TWI401883B - Switching power supply circuit - Google Patents

Description

Switching power supply circuit

The invention relates to the field of switching power supplies, and in particular to a switching power supply circuit for stably and reliably outputting a power supply voltage.

Most switching power supply architectures use dual-supply output common-mode signal voltages, such as a power supply with +5V output and a power supply with -5V output. However, the common-mode voltage of the dual-supply output is high and unstable when its output When the voltage value is high and unstable, it is easy to exceed the power of the electronic component and the integrated circuit in the load, resulting in a shortened life of the electronic component and the integrated circuit, and sometimes even damaging the electronic component.

Therefore, it is thought to replace the dual power supply with a single power supply. However, after a single power supply, the switching circuit needs to be improved accordingly.

In view of this, it is necessary to provide a single-supply switching power supply circuit that provides a stable and reliable power supply output.

A switching power supply circuit is electrically connected between the power supply and the output terminal. Electrically connected between the single power supply and the output terminal, including the control circuit, the logic circuit and the switch unit. The control circuit is configured to generate a control voltage signal after the switching power supply circuit is turned on . The logic circuit turns on the logic circuit in response to the control voltage signal and logically outputs the control voltage signal to the switching unit. The switch unit responds to the logic reverse control signal and enters an on or off state correspondingly, so that the single power supply voltage supplies power to the load through the output terminal or cuts off the single power supply to stop the power supply to the load through the output end.

Compared with the prior art, the logic circuit reversely outputs the control voltage signal to the switch unit and compares with the power supply voltage to turn on or off the switch unit, and controls the time when the switch unit is turned on or off, so that the power supply voltage passes through the output end to the load. Outputs a stable and reliable voltage.

10‧‧‧Switching Power System

20‧‧‧Power supply

30‧‧‧Switching power supply circuit

50‧‧‧output

31‧‧‧Control circuit

33‧‧‧Logical circuits

35‧‧‧Switch unit

331‧‧‧ Triode

351 332 352‧‧‧Electronic switch tube First filter voltage divider circuit Second filter voltage divider circuit

R1‧‧‧ first voltage divider resistor

R2‧‧‧Second voltage divider resistor

1 is a circuit block diagram of a switching power supply circuit according to an embodiment of the present invention.

2 is a specific circuit diagram of a switching power supply circuit according to an embodiment of the present invention.

The invention will be further described in detail below with reference to the accompanying drawings.

Referring to FIG. 1, the switching power supply system 10 includes a single power supply 20, a switching power supply circuit 30, and an output terminal 50. The switching power supply circuit 30 is located between the single power supply 20 and the output terminal 50 for regulating the voltage output from the single power supply 20 and outputting it to the load through the output terminal 50. The single power source 20 is positively grounded, and a voltage is input to the switching power supply circuit 30 through the negative electrode.

The switching power supply circuit 30 includes a control circuit 31, a logic circuit 33, and a switching unit 35.

The control circuit 31 is configured to generate a control voltage after the switching power supply circuit 30 is turned on. The logic circuit 33 turns on the logic circuit 33 in response to the control voltage signal and logically outputs the control voltage signal to the switching unit 35. The switch unit 35 responds to the logic reversed control signal and enters an on or off state correspondingly, so that the single power supply voltage supplies power to the load through the output terminal 50 or cuts off the single power supply 20 to stop the power supply to the load through the output terminal 50.

Referring to FIG. 2, the control circuit 31 is configured to generate a control voltage signal and input it to the logic circuit 33. In the present embodiment, the control circuit 31 is a square wave or rectangular wave generator that outputs a square wave signal whose positive and negative level voltage signals are constantly changing.

The logic circuit 33 includes a first voltage dividing resistor R1 and a transistor 331 (shown as an NPN transistor 331) that is grounded through the first voltage dividing resistor R1. The base of the transistor 331 is electrically connected to the control circuit 31, the collector is connected to the switching unit 35, and the emitter is grounded through the first voltage dividing resistor R1. The logic circuit 33 further includes a filter voltage dividing circuit electrically connected between the base and the emitter of the transistor 331 (as shown, the filter voltage dividing circuit includes capacitors and resistors connected in parallel with each other).

