CN104460812B - A Temperature Compensation Circuit for Output Rectifier Diode of Primary Side Feedback Converter - Google Patents

Abstract

The invention provides the output commutation diode temperature-compensation circuit of a kind of former limit feedback converter, comprising: unit buffer, the first resistance be directly proportional to temperature coefficient, current source and filtering circuit; Wherein, the input end of unit buffer connects a standard voltage source, and output terminal is connected with one end of the first resistance, and unit buffer is connected with the positive pole of a logic power; The other end of the first resistance is connected with one end of filtering circuit with the positive pole of current source respectively, the minus earth of current source, and be connected with the other end of filtering circuit, and filtering circuit is provided with a bucking voltage output terminal be connected for the in-phase end of the error amplifier with former limit feedback switch power-supply controller of electric.The solution of the present invention is applied in the switch power supply system of former limit feedback system, can improve the temperature characterisitic of output voltage.

Description

A Temperature Compensation Circuit for Output Rectifier Diode of Primary Side Feedback Converter

technical field

The invention relates to the technical field of basic electronic circuits, in particular to an output rectifying diode temperature compensation circuit of a primary-side feedback converter.

Background technique

In recent years, with the substantial increase in the demand for consumer electronics and the upgrading of various electronic products, people have higher and higher requirements for power supplies. The flyback converter using the primary side feedback method is widely used in low-power power supplies because of its simple structure, low cost, good electrical isolation, and small size. Converters using flyback topology are easier to achieve low standby power consumption, which makes it more and more widely used under the slogan of advocating a green and energy-saving society today. However, due to the different feedback modes, in the primary-side feedback converter, it is necessary to sample the auxiliary winding to obtain the feedback voltage. The voltage drop of the output rectifier diode is included in the voltage sampled by the auxiliary winding. When the temperature changes, the voltage drop of the output diode will change with the temperature change, thus causing the sampled voltage to be inaccurate and affecting the accuracy of the output voltage.

Contents of the invention

The technical problem to be solved by the present invention is to provide an output rectifier diode temperature compensation circuit of a primary-side feedback converter, which can improve the temperature effect of output voltage when applied in a switching power supply system of primary-side feedback mode.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

According to one aspect of the present invention, an output rectifier diode temperature compensation circuit of a primary-side feedback converter is provided, including:

A unit buffer, a first resistor proportional to the temperature coefficient, a current source and a filter circuit;

Wherein, the input end of the unit buffer is connected to a standard voltage source, the output end is connected to one end of the first resistor, and the unit buffer is connected to the positive pole of a logic power supply;

The other end of the first resistor is respectively connected to the positive pole of the current source and one end of the filter circuit, the negative pole of the current source is grounded and connected to the other end of the filter circuit, and the filter circuit is provided with a The compensation voltage output terminal connected to the same phase terminal of the error amplifier of the primary side feedback switching power supply controller.

Wherein, the unit buffer includes a first operational amplifier circuit and a second operational amplifier circuit, and the input terminal of the first operational amplifier circuit is connected to a standard voltage source, and the output terminal of the first operational amplifier circuit is connected to the second operational amplifier circuit. The input terminal of the operational amplifier circuit is connected, and the second operational amplifier circuit is connected with the positive pole of a logic power supply, and the output terminal of the second operational amplifier circuit is connected with one end of the first resistor.

Wherein, the first operational amplifier circuit is an integrated operational amplifier, the non-inverting terminal of the integrated operational amplifier is connected to a standard voltage source, the inverting terminal is connected to one end of the first resistor, and the output terminal of the integrated operational amplifier is connected to The input ends of the second operational amplifier circuit are connected.

Wherein, the second operational amplifier circuit includes a first capacitor, a second resistor and a P-type metal oxide semiconductor field effect (MOS) transistor;

Wherein, the output end of the first operational amplifier circuit is connected to the gate of the P-type MOS transistor, and the source of the P-type MOS transistor is connected to the positive pole of a logic power supply, and the first capacitor and the second The resistors are connected in series to the gate and the drain of the P-type MOS transistor, and the drain is connected to one end of the first resistor.

Wherein, the current source is a constant current source.

