CN201489092U - Power detectors and power supplies - Google Patents

Abstract

The utility model provides a power detector, the first end of first switch circuit and second end that include are coupled respectively to second switch circuit control end and earthing potential, first switch circuit control end receives bus voltage sampling signal, second switch circuit first end and second end are coupled respectively to second resistor second end and earthing potential, second switch circuit control end is coupled to first end of first resistor and the first end of second resistor, first resistor second end is coupled to mains voltage, optical coupler illuminator is coupled between first resistor second end and second resistor second end, optical coupler illuminator responds illuminator's the luminous and output detected signal, thereby detect input alternating current power supply fast and have the transient interruption or pull out the condition. The utility model also provides a power supply, it uses aforementioned power detector, can be fast when detecting alternating current power supply has the instantaneous break or pulls out, and control power supply closes its peripheral device's power according to the preface.

Description

Power detectors and power supplies

technical field

The utility model relates to a power detector and a power supply using the power detector, in particular to a power detector capable of quickly detecting whether the input AC power is momentarily broken or unplugged and the power detector using the power detector. of the power supply.

Background technique

An LCD TV is mainly composed of a LCD panel, a backlight module, an audio amplifier (such as a speaker), an audio-visual control module, a power supply, and a casing. Among them, the backlight light source of the backlight module currently uses cold cathode fluorescent lamps, and cold cathode fluorescent lamps generally use 24V DC voltage and then convert it to high-voltage AC voltage through an inverter to supply power; audio amplifiers, audio-visual control modules and overall system control generally use The 12V DC voltage is powered by internal voltage conversion; in addition, TVs usually have a standby state, and in the standby state, generally use 5V DC voltage and only supply power to the microcontroller (Micro Controller Unit, referred to as MCU), and the MCU receives power. When the power button on the remote control (or TV control panel) is pressed and the signal is sent, the MCU sends a signal to start the main power supply to establish the aforementioned 24V and 12V DC voltages for components such as cold cathode fluorescent lamps, audio amplifiers and audio-visual control modules, so as to start television. Therefore, the power supply of the TV generally needs to provide multiple sets of DC voltages such as 5V, 12V and 24V.

FIG. 1 is a circuit diagram of a conventional LCD TV power supply. Referring to Figure 1, the power supply 1 includes an ElectroMagnetic Interference (EMI) filter 11, a bridge rectifier 12, a Power Factor Corrector (PFC) 13, a main power converter 14 and a standby power supply. Converter 15. The power supply 1 receives AC power from the public grid, and its voltage VAC typically ranges from 90 to 264Vrms. EMI filter 11 includes X capacitor C1 and common mode choke coil L1, in order to suppress the electromagnetic noise from the public power grid to pass into the TV circuit through the AC power wire, and also prevent the electromagnetic noise generated by the TV circuit itself from polluting the public through the AC power wire. power grid.

The bridge rectifier 12 includes a bridge diode BD and an energy storage filter capacitor C2. The input AC supply voltage VAC is rectified by the bridge diode BD to become a pulsating DC voltage, and then filtered by the capacitor C2 to become a relatively stable DC voltage. However, the bridge rectifier 12 will cause distortion of the input current. Generally, PFC is added thereafter to improve the current distortion. Especially, electronic devices with power above 75W need to add PFC to meet the harmonic current specification. In this example, the PFC 13 adopts an active boost converter, which includes a PFC controller U1, a power switch M1, an inductor L2, a rectifier diode D1 and an energy storage filter capacitor C3. The PFC controller U1 controls the switching of the power switch M1. When the power switch M1 is turned on (ON), the input electric energy is stored in the inductor L2 and the energy stored in the capacitor C3 is supplied to the output; when the power switch M1 is turned off (OFF) , the input electric energy and the energy stored in the inductor L2 are supplied to the output, so the PFC 13 outputs a bus voltage VBUS with a typical value of 380-400V when it is working.

