TWI411187B - Voltage control circuit having negative voltage restraining function - Google Patents

Description

Voltage control circuit with negative voltage suppression

The present invention relates to a voltage control circuit.

At present, the working voltage of some hardware (such as hard disk) on the host computer is usually provided by the voltage output terminal of a voltage control circuit on the computer motherboard. The voltage control circuit usually includes a voltage control chip (such as the model MAX8546). a DC buck control chip) and a plurality of electronic components (such as field effect transistors, inductors, capacitors, etc.) connected to the voltage control chip. However, when the computer is turned off, the low-pass field effect transistor connected to the voltage output terminal of the voltage control circuit is controlled to be turned on by the voltage control chip to short the low-pass field effect transistor to the ground, and then the low pass The field effect transistor will self-dicharge, causing a negative voltage at the voltage output, which may damage the hardware or cause a decrease in the life of the hardware.

In view of the above, it is necessary to provide a voltage control circuit that can effectively suppress the generation of a negative voltage.

A voltage control circuit with a negative voltage suppression function includes a voltage control chip, a voltage output terminal, a low pass field effect transistor connected between the voltage control chip and the voltage output terminal, and a negative voltage suppression unit. The negative voltage suppression unit includes a first electronic switch, a second electronic switch, a first resistor, a second resistor, a power source and a switch signal input terminal, the first end of the first electronic switch being connected to the voltage Controlling a low-pass driving pin of the chip, the second end of the first electronic switch is connected to the gate of the low-pass field effect transistor, and the control end of the first electronic switch is connected to the first end of the second electronic switch The second end of the second electronic switch is grounded, and the control end of the second electronic switch is connected to the switch signal input end, and the control end of the first electronic switch is further connected to the power source through the first resistor, the first electronic The control terminal of the switch is also grounded through the second resistor, and the second signal is turned on when the signal input end of the switch is low When the off is off and the first electronic switch is turned on, when the switch signal input terminal is at a high level, the second electronic switch is turned on and the first electronic switch is turned off.

Compared with the prior art, the voltage control circuit sets the negative voltage suppression unit between the voltage control chip and the low-pass field effect transistor, so that the voltage control circuit controls the first electronic switch to be turned on when the system is turned on. And controlling the first electronic switch to be turned off when the system is turned off, so that the low-pass field effect transistor does not generate a negative voltage when the system is turned off, thereby ensuring that the electronic device connected to the voltage output terminal is not blocked when the system is powered off. Negative voltage is damaged.

10‧‧‧Voltage control circuit

U‧‧‧Voltage Control Wafer

QL‧‧‧ low pass field effect transistor

QH‧‧‧High-pass field effect transistor

L‧‧‧Inductance

C1-C5‧‧‧ capacitor

R, R1, R2‧‧‧ resistance

Vcc‧‧‧ first DC power supply

Vdd‧‧‧second DC power supply

Vout‧‧‧voltage output

12‧‧‧Negative voltage suppression unit

Q1‧‧‧First field effect transistor

Q2‧‧‧Second field effect transistor

PWR_ON‧‧‧ switch signal input

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a circuit diagram of a preferred embodiment of a voltage control circuit having a negative voltage suppression function of the present invention.

Referring to FIG. 1, a preferred embodiment of the voltage control circuit 10 with negative voltage suppression function of the present invention includes a voltage control chip U, a low pass field effect transistor QL, a high pass field effect transistor QH, an inductor L, Five capacitors C1-C5, a resistor R, a first DC power source Vcc (such as 12V), a second DC power source Vdd (such as 24V), a negative voltage suppression unit 12 and a voltage output terminal Vout. In this embodiment, the voltage control chip U is a DC step-down control chip of the MAX8546. Here, only a part of the circuit relationship between the voltage control chip U and the voltage output terminal Vout is shown, and only the figure is shown in the figure. Three pins on the voltage control chip U (high-pass drive pin DH, output pin LX, low-pass drive pin DL), and other parts are conventional techniques, and therefore will not be described in detail.

The negative voltage suppression unit 12 includes two resistors R1 and R2, a first field effect transistor Q1, a second field effect transistor Q2, and a switch signal input terminal PWR_ON. In this embodiment, the first and second field effect transistors Q1 and Q2 are all NMOS type field effect transistors. In other embodiments, other types of electronic switches, such as PMOS type field effect transistors, may be selected as needed. .

The high-pass driving pin DH of the voltage control chip U is connected to the gate of the high-pass field effect transistor QH, and the drain of the high-pass field effect transistor QH is grounded through the two capacitors C1 and C2, respectively, the high-pass field effect transistor The source of QH is connected to the output pin LX of the voltage control chip U. The output pin LX of the voltage control chip U is connected to the direct current through the inductor L The source Vcc and the voltage output terminal Vout are sequentially grounded through the resistor R and the capacitor C3. The output pin LX is grounded through the two capacitors C4 and C5, respectively.

