RU149858U1 - VOLTAGE RETURN CONVERTER WITH PROTECTIVE CIRCUIT DURING INPUT VOLTAGE - Google Patents

Abstract

1. A flyback DC-DC converter with protective shutdown during overvoltage at the input, containing the transformer primary winding connected to the first and second input terminals of the converter, a current sensor and a power switch, the control input of which is connected to the controller output, one input of which is connected to the second input the output of the converter, and the input for determining the zero voltage is connected to the first output of the control winding, while the secondary winding of the transformer h the rectifier diode is connected to an output capacitor connected to the output terminals of the converter, the second terminal of the transformer control winding is connected to the second input of the converter through the first resistor and capacitor connected in parallel and through the diode and second resistor connected in series with the connection point of the power switch and current sensor, characterized in that contains a voltage control unit, the first and second inputs of which are connected respectively to the first and second inputs of the converter, and the output the mentioned control unit is connected to the switching-off input of the controller. 2. A flyback DC-DC converter according to claim 1, characterized in that the control unit includes series-connected first and second resistors connected between the input terminals of the converter, while a zener diode and a third resistor are connected in series with the second resistor, the connection point of which is connected to the switching-off input of the controller. . A reverse-current DC-voltage converter according to claim 1, characterized in that

Description

- Field of technology

The invention relates to a conversion technique and can be used in the construction of secondary power sources, especially in conditions of instability of the power supply network.

- Prior art

Known flyback converter with current control in the primary and secondary circuits (WO 2004042906 A1, IPC H02M 3/335, published May 21, 2004).

The disadvantage of the converter is the continuous current mode of operation, which leads to increased losses in the rectifier diode and a decrease in the efficiency.

Known AC voltage stabilizer with surge protection, the disadvantage of which is the complexity of the disconnecting device with an independent low-power source (RU 2245574, IPC G05F 1/14, published January 27, 2005).

Known flyback converter with switching at zero voltage (EP 0757428, IPC H02M 1/08, published 05.02.1997).

The disadvantage of the converter is the uncontrolled increase in the current of the power switch in the starting mode with a large input capacitance and low active resistance of the transformer windings, which is typical for flyback converters with relatively high power.

A device for protecting electronic equipment against overvoltage is known, a drawback of which is the presence of an additional switching element (RU 2408121, IPC H02H 9/04, published December 27, 2010).

A device is known for automatically protecting power consumers from emergency voltage values in an electric network, comprising a switching unit, an indicating unit, a network voltage rectifier, a voltage divider, two comparators, an upper threshold threshold driver, a lower threshold threshold driver and a microprocessor (RU 2262113, IPC G01R 19/00 , published 10/10/2005).

A disadvantage of the known solution is the lack of the ability to automatically resume the electrical power of the power receiver.

Known is a quasi-resonant DC voltage converter with switching at zero voltage, containing a transformer, a current sensor, a power switch and a controller, the second terminal of the transformer control winding is connected to the second input terminal of the converter through a parallel resistor and capacitor and through a diode and a second resistor connected in series (RU 139333, IPC H02M 3/338, published 04/10/2014).

A disadvantage of the known converter is that a short-term excess of the input voltage above the calculated voltage on the key elements leads to the failure of the converter.

The last of the described analogues adopted as a prototype, as it coincides with the stated solution for most significant features.

The technical result of the claimed solution is to increase the reliability of the converter, which is achieved by turning off the power transistor of the converter when exceeding the permissible value of the input supply voltage, implemented by the introduction of a voltage control unit connected to the turning-off input of the controller.

- Detailed solution description

The device is characterized by the following set of essential features:

1. A quasi-resonant DC / DC converter with switching at zero voltage, comprising transformer primary winding connected to the first and second input terminals of the transformer, a current sensor and a power switch, the control input of which is connected to the controller output, one input of which is connected to the second input output converter, and the input for determining zero voltage is connected to the first output of the control winding, while the secondary winding of the transformer through the rectifier the diode is connected to the output capacitor connected to the output terminals of the converter, the second terminal of the transformer control winding is connected to the second input of the converter through the first resistor and capacitor connected in parallel, and through the diode and second resistor connected in series with the connection point of the power switch and current sensor, characterized in that contains a voltage control unit, the first and second inputs of which are connected respectively to the first and second inputs of the converter, and the output of the aforementioned o the control unit is connected to the off input of the controller.

In an embodiment of the claimed device, the control unit may include series-connected first and second resistors connected between the input terminals of the converter, while a zener diode and a third resistor are connected in series with the second resistor, the connection point of which is connected to the switching-off input of the controller.