The main power converter 14 outputs at least one main power voltage according to the bus voltage VBUS, such as a main power voltage VM1 with a typical value of 24V and a main power voltage VM2 with a typical value of 12V. The main power converter 14 adopts a half-bridge resonant converter, which includes a main power controller U2, power switches M2 and M3, a resonant capacitor C4, a transformer T1, rectifier diodes D2-D5, and energy storage filter capacitors C5 and C6. The main power controller U2 controls the switching of the power switches M2 and M3 to change the bus voltage VBUS into a square wave AC voltage input transformer T1 primary winding Pri, and utilizes the resonant capacitor C4 and the leakage inductor of the primary winding Pri to provide resonance to make the power switch M2 and M3 have zero voltage/zero current switching to reduce switching loss. The secondary winding Sec of the transformer T1 adopts three taps to output two main power supply voltages. It cooperates with the rectifier diodes D2 and D3 and the energy storage filter capacitor C5 to output the main power supply voltage VM1 to supply power to the inverter, and cooperates with the rectifier diodes D4 and D5 and the storage filter capacitor C5. The filter capacitor C6 can output the main power supply voltage VM2 to supply the audio amplifier and the audio-visual control module.

The standby power converter 15 outputs a standby power voltage VSB with a typical value of 5V according to the bus voltage VBUS. The standby power converter 15 adopts a flyback converter, which includes a standby power controller U3, a power switch M4, a transformer T2, a rectifier diode D6, and an energy storage filter capacitor C7. The standby power controller U3 controls switching of the power switch M4 to adjust the time when the bus voltage VBUS is input to the primary winding Pri of the transformer T2. The secondary winding Sec of the transformer T2 cooperates with the rectifier diode D6 and the energy storage filter capacitor C7 to output the standby power supply voltage VSB to supply power to the MCU. The standby power converter 15 also uses the auxiliary winding Aux of the transformer T2 to cooperate with the rectifier diode D7 and the energy storage filter capacitor C8 to provide an internal power supply voltage VCC with a typical value of 16V. This internal power supply voltage VCC will be established after the input of the AC power supply. Power is supplied to the controllers U1-U3 and internal circuits such as the isolated transmission circuit 16 and the like.

The internal power supply voltage VCC outputs the internal power supply voltage VCC1 through the diode D8 to provide constant power to the standby power controller U3, so that the standby power converter 15 will work immediately after the AC power is input to output the standby power supply voltage VSB. Since the TV is not turned on at this time, there will be no picture output and the overall power consumption must comply with international energy-saving regulations. When the MCU receives the signal sent by pressing the power key of the remote controller, the MCU sends the power start signal PS_ON to control the power supply switch 17 to conduct, and the internal power supply voltage VCC outputs the internal power supply voltage VCC2 through the power supply switch 17 to supply power to the PFC controller U1 and the main power supply. The power controller U2 makes the PFC 13 and the main power converter 14 work to output the main power voltages VM1 and VM2 to start the TV. When the MCU receives the signal sent by pressing the power button of the remote control again, the MCU sends the power off signal PS_OFF to control the power supply switch 17 to disconnect, and the internal power supply voltage VCC can no longer output the internal power supply voltage VCC2 through the power supply switch 17, that is, the internal power supply The voltage VCC2 becomes zero at this time, so that the PFC controller U1 and the main power controller U2 are turned off, and only the standby power supply voltage VSB is left to supply power to the MCU, so the TV is in a standby state.

Since the power on signal PS_ON (or power off signal PS_OFF) is located on the high voltage side, the power on signal PS_ON1 (or power off signal PS_OFF1) corresponding to the power on signal PS_ON (or power off signal PS_OFF) must be generated on the low voltage side through the isolated transmission circuit 16 ), and then the power switch 17 is controlled to be turned on (or turned off) by the power on signal PS_ON1 (or power off signal PS_OFF1). In this example, the power switch 17 comprises a transistor switch Q3. The isolated transmission circuit 16 includes an optocoupler OC1, a transistor switch Q4, and a zener diode ZD1, and the optocoupler OC1 includes a light emitting diode PD1 and a phototransistor PT1, wherein the transistor switch Q4 responds to the power on signal PS_ON (or power off signal PS_OFF) Then, the phototransistor PT1 is turned on (or disconnected) in response to the light emitting diode PD1 (or not emitting light), so that the Zener diode ZD1 If there is a crash and the voltage difference between the two ends is the collapse voltage, the power-on signal PS_ON1 is output (or the power-off signal PS_OFF1 is output if there is no voltage difference between the two ends).

