KR101493063B1 - Voltage Protection Circuit for DC-DC Converter of Portable Device Application - Google Patents

Abstract

The present invention relates to a voltage protection circuit for a DC-DC converter for a small portable device, and more particularly, to a voltage protection circuit for a DC-DC converter for a small portable device, And a high voltage protection circuit for interrupting the operation of the DC-DC converter when an output voltage of the DC-DC converter is higher than a second reference voltage.
The low-voltage protection circuit can prevent malfunction of the circuit when a low-voltage input voltage is applied to the DC-DC converter. The high-voltage protection circuit cuts off the circuit when an excessive output voltage is generated in the DC- It is possible to prevent the breakdown of the device due to the breakdown.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage protection circuit for a DC-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage protection circuit for a DC-DC converter for a small portable device, and more particularly, to a low voltage protection circuit (UVLO) that can reduce malfunction of input voltage and output voltage in a DC- : Under Voltage Lock Out) and Over Voltage Protection (OVP).

With the expansion of facilities based on wireless Internet, the demand for small portable devices is increasing more and more research is being actively carried out to install more functions in one mobile device.

Generally, the power supply voltage required for a small portable device is supplied from a battery, and various operating voltages must be supplied from the battery to operate various functions of a small portable device. The power supply of a small portable device must be capable of outputting a constant voltage while lowering the power consumption of the battery, and a power management circuit is widely used for this purpose.

In recent years, power management integrated circuits (PMICs), in which the functions of the main power supply are made into a single chip, are becoming more important. The power management integrated circuit (PMIC) is an element that controls and manages the power of the power source according to an output load, and is generally formed as a one-chip including a switching element and a power conversion and control circuit DC-DC converters are widely used for power conversion and control.

FIG. 1 is a schematic block diagram showing the inside of a PMIC chip using a conventional DC-DC converter.

As shown in FIG. 1, a conventional PMIC includes at least one DC-DC converter, an ON / OFF control and interface, and a plurality of LDOs (Low Drop Out).

However, the input / output voltage of the DC-DC converter may fluctuate due to external impact or malfunction. That is, the DC-DC converter receives a voltage lower than a predetermined reference value or can output a voltage higher than a predetermined reference value. If such a low voltage or a high voltage is generated, the small portable device may fail or malfunction.

Therefore, it can be understood that the configuration of the voltage protection circuit that can improve the reliability and stability of the DC-DC converter used in the conventional small-sized portable equipment is essential.

The present invention provides a voltage protection circuit for preventing the malfunction of the input / output voltage of the DC-DC converter for a small portable device and protecting the circuit, in order to enhance stability and reliability of a power supply device for a small- The purpose.

According to an aspect of the present invention, there is provided a voltage protection circuit for a DC-DC converter for a small portable device, the DC-DC converter including a DC-DC converter, And a high voltage protection circuit for interrupting the operation of the DC-DC converter when the output voltage of the DC-DC converter is higher than the second reference voltage .

A first comparison circuit for comparing the first reference voltage with the input voltage and generating a first cutoff signal according to the comparison result to block the input voltage; And the like. The bias circuit may include a bias circuit for stabilizing the operation of the first comparator and a reference voltage generator for generating a reference voltage by itself.

The low-voltage protection circuit preferably has a hysteresis characteristic.

The high-voltage protection circuit may include a second comparator for comparing the output voltage with the second reference voltage and generating a second shut-off signal according to a comparison result, and a second comparator for supplying a constant current to the second comparator 2 bias circuit portion.

The high-voltage protection circuit may be configured to output the second shut-off signal to the controller for controlling the operation of the DC-DC converter to shut down the operation of the DC-DC converter. Here, the controller receives the output voltage of the DC-DC converter and outputs a PWM signal, and the PWM signal and the shutoff signal OVP OUT generated in the high voltage protection circuit are reset through an OR gate (gate) Terminal to control a switching element of the DC-DC converter.

The DC-DC converter, the controller, and the voltage protection circuit described above may be formed in one chip and made into a power management integrated circuit.

The voltage protection circuit of the DC-DC converter for a small portable device according to the present invention has the following advantageous effects.

The low voltage protection circuit (UVLO) according to the present invention can prevent a malfunction of the circuit when an input voltage of low voltage is applied to the DC-DC converter, and the high voltage protection circuit (OVP) When the output voltage is generated, the circuit is cut off and the breakdown of the device due to the high voltage can be prevented.

Accordingly, it is possible to increase the stability and reliability of the power supply device for a small portable apparatus including the DC-DC converter, and to prevent malfunction and malfunction of the small portable apparatus.

