole of the DC power supply, and the source is connected to the primary winding of the transformer The source of the second main switch is connected to the negative pole of the DC power supply, and the drain is connected to the other end of the primary winding of the transformer. There is an indirect connection between the positive pole of the power supply and the drain of the second main switch and the primary winding of the transformer. The first reset branch has a second reset branch indirectly at the negative pole of the power supply and the contact between the source of the first main switch and the primary winding of the transformer. The secondary winding of the transformer is connected to the rectifier circuit, which is characterized by the first The reset branch is a diode branch, the cathode of the diode is connected to the anode of the power supply, and the second reset branch is a circuit in which a resistor and a capacitor are connected in parallel and then connected in series with the diode, wherein the cathode of the diode is connected to the source of the first main switch and the transformer The contacts of the primary winding are connected.

Option 3:

Resistor, capacitor, diode reset dual-tube forward converter, including DC power supply, transformer, first main switch, second main switch, the drain of the first main switch is connected to the positive pole of the DC power supply, and the source is connected to the primary winding of the transformer The source of the second main switch is connected to the negative pole of the DC power supply, and the drain is connected to the other end of the primary winding of the transformer. There is an indirect connection between the positive pole of the power supply and the drain of the second main switch and the primary winding of the transformer. The first reset branch has a second reset branch indirectly at the negative pole of the power supply and the contact between the source of the first main switch and the primary winding of the transformer. The secondary winding of the transformer is connected to the rectifier circuit, which is characterized by the first The reset branch is a circuit in which a resistor and a capacitor are connected in parallel and then connected in series with a diode, wherein the anode of the diode is connected to the drain of the second main switch and the contact point of the primary winding of the transformer. The second reset branch is composed of a resistor and a capacitor. A circuit in which capacitors are connected in parallel and then connected in series with diodes, wherein the cathode of the diode is connected with the source of the first main switch and the junction of the primary winding of the transformer.

In any of the solutions above, the rectifier circuit connected to the secondary winding of the transformer may be a half-wave rectifier circuit, a zero-type half-wave rectifier circuit, a current-doubler rectifier circuit, a bridge-type full-wave rectifier circuit, or a synchronous rectifier circuit. The rectifiers in each rectification circuit can be diodes or synchronous rectifier tubes.

The RCD reset dual-transistor forward converter of the present invention combines the advantages of the traditional RCD reset single-transistor forward converter and the traditional dual-transistor forward converter in one, and it has the advantages that the duty cycle can be greater than 50% and the switch voltage stress is low , and has high conversion efficiency and wide conversion range. It is suitable for occasions with high voltage input and wide conversion range.

Description of drawings

Fig. 1 is the circuit diagram of the RCD reset single-transistor forward converter of prior art;

Fig. 2 is the circuit diagram of the dual-tube forward converter of prior art;

Fig. 3 is the operating waveform of the dual-tube forward converter of the prior art;

Fig. 4 is a kind of specific structural circuit diagram of RCD reset double-tube forward converter of the present invention;

Fig. 5 is the operating waveform of the RCD reset double-tube forward converter of the present invention under the intermittent situation of the exciting inductance current;

Fig. 6 is the operating waveform of the RCD reset dual-tube forward converter of the present invention under the continuous condition of the exciting inductance current;

Fig. 7 is the circuit diagram of another structure of RCD reset double-transistor forward converter of the present invention;

Fig. 8 is the circuit diagram of another structure of RCD reset double-transistor forward converter of the present invention;

Fig. 9 is that the rectification circuit among the present invention is a zero-type half-wave rectification circuit diagram;

Fig. 10 is that the rectification circuit in the present invention is the double current rectification circuit diagram;

Fig. 11 is that the rectification circuit among the present invention is bridge type full-wave rectification circuit diagram;

Fig. 12 is a diagram showing that the rectification circuit in the present invention is a synchronous rectification circuit.