FIG. 2 is a sequence diagram of startup and shutdown of the power supply of the LCD TV shown in FIG. 1 . Please refer to Figure 2. After the AC power is input, when the user presses the power button on the remote control to start the TV, the MCU sends a power-on signal PS_ON at time t1, which controls the power supply switch 17 to turn on and output The internal power supply voltage VCC2 supplies power to the PFC controller U1 and the main power controller U2, thereby starting the PFC 13 and the main power converter 14. PFC 13 starts to work to convert the input pulsating DC voltage into bus voltage VBUS. When the bus voltage VBUS rises to a certain value, the main power converter 14 starts to work to convert the bus voltage VBUS to the main power supply voltages VM1 and VM2, and at the beginning When the main power supply voltages VM1 and VM2 are established, the MCU will start timing, so that after the main power supply voltages VM1 and VM2 stably provide 24V and 12V, the MCU starts to send peripheral device start signals. For example, at time t2, the MCU sends the logic circuit activation signal LVDS_ON to make the logic circuit in the LCD panel operate first. This logic circuit includes components such as the audio-visual control module, which starts to detect and receive external audio-visual signal sources; After the logic circuit of the panel operates for a period of time, the backlight modulation start signal BR_ON is sent at the time point t3; finally, the MCU sends the inverter start signal INV_ON at the time point t4 to light up the backlight source, so that the LCD TV displays the picture and works stably.

When the user wants to turn off the TV and presses the power button on the remote controller again, the MCU sends the power off signal PS_OFF according to the time point t5, which controls the power supply switch 17 to turn off and turns off the PFC 13 and the main power converter 14, and at the same time The MCU starts to send peripheral device shutdown signals. For example, at time t5, the inverter shutdown signal INV_OFF is sent to turn off the backlight, at time t6 the logic circuit shutdown signal LVDS_OFF is sent, and at time t7 the backlight modulation shutdown signal BR_ON is sent. At this time, the standby power supply voltage VSB is left to supply power to the MCU, and the TV returns to the standby state.

However, the establishment of the startup and shutdown sequence of the power supply 1 of the aforementioned LCD TV must be based on the premise that the standby power converter 15 provides the standby power supply voltage VSB to the MCU, so that the MCU can control the startup and shutdown sequence. When the input AC power supply is momentarily interrupted or unplugged, the standby power converter 15 will no longer be able to provide the standby power supply voltage VSB to the MCU. At this time, the MCU will lose control or fail to operate because the standby power supply voltage VSB begins to drop. There is no way to perform start-up and shutdown sequencing anymore.

Contents of the invention

The purpose of this utility model is to propose a power detector, which can quickly detect whether the input AC power has a momentary interruption or unplugging.

Another purpose of this utility model is to propose a power supply device that can quickly detect whether the input AC power has a momentary interruption or unplugging situation, and when the AC power supply is detected to have a momentary interruption or unplugging situation, control the power supply The controller sequentially turns off the power of its peripheral devices.

In order to achieve the above purpose, the utility model proposes a power detector, which includes a first switch circuit, a second switch circuit, a first resistor, a second resistor and an optical coupler. The first switch circuit has a first terminal, a second terminal and a control terminal, the second terminal of the first switch circuit is coupled to the ground potential, the control terminal of the first switch circuit receives the bus voltage sampling signal, and the first switch circuit responds to the bus voltage sampling signal The signal starts to disconnect when it is less than the set value. The second switch circuit has a first terminal, a second terminal and a control terminal, the second terminal of the second switch circuit is coupled to the ground potential, the control terminal of the second switch circuit is coupled to the first terminal of the first switch circuit, and the second switch circuit Opening in response to initial opening of the first switching circuit. The first resistor has a first terminal and a second terminal, the first terminal of the first resistor is coupled to the control terminal of the second switch circuit, and the second terminal of the first resistor is coupled to the power supply voltage. The second resistor has a first terminal and a second terminal, the first terminal of the second resistor is coupled to the control terminal of the second switch circuit, and the second terminal of the second resistor is coupled to the first terminal of the second switch circuit. The optocoupler includes a light-emitting device and a detection device, wherein the light-emitting device is coupled between the second end of the first resistor and the second end of the second resistor, the light-emitting device emits light in response to the conduction of the second switch circuit, and the detection device A detection signal is output in response to the light emission of the light emitting device.