Wherein, the filter circuit includes a third resistor and a second capacitor, and one end of the third resistor is connected to the positive pole of the current source, and the other end is connected to one end of the second capacitor, and the second capacitor The other end is connected to the negative pole of the current source, and the other end of the third resistor is a compensation voltage output end for connecting with the non-inverting end of the error amplifier of the primary side feedback switching power supply controller.

The beneficial effects of the present invention are:

The output rectifying diode temperature compensation circuit of the primary side feedback converter of the present invention includes a unit buffer, a first resistor with a positive temperature coefficient, a current source and a filter circuit. When the temperature rises, the resistance value of the first resistor increases with the rise of temperature, but the current flowing through the first resistor remains unchanged, so the voltage drop across the first resistor increases. And because the unit buffer maintains the input standard voltage at a constant value, and the output voltage in the solution of the present invention is equal to the standard voltage value minus the voltage drop on the first resistor, so it can be drawn that the output in the solution of the present invention The voltage decreases with the increase of temperature, so as to compensate the low detection voltage caused by the output rectifier diode when the temperature increases. Similarly, when the temperature decreases, the output voltage of the solution of the present invention will increase to compensate for the increase in the detection voltage caused by the output rectifying diode when the temperature decreases.

Description of drawings

Fig. 1 shows the schematic diagram of the output rectifier diode temperature compensation circuit of the primary side feedback converter of the embodiment of the present invention;

Figure 2 shows the schematic diagram of the feedback loop of the primary side feedback switch mode power supply controller.

In the figure: 101, unit buffer; 102, filter circuit; R1, first resistor; I, current source; Vref0, standard voltage source; VDD, positive pole of logic power supply; Vref, compensation voltage output terminal; op, integrated operation Amplifier; C1, first capacitor; R2, second resistor; P1, P-type MOS tube; G, gate; S, source; D, drain; R3, third resistor; C2, second capacitor; 103, Feedback voltage detection circuit; 104, error amplifier; 105, logic control unit; 106, flyback transformer; R6, sixth resistor; R7, seventh resistor; D1, output rectifier diode; Co, output capacitor; R4, fourth resistor ; R5, the fifth resistor.

detailed description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided for more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

According to one aspect of the embodiments of the present invention, a temperature compensation circuit for an output rectifier diode of a primary-side feedback converter is provided. As shown in FIG. 1 , the circuit includes: a unit buffer 101, a first resistor proportional to the temperature coefficient R1, current source I and filter circuit 102;

Wherein, the input end of the unit buffer 101 is connected to a standard voltage source Vref0, the output end is connected to one end of the first resistor R1, and the unit buffer 101 is connected to the positive pole VDD of a logic power supply;

The other end of the first resistor R1 is respectively connected to the positive pole of the current source I and one end of the filter circuit 102, the negative pole of the current source I is grounded and connected to the other end of the filter circuit 102, and the filter circuit 102 is provided with a compensation voltage output terminal Vref for connecting with the non-inverting terminal of the error amplifier of the primary side feedback switching power supply controller.

Optionally, the current source I is a constant current source, which can make the current flowing through the first resistor R1 constant.

As shown in FIG. 1 , in the output rectifier diode temperature compensation circuit of the primary side feedback converter of the embodiment of the present invention, the unit buffer 101 keeps the voltage at one end of the first resistor R1 constant at the voltage V _i of the standard voltage source Vref0 . And because the voltage value Vo output by the compensation voltage output terminal Vref is equal to the voltage value V _i of the standard voltage source Vref0 minus the voltage drop of the first resistor R1, that is, Vo=V _i −r ₁ ·i, where r ₁ represents the first resistor The resistance value of R1, i represents the current value flowing through the first resistor R1, V _i represents the voltage value of the standard voltage source Vref0. Since R1 is a resistor with a positive temperature coefficient, when the temperature rises, _r1 increases, thus Vo decreases; when the temperature decreases, _r1 decreases, thus Vo increases.

Optionally, the unit buffer 101 includes a first operational amplifier circuit and a second operational amplifier circuit, and the input terminal of the first operational amplifier circuit is connected to a standard voltage source Vref0, and the output of the first operational amplifier circuit The terminal is connected to the input terminal of the second operational amplifier circuit, and the second operational amplifier circuit is connected to the positive pole VDD of a logic power supply, and the output terminal of the second operational amplifier circuit is connected to one terminal of the first resistor R1.

