CN201928187U - A high-voltage starting switch circuit and a switching power supply using the circuit - Google Patents

Abstract

The utility model relates to a high-voltage starting switch circuit and a switching power supply using the circuit. The high-voltage starting switch circuit is started by a high-voltage starting switch, and after starting, the starting switch can be turned off to avoid starting circuit loss. The switching power supply includes a transformer and a control circuit, characterized in that: the control circuit is coupled to a feedback unit provided at the output end of the transformer to generate a switch signal to adjust the pulse width of the transformer, and the control circuit includes the high-voltage starting switch circuit and a PWM controller. The power supply can better suppress the problem of starting circuit loss.

Description

A high-voltage starting switch circuit and a switching power supply using the circuit

technical field

The utility model relates to a high-voltage start switch circuit and a switch power supply using the circuit.

Background technique

Switching power converters, widely used in consumer electronics, generally come in two forms: alternating current to direct current (AC-DC) and direct current to direct current (DC-DC). The starters in traditional switching mode power converters are mostly resistors. After the power supply is powered on and started, there is a large power loss in the starting resistor, which has a great impact on the efficiency of the power supply in light load or standby state.

In order to solve the above problems, it is necessary to provide a new startup technology to complete the startup of the switching power supply and reduce the loss caused by the starter itself.

The traditional starting method mainly uses resistance starting, as shown in FIG. 1 , which depicts a power converter 10 based on the traditional starting technology. A control circuit 20 is coupled to a feedback unit 15 to generate a switching signal VSW, the switching signal adjusts the output signal VO of the power converter 10, and the feedback unit 15 is coupled to the output of the power converter 10 to generate A feedback signal VFB. Wherein the switch signal VSW changes according to the feedback signal VFB. A switch current IS of a transformer TR1 is converted into a voltage signal VS through the current pick-up resistor RS. The signal VS is received by the control circuit 20 to generate a switching signal VSW accordingly. The switch signal VSW is activated according to the internal UVLO circuit of the control circuit 20 . In the figure, the control circuit 20 includes a UVLO circuit. The UVLO circuit is coupled to VCC, and is used to generate an internal circuit power supply signal VBIAS according to the VCC pin voltage Vcc. VBAIS provides power supply for other internal circuits to start the circuit 20 to work normally. The pin VCC is coupled to the capacitor C _VCC for supplying power to the VCC pin. In addition, the pin VCC is coupled to the start-up resistor R _ST , and the start-up resistor R _ST is coupled to the input power V _IN for charging the capacitor C _VCC during initial power-on. During the charging period, when the potential on C _VCC rises to a preset potential Vccon, the UVLO circuit responds to the VCC pin to generate VBIAS, the circuit 20 starts to work completely, and the start-up period ends. From the above analysis, the start-up resistor R _ST still has current flowing after the end of the start-up cycle. However, the start-up resistor R _ST of a traditional switching power supply is generally about 1MΩ, and its maximum power consumption is: P _ST0 =380V ² /1MΩ= 144mW. Therefore, traditional starters have a great influence on light-load efficiency, and it is not easy to pass international energy efficiency regulations (such as US Energy Star).

Contents of the invention

The purpose of the utility model is to provide a high-voltage starting switch circuit, which can be applied to switching power supplies and can better suppress circuit loss.

The utility model provides a high-voltage starting switch circuit, which includes a switch signal input terminal, a starting current input terminal, a switch current input terminal, an undervoltage lock input terminal, a power supply input terminal and a current detection terminal, and is characterized in that it also includes: a power A tube, its gate is connected to the switch signal input terminal, its drain is connected to the switch current input terminal, and its source is connected to the current detection terminal; a high-voltage switch tube, its drain is connected to the switch current input terminal The drain of the power tube is connected, the gate is connected to the starting current input terminal, a cathode provided with a clamping regulator tube, the collector of the first transistor and the collector of a second transistor, and its source is connected to a first The second end of the resistor is connected to the first end of a second resistor; the anode provided with the clamping regulator tube is connected to the ground potential; the base of the first transistor is connected to the first end of a third resistor The base of the second transistor is connected to the second end of a capacitor and the second end of the second resistor, and its emitter is connected to the first end of the capacitor and the second end of the second transistor. The first end of a resistor is connected to the anode of a protection diode; the second end of the third resistor is connected to the undervoltage lockout input; the cathode of the protection diode is coupled to the power supply input end.