The utility model further proposes a power supply, including an electromagnetic interference filter, a bridge rectifier, a main power converter, a standby power converter, and the aforementioned power detector of the utility model. The EMI filter receives the AC power and suppresses the interference in the AC power, and the bridge rectifier rectifies the AC power passing through the EMI filter into a bus voltage. The main power converter outputs at least one main power voltage according to the bus voltage. The standby power converter outputs a standby power voltage according to the bus voltage. The power detector outputs a detection signal in response to the bus voltage sampling signal being less than a set value.

In a preferred embodiment, the power supply further includes a power factor corrector, and the power factor corrector is coupled between the bridge rectifier and the bus voltage.

In a preferred implementation, the power supply further includes a power supply switch, the power supply switch is coupled between the power supply voltage and the second end of the first resistor, and the power supply switch responds to a The power start signal is turned on.

Compared with the prior art, the power detector described in the utility model can quickly detect whether the input AC power supply is interrupted or unplugged; the power supply device described in the utility model can quickly detect the input Whether there is a momentary interruption or unplugging of the AC power supply, and when the momentary interruption or unplugging of the AC power supply is detected, the power supply is controlled to turn off the power of its peripheral devices in sequence.

In order to make the above and other objects, features and advantages of the present invention more comprehensible, preferred embodiments will be described in detail below together with the attached drawings.

Description of drawings

Fig. 1 is a circuit diagram of an existing power supply for LCD TV;

FIG. 2 is a timing diagram for starting and shutting down the power supply of the LCD TV shown in FIG. 1;

3 is a circuit diagram of a power supply according to an embodiment of the present invention;

Fig. 4 is the equivalent circuit diagram of the power detector shown in Fig. 3;

FIG. 5 is a simulation diagram of transition time and transition voltage difference of the power detector shown in FIG. 3 .

Explanation of reference signs: 1, 3-power supply; 11, 31-electromagnetic interference (EMI) filter; 12, 32-bridge rectifier; 13, 33-power factor corrector (PFC); 14, 34-main Power converter; 15, 35-standby power converter; 16, 36-isolated transmission circuit; 17, 37-power switch; 38-power detector; BD-bridge diode; C1～C8-capacitor; D1～D8- Diode; L1-common mode choke coil; L2-inductor; M1~M4-power switch; OC1, OC2-optocoupler; PD1, PD2-light-emitting diode; PT1, PT2-phototransistor; Q1~Q4-transistor switch ;R1～R8-resistor; Rth-equivalent resistance; SW1, SW2-switch circuit; P11, P21-first end of switch circuit; P12, P22-second end of switch circuit; P13, P23-switch circuit control end; T1, T2-transformer; Pri-primary winding; Sec-secondary winding; Aux-auxiliary winding; U1-PFC controller; U2-main power controller; U3-standby power controller; ZD1, ZD2-Zener diode; VAC-AC power supply voltage; VBUS-bus voltage; VCC, VCC1, VCC2-internal power supply voltage; VM1, VM2-main power supply voltage; VSB-standby power supply voltage; Vth-equivalent voltage; Vbe1-base terminal to emitter terminal voltage difference ;I1, I2-current flowing through the resistor; Ib1, Ib2-base current; Ic1, Ic2-collector current; GND1, GND2-ground potential; ACD-detection signal; BR_ON-backlight modulation start signal; BR_OFF- Backlight modulation shutdown signal; INV_ON-inverter startup signal; V_OFF-inverter shutdown signal; LVDS_ON-logic circuit startup signal; LVDS_OFF-logic circuit shutdown signal; PS_ON, PS_ON1-power startup signal; PS_OFF, PS_OFF1-power shutdown Signal; P-common contact; t1～t7-time point.