Detailed ways

Referring to Fig. 4, Fig. 4 is a specific circuit diagram of the RCD reset dual-transistor forward converter of the present invention. It includes a DC power supply V _in , a transformer T _R , a first main switch S ₁ , a second main switch S ₂ , the drain of the first main switch S ₁ is connected to the positive pole of the DC power supply, and the source is connected to one end of the primary winding of the transformer The source of the second main switch _S2 is connected to the negative pole of the DC power supply, and the drain is connected to the other end of the primary winding of the transformer _. Indirectly there is a first reset branch 110, the first reset branch is a circuit in which the resistor _R1 and the capacitor _C1 are connected in parallel and then connected in series with the diode _D1 , wherein the anode of the diode _D1 is connected to the drain of the second main switch _S2 It is connected to the contact of the primary winding of the transformer, and there is a second reset branch 120 indirectly between the negative pole of the power supply and the contact between the source of the first main switch S ₁ and the primary winding of the transformer. The second reset branch is a diode D ₂ branch , the anode of the diode _D2 is connected to the cathode of the power supply. The secondary winding of the transformer is connected to the rectifier circuit 130 , where the rectifier circuit 130 is a half-wave rectifier circuit composed of diodes _DR1 , _DR2 , inductor L, capacitor C ₀ and resistor R ₀ . In this way, the main switch _S1 bears the input voltage; the main switch _S2 bears the reset voltage; the voltage on the capacitor _C1 is only used as the compensation part of the reset voltage, and the input voltage mainly resets the transformer, so the resistor R The loss on ₁ will be greatly reduced and the efficiency will be greatly improved.

The RCD reset dual-transistor forward converter of the present invention can be understood as a combination of a dual-transistor forward converter and an RCD reset single-transistor forward converter. The main switches _S1 and _S2 are turned on and turned off at the same time. When the main switches _S1 and _S2 are turned on, the transformer bears the input voltage, as shown in Figure 5. After the main switches S ₁ and S ₂ are turned off, the excitation current of the transformer continues to flow through the diodes D ₁ and D ₂ . The reset voltage across the transformer is then (V _in +V _c ). After the transformer volt-second balance, that is, the excitation current returns to zero, the diodes D ₁ and D ₂ are naturally turned off. The voltage on the transformer also returns to zero.

It can be seen that the reset voltage on the transformer is the superposition of the input voltage and the voltage on the capacitor _C1 . The condition for transformer volt-second balance should be rewritten as:

V _in D≤(V _in +V _c )(1-D) (2)

Available: $\mathrm{D.}\≤\frac{V_{\mathrm{in}}+V_C}{{2V}_{\mathrm{in}}+V_C}$

Right now ${\mathrm{D.}}_{\max }=\frac{V_{\mathrm{in}}+V_C}{{2V}_{\mathrm{in}}+V_C}$

If V _C is positive, then the duty cycle D can exceed 50%. Therefore this circuit can be adapted to a wide range of requirements. The difference from the single-transistor forward converter with RCD reset is that V _C here is not the entire reset voltage, but exists as a compensation for the reset voltage. The main body of the reset voltage is still V _in . In this way, the power consumed on the resistor _R1 is not all the excitation energy, but a part of the excitation energy. This just solves the biggest problem of the single-transistor forward converter with RCD reset. In addition, it can be easily seen from the figure that the voltage stress of the main switch S ₁ is V _in , and the voltage stress of the main switch S ₂ is (V _in +V _C ). V _C here is only a compensation reset voltage, the value is relatively small, so the voltage stress of S ₂ is only slightly greater than the input voltage, which is much smaller than the switch voltage stress in the single-transistor forward converter with RCD reset. Therefore, the RCD reset double-transistor forward converter of the present invention is also very suitable for occasions where the input voltage is relatively high.

The working principle of the double-transistor forward converter with RCD reset in the typical working state of the present invention is qualitatively analyzed above. The characteristics and design methods of the converter under various working conditions are described quantitatively below.

For occasions where the input voltage range is not very wide, the entire range of the circuit can be designed as an intermittent excitation current state, which is beneficial to the design of the transformer.