The above-mentioned high-voltage starting switch circuit is integrated in an integrated block.

Another object of the present invention is to provide a switching power supply using the above-mentioned high-voltage starting switching circuit, which can better suppress the loss of the starting circuit.

The switching power supply of the present utility model includes a transformer and a control circuit, and is characterized in that: the control circuit is coupled to a feedback unit located at the output end of the transformer, and the control circuit includes a high-voltage start-up switch circuit and a PWM controller ; The primary end of the transformer is connected to the starting current input end of the high-voltage starting circuit through a resistor, and the second end of the primary transformer is connected to the switching current input end of the high-voltage starting circuit; the PWM control The output terminal of the device is coupled to the high-voltage starting switch circuit.

The utility model adopts a high-voltage start-up switch circuit to realize the premise that the power-on start performance of the switch power supply remains unchanged, greatly reduces the loss of the start-up circuit after the start-up of the switch power supply is completed, and can be designed as an integrated circuit with low cost and good market value.

Description of drawings

Figure 1 is a power converter based on a traditional starting circuit.

Fig. 2 is a schematic diagram of the circuit connection of the utility model high-voltage starting switch circuit of the present invention.

Fig. 3 is a schematic block diagram of a power supply based on a high-voltage start-up switch circuit.

Description of main component symbols:

20, 300: control circuit

Q1, Q2, Q3: Transistors

TR1: Transformer

D1, D2: Diodes

Z1: regulator tube

M1, M2: Transistors

15, 104: feedback unit

R _S , R ₁ , R ₂ , R ₄ , R _ST : Resistors

C1, C2, C _VCC : Capacitors

1000: High voltage start switch circuit

2000: PWM controller

FB: feedback terminal

VCC: supply voltage input terminal

V _CC : supply voltage

SW: switch output

V _FB : feedback voltage

V _IN : Input voltage

V _O : output voltage

V _S : current sense voltage

I _S : switching current

I _VST : Input current

U _in : input voltage

V _SW : switch signal

UVLO: Undervoltage lockout input

VST: starting current input terminal

DRAIN: switch current input terminal.

Detailed ways

The utility model will be further described below in conjunction with the accompanying drawings and examples of implementation.

The utility model provides a high-voltage start-up switch circuit: it includes a switch signal input terminal V _SW , a start-up current input terminal VST, a switch current input terminal DRAIN, an undervoltage lockout input terminal UVLO, a power supply input terminal VCC, and a current detection terminal Vs. In that, it also includes: a power tube, the grid of which is connected to the input terminal of the switch signal, the drain of which is connected to the input terminal of the switch current, and the source of which is connected to the current detection terminal; a high-voltage switch tube, its drain is connected to the drain of the power tube, the gate is connected to the starting current input terminal, a cathode provided with a clamping regulator tube, the collector of the first transistor and the collector of a second transistor, Its source is connected to the second end of a first resistor and the first end of a second resistor; the anode provided with the clamping regulator tube is connected to the ground potential; the base of the first transistor is connected to the ground potential. The first end of a third resistor is connected, and its emitter is connected to the ground potential; the base of the second transistor is connected to the second end of a capacitor and the second end of the second resistor, and its emitter is connected to the second end of the second transistor. The first terminal of the capacitor, the first terminal of the first resistor and the anode of a protection diode are connected; the second terminal of the third resistor is connected to the input terminal of the undervoltage lockout; the cathode coupling of the protection diode connected to the power supply input described above.