Detailed ways

FIG. 3 is a circuit diagram of a power supply according to an embodiment of the present invention. Please refer to FIG. 3 , the power supply 3 includes an EMI filter 31, a bridge rectifier 32, a PFC 33, a main power converter 34, a standby power converter 35, an isolation transmission circuit 36, a power switch 37 and a power detector 38, wherein An embodiment of an EMI filter 31, a bridge rectifier 32, a PFC 33, a main power converter 34, a standby power converter 35, an isolation transmission circuit 36 and a power supply switch 37 is shown in FIG. This is not the limit. The power detector 38 includes a first switch circuit SW1, a second switch circuit SW2, a first resistor R1, a second resistor R2, and an optocoupler OC2. The first switch circuit SW1 has a first terminal P11, a second terminal P12 and a control terminal P13, the second switch circuit SW2 has a first terminal P21, a second terminal P22 and a control terminal P23, and the first resistor R1 has a first terminal and a control terminal P23. The second end, the second resistor R2 has a first end and a second end, and the optical coupler OC2 includes a light emitting device PD2 and a detecting device PT2.

The first terminal P11 of the first switch circuit SW1 is coupled to the control terminal P23 of the second switch circuit SW2, the second terminal P12 of the first switch circuit SW1 is coupled to the ground potential GND1, and the control terminal P13 of the first switch circuit SW1 receives the bus voltage sampling signal , the first switch circuit SW1 starts to turn off in response to the bus voltage sampling signal being less than a set value. The first terminal P21 of the second switch circuit SW2 is coupled to the second terminal of the second resistor R2, the second terminal P22 of the second switch circuit SW2 is coupled to the ground potential GND1, and the control terminal P23 of the second switch circuit SW2 is coupled to the first The first terminal P11 of the switch circuit SW1 and the second switch circuit SW2 are turned off in response to the initial turn-off of the first switch circuit SW1. Both the first end of the first resistor R1 and the first end of the second resistor R2 are coupled to the control end P23 of the second switch circuit SW2, the second end of the first resistor R1 is coupled to the power supply voltage VCC or VCC2, and the second resistor The second end of the switch R2 is coupled to the first end P21 of the second switch circuit SW2. The light emitting device PD2 is coupled between the second end of the first resistor R1 and the second end of the second resistor R2, the light emitting device PD2 emits light in response to the conduction of the second switch circuit SW2, and the detection device PT2 responds to the light emitting device PD2 luminescence to output a detection signal ACD.

In this embodiment, the bus voltage sampling signal is obtained by dividing and sampling the bus voltage VBUS through the resistors R5 and R6. The power supply detector 38 of the present utility model detects the AC power supply not directly by grabbing the AC supply voltage VAC, but indirectly grabbing the bus voltage VBUS provided by the PFC 33 after the power supply 3 starts the PFC 33, so that sampling of the AC supply voltage can be avoided The error is too large, and after the AC power is unplugged, due to the energy storage effect of the high-voltage capacitor at the output of the PFC 33 (capacitor C3 as shown in Figure 1), in addition to meeting the required output hold-up time after power-off (hold up time ) In addition, the falling slope of the bus voltage VBUS on the high-voltage capacitor is also relatively linear, so that more accurate results can be obtained during detection and sampling.

In this embodiment, the first switch circuit SW1 includes a Zener diode ZD2 , a third resistor R3 , a fourth resistor R4 , and a first transistor switch Q1 , and the first transistor switch Q1 is an NPN BJT transistor. The Zener diode ZD2 has an anode terminal and a cathode terminal, and the cathode terminal of the Zener diode ZD2 is coupled to the control terminal P13 of the first switch circuit SW1 to receive the bus voltage sampling signal. The third resistor R3 and the fourth resistor R4 are coupled in series between the anode terminal of the Zener diode ZD2 and the second terminal P12 of the first switch circuit SW1 (or the ground voltage GND1 ). The first transistor switch Q1 has a first terminal (or collector terminal), a second terminal (or emitter terminal) and a control terminal (or base terminal), which are respectively coupled to the first terminal P11 of the first switch circuit SW1, the first switch The second terminal P12 of the circuit SW1 and the third resistor R3 and the fourth resistor R4 share a joint point P. When the bus voltage sampling signal is less than the set value, the bus voltage sampling signal cannot make the Zener diode ZD2 work in the collapse zone. At this time, the Zener diode ZD2 is reverse-biased and only a very small reverse current passes through, and the very small reverse current passes through the third The operating voltage established by the resistor R3 and the fourth resistor R4 turns off the first transistor switch Q1. When the bus voltage sampling signal is greater than the set value, the bus voltage sampling signal makes the Zener diode ZD2 work in the breakdown zone, at this time the Zener diode ZD2 collapses and a large reverse current passes through, and the large reverse current passes through the third resistor R3 and the operating voltage established by the fourth resistor R4 to turn on the first transistor switch Q1 , wherein the third resistor R3 can limit the current to protect the first transistor switch Q1 . Therefore, when the AC power is removed, the bus voltage sampling signal starts to decrease, and when the bus voltage sampling signal is smaller than the set value, the first switch circuit SW1 starts to turn off.