1. Discontinuous state of excitation current (hereinafter referred to as discontinuous state):

Work in the state of Figure 5 is the intermittent state. The field current returns to zero every cycle. If the transformer reset time is defined as t ₂ , then t ₂ <(1-D)T. Working in this state, the magnetic bias on the transformer of the two-tube forward converter with RCD reset is the smallest, which is more beneficial to the design of the transformer.

In this state, the maximum value of the excitation current I _m can be expressed as the following formula:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; DV</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}\mathrm{<span\; class="notranslate">\; T</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

According to the volt-second balance of the output filter inductor:

DV _in = nV _o (4)

Substitute (4) into (3) to get:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; nV</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}\mathrm{<span\; class="notranslate">\; T</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

For a power supply whose input voltage varies between V _inmin ~V _inmax and the output voltage is constant at V _o , I _m is a constant value.

Assume that the duty cycle corresponding to the minimum input voltage V _inmin is D _max . Then design this time so that the excitation current is just critically intermittent, that is, the reset time t2 is just equal to (1-D)T. According to this principle, the size of the resistor _R1 can be designed.

中有 $\frac{V_c}{V_{\mathrm{in}}+V_c}\&times;\frac{L_m{I_m}^2}{2}$ 灌入电压源V_C，而这部分能量最终是要消耗在电阻R₁上。所以下式成立：Because the capacitance C ₁ is relatively large, it can be regarded as a voltage source V _C in stable operation. During reset, the excitation current flows through the voltage source V _in and the voltage source V _C at the same time, so the excitation energy

There are $\frac{V_c}{V_{\mathrm{in}}+V_c}\&times;\frac{L_m{I_m}^2}{2}$ It is poured into the voltage source V _C , and this part of energy will eventually be consumed on the resistor R ₁ . So the following formula holds:

$\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

It can be seen from formula (6) that the lower the input voltage V _{in is} , the higher the voltage V _C on the capacitor C ₁ is.

According to the design principle of t2=(1-D)T when the input voltage is the lowest. The V _C corresponding to the lowest input voltage can be calculated first. V _C at this time is defined as V _Cmax . According to the volt-second balance of the transformer:

V _inmin D _max ＝(V _inmin +V _Cmax )(1-D _max ) (7)

V _Cmax can be solved from equation (7):

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}\mathrm{<span\; class="notranslate">\; min</span>}}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Substituting (3) and (8) into formula (6), we can solve R:

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

The R calculated according to this method satisfies the minimum bias on the transformer, which is the optimal design of the transformer. This design is suitable for occasions where the input voltage range is not particularly wide. If the input voltage range is very wide, then the maximum duty cycle D _max must be designed very large, and the V _Cmax designed by the above method will be relatively large, so that the voltage stress of the main switch _S2 will be relatively large, especially in When the input voltage is relatively high, it is not conducive to the selection of _S2 .

2. Continuous state of excitation current (hereinafter referred to as continuous state):

The design of the continuous state of the excitation current is analyzed below. In this way, the entire converter works in both discontinuous and continuous states, and the input voltage range can be wider without making the voltage stress of the main switch _S2 too large.

The entire duty ratio range can be divided into two sections D _min ˜D _mid ˜D _max . D _min ~ D _mid segment is the intermittent state mentioned above, t2<(1-D)T. The section D _mid ~ D _max works in a continuous state, t2 = (1-D) T, and the waveforms of its transformer voltage and excitation current are shown in Figure 6.

In the continuous state, the transformer still needs to meet the volt-second balance, but t2 is already equal to (1-D)T, so it can only be forced to increase V _C to meet the volt-second balance. At this time, it is not the magnitude of the excitation current that determines the magnitude of V _C , but the volt-second balance determines the magnitude of V _C , and then V _C determines the magnitude of the excitation current. V _C can be calculated by the following formula:

V _in D = (V _in +V _C )(1-D) (10)

The continuous state corresponds to a relatively large duty cycle, and the corresponding V _in is relatively small, so the V _C at this time will be relatively large, which will also affect the efficiency. In addition, for the transformer, it is unfavorable to work in the continuous state, and its bias magnetic field will be larger than that in the discontinuous state. Therefore, the continuous state is only designed when the input range is required to be particularly wide.