Specifically, refer to FIG. 2. FIG. 2 is a schematic diagram of the circuit connection of the high-voltage start-up switch circuit of this implementation example. In the figure, the gate electrode of the high-voltage switch tube M1 is coupled to the start-up current input terminal VST and the voltage regulator tube Z1. The cathode, the collectors of transistors Q2 and Q3, the source electrode of the high-voltage switch tube M1 is coupled to the first end of the resistor R2 and the second end of the resistor R1, and the drain electrode of the high-voltage switch tube M1 is coupled to the switch current input terminal DRAIN and the drain electrode of the power tube M2; the gate electrode of the power tube M2 is coupled to the switch signal V _SW input terminal, and the source electrode of the power tube M2 is coupled to the current detection terminal Vs; the base electrode of the transistor Q2 is coupled to Connected to the second end of the capacitor C2 and the second end of the resistor R2, the emitter electrode of the transistor Q2 is coupled to the first end of the capacitor C2, the first end of the resistor R1 and the anode of the diode D2; the base of the transistor Q3 The electrodes are coupled to the second end of the resistor R4, the emitter electrode of the transistor Q3 is coupled to the ground potential; the anode of the voltage regulator tube Z1 is coupled to the ground potential; the cathode of the diode D2 is coupled to VCC; The first terminal of the resistor R4 is coupled to the input terminal UVLO of the undervoltage lockout.

It is worth mentioning that the high-voltage starting switch circuit described in the utility model can be integrated into an integrated block, which can greatly reduce the volume and cost of the circuit.

In order to allow those skilled in the art to better understand the utility model, we will further describe the working principle of the utility model in conjunction with the circuit below:

Please continue to refer to FIG. 2 , the high voltage start switch circuit 1000 includes a high voltage switch tube M1, a power tube M2, transistors Q2 and Q3, a diode D2, a voltage regulator tube Z1, resistors R1, R2 and R4, and a capacitor C2. At the beginning of power-on, VST is set at 26V, and at the same time UVLO=“0”, Q3 is disconnected, M1 is turned on to charge the VCC port to start the startup process, when the voltage of the VCC port rises to the preset voltage VCCon, UVLO=“ 1" Turn on the transistor Q3, disconnect the high-voltage switch tube M1, and the start-up ends. The detailed working process of the circuit is as follows:

During power-up, the VST port is set to 26V. R1, R2, Q2, and C1 form a constant current device, which performs constant current control on the channel current of M1.

During power-on and start-up: Initially, the potential of the VCC port is 0. UVLO = "0", the N-type tube Q3 is disconnected, the gate electrode of the high-voltage switch M1 is clamped at 26V, M1 is turned on, and the VCC port is constant through the constant current device (consisting of R1, R2, Q2, and C1) and D1. The current is charged to the preset value VCCon, the UVLO terminal is reversed to "1", Q3 is turned on, M1 is disconnected, and the start-up ends.

During normal operation: after startup, as long as the potential of VCC port is higher than VCCmin, UVLO=“1”. M1 is disconnected, there is no current, and only the VST port of the entire starter circuit has current I _VST flowing (I _VST ≤19uA), so the power consumption during the normal operation of the starter is estimated as: P _ST =V _IN *I _VST ≤380V *19uA=7.22mW (in which switching power supply input voltage V _IN ≤380V). Therefore, the maximum power consumption of the starting circuit of the power converter using this circuit is much smaller than that of the traditional power converter. (The maximum power consumption of the traditional power converter start-up circuit is 144mW)

What is to be explained here is that although the utility model is applied to a power converter by way of an example, the utility model itself has a wider application scope than the example. For example, Q2 and Q3 can use other transistors to achieve the same effect, and Z1 can be split into several electrical devices to achieve the same effect. Remove Q2, C2, R1, R2, R4 or change the network connection to achieve the same effect.