The low pass drive pin DL of the voltage control chip U is connected to the drain of the first field effect transistor Q1, and the source of the first field effect transistor Q1 is connected to the gate of the low pass field effect transistor QL. The drain of the low pass field effect transistor QL is connected to the output pin LX of the voltage control transistor U, and the source of the low pass field effect transistor QL is grounded. The gate of the first field effect transistor Q1 is connected to the drain of the second field effect transistor Q2, is connected to the second power source Vdd through the resistor R1, and is also grounded through the resistor R2. The source of the second field effect transistor Q2 is grounded, and the gate of the second field effect transistor Q2 is connected to the switch signal input terminal PWR_ON.

For ease of understanding of the present invention, an example will be given to illustrate the operation of the present invention, for example, when the voltage control circuit 10 is provided on a computer motherboard (not shown) for providing a hard disk (not shown). In the voltage control circuit of the voltage, the voltage control chip U will receive the PWM (Pulse-Width Modulation) signal provided by other circuits (not shown) on the computer motherboard, and pass through the voltage output terminal. Vout outputs the corresponding voltage to the hard disk. In other embodiments, the hard disk may also be other types of electronic devices.

During operation, after the computer is turned on, the switch signal input terminal PWR_ON will receive a low-level power-on signal to the second field-effect transistor Q2, and the second field-effect transistor Q2 will be turned off. The effect transistor Q1 will be turned on (corresponding to providing a length of wire between the low-pass driving pin DL and the low-pass field effect transistor QL), and the low-pass driving pin DL gives a normal output driving signal to the low-pass field. The effect transistor QL, the voltage output terminal Vout gives the normal output voltage to the hard disk.

When the computer is turned off, the switch signal input terminal PWR_ON will receive a high level shutdown signal to the second field effect transistor Q2, and the second field effect transistor Q2 will be turned on, the first field effect electric The crystal Q1 will be turned off (corresponding to disconnecting the channel between the low-pass driving pin DL and the low-pass field effect transistor QL), and the low-pass driving pin DL will not control the low-pass field effect transistor QL. Turning on, in turn, does not cause the low pass field effect transistor QL to generate a negative voltage to damage the hard disk.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. However, the above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art of the present invention should be included in the following claims. Inside.

10‧‧‧Voltage control circuit

U‧‧‧Voltage Control Wafer

QL‧‧‧ low pass field effect transistor

QH‧‧‧High-pass field effect transistor

L‧‧‧Inductance

C1-C5‧‧‧ capacitor

R, R1, R2‧‧‧ resistance

Vcc‧‧‧ first DC power supply

Vdd‧‧‧second DC power supply

Vout‧‧‧voltage output

12‧‧‧Negative voltage suppression unit

Q1‧‧‧First field effect transistor

Q2‧‧‧Second field effect transistor

PWR_ON‧‧‧ switch signal input

Claims (4)

A voltage control circuit with a negative voltage suppression function includes a voltage control chip, a voltage output terminal, and a low-pass field effect transistor connected between the voltage control chip and the voltage output terminal, and the improvement is: the voltage control The circuit further includes a negative voltage suppression unit including a first electronic switch, a second electronic switch, a first resistor, a second resistor, a power source, and a switch signal input terminal, the first The first end of the electronic switch is connected to the low-pass driving pin of the voltage control chip, and the second end of the first electronic switch is connected to the gate of the low-pass field effect transistor, and the control end of the first electronic switch is connected To the first end of the second electronic switch, the second end of the second electronic switch is grounded, and the control end of the second electronic switch is connected to the switch signal input end, and the control end of the first electronic switch further transmits the first a resistor is connected to the power source, and the control end of the first electronic switch is further grounded through the second resistor. When the switch signal input terminal is at a low level, the second electronic switch is turned off. An electronic switch is turned on when the input switch signal is high, the second electronic switch is turned on and the first electronic switch is turned off. The voltage control circuit with a negative voltage suppression function as described in claim 1, wherein the switch signal input end receives a computer switch signal, and the switch signal is low when the computer is turned on, the computer The power on/off signal is high when the power is turned off. A voltage control circuit having a negative voltage suppression function as described in claim 2, wherein the voltage output terminal is used to supply a voltage to a hard disk. The voltage control circuit with a negative voltage suppression function according to the first aspect of the patent application, wherein the first electronic switch and the second electronic switch are both NMOS type field effect transistors, the first end, the second end, and the control end Corresponding to the drain, source and gate respectively.