Figure 7 is a circuit diagram of another structure of the RCD reset dual-transistor forward converter of the present invention, which includes a DC power supply V _in , a transformer T _R , a first main switch S ₁ , a second main switch S ₂ , and a first main switch S The drain of ₁ is connected to the positive pole of the DC power supply, the source is connected to one end of the primary winding of the transformer, the source of the second main switch _S2 is connected to the negative pole of the DC power supply, and the drain is connected to the other end of the primary winding of the transformer. There is a first reset branch 110 indirectly at the junction of the positive pole of the power supply and the drain of the second main switch S ₂ and the primary winding of the transformer. The first reset branch is a diode D ₁ branch, and the negative pole of the diode D ₁ is connected to the power supply There is a second reset branch 120 connected between the negative pole of the power supply and the contact between the source of the first main switch _S1 and the primary winding of the transformer. The second reset branch is connected in parallel with a resistor _R2 and a capacitor _C2 and then connected to the diode A circuit in which D ₂ is connected in series, wherein the cathode of diode D ₂ is connected to the junction of the source of the first main switch S ₁ and the primary winding of the transformer. The secondary winding of the transformer is connected to the rectifier circuit 130 , where the rectifier circuit 130 is a half-wave rectifier circuit composed of diodes _DR1 , _DR2 , inductor L, capacitor C ₀ and resistor R ₀ . The working principle and characteristics of the RCD-reset dual-transistor forward converter are the same as those of the RCD-reset dual-transistor forward converter described above in FIG. 4 .

Fig. 8 is a circuit diagram of another structure of the RCD reset dual-transistor forward converter of the present invention, which includes a DC power supply V _in , a transformer T _R , a first main switch S ₁ , a second main switch S ₂ , and a first main switch S The drain of ₁ is connected to the positive pole of the DC power supply, the source is connected to one end of the primary winding of the transformer, the source of the second main switch _S2 is connected to the negative pole of the DC power supply, and the drain is connected to the other end of the primary winding of the transformer. There is a first reset branch 110 directly at the positive pole of the power supply and the junction between the drain of the second main switch _S2 and the primary winding of the transformer, and directly at the junction of the negative pole of the power supply and the source of the first main switch _S1 and the primary winding of the transformer. There is a second reset branch 120. Here, the first reset branch 110 is a circuit in which a resistor _R1 and a capacitor _C1 are connected in parallel and then connected in series with a diode _D1 , wherein the anode of the diode _D1 is connected to the second main switch _S2 The drain is connected to the contact point of the primary winding of the transformer, and the second reset branch 120 is a circuit in which the resistor R ₂ and the capacitor C ₂ are connected in parallel and then connected in series with the diode D ₂ , wherein the cathode of the diode D ₂ is connected to the first main switch S ₁ The source is connected to the junction of the primary winding of the transformer. The first reset branch and the second reset branch each have a set of capacitors and resistors, so that the compensation reset voltage can be distributed to the two capacitors, so that the voltage stress on the two main switches S ₁ and S ₂ can be distributed more evenly , which is more conducive to the selection of switches. A rectification circuit 130 is connected to the secondary winding of the transformer, which is a half-wave rectification circuit composed of diodes _DR1 , _DR2 , inductor L, capacitor C ₀ and resistor R ₀ .

The working principle and characteristics of the RCD-reset dual-transistor forward converter are the same as those of the RCD-reset dual-transistor forward converter described above in FIG. 4 .

As shown in Fig. 9, the rectification circuit connected to the secondary winding of the transformer is a zero-type half-wave rectification circuit composed of diodes _DR1 , _DR2 , inductor L, capacitor C ₀ and resistor R ₀ . In this way, the filter inductance can be reduced, and the output ripple can be significantly reduced. This structure requires two windings on the secondary side of the transformer.

