A low power consumption power supply quick start circuit

Abstract

The present invention discloses a low-power power supply quick start circuit, comprising an AC input unit 100 and a DC output unit 107, wherein a rectifier unit 101 is connected in parallel to the AC output unit 100, wherein the rectifier unit 101 is connected to a peak absorption circuit 102, wherein the rectifier unit 101 is connected to a high-voltage start circuit 104, wherein the high-voltage start circuit 104 is connected to a rectifier filter unit 103, wherein the high-voltage start circuit 104 is connected to a PWM control unit 105, wherein the PWM control unit 105 is connected to the peak absorption circuit 102 via a transistor Q101, wherein the DC output unit 107 is connected to an output rectifier filter unit 106, wherein the DC output unit 107 is connected to the PWM control unit 105 via a feedback unit 108. The present invention has the advantages of being simple and reliable, having a high cost-effectiveness, and being able to easily achieve new design indicators.

Description

Technical Field

[0001] The invention relates to the technical field of fast start circuits, and in particular to a low power consumption power supply fast start circuit. Background Art

[0002] The new European ERP regulations require that the startup time of LED power supplies should be less than 500ms and the no-load loss should be less than 500mw. However, many power chips do not have a high-voltage startup function. If the startup resistor value from the VCC pin of the power chip to the high voltage of the rectifier output is simply reduced, the regulatory requirements for no-load loss will not be met, and the startup time will become very long. Therefore, it is necessary to add a high-voltage startup circuit to this type of chip to meet the startup time and no-load loss requirements.

[0003] Commonly used high-voltage startup chips, such as SP689 from Taiwan's Qingli Microelectronics, work on the principle that there is an electronic switch inside the chip that connects the high-voltage end after rectification and the VCC pin of the power chip and capacitor C4, and the switch is in a normally closed state. When we power on the power supply, the potential on C4 rises rapidly. When it rises to the startup threshold voltage of the power chip IC1, the power chip IC1 starts to work and outputs a PWM waveform through the drive pin (OUT pin); at this time, the detection end (sense pin) of the high-voltage startup chip IC2 detects that IC1 has a drive waveform and judges that IC1 is working normally. Then IC2 turns off the internal electronic switch, so that the high voltage electricity after the rectifier bridge no longer charges the electrolytic C4 through the resistor RHV, thereby reducing the no-load power consumption.

[0004] However, such dedicated chips are expensive and have a very low maximum allowable charging current. For example, the startup current of SP689 is only 2mA, while the startup current of many power chips is greater than 2mA. In many cases, the device may not be able to start normally. Figure 1 and Figure 2 shown.

[0005] Therefore, many simple discrete components have emerged to realize the circuit of this low-power startup function.

[0006] The first common one, such as Figure 3 :

[0007] The working principle of this circuit is to connect the high voltage HV+ after the rectifier and filter unit and the VCC pin of the power chip through an enhanced MOS. The high voltage HV+ is connected to the voltage regulator ZD50 through R23 / 24 / 25. Since the voltage regulator on ZD50 is 15V, which is greater than the driving threshold voltage of MOS (Q50), Q50 is turned on, and then the high voltage charges the electrolytic C37 through the resistor R20 / 21 / 22. After the potential of C37 quickly rises to the startup threshold voltage of the power chip, the power chip starts to work. , and the high-voltage DC power after rectification of the mains is adjusted to the low-voltage DC power we need through the transformer. The winding on the transformer that provides the driving voltage for the power chip is also coupled and rectified to obtain low-voltage DC power. The low-voltage DC power passes through the linear voltage stabilization circuit Q30 / R32 / ZD30 / D31 and outputs a stable 20V voltage to the source of the MOS tube Q50. At this time, the gate voltage is greater than the source voltage, and the enhanced NMOS tube Q50 is turned off, thereby achieving the purpose of quickly starting the power chip and reducing the no-load power consumption.

[0008] But the problem with this line is that even if Q50 is turned off to reduce the loss caused by R20 / 21 / 22, the dead loads R23 / 24 / 25 and ZD50 will continue to consume energy. Therefore, this line can effectively reduce the no-load loss, but basically cannot meet the stringent requirements of 500mw.

[0009] There is another common low-power fast-start circuit. For example, patent ZL201320883909.7 provides a high-voltage startup circuit composed of discrete components.

[0010] This circuit is that high voltage VH drives MOS tube V4 through resistor R5. After V4 is turned on, high voltage VH charges electrolytic C3 through resistor R7 / diode V5. When the potential of C3 reaches the startup threshold of the power chip, the chip starts to work and outputs a reference signal Vref. The reference signal drives transistor V1 after current limiting through R3. After transistor V1 is turned on, the gate potential of MOS tube V4 is pulled down, thereby turning off MOS tube V4, achieving the purpose of fast startup and reducing no-load power consumption.

