Flyback constant-voltage and constant-current switching power supply
A technology of constant voltage, constant current, and switching power supply, which is applied in the direction of electrical components, adjusting electrical variables, and converting DC power input to DC power output. , to achieve the effect of improving the conversion efficiency of the circuit
Pending Publication Date: 2020-07-31
SHENZHEN LII SEMICON CO LTD
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Problems solved by technology
In the prior art, there are great limitations in achieving constant current output by controlling the on-time duty cycle of the secondary coil, which requires the peak current of the primary coil to be a constant value. At this time, if the circuit output feedback voltage continues to decrease, it will As a result, the conduction time of the secondary diode D1 increases, and the dead time also increases; if the input voltage of the circuit increases, the conduction time of the primary coil becomes shorter, and the dead time increases accordingly.
The increase of the dead time will not only lead to a longer circuit switching cycle, a decrease in the switching frequency, and even enter the audio frequency range, but also reduce the conversion efficiency of the circuit
Method used
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[0027] The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.
[0028] See figure 1 , figure 1 It is a schematic diagram of a flyback constant voltage constant current switching power supply in the prior art, which includes a constant current constant voltage control circuit. The constant current and constant voltage control circuit includes a power supply circuit (POWER), a sampling control circuit, a peak current control circuit (CS), a second comparator (CMP), an AND gate circuit, a D flip-flop (DRFF), a driving circuit (DRV ), a switch tube Q6, a constant current control circuit, a current detection resistor RCS, and a transformer, wherein the transformer includes a primary coil, a secondary coil and an auxiliary coil, the primar...
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The invention relates to a flyback constant-voltage and constant-current switching power supply, which comprises a constant-voltage and constant-current control circuit. The constant-voltage constant-current control circuit comprises a constant-current control circuit, a sampling circuit, an error amplification circuit and a peak current control circuit. The sampling circuit is used for sampling an induced voltage signal of the auxiliary coil to the secondary coil; the induced voltage signal is sent to the error amplifying circuit to be amplified; the peak current is processed by the peak current control circuit to obtain a maximum conduction current control signal VCST_MAX; and the constant current control circuit accesses and processes the maximum conduction current control signal VCST_MAX so as to control the flyback constant-voltage constant-current switching power supply to output constant current, the constant current output by the constant current control circuit is ensured to be constant through an active control mode, and the flexibility and the reliability are high.
Description
technical field [0001] The invention relates to a flyback type constant voltage and constant current switching power supply, which belongs to the technical field of flyback type power supply control. Background technique [0002] At present, there are various types of flyback AC / DC switching power supplies, and their internal control modules are becoming more and more complex, but all control modules are designed to obtain accurate constant voltage (CV) and constant current (CC) outputs. Such as figure 1 As shown, the stable output voltage is maintained by controlling the switching frequency and peak current of the switching tube Q6. For precise constant current output, the usual method is to adjust the duty cycle of the secondary coil conduction time while fixing the peak current. In the prior art, there are great limitations in achieving constant current output by controlling the on-time duty cycle of the secondary coil, which requires the peak current of the primary coil...
Claims
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IPC IPC(8): H02M3/335H02M7/217
CPCH02M3/33523H02M3/33569H02M7/217
Inventor 张杰朱敏郑凌波
Owner SHENZHEN LII SEMICON CO LTD