A kind of enabling and starting circuit used in high-voltage dc-dc circuit

Abstract

The invention discloses an enabling starting circuit used for a high voltage DC-DC circuit. According to the enabling starting circuit, a threshold voltage of a first NMOS serves as a first threshold, when a voltage of an EN pin of an enabling comparator is lower than the threshold voltage of the first NMOS, a whole system is stopped, and therefore the turn-off current of the system is zero; when the voltage of the EN pin is higher than the threshold voltage of the first NMOS, a loop is started, the loop can provide starting power for a band-gap reference circuit, the band-gap reference circuit can provide an accurate reference voltage for the enabling comparator after being started, and therefore the enabling comparator can monitor the voltage of the EN pin; when the voltage of the EN pin is larger than the threshold voltage, a whole subsequent DC-DC system is started, and the function of enabling an enabling threshold to be accurate is achieved; meanwhile, as the loop can control the voltage applied to the grid of the first NMOS, a bias current of the first NMOS can be controlled, a working current of the enabling starting circuit can be further controlled to be constant, and the working current cannot be changed along with changes of the input voltage of the EN pin.

Description

technical field [0001] The invention relates to an enabling and starting circuit used in a high-voltage DC-DC circuit, which is used in a high-voltage DC-DC converter integrated circuit to realize zero shutdown current, precise enabling threshold and constant operating current, and The working current does not vary with the input voltage (VIN) and the enable terminal (EN) voltage. Background technique [0002] In the existing high-voltage DC-DC converter integrated circuits, the maximum gate-source voltage Vgs of the high-voltage MOSFET can only withstand 5V, and the maximum drain-source voltage Vds can withstand 5V to 40V (or higher). of high pressure. Since there is no external 5V input voltage, the enable and start-up circuits used to achieve precise enable thresholds usually need to consume a certain amount of quiescent current in the off state, such as the ADP2301. When EN=0, the reference voltage and enable The comparator is working. Or in order to achieve zero shutd...

AI Technical Summary

Problems solved by technology

Since there is no external 5V input voltage, the enable and start-up circuits used to achieve precise enable thresholds usually need to consume a certain amount of quiescent current in the off state, such as the ADP2301. When EN=0, the reference voltage and enable The comparator is working. Or in order to achieve zero shutdown current, the precise enable threshold cannot be achieved, such as LM2734, which only uses the threshold voltage of the MOSFET (which cannot be precise) to achieve shutdown

Another method is to use a high-voltage JFET (such as MP1484) to generate a 5V voltage inside the chip, which can achieve zero off-current and accurate enablement, but requires the use of a high-voltage JFET, which will increase the production process steps and increase production. cost

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