The output rectifier diode temperature compensation circuit of the primary side feedback converter of the present invention is applied in the switching power supply system of the primary side feedback mode, and the compensation voltage output terminal Vref in the embodiment of the present invention is connected to the error amplifier 104 as shown in FIG. 2 The non-inverting input terminal of the circuit can improve the temperature characteristics of the output voltage.

As shown in FIG. 2 , on the periphery of the chip, the feedback loop includes voltage dividing resistors, namely sixth resistor R6 and seventh resistor R7 , flyback transformer 106 , output rectifier diode D1 and output capacitor Co. The output voltage V _out is detected by the voltage dividing resistor externally connected to the flyback converter 106, and the calculation formula of the feedback voltage V _fb is:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; fb</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; aux</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; sec</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>$

Wherein, r6 is the resistance value of the _sixth resistor R6, r7 is the resistance value of the seventh resistor _R7 , _Naux is the number of turns of the auxiliary winding of the flyback transformer 106, and _Nsec is the number of turns of the secondary winding of the flyback transformer 106 , V _out is the output voltage, V _d1 is the conduction voltage drop of the output rectifier diode D1. In the above formula, r ₆ , r ₇ , _Naux , _Naux and V _out are all constant values, so the feedback voltage V _fb is related to the conduction voltage drop V _d1 of the output rectifier diode D1.

Since when the temperature rises, the conduction voltage drop V _d1 of the output rectifier diode D1 will decrease, so the feedback voltage V _fb will decrease; when the temperature decreases, the conduction voltage drop V _d1 of the output rectifier diode D1 will increase, Therefore, the feedback voltage V _fb will increase. It can be known that the increase or decrease of temperature will cause the feedback voltage V _fb to decrease or increase accordingly.

Inside the chip, it includes a feedback voltage detection circuit 103 , an error amplifier 104 , a logic control unit 105 , a fourth resistor R4 and a fifth resistor R5 . The chip adjusts the output voltage through the internal error amplifier 104 according to the feedback voltage. Ideally, the output voltage V _{fb_det} of the feedback voltage detection circuit 103 is equal to V _fb . The output voltage V _ea of the error amplifier 104 is:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; ea</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; Vref</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Vref</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; fb</span>}}<span\; class="notranslate">\; )</span>$

Wherein, Vref1 represents the voltage of the non-inverting input terminal of the error amplifier 104, _r4 represents the resistance value of the fourth resistor R4, and r5 represents the resistance value of the _fifth resistor R5. In the case that no temperature compensation measures are taken for the output voltage V _out , the non-inverting input terminal of the error amplifier 104 is connected to a standard voltage source. Therefore, Vref1 is a constant value at this time, and since r ₅ and r ₄ are also constant values, the output voltage V _ea of the error amplifier 104 is related to the feedback voltage V _fb . And because V _fb decreases with the increase of temperature, and increases with the decrease of temperature, V _ea decreases with the increase of temperature when no temperature compensation measures are taken for the output voltage V _out . Decrease and increase. In addition, the logic control circuit 105 generates a modulation signal to adjust the output voltage through the magnitude of the V _ea output by the error amplifier 104 , and when the V _ea is too large or too small, the output voltage will deviate from the set value.

When the output rectifier diode temperature compensation circuit of the primary side feedback converter of the embodiment of the present invention as shown in Figure 1 is connected to the non-inverting input terminal of the error amplifier 104 as shown in Figure 2 through the compensation voltage output terminal Vref, Vref1 It is equal to the output voltage Vo of the compensation voltage output terminal Vref. Due to the increase of temperature, the decrease of Vo and the decrease of V _fb are based on the formula:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; ea</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; Vo</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Vo</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; fb</span>}}<span\; class="notranslate">\; )</span>$

It can be drawn that when the temperature increases, V _ea can remain unchanged. Similarly, when the temperature decreases, V _ea remains unchanged.

Optionally, as shown in FIG. 1, the first operational amplifier circuit is an integrated operational amplifier op, the non-inverting terminal of the integrated operational amplifier op is connected to a standard voltage source Vref0, and the inverting terminal is connected to the first resistor R1. One end is connected, and the output end of the integrated operational amplifier op is connected to the input end of the second operational amplifier circuit.

