CN201868933U - A primary-side feedback constant-voltage current-limiting RCC charger control circuit - Google Patents

Abstract

The utility model provides a primary side feedback's constant voltage current-limiting RCC charger control scheme, including AC input end, DC output end, the transformer that has primary winding and secondary winding, primary winding comprises main winding and secondary winding, AC input end connects primary winding, DC output end connects secondary winding directly utilizes zener diode Z1, resistance R7, electrolytic capacitor C4, rectifier diode D2 and the secondary winding of transformer to realize constant voltage output; current is limited through a resistor R3, a nonpolar capacitor C3, a resistor R5, a triode Q2 and a secondary winding of the transformer; and simultaneously, the utility model discloses a projecting pole of primary switch triode need not to lead to the fact the fried quick-witted phenomenon that the switch tube bursts easily through current detection resistance ground connection, has improved the conversion efficiency of whole product, and not only the circuit is simple, and production assembly cost is low, product convenient to use moreover, the commonality is strong.

Description

A primary-side feedback constant-voltage current-limiting RCC charger control circuit

technical field

The utility model relates to a circuit design of a battery charger, in particular to a constant voltage and current limiting RCC charger control circuit with primary side feedback.

Background technique

The constant voltage of the general battery charger control circuit is to use the photocoupler to collect the secondary voltage and current signal and feed it back to the primary to control the stability of the output voltage. If the current is limited, another control circuit needs to be added, so that the entire control circuit The structure is complex and the cost is high. Either an integrated circuit is used to control the stability of the output voltage, but the integrated circuit has disadvantages such as high cost and poor antistatic ability.

The emitter of the primary switching transistor of the general RCC charger control circuit or the source of the field effect tube has a current detection resistor to the ground. This resistor is used to detect the working current of the switching tube. When the working current of the switching tube is large When the voltage across the resistor will rise, it will be used as an over-power protection to control the output power (or as an over-current protection). The detection speed of this control method is slow, and it is easy to cause the explosion phenomenon of the switch tube bursting, and because of the increase of the current detection resistor, the conversion efficiency of the entire product is greatly reduced, and the cost is also increased accordingly.

Utility model content

In order to overcome the above-mentioned shortcomings of the prior art, the utility model provides a constant voltage and current limiting RCC charger control circuit with primary side feedback.

The technical solution adopted by the utility model to achieve the purpose of the invention is a constant voltage and current limiting RCC charger control circuit with primary side feedback, including an AC input terminal, a DC output terminal, a transformer with a primary winding and a secondary winding, and the primary The winding is composed of a main winding and an auxiliary winding. The AC input terminal is connected to the primary winding, and the DC output terminal is connected to the secondary winding. It is characterized in that: the input terminal of the main winding is connected to the live wire of the AC input terminal through a safety resistor R1 terminal, the output terminal of the main winding is connected to the collector of a switching transistor Q1, a rectifier diode D1 is provided at the neutral terminal of the AC input terminal, and an electrolytic capacitor C1 is provided between the safety resistor R1 and the rectifier diode D1, The negative pole of the electrolytic capacitor C1 is connected to the positive pole of the rectifying diode D1, the base of the switching transistor Q1 is connected to the collector of a transistor Q2 through a resistor R4, the emitter of the switching transistor Q1 is connected to the positive pole of the rectifying diode D1, and the base of the transistor Q2 The pole is connected to the anode of the rectifier diode D1 in turn through the resistor R5 and the non-polar capacitor C3, while the base of the transistor Q2 is connected to the input end of the secondary winding through the resistor R5 and the resistor R6 in turn, and the emitter of the transistor Q2 is connected to the rectifier diode D1 positive pole; a rectifier diode D2 and a resistor R7 are also arranged between the input terminal of the secondary winding and the neutral terminal, one end of the resistor R7 is connected to the ground terminal, and the other end is connected to the positive pole of the rectifier diode D2, and the rectifier diode D2 The negative pole is connected to the input terminal of the secondary winding, and the output terminal of the secondary winding is grounded; the two ends of the resistor R7 are connected in parallel with an electrolytic capacitor C4, the positive pole of the electrolytic capacitor C4 is connected to the ground terminal, and the negative pole is connected to the rectifier diode D2 Anode connection; the cathode of Zener diode Z1 is connected to the collector of triode Q2, and the anode is connected to the anode of rectifier diode D2; resistor R2 and a non-polar capacitor are sequentially connected between the insurance resistor R1 and the input terminal of the secondary winding C2 and the resistor R3, and the collector of the triode Q2 is connected between the resistor R2 and the non-polar capacitor C2.