[0011] But this circuit and Figure 3 As in the circuit shown, there is a component that consumes energy all the time. When transistor V1 is turned on, resistors R4 / R5 continue to consume energy, making it difficult to reduce the no-load power consumption to 500mW. Summary of the invention

[0012] The technical problem to be solved by the present invention is to provide a low-power power supply quick start circuit which is simple, reliable, cost-effective and can easily achieve new design indicators in view of the above problems.

[0013] In order to solve the above technical problems, the technical solution provided by the present invention is as follows: a low-power power supply fast start-up circuit, comprising an AC input unit 100 and a DC output unit 107, wherein a rectifier unit 101 is connected in parallel to the AC output unit 100, wherein the rectifier unit 101 is connected to a peak absorption circuit 102, wherein the peak absorption circuit 102 comprises a diode D1, a resistor R2 and a capacitor C3, wherein the resistor R2 and the capacitor C3 are connected in parallel and then connected in series with the diode D1, and are connected in parallel with the primary winding, wherein the rectifier unit 101 is connected to a high-voltage start-up circuit 104, wherein the high-voltage start-up circuit 104 comprises a MOS tube Q100, wherein the MOS tube Q100 is a depletion-type MOS tube, wherein the drain of the MOS tube Q100 is connected to the resistor R100, wherein a resistor R101 is provided between the source and the gate of the MOS tube Q100, and wherein the gate of the MOS tube Q100 is connected to the transistor Q102 through the resistor R102. The collector of the transistor Q102 is connected, a resistor R103 is connected between the base and the emitter of the transistor Q102, the base of the transistor Q102 is connected to the source of the MOS tube Q100 through the resistor R104 and the diode D101, the high-voltage startup circuit 104 is connected to the rectification and filtering unit 103, the rectification and filtering unit 103 includes a VCC auxiliary winding, a diode D2 and a capacitor C4, the VCC auxiliary winding is connected in series with the diode D2 and in parallel with the capacitor C4, the diode D2 is connected to the diode D101, the high-voltage startup circuit 104 is connected to the PWM control unit 105, the PWM control unit 105 is connected to the peak absorption circuit 102 through the transistor Q101, the DC output unit 107 is connected to the output rectification and filtering unit 106, the output rectification and filtering unit 106 includes a secondary winding, a diode D3 and a capacitor C5, the secondary winding is connected to the diode D3 The DC output unit 107 is connected in series and in parallel with the capacitor C5 . The DC output unit 107 is connected to the PWM control unit 105 via the feedback unit 108 .

[0014] The advantages of the present invention over the prior art are as follows: the low-power power supply quick start circuit replaces the enhancement-type MOS tube with a depletion-type MOS tube MOS tube Q100. The characteristic of the depletion-type MOS tube is that even if the gate is not driven by a driving voltage, its drain-source is always on, so that the resistance between the high voltage and the gate of the MOS tube can be omitted, and the dead load is eliminated, thereby eliminating the driving resistance that must be used for the enhancement-type MOS tube that will become a dead load. The isolation diode D101 can ensure that the power chip is started reliably, ensure a sufficiently fast starting speed, and ensure sufficiently low no-load power consumption.

[0015] As an improvement, a capacitor C1 is connected in parallel to the AC input unit 100 .

[0016] As an improvement, a capacitor C2 is connected in parallel to the rectifying unit 101 .

[0017] As an improvement, the transistor Q101 is grounded via a resistor R3. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 2 is a circuit diagram of an existing circuit 1.

[0019] Figure 2 It is the circuit diagram of existing circuit 2.

[0020] Figure 3 BEIJING, China; 1. FIG. 1 is a circuit diagram of existing circuit three.

[0021] Figure 4 This is the circuit design diagram of patent ZL201320883909.7.

[0022] Figure 5 The invention discloses a block diagram of a low-power-consumption power supply quick-start circuit.

[0023] Figure 6 It is a circuit diagram of a high-voltage starting circuit 104 of a low-power power supply quick starting circuit of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0025] In conjunction with the accompanying drawings, a low-power power supply quick start circuit includes an AC input unit 100 and a DC output unit 107. The AC output unit 100 is connected in parallel with a rectifier unit 101. The rectifier unit 101 is connected to a peak absorption circuit 102. The peak absorption circuit 102 includes a diode D1, a resistor R2 and a capacitor C3. The resistor R2 and the capacitor C3 are connected in parallel with the diode D1 in series and in parallel with the primary winding. The rectifier unit 101 is connected to a high-voltage start circuit 104. The high-voltage start circuit 104 includes a MOS tube Q100. The MOS tube Q100 adopts a depletion type MOS tube. The drain of the transistor Q100 is connected to the resistor R100, a resistor R101 is provided between the source and the gate of the MOS transistor Q100, the gate of the MOS transistor Q100 is connected to the collector of the triode Q102 through the resistor R102, a resistor R103 is connected between the base and the emitter of the triode Q102, the base of the triode Q102 is connected to the source of the MOS transistor Q100 through the resistor R104 and the diode D101, the high-voltage startup circuit 104 is connected to the rectification and filtering unit 103, the rectification and filtering unit 103 includes a VCC auxiliary winding, a diode D2 and a capacitor C4, the VC The C auxiliary winding is connected in series with the diode D2 and in parallel with the capacitor C4. The diode D2 is connected to the diode D101. The high-voltage starting circuit 104 is connected to the PWM control unit 105. The PWM control unit 105 is connected to the peak absorption circuit 102 through the transistor Q101. The DC output unit 107 is connected to the output rectification and filtering unit 106. The output rectification and filtering unit 106 includes a secondary winding, a diode D3 and a capacitor C5. The secondary winding is connected in series with the diode D3 and in parallel with the capacitor C5. The DC output unit 107 is connected to the PWM control unit 105 through the feedback unit 108.