1 is an internal block diagram of a PMIC chip using a conventional DC-DC converter.
2 is a block diagram of a DC-DC converter having a voltage protection circuit according to an embodiment of the present invention;
3 is a block diagram of a low voltage protection circuit according to an embodiment of the present invention.
4 is a circuit diagram of a low-voltage protection circuit according to an embodiment of the present invention.
5 is a graph showing SPICE simulation results of a low-voltage protection circuit according to an embodiment of the present invention.
6 is a block diagram of a high voltage protection circuit according to an embodiment of the present invention;
FIG. 7A is an internal circuit diagram of a high voltage protection circuit according to an embodiment of the present invention, and FIG. 7B is a circuit diagram of a bias circuit of a high voltage protection circuit according to an embodiment of the present invention. FIG.
8 is a graph showing the results of a SPICE simulation of a high voltage protection circuit according to an embodiment of the present invention.
9 is a block diagram showing the relationship between the controller of the DC-DC converter and the high-voltage protection circuit according to the embodiment of the present invention.
10 and 11 are graphs showing the results of a SPICE simulation of a high voltage protection circuit according to an embodiment of the present invention.
12 and 13 are views showing layouts of a low-voltage protection circuit and a high-voltage protection circuit according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 2 shows a DC-DC converter having a voltage protection circuit according to an embodiment of the present invention. The DC-DC converter shown in Fig. 2 uses a step-down DC-DC converter (buck DC-DC converter) as an example.

As shown in FIG. 2, the DC-DC converter includes a controller and a voltage protection circuit. The controller is connected to a switching element of the DC-DC converter to control operation of the DC-DC converter. To sense the input / output voltage and determine the driving of the DC-DC converter.

The voltage protection circuit according to the embodiment of the present invention comprises a low voltage protection circuit (UVLO) and a high voltage protection circuit (OVP). The low voltage protection circuit is a circuit for interrupting the operation of the DC-DC converter when the input voltage Vin input to the DC-DC converter is lower than the reference voltage Vref1. The high voltage protection circuit is an output And blocks the operation of the DC-DC converter when the voltage Vo is higher than the reference voltage Vref2.

First, the low voltage protection circuit according to the present invention will be described. A low-voltage protection circuit is shown in Fig.

3, the low-voltage protection circuit includes a bias circuit for generating a reference voltage Vref1, a comparator for comparing the reference voltage Vref1 with the input voltage Vin of the DC-DC converter, (UVLO OUT) to block the transmission of the input voltage (Vin). That is, the blocking signal (UVLO OUT) output from the comparator is applied to the switching element (FET) of the DC-DC converter to interrupt the operation of the DC-DC converter.

4 shows a specific circuit diagram of the low-voltage protection circuit. As shown in Fig. 4, a bias circuit portion composed of a bias circuit portion and a reference voltage generating portion is disposed at the front end, and a comparator is disposed at the rear end. The bias circuit stage serves to stabilize the voltage and current in the circuit, stabilizes the operation of the comparator, and the reference voltage generation stage serves to generate a reference voltage in the circuit.

The operation of the low-voltage protection circuit is determined according to the result of comparison between the reference voltage Vref1 and the input voltage Vin. That is, when the input voltage Vin is lower than the reference voltage Vref1, the DC-DC converter is shut off to prevent malfunction. When the input voltage Vin is a proper voltage, the DC-DC converter outputs the voltage do.

The low-voltage protection circuit has a hysteresis characteristic and can set a voltage value at which the DC-DC converter operates.

The SPICE simulation was performed to confirm the driving of the low-voltage protection circuit, and the result is shown in FIG. In this embodiment, the SPICE simulation uses an XFAB 1 탆 CMOS process.

 As shown in FIG. 5, when the input voltage Vin is gradually increased to 4.8 V or more, the low-voltage protection circuit is turned on. When the input voltage Vin is decreased to 4.2 V or less, It turns off. In this interval, if the DC-DC converter is supplied with the power supply voltage, it can operate normally.

Next, the high voltage protection circuit according to the present invention will be described. 6 shows a high voltage protection circuit.

6, the high voltage protection circuit is composed of a comparator and a bias circuit. The comparator compares the output voltage Vdd of the DC-DC converter with the reference voltage Vref2, and outputs a shutoff signal OVP OUT ), And the bias circuit unit is a circuit that maintains a stable bias and supplies a constant current to the comparator.

In the above-described low voltage protection circuit, the reference voltage is generated in the protection circuit, but in the high voltage protection circuit, the reference voltage is separately applied from the outside of the protection circuit. In this case, since the input voltage is almost fixed in the case of the low-voltage protection circuit, the circuit terminal for generating the reference voltage can be integrated in the circuit, but the high-voltage protection circuit determines whether the circuit operates or not according to the output voltage. I can not.

FIG. 7 shows a specific circuit diagram of the high voltage protection circuit. Fig. 7A is an internal circuit diagram of the high voltage protection circuit, and Fig. 7B is a circuit diagram of the bias circuit section. 7A, INP is the (+) input terminal of the comparator and INN is the (-) input terminal of the comparator.

In order to prevent the output voltage of the DC-DC converter from becoming excessively high and to prevent the device from being destroyed, the high voltage protection circuit controls the DC-DC converter so as not to perform the switching operation when the output voltage becomes a predetermined value or more, do.

In order to confirm driving of the high voltage protection circuit, a SPICE simulation was performed in the same manner as the low voltage driving circuit described above, and the results are shown in FIG.