The switch unit 35 includes a second voltage dividing resistor R2 and an electronic switch tube 351 connected to the logic circuit 33 through the second voltage dividing resistor R2. In the present embodiment, the electronic switch tube 351 is an N-channel enhancement type MOS transistor Q1 (hereinafter referred to as an NMOS transistor Q1), and the source of the NMOS transistor Q1 is electrically connected to the power supply output terminal of the single power source 20, and the drain is electrically connected. The output terminal 50 of the switching power supply circuit is electrically connected to one end of the second voltage dividing resistor R2, and the other end of the second voltage dividing resistor R2 is electrically connected to the collector of the transistor 331. The switching unit 35 further includes a filter voltage dividing circuit electrically connected between the source and the gate of the N-channel enhancement type MOS (as shown, the filter voltage dividing circuit includes phases Capacitors and resistors in parallel with each other).

When the control circuit 31 outputs a negative high level voltage (e.g., -3V) to the base of the transistor 331, the transistor 331 is turned on, and the collector of the transistor 331 outputs a positive high level voltage signal (e.g., +3V). At this time, the gate of the NMOS transistor Q1 connected to the collector of the transistor 331 receives the positive high-level voltage signal and is at a high level, so that the NMOS transistor Q1 is turned on correspondingly, and the voltage of the single power source 20 passes through the switching unit. 35 provides a common mode voltage to output 50.

When the control circuit 31 outputs a positive high level signal, the transistor 331 is turned off, and the gate and the source of the NMOS transistor Q1 are electrically connected to the single power source 20 to obtain an equal voltage to turn off the NMOS transistor Q1 to make the output Terminal 50 has no voltage output.

It is to be understood that those skilled in the art can make various other changes and modifications in accordance with the technical concept of the present invention, and all such changes and modifications are intended to fall within the scope of the appended claims.

10‧‧‧Switching Power System

20‧‧‧Power supply

30‧‧‧Switching power supply circuit

50‧‧‧output

31‧‧‧Control circuit

33‧‧‧Logical circuits

35‧‧‧Switch unit

Claims (8)

A switching power supply circuit electrically connected between a single power supply and an output terminal, the improvement comprising: a control circuit, a logic circuit and a switch unit; wherein the control circuit is configured to generate a control voltage signal after the switching power supply circuit is turned on; The circuit includes an electronic switch tube, the first end of the electronic switch tube is connected to the control circuit, the second end is connected to the switch unit, and the third end is grounded; the electronic switch tube is turned on in response to the control voltage signal Or turning off, and correspondingly generating a high-level power signal at the second end when the electronic switch is turned on, and the voltage value of the high-level power signal and the voltage signal of the single power input When the difference between the voltage values is greater than or equal to the turn-on voltage value of the switch unit, the switch unit is turned on, so that the single power supply voltage supplies power to the load through the output end; when the electronic switch tube is turned off, The second end correspondingly generates a low-level power signal, and the difference between the voltage value of the low-level voltage signal and the voltage value of the single-power input voltage signal is less than the When the value of the ON voltage of the switching unit, the switching unit is turned off, truncating the single power supply through a load to the output terminal. The switching power supply circuit of claim 1, wherein the control circuit is a square wave or a rectangular wave generating circuit. The switching power supply circuit of claim 1, wherein the logic circuit further comprises a first voltage dividing resistor, the electronic switching tube is a triode, and the base of the triode is electrically connected to the control circuit, and the collector Connected to the switching unit, the emitter is grounded through the first voltage dividing resistor. The switching power supply circuit of claim 3, wherein the logic circuit further comprises a first filter voltage dividing circuit electrically connected between the base and the emitter of the triode, the first filter divided piezoelectric The circuit includes capacitors and resistors connected in parallel with each other. The switching power supply circuit of claim 3, wherein the switching unit comprises a second voltage dividing resistor and an electronic switching tube connected to the logic circuit through the second voltage dividing resistor. The switching power supply circuit of claim 5, wherein the electronic switching transistor is an N-channel enhancement type MOS transistor, and a source of the N-channel enhancement MOS transistor is electrically connected to a power supply output end of the power supply. The drain is electrically connected to the output end of the switching power supply, the gate is electrically connected to one end of the second voltage dividing resistor, and the other end of the second voltage dividing resistor is electrically connected to the collector of the triode. The switching power supply circuit of claim 6, wherein the switching circuit further comprises a second filter voltage dividing circuit electrically connected between the source and the gate of the N-channel enhancement type MOS transistor, The second filter voltage dividing circuit includes a capacitor and a resistor connected in parallel with each other. The switching power supply circuit of claim 1, wherein the single power supply is positively grounded, and a voltage is input to the switching power supply circuit through the negative electrode.