The DC output terminal of the utility model can adopt the following circuit design, one end of the secondary winding is connected to the positive pole of the DC output terminal through a rectifier diode D3, and the negative pole of the rectifier diode D3 is connected to the negative pole of the DC output terminal. An electrolytic capacitor C5 is connected, the anode of the electrolytic capacitor C5 is connected to the cathode of the rectifier diode D3, and a resistor R8 and a light emitting diode LED are arranged between the anode and the cathode of the DC output terminal.

Preferably, the rectifier diode D3 is a Schottky rectifier diode or a fast rectifier diode.

The beneficial effects of the utility model are:

1. Eliminate the use of photocouplers to collect the voltage and current signals of the secondary winding and feed them back to the primary winding to stabilize the output voltage, and directly use the Zener diode Z1, resistor R7, electrolytic capacitor C4, rectifier diode D2, and transformers Secondary winding to achieve constant voltage output. When the output voltage rises, the energy stored in the secondary winding of the transformer increases, and the negative voltage after reverse rectification by the rectifier diode D2 rises and breaks down the Zener diode Z1, which pulls down the base voltage of the switching transistor Q1 so that the switching transistor The switching speed of Q1 is slowed down, and the duty cycle is reduced, thereby reducing the output voltage. Conversely, when the output voltage decreases, the energy stored in the secondary winding of the transformer decreases. Since the secondary winding of the transformer is in the same direction as the main winding of the transformer, the charging speed of the non-polar capacitor C2 by the secondary winding of the transformer through the resistor R3 is accelerated, and the switching speed of the switching transistor Q1 is accelerated, thereby increasing the output voltage. The resistor R7 is used to limit the current of the rectifier diode D2, control the charging speed of the electrolytic capacitor C4, and adjust the output voltage.

2. There is no need for expensive integrated circuits or other control circuits to limit the current, and the current is limited through the resistor R3, the non-polar capacitor C3, the resistor R5, the transistor Q2 and the secondary winding of the transformer. When the output current increases, the energy provided by the secondary winding of the transformer increases, and accordingly the energy of the secondary winding of the transformer also increases, and the charging speed of the capacitor C3 is accelerated through the resistor R6. The conduction time (Ton) of the transistor Q2 becomes shorter, and the switching tube Q1 The conduction time (Ton) of the circuit is also shortened so that the output current decreases. Conversely, when the output current decreases, the energy provided by the secondary winding of the transformer decreases, and accordingly the energy of the secondary winding of the transformer also decreases, and the charging speed of the non-polar capacitor C3 is reduced through the resistor R6, and the conduction time (Ton) of the transistor Q2 becomes longer. The conduction time (Ton) of the switch tube Q1 also becomes longer so that the output current increases. However, when the resistance value of the resistor R6 is adjusted to a maximum value, the charging speed of the non-polar capacitor C3 also becomes very slow, and the transistor Q2 cannot be turned on and off normally. Therefore, adjusting the resistance value of the resistor R3 and the capacity of the non-polar capacitor C3 can adjust the RC time constant to control the level of the output current, and can also limit the output power, thereby overcoming the disadvantages of high integrated circuit cost and poor antistatic ability;

At the same time, the emitter of the primary switch triode of the utility model does not need to be grounded through the current detection resistor, which avoids the explosion phenomenon that may easily cause the switch tube to burst, and improves the conversion efficiency of the entire product. Not only is the circuit simple, the production and assembly cost is low, and the product Easy to use and strong versatility.

Description of drawings

Fig. 1, the circuit schematic diagram of the utility model.

