Switching Regulator Dead Time Adjusting Circuit
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Solution Overview
Problem
Existing switching regulators face challenges in suppressing hard switching and short-circuit currents without increasing circuit complexity or being limited to the start-up period, with previous solutions either causing power loss, having limited application periods, or requiring high-voltage circuit elements.
Innovation Solution
A switching regulator with a series-connected first and second switch, a resonant oscillation circuit, and an auxiliary winding to detect voltage changes, using a differentiation detecting circuit and dead time adjusting circuit to determine current transfer timing and adjust dead time, thereby preventing hard switching and short-circuit currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead time is extended to prevent short-circuit current, then reliability improves, but productivity deteriorates due to reduced switching frequency
Solution Approach 1:
The dead time is made dynamic rather than fixed. The control device extends dead time only when body diode current transfer is detected, and maintains normal dead time otherwise. This dynamic adjustment prevents short-circuit currents while minimizing impact on switching frequency and maintaining productivity.
Solution Approach 2:
The dead time parameter is changed based on detected operating conditions. When current transfer between body diodes is detected, the dead time parameter is extended; when no current transfer is detected, the normal dead time parameter is used. This parameter change resolves the contradiction by adapting dead time to actual circuit conditions.
2Measurement precision
If circuit complexity is increased to detect current transfer timing, then measurement precision improves, but device complexity worsens
Solution Approach 1:
The control device uses feedback from voltage detection across the resonant oscillation capacitor to determine current transfer timing. The detection circuit monitors voltage changes, and this feedback information is used by the control device to adjust dead time timing, achieving precise measurement without complex additional circuitry.
Solution Approach 2:
The voltage across the resonant oscillation capacitor serves as an intermediary indicator of current transfer timing. Instead of directly detecting complex current waveforms, the system uses the voltage intermediary that changes in correlation with current transfer, simplifying the detection mechanism while maintaining measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses hard switching and short-circuit currents without increasing circuit scale and maintains performance beyond the start-up period, ensuring stable operation by accurately detecting voltage reversals and adjusting dead time for safe current transfer.
Implementation Method 1
a series-connected resonant oscillation circuit composed of a resonant oscillation capacitor Cr and a leakage inductance Lk of a primary winding P1 of a transformer T1
Implementation Method 2
an auxiliary winding P2 provided in the primary side of the transformer T1. The voltage detected by the auxiliary winding P2 is delivered to a differentiation detecting circuit 5 and differentiated therein
Implementation Method 3
the current I_Qb that has been flowing in the switch Qb turns to flow through the body diode Da of the high side switch Qa. Since the voltage Vs between the switch Qa and the switch Qb is approximately the voltage Vi of the DC power supply Ed during a current is flowing in the body diode Da, even if the switch Qa is turned ON, the voltage across the switch Qa does not change rapidly. Thus zero voltage switching (ZVS) is achieved.
Data Source
AI summary
A switching regulator related to aspects of the invention can include an auxiliary winding for monitoring the voltage across the primary winding of a transformer, a differentiation detecting circuit that detects the timing of reversal start or reversal end of the signal detected by the auxiliary winding and a dead time adjusting circuit that receives a signal to trigger turn OFF of a first switch or a second switch and, after passing a predetermined delay time from the detection of the signal, generates a signal to trigger turn ON of the first switch or the second switch. The differentiation detecting circuit can confirm current transfer between body diodes. The dead time adjusting circuit can adjust a dead time to deliver the signal after a predetermined time from the confirmation of the current transfer. In some aspects of the invention, occurrence of hard switching and short-circuit current can be suppressed.