CN201113789Y - A kind of DC-DC converter - Google Patents

Abstract

A DC-DC converter, the DC-DC converter includes an input loop, an output loop, a transformer, an output current protection circuit, a main controller IC and a switch; the input loop and the output loop are respectively connected to the transformer The primary side and the secondary side, the output terminal current protection circuit is connected between the voltage output terminal of the output terminal loop and one input terminal of the main controller IC, the output terminal of the main controller IC is connected with the control terminal of the switch, and the switch is connected at On the main circuit of the primary side of the transformer; it is characterized in that the DC-DC converter also includes an input terminal current protection circuit, and the input terminal current protection circuit is connected between the voltage output terminal of the input terminal circuit and another input terminal of the main controller IC between. In this way, the converter can be effectively protected under various conditions such as converter output overcurrent, output short circuit, output load mutation, and input terminal voltage is too low, thereby increasing the input voltage of the DC-DC converter under normal operation. scope.

Description

A kind of DC-DC converter

technical field

The utility model relates to a DC-DC converter.

Background technique

The existing current protection for DC-DC converters is usually to add an output terminal current protection circuit between the converter output terminal circuit and the main controller IC, as shown in Figure 3, the output terminal protection circuit includes a Hall current sensor 100 , a signal amplifying circuit 110, and an isolation module 120, the isolation module 120 includes a three-terminal regulator Q2 and an optocoupler controller U1. The Hall current sensor 100 is socketed on the converter output circuit 40 to sample the output current and convert the sampled current into a voltage signal, which is transmitted to the main controller IC 80 through the signal amplification circuit 110 and the isolation module 120. When the current passing through the output loop 40 is the rated current, the above-mentioned voltage signal obtained by the main controller IC 80 is set as a reference signal, and when the voltage signal transmitted to the main controller IC 80 is greater than the above-mentioned reference signal (that is, the converter output loop The current is greater than its rated current), the main controller IC 80 adjusts the power of the output loop 40 by adjusting the duty ratio of the converter switch (not shown in FIG. 3 ), so as to achieve the purpose of current protection.

However, the above current protection circuit is only effective for the overcurrent of the converter output loop 40, for example, when the converter output is overloaded or the output loop is short-circuited. However, when the current in the input circuit of the converter exceeds its rated current, such as the input terminal of the converter is low voltage or/and the output load suddenly increases, the above-mentioned current protection circuit cannot provide overcurrent protection for the input circuit. effect.

In the prior art, there is a circuit for overcurrent protection of the DC-DC converter input circuit, such as the DC zero current induction detection protection device disclosed in CN2543257Y. The device connects a current sensor in series in the DC converter input circuit, and the current The sensor transmits the collected signal to the control circuit through the comparator and the switch amplifier circuit to realize the purpose of over-current protection for the DC converter. However, this protection device can only protect the input circuit from overcurrent, and the circuit is relatively complicated, and many components are used.

Utility model content

The purpose of this utility model is to provide a current protection circuit that can only protect the output end circuit or only the input end circuit in the prior art, and provide a current protection circuit that can protect both A DC-DC converter with a dual current protection circuit that protects the output circuit and also protects the input circuit.

In order to achieve the above object, the DC-DC converter provided by the utility model includes an input loop, an output loop, a transformer, an output current protection circuit, a main controller IC and a switch, and the input loop and the output loop are respectively connected to the transformer The primary side and secondary side of the output end current protection circuit are connected between the voltage output end of the output end loop and one input end of the main controller IC, the output end of the main controller IC is connected with the control end of the switch, and the switch is connected On the main circuit of the primary side of the transformer; wherein, the DC-DC converter also includes an input terminal current protection circuit, which is connected between the voltage output terminal of the input terminal circuit and the other input terminal of the main controller IC .

As mentioned above for the DC-DC converter, when the loop current at the input terminal exceeds its maximum rated current, for example, the input terminal of the converter is low voltage or/and the output load suddenly increases, the main controller IC controls the duty cycle of the switch , adjust the size of the input loop current to make it back below the maximum rated current to achieve the purpose of current protection. The DC-DC converter provided by the utility model has a dual current protection circuit that can protect the converter under various conditions such as converter output overcurrent, output short circuit, output load mutation, and input terminal voltage is too low. Effective protection is implemented to increase the input voltage range of the DC-DC converter under normal operation, reduce the failure probability of the DC-DC converter, and increase the reliability, safety and service life of the DC-DC converter. Reduced maintenance costs. Moreover, the input-end current protection circuit and the output-end current protection circuit in the DC-DC converter provided by the utility model share the same main controller IC, which is simpler than the prior art circuit and reduces the number of components used.

