CN101453170B - A discrete component power supply circuit - Google Patents

Abstract

The invention discloses a power supply circuit for discrete components, including a power supply circuit for discrete components, including a transformer T1, a switching power supply MOS tube Q2, a switching power supply MOS tube connected to the MOS tube Q2 driving a back pumping circuit, and a switch connected to the back pumping circuit The power supply MOS tube driving circuit, the switching power supply output voltage feedback circuit connected to the output terminal out of the switching power supply, and the control circuit of the switching power supply. The discrete component power supply circuit of the present invention is composed of separate components, has a simple circuit structure, saves an expensive integrated circuit IC, and has low cost, thereby reducing the production cost of the TV set.

Description

A discrete component power supply circuit

【Technical field】

The invention relates to the technical field of television sets, in particular to a power supply circuit of discrete components manufactured by using discrete components.

【Background technique】

At present, TV sets have been popularized as a consumer electronic product, and consumers have increasingly strict technical requirements for TV sets. As an important part of the TV, the TV power circuit has more and more design requirements. At present, most of the switching power supplies of TVs use chips to drive the light-on tubes, drive the chips to output pulses, and drive MOS tubes to make the whole circuit work. The peripheral circuit of the driver chip includes oscillation circuit, power supply circuit, soft start circuit, self-locking circuit, frequency setting circuit and other circuits, which require many components and the peripheral circuit is complex. In addition, using a high-priced voltage regulator IC as the feedback detection circuit requires a separate chip power supply circuit, and an RCD absorption circuit needs to be added to the drain of the switch tube, resulting in relatively high costs, which in turn increases the production of the TV set. cost.

【Content of invention】

In order to solve the above problems, the main purpose of the present invention is to provide a power supply circuit for discrete components with simple circuit and low cost.

To achieve the above object, the technical solution of the present invention is:

A power supply circuit for discrete components, including a power supply circuit for discrete components, including a transformer T1, a switching power supply MOS tube Q2, a switching power supply MOS tube connected to the MOS tube Q2 to drive a back pumping circuit, and a switching power supply MOS tube connected to the back pumping circuit The driving circuit, the switching power supply output voltage feedback circuit connected to the output terminal out of the switching power supply, and the control circuit of the switching power supply.

Compared with the prior art, the discrete component power supply circuit of the present invention is composed of separate components, the circuit structure is simple, the expensive integrated circuit IC is omitted, and the cost is lower, thereby reducing the production cost of the TV set.

【Description of drawings】

FIG. 1 is a schematic circuit diagram of a power supply circuit for discrete components of the present invention.

【Detailed ways】

Please refer to Fig. 1, a power supply circuit for discrete components of the present invention includes a transformer T1, a switching power supply MOS tube Q2, a reverse pumping circuit 2 driven by a switching power supply MOS tube connected to the MOS tube Q2, and connected to the reverse pumping circuit 2 The switching power supply MOS tube drive circuit 3, the switching power supply output voltage feedback circuit 4 connected to the output terminal out of the switching power supply, and the control circuit 1 of the switching power supply. Among them, the rectified DC voltage of the AC mains is respectively input from the Vin terminal to the eleventh pin of the transformer T1 and the voltage divider circuit composed of resistors R1, R2, R3, R4, and R5. The control circuit 1 is connected between the resistor R4 and the resistor R5 of the voltage dividing circuit. The gate of the switching power supply MOS transistor Q2 is also connected between the resistor R4 and the resistor R5, and one end of the resistor R5 is grounded. The source of the switching power supply MOS transistor Q2 is grounded, and the drain is connected to the ninth pin of the transformer T1. The reverse pumping circuit 2 is connected to the gate of the MOS transistor Q2 through a capacitor C2. The output voltage feedback circuit 4 is connected with the MOS tube drive circuit 3 through an optocoupler.

The control circuit 1 includes a transistor Q1 and a diode D1. Wherein, the transistor Q1 is an NPN transistor, the anode of the diode D1 is connected between the resistors R4 and R5 , the cathode is connected to the collector of the transistor Q1 , and the emitter of the transistor Q1 is grounded. The reverse pumping circuit 2 includes a diode D2, a resistor R6 connected in series with the diode D2, and a resistor R7 connected in parallel with the series circuit formed by the diode and the resistor R6.

The MOS transistor driving circuit 3 includes a transistor Q3, a capacitor C3 with one end connected to the base of the transistor Q3 and the other end grounded, and a resistor R8. The transistor Q3 is an NPN transistor, its collector is connected to the gate of the MOS transistor Q2, and its emitter is grounded. In addition, the collector and the base of the triode Q3 are respectively connected to different pins of the optocoupler. The output voltage feedback circuit 4 includes a transistor Q4 and a voltage dividing circuit connected to the base of the transistor Q3. The voltage dividing circuit includes a resistor R18 , a resistor R19 , a resistor R20 , a sliding resistor VR1 and a resistor R21 with one end grounded. The collector of the triode Q3 is connected to the optocoupler, and the emitter is connected to a Zener diode ZD1 with one end grounded.