As shown in Figure 10, the rectifier circuit connected to the secondary winding of the transformer is a current doubler rectifier circuit composed of diodes _DR1 , _DR2 , inductors _L1 , _L2 , capacitor _C0 and resistor _R0 . In this way, the filter inductance can be reduced, the output ripple can be significantly reduced, the secondary side of the transformer only needs one winding, and the loss on the winding will also be significantly reduced. This structure is suitable for the occasion of high current output.

As shown in Figure 11, the rectifier circuit connected to the secondary winding of the transformer is a bridge full-wave rectifier circuit composed of diodes _DR1 , _DR2 , _DR3 , _DR4 , inductor _L1 , capacitor _C0 and resistor _R0 . In this way, the filter inductance can be reduced, the output ripple can be significantly reduced, there is only one winding on the secondary side of the transformer, and the voltage stress on the diode can be reduced. This structure is suitable for high voltage output occasions.

As shown in Figure 12, the rectification circuit connected to the secondary winding of the transformer is a synchronous rectification circuit composed of synchronous rectifier tube _DR1 , _DR2 inductor L, capacitor _C0 and resistor _R0 . Generally, a drive control circuit is required to keep the rectifier _DR1 on when the main switches S ₁ and S ₂ are turned on, and to turn on the rectifier _DR2 when the main switches S ₁ and S ₂ are turned off . In this way, the loss of the rectifier circuit will be greatly reduced, and it is suitable for low voltage output occasions.

Claims (9)

1. resistance, electric capacity, diode reset two-transistor forward converter comprise DC power supply (V _In), transformer (T _R), the first main switch (S ₁), the second main switch (S ₂), the first main switch (S ₁) drain electrode link to each other with the positive pole of DC power supply, source electrode links to each other with an end of the former limit of transformer winding, the second main switch (S ₂) source electrode link to each other with the negative pole of DC power supply, the drain electrode link to each other with the other end of the former limit of transformer winding, at the positive pole and the second main switch (S of power supply ₂) be connected to first branch road (110) that resets between drain electrode and the contact of the former limit of transformer winding, at the negative pole and the first main switch (S of power supply ₁) being connected to second branch road (120) that resets between the contact of source electrode and the former limit of transformer winding, the secondary winding of transformer links to each other with rectification circuit (130), it is characterized in that said first branch road (110) that resets is by resistance (R ₁) and electric capacity (C ₁) after the parallel connection again with diode (D ₁) series connection circuit, wherein, diode (D ₁) the positive pole and the second main switch (S ₂) drain electrode links to each other with the contact of the former limit of transformer winding, second branch road (120) that resets is a diode (D ₂) branch road, this diode (D ₂) positive pole link to each other with the negative pole of power supply.

2. the two-transistor forward converter that resets according to claim 1 is characterized in that said rectification circuit (130) is by rectifier (D _R1, D _R2), inductance (L), electric capacity (C ₀) and resistance (R ₀) half-wave rectifying circuit formed or zero formula half-wave rectifying circuit or by rectifier (D _R1, D _R2), inductance (L ₁, L ₂), electric capacity (C ₀) and resistance (R ₀) current-doubling rectifier formed or by rectifier (D _R1, D _R2, D _R3, D _R4), inductance (L ₁), electric capacity (C ₀) and resistance (R ₀) full-wave bridge rectifier circuit formed or by rectifier (D _R1, D _R2), inductance (L), electric capacity (C ₀) and resistance (R ₀) circuit of synchronous rectification formed.

3. the two-transistor forward converter that resets according to claim 2 is characterized in that said rectifier is diode or synchronous rectifier.