Optionally, as shown in FIG. 1, the second operational amplifier circuit includes a first capacitor C1, a second resistor R2, and a P-type MOS transistor P1;

Wherein, the output end of the first operational amplifier circuit is connected to the gate G of the P-type MOS transistor P1, and the source S of the P-type MOS transistor P1 is connected to the positive pole VDD of a logic power supply, and the first A capacitor C1 is connected in series with the second resistor R2 and connected in parallel to the gate G and the drain D of the P-type MOS transistor P1, and the drain D is connected to one end of the first resistor R1.

Optionally, the filter circuit 102 includes a third resistor R3 and a second capacitor C2, and one end of the third resistor R3 is connected to the positive pole of the current source I, and the other end is connected to one end of the second capacitor C2 The other end of the second capacitor C2 is connected to the negative pole of the current source I, and the other end of the third resistor R3 is used to connect with the non-inverting end of the error amplifier of the primary side feedback switching power supply controller Compensation voltage output terminal Vref.

Of course, it can be understood that the output rectifier diode temperature compensation circuit of the primary side feedback converter in the embodiment of the present invention is not limited to the specific circuit forms of the first operational amplifier circuit, the second operational amplifier circuit and the filter circuit 102. , as long as the first operational amplifier circuit and the second operational amplifier circuit can form the unit buffer 101 and the filter circuit 102 can ensure the stability of the voltage output by the compensation voltage output terminal Vref.

What has been described above is a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications can also be made without departing from the principles described in the present invention. within the scope of protection of the invention.

Claims (6)

1. an output rectifier diode temperature compensation circuit of a primary side feedback converter, characterized in that, comprising: a unit buffer, a first resistor proportional to the temperature coefficient, a current source and a filter circuit; Wherein, the input end of the unit buffer is connected to a standard voltage source, the output end is connected to one end of the first resistor, and the unit buffer is connected to the positive pole of a logic power supply; The other end of the first resistor is respectively connected to the positive pole of the current source and one end of the filter circuit, the negative pole of the current source is grounded and connected to the other end of the filter circuit, and the filter circuit is provided with a The compensation voltage output terminal connected to the same phase terminal of the error amplifier of the primary side feedback switching power supply controller; Wherein, the inverting terminal of the error amplifier of the primary feedback switching power supply controller is connected to the feedback voltage of the rectifying diode. 2. The output rectifier diode temperature compensation circuit of the primary side feedback converter as claimed in claim 1, wherein the unit buffer comprises a first operational amplifier circuit and a second operational amplifier circuit, and the first operational amplifier circuit The input terminal of the amplifier circuit is connected to a standard voltage source, the output terminal of the first operational amplifier circuit is connected to the input terminal of the second operational amplifier circuit, and the second operational amplifier circuit is connected to the positive pole of a logic power supply, and the second operational amplifier circuit is connected to the positive pole of a logic power supply. The output end of the circuit is connected with one end of the first resistor. 3. the output rectifier diode temperature compensation circuit of primary side feedback converter as claimed in claim 2, is characterized in that, described first op-amp circuit is an integrated operational amplifier, and the non-inverting terminal of described integrated operational amplifier is connected a standard voltage source, the inverting terminal is connected to one terminal of the first resistor, and the output terminal of the integrated operational amplifier is connected to the input terminal of the second operational amplifier circuit. 4. The output rectifier diode temperature compensation circuit of the primary side feedback converter as claimed in claim 2, wherein the second operational amplifier circuit comprises a first capacitor, a second resistor and a P-type metal oxide semiconductor field effect MOS tube; Wherein, the output end of the first operational amplifier circuit is connected to the gate of the P-type MOS transistor, and the source of the P-type MOS transistor is connected to the positive pole of a logic power supply, and the first capacitor and the second The resistors are connected in series to the gate and the drain of the P-type MOS transistor, and the drain is connected to one end of the first resistor. 5. The output rectifier diode temperature compensation circuit of the primary-side feedback converter according to claim 1, wherein the current source is a constant current source. 6. The output rectifier diode temperature compensation circuit of the primary side feedback converter as claimed in claim 1, wherein the filter circuit comprises a third resistor and a second capacitor, and one end of the third resistor is connected to the The positive pole of the current source is connected, the other end is connected to one end of the second capacitor, the other end of the second capacitor is connected to the negative pole of the current source, and the other end of the third resistor is used to connect with the primary side The compensation voltage output terminal is connected to the non-inverting terminal of the error amplifier of the feedback switching power supply controller.