CN-119696349-B - Self-powered circuit of switching power supply and switching power supply

CN119696349BCN 119696349 BCN119696349 BCN 119696349BCN-119696349-B

Abstract

The invention provides a self-powered circuit of a switching power supply and the switching power supply, and the self-powered circuit comprises a first linear voltage stabilizing circuit, a second linear voltage stabilizing circuit, an adjusting circuit and a first charging current, wherein the first linear voltage stabilizing circuit is connected between a public connecting end of a main power tube and an auxiliary power tube and a power supply capacitor, the second linear voltage stabilizing circuit is connected with the second linear circuit in parallel, the adjusting circuit is connected with the second linear voltage stabilizing circuit, when the second linear voltage stabilizing circuit is started, an adjusting voltage is generated to adjust the first charging current flowing through the second linear voltage stabilizing circuit, after the switching power supply is started, the first linear voltage stabilizing circuit is started, the power supply capacitor is charged, and when a PWM signal generated by a control chip of the switching power supply is effective, the second linear voltage stabilizing circuit is controlled to be started. The invention can save power supply loss and optimize system EMI.

Inventors

GONG CHANGWEI
YANG YANG
XU XIANGYONG

Assignees

杰华特微电子股份有限公司

Dates

Publication Date: 20260512
Application Date: 20240801

Claims (14)

1. The self-powered circuit of the switching power supply comprises an inductor, a main power tube and an auxiliary power tube, wherein the inductor is connected with a first end of the main power tube, the auxiliary power tube is connected between a second end of the main power tube and a ground end, A power supply capacitor for generating a power supply voltage of a control chip of the switching power supply; The first linear voltage stabilizing circuit is connected between the common connecting end of the main power tube and the auxiliary power tube and the power supply capacitor; The second linear voltage stabilizing circuit is connected with the first linear voltage stabilizing circuit in parallel; The adjusting circuit is connected with the second linear voltage stabilizing circuit, and when the second linear voltage stabilizing circuit is turned on, the first charging current flowing through the second linear voltage stabilizing circuit is adjusted so that the voltage change rate of a first node between the main power tube and the inductor reaches a preset change rate; and when the PWM signal generated by the control chip of the switching power supply is effective, the second linear voltage stabilizing circuit is turned on, and the power supply capacitor is charged.
2. The self-powered circuit as recited in claim 1, wherein the first linear voltage regulator circuit is turned off when the supply voltage reaches a first threshold.
3. The self-powered circuit as recited in claim 1, wherein the adjustment circuit adjusts the first charging current to a reference current when the second linear voltage regulator circuit is on such that a rate of change of voltage at a first node between the main power tube and the inductor reaches a predetermined rate of change.
4. The self-powered circuit as recited in claim 1, wherein the adjustment circuit includes a first resistor coupled in a charging path between the second linear voltage regulator circuit and the supply capacitor, the magnitude of the first charging current being set by setting the magnitude of the first resistor.
5. The self-powered circuit as recited in claim 4, wherein the regulation circuit further comprises a sampling circuit and a first operational amplifier, the sampling circuit sampling the voltage of the first resistor to obtain a voltage sampling signal when the second linear voltage stabilizing circuit is on; the first operational amplifier carries out operational amplification on the voltage sampling signal and a first reference voltage to obtain an adjusting voltage, and the adjusting voltage controls the magnitude of the first charging current.
6. The self-powered circuit as recited in claim 5, wherein the sampling circuit is configured to sample the voltage at the power supply terminal to obtain a first sampled signal when the second linear voltage regulator circuit is on, When the second linear voltage stabilizing circuit is turned off, the voltage of the power supply end is sampled to obtain a second sampling signal, Subtracting the first sampling signal and the second sampling signal to obtain a voltage sampling signal representing the first resistance voltage; the power supply end is a public connection end of the second linear voltage stabilizing circuit and the first resistor.
7. The self-powered circuit as recited in claim 5, wherein the first resistor and the supply capacitor are integrated outside a control chip and the first linear voltage regulator circuit, the second linear voltage regulator circuit, the main power tube and the auxiliary power tube are integrated inside the control chip.
8. The self-powered circuit as recited in claim 1, wherein the adjustment circuit includes a rate-of-change detection circuit for detecting a rate of change of the first node voltage to obtain a rate-of-change detection signal, and adjusting the first charging current based on the rate-of-change detection signal.
9. The self-powered circuit as recited in claim 8, wherein the regulation circuit further comprises a sample-and-hold circuit and a second op-amp, the sample-and-hold circuit sampling the rate-of-change detection signal when the second linear voltage regulator circuit is on; And the second operational amplifier carries out operational amplification on the change rate detection signal obtained by the sampling and holding circuit and a second reference voltage to obtain an adjusting voltage, and the adjusting voltage controls the magnitude of the first charging current.
10. The self-powered circuit as recited in claim 1, further comprising a clamping circuit coupled to the high potential terminal of the supply capacitor for clamping the supply voltage at a predetermined value when the supply voltage is greater than the predetermined value.
11. The self-powered circuit as recited in claim 1, wherein the second linear voltage regulator circuit is turned off and the auxiliary power transistor is turned on when an on time of the second linear voltage regulator circuit reaches a preset time.
12. The self-powered circuit as recited in claim 1, wherein the second linear voltage regulator circuit is turned off and the auxiliary power tube is turned on when a voltage at a first node between the main power tube and the inductor drops to a predetermined voltage.
13. The self-powered circuit as recited in claim 1, wherein the power transistor is a depletion transistor.
14. A switching power supply comprises a main power tube and an inductor which are connected, and is characterized by further comprising a self-powered circuit as claimed in any one of claims 1-13, and the self-powered circuit is used for generating the supply voltage of a control chip of the switching power supply.