In the AC / DC version of the flyback converter, two diodes are introduced into it, a diode bridge and a line filter, the inputs of which are connected to the first and second input terminals of the converter, and the outputs are to the inputs of the diode bridge, the first output of which is connected to the transformer primary winding, connected by power a key and a current sensor, and the second output with a common connection point of the input voltage control unit, controller, current sensor, capacitor and first resistor, while the first input of the control unit is input one voltage is connected to the combined cathodes of two diodes connected by anodes to the first and second input terminals of the converter.

- The list of graphic materials.

In FIG. 1 is a block diagram of a device;

in FIG. 2 is a flyback converter shown in FIG. 1 with a preferred embodiment of a voltage monitoring unit;

in FIG. 3 - a variant of the flyback AC / DC converter with a line filter and a diode bridge at the input.

The principle of operation of a flyback converter with protective shutdown during overvoltage at the input is that transistor 3 is used for protective shutdown of the converter. Moreover, the voltage at transistor 3 in the switched off state of the converter is significantly (about half) lower than the pulse voltage that occurs when the circuit operates, at the same value of the supply voltage at the inputs of the converter.

The flyback voltage converter with protective shutdown during an overvoltage at the input (Fig. 1) contains the primary winding 2 _{1 of the} transformer 2 connected to the first 1 ₁ and second 1 ₂ input terminals of the converter, the current sensor 4 and the power switch 3, the control input of which is connected to the output 5 _{3 of the} controller 5, one input 5 _{1 of} which is connected to the second input terminal 1 _{2 of the} converter, and the input 5 _{2 of} determining the zero voltage is connected to the first output of the control winding 2 ₂ , while the secondary winding is 2 ₃ tra the transformer through a rectifier diode 6 is connected to the output capacitor 7 connected to the output terminals 8 ₁ and 8 _{of the} converter ₂ , the second terminal of the control winding 2 _{2 of the} transformer 2 is connected to the second input terminal 1 _{2 of the} converter through the first resistor 9 and the capacitor 10 connected in parallel and through connected sequentially diode 11 and the second resistor 12 to the junction point of the power switch 3 and the current sensor 4, the voltage control unit 13, the first 13 ₁ and second 13 ₂ inputs of which are connected respectively to the first and second on January ₁ January ₂ inputs reobrazovatelya and 13 ₃ Voltage output control unit 13 turns off an input connected to the controller 5 ₅ 5.

The control unit 13 according to the second embodiment of the flyback DC-DC converter (Fig. 2) contains the first 18 and second 19 resistors connected in series between the input terminals 1 ₁ and 1 _{2 of the} converter and connected in series to the second resistor 19, the zener diode 20 and the third resistor 21, the connection point of which is connected with the output 13 _{3 to the} switching-off input 5 _{5 of the} controller 5.

The flyback converter according to the third embodiment for AC power supply (Fig. 3) with two diodes 16 and 17, a diode bridge 15 and a line filter 14 whose inputs are connected to the first 1 ₁ and second 1 ₂ input terminals of the converter, and the outputs to the inputs of the diode bridge 15, the positive output of which is connected in series with the primary winding 2 _{1 of the} transformer 2, the power switch 3 and the current sensor 4, and the negative output of the diode bridge is connected to a common connection point of the second input 13 ₂ of the input voltage control unit 1 3, the input 5 _{1 of the} controller 5, the current sensor 4, the capacitor 10 and the first resistor 9, while the first input 13 ₁ of the input voltage control unit 13 is connected to the combined cathodes of two diodes 16 and 17 connected by the anodes to the first 1 ₁ and second 1 ₂ input terminals of the converter.

- Work description.

The main version of the Converter (Fig. 1).

The inputs 13 ₁ and 13 _{2 of} block 13 receives the input voltage of the Converter. When this voltage is increased above the permissible level, block 13 generates a shutdown signal for the converter, which from output 13 ₃ goes to input 5 _{5 of} controller 5. By this signal, the controller stops generating control pulses of transistor 3 and puts the converter in the off state.

The voltage on the transistor 3 in the off state, i.e. in the absence of current flowing in the windings of the transformer 2 of the converter, it is significantly (approximately half) lower than the pulse voltage that occurs during operation of the circuit, with the same value of the supply voltage at the converter inputs.

The maximum voltage on the power key 3 during operation of the converter is calculated by the formula:

U ₃ = U _in + U ₇ / K + U ′, where

U ₃ - voltage in the closed state on the transistor 3,

U _I - voltage between the first 1 ₁ and second 1 ₂ inputs of the Converter,

K is the transformation ratio of transformer 2,

U ₇ - voltage of the output capacitor 7 (voltage between the outputs of the Converter 8 ₁ and 8 ₂ ),

U ′ is the voltage of the inductive surge on the primary winding 2 _{1 of the} transformer 2, arising due to the transformer not ideal.