As shown in FIG. 8, when a triangular wave of 0 to 5 V is input as the voltage to be input to the high voltage protection circuit and the reference voltage Vref2 is 3.8 V, if the voltage higher than the reference voltage Vref2 is output, And the circuit is protected by interrupting the driving of the DC-DC converter.

The DC-DC converter includes a controller such as a PWM (Pulse Width Modulation) circuit, and a controller and a high voltage protection circuit are shown together in a block diagram in FIG.

9, the controller of the DC-DC converter is constituted by a transconductance amplifier gm, a voltage-current converter (VtoI), a PWM comparator, an RS latch, And outputs a PWM signal to control the switching element (FET of FIG. 2) of the DC-DC converter.

The shutoff signal (OVP OUT) generated by the high voltage protection circuit and the PWM signal of the controller are connected to a reset terminal of an RS latch through an OR gate (gate). That is, when the output voltage Vo of the DC-DC converter exceeds the reference voltage Vref2, the high voltage protection circuit generates and outputs the shutoff signal OVP OUT, and the shutoff signal OVP OUT is input to the OR gate The RS latch is reset, so that the switching element of the DC-DC converter is turned off. The operation of the DC-DC converter is interrupted.

In order to confirm the concrete operation of the high voltage protection circuit of the present invention as described above, SPICE simulation was performed, and the results are shown in FIG. 10 and FIG.

10, when the voltage higher than the reference voltage Vref2 is inputted to the high voltage protection circuit, it can be confirmed that the high voltage protection circuit operates and the operation of the OR gate by the shutoff signal OVP OUT can be confirmed.

Next, in Fig. 11, a change in the output value of the RS latch can be confirmed. Here, a certain clock signal is applied as a set signal of the RS latch. 11, the operation of the high voltage protection circuit, the operation of the OR gate, the set signal of the RS latch, and the output signal of the RS latch are shown in turn.

It can be seen from Fig. 11 that when the high voltage protection circuit is operated, the OR gate is operated and the RS latch is reset. As a result, the switching element of the DC-DC converter is turned off, and the operation of the DC-DC converter is interrupted, thereby protecting the circuit.

12 and 13 show layouts of the low-voltage protection circuit and the high-voltage protection circuit of the present invention. The undervoltage protection circuit has a size of 789 μm × 307 μm and the high voltage protection circuit has a size of 335 μm × 177 μm.

As described above, the low-voltage protection circuit according to the embodiment of the present invention is turned on when the input voltage is 4.8 V or more, and is turned off when the input voltage is lower than 4.2 V to prevent malfunction of the circuit when the low- can do. In addition, the high voltage protection circuit according to the embodiment of the present invention can prevent the device from breaking when the output voltage of 3.8 V or higher is generated. Therefore, the stability and reliability of the DC-DC converter for small-sized portable apparatuses can be improved.

Meanwhile, the voltage protection circuit, the DC-DC converter, and the controller for controlling the DC-DC converter according to the embodiment of the present invention may be formed as a single chip and may be formed as a power management integrated circuit. Such a power management integrated circuit can provide a stable and reliable voltage to a small portable device.

While the present invention has been described with reference to the preferred embodiments described above and the accompanying drawings, it is to be understood that the invention may be embodied in different forms without departing from the spirit or scope of the invention. Accordingly, the scope of the present invention is defined by the appended claims, and is not to be construed as limited to the specific embodiments described herein.

Claims (8)

As a voltage protection circuit for DC-DC converters for small portable devices,
A low-voltage protection circuit for blocking an operation of the DC-DC converter when an input voltage inputted to the DC-DC converter is lower than a first reference voltage, and a second bias circuit part for generating a first reference voltage;
And a high voltage protection circuit for interrupting the operation of the DC-DC converter when the output voltage from the DC-DC converter is higher than a second reference voltage applied from the outside,
Wherein the first bias circuit unit includes:
A bias circuit stage for stabilizing the operation of the low voltage protection circuit, and a reference voltage generation stage for generating the first reference voltage by itself.
The method according to claim 1,
The low voltage protection circuit
Further comprising a first comparator for comparing the first reference voltage with the input voltage and generating a first blocking signal according to a result of the comparison to block the input voltage.
delete The method of claim 2,
Wherein the low-voltage protection circuit has a hysteresis characteristic.
The method according to claim 1,
The high voltage protection circuit
A second comparator for comparing the output voltage with the second reference voltage and generating a second cutoff signal according to the comparison result,
And a second bias circuit for supplying a constant current to the second comparator.
The method of claim 5,
The high voltage protection circuit
And outputs the second blocking signal to the controller for controlling the operation of the DC-DC converter to interrupt the operation of the DC-DC converter.
The method of claim 6,
The controller receives the output voltage of the DC-DC converter and outputs a PWM signal. The PWM signal and the shutoff signal OVP OUT generated by the high voltage protection circuit are connected to the reset terminal of the RS latch through an OR gate And controls the switching element of the DC-DC converter.
DC-DC converters for small portable devices,
A controller for controlling the DC-DC converter;
A voltage protection circuit according to any one of claims 1 to 7,
Wherein the DC-DC converter, the controller, and the voltage protection circuit are formed in one chip.

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