[0026] The AC input unit 100 is connected in parallel with a capacitor C1 .

[0027] The rectifier unit 101 is connected in parallel with a capacitor C2 .

[0028] The transistor Q101 is grounded via a resistor R3.

[0029] Working principle of the present invention: When the AC input 100 is turned on, the rectification and filtering unit 101 outputs high-voltage direct current. This high-voltage direct current is connected to the drain of the depletion-type MOS transistor Q100 through the resistor R100. Since the depletion-type MOS transistor Q100 is always turned on, the high voltage is connected to the PWM control unit (i.e., the VCC pin of the power supply chip and the filter capacitor on the VCC pin) after being limited by the resistor R100. The startup current charges the VCC capacitor. When the voltage on the VCC filter capacitor reaches the startup voltage threshold of the power supply chip, the power supply chip starts to work. Subsequently, the voltage is induced in the VCC auxiliary winding and starts to supply power to the VCC pin of the power supply chip after passing through the rectification and filtering unit 103, and drives the transistor Q101 through the resistor R104, turning on R101 and R102, resulting in Vg < Vs. In this way, the depletion-type MOS transistor Q100 turns off after the VCC winding starts to supply power. At this time, R100 is disconnected and no longer affects the no-load loss. Therefore, this circuit can well meet the requirements of startup time and no-load loss. The function of D101 is to prevent Q101 from turning on immediately and Q100 from turning off immediately as soon as the power is applied. In this case, the startup voltage of the power supply chip has not yet reached the threshold voltage, which may cause startup failure. After adding D101, only when the power supply chip completes startup and the induced voltage is generated in the self-powered VCC winding does Q101 turn on and Q100 turn off, which can ensure the reliable startup of the power supply chip.

[0030] The present invention and its embodiments have been described. This description is not restrictive. What is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural modes and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A low power consumption power supply quick start circuit, comprising an AC input unit 100 and a DC output unit 107, characterized in that: The AC input unit 100 is connected in parallel with a rectifier unit 101, and the rectifier unit 101 is connected to a peak absorption circuit 102. The peak absorption circuit 102 includes a diode D1, a resistor R2 and a capacitor C3. The resistor R2 and the capacitor C3 are connected in parallel and connected in series with the diode D1, and are connected in parallel with the primary winding. The rectifier unit 101 is connected to a high-voltage startup circuit 104, and the high-voltage startup circuit 104 includes a MOS tube Q100. The MOS tube Q100 is a depletion-type MOS tube. The drain of the MOS tube Q100 is connected to the resistor R100. A resistor R101 is provided between the source and the gate of the MOS tube Q100. The gate of the MOS tube Q100 is connected to the collector of the transistor Q102 through the resistor R102. A resistor R103 is connected between the base and the emitter of the transistor Q102. The base of the transistor Q102 is connected to the MOS tube Q100 through the resistor R104 and the diode D101. 00, the high-voltage starting circuit 104 is connected to the rectifying and filtering unit 103, the rectifying and filtering unit 103 includes a VCC auxiliary winding, a diode D2 and a capacitor C4, the VCC auxiliary winding is connected in series with the diode D2 and in parallel with the capacitor C4, the diode D2 is connected to the diode D101, the high-voltage starting circuit 104 is connected to the PWM control unit 105, the PWM control unit 105 is connected to the peak absorption circuit 102 through the transistor Q101, the DC output unit 107 is connected to the output rectifying and filtering unit 106, the output rectifying and filtering unit 106 includes a secondary winding, a diode D3 and a capacitor C5, the secondary winding is connected in series with the diode D3 and in parallel with the capacitor C5, the DC output unit 107 is connected to the PWM control unit 105 through the feedback unit 108; the capacitor C1 is connected in parallel to the AC input unit 100, and the capacitor C2 is connected in parallel to the rectifying unit 101.

2. A low power consumption power supply quick start circuit according to claim 1, characterized in that: The transistor Q101 is grounded via a resistor R3.

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