When the transistor Q1 in the control circuit 1 is turned on, the switching power supply does not work, and the DC part has no voltage output; otherwise, when the transistor Q1 is turned off, the switching power supply works. Specifically, the DC voltage Vin after the rectification of the AC mains is divided by the resistors R1, R2, R3, R4, and R5. The gate voltage of the MOS transistor Q2 is the voltage on the resistor R5, and the MOS transistor Q2 is turned on. The circuit The medium current direction flows from the 11th pin to the 9th pin of the winding in the transformer T1. At the same time, the 11th pin and the 8th pin of the transformer T1 are terminals with the same name, so the 8th pin of the transformer T1 has a voltage output, and the 23rd pin of the secondary winding of the transformer T1 has no voltage output. The output current of the 8th pin of the transformer T1 turns on the transistor Q3 through the diode D3 and the resistor R10, and charges the capacitor C2, the capacitor C3, and the capacitor C4 at the same time. Transistor Q3 is turned on to pull the gate voltage of MOS transistor Q2 to a low potential, MOS transistor Q2 is turned off, no current flows in the 11th-9th winding of transformer T1, the 8th pin of transformer T1 has no voltage output, and the voltage of transformer T1 The energy stored in the 23rd-45th winding of the secondary winding is released, outputting a 60V DC voltage, and this state lasts until the MOS transistor Q2 is turned on again; when the electricity in the capacitor C2, capacitor C3, and capacitor C4 is completely discharged, the transistor Q3 is turned off, MOS transistor Q2 is turned on again. Repeat the above state to achieve a stable 60V DC voltage output at the output terminal.

The current in capacitor C3 and capacitor C4 is quickly released to the ground through resistor R12, diode D4, and winding 8-9 of transformer T1, and capacitor C2 is quickly discharged to ground through diode D2, resistor R6, and winding 8-9 of transformer T1. Lose. The capacity of capacitor C3 and capacitor C4 determines the turn-off time of MOS transistor Q2. The larger the capacity of capacitor C3 and capacitor C4 within a certain range, the longer the conduction time of transistor Q3 and the longer the turn-off time of MOS transistor Q2. .

The preferred embodiments described above are only illustrative and illustrative of the invention, but are not limited to any specific form disclosed, as many modifications and variations are possible.

Claims (10)

1. electric power circuit with discrete components, comprise transformer T1, Switching Power Supply metal-oxide-semiconductor Q2, it is characterized in that: include also that the Switching Power Supply metal-oxide-semiconductor that is connected with metal-oxide-semiconductor Q2 drives back suction circuit, the Switching Power Supply metal-oxide-semiconductor drive circuit that is connected with the back suction circuit, the switch power source output voltage feedback circuit of the output out that is connected in Switching Power Supply and the control circuit of Switching Power Supply.

2. electric power circuit with discrete components as claimed in claim 1 is characterized in that: the bleeder circuit that the direct voltage after the electric main rectification inputs to the 11st pin of elementary winding one end of transformer T1-promptly respectively and is made up of resistance R 1, resistance R 2, resistance R 3, resistance R 4, resistance R 5 from Vin end.

3. electric power circuit with discrete components as claimed in claim 2, it is characterized in that: described control circuit is connected with the resistance R 4 of bleeder circuit, the connected node between the R5, connected node between resistance R 4, the R5 also connects the grid of Switching Power Supply metal-oxide-semiconductor Q2, resistance R 5 one end ground connection.

4. electric power circuit with discrete components as claimed in claim 3 is characterized in that: the source ground of described Switching Power Supply metal-oxide-semiconductor Q2, drain electrode are connected to the 9th pin of the elementary winding other end of transformer T1-promptly.

5. electric power circuit with discrete components as claimed in claim 4 is characterized in that: described back suction circuit connects the grid of metal-oxide-semiconductor Q2 by a capacitor C 2; And described output voltage feedback circuit is connected with the metal-oxide-semiconductor drive circuit by optocoupler.

6. electric power circuit with discrete components as claimed in claim 5 is characterized in that: described control circuit includes triode Q1 and diode D1; Wherein, triode Q1 is a NPN type triode, and the positive pole of diode D1 is connected between resistance R 4 and the resistance R 5, and negative pole connects the collector electrode of triode Q1; And the grounded emitter of triode Q1.

7. electric power circuit with discrete components as claimed in claim 6 is characterized in that: the series circuit parallel resistor R7 that described back suction circuit includes diode D2, the resistance R 6 of connecting with diode D2 and constitutes with diode D2, resistance R 6.

8. electric power circuit with discrete components as claimed in claim 7 is characterized in that: described metal-oxide-semiconductor drive circuit includes triode Q3, and is terminated at triode Q3 base stage, the capacitor C 3 of other end ground connection and resistance R 8.

9. electric power circuit with discrete components as claimed in claim 8 is characterized in that: described triode Q3 is a NPN type triode, and its collector electrode connects the grid of metal-oxide-semiconductor Q2, grounded emitter; In addition, the collector electrode of triode Q3, base stage also are connected to the different pins of optocoupler respectively.

10. electric power circuit with discrete components as claimed in claim 9 is characterized in that: the bleeder circuit that described output voltage feedback circuit includes triode Q4 and connects triode Q4 base stage; This bleeder circuit includes the resistance R 21 of resistance R 18, resistance R 19, resistance R 20, swept resistance VR1 and an end ground connection; The collector electrode of triode Q4 is connected to optocoupler, and emitter is connected with the voltage-stabiliser tube ZD1 of an end ground connection.