In this embodiment, the second switch circuit SW2 includes a second transistor switch Q2, and the second transistor switch Q2 is a PNP bipolar junction transistor. The second transistor switch Q2 has a first terminal (or emitter terminal), a second terminal (or collector terminal) and a control terminal (or base terminal), respectively coupled to the first terminal P21 of the second switch circuit SW2, the second switch The second terminal P22 of the circuit SW2 and the control terminal P23 of the second switch circuit SW2. In addition, the second end of the second resistor R2 is coupled to the first end P21 of the second switch circuit SW2, and the second end of the first resistor R1 is coupled to the power supply voltage through the resistor R7, and the power supply voltage can be provided by an independent external power supply The power supply can also be powered by the internal power supply voltage VCC or VCC2 as in this embodiment. When powered by internal supply voltage VCC or VCC2, it is preferable to supply power from supply voltage VCC2 to save power, because the power detector 38 is not needed when the TV is turned off (or the power supply 3 receives the power off signal PS_OFF) Detect whether there is a momentary interruption or unplugging of the AC power supply.

In this embodiment, the light emitting device PD2 in the optical coupler OC2 is a light emitting diode, and the detection device PT2 is a phototransistor, but not limited thereto; for example, the detection device PT2 may also be a photodiode. When the first switch circuit SW1 is turned on, the second switch circuit SW2 is turned on, so that the light-emitting device PD2 emits light, and then the detection device PT2 is turned on in response to the light-emitting of the light-emitting device PD2. At this time, the output terminal of the power detector 38 is connected. to the ground potential GND2, so the detection signal ACD is a low voltage level signal (or logic 0 signal). When the AC power is unplugged, the bus voltage sampling signal starts to decrease and when it is less than the set value, the first switch circuit SW1 starts to turn off, and the second switch circuit SW2 cooperates with the first resistor R1, the second resistor R2 and the light The coupler OC2 can be disconnected very quickly, so that the light-emitting device PD2 no longer emits light, and then the detection device PT2 is disconnected in response to the non-light-emitting of the light-emitting device PD2. At this time, the output terminal of the power detector 38 is connected through the resistor R8. to the standby power supply voltage VSB, so the detection signal ACD is a high voltage level signal (or logic 1 signal). Therefore, the power detector 38 of the utility model can quickly detect that the input AC power has been cut off or unplugged and output a detection signal ACD, and use this detection signal ACD to directly notify the peripheral devices of the TV power supply 3 to shut down as shown in Figure 2 Shut down sequentially, or notify the MCU to control the TV power supply 3 to shut down the peripheral devices sequentially according to the shut-down sequence shown in FIG. 2 .

FIG. 4 is an equivalent circuit diagram of the power detector 38 shown in FIG. 3 . Referring to FIG. 4 , the bus voltage VBUS, the resistors R3 - R6 and the Zener diode ZD2 are simplified into a Thevenin equivalent circuit, which includes an equivalent voltage Vth and an equivalent resistance Rth. Equivalent voltage Vth=[VBUS×R6/(R5+R6)-VZD2]×R4/(R3+R4), equivalent resistance Rth=R3×R4/(R3+R4), where VZD2 is the cathode of Zener diode ZD2 The voltage difference between the pole and the anode, R3-R6 are the resistance values of the resistors R3-R6 respectively. If R3<<R4, the equivalent resistance Rth R3. Therefore, the base current Ib1=(Vth-Vbe1)/Rth flowing through the first transistor switch Q1, the collector current Ic1=hfe×Ib1=I1+I2+Ib2, wherein Vbe1 is the control terminal of the first transistor switch Q1 (or base terminal) to the second terminal (or emitter terminal), hfe is the current amplification factor of the first transistor switch Q1, I1 is the current flowing through the first resistor R1, and I2 is the current flowing through the second resistor R2 Current, Ib2 Base current for the second transistor switch Q2.