Description of drawings

Fig. 1 is the circuit schematic diagram of the utility model DC-DC converter;

Fig. 2 is the principle schematic diagram of the input terminal current protection circuit of the utility model DC-DC converter;

Fig. 3 is a schematic diagram of the principle of the output current protection circuit of the DC-DC converter of the present invention.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described.

Fig. 1 has shown the structural representation of the DC-DC converter that the utility model provides, and this DC-DC converter comprises: input end loop 30, output end loop 40, transformer 50, output end current protection circuit 60, main controller IC 80 and switch 90, the input end loop 30 and the output end loop 40 are respectively connected to the primary side and the secondary side of the transformer 50, and the output end current protection circuit 60 is connected to the voltage output end of the output end loop 40 and the main controller IC 80 Between one input terminal, the output terminal of the main controller IC 80 is connected to the control terminal of the switch 90, and the switch 90 is connected to the main circuit of the primary side of the transformer 50; wherein, the DC-DC converter also includes an input terminal current protection circuit 70. The input terminal current protection circuit 70 is connected between the voltage output terminal of the input terminal circuit 30 and the other input terminal of the main controller IC 80.

The structure of the output current protection circuit 60 is shown in FIG. 3 , including a Hall current sensor 100 , a signal amplification circuit 110 and an isolation module 120 .

The Hall current sensor 100 is socketed or connected in series with the converter output end loop 40 to sample the output current and convert the sampled current into a voltage signal.

The signal amplification circuit 110 receives the voltage signal output by the Hall current sensor 100 , amplifies the voltage signal, and outputs the amplified voltage signal to the isolation module 120 . The signal amplifying circuit 110 may be an amplifying circuit known to those skilled in the art, such as an operational amplifier, a triode, etc., preferably an operational amplifier.

The isolation module 120 includes a three-terminal regulator Q2, an optocoupler controller U1, a rectifier diode D2, a resistor R11 and a resistor R12. The anode of the rectifier diode D2 is connected to the signal output terminal of the signal amplifier circuit 110, the cathode is connected to the contact point of the resistor R11 and the resistor R12, and the other end of the resistor R11 is connected to the 2-pin of the three-terminal regulator Q2 and also connected to the DC-DC converter The negative output terminal of the voltage; the other end of the resistor R12 is connected to pin 1 of the three-terminal voltage regulator tube Q2, and pin 3 of the three-terminal voltage regulator tube Q2 is connected to the cathode of a light-emitting diode of the optocoupler controller U1. The anode of the diode is connected to the cathode of another light-emitting diode of the optocoupler controller U1, and the anode of the light-emitting diode is connected to the voltage positive output terminal of the DC-DC converter through a resistor; pin 1 of the three-terminal regulator Q2 and pin 3 are connected to an RC filter circuit, the two collectors of the two triodes of the optocoupler controller U1 are connected to the control terminal pins of the main controller IC 80, and grounded through a resistor, the two collectors of the optocoupler controller U1 The two emitters of the transistor are grounded.

The input current protection circuit 70 is shown in FIG. 2 , which includes a transformer 130 , a resistor R1 , a rectifying element 140 and a filter circuit 150 .

The transformer 130 senses the current of the primary side main loop of the transformer 50, which can be any transformer known to those skilled in the art. The utility model is selected as a coupling inductance L1, and the coupling inductance L1 is a magnetic ring wound with a coil. The magnetic ring is sleeved on the primary side main circuit of the transformer 50 .

Both ends of the resistor R1 are connected across the transformer 130 , one end is grounded, and the other end is connected to the input end of the rectifying element 140 (the anode of the rectifying diode D1 in the figure).