The maximum voltage at diode 6 during operation of the converter is calculated by the formula:

U ₆ = U ₇ + U _in * K + U ″, where

U ₃ - voltage in the closed state on the transistor 3,

U _I - voltage between the first 1 ₁ and second 1 ₂ inputs of the Converter,

K is the transformation ratio of transformer 2

U ₇ - voltage of the output capacitor 7 (voltage between the outputs of the Converter 8 ₁ and 8 ₂ ),

U ″ is the voltage of the inductive emission on the secondary winding 22 of the transformer 2 g resulting from the imperfection of the transformer.

The voltage on the power switch 3 in the off state of the Converter is defined as:

U ₃ = U _I

The maximum voltage on the diode 6 in the off state of the Converter is defined as:

U ₆ = U ₇ ,

when the converter is turned off for a long time, the voltage U ₆ on the diode 6 decreases to 0, due to the discharge of the capacitor 7.

Thus, the voltage on the power switch 3 in the off state of the converter is less than U ₇ / K + U ′ when it is running, and the voltage on the diode 6 is less by the value U _in * K + U ″, or, when it is turned off for a long time state of the converter decreases to 0.

This difference is used to increase the stability of the converter circuit to increase the input voltage. In an embodiment of the voltage monitoring unit (Fig. 2), at a normal value of the input voltage, current does not flow through the zener diode 20 and, accordingly, the resistor 21. The voltage across the resistor 21 is 0, and there is no switch-off signal supplied to input 5 _{5 of} controller 5, the converter is operating. With increasing input voltage, the current flowing through the resistors 18 and 19 increases, the voltage released on the resistor 19 also increases. When the voltage across the resistor 19 reaches the breakdown level of the zener diode 20 through the zener diode 20 and, accordingly, the resistor 21 starts to flow current. A voltage is applied to resistor 21 and supplied to input 5 _{5 of} controller 5. When this voltage reaches a level sufficient to turn off controller 5, the converter is turned off and in the off state until the input voltage returns to normal.

The difference in the operation of the converter according to the third embodiment shown in FIG. 3, consists in the fact that an alternating voltage is applied to the input terminals 1 ₁ and 1 ₂ to power the converter, a diode bridge 15 is used to rectify it, and a line filter 14 is used to reduce the noise generated by the converter into the network. In the work of overvoltage protection, the property line filter to introduce a temporary delay in the passage of high-frequency voltage. The surge voltage from the input terminals 1 ₁ and 1 _{2 of the} converter is supplied to the input of block 13 through diodes 16 and 17 without delay, and to the elements of the converter circuit, primarily transistor 3, through a line filter and a diode bridge with a delay determined by the line filter. Thus, the block 13 generates a tripping signal, and the controller 5 turns off the transistor 3 earlier than the increased voltage pulse arrives at the transistor 3. As a result, the resistance of the converter to short high-voltage pulses is increased compared with the basic version.

- Industrial applicability

The design features given in the description of the flyback voltage converter with protective shutdown during overvoltage at the input are not exhaustive. Equivalent features may be used to achieve the indicated technical result. Based on the foregoing description, a prototype flyback converter was manufactured, and a positive test result of this sample in various modes was obtained.

Claims (3)

1. A flyback DC-DC converter with protective shutdown during overvoltage at the input, containing the transformer primary winding connected to the first and second input terminals of the converter, a current sensor and a power switch, the control input of which is connected to the controller output, one input of which is connected to the second input the output of the converter, and the input for determining the zero voltage is connected to the first output of the control winding, while the secondary winding of the transformer h the rectifier diode is connected to an output capacitor connected to the output terminals of the converter, the second terminal of the transformer control winding is connected to the second input of the converter through the first resistor and capacitor connected in parallel and through the diode and second resistor connected in series with the connection point of the power switch and current sensor, characterized in that contains a voltage control unit, the first and second inputs of which are connected respectively to the first and second inputs of the converter, and the output the mentioned control unit is connected to the switching-off input of the controller. 2. The flyback DC-DC converter according to claim 1, characterized in that the control unit includes series-connected first and second resistors connected between the input terminals of the converter, parallel to the second resistor, a zener diode and a third resistor are connected in series, the connection point of which is connected to the turning-off input of the controller. 3. A reverse-current DC-voltage converter according to claim 1, characterized in that two diodes, a diode bridge and a power filter are introduced into it, the inputs of which are connected to the first and second input terminals of the converter, and the outputs to the inputs of the diode bridge, the first output of which is connected to connected in series by the primary winding of the transformer, a power switch and a current sensor, and a second output with a common connection point of the input voltage control unit, controller, current sensor, capacitor and first resistor, while The output input of the input voltage control unit is connected to the combined cathodes of two diodes connected by anodes to the first and second input terminals of the converter.

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