Detailed ways

The utility model will be described in detail below in conjunction with the accompanying drawings. Referring to accompanying drawing 1, a constant-voltage current-limiting RCC charger control circuit with primary side feedback includes an AC input terminal, a DC output terminal, and a transformer with a primary winding and a secondary winding. , the primary winding is composed of the main winding and the secondary winding, the AC input end is connected to the primary winding, the DC output end is connected to the secondary winding, the input end of the main winding is connected to the live wire end of the AC input end through the insurance resistor R1, and the output end of the main winding is connected to a switch The collector of the triode Q1 is connected, the neutral end of the AC input terminal is provided with a rectifier diode D1, an electrolytic capacitor C1 is provided between the safety resistor R1 and the rectifier diode D1, the negative pole of the electrolytic capacitor C1 is connected to the positive pole of the rectifier diode D1, and the switch transistor Q1 The base is connected to the collector of a transistor Q2 through the resistor R4, the emitter of the switching transistor Q1 is connected to the neutral terminal, the base of the transistor Q2 is connected to the neutral terminal through the resistor R5 and the non-polar capacitor C3 in turn, and the transistor Q2 The base is connected to the input terminal of the auxiliary winding through the resistor R5 and the resistor R6 in turn, and the emitter of the triode Q2 is directly connected to the neutral terminal; a rectifier diode D2 and a resistor R7 are arranged between the input terminal of the secondary winding and the neutral terminal, and the resistor R7 One end of the terminal is connected to the neutral terminal, the other end is connected to the anode of the rectifier diode D2, the cathode of the rectifier diode D2 is connected to the input end of the auxiliary winding, and the output end of the auxiliary winding is grounded; the electrolytic capacitor C4 is connected in parallel to both ends of the resistor R7, and the electrolytic capacitor C4 The anode of the voltage regulator diode Z1 is connected to the neutral terminal, and the cathode is connected to the anode of the rectifier diode D2; the cathode of the Zener diode Z1 is connected to the collector of the triode Q2, and the anode is connected to the anode of the rectifier diode D2; the fuse resistor R1 is connected to the input terminal of the auxiliary winding Resistor R2, non-polar capacitor C2 and resistor R3 are connected in turn, and the collector of transistor Q3 is connected between resistor R2 and non-polar capacitor C2, and one end of the secondary winding is connected to the positive pole of the DC output terminal through the rectifier diode D3. An electrolytic capacitor C5 is connected between the negative pole of the Tertky rectifier diode D3 and the negative pole of the DC output terminal, the positive pole of the electrolytic capacitor C5 is connected to the negative pole of the Schottky rectifier diode D3, and a resistor R8 and a light emitting diode are also arranged between the positive pole and the negative pole of the DC output terminal. The diode LED, the light emitting diode LED is arranged between the resistor R8 and the negative pole of the DC output terminal.

When the input power supply voltage becomes low to a certain extent, the base of the switching transistor Q1 through the resistor R2 cannot obtain the normal conduction power supply voltage and current, and the switching transistor Q1 is in an off state, so that the entire power supply has no output voltage, and the circuit in an undervoltage lockout state. When the input power supply voltage rises to a certain level, the input voltage increases the voltage and current of the Zener diode Z1 through the resistor R2, thereby breaking down the Zener diode Z1 and pulling down the base voltage of the switching transistor Q1 to an incapable level. In the normal conduction state, the switching tube is turned off and stops working, so that the entire power supply has no output voltage, and the circuit is in an overvoltage protection state.

This circuit can realize over-current protection and over-power protection through resistor R3, non-polar capacitor C3, resistor R5, transistor Q2 and transformer secondary winding. When the output current increases, the energy provided by the secondary winding of the transformer increases, and accordingly the energy of the secondary winding of the transformer also increases, and the charging speed of the non-polar capacitor C3 is accelerated through the resistor R6. The conduction time (Ton) of the transistor Q2 becomes shorter, and the switch The conduction time (Ton) of the transistor Q1 is also shortened to reduce the output current. Conversely, when the output current decreases, the energy provided by the secondary winding of the transformer decreases, and accordingly the energy of the secondary winding of the transformer also decreases, and the charging speed of the non-polar capacitor C3 is reduced through the resistor R6, and the conduction time (Ton) of the transistor Q2 becomes longer. The conduction time (Ton) of the switching transistor Q1 also becomes longer so that the output current increases. However, when the resistance value of the resistor R6 is adjusted to a maximum value, the charging speed of the non-polar capacitor C3 also becomes very slow, and the transistor Q2 cannot be turned on and off normally. Therefore, adjusting the resistance value of the resistor R3 and the capacity of the non-polar capacitor C3 can adjust the RC time constant to control the level of the output current, and can also limit the size of the output power.