The filter circuit 150 includes: a resistor R2, a resistor R3, a resistor R4, and a capacitor C1, a capacitor C2, and a capacitor C3. One end of the resistor R2 is connected to the output end of the rectifying element 140 (the cathode of the rectifying diode D1 in the figure), the other end is connected to the ground through the resistor R3 and the resistor R4 in turn, one end of the capacitor C1, the capacitor C2 and the capacitor C3 are connected to the ground, and the other end is respectively connected to the The contact of the output terminal of resistor R2 and rectifier element 140, the contact of resistor R2 and resistor R3, the contact of resistor R3 and resistor R4 are connected, and the contact of resistor R3 and resistor R4 is connected with an input terminal (overcurrent) of main controller IC 80. Protection pin CS pin) connection.

The rectifying element 140 can be any rectifying element known to those skilled in the art, such as a rectifying diode, a rectifying triode, etc., and in consideration of cost, it is preferably a rectifying diode D1, and the input end of the rectifying element 140 is the rectifying diode The anode of D1, the output terminal of the rectifying element 140 is the cathode of the rectifying diode D1.

The main controller IC 80 is a multi-channel control controller with multiple input terminals and multiple output terminals, and the overcurrent protection pin CS pin of the main controller IC 80 is connected to the junction of the resistor R3 and the resistor R4 , the output terminal of the main controller IC 80 is connected with the control terminal of the switch 90, and controls the driving signal of the switch 90. The main controller IC 80 can choose UCC2895.

The switch 90 may be any controllable switch element with a control terminal known to those skilled in the art, such as a relay, MOSFET, IGBT, etc., preferably a MOSFET.

The input circuit 30 and the output circuit 40 are the input and output circuits known to those skilled in the art and can be used in DC-DC converters, respectively having a maximum rated current. When the current flowing through the circuit exceeds the maximum rated current, the utility model The newly provided input and/or output protection circuit can protect the entire DC-DC converter from overcurrent.

The transformer 50 is a commonly used transformer known to those skilled in the art, and is a basic component in a DC-DC converter, which is not particularly limited and will not be described here.

Introduce how the utility model carries out input end protection below. When a current flows in the main circuit of the primary side of the transformer 50, a coupling current is generated on the magnetic loop coil through the induction of the coupling inductor L1, and the current flows through the resistor R1, and a voltage drop is generated on the resistor R1. Since the main circuit on the primary side of the transformer 50 is controlled by the switch 90 periodically, the main circuit flows an alternating current, so the voltage on the resistor R1 is an alternating voltage. After rectification by the rectifier diode D1, the alternating current flowing through the rectifier diode D1 is converted into direct current. After the filtering effect of capacitor C1, capacitor C2 and capacitor C3, some interference noise is removed, so that the junction of resistor R3 and resistor R4 gets a clean voltage value, which is the main controller IC 80 overcurrent protection pin CS pin get the voltage value. The comparator inside the main controller IC 80 compares the voltage value received by the CS pin with a specific reference value that has been set inside the main controller IC 80. If the value is greater than the reference value, the main controller IC 80 is turned off The driving signal of the switch 90, until the voltage of the CS pin is lower than the reference voltage value of the main controller IC 80, the main controller IC 80 will start the driving signal of the switch 90 again. Therefore, when designing the circuit, it is first necessary to set the voltage value on the overcurrent protection pin CS pin of the main controller IC 80 when the current of the input terminal loop 30 is the maximum rated current value allowed to flow. Reference value for IC 80 internal current comparator. The input current protection circuit 70 detects the primary side loop of the transformer 50 by cycle-by-cycle current detection (synchronized with the switching cycle of the DC converter), so the input current protection circuit 70 has a sensitive response speed, and its circuit structure is simple at the same time. There are fewer devices, and the reliability is greatly improved.

Now, the operation of the input terminal protection circuit 70 to implement current protection will be described.

The first situation: when the load carried by the converter output exceeds its rated load, the output required power will be greater than the rated power of the converter. This power comes from the power transmission of the transformer 50, and the power at the input end of the converter increases. At this time, the current flowing through the primary side of the transformer 50 must increase (the input voltage of the converter will not actively increase). Through the coupling effect of the coupled inductor L1, the current on the coil of the coupled inductor L1 will also increase, and the voltage of the CS pin on the main controller IC 80 will also increase. When the voltage is greater than the internal current of the main controller IC 80 When the reference voltage of the inverter, the main controller IC 80 will turn off the driving signal of the converter switch 90, the converter input terminal loop 30 is disconnected and no current passes through, then the output power of the converter is reduced (due to the converter input terminal loop 30 The energy storage function of the capacitor, the output power will not drop to zero instantaneously), until the voltage of the CS pin of the main controller IC 80 is less than its reference value, the drive signal of the converter switch 90 will not be activated.