4. resistance, electric capacity, diode reset two-transistor forward converter comprise DC power supply (V _In), transformer (T _R), the first main switch (S ₁), the second main switch (S ₂), the first main switch (S ₁) drain electrode link to each other with the positive pole of DC power supply, source electrode links to each other with an end of the former limit of transformer winding, the second main switch (S ₂) source electrode link to each other with the negative pole of DC power supply, the drain electrode link to each other with the other end of the former limit of transformer winding, at the positive pole and the second main switch (S of power supply ₂) be connected to first branch road (110) that resets between drain electrode and the contact of the former limit of transformer winding, at the negative pole and the first main switch (S of power supply ₁) being connected to second branch road (120) that resets between the contact of source electrode and the former limit of transformer winding, the secondary winding of transformer links to each other with rectification circuit (130), it is characterized in that said first branch road (110) that resets is a diode (D ₁) branch road, this diode (D ₁) negative pole link to each other with the positive pole of power supply, second resets branch road (120) by resistance (R ₂) and electric capacity (C ₂) after the parallel connection again with diode (D ₂) series connection circuit, wherein, diode (D ₂) the negative pole and the first main switch (S ₁) source electrode links to each other with the contact of the former limit of transformer winding.

5. the two-transistor forward converter that resets according to claim 4 is characterized in that said rectification circuit (130) is by rectifier (D _R1, D _R2), inductance (L), electric capacity (C ₀) and resistance (R ₀) half-wave rectifying circuit formed or zero formula half-wave rectifying circuit or by rectifier (D _R1, D _R2), inductance (L ₁, L ₂), electric capacity (C ₀) and resistance (R ₀) current-doubling rectifier formed or by rectifier (D _R1, D _R2, D _R3, D _R4), inductance (L ₁), electric capacity (C ₀) and resistance (R ₀) full-wave bridge rectifier circuit formed or by rectifier (D _R1, D _R2), inductance (L), electric capacity (C ₀) and resistance (R ₀) circuit of synchronous rectification formed.

6. the two-transistor forward converter that resets according to claim 5 is characterized in that said rectifier is diode or synchronous rectifier.

7. resistance, electric capacity, diode reset two-transistor forward converter comprise DC power supply (V _In), transformer (T _R), the first main switch (S ₁), the second main switch (S ₂), the first main switch (S ₁) drain electrode link to each other with the positive pole of DC power supply, source electrode links to each other with an end of the former limit of transformer winding, the second main switch (S ₂) source electrode link to each other with the negative pole of DC power supply, the drain electrode link to each other with the other end of the former limit of transformer winding, at the positive pole and the second main switch (S of power supply ₂) be connected to first branch road (110) that resets between drain electrode and the contact of the former limit of transformer winding, at the negative pole and the first main switch (S of power supply ₁) being connected to second branch road (120) that resets between the contact of source electrode and the former limit of transformer winding, the secondary winding of transformer links to each other with rectification circuit (130), it is characterized in that said first branch road (110) that resets is by resistance (R ₁) and electric capacity (C ₁) after the parallel connection again with diode (D ₁) series connection circuit, wherein, diode (D ₁) the positive pole and the second main switch (S ₂) drain electrode links to each other with the contact of the former limit of transformer winding, said second branch road (120) that resets is by resistance (R ₂) and electric capacity (C ₂) after the parallel connection again with diode (D ₂) series connection circuit, wherein, diode (D ₂) the negative pole and the first main switch (S ₁) source electrode links to each other with the contact of the former limit of transformer winding.

8. the two-transistor forward converter that resets according to claim 7 is characterized in that said rectification circuit (130) is by rectifier (D _R1, D _R2), inductance (L), electric capacity (C ₀) and resistance (R ₀) half-wave rectifying circuit formed or zero formula half-wave rectifying circuit or by rectifier (D _R1, D _R2), inductance (L ₁, L ₂), electric capacity (C ₀) and resistance (R ₀) current-doubling rectifier formed or by rectifier (D _R1, D _R2, D _R3, D _R4), inductance (L ₁), electric capacity (C ₀) and resistance (R ₀) full-wave bridge rectifier circuit formed or by rectifier (D _R1, D _R2), inductance (L), electric capacity (C ₀) and resistance (R ₀) circuit of synchronous rectification formed.

9. the two-transistor forward converter that resets according to claim 8 is characterized in that said rectifier is diode or synchronous rectifier.

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