Therefore, by controlling the magnitude of the current Ib1, the magnitudes of the currents I1 and I2 can be controlled. When the current Ib1 is larger, the current Ic1 is larger, so that the voltage difference generated across the resistors R1 and R2 is higher, and thus the second transistor switch Q2 is turned on faster. Conversely, when the AC power supply is momentarily cut off or unplugged, the bus voltage VBUS starts to drop, so the equivalent voltage Vth starts to drop, which will cause the current Ib1 to drop, and through the resistance value of the first resistor R1 and the second resistor R2 Different, it can affect the magnitude of the current Ipd flowing through the light-emitting device PD2, for example, R2>>R1, when the current Ic1 slowly drops, the current Ipd will be greatly reduced due to the shunt relationship, and the current Ipt flowing through the detection device PT2 at this time Also because the current mapped under the fixed current transfer ratio (Current Transfer Ratio, CTR) ratio of the optocoupler OC2 is too low, the voltage on the resistor R8 drops rapidly. Therefore, the detection signal ACD can quickly transition from a logic 0 signal (indicating that the AC power supply has not been detected or unplugged) to a logic 1 signal (indicating that the AC power supply is detected to be disconnected or unplugged), that is, the power detector 38 of the present invention It can quickly detect the momentary interruption or unplugging of the input AC power.

FIG. 5 is a simulation diagram of the transition time and transition voltage difference of the power detector 38 shown in FIG. 3 . Please refer to Fig. 3 and Fig. 5 at the same time, the internal power supply voltage VCC2 in the design of the power supply detector 38 shown in Fig. 3 is 16V, the standby power supply voltage VSB is 5V, the resistance values of resistors R5 and R6 are 4.5MOhm and 91KOhm respectively, and resistor R3 The resistance values of R1 and R4 are 10KOhm and 51KOhm, the resistance values of resistors R1 and R2 are 10KOhm and 100KOhm respectively, the resistance values of resistors R7 and R8 are 2KOhm and 1KOhm respectively, the Zener diode ZD2 adopts 1N4734, and the first transistor switch Q1 adopts 2N3904 , the second transistor switch Q2 adopts 2N3906, and the optocoupler OC2 adopts SFH610A. Fig. 5 shows that when the bus voltage VBUS starts to drop linearly from 400V due to the momentary interruption or removal of the AC power supply, the output detection signal ACD of the power detector 3 changes from a logic 0 signal (indicating that the momentary interruption or removal of the AC power supply has not been detected) to The transition time for a logic 1 signal (representing that the AC power supply is detected to be cut off or unplugged) is 19.67ms and the transition voltage difference is 7V. The simulation results show that the power detector 38 of the utility model can quickly detect whether the input AC power is There is a momentary disconnection or unplugging situation.

In summary, the utility model utilizes the power detector 38 composed of the first switch circuit SW1, the second switch circuit SW2, the first resistor R1, the second resistor R2 and the optocoupler OC2 to quickly detect the input Whether there is a momentary interruption or unplugging of the AC power supply, and then can quickly and sequentially turn off the power of peripheral devices when the AC power supply is momentary or unplugging.

Although the utility model has been disclosed as above with preferred embodiments, it is not intended to limit the utility model, and any person of ordinary skill in the art may make some modifications and changes without departing from the spirit and scope of the utility model. Retouching, so the scope of protection of the present utility model should be defined by the scope of the appended patent application.