The second situation: the output power of the converter is within the rated output power range, but the input voltage of the converter is very low. At this time, the current flowing through the primary side of the transformer 50 will be very large. When the current is greater than the rated current of the primary side circuit of the transformer 50 , it is possible to burn the switch 90 and some other components such as fuses, etc., thereby damaging the converter itself. After the input terminal protection circuit 70 is added, the converter can be well protected, and the implementation of the protection principle is the same as the protection principle of the first case above, and will not be repeated here.

The third situation: when the converter output load suddenly increases from very small to very large (such as from light load to full load, but will not exceed the rated output current of the converter), the power at the input end of the converter will suddenly increase a lot, and the transformer The current of the primary side loop of 50 will also suddenly increase a lot, and a very large transient current peak will be generated on the primary side loop of the transformer 50 (sometimes this peak current will be several times of the primary side current), and they may burn out The switch 90 of the converter and/or some other components on the input circuit 30 of the converter, such as a fuse, a thermistor, etc., will damage the converter itself. But after adding the input terminal current protection circuit 70, the converter can be well protected, and the implementation of the protection principle is the same as the protection principle of the above-mentioned first case, which will not be repeated here.

When it is worth explaining, the utility model can also have multiple variants, such as the variable filter circuit in the current protection circuit at the input end, the variable type of the Hall current sensor for current sampling in the current protection circuit at the output end, and the variable signal amplifier circuit. The organizational structure of the converter can be changed, the way the signal is transmitted to the main controller IC and the controlled pins transmitted to the main controller IC can be changed. Of course, the main controller IC used by the converter can also be changed. However, these obvious modifications all fall within the protection scope of the present utility model.

Claims (4)

1. DC-DC converter, this DC-DC converter comprises input loop (30), output loop (40), transformer (50), output end current protective circuit (60), master controller IC (80) and switch (90); Input loop (30) and output loop (40) are connected respectively to the primary side and the primary side of transformer (50), output end current protective circuit (60) is connected between the input of the voltage output end in output loop (40) and master controller IC (80), the output of master controller IC (80) is connected with the control end of switch (90), and switch (90) is connected on transformer (50) the primary side major loop; It is characterized in that this DC-DC converter also comprises input current protecting circuit (70), input current protecting circuit (70) is connected between another input of the voltage output end in input loop (30) and master controller IC (80).

2. DC-DC converter according to claim 1 is characterized in that, described input current protecting circuit (70) comprises instrument transformer (130), rectifier cell (140), filter circuit (150) and resistance R 1;

The electric current of described instrument transformer (130) sensor transformer primary side major loop;

The two ends of described resistance R 1 are connected across the two ends of instrument transformer (130), resistance R 1 one end ground connection;

Described filter circuit (150) comprises resistance R 2, resistance R 3, resistance R 4, capacitor C 1, capacitor C 2 and capacitor C 3; The output of the described rectifier cells of resistance R 2 one terminations (140), the other end is successively by resistance R 3 and resistance R 4 ground connection, one end ground connection of capacitor C 1, capacitor C 2 and capacitor C 3, the other end is connected with contact, resistance R 3 and the contact of resistance R 4 of contact, resistance R 2 and the resistance R 3 of the resistance R 2 and the output of rectifier cell (140) respectively, and the contact of resistance R 3 and resistance R 4 links to each other with the end of coming in and going out of master controller IC (80);

The input of rectifier cell (140) is connected with resistance R 1 other end.

3. DC-DC converter according to claim 2 is characterized in that, described instrument transformer (130) is coupling inductance L1, and described coupling inductance L1 is the magnet ring that is wound with coil, and described magnet ring is enclosed within on transformer (50) the primary side major loop.

4. DC-DC converter according to claim 2, it is characterized in that, described rectifier cell (140) is rectifier diode D1, the input of described rectifier cell (140) is the anode of described rectifier diode D1, and the output of described rectifier cell (140) is the negative electrode of described rectifier diode D1.

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