A control method for a switch circuit, a control circuit and a switch circuit device

Abstract

The invention discloses a control method of a switch circuit, a control circuit and a corresponding switch circuit device, which relate to the field of circuit technology and are used to ensure that the switch circuit works in DCM, and only after the DCM enters a certain depth, the frequency spreading is started, so as to avoid switching Spread spectrum begins when the circuit works in CCM. The control circuit includes: an acquisition module, used to acquire the first time; a comparison module connected with the acquisition module, used to compare the size of the first fixed time with the first time; an adjustment module connected with the comparison module, when the first time is less than During the first fixed time, the adjustment module adjusts the period of the conduction signal of the first switch tube to the second fixed time; when the first time is greater than the first fixed time, the adjustment module adjusts the sum of the second time and the first fixed time Adjust to the second fixed time to achieve spread spectrum. The control circuit of the switch circuit provided by the present invention is used to control the switch circuit to spread spectrum.

Description

technical field [0001] The invention relates to the field of circuit technology, in particular to a control method for a switch circuit, a control circuit and a switch circuit device. Background technique [0002] Currently, a switch circuit (for example, a BUCK circuit) is a circuit commonly used in circuit design, such as figure 1 As shown, the BUCK circuit usually includes a first switch tube 1', a second switch tube 2' and an inductor 3', wherein the first switch tube 1' can be a MOS tube (Metal Oxide Semiconductor Field Effect Transistor, metal-oxide- semiconductor field effect transistor), the second switch tube 2' can be a freewheeling diode or a synchronous rectifier tube, Vin' is the input signal of the BUCK circuit, Vout' is the output signal of the BUCK circuit, and TON' is the first switch The conduction signal of tube 1'. [0003] Specifically, when the load of the switching circuit is large, the switching circuit is in CCM (Continuous Conduction Mode, continu...

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Problems solved by technology

[0004] However, the inventors of the present application have found that after the switch circuit enters DCM from CCM, as the load decreases, the load current will decrease, and the conduction time of the first switch tube 1' will be shortened. It can be seen from the working process that the period of the conduction signal TON' of the first switch tube 1' when the switch circuit is in DCM is the same as the period of the conduction signal TON' of the first switch tube 1' when the switch circuit is in CCM, namely In the above two working modes of the switching circuit, the switching cycle of the first switching tube 1' remains unchanged. Therefore, when the timing circuit is set to realize the fixed frequency of the switching circuit, when the first switching tube 1' is turned on After the time is shortened to the minimum conduction time allowed by the first switch tube 1', since the duty cycle of the conduction signal TON' of the first switch tube 1' is the conduction time of the first switch tube 1' divided by the first The switching period of the switching tube 1', so that the duty cycle of the conduction signal TON' of the first switching tube 1' cannot continue to decrease, so that the load current of the switching circuit cannot continue to decrease as the load decreases

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