Claims (9)

1. Power supply detector is characterized in that it comprises:

One first on-off circuit, have one first end, one second end and a control end, described first on-off circuit, second end is coupled to an earthing potential, the described first on-off circuit control end receives a bus voltage sampled signal, and described first on-off circuit begins to disconnect less than a setting value for responding described bus voltage sampled signal;

One second switch circuit, have one first end, one second end and a control end, described second switch circuit second end is coupled to described earthing potential, described second switch circuit control end is coupled to described first on-off circuit, first end, described second switch circuit for respond described first on-off circuit begin disconnect;

One first resistor has one first end and one second end, and described first resistor, first end is coupled to described second switch circuit control end, and described first resistor, second end is coupled to a supply voltage;

One second resistor has one first end and one second end, and described second resistor, first end is coupled to described second switch circuit control end, and described second resistor, second end is coupled to described second switch circuit first end; And

One photo-coupler, comprise a light-emitting device and a pick-up unit, described light-emitting device is coupled between described first resistor, second end and described second resistor, second end, described light-emitting device is luminous for the conducting of responding described second switch circuit, and described pick-up unit is for responding the luminous detection signal of exporting of described light-emitting device.

2. Power supply detector as claimed in claim 1 is characterized in that, described first on-off circuit comprises:

One Zener diode has an anode tap and a cathode terminal, and described Zener diode cathode terminal is coupled to the described first on-off circuit control end;

One the 3rd resistor and one the 4th resistor, coupled in series is between described Zener diode anode tap and described first on-off circuit, second end; And

One the first transistor switch, have one first end, one second end and a control end, described the first transistor switch first end is coupled to described first on-off circuit, first end, described the first transistor switch second end is coupled to described first on-off circuit, second end, and described the first transistor switch control end is coupled to the common joint of described the 3rd resistor and described the 4th resistor.

3. Power supply detector as claimed in claim 2, it is characterized in that, described second switch circuit comprises a transistor seconds switch, described transistor seconds switch has one first end, one second end and a control end, described transistor seconds switch first end is coupled to described second switch circuit first end, described transistor seconds switch second end is coupled to described second switch circuit second end, and described transistor seconds switch control end is coupled to described second switch circuit control end.

4. Power supply detector as claimed in claim 3 is characterized in that, described the first transistor switch comprises a NPN two-carrier junction transistor, and described transistor seconds switch comprises a PNP two-carrier junction transistor.

5. Power supply detector as claimed in claim 1 is characterized in that described light-emitting device comprises a light emitting diode.

6. Power supply detector as claimed in claim 1 is characterized in that described pick-up unit comprises an optotransistor or photodiode.

7. power supply unit is characterized in that it comprises:

One Electromagnetic interference filter receives an AC power and suppresses interference in the described AC power;

One bridge rectifier will become a bus voltage by the described AC power rectification of described Electromagnetic interference filter;

One primary power converter is exported at least one main power voltage according to described bus voltage;

One standby power converter is exported a standby power voltage according to described bus voltage; And

One Power supply detector comprises:

One first on-off circuit, have one first end, one second end and a control end, described first on-off circuit, second end is coupled to an earthing potential, the described first on-off circuit control end receives the sampled signal of described bus voltage, and described first on-off circuit begins to disconnect less than a setting value for the sampled signal of responding described bus voltage;

One second switch circuit, have one first end, one second end and a control end, described second switch circuit second end is coupled to described earthing potential, described second switch circuit control end is coupled to described first on-off circuit, first end, described second switch circuit for respond described first on-off circuit begin disconnect;

One first resistor has one first end and one second end, and described first resistor, first end is coupled to described second switch circuit control end, and described first resistor, second end is coupled to a supply voltage;

One second resistor has one first end and one second end, and described second resistor, first end is coupled to described second switch circuit control end, and described second resistor, second end is coupled to described second switch circuit first end; And

One photo-coupler, comprise a light-emitting device and a pick-up unit, described light-emitting device is coupled between described first resistor, second end and described second resistor, second end, described light-emitting device is luminous for the conducting of responding described second switch circuit, and described pick-up unit is for responding the luminous detection signal of exporting of described light-emitting device.

8. power supply unit as claimed in claim 7 is characterized in that it also comprises a power factor corrector, and described power factor corrector is coupled between described bridge rectifier and the described bus voltage.

9. power supply unit as claimed in claim 7 is characterized in that it also comprises a power switch, and described power switch is coupled between described supply voltage and described first resistor, second end, and described power switch is for responding a power supply starting signal conducting.

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