Please refer to Fig. 3, Fig. 3 is a power supply 100 based on a high-voltage starting switch circuit 1000, including a transformer and a control circuit 300, the control circuit 300 is coupled to a feedback unit located at the output end of the transformer, and the control circuit includes a A high-voltage start-up switch circuit 1000 and a PWM controller 2000; the first end of the transformer primary is connected to the start-up current input terminal (VST) of the high-voltage start-up circuit through a resistor R _ST , and the second end of the transformer primary is connected to The switching current input terminal (DRAIN) of the high-voltage starting circuit is connected; the output terminal of the PWM controller is coupled to the high-voltage starting switching circuit. In the figure, the resistor R _ST (R _ST greater than 20MΩ) is coupled between the port V _IN and VST to charge the VCC port of the circuit 300 through the resistor to start the power supply 100 . The maximum current of the port VST is V _INmax /R _ST =380V/20MΩ=19uA. A capacitor Cvcc is coupled between the port VCC and the ground for powering the control circuit 300 . A resistor Rs is coupled between the SENSE port and the ground potential to generate a voltage signal Vs according to the switch current Is. The control circuit 300 is coupled to a feedback unit 104 to generate a switch signal V _SW , and the switch signal adjusts the output signal V _O of the power converter. The feedback unit 104 is coupled to the output V _O of the power converter to generate a feedback signal V _FB . Wherein, the switch signal V _SW changes according to the feedback signal V _FB . A switching current I _S of a transformer TR1 is converted into a voltage signal V _S through a resistor R _S . The signal V _S is received by the control circuit 300 and a switching signal V _SW is generated accordingly.

The control circuit 300 starts the power supply 100 through the internal high voltage start switch circuit 1000 and the R _ST cascaded therewith. The high-voltage start-up switch circuit 1000 is coupled to the circuit 2000 and the VST port respectively, and charges and starts the capacitor Cvcc coupled to the VCC port through the VST port and the high-voltage start-up switch circuit 1000 in response to the UVLO signal. The high-voltage starting switch circuit 1000 is respectively coupled to the PWM controller 2000, the DRAIN port and the SENSE port. In response to the Vsw signal, the port DRAIN generates a switching current Is, and the switching current Is flows through the resistor Rs to generate a voltage signal Vs. The PWM controller 2000 is respectively coupled to the high voltage start switch circuit 1000, the FB port and the SENSE port, and generates a signal Vsw in response to the signals V _FB and Vs. The PWM controller 2000 is coupled to the VCC port, receives power from the VCC port, and generates a control signal UVLO to be input to the high-voltage start-up switch circuit 1000 .

Although the present invention is disclosed as above with preferred embodiments, it should not limit the present invention. Any person skilled in the art can make some modifications and substitutions without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present utility model should be defined by the appended patent scope.

Claims (4)

1. A high-voltage starting switch circuit, including a switching signal (V _SW ) input terminal, a starting current input terminal (VST), a switching current input terminal (DRAIN), an undervoltage lockout input terminal (UVLO), and a power supply input terminal (VCC) and the current sensing terminal (V _S ), characterized in that it also includes: A power tube, the grid of which is connected to the switch signal input terminal, the drain connected to the switch current input terminal, and the source connected to the current detection terminal; A high-voltage switching tube, the drain of which is connected to the drain of the power tube, the grid is connected to the starting current input terminal, the cathode of a clamping regulator tube, the collector of a first transistor and the collector of a second transistor connected; its source is connected to a second end of a first resistor and a first end of a second resistor; The anode of the embedded voltage regulator tube is connected to the ground potential; The base of the first transistor is connected to the first end of a third resistor, and its emitter is connected to the ground potential; The base of the second transistor is connected to the second end of a capacitor and the second end of the second resistor, and its emitter is connected to the first end of the capacitor, the first end of the first resistor and a protection diode. anode connection; The second terminal of the third resistor is connected to the input terminal of the undervoltage lockout; The cathode of the protection diode is coupled to the power input terminal. 2. The high voltage start switch circuit according to claim 1, characterized in that: said high voltage start switch circuit is integrated in an integrated block. 3. A power supply applying the high-voltage start-up switch circuit described in claim 1, comprising a transformer and a control circuit, characterized in that: the control circuit is coupled to a feedback unit located at the output end of the transformer, and the control circuit It includes a high-voltage starting switch circuit and a PWM controller; the first terminal of the transformer primary is connected to the starting current input terminal (VST) of the high-voltage starting circuit through a resistor, and the second terminal of the transformer primary is connected to the The switching current input terminal (DRAIN) of the high-voltage starting circuit is connected; the output terminal of the PWM controller is coupled to the high-voltage starting switching circuit. 4. The power supply using a high-voltage start-up switch circuit according to claim 3, wherein the high-voltage start-up switch circuit and the PWM controller are integrated into an integrated block.

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