The control circuit described in the utility model can be applied to battery chargers such as mobile phones, cordless phones, PDAs, digital cameras, etc., low-power adapters, auxiliary power sources such as PCs and TVs, and the like.

Finally, it should be noted that: the above embodiments are only used to illustrate the utility model rather than limit the technical solution described in the utility model; therefore although the description has described the utility model in detail with reference to the above-mentioned various embodiments, the present utility model Those skilled in the art should understand that the utility model can still be modified or equivalently replaced; and all technical solutions and improvements that do not depart from the spirit and scope of the utility model should be included in the claims of the utility model.

Claims (3)

1. the constant voltage and current limiting RCC charger control circuit of a former limit feedback, comprise ac input end, dc output end, transformer with elementary winding and secondary winding, described elementary winding is made up of main winding and auxiliary winding, described ac input end connects elementary winding, described dc output end connects described secondary winding, it is characterized in that: the input of described main winding connects the live wire end of ac input end by insurance resistance (R1), the output of described main winding is connected with the collector electrode of a switch triode (Q1), the zero line side of described ac input end is provided with a rectifier diode (D1), be provided with an electrochemical capacitor (C1) between described insurance resistance (R1) and the rectifier diode (D1), the negative pole of described electrochemical capacitor (C1) connects the positive pole of rectifier diode (D1), the base stage of switch triode (Q1) is connected to the collector electrode of a triode (Q2) by resistance (R4), the emitter of switch triode (Q1) is connected to zero line side by rectifier diode (D1), the base stage of triode (Q2) is connected to the positive pole of rectifier diode (D1) successively by resistance (R5) and polarity free capacitor (C3), the base stage of triode (Q2) is connected to the input of auxiliary winding successively by resistance (R5) and resistance (R6) simultaneously, and the emitter of triode (Q2) is connected to the positive pole of rectifier diode (D1); Also be provided with a rectifier diode (D2) and a resistance (R7) between the input of described auxiliary winding and the zero line side, one end of described resistance (R7) connects zero line side, the other end connects the positive pole of rectifier diode (D2), the negative pole of rectifier diode (D2) is connected to the input of auxiliary winding, the output head grounding of described auxiliary winding; The two ends of described resistance (R7) electrochemical capacitor (C4) in parallel, the positive pole of described electrochemical capacitor (C4) is connected with the positive pole of rectifier diode (D1), and negative pole is connected with the positive pole of rectifier diode (D2); The negative pole of voltage stabilizing didoe (Z1) connects the collector electrode of triode (Q2), the anodal positive pole that connects described rectifier diode (D2); Be connected with resistance (R2), polarity free capacitor (C2) and resistance (R3) between the input of described insurance resistance (R1) and described auxiliary winding in turn, the collector electrode of described triode (Q2) is connected between resistance (R2) and the polarity free capacitor (C2) simultaneously.

2. according to the constant voltage and current limiting RCC charger control circuit of the described a kind of former limit of claim 1 feedback, it is characterized in that: an end of described secondary winding is connected to the positive pole of described dc output end by a rectifier diode (D3), be connected with an electrochemical capacitor (C5) between the negative pole of described rectifier diode (D3) and the negative pole of described dc output end, the positive pole of described electrochemical capacitor (C5) connects the negative pole of described rectifier diode (D3), also is provided with resistance (R8) and light-emitting diode (LED) between the positive pole of described dc output end and the negative pole.

3. according to the constant voltage and current limiting RCC charger control circuit of the described a kind of former limit of claim 2 feedback, it is characterized in that: described rectifier diode (D3) is Schottky rectifier diode or fast recovery rectifier diode.

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