Description

Self-powered circuit of switching power supply and switching power supply Technical Field The invention relates to the field of power electronics, in particular to a self-powered circuit of a switching power supply and the switching power supply. Background By adopting a normal on power device, the self-starting and self-power supply can be realized conveniently, an extra resistor starting or high-voltage starting circuit can be omitted from a self-starting function, and an auxiliary winding power supply can be omitted from a self-power supply function. As shown in fig. 1, a self-powered circuit of a switching power supply in the prior art is shown as an example of a flyback converter, the self-powered circuit includes a main power tube Q1 and an auxiliary power tube Q2 connected in series, a first linear adjusting circuit (LDO 1) is connected between a common connection end and a power supply capacitor C0, a power supply voltage VDD is generated on the power supply capacitor C0, the power supply voltage VDD is used for supplying power to a control chip of the switching power supply, the power supply voltage VDD obtains a voltage VCC through the LDO (linear adjusting circuit) and is used for supplying power to a driving circuit 01 of the auxiliary power tube Q2, and the driving circuit 01 receives a PWM driving signal to generate a driving signal DRV for controlling on-off of the auxiliary power tube Q2. As shown in FIG. 2, during the on period (t 1-t 2) of the power tube Q1 and the auxiliary power tube Q2, the exciting inductance of the flyback converter stores energy, the inductance current I_Lm rises, the voltage Vsw at SW and the voltage drop Vds_Q2 at two ends of the auxiliary power tube Q2 are low, the control chip supplies power by the supply voltage VDD, and the VDD voltage drops. During the turn-off period (t 2-t 3) of the power tube Q1 and the auxiliary power tube Q2, exciting inductance current supplies power to the output, inductance current I_Lm drops, voltage Vsw at SW is clamped to vin+ Nps x Vo, wherein Vin is direct current input voltage of the flyback converter, vo is output voltage, nps is primary-secondary side turn ratio Nps =Np/Ns. of the transformer, the power tube Q1 works in a linear region at the moment, C0 is charged in a capacitor, voltage drop of the power tube Q1 has Vds_Q1=V SW - (-vgs_th), and vgs_th is threshold voltage of a D-Mode power device. Since the voltage at SW is clamped, the loss of the power transistor Q1 is relatively large, loss p=vds_q1×ivdd, where Ivdd is the average current consumed by the chip. When the power tube Q1 and the auxiliary power tube Q2 are turned off, the supply voltage VDD is derived from the voltage Vsw at SW, where Vsw is a high voltage, and at this time, the power tube Q1 works in a linear region, similar to a high voltage LDO, which causes large power loss and low system efficiency. In addition, when the auxiliary power tube Q2 is turned on, if the switching speed is not controlled, a large electromagnetic interference (EMI) may be caused. Disclosure of Invention The invention aims to provide a high-efficiency self-powered circuit of a switching power supply and the switching power supply, which are used for solving the problems of high power supply loss and low system efficiency in the prior art and optimizing the system EMI. The invention also provides a self-powered circuit of the switching power supply, the switching power supply comprises an inductor, a main power tube and an auxiliary power tube, the inductor is connected with the first end of the main power tube, the auxiliary power tube is connected between the second end of the main power tube and the ground end, comprising, A power supply capacitor for generating a power supply voltage of a control chip of the switching power supply; The first linear voltage stabilizing circuit is connected between the common connecting end of the main power tube and the auxiliary power tube and the power supply capacitor; The second linear voltage stabilizing circuit is connected with the first linear voltage stabilizing circuit in parallel; The adjusting circuit is connected with the second linear voltage stabilizing circuit, and when the second linear voltage stabilizing circuit is turned on, the first charging current flowing through the second linear voltage stabilizing circuit is adjusted so that the voltage change rate of a first node between the main power tube and the inductor reaches a preset change rate; and when the PWM signal generated by the control chip of the switching power supply is effective, the second linear voltage stabilizing circuit is turned on, and the power supply capacitor is charged. Optionally, when the supply voltage reaches a first threshold, the first linear voltage stabilizing circuit is turned off. Optionally, when the second linear voltage stabilizing circuit is turned on, the adjusting circuit adjusts the first charging current to a reference current, so that a